HK1024194B - Proton beam digital imaging system - Google Patents

Description

Proton beam digital imaging system

Technical Field

The present invention relates to particle beam therapy systems, and more particularly to a digital imaging system for imaging a target region in a patient's body to determine the position of the patient relative to the particle beam emitting system, thereby enabling the patient to be adjusted to a desired position.

Background

Radiation particle therapy is commonly used to treat localized types of cancer as well as other diseases. Typically, atomic particles, such as electrons, protons, neutrons, or sub-atomic particles, such as X-rays, are emitted from a nozzle toward a particular target region of a patient, often referred to as the target isocenter. The particles strike cells in the target region of the patient, killing them.

One particularly useful radiation therapy is proton beam therapy, in which protons are bombarded at the target isocenter within the patient. Proton therapy takes advantage of the proton, i.e., the proton has a phenomenon known as bragg peak, i.e., when the proton comes to rest, a significant portion of the energy of the proton is released. Thus, by selecting the initial energy of the proton beam, the protons in the proton beam can be directed to and stop at the target isocenter, thereby delivering a substantial portion of their energy to the cells within the target isocenter. Proton therapy is currently being used by the Loma Linda University medical center (Loma Linda University medical center) of Loma Linda, california, the system used by which is described in detail in U.S. patent No. 4870287.

Although proton therapy has significant clinical advantages over other types of therapy in certain situations, it still requires precise placement of the patient relative to the proton beam nozzle so that the proton beam impinges only at the target isocenter. Otherwise, the proton beam may kill healthy cells in the patient. This is particularly important, for example, when treating a target isocenter located in the brain of a patient. In many other types of radiotherapy, accurate positioning of the patient is of course important for similar reasons, if it is said that accurate positioning of the patient with respect to the nozzle is important in proton therapy.

Typically, a patient undergoing proton therapy is treated periodically, that is, the target isocenter is repeatedly irradiated with a proton beam over a longer period of time. For example, a patient may receive a dose of proton radiation therapy daily over a period of one month. In addition, when a proton beam is emitted by a gantry system, such as the gantry systems described in U.S. patent nos. 4917344 and 5039057, the target isocenter is often irradiated with the proton beam from a number of different angles.

To ensure accurate positioning of the patient relative to the proton treatment beam, the location of the target isocenter is initially determined relative to one or more markers within the patient. Typically, the markers are points on the patient's skeletal structure, and the location of the target isocenter is determined relative to these markers. One technique for determining the location of the isocenter of the target is to use a Digital Reconstructed Radiograph (DRR). In particular, a CT scan of the patient is performed using known techniques. Integration of this information into the DRR marks the target isocenter on the DRR, which contains diseased tissue, such as tumors and similar diseased tissue. The DRR file can then be integrated to display an image of the target isocenter from a variety of different perspectives.

Thus, when a patient is placed in a support, such as the support described in U.S. patent 4905267, and the support is placed on a treatment table in the gantry structure of a proton treatment apparatus, an X-ray source is placed in the path of the proton beam and an X-ray receiving device is positioned on the other side of the patient in the path of the proton beam. The X-ray source and X-ray receiving device thus generate an X-ray picture of an area in the patient's body that is placed on the proton beam path, which is the path of a proton beam that will be ejected from a nozzle of a proton beam emission system during treatment. The center of the proton beam in the radiograph can then be determined relative to pre-selected markers in the patient.

Comparison of the offset of the target isocenter in the DRR from a preselected marker with the offset of the X-ray beam center from the same marker in the radiograph indicates the direction in which the patient must be moved relative to the nozzle in order for the nozzle to be aligned with the target isocenter. Typically, this process is repeated until the patient is properly aligned with the nozzle of the proton emission system. In addition, the process must generally be repeated for each orientation of the nozzle relative to the patient as the nozzle is rotated about the gantry.

It will be appreciated that it is very time consuming to acquire radiographs of an area within a patient's body, as each must be washed. In addition, once the photographs are developed, the treating physician must measure the radiographs and compare the measurements to DRR images to determine how to move the patient. Thus, the patient must remain on the support for a long period of time, waiting for the treating physician to properly align. As a result, the treatment apparatus can only take very few patients due to the time required to perform the steps necessary to align the patients. Thus, there is a need for a system to more efficiently acquire images of the position of the patient relative to the nozzle in order to minimize the time required to determine the position of the patient relative to the nozzle and to move the patient for proper alignment of the patient.

In some applications of radiation therapy, a digitized image of an X-ray is acquired, which reduces film processing time. For example, U.S. patent No. 5039867 discloses a system for acquiring X-ray television images of a patient's body. However, this patent is designed to combine an ionized particle beam with a heavy particle beam and also to enhance the X-ray television image using an image intensifier. Such a system is less readily applicable to proton therapy because the use of an image intensifier can cause image distortion, thereby introducing unacceptable errors in the calculation of patient position. Since a proton beam has a much stronger injurious effect on the tissue, it is important that the position of the patient relative to the nozzle is determined very accurately. The errors introduced by the image intensifier when applied in a proton therapy system can result in too much inaccuracy.

Therefore, there is a need for a system that can acquire non-photographic images of the area of a patient's body that is placed in front of the nozzle of a proton emission system. Such a system should be able to accurately determine the area of the patient's body in front of the nozzle without introducing any errors into the determination. In addition, such a system should also be readily applicable to gantry systems in which the determination of the patient's body relative to the nozzle need not be governed by the angular orientation of the nozzle relative to the patient.

Disclosure of Invention

The proton therapy system of the present invention satisfies the aforementioned needs. The system includes a gantry, a nozzle disposed on the gantry and emitting a proton beam therefrom, a proton beam path feeding the proton beam to the nozzle, a movable X-ray source positionable in the proton beam path, and an X-ray receiving device disposed to receive X-rays generated by the X-ray source and passing through the patient. The X-ray source and X-ray receiving device are preferably mounted on the gantry so that an image of an area within the patient's body in the path of the proton beam can be generated using the X-ray source and X-ray receiving device regardless of the orientation of the nozzle relative to the patient. In addition, the X-ray receiving device preferably generates a digitized image of the region of the patient in front of the nozzle.

