CN201242531Y - Scanning imagery system for straight-line track - Google Patents
Scanning imagery system for straight-line track Download PDFInfo
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Abstract
一种直线轨迹扫描成像系统和方法，该成像系统包括：射线发生单元，包含多个射线源，所述多个射线源交替出束，在同一时间只有一个射线源出束；传动装置，用于使检查对象与所述直线轨迹扫描系统沿直线轨迹相对运动，从而使检查对象穿过所述直线轨迹扫描成像系统的扫描区域；数据采集单元，对于每个射线源，分别采集检查对象的投影数据；成像单元，根据对于每个射线源采集的投影数据，重建所述检查对象的图像；显示单元，用于显示重建的图像。通过采用多个按照一定的空间分布排列，并以一定的时间顺序交替出束的射线源，可以以较短的探测器长度获得较大的扫描视角，从而减少系统所需探测器单元数量并缩小被检物体的总扫描距离。
A linear trajectory scanning imaging system and method, the imaging system includes: a ray generating unit, including a plurality of ray sources, the plurality of ray sources emit beams alternately, and only one ray source emits beams at the same time; a transmission device for The inspection object and the linear trajectory scanning system move relatively along the linear trajectory, so that the inspection object passes through the scanning area of the linear trajectory scanning imaging system; the data acquisition unit collects the projection data of the inspection object for each ray source an imaging unit, reconstructing an image of the inspection object according to the projection data collected for each ray source; a display unit, configured to display the reconstructed image. By adopting multiple ray sources arranged in a certain spatial distribution and alternately emitting beams in a certain time sequence, a larger scanning angle of view can be obtained with a shorter detector length, thereby reducing the number of detector units required by the system and shrinking the size of the beam. The total scanning distance of the inspected object.
Description
Technical Field
The utility model relates to a radiation imaging field, more specifically, the utility model relates to a linear track scanning imaging system.
Background
The safety inspection has very important significance in the fields of anti-terrorism, fighting against drug trafficking, smuggling and the like. After 911 in the united states, security inspection has become increasingly important in countries around the world, particularly in public areas such as airports, stations, customs, and docks, where a series of security inspection measures are taken to strictly inspect passenger luggage, cargo containers, and the like.
Currently, the mainstream imaging technology adopted by the widely used security inspection system is radiation imaging technology. The radiation imaging technology adopts a ray source to irradiate an inspection object on one side of the inspection object according to the exponential attenuation principle of rays, the rays penetrate through the inspection object and are received by a ray acquisition device, the ray acquisition device converts the received rays into digital signals and outputs the digital signals to a computer for imaging, and the computer processes acquired data, synthesizes or reconstructs images and displays the images. A security inspection system employing radiation imaging technology is capable of tomographic or fluoroscopic imaging. The tomography displays the tomography image of the inspection object, and can combine the multilayer tomography images into a three-dimensional image; whereas fluoroscopic imaging shows a two-dimensional fluoroscopic image of an examination object.
Since Tomography requires a radiation acquisition device to receive an omnidirectional radiation of an object under examination to obtain transmission projection data of a radiation beam, a Tomography security inspection system generally requires a Computed Tomography (CT) apparatus in which at least one of the object under examination and the radiation source should be capable of rotating. In practical applications, the safety inspection system generally needs on-line real-time inspection, and the imaging speed of the safety inspection system is required to be very high, for example, for civil aviation article inspection, since the clearance rate is required to be 0.5 m/s, even a helical CT apparatus with a large pitch is difficult to achieve. In addition, for large objects, such as customs containers, it is very difficult to rotate either the container or the source of radiation. In addition, the cost of the CT apparatus is high, and the safety inspection system using the CT apparatus for three-dimensional imaging cannot be widely used due to the above factors.
