HK40008804A

HK40008804A - Stationary intraoral tomosynthesis imaging systems, methods, and computer readable media for three dimensional dental imaging

Info

Publication number: HK40008804A
Application number: HK19132027.4A
Authority: HK
Inventors: J‧陆; O‧Z‧周; A‧塔克; J‧尚; B‧冈萨雷斯
Original assignee: Xinvivo, Inc.; The University Of North Carolina At Chapel Hill
Priority date: 2016-05-09
Filing date: 2017-02-01
Publication date: 2020-06-19

Description

Static intraoral tomosynthesis imaging systems, methods, and computer readable media for three-dimensional dental imaging

Cross Reference to Related Applications

This patent application claims priority to U.S. provisional application serial No.62/333,614, filed 2016, 5, 9, the contents of which are incorporated herein by reference in their entirety.

Technical Field

The subject matter disclosed herein relates to x-ray radiography. More particularly, the subject matter disclosed herein relates to static intraoral tomosynthesis systems, methods, and computer readable media for three-dimensional dental imaging.

Background

Dental radiography has undergone significant changes over the past decades. However, the need for more accurate diagnostic imaging methods remains a high priority. Intraoral dental x-rays were introduced only one year after Roentgen found x-ray radiation. Since then, advances in dental imaging technology have included more sensitive detector technology, panoramic imaging, digital imaging, and cone-beam computed tomography (CBCT). Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Ultrasound (US) and optical techniques have also been investigated for dental imaging.

Intraoral radiography is the primary approach to dental imaging. Which provides higher resolution and limited field of view images for most routine dental needs. However, as a two-dimensional (2D) imaging modality, this technique suffers from the superposition of overlapping structures and the loss of spatial information in the depth dimension. Panoramic imaging (a popular form of extraoral imaging) visualizes the entire maxilla, mandible, temporomandibular joint (TMJ) and associated structures in a single image, but suffers from considerable geometric distortion and has lower spatial resolution than intraoral radiography. CBCT as a three-dimensional (3D) imaging modality has found wide acceptance in the dental field, particularly for surgical planning procedures such as dental implant planning and orthodontic treatment planning, and for the assessment of endodontic and pathological conditions. However, there are some CBCT related drawbacks compared to 2D radiography, which are excessive noise and artifacts from metallic dental restorations/appliances, which reduce image quality; greatly increased acquisition, reconstruction and interpretation times relative to 2D radiography, thereby reducing clinical efficiency and increasing financial costs; and significantly higher ionizing radiation doses, which increase the radiation burden on the patient.

Despite many technological advances, the accuracy of radiographic diagnosis of some of the most common dental conditions has not improved for many years, and in some cases is still low. Examples include caries detection, root fracture detection, and periodontal bone loss assessment.

Dental caries is the most common dental disease. The world health organization estimates that 60% to 90% of school-age children and almost all adults have dental caries at some point in time. If caries lesions are detected early enough (e.g., prior to cavitation), they can be inhibited and remineralized by non-surgical means. When caries lesions are undetected, they can develop into more serious conditions that can require extensive repair, endodontic treatment, and (in some cases) extraction. Over the past decades, caries detection sensitivity has not seen any significant improvement. 2D intraoral radiography is the current gold standard, reportedly with sensitivity in the range of 40% to 70% for dentinal lesions and 30% to 40% for enamel lesions. CBCT provides no significant improvement in caries detection. Beam hardening artifacts and patient movement reduce structural sharpness and clarity.

Detection of root fissure (VRF) represents a clinically significant diagnostic task in dental management with serious consequences. VRF is considered one of the most adverse dental conditions associated with endodontic therapy. The overall detection of VRFs is still poor. The ability of CBCT to detect initial small root fractures is limited by its lower resolution. In addition, excessive beam hardening, streak artifacts, and noise lead to significantly reduced sensitivity and significantly increased false positive root break diagnosis.

Dental radiography provides important information for estimating tooth prognosis and for making treatment decisions associated with periodontal disease. Currently, 2D intraoral radiography is the primary approach to dental imaging. Which provides higher resolution images and a limited field of view for most routine dental needs. However, this technique is limited due to the 2D representation of the 3D object. The 2D image results in an overlap of overlapping structures and a loss of spatial information in the depth dimension. Thus, the important dimensional relationship is blurred, the sharpness of the observation is reduced, the object of interest is lost, and the contrast of the lesion is reduced. Panoramic imaging, on the other hand, a popular form of extraoral imaging, visualizes the entire maxillary, mandibular, temporomandibular joint (TMJ) and associated structures in a single scan. It suffers from considerable geometric distortion and has a lower spatial resolution compared to intra-oral radiography.

These diagnostic tasks illustrate the clinical need for a diagnostic imaging system with high resolution, 3D capability, reduced metal artifact sensitivity and lower radiation burden on the patient.

Digital tomosynthesis imaging is a 3D imaging technique that provides reconstructed slice images from a finite angular series of projection images. Digital tomosynthesis improves the visibility of anatomical structures by reducing visual clutter from overlapping normal anatomical structures. Some examples of current clinical tomosynthesis applications include breast imaging, abdominal imaging, musculoskeletal imaging, and breast imaging.

A variation of tomosynthesis technology, known as aperture-tuned computer tomography (TACT), was studied for dental imaging in the late 90 s of the 20 th century. TACT significantly improves the diagnostic accuracy of most tasks compared to traditional radiography. These improvements include root fracture detection, detection and quantification of periodontal bone damage, implant site assessment, and estimation of impacted third molars. However, the results of dental caries are not conclusive.

TACT is not clinically applicable because this technique is not practical for patient imaging. Conventional x-ray tubes are single pixel devices in which x-rays are emitted from a fixed point (focal spot). To acquire a plurality of projection images, the x-ray source is mechanically moved around the patient. The fiduciary markers are used to determine the imaging geometry. This method is time consuming (e.g., about 30 minutes per scan) and requires high operator skill to achieve image acquisition. The difficulty in accurately determining the imaging geometry and the long imaging acquisition time due to the mechanical motion of the source make TACT impractical. Any variation of TACT for 3D intraoral imaging using a single x-ray source has similar drawbacks and disadvantages.

Extraoral synthesis has been studied in patient studies by using experimental devices and by using CBCT. The extraoral geometry requires a high radiation dose. The image quality is limited by the crosstalk of the defocused structure. To avoid high radiation doses, intra-oral tomosynthesis using a single mechanically scanned x-ray source has been described in the patent literature, and studies using a single conventional x-ray source and a rotating model have been conducted in recent publications. Unfortunately, the constraints described above for TACT remain the same as for these approaches, which are mainly caused by the conventional single focus x-ray tube.

Accordingly, there is a need for a static intraoral tomosynthesis system, method and computer readable medium for 3D dental imaging that can quickly obtain 3D dental images with the same spatial resolution as conventional 2D intraoral dental imaging with a significant radiation dose to the patient.

Disclosure of Invention

The presently disclosed subject matter relates to generating three-dimensional (3D) tomosynthesis images of an object, in particular images of a patient's teeth, from one or more two-dimensional (2D) x-ray projection images.

According to one aspect of the subject matter herein, there is provided a static intra-oral tomosynthesis system for three-dimensional (3D) imaging of an object, the system comprising: a spatially distributed x-ray source array comprising one or more focal spots; a degree of freedom (DOF) device attached to the spatially distributed x-ray source array at a first end of an articulated arm, the first end of the articulated arm being positioned closest to the object; a control unit comprising a power supply and control electronics configured to control the spatially distributed x-ray source array, wherein the control unit is attachable to the second end of the articulated arm, wherein the control unit is connected to the spatially distributed x-ray source array via a cable through the interior of the articulated arm or along the articulated arm, and wherein the control unit is mountable to a wall or surface; an intra-oral detector configured to record one or more x-ray projection images, wherein each of the one or more x-ray projection images is generated by x-ray radiation emitted from a corresponding focal spot of the one or more focal spots of the spatially distributed x-ray source array; and a collimator disposed between the spatially distributed x-ray source array and the patient, wherein the collimator couples the spatially distributed x-ray source array to the x-ray detector, the collimator configured to confine x-ray radiation emitted from one or more focal spots of the spatially distributed x-ray source array to a common area bounded by an intra-oral detector, also known as an x-ray detector. The static intraoral tomosynthesis system is configured to perform tomosynthesis reconstruction using the computing platform to generate one or more 3D images using the one or more x-ray projection images.

According to another aspect of the subject matter herein, there is provided a method for three-dimensional (3D) imaging with a static intra-oral tomosynthesis system, the method comprising: positioning a spatially distributed x-ray source array of a static intraoral tomosynthesis system outside an oral cavity of a patient, wherein the spatially distributed x-ray source array comprises one or more focal spots spatially distributed over one or more anodes; positioning an x-ray detector inside an oral cavity of a patient with an x-ray detector holder configured for at least one imaging protocol, wherein the x-ray detector holder comprises a plurality of magnets disposed on a first end of the x-ray detector holder, the first end being outside the oral cavity of the patient; providing a first collimator plate on a first end of a collimator and a second collimator plate on a second end of the collimator, wherein the second collimator plate is selected to correspond to one or more aspects of an x-ray detector holder for at least one imaging protocol; coupling the spatially distributed x-ray source array and the collimator to the x-ray detector holder via a second collimator plate by coupling the second collimator plate to a second end of the collimator and to a first end of the x-ray detector holder; acquiring one or more x-ray projection images of the patient's oral cavity from one or more viewing angles by sequentially activating each of one or more focal spots of a preset radiation dose and x-ray energy, wherein the one or more x-ray projection images are two-dimensional (2D); transmitting the one or more x-ray projection images to a computing platform; reconstructing one or more 3D tomosynthesis images from the one or more x-ray projection images using one or more iterative reconstruction algorithms; and processing the one or more 3D tomosynthesis images and displaying the one or more 3D tomosynthesis images on one or more monitors, the one or more monitors electrically connected to the computing platform.

According to yet another aspect of the subject matter herein, there is provided a non-transitory computer-readable medium comprising computer-executable instructions that, when executed by a processor of a computer, control the computer to perform a method comprising: positioning a spatially distributed x-ray source array of a static intraoral tomosynthesis system on a first side of a subject or outside an oral cavity of a patient, the spatially distributed x-ray source array comprising one or more focal spots; positioning an x-ray detector inside a second side of the object or an oral cavity of the patient with an x-ray detector holder configured for at least one imaging protocol, the x-ray detector holder comprising a plurality of magnets disposed on a first end of the x-ray detector holder, the first end being located outside the first side of the object or the oral cavity of the patient; providing a first collimator plate on a first end of a collimator and a second collimator plate on a second end of the collimator, the second collimator plate selected to correspond to one or more aspects of an x-ray detector holder for at least one imaging protocol; coupling the spatially distributed x-ray source array and the collimator to the x-ray detector holder via a second collimator plate by coupling the second collimator plate to a second end of the collimator and to a first end of the x-ray detector holder; acquiring one or more x-ray projection images of the oral cavity of the subject or patient from one or more viewing angles by sequentially activating each of one or more focal spots of a preset radiation dose and x-ray energy, the one or more x-ray projection images being two-dimensional (2D); transmitting the one or more x-ray projection images to a computing platform; reconstructing one or more 3D tomosynthesis images from the one or more x-ray projection images using one or more iterative reconstruction algorithms; and processing the one or more 3D tomosynthesis images and displaying the one or more 3D tomosynthesis images on one or more monitors, the one or more monitors electrically connected to the computing platform.

While some aspects of the subject matter disclosed herein have been set forth above and are achieved, in whole or in part, by the presently disclosed subject matter, other aspects will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, as best described below.