In one aspect of the invention, the system further includes a computer system having one or more standard indicating images and a plurality of markers within the patient. In the preferred embodiment, the standard prescription images are generated using Digitally Reconstructed Radiographs (DRRs), and the prescribing physician is able to locate the target isocenter with respect to preselected landmarks in the patient. The digitized radiograph generated by the image receiving device preferably shows the beam center superimposed on the patient's bone structure. The markers selected in the standard indicator image are preferably markers on the bone structure which are still visible in the radiograph. The system preferably allows the treating physician to identify the markers on the radiograph and then determine the spatial relationship between the beam center and the markers. The spatial relationship between the beam center and the marker is then compared to the spatial relationship between the target equiangular point and the same marker in the standard prescription image. The comparison produces a deviation value indicating how far the beam center is off the target isocenter in the patient. These values can then be used to move the patient so that the target isocenter is correctly aligned with the beam center.

Preferably, a standard prescription image is prepared for each gantry angle at which the beam is to be applied to the patient. Since the X-ray source and the X-ray receiving device are attached to the gantry, positioning images can be acquired no matter what new position the gantry is moved to, and deviation values can be calculated appropriately.

In another aspect of the invention, the X-ray receiving device is an apparatus having a phosphor screen that fluoresces when X-rays strike it, wherein photons generated by the phosphor screen are directed along a compact path to a cooled digital recording device. In one embodiment, the digital recording device is a CCD camera equipped with a thermoelectric cooler, thin (thined) CCD sensor with 512 x 512 pixels. The cooler carries thermal energy away, thereby reducing noise produced by the camera so that the camera can obtain radiographs of portions of the patient in the beam path from X-rays generated by a diagnostic quality X-ray tube operating in the energy range of 30kV to 150 kV.

Thus, the system of the present invention obtains an accurate digitized image of the portion of the patient's body in front of the nozzle, and calculates how far the beam center is offset from the target isocenter in the patient's body, thereby providing measurements that allow the patient to be repositioned relative to the beam nozzle. The foregoing and other objects and advantages of the invention will become more apparent in the following description, which proceeds with reference to the accompanying drawings.

Drawings

FIG. 1 is a block diagram of a digital imaging system in a preferred embodiment;

FIG. 2 is a front isometric view of a gantry for emitting a proton beam toward a patient, wherein the system of FIG. 1 is mounted on the gantry;

FIG. 3 is a front view of a movable X-ray apparatus in a counter-current direction along the emission line of the beam;

FIG. 4 is a detailed view of the image acquisition device of the digital imaging system shown in FIG. 1 mounted on a portion of the gantry shown in FIG. 2;

FIGS. 5A to 5E are detailed views further illustrating the image pickup apparatus shown in FIG. 4;

FIG. 6 is a flow chart illustrating operation of the digital imaging system shown in FIG. 1;

FIG. 7A is an illustration of a region within a patient's body having a target isocenter and a number of preselected markers;

figure 7B is an illustration of an X-ray of a portion of a patient's body in the beam path of the system shown in figure 1.

Detailed Description

Referring now to the drawings, in which like numerals indicate like parts throughout the several views, FIGS. FIG. 1 is a block diagram of a digital imaging system in a preferred embodiment the digital imaging system is implemented on a proton beam emission system 102 shown in FIG. 2. The proton beam emitting system 102 includes a gantry similar to the proton beam emitting system described in U.S. patent No. 4870287, which is incorporated herein by reference. In addition, reference is made to the structure of the portal described in U.S. patent nos. 4917344 and 5039057.

Referring now to fig. 1, the digital imaging system includes an X-ray tube 106 that can be positioned in the beam path to emit a beam of X-rays along the path of the proton beam, penetrating the region of the patient 108 positioned in front of the jet or nozzle 110 (fig. 2) of the beam emitting system 102. An image acquisition device 112 is disposed on the other side of the patient 108 along the path of the proton beam. The image acquisition device 112 includes a phosphor screen 114 that is designed to fluoresce in response to X-rays impinging thereon.

The photons generated by the phosphor screen are then directed along a compact path, as will be described in detail below with reference to fig. 5A through 5B, to a camera 116, which then generates a digitized image from the photons. The camera 116 is cooled to about-30 c in a manner to be described in more detail below to remove excess heat and thereby reduce noise in the image generated by the camera. The camera 116 is controlled by control electronics 120 and control and synchronization logic 122 such that the opening and closing of the shutter of the camera 116 corresponds to the state of the X-ray tube 106 emitting X-rays, and images are captured, which can be provided to a treatment room digital imaging display workstation 126 via a network 124.

The treatment room digital imaging display workstation 126 generates a display of the digital images captured by the camera 116 on the monitor 130. In addition, the treatment room digital imaging display workstation 126 also receives standard prescription images of the patient 108, which are also simultaneously displayed on the treatment room monitor 132.

As will be described in detail below with reference to FIGS. 6 and 7, the imaging system of the preferred embodiment acquires a digitized image of the area in the patient's body in the beam path for a given position of the gantry and displays the image on the monitor 130. The imaging system also receives a standard prescription image of the patient's body in which the target isocenter has been determined relative to various landmarks in the patient's body. The standard prescription image shows on monitor 132 the portion of the patient's body containing the isocenter of the target from the same perspective, i.e., from the same gantry angle as the X-ray image simultaneously displayed on monitor 130. The treating physician must then identify markers in the X-ray image on monitor 130 that correspond to the markers in the standard prescription image on monitor 132, and the spatial relationship between the beam center in the X-ray image on monitor 130 and the target isocenter displayed on monitor 132 is then determined by the treatment room digital imaging display workstation 126. The spatial relationship can then be used to move the patient in an appropriate manner to place the patient in front of the nozzle such that the beam path intersects the target isocenter.