Compared with a tomography safety inspection system, the perspective imaging safety inspection system is widely applied to public places such as airports, stations, customs and docks. However, the perspective imaging safety inspection system cannot avoid the overlapping effect of the objects in the ray direction, and cannot solve the problem of the overlapping of the objects in the ray direction, so that the inspection capability of the perspective imaging safety inspection system is seriously insufficient.
In patent applications with application numbers 200510123587.6, 200510123588.0, and 200610076573.8 (publication numbers CN1971414, CN1971620, and CN101071109, respectively) filed by the applicant of the present application, a single-segment and multi-segment linear trajectory scanning imaging mode is proposed, in which during the scanning process, an object to be detected between a radiation source and a detector array is moved linearly relative to the radiation source and the detector array (an opening angle formed by the radiation source and the detector array is a scanning view angle during imaging), the radiation source and the detector and the object do not rotate relative to each other, so that the requirement of fast imaging of a security inspection system can be basically met, and the problems of difficult rotation of a large object and overlapping of objects in the ray direction of a perspective imaging security inspection system can be solved. In the multi-segment linear track scanning imaging, the travel track of an inspection object comprises at least two segments of linear tracks which form an angle with each other; and the object under examination makes only translational motion on the at least two linear trajectories without any rotation. In the multi-section linear track scanning imaging mode, the plurality of detector arrays arranged on the multi-section linear track are adopted, the same ray source is used for irradiating the inspection object for multiple times, and the scanning visual angle of the system can be expanded by multiple times (depending on the number of sections of the linear track and the number of the detector arrays), so that the problem of limited angle projection in the practical application of a single-section linear track can be solved. However, the above-described imaging systems all have a common deficiency: in order to make the detector and the radiation source form a large enough scanning angle to obtain a high-quality imaging image, the detector must cover a long enough range in the object moving direction, which results in high cost of the detector and long scanning distance of the detected object in the imaging system.
SUMMERY OF THE UTILITY MODEL
The invention aims to provide a linear track scanning imaging system which can meet the requirement of rapid imaging of a safety inspection system, solve the problems of difficult rotation of a large object and object overlapping of a perspective imaging safety inspection system in the ray direction and realize a larger scanning visual angle by using a shorter detector.
The above object is achieved by a linear trajectory scanning imaging system according to the present invention. The linear track scanning imaging system comprises: the method comprises the following steps: the ray generating unit comprises a plurality of ray sources, the ray sources alternately emit beams, and only one ray source emits beams at the same time; the transmission device is used for enabling the inspection object and the linear track scanning system to move relatively along a linear track, so that the inspection object passes through a scanning area of the linear track scanning imaging system; the data acquisition unit is used for respectively acquiring projection data of the inspection object for each ray source; an imaging unit for reconstructing an image of the examination object from the acquired projection data for each radiation source; and a display unit for displaying the reconstructed image.
Another object of the present invention is to provide a linear trajectory scanning imaging method, comprising the following steps: moving an examination object relative to a scanning imaging system into a scanning region of the scanning imaging system; controlling a plurality of ray sources to emit beams alternately to ensure that only one ray source emits beams at the same time; for each ray source, acquiring corresponding projection data by a detector array respectively; reconstructing an image of the examination object from the projection data acquired for each radiation source; and displaying the reconstructed image.
Because the invention adopts a plurality of ray sources which are arranged according to certain spatial distribution and alternately emit beams in a certain time sequence, a larger scanning visual angle can be obtained by a shorter detector length, thereby reducing the number of detector units required by the system and shortening the total scanning distance of the detected object.
Because the invention adopts the linear track scanning to replace the circular track or spiral track scanning, the inspection object basically moves linearly without considering the centrifugal force problem in the circular or spiral motion, the inspection object can be quickly imaged, the imaging speed of the inspection object is greatly improved, the imaging time of the inspection object is reduced, the requirement of the clearance rate of the object inspection can be well met, the clearance rate of the object inspection can be further improved, and the invention is very favorable for the inspection system requiring higher clearance rate.