Drawings

The features and advantages of the subject matter of the invention will be more readily understood from the following detailed description, which is to be read in connection with the accompanying drawings, which are given by way of illustrative and non-limiting example only, and in which:

FIG. 1 is a perspective view illustrating one example embodiment of an intraoral tomosynthesis system having a fixed link between an x-ray source and an x-ray detector in accordance with the disclosure herein;

FIG. 2A is a top view illustrating a fixed link between the x-ray source and the x-ray detector of FIG. 1, in accordance with the disclosure herein;

FIG. 2B is a top perspective view illustrating a socket between an x-ray source and an x-ray detector in accordance with the disclosure herein;

FIG. 3A is a front perspective view illustrating one example embodiment of a geometric calibration apparatus for an intraoral tomosynthesis system in accordance with the disclosure herein;

FIG. 3B is a rear perspective view illustrating an example embodiment of the geometric calibration device of FIG. 3A, in accordance with the disclosure herein;

FIG. 4 is an example image capture illustrating a process for determining tomosynthesis imaging geometry using the example geometry calibration apparatus of FIGS. 3A-3B in accordance with the disclosure herein;

fig. 5A-5D are schematic diagrams illustrating an example geometric calibration apparatus for an intraoral tomosynthesis system according to the disclosure herein;

6A-6C are schematic diagrams illustrating example light patterns using the geometric calibration device of FIGS. 5A-5D, in accordance with the disclosure herein;

FIG. 7 is a schematic diagram illustrating one example embodiment of a geometric calibration apparatus for an intraoral tomosynthesis system in accordance with the disclosure herein;

FIG. 8 is a system diagram illustrating one example embodiment of a static intraoral tomosynthesis system for three-dimensional (3D) dental imaging interacting with an example computing platform according to the disclosure herein;

FIG. 9 is a perspective view showing one example embodiment of a static intraoral tomosynthesis system for 3D dental imaging having an articulated arm with a degree of freedom device at one end and electronics and power supply at the other end in accordance with the disclosure herein;

FIG. 10 is a perspective view illustrating one embodiment of an example holder for an x-ray sensor and/or detector in accordance with the disclosure herein;

11A and 11B are detailed perspective views illustrating one example embodiment of a magnetic coupling of the detector holder to collimator of FIG. 10, in accordance with the disclosure herein;

FIG. 12 is a perspective view illustrating one example embodiment of a collimator having a first x-ray limiting collimator plate and a second x-ray limiting collimator plate according to the disclosure herein;

FIG. 13 is a perspective view illustrating the first x-ray limiting collimator panel of FIG. 12 according to the disclosure herein;

FIG. 14 is a schematic diagram of an example collimator that collimates an x-ray beam of each focal spot onto a detector area in accordance with the disclosure herein;

FIG. 15 is a perspective view of one example embodiment of a degree of freedom device having three rotational degrees of freedom in accordance with the disclosure herein;

FIG. 16 is a perspective view illustrating one example embodiment of a linear x-ray source array according to the disclosure herein;

fig. 17A is a schematic illustration of the relative orientation of a linear x-ray source array with respect to one example embodiment of an x-ray sensor and/or detector such that the scan direction is generally perpendicular to the root-crown direction, in accordance with the disclosure herein;

fig. 17B is a schematic illustration of the relative orientation of a linear x-ray source array with respect to one example embodiment of an x-ray sensor and/or detector such that the scan direction is generally parallel to the root-crown direction, in accordance with the disclosure herein; and

figure 18 is a schematic diagram utilizing a flow chart according to an example embodiment of a static intraoral tomosynthesis method for 3D dental imaging utilizing a static intraoral tomosynthesis system according to the disclosure herein, the static intraoral tomosynthesis method including formation and display of a synthetic two-dimensional (2D) intraoral image.

Detailed Description

The presently disclosed subject matter relates to static intraoral tomosynthesis systems, methods, and computer readable media for three-dimensional (3D) dental imaging applications, but those skilled in the art will appreciate that the static intraoral tomosynthesis systems, methods, and computer readable media may be used in applications other than dental imaging. For example, the system described herein may be modified in the manner of a static digital breast tomosynthesis (s-DBT) system, such as disclosed in U.S. patent No.7,751,528, which is incorporated herein by reference in its entirety. It is noted that the static design of the s-DBT system increases the system spatial resolution by eliminating image blur caused by x-ray tube motion. By integrating with a high frame rate detector, faster scan times are also achieved to minimize patient motion and discomfort under pressure. The static design of the s-DBT (without constraints on mechanical motion) also allows for wider angle tomosynthesis scans for better depth resolution without changing scan time.

In some aspects, the static intraoral tomosynthesis systems, methods, and computer-readable media described herein are used in dental imaging applications. In particular, static intraoral tomosynthesis systems may be used for intraoral imaging applications using x-ray detectors placed inside the oral cavity of a patient. In other aspects, the static tomosynthesis system may be used for extraoral imaging applications with an x-ray detector placed outside the patient's oral cavity.

In some aspects, static intraoral tomosynthesis systems, methods, and computer readable media may be used for dual energy applications. For example, two complete sets of x-ray projection images may be collected for each object being imaged. The first group may be collected at a first x-ray energy and the second group may be collected at a second x-ray energy, wherein the first x-ray energy is different from the second x-ray energy. According to one such aspect, x-ray images of the two groups are collected at two different x-ray anode voltages and then processed, reconstructed, and subtracted to enhance the contrast of certain features, such as, for example, caries. According to another such aspect, at various viewing angles, two projection images may be acquired, one at a first x-ray energy and the other at a second x-ray energy.

Thus, the presently disclosed subject matter provides static intraoral tomosynthesis systems, methods, and computer-readable media for 3D dental imaging. According to some embodiments, a static intraoral tomosynthesis system, method, and computer-readable medium for 3D dental imaging may include an x-ray source, an x-ray detector (for positioning inside an oral cavity of a patient), a geometric calibration apparatus, and control electronics for obtaining multiple projection views of a region of interest (ROI) (e.g., a tooth) of an object within the oral cavity of the patient without moving the x-ray source, x-ray detector, or ROI. Fig. 1 shows one such embodiment of an intraoral tomosynthesis system, generally designated 100. The system 100 may include an x-ray source, generally designated 110, an x-ray detector 120, a control unit, generally designated 130, a collimator, generally designated 140, and an x-ray detector holder 150. In some aspects, the system 100 may be installed such that it is not mobile. For example, the system 100 may be installed from a ceiling, wall, or the like. In other aspects, the system 100 may be mobile. For example, the system 100 may include wheels that may be placed on a movable cart, a stand, and the like. Fig. 1 shows a movable cart, generally designated 102, to which system 100 is attached 102 with a robotic arm, generally designated 104. The robotic arm 104 may be rotationally and/or axially movable about a pivot or articulated joint to adjust the position of the system 100 about the object to be imaged. Thus, by utilizing the movable cart 102 and robotic arm 104, the system 100 may be freely moved and rotated for optimal positioning relative to the object. Optionally, the movable cart 102 may include a rechargeable battery (not shown) that may provide imaging power, thereby reducing the need for wires and/or wires to power the system 100.

The x-ray source 110 may be configured to direct an x-ray beam (e.g., 108, fig. 2A) toward a location or position where an ROI of the object (e.g., a tooth of a patient) is placed. The x-ray beam may be directed toward the location or position from a number of different angles. Additionally, the x-ray source 110, the x-ray detector 120, and the object may be positioned such that the generated x-ray beam is detected by the x-ray detector 120. In some aspects, the x-ray source 110 can include a spatially distributed x-ray source array (e.g., 310, fig. 3A) positioned such that the generated x-ray beam is generally directed toward the object and can pass through an ROI of the object. In some aspects, the ROI of an object may change because different ROIs of the same object may be imaged during one or more imaging sessions.

In some aspects, the x-ray source array of x-ray sources 110 can include a plurality of individually programmable x-ray pixels (e.g., 312, fig. 3A) distributed as a linear array. Alternatively, the x-ray pixels can be non-linearly distributed along the x-ray source 110 in a two-dimensional matrix, e.g., as arcs, circular perimeters, polygons, and the like. In some aspects, the x-ray pixels in the array may be uniformly spaced and/or angled for directing the x-ray beam toward an ROI of the subject. Regardless, the x-ray pixels may be arranged in any suitable location such that the x-ray beam is generally directed toward the object and the x-ray beam is detected by x-ray detector 120. It is noted that the x-ray source 110 and the x-ray detector 120 may be stationary relative to each other during irradiation of the object by the x-ray source 110 and detection by the x-ray detector 120. The x-ray source 110 can control (e.g., via the control unit 130) the sequential activation (e.g., one pixel at a time) with respect to a predetermined dwell time and a predetermined x-ray dose level.

In some aspects, the x-ray source array of sources 110 can, for example, include between 10 and 100 pixels, e.g., specifically 25 pixels. Each pixel may include, for example, a Carbon Nanotube (CNT) field emission-based cathode, such as those commercially available from manufacturers (including, for example, XinRay systems corporation), a gate electrode to extract electrons, and a set of electron focusing lenses (e.g., EinZel type electrostatic focusing lenses) to focus the field emission electrons to a small area or focal point on a target (e.g., an anode). Note that the CNT cathode is a cold cathode that can be turned on and off instantaneously. In this way, the use of a CNT cathode may reduce the heating time and heat generation of the source 110 compared to conventional vacuum electrons based on thermionic cathodes (e.g., cathode ray tubes, microwave tubes, x-ray tubes, etc.). Alternatively, each pixel may include a thermionic cathode, a photocathode, or the like.

In some aspects, where the x-ray source pixels are arranged linearly parallel to the detector plane (non-arc), the pixel-to-source distance may vary from pixel to pixel. To compensate for this variation in x-ray beam travel distance, the x-ray tube current for each pixel can be individually controlled and adjusted (e.g., by control unit 130) so that the flux intensity at the dashed line surface remains the same.

The size of the focal spot and/or the x-ray flux generated by each pixel of the x-ray source array of x-ray source 110 may be adjusted by control unit 130. The size of the focal spot may be in the range between 0.05mm and 2 mm. The system 100 can design an isotropic 0.2 x 0.2mm effective focal spot size for each x-ray source pixel. The individual focal spot size can be adjusted by adjusting the potential (e.g., voltage) of the focusing electrode. To minimize current fluctuations and delays and also to reduce pixel-to-pixel variations, an electrical compensation loop may be incorporated to automatically adjust the gate voltage to maintain a constant preset emission current. The area of the CNT cathode can be selected such that a peak x-ray tube current of about 10mA can be obtained with an effective focal spot size of 0.2 x 0.2 mm. Note that a higher x-ray peak current of 50mA to 100mA can be obtained by increasing the CNT area and the focal spot size.

In some aspects, the x-ray detector 120 may be configured for intraoral or extraoral detection of the projection images. For example, the x-ray detector 120 may include an intraoral x-ray detector configured to be positioned behind a patient's teeth in the interior of the patient's mouth. The x-ray detector 120 may include a fast frame rate, on the order of 1 to 100 frames per second (e.g., hertz). The x-ray detector 120 may also include a high spatial resolution, with pixel sizes in the range of 10 x 10 microns to 200 x 200 microns, to detect projection images of an object (e.g., teeth within a patient's mouth).

The x-ray detector 120 may be configured to collect projection images of the object from different angles for tomosynthesis. To this end, the control unit 130, which may be stored in a housing 132 of the system 100, may be configured to sequentially activate an x-ray source array of electron emission pixels (as described herein) spatially distributed over an area of the x-ray source 110 (e.g., on one or more anodes of a vacuum chamber) with a predetermined exposure time, radiation dose, and x-ray energy and may be configured to regulate the intensity of the x-ray flux at each focal spot. The x-ray source 110 may be electrically connected with the x-ray detector 120 such that projection images are recorded from radiation originating from each focal spot. It is noted that the control unit 130 may vary the intensity of the x-ray radiation based on the distance between the x-ray source array of the x-ray source 110 and the object by reading the radiation directly from each focal spot, reading the x-ray tube current or reading the cathode current. In this way, the x-ray dose delivered to the subject from each viewing angle is substantially the same.