Fig. 2 illustrates in detail a preferred embodiment of the beam-emitting system 102, which includes the imaging system. In particular, the beam delivery system 102 includes a gantry as described above that rotates about a center point 140. Beam emission system 102 includes a nozzle 110 from which a proton beam is emitted. Preferably, the nozzle is mounted on a ring (not shown) of the gantry such that the nozzle is rotatable about the center point 140, and the X-ray source is mounted on the beam emission system 102 so as to be rotatable about the center point 140. Similarly, image acquisition device 112 is also mounted on the ring opposite the X-ray source (fig. 3) so as to be centered on beam path 146 at any angular orientation of the beam emission system. In fig. 2, the gantry 104 is positioned such that the nozzle can emit a beam along a beam path 146 corresponding to an x-axis 151. It will be appreciated, however, that the nozzle 110 is movable such that the beam path 146 may be in a different direction, but always intersect the center point 140. Beam emission system 102 also includes a treatment table 150 that is movable along a z-axis 152 and the X-ray source.

The patient 108 is placed in a chamber 149 such as that disclosed in U.S. patent No. 4905267, which is incorporated herein by reference. The chamber 149 and the patient 108 are then placed on the treatment table 150. the chamber 149 is movable relative to the treatment table 150 along an x-axis 151 and y-axis and z-axis extending out of the plane of the paper in FIG. 2, and may be rotationally aligned. The movement of the capsule over the treatment table can be achieved in any of a number of known ways, such as by placing the capsule in a cradle connected to the treatment table, the cradle having drive means for moving the capsule. One possible system for moving the capsule after determining the deviation may be the system currently being used at the university of Loma Linda medical center of Loma Linda, california.

Generally, the chamber 149 is designed such that when a patient 108 is placed into the chamber 149, the orientation of the patient relative to the chamber 149 is substantially fixed. In this way, each time the patient 108 is placed into the compartment 149, the orientation of the patient relative to the compartment 149 is substantially the same. The chamber 149 is then placed on the treatment table 150 with the chamber and patient in front of the jet 110 so that the target isocenter in the patient is centered on the beam emanating from the jet 110.

Fig. 3 is a front view of the X-ray source 106 of the digital imaging system. As shown, the X-ray source 106 is mounted on the beam emission system 102 so that it can be positioned in the beam path 146 and then moved away from the beam path 146. In this way, the X-ray source can emit X-rays along the beam path 146, which then pass through the body of the patient 108 in a compartment 149 placed on the treatment table 150 to the image acquisition device 112. The X-ray source 106 is mounted on a movable slide 134 that is slidable along two guide rails 135a and 135 b. The treatment room control system (not shown) activates a rotation motor assembly 136 as the treating physician initiates the X-ray imaging procedure, in a manner to be described in detail below. The rotational motor arrangement is used to position the sled 134, and thus the X-ray source 106, along the beam path 146 such that when X-rays are emitted by the X-ray source 106, the X-rays propagate along the beam path 146. In the preferred embodiment, the X-ray source 106 is comprised of a 10-150kVA X-ray tube manufactured by Varian Inc. of Palo Alto, Calif., a B150 v tube having an A192 tube mounted therein. The X-ray generating device and the control line are constituted by a general X-ray generating device of model No. edec 30 produced by electric International. The generating device and controller can cause the rotational motor device 136 to move the sled 134 and the X-ray source 106 into the beam path 146 and then cause the X-ray source 106 to generate an X-ray imaging beam. Once the imaging process is complete, the sled 134 and the X-ray source 106 are moved away from the beam path 146 to irradiate the target isocenter with a treatment beam.

Fig. 4 is a view of the image capture device 112 as mounted on one or more shield plates 144. The shield plate is mounted on a gantry of the beam emission system 102. Specifically, the image capture device 112 is placed in a rectangular parallelepiped box 160, which is then mounted to the inner shield 144 of the gantry using mounting screws 162a and 162 b. As shown in FIG. 2, the image acquisition device is fixed to the gantry so that it can be positioned in the beam path 146 regardless of the rotational position of the gantry. Thus, when the X-ray source 106 is positioned in the beam path and generates X-rays, the image acquisition device 112 receives the X-rays after they have traveled along the beam path 146 and through the patient 108.

In this way, the X-ray source 106 and the image acquisition device 112 are capable of generating images of the portion of the patient 108 positioned in front of the nozzle of the beam emission system 102 in each direction of the gantry 104. It will be appreciated that the image acquisition apparatus 112 must be mounted on the gantry ring 114 such that the image acquisition apparatus 112 remains in the beam path 146 throughout the range of motion of the gantry 104. Thus, the brackets 162a and 162b, as well as the cassette 160, are made of a material that is sufficiently rigid such that the image capture device 112 does not move relative to the nozzle 110 throughout the range of motion of the gantry.

Fig. 5A to 5E illustrate the image pickup device 112 in detail. Specifically, fig. 5A shows the cassette 160 of the image capture device 112 with a portion of the outer wall 170 of the cassette removed to expose the components placed inside. In the preferred embodiment, the box is constructed of a frame 172 and panels bolted to the frame so that the interior of the box is dark. As will be appreciated from the following description, image acquisition device 112 must generate accurate, distortion-free digitized images of the X-rays generated by X-ray source 106 for the portion of patient 108 located in front of nozzle 110, i.e., along beam path 146. Thus, the cassette 160 must be manufactured such that no additional light penetrates into it other than the X-ray generated light impinging on the image capture device 112 in a manner to be described below.