Because the invention adopts the linear track scanning to replace the circular track or spiral track scanning, the inspection object moves linearly, the large object does not need to rotate any more, the problem of difficult rotation of the large object is solved, and the invention is very beneficial to the inspection system which requires to inspect the large object.
Because the invention can obtain the tomographic image and the stereo image of the inspection object, the invention well solves the problem of object overlapping existing in the traditional transmission imaging safety inspection system during imaging. Moreover, the invention can also obtain conventional perspective images with single or multiple visual angles, so that the system of the invention can carry out initial detection on the object to be detected by obtaining the perspective images of the object to be detected first, and carries out tomography imaging on the object to be detected when a possible suspected area is found, thereby further detecting the suspected area.
The invention does not need to rotate the inspection object or the ray source and utilizes the characteristic of linear transmission of the inspection object in the prior safety inspection system, so the mechanical design of the invention is very simple and the realization cost is very low.
Drawings
FIG. 1 schematically illustrates a block diagram of one embodiment of a multi-source linear trajectory scanning imaging system according to the present invention.
FIG. 2 schematically illustrates a plan view of a dual source linear track scanning imaging system in accordance with the present invention.
FIG. 3 schematically shows a schematic plan view of a multi-source (N >2) linear trajectory scanning imaging system according to the present invention.
Fig. 4 schematically shows a scanning perspective view of a single radiation source emitting a beam in an imaging system according to the present invention.
Figure 5 schematically shows a scan geometry definition in a linear trajectory imaging system according to the invention.
FIG. 6 schematically illustrates a flow diagram of one embodiment of a multi-source linear trajectory scanning imaging method in accordance with the present invention.
Detailed Description
The following detailed description of the embodiments is merely illustrative of the present invention and is not intended to limit the scope of the invention.
The multi-source linear track scanning imaging system obtains projection data by using multi-source linear track scanning, and obtains a tomographic image by using CT image reconstruction and data processing technology to realize three-dimensional imaging. The basic idea of the invention is: the advancing track of the inspection object is a straight track; the receiving plane of the detector array is set to be parallel to the corresponding straight line track, and at least two ray sources are arranged on the same side of the detector array, preferably distributed on a straight line parallel to the running track of the inspection object; each ray source and the detector array form independent scanning visual angles respectively, but partial overlapping is allowed; in the working process, the ray generating unit and the data acquisition unit are kept still, the inspection object runs along the travel track of the inspection object, and when the inspection object quickly enters the scanning range of the first ray source (which can be detected by a position trigger device), the system starts to acquire data. The radiation source adopts a pulse working mode to alternately emit beams (as shown in figure 2), so that the system of the invention can realize a wider range of scanning visual angles by a detector array with shorter length, thereby being capable of carrying out higher-quality tomography on the checked object and simultaneously carrying out conventional perspective imaging on the checked object at different angles.
FIG. 1 schematically illustrates a block diagram of one embodiment of a multi-source linear trajectory scanning imaging system according to the present invention. The multi-source linear track scanning imaging system comprises a ray generating unit 11, a transmission device 18, a data acquisition unit 12 and a display unit 16. In a preferred embodiment, the multi-source linear trajectory scanning imaging system includes one or more of an imaging unit 13, an image processing and recognition unit 14, a correction unit 15, and a main control unit 17.
The radiation generating unit 11 comprises a plurality of radiation sources 1. Including an X-ray accelerator, an X-ray machine or a radioisotope, and corresponding auxiliary equipment. The total number of the ray sources is more than or equal to two, and all the ray sources are arranged on the same side of the detector, preferably on the same straight line or the same plane. Each ray source forms an independent scanning visual angle with the detector array, but partial overlapping is allowed. The radiation sources can adopt a pulse working mode, and all the radiation sources emit beams alternately at certain time intervals, preferably, only one radiation source emits beams at the same time.