In some aspects, the size of the various focal spots and/or the x-ray flux generated by the x-ray source 110 may be adjusted by the control unit 130. For example, by increasing the carbon nanotube area and the focal spot size, control unit 130 may adjust x-ray source 110 (which operates with up to 100kVp and up to 10mA to 20mA tube current for each focal spot, and focal spot size in the range of 0.1mm to 1.5 mm) to a higher x-ray peak current of 50mA to 100 mA. In some aspects, the control unit 130 may also adjust the individual focus size by adjusting the potential of the focusing electrodes. In some aspects, the control unit 130 may minimize current fluctuations and may reduce pixel-to-pixel variations by incorporating an electrical compensation loop to adjust the gate voltage to maintain a constant preset emission current.

A collimator 140 may be placed between the window of the x-ray source 110 and the detector 120 to confine the x-ray radiation to the ROI of the object. In some aspects, a first end of the collimator 140 may be fixed to the x-ray source 110 while a second end of the collimator 140 may be collapsible and/or may taper in the direction of the detector 120.

In some embodiments, a mechanical fixture (e.g., x-ray detector holder 150) may connectively attach the x-ray source 110 to the x-ray detector 120 in a known fixed position. Thus, the position of the x-ray source 110 relative to the x-ray detector 120 may be known and maintained at all times. Alternatively, the position of the x-ray focal spot relative to the x-ray detector 120 need not be determined by a physical connection between the x-ray detector 120 and the x-ray source 110. Instead, a geometric calibration device may be used to determine the position of the x-ray source 110 relative to the x-ray detector 120, and thereby detect the position of the x-ray focal spot relative to the x-ray detector 120.

Referring now to FIG. 2A, a more detailed view of the system 100 is shown. In particular, the relationship between the x-ray source 110, the x-ray detector 120, and the x-ray detector holder 150 is shown in more detail. As shown in fig. 2A, the x-ray detector holder 150 secures the x-ray sources 110 to the x-ray detector 120 at a known distance relative to each other. In some aspects, a first end of the x-ray detector holder 150 is fixed to the x-ray source 110 and a second end of the x-ray detector holder 150 is fixed to the x-ray detector 120. In some aspects, the x-ray source array of sources 110 includes a plurality of pixels, each pixel positioned at a known location and disposed to be directed inward toward the object at a known angle. Thus, when the x-ray source 110 and the x-ray detector 120 are disposed at a fixed distance from each other, the precise location of the focal spot generated by the x-ray source array pixels relative to the x-ray detector 120 is known.

For example, in fig. 2A, x-ray source 110 and x-ray detector 120 are securely separated by x-ray detector holder 150 by a distance D. In this example, x-ray source 110 includes a linear x-ray source array and x-ray source detector 120 is configured as an intra-oral detector for placement in the mouth of a patient to image the patient's teeth (generally designated 106). The x-ray detector 120 may be positioned behind a particular ROI of the tooth 106. Thus, when x-ray source 110 is activated, an x-ray beam (generally designated 108) may be generated to project through an ROI of tooth 106 and onto x-ray detector 120. Because the distance D is a fixed known quantity, the exact location of the focal spot generated by the x-ray source array pixels relative to the x-ray detector 120 is known. In this way, the reconstruction of the 2D projection images into 3D images may be improved.

Referring to fig. 2B, an alternative to utilizing an x-ray detector holder 150 is shown. In particular, an apparatus, generally designated 200, may be used to connect an x-ray source (e.g., 110) to an x-ray detector (e.g., 120) at a known distance relative to each other. In some aspects, the apparatus 200 may include a socket 210, the socket 210 attachable to an x-ray source and connectable to a connection arm 220 attachable to an x-ray detector. Where the apparatus 200 is used in an intraoral tomosynthesis system (e.g., 100), the receptacle 210 may be attached to an x-ray source (e.g., 110) and may magnetically connect to a connecting arm 220, the connecting arm 220 being attachable to an intraoral x-ray detector (e.g., 120) positioned within the patient's mouth.

In some aspects, the socket 210 may comprise any suitable material, such as any metal or metallic material (e.g., aluminum (Al), steel, iron (Fe), alloys thereof, and so forth), any non-metallic material (e.g., plastic, polymer, and so forth), a non-magnetic material, a magnetic material, and/or any combination thereof. The socket 210 may comprise a metal socket configured for attachment to an x-ray source. The receptacle 210 may include a hollow interior, generally designated 212, to allow collimation of x-ray radiation from the x-ray source array. To attach to the connection arm 220, the socket 210 may include an angled channel (generally designated 214) disposed along an exterior side surface. The channel 214 may be disposed along the entire length of the receptacle 210 and may be correspondingly sized and shaped to receive the raised inner surface 228 of the longitudinal portion 222 of the connection arm 220.

In some aspects, the connecting arm 220 can comprise any suitable material, such as any metal or metallic material (e.g., aluminum (Al), steel, iron (Fe), alloys thereof, and the like), any non-metallic material (e.g., plastic, polymer, and the like), a non-magnetic material, a magnetic material, and/or any combination thereof. For example, the connecting arm 220 may include a magnetic longitudinal portion 222, an elbow 224, and an x-ray detector holder 226. A first end of the bend 224 may be disposed toward one end of the longitudinal portion 222 and may extend perpendicularly therefrom, forming a right angle therewith. An x-ray detector holder 226 may be disposed at a second end of the elbow 224 and may be configured to securely hold an x-ray detector (e.g., 120). Where the x-ray detector is an intraoral x-ray detector, the x-ray detector holder 226 may be configured to securely position the intraoral x-ray detector within the patient's intraoral cavity.

The longitudinal portion 222 of the connection arm 220 may include a convex inner surface 228, and the convex inner surface 228 may be sized and shaped to be removably received in the channel 214 of the receptacle 210. In some aspects, the connecting arm 220 may be configured to move into and out of attachment with the socket 210 via a magnetic attachment. For example, the magnetic attachment may include a metal contact (generally designated 216) provided along the length of one or both of the channel 214 and the raised inner surface 228 of the longitudinal portion 222. The metal contacts 216 may be configured to provide immediate feedback on the accuracy of the alignment and connection between the channel 214 and the inner surface 228. Furthermore, such contacts 216 may allow for a quick release function of the device 220, which may be useful, for example, in the event of sudden movement of the patient.

Referring now to fig. 3A-3B, a first example embodiment of a geometric calibration apparatus, generally designated 300, for use in an intra-oral tomosynthesis system including an x-ray source 310 and an x-ray detector 320 is shown. Geometric calibration device 300 may include, for example, a board or screen 330, at least one light source 340, a camera 350, and at least one gyroscope 360 or any other device for being configured to calculate and/or detect orientation and rotation.

In some aspects, the position of the x-ray detector 320 relative to the x-ray source 310 may be fixed, even in embodiments in which the x-ray source 310 and the x-ray detector 320 are not physically connected to each other. For example, fig. 3A and 3B illustrate that the x-ray source 310 and the x-ray detector 320 are not physically separated by a mechanical link, such as the x-ray detector holder 150 of fig. 1-2B, which may otherwise maintain a fixed position of the x-ray source to the x-ray detector. Instead, the x-ray source 310 and the x-ray detector 320 may be physically separated from each other such that the relative position of the x-ray detector 320 with respect to the x-ray source 310 may be dynamically determined by geometric calibration techniques, as described in more detail below.

In some aspects, the x-ray source 310 can include an x-ray source array (generally designated 312) that can include individually programmable x-ray pixels 314. As shown in the example embodiment of fig. 3A, the 5 to 20 pixels 314 may be distributed as a generally linear array and may be configured to project x-rays onto the x-ray detector 320, thereby generating a projection image of an ROI (e.g., a patient's teeth) of the object. However, because the x-ray source 310 and the x-ray detector 320 are not physically connected to each other, the geometric calibration apparatus 300 may be used to geometrically calibrate the position of the x-ray detector 320 relative to the x-ray source 310.

In some aspects, at least one light source 340 can project a beam of light (generally indicated at 342) onto plate 330 to produce a spot of light (generally indicated at 344) to determine the translational position of plate 330 relative to x-ray source 310. In some aspects, the x-ray detector 320 may be physically connected to the plate 330. For example, cross-bar 322 may be used to secure x-ray detector 320 to plate 330. The crossbar 322 may comprise a substantial length of between 2cm and 20cm, for example. In some aspects, the length of the crossbar 322 may be adjustable. Plate 330 may comprise paper, plastic, metal, or any combination of such materials having dimensions of approximately, for example, 5cm and 20 cm. In some aspects, crossbar 322 may secure plate 330 to x-ray detector 320 such that plate 330 is in a plane parallel to the plane in which x-ray detector 320 is located. In other aspects, the plate 330 may be angled with respect to the x-ray detector 320.

In some aspects, where the detector 320 is configured as an intra-oral x-ray detector, the plate 330 may protrude from the patient's mouth. Thus, by determination of the angular and translational position of plate 330 relative to x-ray source 310, the position of x-ray detector 320 relative to x-ray source 310 can be determined because plate 330 can be connected to x-ray detector 320 at a known fixed distance.

In some aspects, at least one light source 340 may be projected onto the plate 330. For example, the at least one light source 340 may include a low power laser or other light configured to be projected onto the plate 330, such as a 5mW laser pointer having a wavelength of 650 nm. The at least one light source 340 may be mounted or otherwise attached to the x-ray source 310 and/or collimator. As shown in fig. 3A-3B, the illustrated embodiment has four light sources 340, each positioned at a separate corner of the x-ray source 310. Each of the four light sources 340 may be angled toward the plate 330 to project a light beam 342 onto the plate 330 and thereby produce four independent spots 344 (see, e.g., 334A-D, fig. 4). Depending on the angle of incidence of each of the four light sources 340 directed at the plate 330, the spot 344 may form a rectangle, square, triangle, or any other shape, with each projected beam 342 that produces the spot 344 forming a corner vertex of such a projected shape. In some aspects, the angle of incidence at which each light source 340 is mounted to the x-ray source 310 can be known and can be used to determine the translational position of the plate 330 relative to the x-ray source 310. It is noted that positioning the at least one light source 340 in this manner can result in the shape formed by the spot 344 produced by the projected beam 342 on the plate 330 becoming smaller as the plate 330 moves farther from the x-ray source 310 and larger as it moves closer to the x-ray source 310.

In some aspects, camera 350 can record the position of projected spot 344 on plate 330 to determine the translational position of plate 330 relative to x-ray source 310. In some aspects, the camera 350 may also be configured to provide motion tracking and correction during imaging processes in which there is unintentional movement of the object or system. The camera 350 may comprise a high resolution, high speed digital camera that may be mounted in a known location, for example, on the x-ray source 310 or a collimator (not shown). As shown in fig. 3A-3B, the camera 350 may be mounted centrally on the top surface of the x-ray source 310 and adjacent to the front surface edge of the x-ray source 310. In some aspects, the camera 350 may transmit the captured photographic image to a computing platform (see, e.g., 804, fig. 8). For example, camera 350 may transmit a photographic image capturing the position of light spot 344 on plate 330 to a computing platform to determine the translational position of plate 330 relative to x-ray source 310, and thus the position of x-ray detector 320 relative to x-ray source 310.

In some aspects, at least one gyroscope 360 may be included to determine the angular position of the plate 330 relative to the x-ray source 310. For example, at least one gyroscope 360 may include a parallelsx gyroscope module 3 axis L3G4200D, which may be commercially available from manufacturers including, for example, parallelax corporation. Thus, determining the angular position of the plate 330 relative to the x-ray source 310 can be accomplished in one of a number of techniques. For example, a first technique may include mounting a first gyroscope 360 at the x-ray source 310 and a second gyroscope (not shown) at the board 330 and comparing data points from each gyroscope at the computing platform. In another example, the second technique may include resetting the plate 330 by positioning the plate 330 in the same plane as the x-ray source array 310, resetting data of a first gyroscope 360 mounted at the x-ray source 310, and measuring deviations from the initial x-ray source plane during the imaging process.