Fig. 5B and 5C illustrate a side view and a front side 176, respectively, of the image capture cartridge 160. The front surface 176 is the side that faces the X-ray source 106 and is perpendicular to the beam path 146 (fig. 2) when the image acquisition device 112 is mounted to the gantry 104 in the manner shown in fig. 2. On the left side of the front 176 of the cartridge 160, a square aperture or entrance is formed (fig. 5C). In the preferred embodiment, a protective cover 184, a radiographic grid slot 186, and a cassette slot 190 are provided in front of the entrance 182. In addition, immediately after the X-ray cassette slot 190, immediately adjacent to the entrance 182 of the cassette 160, there is a phosphor screen assembly 192 (fig. 5A).

As shown in FIG. 5C, three cross-hairs 200a-200C are formed in the protective cover and intersect at a point, i.e., the center of the entrance 182. As will be described below, the cross-hairs 200a-200c provide the treating physician with a visual indication of the location of the center of the X-ray propagating along the beam path 146 relative to markers within the patient 108. Thus, the intersection of the cross-hairs 200a-200c is preferably located at the very center of the beam path 146. This requires precise positioning of the cartridge 160 of the image capture device 112 relative to the nozzle 10.

In the preferred embodiment, the radiographic grid slot 186 and the radiographic cassette slot 190 each receive an radiographic grid 187 and an X-ray cassette 191 (FIG. 5A). In this way, patient alignment can also be accomplished using existing techniques for obtaining radiographs of the patient's position. Thus, the patient alignment system in the preferred embodiment allows for both the use of digitized images and the use of photographic images for patient alignment.

In the event that it is desired to acquire a digitized image of the patient, the X-ray cassette 191 (FIG. 5A) is removed from its cassette so that X-rays emitted from the X-ray source 106 impinge upon the phosphor screen arrangement 192, which causes the phosphor screen arrangement 192 to generate photons at the location where they are impinged by the X-rays. These photons travel generally inwardly in the direction of arrow 202 (fig. 5A) through one or more baffles 204, into the box 160, toward a second mirror 206. In the preferred embodiment, the luminescent screen assembly 192 is formed of a Kodak Lanax rapid enhancement screen, product number 1476175, made of 14 "x 14" square gadolinium dioxide (Gd)₂O₂S: tb) that generates photons when X-rays strike the surface of phosphor screen 192.

The photons strike the second mirror 206 and are reflected in the direction of arrow 210 to a first mirror 212. The photons are then reflected from the first mirror 212 in the direction of arrow 214 to a lens 216 of the camera 116. As shown in FIG. 5A, photons generated by X-rays striking phosphor screen assembly 192 travel along a zigzag path 203 to camera 116. The zigzag path 203 allows the cassette 160 to be compact enough to be mounted on the gantry 104. In the preferred embodiment, the dimensions of the cassette 160 are approximately 32 inches long, 32 inches wide and 14 inches deep.

The phosphor screen arrangement 192 generates photons that are sufficient to represent the X-rays impinging on the front surface of the phosphor screen 192, which are then directed to a lens 216. Preferably, the second mirror is an 1/4 wavelength antireflective mirror with an aluminum protective film mounted in the box 160 at an angle of 25.5490 ° to the photon path. In the preferred embodiment, the second mirror 206 is mounted in a fixed mount that maintains the angle relative to the beam path 146 throughout the range of motion of the gantry 104. The first mirror 212 is a mirror with an arcuate front surface mounted on a two-axis gimbal (gimble) that allows + -4 deg. adjustment in each axis. The first mirror 212 is oriented such that light reflected from the second mirror 206 is substantially totally reflected into the lens 216 of the camera 116.

It will be appreciated that control of reflected light in the cassette 160 is an important design issue because the intensity of light produced by X-rays striking the front surface of the phosphor screen 192 is very weak. It is also known that the scattered light produced by the luminescent screen arrangement 192 is generally transmitted in all directions. In the preferred embodiment, this control of scattered light is achieved by two mechanisms.

The first mechanism is to make the inner surface of the box 160 only minimally reflective. Specifically, in the preferred embodiment, the interior of the cassette 160 and most of the components therein are grit blasted with a glass frit to form a matte finish, and then anodized in black. In addition, the baffle 204 also traps the scattered light, causing it to be reflected multiple times before it reaches the camera lens, thereby reducing its intensity. Although only two baffles 204 are shown in the preferred embodiment, it is understood that multiple baffles may be provided in cassette 160 to further limit the adverse effects of scattered light on any subsequent images generated by image capture device 112. The baffle 204 is positioned such that substantially all light incident on the lens 216 of the camera 116 travels along a path parallel to the optimal path 203 of light in the cassette 160. Thus, light rays emanating from the phosphor screen arrangement 192 at an angle to the path 203 are preferably absorbed or reflected multiple times so as not to reach the lens 216. In this manner, noise in the resulting digitized image can be reduced.

The camera 116 is preferably mounted on a mounting means within the image capture device's cassette 160 that allows for adjustment about a horizontal axis, a vertical axis, and a longitudinal axis. In addition, the fixture also allows angular adjustment along the optical axis 214, which is defined as the path of the photons from the mirror to the lens. In this manner, the camera may be adjusted to an optimal position to receive the image produced by the X-rays impinging on the phosphor screen assembly 192. In addition, camera 116 is configured to form an image from the low level light generated by the X-rays impinging on phosphor screen arrangement 192.

In the preferred embodiment, the camera is a CCD camera with 512 by 512 active pixels with a duty cycle of 100% and an objective field of view of 355.6mm by 355.6 mm. Wherein the pixel size is 0.69mm square. Preferably, the camera is a thermoelectric cooled CCD type camera in which the heat generated by the TEC is carried away in a liquid closed cycle. In the preferred embodiment, the camera is a research grade CCD camera model MCD1000S, available from Spectral Source, Inc. of Westlake Village, Calif. Lens 216 is preferably a 50mm focal length f.95 lens.