The actuator 18 may be a mechanical actuator for carrying and transporting the object under examination (or source and detector) and defining a trajectory of travel of the object under examination within the system. Preferably, the transmission device 18 may include a conveying device 20 and an electric control unit 19, the conveying device 20 being used for supporting and conveying the inspection object (or the radiation source and the detector); the electrical control unit 19 is adapted to control the transport means 20 for controlling the movement of said examination object along said path of travel, the object movement being relative to the source and detector movement, and being equivalent, and will be described in the following in terms of object movement, but it should be clear that the source and detector movement have the same meaning. In the multi-source linear track scanning imaging, the inspection object makes linear translation along with the conveying device, and preferably, the inspection object makes uniform linear motion in the multi-source linear track scanning imaging system.
The data acquisition unit 12 is used to acquire the radiation transmitted through the examination object and convert it into digital signals. The data acquisition unit 12 includes a detector array, which may be a linear array detector or an area array detector, and the detectors in the detector array are generally arranged at equal intervals, or arranged at equal angles, and are used to obtain the attenuated ray intensity information of the cone beam ray after passing through the object to be detected. The detector can be a solid detector, a gas detector or a semiconductor detector. The detectors need not be closely arranged, but need to cover a certain range in the X-axis direction (the moving direction of the object to be inspected), so as to form a certain scanning view angle with each ray source. The detector also comprises a signal conversion circuit, which is used for converting the ray beam signals received by the detector array into transmission data; a data processing circuit for combining the transmission data from the signal conversion circuit into projection data; and the logic control circuit is used for controlling the detector array to receive the ray beam signals and the data processing circuit to transmit projection data synchronously. Preferably, during data acquisition, equal-interval sampling is performed during the translational motion of the examination object along the linear track. The data acquisition trigger needs to be synchronized with the radiation source beam-emitting trigger for subsequent data processing.
The optional main control unit 17 is responsible for main control of the operation process of the whole imaging system, including mechanical control, electrical control, data acquisition control, safety interlocking control and the like. It is clear to a person skilled in the art that these control operations performed by the master control unit 17 may also be implemented in a distributed manner, i.e. by the control means of the individual components of the imaging system themselves. Preferably, the main control unit 17 comprises a trigger pulse generator for generating a respective trigger pulse sequence for each radiation source, the trigger pulse sequence being used for controlling the respective radiation sources to emit beams alternately in a pulsed manner. It is noted that the trigger generator may also be located elsewhere, generating a trigger pulse sequence under the control of the master control unit 17. Alternatively, the main control unit 17 may be absent, and the trigger generator interacts with the radiation generation unit 11 and the data acquisition unit 12, and then generates a trigger pulse sequence according to the interaction.
The imaging unit 13 is responsible for processing and reconstructing projection data to be acquired by the data acquisition unit, thereby generating a perspective image, a tomographic image, and a stereoscopic image of the inspection object. Because the reconstruction process involves projection data generated by a plurality of ray sources, the known synchronization relationship between the data acquisition trigger and the beam-emitting trigger of each ray source needs to be utilized to extract the projection data when each ray source emits a beam independently. The contribution of the projection data generated by each ray source to the reconstructed image can be carried out before or after the image reconstruction.
The display unit 16 is used to display the image reconstructed by the imaging unit 13. The perspective image can be formed by extracting and combining output data of a certain array of the area array detector on a time sequence.
Preferably, the multi-source linear trajectory scanning imaging system according to the present invention further includes a correction unit 15 for correcting the reconstructed image before the reconstructed image is displayed on the display unit 16 so as to optimize the reconstructed image. The correction includes detection of inconsistencies, hardening corrections, scattering corrections, metal artifact corrections, and the like.
Preferably, the multi-source linear track scanning imaging system according to the present invention further comprises an image processing and recognizing unit 14 for image processing, pattern recognition, and the like. In image processing and pattern recognition, techniques such as image enhancement, edge detection, intelligent identification of dangerous goods, and the like are generally used.