Referring now to FIG. 4, an exemplary image capture from a camera (e.g., 350) shows a captured image from beam 342, beam 342 being projected onto plate 330 and producing spots (generally labeled 344A-D). In this example, four individual spots 344A-D are generated from the beam 342, the beam 342 is generated from four individual light sources 340, the four individual light sources 340 are arranged in a similar manner as described above with reference to FIGS. 3A-3B, wherein each spot 344A-D forms one corner or vertex of a rectangular shape. A coordinate system may be defined to establish x, y, and z directions for determining x-ray detector 320 relativeIn the translated position of the x-ray source 310. In some aspects, the distance between the various spots may determine the z-offset of the plate 330 relative to the x-ray source 310. For example, the horizontal or x-distance B measured between the first spot 344A and the second spot 344B_xOr the vertical or y-distance B measured between the second spot 344B and the third spot 344C_yThe z-offset of the plate 330, and thus the x-ray detector 320, relative to the x-ray source 310 can be determined because the distance between the spots 344A-D is uniquely determined by the provision of any diffraction grating attached to the at least one light source 340, the wavelength of the at least one light source 340, and the z-offset. In other aspects, the ratio of the distance from the spot to the edge of the plate 330 to the distance between the opposing edges of the plate 330 can determine the x-offset or y-offset of the plate 330 relative to the x-ray source 310. For example, the horizontal or x distance a from spot 344D to the edge of plate 330_xHorizontal or x distance c between two opposing edges of plate pair 330_xA (e.g., a)_x/c_x) The x-offset of plate 330, and thus x-ray detector 320, with respect to x-ray source 310 may be determined. In another illustrative example, the vertical or y-distance a from spot 344D to the edge of plate 330_yThe vertical or y-distance c between two opposing edges of the plate pair 330_yA (e.g., a)_y/c_y) The y-offset of plate 330, and thus x-ray detector 320, with respect to x-ray source 310 may be determined.

Referring now to fig. 5A-5D, a second example embodiment of an exemplary geometric calibration apparatus (generally designated 500) for use in an intra-oral tomosynthesis system including an x-ray source 510 and an x-ray detector 520 is shown. Here, an example sequential acquisition of tomographic images using the geometric calibration apparatus 500 is shown. With fig. 5A showing an initial setup of the geometric calibration apparatus 500, fig. 5B-5D show sequential activation of different cathodes in an array of x-ray sources at two different positions (e.g., a first position shown in fig. 5B-5C and a second position shown in fig. 5D). It is noted that the apparatus 500 may include, for example, a board or screen 530, a light source 540, and a camera 550.

Referring to fig. 5A, the apparatus 500 may be configured in an initial configuration prior to acquisition of the 2D projection images. Although the position of x-ray detector 520 relative to x-ray source 510 may be fixed, x-ray source 510 and x-ray detector 520 are not shown physically connected to each other in this embodiment. Thus, the mechanical links are not connected and maintain a fixed spacing between the x-ray source 510 and the x-ray detector 520. Rather, the x-ray source 510 and the x-ray detector 520 are physically separated from each other such that the relative position of the x-ray detector 520 with respect to the x-ray source 510 can be dynamically determined by geometric calibration techniques, as described in more detail below. In some aspects, x-ray source 510 may include an x-ray source array (generally designated 512) that may include individually programmable x-ray pixels 516. As shown in fig. 5A-5D, the nine pixels 516 may be distributed as a linear array and may be configured to be activated individually to sequentially project an x-ray beam (generally designated 514) (see, e.g., fig. 5B-5D) onto the x-ray detector 520 to generate projection images of an ROI (e.g., a patient's teeth) of the object 502. However, because the x-ray source 510 and the x-ray detector 520 are not physically connected to each other, the geometric calibration apparatus 500 may be used to geometrically calibrate the position of the x-ray detector 520 relative to the x-ray source 510.

In some aspects, the x-ray detector 520 may be physically connected to the plate 530. For example, a cross-bar 522 may be used to secure the x-ray detector 520 to the plate 530. The cross-bar 522 may include a length, for example, approximately between 2cm and 20 cm. In some aspects, the length of the crossbar 522 may be adjustable. Plate 530 may comprise, for example, paper, plastic, metal, or any combination thereof. In some aspects, the crossbar 522 may secure the plate 530 to the x-ray detector 520 such that the plate 530 lies in a plane parallel to a plane in which the x-ray detector 520 lies. In other aspects, the plate 530 may be angled with respect to the x-ray detector 520.

In some aspects, where detector 520 is configured as an intra-oral x-ray detector, plate 530 may protrude from the patient's mouth. Thus, by determination of the angular and translational position of plate 530 with respect to x-ray source 510, the position of x-ray detector 520 with respect to x-ray source 510 may be determined because plate 530 may be connected to x-ray detector 520 at a known and fixed distance (e.g., with cross-bar 522). The plate 530 may be made of paper, plastic, metal, or any combination of such materials, with dimensions approximately between 5cm and 20cm, for example.

The light source 540 may be configured to project a beam of light (generally designated 542) onto the plate 530 and produce a spot of light (generally designated 544) to determine the translational position of the plate 530 relative to the x-ray source 510. In some aspects, only one light source 540 may be required, as compared to the first embodiment of the geometric calibration apparatus 300. The light source 540 may be mounted or otherwise attached to the x-ray source 510 and/or collimator (not shown). In some aspects, the light source 540 is integral with the camera 550, which may each be configured to attach to the source 510. As shown in fig. 5A-5D, the light source 540 may be mounted with the camera 550 and centrally mounted on the x-ray source 510 and adjacent to the front surface edge thereof. It is noted that light source 540 may comprise a low power laser or other light configured to be projected onto plate 530, such as a 5mW laser pointer having a wavelength of 650 nm.

In some aspects, at least one diffraction grating (not shown) having a known diffraction line distance can be attached to x-ray source 510 at a known relative position. For example, a one-dimensional (1D) diffraction grating may be utilized. In another example, two gratings may be used, where the first grating is a 1D diffraction grating and the second grating is a 2D diffraction grating. In some aspects, the gratings may each include a diffraction line distance that may be similar to or different from each other. The diffraction line distance may comprise the distance between individual diffraction lines in the grid. In other aspects, the gratings may comprise the same optical dimensions and may be oriented in different directions relative to each other. Where geometric calibration apparatus 500 includes at least one diffraction grating, light source 540 may be mounted such that light beam 542 passes through the diffraction grating at a known location relative to x-ray source 510, wherein passing through the grating causes light source 540 to separate in the vertical (y) and horizontal (x) directions according to the following separation formula:where m is 0,1,2,3 to indicate the magnitude of the diffraction points, λ is the wavelength of the light source 540D is the distance of the plate 530 from the diffraction origin, and D is the diffraction grating slit spacing.

In some aspects, camera 550 can record the position of projected spot 544 on plate 530 to determine the translational position of plate 530 with respect to x-ray source 510. In some aspects, the camera 550 may also be configured to provide motion tracking and correction during imaging processes in which there is unintentional movement of the object 502 or the system (e.g., system 100). The camera 550 may comprise a high resolution, high speed digital camera that may be mounted in a known location, for example, on the x-ray source 510 or collimator. As discussed above, the camera 550 and the light source 540 may be mounted centrally on the x-ray source 510 and adjacent to the front surface edge of the x-ray source 510. In some aspects, the camera 550 may transmit the captured photographic image to a computing platform (see, e.g., 804, fig. 8). For example, camera 550 may transmit a photographic image capturing the position of light spot 544 on plate 530 to a computing platform to determine the translational position of plate 530 relative to x-ray source 510, and thus the position of x-ray detector 520 relative to x-ray source 510.

Thus, the light source 540 and camera 550 may be angled toward the plate 530 to project the light beam 542 through the at least one diffraction grating and onto the plate 530, and thereby produce the light spot 544 (see, e.g., 544A-C, fig. 6A-6C) at different locations of the screen 530, and thus provide a light pattern on the screen 530. It is noted that different positions of light source 540 and/or screen 530 can result in different light patterns that can each be captured by camera 50 and can be used to calibrate the geometry of screen 530 and attached x-ray detector 520 relative to various pixels in x-ray source 510.

Once apparatus 500 is configured and ready for generation of 2D projection images, camera 550 may be configured to capture an initial light pattern produced by light source 540 (e.g., a laser) when x-ray detector 520 and screen 530 are in a first position and the captured pattern is transmitted to a computing platform (e.g., 804) for processing and geometric calibration. For example, when x-ray detector 520 and screen 530 are in an initial (or first) position, camera 550 may be configured to capture spots 544, spots 544 forming an initial light pattern on screen 530. This processing of the captured image may be used as a reference for geometric calibration purposes.

Referring now to fig. 5B-5D, the acquisition of 2D projection images is shown, wherein individual pixels 516 in the source array 512 of the x-ray source 510 are sequentially activated when the x-ray detector 520 and the screen 530 are in a first position and then in a second position. Although fig. 5B-5D show sequential acquisitions of only three pixels 516 and only two different locations, those skilled in the art will recognize that these illustrations are merely illustrative and non-limiting. For example, individual pixels 516 in the x-ray source 510 may be activated and the detector 520 configured to record the resulting image. As shown in fig. 5A-5D, where there are nine pixels 516, all nine pixels 516 may be activated individually and the x-ray detector 520 may be configured to record respective images of respective positions of the x-ray detector 520 relative to the activated pixels 516. In some aspects, the x-ray detector 520 need only be in one position, in which case the nine pixels 516 need only be activated at once, with activation of each pixel 516 being performed separately. However, if the x-ray detector 520 is moved to multiple locations, each of the nine pixels 516 are separately reactivated when the x-ray detector 520 is moved to each of the subsequent multiple locations.

In fig. 5B, a second pixel 516A in x-ray source 510 is shown in an activated state to generate x-ray beam 514, x-ray beam 514 is projected onto detector 520, and detector 520 records the projected image when screen 530 and x-ray detector 520 are in the first position. Note that a first one of the pixels 516 in the x-ray source 510 may have been activated and the x-ray detector 520 may have recorded its generated image before the second pixel 516A in the x-ray source 510 is activated. Likewise, in FIG. 5C, a third pixel 516A in x-ray source 510 is activated to generate x-ray beam 514, x-ray beam 514 is projected onto detector 520, and detector 520 records the projected image while screen 530 and x-ray detector 520 are in the first position. Because the screen 530 remains in the first position during activation of the second pixel 516A and the third pixel 516B in the source array 512, the light pattern produced by the spot 544 will remain the same for geometric calibration purposes.

However, in fig. 5D, the screen 530 and the x-ray detector 520 are moved to a second position, which is different from the first position (indicated by the dotted line). For the example shown in fig. 5D, screen 530 and x-ray detector 520 are moved toward the left in the x-direction relative to x-ray source 510. Although the screen 530 and the x-ray detector 520 are movable, the x-ray source remains in its initial position. In such a case, when light beam 542 is projected onto screen 530, the light pattern formed by light spot 544 will have a different geometry because light spot 544 is projected onto screen 530 at a different location than when screen 530 is in the first position. This remains true for any subsequent positions into which the screen 530 and x-ray detector 520 move, where each subsequent position is also different from the first position and each other position.

Thus, once the screen 530 and the x-ray detector 520 are moved to the second position or any other position different from the first position, the camera 550 may be configured to capture the second light pattern generated by the light source 540 (e.g., a laser) when the x-ray detector 520 and the screen 530 are in any position different from the first position and transmit the captured second light pattern to the computer platform (e.g., 804, fig. 8) for processing and geometric calibration. For example, when x-ray detector 520 and screen 530 are in a second position, camera 550 may be configured to capture an image containing spots 544, spots 544 forming a second light pattern on screen 530. This processing of the captured image may be used as a reference for geometric calibration purposes. In some aspects, and still referring to fig. 5D, a fourth pixel 516C in the source array 512 can be activated to generate an x-ray beam 514, the x-ray beam 514 projected onto a detector 520, the detector 520 recording the projected image when the screen 530 and the x-ray detector 520 are in the second position. When the x-ray detector 520 and the screen 530 are in the second position, activation of each successive pixel 516 in the source array 512 at the second position may also occur to generate other successive images.