As shown in fig. 5D and 5E, the camera 116 is water cooled by a pair of cooling tubes 230 that supply water to the camera 116 and carry heated water away from the camera 116. The cooling tube 230 in the preferred embodiment is connected to a water supply (not shown) that is a component of the gantry apparatus 104. The water cooling system cools the CCD camera to maintain it at a temperature of-30 ℃. The cooling of the camera 116 ensures that the camera 116 is able to generate a visible digitized image of an X-ray picture corresponding to the portion of the patient 108 in front of the nozzle 110 of the beam emitting system 102.

Figure 6 is a flow chart illustrating the operation of the digital imaging system in determining the position of the patient 108 relative to the nozzle 110 of the beam emitting system 102, in particular, starting from an initial state 400, at stage 402, a prescription is prescribed for the patient in a known technique. Typically, the prescription is based on a physician's judgment of the location, characteristics and size of the part of the patient to be treated. For example, if the treatment is to radiation treat a tumor, the prescription may be based on the size, characteristics, and location of the tumor. The prescription includes such information: the dose of radiation to be delivered to the tumor, the frequency of the radiation therapy, and the angle at which the dose of radiation is delivered from the gantry to the patient. The prescription is typically made using known dosimetry techniques.

Additionally, at stage 404, a Digitally Reconstructed Radiograph (DRR) of the patient is formed, again using known techniques. Specifically, in the preferred embodiment, the DRR file is created using a DRR application using techniques described in George Shell et al, entitled "calculation of digitally reconstructed radiographs for radiation therapy," which is incorporated herein by reference, and which is originally published in International Journal of RadiationOncology Biology Physics, Vol.18 pp. 651-658, 1989. The technology was developed by university of north carolina on Sun Spark 5 workstation. The DRR is obtained by performing a series of CT scans of a region of diseased tissue of the patient, wherein from the CT scans DRR files can be formed which can show the region of the patient's body from any given perspective. The creation of a DRR file showing diseased tissue, such as a tumor, located at the target isocenter within a patient is a well-known radiation therapy planning procedure ix. Thus, a standard prescription image 500 (FIG. 7A) may be generated for a region within the patient surrounding the target isocenter 504 from the perspective of a given gantry angle at stage 406. An example of a standard pointing image 500 is shown in FIG. 7A, the image 500 in FIG. 7A being greatly simplified for illustrative purposes.

Figure 7A shows an image of a target isocenter 504 in a region of a patient 108 on an image 500. In addition, there are two rigid structures or markers 506 and 508 on the adjacent bone structure 510 selected by the prescribing physician. As shown in fig. 7A, a pair of imaginary cross-hairs 520a and 520b are formed to be aligned with the target isocenter 504. The distance of the markers 506 and 508 relative to the imaginary cross-hairs 520a and 520b constitutes a reference for aligning the patient 108 in a manner to be described below. Of course, those skilled in the art will appreciate that the criteria indicate that the images in image 500 have been greatly simplified for clarity. In an actual standard prescription image, the prescribing physician will select a series of landmarks on the patient's bone structure and will often generate standard prescription images from two different perspectives to ensure that the patient is accurately aligned in all three dimensions.

After generating the standard prescription image 500 from the DRR data, the physician then selects markers 506 and 508 on the standard prescription image at stage 410 and uses these markers to determine the coordinates of the target isocenter relative to the markers 506, 508. Preferably, the treating physician utilizes the workstation 126 to select the markers, which are typically points on the patient's skeletal system that are visible in the subsequently generated digitized X-ray images of the patient 108. The target isocenter 504 corresponds to a diseased tissue region, and the target isocenter 504 may be identified on the standard prescription image 500.

As shown in FIG. 7A, the position of the marker relative to selected points on both imaginary cross-hairs 520a and 520b can be determined. The distance between the selected point on the cross-hair and the target isocenter 504 can also be determined. Specifically, the distance of each marker from the crossing filaments 520a and 520b in a direction perpendicular to the crossing filaments, i.e., the X and Y coordinates of the marker with respect to the isocenter of the target, may be first determined. Thus, the spatial relationship between the markers 506, 508 and the isocenter of the target can be determined and defined as X and Y coordinates, such that the coordinates of the marker 506 are X1, Y1, and the coordinates of the marker 508 are X2, Y2.

After the standard prescription image 500 of the patient 108 is formed, the markers are selected and the vector coordinates of the target isocenter with respect to the markers are determined, this information can then be provided to a digital imaging system and used in subsequent treatment of the patient 108. Specifically, at stage 412, the patient may be placed on the treatment table 150 (fig. 2), and then the gantry 104 may be rotated to a desired treatment angle. As previously mentioned, the patient 108 is preferably substantially immobilized in the chamber, which is fixed to the treatment table 150 in a fixed orientation relative to the nozzle 110 of the beam delivery system 102. Typically, the patient is secured in a chamber, which is secured to the treatment table 150 such that the chamber is generally aligned with the nozzle 110 of the beam delivery system 102. Subsequently, at stage 414, the X-ray source 106 is placed in the beam path 146 in the manner described with reference to FIG. 3, and then at stage 416, the X-ray source is activated to emit X-rays from the nozzle 110 of the beam emission system 102 through the portion of the patient's body just before the nozzle 110 to the image acquisition device 112. The result is an image 500 'of the portion of the patient's body just before the nozzle 110 of the beam emitting system 102 generated by the workstation 126 or the display device 130 (FIG. 1) and displayed.