Preferably, the multi-source linear track scanning imaging system according to the present invention may first obtain conventional perspective images of single or multiple viewing angles, so that the system of the present invention may perform an initial inspection on an inspection object by obtaining the perspective image of the inspection object first, and perform tomography only when a possible suspected area is found, thereby further inspecting the suspected area.
Fig. 2 schematically shows a schematic plan view of a dual-source linear trajectory scanning imaging system according to the present invention, which shows an exemplary embodiment of building a stereoscopic imaging security inspection system by using the present invention. In fig. 2, the number of the radiation sources is two, the two radiation sources are respectively installed at two ends of the detector array, and a connecting line between the two radiation sources is parallel to a linear motion track of the inspection object. The fan angle (the opening angle in the moving direction of the inspection object) of each radiation source is 60 degrees, the effective scanning view angle range of the first radiation source is 90-150 degrees, the effective scanning view angle range refers to the incident angle range of all the rays which can reach the detector array in the rays emitted by the radiation source in the moving direction of the inspection object, and the scanning view angle range of the second radiation source is 30-90 degrees, so that the two fan angles are combined together skillfully to obtain a complete 120-degree scanning view angle range: 30-150 degrees, i.e. the scan view angle of the whole imaging system is 120 degrees. It should be noted that although the fan angles of the two radiation sources are equal to 60 degrees in the present embodiment, they may be other angles and may be different from each other. Moreover, the scanning view angle ranges of the two radiation sources may also partially overlap, for example, the effective scanning view angle range of the first radiation source is 80-140 degrees, and the scanning view angle range of the second radiation source is 40-100 degrees, so that the scanning view angle range of the whole system is 100 degrees: 40-140 degrees. Of course, the first and second radiation sources may take other scan views.
The situation with more radiation sources can be analogized (as shown in figure 3). The ray sources are triggered alternately at certain time intervals in a pulse working mode to ensure that only one ray source emits a beam at the same time. The source of radiation may be an X-ray tube, an accelerator source of radiation, or an isotope source, depending on the size of the object and the context of the application.
FIG. 3 schematically shows a plan view of a multi-source (N >2) linear trajectory scanning imaging system according to the present invention. Like fig. 2, the scan view angle of the multi-source linear trajectory scan imaging system of fig. 3 is also obtained by combining the fan angles of each of the ray sources. That is, the obtained system scanning view angle range is a union of effective scanning view angle ranges of the N ray sources, when the scanning view angle ranges of each ray source are continuous but do not overlap with each other, the obtained system scanning view angle is the sum of the effective scanning view angles of the N ray sources, and when the scanning view angle ranges of some ray sources partially overlap with each other, the obtained system scanning view angle is the sum of the effective scanning view angles of the N ray sources minus the overlapping portion.
Fig. 4 schematically shows a scanning perspective view of a single radiation source emitting a beam in an imaging system according to the present invention.
In fig. 4, the inspection object is placed on a transfer platform (shown as a transfer belt in the drawing) of a transfer device 20 of a transfer device 18, and is smoothly transferred along a linear trajectory in the multi-source linear trajectory scanning image forming system according to the present invention under the control of an electric control unit 19.
In fig. 4, the detector array is an area array detector, which is located opposite to the radiation source and perpendicular to the driving platform. The detector covers the object in the vertical direction, and the field angles formed by the detector and the two ray sources in the horizontal direction are respectively 60 degrees, so that the total scanning visual angle can reach 120 degrees under the condition that the two ray sources exist. Triggering of acquisition in the data acquisition process needs to be synchronized with triggering of beam emission of the ray source, so that data of two 60-degree scanning view angles can be recombined into data of a 120-degree scanning view angle in subsequent data processing, or images reconstructed from the data of the two 60-degree scanning view angles are combined into an image reconstructed from the data of the 120-degree scanning view angle. This will be further described later.