In some aspects, once the individual pixels 516 in the source array 512 have been activated and the projection images have been recorded by the x-ray detector 520, 3D image reconstruction may be initiated. For example, the 3D image reconstruction may include tomosynthesis reconstruction. The 3D image reconstruction may be implemented using a computer program and/or workstation (e.g., 804, fig. 8)) to analyze, calibrate, reconstruct, display, etc., the 3D tomographic image from the recorded 2D projection images. Geometric calibration data (e.g., photographic images) captured and recorded by the camera 550 may be utilized by a computer program and/or workstation to determine the relative position of individual pixels 516 of the source array 512 with respect to the x-ray detector 520; this position data is then used for tomosynthesis reconstruction of a 3D image of the tooth.

Referring now to fig. 6A-6C, various figures show an example captured image from beam 542, beam 542 being projected onto plate 530 and producing spot 544. Each of fig. 6A-6C illustrate different positions and/or orientations of the screen 530 relative to the light source (e.g., 540). It is noted that moving the screen 530 relative to the light source may cause the light pattern produced by the spots 544 on the screen 530 to change. Thus, by comparing and analyzing the pattern of spots 544, the relative movement of x-ray source 510 with respect to detector 520 can be determined.

Fig. 6A shows a first schematic diagram (generally designated 600A) of a first light pattern (generally designated 544A) produced at a first position and a first orientation of the screen 530 relative to the light source. In fig. 6A, the spots of a first light pattern 544A form a first light pattern that indicates that screen 530 is positioned at a "short z-distance" relative to a light source mounted on an x-ray source (e.g., 510) and in a plane parallel to the plane containing the light source. Here, the "short" and "long z-distance" definitions are defined relative to fig. 6B because screen 530 is positioned at a smaller z-distance from the x-ray source (as compared to when it is positioned at the long z-distance). Thus, the closer the screen 530 is positioned in the z-direction to the light source, the closer the spots of the first light pattern 544A will be spaced.

Fig. 6B shows a second schematic view (generally designated 600B) of a second light pattern (generally designated 544B) produced at a second position of the screen 530 relative to the light source, but still at the first orientation. In fig. 6B, the spots of the second light pattern 544B form a second light pattern that indicates that the screen 530 is positioned at a "long z-distance" relative to the light source mounted on the x-ray source and in a plane parallel to the plane containing the light source. Thus, the further away the screen 530 is positioned in the z-direction from the light source, the more dispersed the spots of the second light pattern 544B will be.

FIG. 6C illustrates a third schematic view (generally designated 600C) of a third light pattern (generally designated 544C) produced at a third position and second orientation of screen 530 relative to the light source. In fig. 6C, the spots of a third light pattern 544C form a third light pattern that indicates that screen 530 is positioned at a z-distance of about 10cm to 40cm relative to a light source mounted on an x-ray source and in a plane of rotation relative to the plane containing the light source. In the case where the screen 530 is rotated with respect to a plane containing the light source, the relative distance between the individual light points of the third light pattern 544C may be different than when the screen 530 is oriented parallel to the plane containing the light source. In such cases, the rotation calculation may be used during calibration to determine the angular position of the x-ray detector (e.g., 520) connected to the plane 530 relative to the x-ray source. Thus, the more the screen 530 is rotated relative to the plane containing the light sources, the greater the relative distance between the individual spots of the third light pattern 544C will increase. Conversely, the less the screen 530 is rotated relative to the plane containing the light sources, the less the relative distance between the individual spots of the third light pattern 544C will increase.

Referring now to FIG. 7, a third embodiment of an example embodiment of a geometric calibration apparatus 700 for use in an intra-oral tomosynthesis system (e.g., system 100) is schematically illustrated. The geometric calibration device 700 may include, for example, a light source 710, a camera 720, a screen or plate 730, a first grating 740, and a second grating 750.

Light source 710 may include a visible laser or any other light source (not shown in this embodiment) attached to an array of x-ray sources. The light source 710 may provide light at any suitable known frequency and wavelength. In some aspects, only one light source 710 may be required, as compared to the first embodiment of the geometric calibration apparatus 300. In some aspects, a camera 720 is mounted relative to the light source 710 and attached to the x-ray source array. For example, the camera 720 may be mounted above or below the light source 710, or in any suitable position relative to the light source 710, as will be understood by those skilled in the art.

In some aspects, light source 710 may be projected onto screen or panel 730 through at least one optical diffraction grating. Two optical diffraction gratings 740 and 750 are included in the geometric calibration apparatus 700. A screen or panel 730 may be attached to the x-ray detector (not shown in this embodiment) and positioned in front of the ROI of the object to be imaged. For example, screen 730 may be attached to an intra-oral x-ray detector and may be positioned outside of the patient's mouth. The plate 730 may be attached to the x-ray detector at known relative positions using, for example, a cross-bar (e.g., 322,522, fig. 3A-3B, and 5A-5D, respectively). The plate 730 may comprise paper, plastic, metal, or any combination of such materials thereof, wherein the dimensions of the plate 730 are approximately 5cm and 20 cm.

In some aspects, the plate 730 may include a predetermined calibration marker 732 that is centered or otherwise disposed. The predetermined calibration marker 732 may comprise a square or other closed shape encompassing an area therein. The light source 710 may be configured to project a split beam (generally designated 752) onto the plate 730, particularly within the shape formed by the predetermined calibration marker 732. The predetermined calibration marker 732 may be used as a reference point with respect to the spots M0, M1, M2, etc. to determine the position of the x-ray detector to which the plate 730 is attached with respect to the x-ray source, as will be discussed in more detail below. In some aspects, the plate 730 includes a calibration circle 734 defined within a predetermined calibration marker 732. The position of calibration circle 734 may be predetermined by an operator to correspond to a desired position of light source 710. Thus, the operator may adjust the position of the light source 710 such that the light beam 702 generated by the light source 710 produces the initial spot M0 within the calibration circle 734.

In some aspects, the at least one diffraction grating may be attached to the x-ray source at a known location. As shown in fig. 7, two diffraction gratings 740 and 750 are positioned in front of the light source 710 so that a light beam emitted from the light source 710 may be projected through the gratings 740 and 750, and the gratings 740 and 750 may split the light beam. The split beam may then be projected onto the plate 730 in the form of a plurality of spots M1, M2. Note that the initial spot M0 of the light beam is also projected onto the panel 730.

In some aspects, gratings 740 and 750 may be 1D or 2D optical diffraction gratings with a known diffraction line distance therebetween. According to the example embodiment of fig. 7, the first grating 740 is a 1D diffraction grating and the second grating 750 is also a 1D diffraction grating. In some aspects, gratings 740 and 750 may each include a diffraction line distance that may be similar to or different from each other. The diffraction line distance may comprise the distance between individual diffraction lines in the grid. For example, first diffraction grating 740 and/or second diffraction grating 750 may be configured with diffraction line distances that may include diffraction lines that are spaced apart, e.g., approximately, e.g., 0.001mm to 0.1 mm. In other aspects, gratings 740 and 750 may comprise the same focal dimension and may be oriented in different directions relative to each other. In fig. 7, for example, first diffraction grating 740 and second diffraction grating 750 are rotationally oriented with respect to each other. According to this example embodiment of the geometric calibration apparatus 700, the first grating 740 is rotated 90 degrees with respect to the orientation of the second grating 750.

The gratings 740 and 750 may be configured to split the initial grating 702 emitted by the light source 710 to generate a plurality of spots M1, M2 on the panel 730. The initial grating 702 may be a beam of light that includes a wavelength in the visible range (e.g., about 390nm to 700 nm). Primary spot M0 may be generated by beam 702 and may be used as a reference for positioning light source 710, and thus the x-ray source, within calibration circle 734.

The light beam 702 may also be configured to pass through one or more diffraction gratings. Because geometric calibration apparatus 700 has at least one diffraction grating (first diffraction grating 740 and second diffraction grating 750), light source 710 may be mounted such that light beam 702 passes through diffraction gratings 740 and 750 at a known location relative to the x-ray source, where passing through gratings 740 and 750 causes light source 710 to separate in the vertical (y) and horizontal (x) directions according to the following separation formula:where m is 0,1,2,3., indicating the magnitude of the diffraction points, λ is the wavelength of the light source 540, D is the distance of the plate 530 from the diffraction origin, and D is the diffraction grating slit spacing. As shown in fig. 7, for example, the light beam 702 passes through a first diffraction grating 740 and a second diffraction grating 750, each grating rotated 90 degrees relative to each other. The first diffraction grating 740 is configured with a first diffraction line pitch comprising horizontal lines spaced apart, for example, about 0.001mm to 0.1 mm; and the second diffraction grating 750 is configured with a second diffraction pitch comprising vertical lines spaced apart, for example, by about 0.001mm to 0.1 mm. It will be appreciated that other line spacings, vertical and horizontal, are within the skill of those in the art. The beam 702 is thus split horizontally by the first diffraction grating 740 into multiple horizontal beams 742, with intermediate beams passing through the second diffraction grating 750, which results in the intermediate beams of the horizontal beams 742 being split into separate vertical beams 752. In some aspects, the split horizontal and vertical beams 742 and 752 can be projected onto the plate 730 within an area bounded by the predetermined calibration marker 732. According to the example embodiment of fig. 7, eight individual beams (four of which are horizontal beams 742 and four of which are vertical beams 752) are projected onto the plate 730 and form a 2D light pattern 736 comprising eight individual spots M1, M2. In this example embodiment, four spots M1 and four spots M2 are formed, with the initial spot M0 positioned within the center of the light pattern 736 formed from spots M1, M2. However, diffraction points of multiple orders of magnitude (such as M0, M1, M2) may be used to determine the position of the light source 710 relative to the plate 730, and thus the position of the x-ray source relative to the x-ray detector.

In some aspects, the camera 720 may be configured to capture at least one projection image of the points of light M1, M2, and the initial point of light M0 within the predetermined calibration marker 732 and transmit the at least one captured image to a computing platform (see, e.g., 804, fig. 8). For example, camera 720 may transmit photographic images capturing the positions of initial spot M0 and spots M1, M2 within calibration marker 732 on plate 730 to a computing platform for determining the translational position of plate 730 with respect to the x-ray source, and thus the x-ray detector relative to the x-ray sourceAt the location of the x-ray source. Thus, with the light pattern 736 having the initial spot M0 and spots M1, M2, the calibration marker 732 and the diffraction angle θ for each intensity peak are predetermined_mThe location when the beam 702 hits the first grating 740 and the distance between the various spots M1, M2 on the plate 730 may be determined at the computing platform. For example, the geometric calibration module may calculate the position when the beam 702 hits the first grating 740 and the distance between the respective spots M1, M2 on the plate 730, as well as the axial rotation angle of the three plates 703. It is noted that all six degrees of freedom of the plate 730 can be determined from the light pattern 736 formed by the points of light M1, M2 relative to the point where the first beam is split (e.g., where the beam 702 hits the first grating 740). Thus, the complete geometry of the imaging system can be determined based on the relative positions of the x-ray detector to the plate 730 and the x-ray source with respect to the light source 710.

Thus, regardless of the technique used for geometric calibration purposes, the angular and/or translational position of the x-ray detector relative to the x-ray source may be determined, which may facilitate accurate reconstruction of tomosynthesis images from the acquired x-ray projection images. Thus, the determined position (e.g., angular position and/or translational position) of the x-ray source during image acquisition may allow a tomosynthesis reconstructed image of the imaging subject to be formed.

Referring now to FIG. 8, a system diagram (generally designated 800) of an example embodiment of a static intraoral tomosynthesis system 802 interacting with an example computing platform 804 is shown. It is noted that when configured as described herein, the example computing platform 804 becomes a dedicated computing platform that can improve the technical field of static intra-oral tomosynthesis imaging for 3D dental imaging by acquiring 2D projection images from multiple viewpoints and then processing such images without moving the x-ray source or the patient.