An example 500' of an acquired X-ray image is shown in fig. 7B. The image is primarily of the bone structure 510' in the region of the patient 108 in front of the nozzle 110, overlaid with the cross hairs 200a-200C (FIG. 5C). It will be appreciated that the cross hairs will block X-rays directed to the luminescent screen assembly 192 (FIGS. 5A and 5B), thereby resulting in fewer photons being generated in the cross-hair region. Preferably, the cross-hairs 200a-200c are arranged so as to cross the direct geographic center (direct geographic center) of the beam path 146. In addition, in practice, a second set of cross hairs may be provided in the beam path adjacent to the nozzle 110 of the beam emitting system 102, so that the two sets of cross hairs may be used for alignment verification. For example, if the two sets of cross-hairs are misaligned, this indicates that the image acquisition system 112 is misaligned with the beam path 146, thereby informing the operator of the gantry system 102 to take the necessary corrective action.

After the image acquisition system 112 acquires an X-ray image 500 'of the patient 108 located on the beam path 146, the image 500' is fed to the treatment room digital imaging display workstation 126 (fig. 1) and then displayed on the treatment room image display monitor 130. Additionally, at stage 420, a standard prescription image 500 is also simultaneously displayed on the monitor 132. This enables the treating physician to simultaneously view the standard prescription image 500 of FIG. 7A and the X-ray image 500' of FIG. 7B. The treating physician may then select markers 506 ' and 508 ' on the X-ray image 500 ' that correspond to the markers 506 and 508 on the standard prescription image 500 at stage 422. Preferably, the treating physician selects the image using a mouse and clicks on the markers displayed in the X-ray image.

After selecting the markers 506 ' and 508 ' on the X-ray image 500 ' that correspond to the markers 506 and 508 on the standard designation image 500, the workstation 126 determines the coordinates (X1, Y1) and (X2, Y2), respectively, of the markers 506 ' and 508 ' relative to the beam center 512 on the X-ray image at stage 424. As previously described, the beam path center 512 is indicated by the intersection of the cross hairs 200a-200 c. The third cross hair 200c may be similarly used. By comparing the coordinate values (X1, Y1) and (X2, Y2) determined for the standard index image with the coordinate values (X1 ', Y1') and (X2 ', Y2'), the deviation between the target isocenter 504 and the beam path center 512 can be determined.

Then, at decision stage 430, the computer in the display workstation 126 determines whether the beam center 512 is aligned with the isocenter 504. If the beam center 512 is aligned with the isocenter 504, the digital imaging system proceeds to stage 432 where the patient 108 can be treated with treatment beams by initiating a treatment procedure. Typically, a treatment procedure will require that the X-ray source 106 be removed from the beam path, a proton beam be requested from the beam source, and the proton beam be directed to the patient after appropriate calibration and verification.

If the beam center 512 in the X-ray image 500' is not aligned with the isocenter 504 in the standard prescription image 500, the digital imaging system determines at stage 434 the direction in which the patient needs to be moved to align the isocenter 504 with the beam path center 512. In the preferred embodiment, the direction and magnitude of patient movement is determined using least squares approximation between the coordinates of the isocenter 504 with respect to the markers 506, 508, and the coordinates of the center point 512 of the X-ray image with respect to the markers 506 ', 508'. The digital imaging system then moves the patient 108 in the direction of the deviation at stage 436. In the preferred embodiment, the treatment table 150 is automated and can be moved in response to commands provided by the treating physician. Thus, the treatment practitioner can move the patient 108 held in the chamber 149 to a new position by simply entering the movement values determined at stage 434. The X-ray source is then restarted at stage 416, and the process of steps 416 through 430 is repeated until the isocenter 504 is aligned within a tolerable error range from the beam path center 512.

Although in the preferred embodiment alignment is performed using matching markers selected by the treating physician, other techniques may be used to compare the standard indicator image and the X-ray image for alignment purposes. In particular, shape recognition software may be used, which software may recognize the markers in the X-ray image, so that point markers do not have to be specifically pointed by the treating physician. Additionally, curve recognition software may also be used, in which case the target isocenter may be determined relative to a bone structure or landmark having a particular curve profile. In this way, the same curved structures can be identified in the X-ray image by the computer, so that the position of the beam path center can be determined with respect to the same bone structure with a specific curved profile. This information can then be used to determine the deviation between the beam center and the target isocenter for subsequent adjustment of the patient position. Thus, it will be appreciated by those skilled in the art that the markers used to determine the deviation between the beam center and the target isocenter need not be specified by the prescribing physician, but can be determined by computer software, and that the markers need not be constituted by specific points on the bone structure, but can be the entire bone structure, such as curved bone or the like.

Thus, the digital imaging system of the preferred embodiment makes alignment of the patient with the beam nozzle more efficient. Specifically, the treating physician need only place the patient in the chamber in front of the nozzle and repeatedly determine the relative position between the beam path and the target isocenter in the patient with respect to the selected markers. This eliminates the need to generate an X-ray picture of the part of the patient's body before the nozzle and allows the deviation between the beam path centre and the target isocenter to be calculated automatically. Thus, patient alignment is simplified and becomes more efficient, thereby allowing for more efficient use of the treatment apparatus.

While there have been shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their use, may be made by those skilled in the art without departing from the spirit of the invention. Accordingly, the scope of the invention should not be limited by the foregoing description, but should be defined by the appended claims.

Claims (34)

1. An imaging system for use in a proton beam therapy system including a proton source and a beam delivery system having a nozzle mounted on a gantry such that said proton beam is directed at a patient from a range of angles, wherein said proton beam therapy system receives standardized indicative images of an area of the patient to be treated, said imaging system comprising:

an imaging beam source mounted on said beam emitting system, wherein said imaging beam source is movable between a plurality of positions, wherein said imaging beam source can emit an imaging beam along a beam path toward a first side of said patient, said imaging beam source being movable away from said beam path;

an imaging beam receiving means mounted on said gantry such that said imaging beam receiving means is aligned with the center of the beam path through a range of angles of gantry orientation, wherein said receiving means receives said imaging beam after said imaging beam has traversed a region of the patient positioned in said beam path;

an image acquisition device in close proximity to said imaging beam receiving means, wherein said image acquisition device receives signals from said imaging beam receiving means and generates a patient orientation image of a region in the patient's body in the beam path; and

a control device for receiving the standard prescription image and the patient orientation image, wherein the control device is designed such that one or more rigid structures can be approximately assigned to the standard prescription image in order to define the relative position of the isocenter to be treated in the patient with respect to the one or more rigid structures, wherein the control device is further designed such that one or more rigid structures can be approximately assigned to the patient orientation image in order to be able to determine the approximate relative position of the beam path with respect to the one or more rigid structures, wherein the control device determines the relative movement which the patient and the gantry need to perform with the use of the isocenter and the approximate relative position of the beam path with respect to the one or more rigid structures in order to position the beam path with respect to the one or more rigid structures, corresponding to the location of the isocenter relative to the one or more rigid structures.