In this embodiment, the control, data transmission, image reconstruction, and data processing of the entire imaging system are performed by a computer (workstation), scanning control information, position information, projection data, and the like are input to the computer workstation through a data acquisition system, and the workstation performs the reconstruction of the transmission image, the tomographic image, and the three-dimensional stereoscopic image of the object, and finally displays the reconstructed image on a display. That is, one or more of the ray generation unit 11, the data acquisition unit 12, the imaging unit 13, the image processing and recognition unit 14, the correction unit 15, the display unit 16, and the main control unit 17 may be implemented in the one computer workstation.
To achieve accurate image reconstruction, the imaging system should be able to accurately measure or calibrate the following system parameters: the position of each ray source, the distance T from each ray source to the detector, the distance D from each ray source to the linear motion track of an object to be inspected, the linear motion speed v of a transmission device, the sampling interval delta T of an array detector (the equivalent sampling interval of a space for receiving transmission data by a detector array is delta D which is v delta T), and the physical size of the detector, including the physical size of a single detector and the physical size of the detector array.
The imaging unit 13 receives projection data when the plurality of radiation sources alternately emit beams from the data acquisition unit 12, and reconstructs a tomographic image and a stereoscopic image from the projection data obtained by each radiation source. Because the reconstruction process involves projection data generated by a plurality of ray sources, the known synchronization relationship between the data acquisition trigger and the beam-emitting trigger of each ray source needs to be utilized to extract the projection data when each ray source emits a beam independently. The contribution of the projection data generated by each ray source to the reconstructed image can be carried out before or after the image reconstruction. The former processing idea is to equate projection data generated by a plurality of source line sources to projection data in a single source (single source, it is enough to enlarge the coverage of the detector array), and this processing method has the advantage of handling the problem that there may be overlapping scan view angles in each source line (i.e. projection data redundancy, which is a very common phenomenon in image reconstruction, and can be eliminated by doing a simple weighting), but this method requires that each source line needs to be at least on a plane parallel to the detector array (T, D value of each source line). The processing idea of the latter is to reconstruct sub-images by using projection data generated by each ray source respectively, and then to perform weighted superposition on the reconstructed sub-images according to pixels under the condition of considering data redundancy, so as to obtain a final reconstructed image.
The imaging principles of the present invention will be further explained in a mathematical description language with reference to the geometric parameter definitions of fig. 5.
Although the radiation source and the detector are fixed in actual scanning and the object to be inspected (to be reconstructed) is translated to the left and right, for convenience of mathematical description, according to the principle of relativity of motion, it is assumed herein that the object to be inspected is still and the radiation source and the detector are moved from the right to the left as a whole when image reconstruction is performed. In fact, the multi-source linear trajectory scanning imaging system according to the present invention can be regarded as a combination of a plurality of independent single-source systems, however, the plurality of single-source systems share the same detector array. Therefore, the description of the multi-source system can be simplified by describing the operation principle of the single-source system.
Fig. 5 schematically shows the scan geometry definition of the linear trajectory imaging system, which corresponds to the linear trajectory scan imaging when a single radiation source emits a beam as shown in fig. 4.
The plane containing the motion trail of the ray source and perpendicular to the area array detector is set as an x-y plane. Let O be the origin of the object coordinate system (x, y, z), which is stationary since the examination object is assumed to be stationary for the sake of mathematical description, and its orthogonal projection point O on the motion trajectory of the radiation sourcesDefined as the source position zero point. For convenience, the concept of an equivalent detector is used, that is, a real area array detector is virtualized to an x-z plane on which a coordinate origin O is located according to a geometric mapping relationship. Orthogonal projection point O of ray source A on equivalent detectordSet as the zero point of the equivalent detector unit position and the distance between the two is represented by D. If the source and detector are reversed along the x-axis at a velocity c<0 shift, at some point in time, the source position index value is denoted by l (which is relative to O)sOffset of (d), the detector cell position index value is represented by (t, v) (which is relative to O)dHorizontal and vertical offsets) then the cone-beam projection acquired by the detector unit may be denoted as p (l, t, v). Wherein, the coordinates of the corresponding ray source and the equivalent detector unit in the object coordinate system are (l, -D, 0) and (l + t, 0, v), respectively.