In some aspects, exemplary tomosynthesis system 802 comprises a tomosynthesis system, such as described above in fig. 1 (e.g., 100), fig. 9, and/or fig. 17. In some aspects, tomosynthesis system 802 may include a geometric calibration device 810, such as those described above (e.g., 300,500, 700). The tomosynthesis system 802 may be configured to interact with a computing platform 804 for calibrating the geometry of the system 802 through processing of the photographic images. For example, tomosynthesis system 802 may be configured to transmit one or more projection images from the intraoral detector to computing platform 804 via an interface, such as, for example, a data transmission line connecting the intraoral detector with the computing platform, a wireless transmission, or the like. The computing platform 804 may also be configured for tomosynthesis reconstruction of 2D projection images.

Computing platform 804 may be configured to perform one or more aspects associated with the geometry of calibration system 802. In some aspects, the computing platform 804 may be one or more separate entities, devices, or software executing on a processor. In some aspects, computing platform 804 may be a single node or may be distributed across multiple computing platforms or nodes. Computing platform 804 may also be adapted for purposes other than geometric calibration.

In some aspects, computing platform 804 may include a geometric calibration module 806, the geometric calibration module 806 configured to perform one or more aspects associated with calibrating the geometry of tomosynthesis system 802 and aspects other than geometric calibration, such as tomosynthesis reconstruction. In some aspects, the computing platform 804 may further include a stand-alone tomosynthesis reconstruction module (not shown) configured to reconstruct the acquired 2D x radiographic projection images. Note that the geometric calibration module 806 may be configured to perform tomosynthesis reconstruction as well as geometric calibration. Geometric calibration module 806 may be any suitable entity (e.g., software executing on a processor) for performing one or more aspects associated with geometric calibration of tomosynthesis system 802. The geometric calibration module 806 may include functionality for receiving at least one photographic image from a camera (e.g., 350,550,750) during one or more image acquisition sessions. For example, an interface 808 associated with the geometric calibration module 806 and/or the computing platform 804 may receive photographic images of various locations of light patterns, light spots, etc. on a screen, plate, etc. from the geometric calibration device 810 for each adjustment of the position of the x-ray detector to which the screen, plate, etc. is attached relative to the ROI of the object. In this example, a geometric calibration module user (e.g., a device or computing platform usable by a user or operator) may capture at least one photographic image of a light pattern, light spot, etc., on a screen, plate, etc., for each adjustment of the position of the x-ray detector relative to the ROI of the object, which may then be received by the geometric calibration module 806.

The tomosynthesis reconstruction module (independent of or integral with the geometric calibration module) may be configured to acquire and/or process 2D x ray projection images of the object. For example, the tomosynthesis reconstruction module may be configured to reconstruct the acquired 2D x radiographic projection images of the object via various algorithms including, for example, filtered backprojection and iterative reconstruction methods (e.g., iterative truncation artifact reduction).

Computing platform 804 and/or geometric calibration module 806 may include functionality for storing one or more projection images for later use. In some aspects, computing platform 804 and/or geometric calibration module 806 may include functionality for instantiating or initializing images and/or for providing images to other computing platforms or devices. For example, the computing platform 804 and/or the geometric calibration module 806 may receive one or more photographic images, may calibrate the geometry of the system 802 based on these images, and/or may provide these images to other nodes via the interface 808 for geometric calibration of the tomosynthesis system 802.

In some aspects, the computing platform 804 and/or the geometric calibration module 806 may include or access a data store 812, the data store 812 including data and/or photographic images related to geometric calibration of the tomosynthesis system 802. For example, computing platform 804 and/or geometric calibration module 806 may access data store 812, data store 812 including previous images, mapped coordinate systems, image data, configuration files, settings, or configurations. Example embodiments of data store 812 may include non-transitory computer-readable media, such as flash memory, random access memory, non-volatile media, and/or other storage devices. In some aspects, data store 812 may be external to and/or integrated with computing platform 804 and/or geometric calibration module 806.

In some embodiments, computing platform 804 and/or geometric calibration module 806 may include one or more communication interfaces for interacting with a user and/or a node. For example, computing platform 804 and/or geometric calibration module 806 may provide a communication interface for communicating with a user of computing platform 804 and/or geometric calibration module 806. In some aspects, a user of computing platform 804 and/or geometric calibration module 806 may be an automated system, or may be controlled by or controllable by a human user. A user of computing platform 804 and/or geometric calibration module 806 may use a camera of device 810 to capture one or more photographic images and transmit these images to computing platform 804 and/or geometric calibration module 806. According to the example embodiment of fig. 8, the computing platform 804 is shown electrically connected to one or more monitors 814, the one or more monitors 814 being configured to display at least a portion of the reconstructed 3D tomosynthesis image and/or at least a portion of the one or more 2D projection images. The one or more monitors 814 may be of any suitable type (e.g., CRT, LCD, OLED, holographic, projection, etc.) and may be configured in any suitable configuration and number.

In some embodiments, computing platform 804 may include functionality for configuring tomosynthesis system 802 (as described herein) for capturing 2D x ray projection images of an ROI of an object. For example, computing platform 804 may control the acquisition of 2D x ray projection images using tomosynthesis system 802 by activating an x-ray source to begin the generation of an x-ray beam. In another aspect, computing platform 804 may include functionality to modify conditions within tomosynthesis system 802, including, for example, moving a translation stage, moving an x-ray detector relative to an object, and so forth. In some aspects, computing platform 804 may include functionality to generate content (e.g., a reconstructed 3D tomosynthesis image utilizing previously acquired 2D x radiographic projection images) and/or to retrieve stored content associated with an imaging session.

According to another example embodiment of a static intraoral tomosynthesis system (generally designated 900), tomosynthesis system 900 shown in fig. 9 includes an x-ray source 930, an intraoral x-ray detector (generally designated 912), an x-ray detector holder 910, an articulated arm 950 (having a degree of freedom device 940 at one end thereof and a control unit 960 at another end thereof), and an x-ray collimator 920 (having one end thereof connected to x-ray source 930 and another end thereof magnetically coupled to x-ray detector holder 910). It is contemplated that x-ray collimator 920 may be coupled to x-ray detector holder 910 by any suitable fastener.

In some aspects, the tomosynthesis system 900 may be mounted such that it is immovable. For example, the tomosynthesis system 900 may be installed from a ceiling, wall, or the like. In other aspects, the tomosynthesis system 900 may be mobile. For example, the tomosynthesis system 900 may include wheels that may be placed on a movable cart, a hand truck, a stand, and the like. Additionally, control unit 960 may include power supplies, control electronics, cables, and the like, at least partially contained within control unit 960. In some aspects, a power source (not shown) may be enclosed inside the articulated arm 950, rather than inside the control unit 960. In some aspects, the power source may include a rechargeable battery (not shown) that may provide power to the imaging, thereby avoiding the need for wires and/or wires for power during use. According to some embodiments, the articulated arm 950 may be attached at one end to the control unit 960 and may be attached at the other end to the x-ray source 930 and/or the detection component (e.g., x-ray detector 912). In some aspects, cables may run along the articulated arm 950 from the control unit 960 to the x-ray source 930 and/or detection components (e.g., x-ray detector 912) so that these components may be used for 3D dental imaging. In other aspects, the cables may be internal to the articulated arm. In other aspects, the cables may be provided independently of the articulated arm or in another manner than described above. A degree of freedom (DOF) device 940 may be provided between the articulated arm 950 and the x-ray source 930 to orient the x-ray source 930 and/or the x-ray detector 912 in three degrees of freedom around an object to be imaged.

The articulated arm 950 may include an extension arm 952, a first arm segment 954, and a second arm segment 956. According to the embodiment shown in fig. 9, extension arm 952 is attached to control unit 960 at a first end via a pivot and/or another type of attachment that allows extension arm 952 to move generally in a first plane. For example, extension arm 952 in fig. 9 may be pivotable in a first horizontal plane. The second end of the extension arm of this embodiment is attached to the first end of the first arm segment 954 via a pivot and/or another type of attachment that allows the first arm segment 954 to pivot generally in a second plane. For example, the first arm segment 954 in fig. 9 may be pivotable in a second vertical plane that is generally perpendicular to the first horizontal plane. However, pivoting of the first arm segment 954 in the second plane may be limited to about 180 degrees due to interference with the extension arm 952. Thus, the second end of the first arm segment 954 is attached to the first end of the second arm segment 956 via a pivot and/or another type of attachment that allows the second arm segment 956 to pivot in a second plane in a direction opposite the first arm segment 954. For example, the second arm section 956 in fig. 9 may be pivotable in a second vertical plane in a direction opposite to the direction of the first arm section 954. The second end of the second arm segment 956 is attached to the DOF device 940 and/or another type of attachment that allows the DOF device 940 to rotate about an axis. In this way, the tomosynthesis system 900 is adjustable in any of x, y and/or z around the object to be imaged. Accordingly, the tomosynthesis system 900 is free to move and rotate for optimal positioning. Accordingly, tomosynthesis system 900 remains generally stationary because it is capable of obtaining multiple projection views of an ROI of an object (e.g., a patient's teeth) without moving either x-ray source 930, x-ray detector 912, or the ROI. This is due at least in part to the articulated arm 950 having the DOF device 940 or structure attached at one end of the articulated arm 950.

The x-ray source 930 and x-ray detector 912 of fig. 9 may be configured in a manner similar to that described above with reference to fig. 1. In some aspects, x-ray source 930 has linearly or otherwise spatially distributed focal spots. In some aspects, the x-ray tube current of each of the pixels in the x-ray source array is configured to be set to the same x-ray tube current with the control unit 960, wherein the extraction voltage is configured to be applied to the extraction gate of each corresponding pixel, and wherein the x-ray exposure level of each of the one or more x-ray projection images is set by varying the exposure time. In some aspects, the systems described herein may operate in a constant exposure mode, where the x-ray exposure level is configured to be adjusted by changing the x-ray tube current of each of the pixels.

In some aspects, the x-ray detector 912 can be an intra-oral x-ray detector configured to be inserted inside the oral cavity of a patient. Additionally, x-ray detector 912 may be extra-oral. Additionally, in some aspects, the x-ray detector can be a digital detector synchronized with x-ray exposure of the spatially distributed x-ray source array to record one or more images of the patient during one or more scans, each of the one or more images generated by x-ray radiation emitted from a corresponding focal spot of the spatially distributed x-ray source array.

In some aspects, the x-ray detector 912 shown in fig. 9 is attached to the x-ray detector holder 910 for snap-in flap imaging applications. For example, fig. 10 provides a more detailed perspective view of one example embodiment of an x-ray detector holder 910. x-ray detector holder 910 can comprise a biocompatible plastic, but other materials functionally useful for 3D dental imaging applications are also contemplated. A first end of an x-ray detector holder, generally designated 902, is shown configured to align with one end of a collimator, while any suitable detector may snap or otherwise fit into a second end of an x-ray detector holder 910, generally designated 904. For example, first end 902 of x-ray detector holder 910 has a generally rectangular profile and has an open center to match the generally rectangular profile of a collimator (see 920, fig. 11A-11B).

As used herein, "collimator" includes an aiming cone (see, e.g., 914, fig. 11A-11B) and/or one or more x-ray limiting collimator plates. A link 908 may connect the first end 902 of the x-ray detector holder to the second end 904 of the x-ray detector holder. The link may have a slight bend or curve to position the second end 904 of the x-ray detector holder generally within the open center of the generally rectangular profile of the first end 902 of the x-ray detector holder 910. The mechanism for attaching the detector to the x-ray detector holder may be integrally formed or otherwise provided at the second end of the x-ray detector holder.

In some aspects, the first end 902 of the x-ray detector holder has a mechanism to hold the x-ray detector holder 910 in removable alignment with the collimator. According to this example embodiment, a plurality of magnets 906 are provided around the perimeter of the generally rectangular profile on first end 902 of x-ray detector holder 910. For example, ten magnets 906 are embedded in the first end portion 902.