2. The system according to claim 1, wherein the imaging beam source is comprised of an X-ray source mounted for movement transverse to the proton beam path direction.

3. The system of claim 2 wherein said imaging beam receiving means is comprised of a phosphor screen disposed in said beam path, said phosphor screen producing photons when X-rays impinge upon said phosphor screen.

4. The system of claim 3, wherein the image capture device is comprised of a CCD camera that receives the photons produced by the phosphor screen to generate the patient orientation image.

5. The system of claim 4, wherein the CCD camera is water cooled to remove unwanted noise from the patient orientation image.

6. The system of claim 5, wherein said receiving means and said CCD camera are disposed in a cassette, wherein said receiving means is disposed in an aperture of said cassette, said cassette defining a path for said photons generated by said receiving means for directing said photons toward said CCD camera for said beam path.

7. The system of claim 6, wherein the box includes two mirrors such that photons emitted from the phosphor screen are directed to one of the mirrors in a first direction, reflected to the second mirror in a second direction, and reflected to the CCD camera in a third direction substantially parallel to the first direction.

8. The system of claim 7, wherein the cassette includes one or more baffles to prevent at least a portion of the photons having a directional component transverse to the path direction from reaching the CCD camera.

9. The system of claim 8, wherein said X-ray source is comprised of a diagnostic quality X-ray tube operating in the energy range of 30kV-150kV, said phosphor screen is comprised of square gadolinium sulfur dioxide, and said CCD camera comprises a 512X 512 pixel thin CCD sensor and comprises a 50mm focal length f.95 lens.

10. The system of claim 9, wherein the CCD camera receives the photons from the phosphor screen directly from the path such that the patient orientation image is not substantially distorted by the enhancement.

11. The system of claim 4, further comprising a pair of cross hairs mounted on the receiving device to be aligned with the beam path, wherein the cross hairs block X-rays from the X-ray source such that fewer photons are generated by the phosphor screen in the cross-hair region, thereby causing an image of the cross hairs to be visualized in the patient-oriented image.

12. The system of claim 1, further comprising:

a first monitor for receiving the signal from the control device and displaying the standard indicating image; and

a second monitor receiving signals from the control device and displaying the patient orientation image, wherein the treating physician can manipulate the control device to designate the one or more rigid structures on the patient orientation image.

13. The system of claim 1, wherein the control device performs a least squares approximation to determine deviations of the beam path center and the isocenter from the one or more rigid structures, wherein the one or more rigid structures are markers on the patient's skeletal structure.

14. An imaging system for use in a proton beam therapy system including a proton source and a beam delivery system having a nozzle mounted on a gantry such that an X-ray beam is directed at a patient from a range of angles, wherein said imaging system receives standardized index images of an area of the patient to be treated, said imaging system comprising:

an X-ray source mounted on said beam emission system, wherein said X-ray source is movable between a first position in which said X-ray source can emit an X-ray beam along a beam path toward a first side of said patient and a second position in which said X-ray source is moved away from said beam path to allow a proton beam to pass from said beam path;

an X-ray beam receiving device mounted on said gantry such that said X-ray beam receiving device is aligned with the center of the beam path through a range of angles of gantry orientation, wherein said X-ray beam receiving device receives said X-ray beam after said X-ray beam has traversed a region of the patient positioned in said beam path and generates a photon image corresponding to a portion of the patient's body in said beam path;

an image acquisition device receiving photon images directly from the X-ray beam receiving arrangement to generate a patient oriented image of a region of the patient's body in the beam path such that the patient oriented image is substantially undistorted by the enhancement; and

a control device for receiving the standard prescription image and the patient orientation image, wherein the control device is designed such that approximately one or more rigid structures can be assigned on the standard prescription image in order to define the relative position of the isocenter to be treated in the patient with respect to the one or more rigid structures, wherein the control device is further designed such that approximately one or more rigid structures can be assigned on the patient orientation image in order to be able to determine the approximate relative position of the beam path with respect to the one or more rigid structures, wherein the control device determines the required movement of the patient with the aid of the isocenter and the approximate relative position of the beam path with respect to the one or more rigid structures in order to position the beam path with respect to the one or more rigid structures, corresponding to the location of the isocenter relative to the one or more rigid structures.

15. The system of claim 14, further comprising a pair of cross hairs mounted on said receiving means so as to be aligned with said beam path, wherein said cross hairs block X-rays from said X-ray source such that fewer photons are generated by said X-ray receiving means in said cross hairs region, thereby causing an image of said cross hairs to be visualized in said patient orientation image.

16. The system of claim 14, wherein the control device performs a least squares approximation using the relative positions of the isocenter and the beam path center with respect to the one or more markers to determine the direction and magnitude of movement of the patient relative to the beam path required to align the isocenter with the beam path center.

17. The system of claim 14, further comprising:

a first monitor for receiving the signal from the control device and displaying the standard indicating image; and

a second monitor receiving signals from the control device and displaying the patient orientation image, wherein the treating physician can manipulate the control device to designate the one or more rigid structures on the patient orientation image.