Image reconstruction of a single ray source may be performed using a straight-line filtered back-projection algorithm. For the projection data p (l, t, v), the object under examination is denoted f (r, Φ, z) in a cylindrical coordinate system, and the transformation from the three-dimensional planar coordinate system to said cylindrical coordinate system is well known to the person skilled in the art and will not be described in further detail herein. In the cylindrical coordinate system, an approximate estimate f (r, φ, z) of the object f (r, φ, z) to be inspected is:
wherein,
Q(l′，t，z)＝∫q(l，t，z)h(l′-l)dl
q(l，t，z)＝p(l-t，t，z)
here, [ t ]m1，tm2]The coverage of the detector array in the X-axis direction is characterized. h is a convolution kernel function with a theoretical value of <math> <mrow> <mi>h</mi> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> <mo>=</mo> <msubsup> <mo>∫</mo> <mrow> <mo>-</mo> <mo>∞</mo> </mrow> <mo>∞</mo> </msubsup> <mrow> <mo>|</mo> <mi>ω</mi> <mo>|</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>πωl</mi> </mrow> </msup> <mi>dω</mi> <mo>,</mo> </mrow></math>
The discretization generally adopts an RL or SL filter, and the discrete form of the SL filter is as follows:
the linear filtering back projection algorithm is characterized in that: and filtering the received projection data along the data acquisition direction l, and integrating the received projection data along the detector direction t to realize back projection processing. This characteristic is determined by the straight scan trajectory. Compared with a rearrangement algorithm for rearranging acquired data into parallel beams, the linear filtering back projection algorithm can more fully utilize each received effective projection data, further can better keep the resolution of a reconstructed image, and has far lower sensitivity to data truncation than the rearrangement algorithm
It can be seen that the parameters (l, t, v) of the projection data p (l, t, v) when beams are emitted from different radiation sources are not completely the same, i.e. corresponding to different scanning angles, and if the parameters are the same, the data are redundant, and accordingly, weighting processing is required. The simplest method is to take the projection data of the same parameters for averaging. If the distances from the respective radiation sources to the detector are different, it means that the scanning planes of the respective radiation sources at the same point of the object under examination are different, which may cause artifacts in the final reconstructed image of the image. Therefore, in order to obtain a high quality image, the individual radiation sources preferably need to be in the same plane parallel to the detector array. More preferably, each source is on a line parallel to the detector array.
FIG. 6 schematically illustrates a flow diagram of one embodiment of a multi-source linear trajectory scanning imaging method in accordance with the present invention. The multi-source linear trajectory scanning imaging method according to the present invention starts at step S1. In step S2, the actuator 18 moves the object under examination relative to the scanning imaging system along a linear trajectory into a scanning region of the scanning imaging system. In a preferred embodiment, the radiation generating unit 11 and the data acquisition unit 12 are kept stationary, and the transmission 18 carries the examination object along the travel path. In step S3, the main control unit 17 controls the plurality of radiation sources to emit beams alternately, ensuring that only one radiation source emits a beam at a time. Preferably, the plurality of radiation sources alternately emit beams in a pulse working mode. In step S4, projection data of the examination object are acquired by the data acquisition unit 12 for each beam-out of each radiation source, which beam-out is synchronized with the data acquisition of the data acquisition unit, which synchronization may be controlled by the same trigger pulse sequence. When the object under examination is about to enter the scanning range of the first radiation source (which can be detected by a position trigger device), the data acquisition unit 12 starts to acquire data. In step S5, the imaging unit 13 reconstructs an image of the object under examination from the projection data acquired separately for each radiation source. In step S6, the display unit 16 displays the reconstructed image. Preferably, the reconstructed image is image processed and identified to identify the hazardous material before the reconstructed image is displayed on the display unit 16. Preferably, the reconstructed image is corrected to optimize the reconstructed image before it is displayed on the display unit 16. Preferably, conventional perspective images of a single or multiple viewing angles can be reconstructed and displayed, so that the examination object can be initially examined by obtaining the perspective images of the examination object first, and when a possible suspect region is found, the suspect region is further examined by performing tomography imaging. Finally, in step S7, the multi-source linear trajectory scanning imaging method according to the present invention ends.