Fig. 11A-11B illustrate the x-ray detector holder 910 of fig. 9, the x-ray detector holder 910 being aligned with a second collimator plate 916 at one end of an aiming cone 914 of a collimator, generally designated 920. Second collimator plate 916 in fig. 11A-11B has a generally rectangular profile that corresponds to a generally rectangular profile on first end 902 of x-ray detector holder 910. A plurality of magnets 922 are provided on a generally rectangular profile of second collimator plate 916 that corresponds in position to magnets 906 provided on first end 902 of x-ray detector holder 910. However, the polarity of the magnets is reversed between the magnets on second collimator plate 916 and x-ray detector holder 910 such that when x-ray detector holder 910 and second collimator plate 916 are within sufficient proximity, magnets 906 and 922 on each component attract each other and the components align with each other due to magnetic forces. Advantageously, the coupling between x-ray detector holder 910 and second collimator plate 916 on sighting cone 914 helps to ensure positioning of the two components relative to each other, but the coupling is not a permanent attachment. Thus, the x-ray detector holder 910 and the second collimator plate 916 can be brought out of alignment by applying a tensile or shear force to the magnetic coupling between the two structures and interrupting therebetween.

Fig. 12 provides another illustration of the aiming cone 914 of collimator 920. The sighting cone 914 is placed between a first collimator plate 928 (which has x-ray limiting and/or attenuating properties and/or characteristics) and an exit window 924 of collimator 920 to confine or limit x-ray radiation to a substantially common area on the surface of the intraoral detector without requiring any mechanical movement of the x-ray source 930, the x-ray detector 912, or the collimator plate 916,928. In some aspects, a first end (generally designated 926) of aiming cone 914 is near or otherwise coupled to x-ray source 930, while exit window 924 of aiming cone 914 is near or otherwise coupled to x-ray detector holder 910. The first collimator plate 928 is located at the first end 926 of the sighting cone 914, while the second collimator plate 916 is located at the exit window 924 of the sighting cone 914. In some embodiments, first collimator plate 928 and second collimator plate 916 may each be configured to limit or otherwise attenuate an amount of x-ray radiation emitted from collimator 920 in the direction of x-ray detector holder 910. According to one embodiment, first collimator plate 928 may be configured to manipulate one or more aspects of the x-rays of the respective focal points, while second collimator plate 916 may be configured to further limit the x-ray field to the shape and size of the intra-oral x-ray detector to protect the patient. The first and second collimator plates 916 may each comprise a material having high levels of x-ray limiting and/or attenuation characteristics.

Still referring to fig. 12, the second collimator plate 916 may have an open center or common hole with a smaller diameter than the diameter of the opening or common hole of the sighting cone 914. The common aperture is shaped as a rectangle, but other shapes are also conceivable. Depending on the x-ray detector orientation and/or size, second collimator plate 916 is configured to be interchangeable on aiming cone 914. As such, the second collimator plate 916 may be rotatable, changeable, and/or replaceable with plates having different sized and/or shaped common apertures. The common aperture may be configured to further limit the x-ray field to the shape and size of the intra-oral x-ray detector. For example, where x-ray detector 912 is oriented in a lateral orientation on x-ray detector holder 910, second collimator plate 916 may be similarly oriented in a lateral orientation on sighting cone 914 to match the orientation of x-ray detector 912. In another example illustrative scenario, when x-ray detector 912 is oriented in a longitudinal orientation on x-ray detector holder 910, second collimator plate 916 may be similarly oriented in a longitudinal orientation on sighting cone 914.

Fig. 13 further illustrates the first collimator plate 928. The first collimator plate 928 has one or more holes or apertures 932 configured to align with one or more apertures in the x-ray source to thereby limit, for example, an x-ray field size, beam intensity, and/or beam direction of an x-ray beam from the x-ray source 930. According to the example embodiment of fig. 12 and 13, the seven apertures 932 are linearly distributed across the length of the first collimator plate 928 and correspond to seven apertures (not shown) similarly provided in the x-ray source 930. A bracket 934 for mounting the first collimator plate to the aiming cone 914 and/or the x-ray source 930 is provided and may be integral with the first collimator plate 928. According to this example embodiment, the first collimator plate 928 has four integrally formed brackets 934 for removably mounting the plate to one or both of the aiming cone 914 and/or the x-ray source 930.

Thus, fig. 14 shows an example embodiment of a collimator (generally designated 920) having a sighting cone 914 with a first collimator plate 928 at a first end of the sighting cone 914 and a second collimator plate 916 at a second end of the sighting cone 914. Each of the one or more focal points 948 (seven in this embodiment) emits an x-ray beam 949, the x-ray beam 949 being conditioned by the first collimator plate 928. x-ray beam 949 travels through first collimator plate 928, through collimating cone 914, through second collimator plate 916 to sensors disposed on x-ray detector 912, which x-ray detector 912 is held substantially stationary by x-ray detector holder 910 during use. The second collimator plate 916 may be configured to further limit the x-ray beam to the size and/or shape of the x-ray detector active area dimension (e.g., the area defined in the x-ray detector 912 where data may be collected). As such, collimator 920 may be configured such that x-ray exposure of each focal spot 948 is collimated to the same x-ray detector 912 within a certain percentage of the active detector area dimension. For example, collimator 920 may be configured to collimate x-ray radiation up to about one percent (1%) of the effective detector area dimension. However, larger or smaller percentages are also contemplated without departing from the scope of the subject matter herein.

Referring now to fig. 15, an example embodiment of a degree of freedom (DOF) structure or device, generally designated 940, is shown. DOF device 940 is configured to attach to x-ray source 930 and to an articulated arm 950. In some aspects, DOF device 940 may be attached to x-ray source 930 via a pivot, pin, screw, spring, and/or any other mechanism (which may allow x-ray source 930 to rotate with three independent degrees of freedom relative to an object to be imaged). For example, first arm 942 may be attached to a side surface and a back surface of x-ray source 930 via a pivotable pin 944, the pivotable pin 944 allowing x-ray source 930 to rotate about axes CL3 and CL4, respectively. In this example, the second arm 946 may be attached to the same side surface of the x-ray source 930 as the first arm 942 is attached to, and may be attached to a curve above the top surface of the x-ray source 930, and may be attached to the end of the articulated arm 950. The second arm 946 and the first arm 942 of the DOF device 940 are shown attached to the x-ray source 930 via the same pivotable pin 944, however their attachment may also be accomplished by different pivotable pins 944 that allow the x-ray source 930 to rotate about the axis CL 2. The second arm 946 can be otherwise disposed on the other opposing side surface of the x-ray source 930. Different structural configurations of the DOF device 940 may also be utilized that may allow rotation of the device about the three axes CL2, CL3, and CL4, as will be understood by those skilled in the art.

Referring now to FIG. 16, a perspective view of one example embodiment of a linear x-ray source array (generally labeled 935) is shown. Linear x-ray source array 935 may be configured with similar properties and functionality as described above with reference to x-ray source array 110 of fig. 1 (e.g., linear x-ray source array 935 of fig. 16 may include one or more x-ray focal points). According to this embodiment, linear x-ray source array 935 has a housing 936 for an x-ray tube (e.g., CNT) and one or more pixels, and also has an x-ray exit window 938, the x-ray exit window 938 being configured to provide an exit for one or more x-ray beams and intrinsic filtering. In some aspects, x-ray exit window 938 is configured as a rectangular window to provide an exit to the linearly distributed x-ray pixels. However, in the case where x-ray source array 935 is circular, the shape of x-ray exit window 938 may be correspondingly circular. In all embodiments of the x-ray source array 935, its x-ray exit window 938 can have any suitable shape. Accordingly, it will be apparent to those skilled in the art that x-ray exit window 938 of x-ray source array 935 is configured to correspond to the size and/or shape of the x-ray pixel distribution.

Thus, it follows that the relative orientation of the x-ray source array with respect to the x-ray detector can affect the scan direction. Fig. 17A to 17B illustrate this effect. In fig. 17A, an x-ray source array (generally designated 935) is schematically illustrated as a linearly distributed x-ray source array, oriented with its longitudinal axis a parallel to the x-direction. Thus, in fig. 17A, the scan direction is perpendicular to the root-coronal z-direction, since the object being imaged (e.g., tooth 106) is placed a certain distance away in the y-direction. Conversely, in fig. 17B, x-ray source array 935 is still configured as a linearly distributed x-ray source array oriented with its longitudinal axis a perpendicular to the x-direction. Thus, in fig. 17B, the scan direction is parallel to the root-coronal z-direction, since the object being imaged (e.g., tooth 106) is placed a certain distance away in the y-direction.

Fig. 18 shows a method flow diagram of a static intraoral tomosynthesis method for 3D dental imaging with a static intraoral tomosynthesis system, including the formation and display of a synthetic two-dimensional (2D) intraoral image.

In a first step 1000A, system boot and/or check is initiated. The system guidance and/or examination being initiated may be performed by medical personnel and/or may be performed robotically and/or automatically using a dedicated computing device, which is particularly attached to static intra-oral tomosynthesis systems and/or methods for 3D dental imaging. The special purpose computing device may be a device such as computing platform 804 shown in fig. 8. In some aspects, the system guidance and/or inspection step may include activating respective constituent components, including an x-ray detector, an x-ray array, a computing platform, and the like.

In a second step 1000B, the patient may be enrolled. For example, a patient may be enrolled and a file containing patient information may be accessed (e.g., from data storage 812 in computing platform 804 of fig. 8) and uploaded to a static intraoral tomosynthesis system.

In a third step 1000C, the patient may be placed in a position in which a detector attached to the detector holder may be placed inside the patient's mouth. For example, a patient may sit in a reclining chair and an intraoral detector attached to the detector or x-ray detector holder 910 (e.g., fig. 10) may be positioned within the patient's intraoral cavity adjacent to an ROI (e.g., one or more teeth) within the patient's intraoral cavity.

In a fourth step 1000D, the position of the detector holder may be adjusted to prepare the detector holder for alignment with the sighting cone. For example, a first end of detector or x-ray detector holder 910 (such as one shown in fig. 10) may be prepared for attachment with an aiming cone 914 (see, e.g., fig. 11A-11B).

In a fifth step 1000E, an x-ray detector holder may be coupled to the sighting cone. For example, a first end of x-ray detector holder 910 may be magnetically coupled to aiming cone 914 via a plurality of magnets 906, 922 embedded on the first end of x-ray detector holder 910 and aiming cone 914.

In a sixth step 1000F, the system may be activated to acquire all projection images for 3D tomosynthesis (e.g., activated to perform a tomosynthesis scan). For example, performing a tomosynthesis scan may include collecting one or more x-ray projection images with x-ray radiation emitted from corresponding focal spots or pixels of an x-ray source array, which may be spatially distributed. In some aspects, each of the x-ray pixels in the x-ray source array can be activated individually. In some aspects, x-ray exposure and data collection are configured to be synchronized after a preprogrammed imaging protocol. The pre-programmed protocol may include a series of steps that are performed by the computing platform (e.g., 804 of fig. 8) and its associated static intraoral tomosynthesis system that is programmed prior to the tomosynthesis scan session. For example, the protocol may include: (a) triggering the start of intraoral detector data acquisition by x-ray photons being emitted from a first focal spot for the same dwell time as the x-ray exposure time; (b) after the dwell time, the x-ray radiation of the first focal spot is switched off and the data is transmitted to the computing platform by the intra-oral detector for a fixed readout time; (c) at the end of the fixed readout time, switching on the x-ray radiation of the second focal spot and starting the intraoral detector data acquisition again; and (d) repeating the process until a final x-ray radiation projection image of the final focal spot is recorded. In another example, the protocol may include: (a) triggering the start of intra-oral detector data acquisition for each frame by x-ray photons emitted from the corresponding focal point and presetting a dwell time, which is preset for each of the frames; (b) transmitting data to the computing platform through the intraoral detector after each of the x-ray exposures; and (c) after x-ray image acquisition of each of the frames, resetting the intra-oral detector and repeating the process until the last x-ray projection image of the last focal spot is recorded. Other protocols may also be included, as will be understood by those skilled in the art. Furthermore, the x-ray detector may be configured and/or designed for a particular protocol.

In a seventh step 1000G, image processing and reconstruction may be performed at a computing platform (e.g., 804, fig. 8). For example, each of the image slices acquired from the various x-ray pixels may be reconstructed at computing platform 804 into a single tomosynthesis image. In some aspects, the one or more projection images acquired during the sixth step may be transmitted from the intraoral detector (see fig. 9) to the computing platform 804 by, for example, a wired data transmission line connecting the intraoral detector with the computing platform, wireless transmission, or the like.

In an eighth step 1000H (which may be optional), the 2D image may be synthesized from the 3D reconstructed image in the seventh step. For example, the 2D image may be synthesized from projection directions that are the same or different from the direction in which the one or more original x-ray projection images were collected.

In a ninth step 1000I, the reconstructed 3D image and optionally the 2D composite image may be saved in a database. For example, the database may be the data store 812 in fig. 8 of a dedicated computing platform associated with a static intra-oral tomosynthesis system.

In a tenth step 1000J, the reconstructed 3D image and/or optionally the 2D image is displayable to any medical staff and/or to the patient using a display. For example, a user may be able to access data store 812 (where the reconstructed 3D image and/or the optional 2D image is stored) and be able to display the reconstructed image on a display associated with computing platform 804 of fig. 8. In some aspects, displaying a series of one or more synthetic x-ray projection images from different projection angles may be advantageous because it may allow a healthcare provider (such as a dentist) to better visualize the adjacent interfaces between one or more teeth. In some aspects, the one or more synthetic x-ray projection images may be displayed simultaneously with one or more 3D tomosynthesis slice images (e.g., 3D images used to reconstruct the 3D tomosynthesis images) to enhance characterization and diagnostic accuracy of a disease, such as, for example, a dental disease.

It will be understood that the example method flow diagram of fig. 18 is provided for illustrative purposes only, and that different and/or additional steps may be implemented without departing from the scope of the subject matter described above. It will also be understood that the various steps described herein may occur in a different order or sequence, or may even be omitted entirely.

Although described above with respect to the figures for dental imaging, the above-described systems, methods, and computer-readable media may be used in applications other than dental imaging and are not limited thereto. The inventive subject matter, therefore, may be embodied in other forms without departing from the spirit or essential characteristics thereof. The embodiments described above are therefore to be considered in all respects as illustrative and not restrictive. Although the present subject matter has been described with respect to certain preferred embodiments, other embodiments that are apparent to those of ordinary skill in the art are also within the scope of the present subject matter.

It will be understood that various details of the subject matter described herein may be changed without departing from the scope of the subject matter described herein. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation, as the subject matter described herein is defined by the claims as set forth hereinafter.

Claims

1. A static intra-oral tomosynthesis system for three-dimensional (3D) imaging of an object, the system comprising:

a spatially distributed x-ray source array comprising one or more focal spots;

a degree of freedom (DOF) device attached to the spatially distributed x-ray source array at a first end of an articulated arm, the first end of the articulated arm positioned closest to the object;

a control unit comprising a power supply and control electronics configured to control the spatially distributed x-ray source array, wherein the control unit is attachable to the second end of the articulated arm, wherein the control unit is connected to the spatially distributed x-ray source array via a cable through the interior of the articulated arm or along the articulated arm, and wherein the control unit is mountable to a wall or surface;

an intra-oral detector configured to record one or more x-ray projection images, wherein each of the one or more x-ray projection images is generated by spatially distributing x-ray radiation emitted by a corresponding focal spot of one or more focal spots of an x-ray source array; and

a collimator disposed between the spatially distributed x-ray source array and the patient, wherein the collimator couples the spatially distributed x-ray source array to the x-ray detector, the collimator configured to confine x-ray radiation emitted by one or more focal spots of the spatially distributed x-ray source array to a common area bounded by the intra-oral detector,

wherein the system is configured to perform tomosynthesis reconstruction using the computing platform to generate one or more 3D images using the one or more x-ray projection images.

2. The system of claim 1, wherein the spatially distributed x-ray source array is rotatable about three independent axes defined by a DOF apparatus to align the spatially distributed x-ray source array relative to the object.

3. The system of claim 1, wherein:

the collimator includes:

aiming at the cone;

a first collimator plate disposed at a first end of the collimating cone near the spatially distributed x-ray source array, wherein the first collimator plate comprises one or more apertures, each aperture configured to collimate x-ray radiation emitted by a corresponding focal spot of the one or more focal spots of the spatially distributed x-ray source array, and

a second collimator plate disposed at a second end of the sighting cone near the intra-oral detector, wherein the second collimator plate includes a common aperture configured for all of the one or more focal points, an

Wherein the first and second collimator plates are configured such that x-ray radiation of each of the one or more focal spots is configured to be collimated to a substantially common area on a surface of the intra-oral detector without any mechanical movement of the spatially distributed x-ray source, intra-oral detector, or first and/or second collimator plates.

4. The system of claim 3, wherein the first and second collimator plates are disposed relative to each other in a generally parallel plane of an aiming cone.

5. The system of claim 3, wherein the first collimator panel is fixed to the spatially distributed x-ray source array and the second collimator panel is interchangeable according to the orientation and/or size of the intraoral detector.

6. The system of claim 1, wherein the collimator is configured such that x-ray exposure of each of the focal points is collimated to the intra-oral detector within a range of about one percent of an effective detector area dimension.

7. The system of claim 1, wherein the spatially distributed x-ray source array comprises a carbon nanotube-based field emission x-ray source array.

8. The system of claim 1, wherein the intraoral detector is a digital detector synchronized with x-ray exposure of the spatially distributed x-ray source array to record one or more x-ray projection images during one or more scans, and wherein each of the one or more x-ray projection images is generated by x-ray radiation emitted by a corresponding focal spot of one or more focal spots of the spatially distributed x-ray source array.

9. The system of claim 1, wherein the one or more x-ray projection images are configured to be transmitted from the intraoral detector to the computing platform via a data transmission line or wireless transmission therebetween, the data transmission line connecting the intraoral detector with the computing platform.

10. The system of claim 1, wherein the system is configured to perform a tomosynthesis scan comprising collecting one or more x-ray projection images, wherein the x-ray exposure and the collecting one or more x-ray projection images are configured to be synchronized after a pre-programmed protocol comprising:

activating a first focal spot to emit x-ray radiation for an x-ray exposure time, and triggering acquisition of intra-oral detector data for a dwell time, wherein the dwell time is the same duration as the x-ray exposure time;

after the dwell time, deactivating the first focal spot to stop emission of x-ray radiation therefrom, and transmitting intraoral detector data to the computing platform for a fixed readout time;

activating a second focal spot to emit x-ray radiation for an x-ray exposure time and to trigger a subsequent acquisition of new intra-oral detector data for a dwell time after a fixed readout time;

after the dwell time, deactivating the second focal spot to stop emission of x-ray radiation therefrom, and transmitting new intraoral detector data to the computing platform for a fixed readout time; and

the activating and deactivating steps are repeated until a last x-ray projection image of a last focal spot is acquired and transmitted to the computing platform.

11. The system of claim 1, wherein the system is configured to perform a tomosynthesis scan comprising collecting one or more x-ray projection images, wherein the x-ray exposure and the collecting one or more x-ray projection images are configured to be synchronized after a pre-programmed protocol comprising:

triggering acquisition of intraoral detector data for each of one or more x-ray projection images by x-ray exposure for a dwell time, wherein the x-ray exposure includes x-ray radiation emitted by a corresponding focal spot, and wherein the dwell time is preset for each of the one or more x-ray projection images;

transmitting intraoral detector data to a computing platform after each x-ray exposure;

resetting the intraoral detector after acquisition of each of the one or more x-ray projection images, and

the triggering, transmitting and resetting steps are repeated until a last of the one or more x-ray projection images from the last focal spot is acquired and transmitted.

12. The system of claim 1, wherein:

the control unit is configured to set an x-ray tube current for each of the one or more focal points, each of the one or more focal points configured to the same x-ray tube current,

the control unit is configured to apply an extraction voltage to the extraction grid of the cathode of each corresponding focal point, and the x-ray exposure level of each of the one or more x-ray projection images is set by changing the x-ray exposure time.

13. The system of claim 1, further comprising an x-ray detector holder configured to couple to the collimator at a first end of the x-ray detector holder and to an intra-oral detector at a second end of the x-ray detector holder, wherein the intra-oral detector is mounted at the second end of the x-ray detector holder and configured to be placed inside an oral cavity of a patient, and wherein the first end of the x-ray detector holder is coupled to an exit window of the collimator.

14. The system of claim 13, wherein a plurality of magnets are disposed on a surface of the first end of the x-ray detector holder and the collimator to magnetically couple the x-ray detector holder to the collimator.

15. The system of claim 1, wherein the system operates in a constant exposure mode, wherein an x-ray exposure level can be adjusted by changing an x-ray tube current of each of the one or more focal points.

16. A method for three-dimensional (3D) imaging with a static intraoral tomosynthesis system, the method comprising:

positioning a spatially distributed x-ray source array of a static intraoral tomosynthesis system outside an oral cavity of a patient, wherein the spatially distributed x-ray source array comprises one or more focal spots;

positioning an x-ray detector inside an oral cavity of a patient with an x-ray detector holder configured for at least one imaging protocol, wherein the x-ray detector holder comprises a plurality of magnets disposed on a first end of the x-ray detector holder, the first end being located outside the oral cavity of the patient;

providing a first collimator plate on a first end of a collimator and a second collimator plate on a second end of the collimator, wherein the second collimator plate is selected to correspond to one or more aspects of an x-ray detector holder for at least one imaging protocol;

coupling the spatially distributed x-ray source array and the collimator to the x-ray detector holder via a second collimator plate by coupling the second collimator plate to a second end of the collimator and to a first end of the x-ray detector holder;

acquiring one or more x-ray projection images of the patient's oral cavity from one or more viewing angles by sequentially activating each of one or more focal spots of a preset radiation dose and x-ray energy, wherein the one or more x-ray projection images are two-dimensional (2D);

transmitting the one or more x-ray projection images to a computing platform;

reconstructing one or more 3D tomosynthesis images from the one or more x-ray projection images using one or more iterative reconstruction algorithms; and

the one or more 3D tomosynthesis images are processed and the one or more 3D tomosynthesis images are displayed on one or more monitors, the one or more monitors being electrically connected to the computing platform.

17. The method of claim 16, wherein the one or more iterative reconstruction algorithms comprise performing an iterative truncation artifact reduction method to enhance image quality and maximize a field of view of an x-ray detector of a given size.

18. The method of claim 16, comprising generating one or more synthetic x-ray projection images from a projection direction that is the same as or different from a direction in which at least one of the one or more x-ray projection images was collected, wherein the one or more synthetic x-ray projection images are two-dimensional (2D).

19. The method of claim 18, comprising simultaneously displaying the one or more 3D tomosynthesis images and the one or more synthetic x-ray projection images to enhance characterization and diagnosis of dental disease.

20. The method of claim 16, comprising displaying a series of one or more x-ray projection images from different projection angles to enhance visualization of a proximity interface between one or more teeth.

21. A non-transitory computer-readable medium comprising computer-executable instructions that, when executed by a processor of a computer, control the computer to perform a method, the method comprising:

transmitting the one or more x-ray projection images to a computing platform;

22. The non-transitory computer readable medium according to claim 21, comprising rotating the spatially distributed x-ray source array about three independent axes defined by a degree of freedom (DOF) device to align the spatially distributed x-ray source array relative to an oral cavity of the patient, the spatially distributed x-ray source array attached to the DOF device.