Although the present invention has been described with reference to specific preferred embodiments, those skilled in the art will appreciate that various modifications, additions, substitutions and changes can be made without departing from the scope of the invention.
Claims (16)
1. A linear trajectory scanning imaging system comprises a display unit for displaying a reconstructed image,
characterized in that, the linear track scanning imaging system still includes:
the ray generating unit comprises a plurality of ray sources, the ray sources alternately emit beams, and only one ray source emits beams at the same time;
the transmission device is used for enabling the inspection object and the linear track scanning system to move relatively along a linear track, so that the inspection object passes through a scanning area of the linear track scanning imaging system;
the data acquisition unit is used for respectively acquiring projection data of the inspection object for each ray source; and
an imaging unit reconstructs an image of the examination object from the acquired projection data for each radiation source.
2. The linear trajectory scanning imaging system of claim 1, wherein the plurality of radiation sources alternate beam emission in a pulsed mode of operation.
3. The linear trajectory scanning imaging system of claim 2, further comprising a trigger generator for generating a sequence of trigger pulses for each of said plurality of radiation sources to control said plurality of radiation sources to alternate beams.
4. The linear trajectory scanning imaging system of claim 3, wherein the trigger pulse generated by the trigger pulse generator is further transmitted to the data acquisition unit for controlling the timing of the data acquisition.
5. The linear trajectory scanning imaging system of claim 1, further comprising a master control unit for controlling and coordinating operation of the components of the linear trajectory scanning imaging system.
6. The linear trajectory scanning imaging system of claim 1, wherein the plurality of radiation sources are located in a plane parallel to a trajectory of the object under examination.
7. The linear trajectory scanning imaging system of claim 4, wherein the plurality of radiation sources are positioned in a line parallel to a trajectory of the object under examination.
8. The linear trajectory scanning imaging system of any one of claims 1-7, wherein the range of ray scanning views of each of the plurality of ray sources is continuous, thereby forming a continuous range of scanning views.
9. The linear trajectory scanning imaging system of claim 8, wherein the ray scanning view angle ranges of each of the plurality of ray sources partially overlap one another.
10. The linear trajectory scanning imaging system of any one of claims 1-7, further comprising a correction unit for correcting an image prior to displaying said reconstructed image.
11. The linear trajectory scanning imaging system of any one of claims 1-7, further comprising an image processing and recognition unit for processing and recognizing the reconstructed image.
12. The linear trajectory scanning imaging system of any one of claims 1-7, wherein the object under examination moves at a constant velocity with respect to the linear trajectory scanning system.
13. The linear trajectory scanning imaging system of any one of claims 1-7, wherein the actuator includes an electrical control unit for controlling the actuator to control the relative motion between the examination object and the linear trajectory scanning system.
14. The linear track scanning imaging system according to any one of claims 1 to 7, wherein the imaging unit reconstructs a stereoscopic image of the inspection object by generating a perspective image, a tomographic image of the inspection object.
15. The linear trajectory scanning imaging system of any one of claims 1-7, wherein the data acquisition unit acquires projection data in synchronization with the beam-out of each of the plurality of radiation sources.
16. The linear track scanning imaging system of any one of claims 1 to 7, wherein said data acquisition unit is a line array detector or an area array detector.
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| CNU2008200800191U CN201242531Y (en) | 2008-04-17 | 2008-04-17 | Scanning imagery system for straight-line track |
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| WO2009127118A1 (en) * | 2008-04-17 | 2009-10-22 | 清华大学 | Imaging system using a straight-line trajectory scan and method thereof |
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