18. The system of claim 14 wherein said X-ray receiving means is comprised of a phosphor screen disposed in the beam path, the phosphor screen producing photons when X-rays impinge upon the phosphor screen.

19. The system of claim 18, wherein the image capture device is comprised of a CCD camera that receives the photons produced by the phosphor screen to generate the patient orientation image.

20. The system of claim 19, wherein the CCD camera is water cooled to remove unwanted noise from the patient orientation image.

21. The system of claim 20, wherein said receiving means and said CCD camera are disposed in a cassette, wherein said receiving means is disposed in an aperture of said cassette, said cassette defining a path for said photons generated by said receiving means for directing said photons to said CCD camera in alignment with said beam path.

22. The system of claim 21, wherein the box includes two mirrors such that photons emitted from the phosphor screen are directed to one of the mirrors in a first direction, reflected to a second mirror in a second direction, and reflected to the CCD camera in a third direction substantially parallel to the first direction.

23. The system of claim 22, wherein the cassette includes one or more baffles to prevent photons having a directional component transverse to the path direction from reaching the CCD camera.

24. The system of claim 23, wherein said X-ray source is comprised of a diagnostic quality X-ray tube operating in the energy range of 30kV-150kV, said phosphor screen is comprised of square gadolinium dioxide, and said CCD camera comprises a 512X 512 pixel thin CCD sensor and comprises a 50mm focal length f.95 lens.

25. A method of aligning a patient in a proton beam therapy system such that the beam path center is aligned with an isocenter in the patient, comprising the steps of:

acquiring a standard prescription image of the patient for the desired beam orientation, the standard prescription image being stored in a computer system;

placing the patient on a treatment table with a region of the patient's body containing the isocenter in front of the nozzle;

emitting an imaging beam along a treatment beam path, the imaging beam directed toward a region of the patient's body disposed in front of the nozzle;

receiving the imaging beam after the imaging beam has penetrated a region within the patient, thereby acquiring a patient-oriented image of a region within the patient disposed in the beam path and providing the image to the computer system;

designating, with the computer system, the one or more markers on the standard indication image;

designating, with the computer system, the one or more markers on the patient-oriented image, wherein the one or more markers designated on the standard-indicating image and the patient-oriented image correspond to a same point on the patient's bone;

determining a relative position of the treatment beam center with respect to the one or more markers specified on the patient orientation image;

determining, with the computer system, a deviation between the isocenter relative to the one or more markers in a standard prescription image and the beam center relative to the one or more markers in a patient orientation image; and

the distance and direction that the patient has to move is determined such that the position of the beam center relative to the one or more markers coincides with the position of the isocenter relative to the one or more markers.

26. The method of claim 25, wherein the step of transmitting an imaging beam along the therapy beam path comprises the steps of:

placing an X-ray source in the treatment beam path; and

causing the X-ray source to emit X-rays along the treatment beam path.

27. The method of claim 26, wherein the step of receiving the imaging beam is such that: receiving the X-rays after the X-rays propagate along the treatment beam path and through the patient.

28. The method of claim 27, wherein the step of receiving an imaging beam and acquiring a patient orientation image comprises the steps of:

placing a phosphor screen in the beam path such that photons are generated by the X-ray beam when it impinges the phosphor screen;

the photons are directed along a compact path to a CCD camera.

29. The method of claim 28, further comprising the step of: a pair of cross hairs is arranged so as to be aligned with the centre of the treatment beam path so that an image of the cross hairs is visualized at a point on the patient orientation image corresponding to the centre of the treatment beam path.

30. The method of claim 25, wherein the step of selecting one or more markers comprises the steps of:

displaying a digitized image of the standard indicating image on a display device;

manipulating a user input device to move to a marker on the patient's skeletal structure displayed on the display device;

manipulating the user input device to select the marker;

displaying a digitized image of the patient orientation image on a display device;

manipulating a user input device to move to a marker on the patient's skeletal structure displayed on the display device;

manipulating the user input device to select the marker;

31. the method of claim 30, further comprising the steps of:

calculating the relative position between a selected marker in a standard indicating image and an isocenter in the standard indicating image; and

the relative position of a selected marker of the patient orientation image to the center of the beam path is calculated.

32. The method of claim 25, wherein the step of determining the distance and direction the patient has to move is such that: a least squares 2 approximation is performed between the relative position of the isocenter with respect to the one or more markers in the standard-indicative image and the relative position of the beam path center with respect to the one or more markers.

33. A therapeutic imaging system for use in a therapeutic beam therapy system comprising a therapeutic beam source and a beam emitting system with a nozzle, said nozzle being designed to provide said therapeutic beam from a range of different angles, wherein said therapeutic imaging system comprises:

an X-ray source mounted on said beam emission system, wherein said X-ray source is movable between a first position in which said X-ray source emits an X-ray beam along a treatment beam path toward a first side of said patient and a second position in which said X-ray source is moved away from said treatment beam path to allow said treatment beam to pass from said treatment path;

a phosphor screen positioned to be aligned with a center of the treatment beam path, wherein the phosphor screen receives the X-ray beam and generates a photon image therefrom after the X-ray beam passes through a region of a patient positioned in the treatment beam path;

a digital camera receiving photon images directly from the phosphor screen to generate a patient-oriented image of a region of the patient's body in the path of the treatment beam such that the patient-oriented image is substantially undistorted by the enhancement; and

a control device for receiving a standard prescription image of a region of a patient to be treated and the patient orientation image, wherein the control device is designed such that one or several rigid structures can be assigned on the standard prescription image in order to determine the relative position of the isocenter to be treated in the patient with respect to the one or more rigid structures, and such that one or several rigid structures can be assigned on the patient orientation image in order to be able to determine the relative position of the beam path center with respect to the one or more rigid structures, wherein the control device determines the relative movement that the patient and the nozzle need to perform with the isocenter and the relative position of the beam path center with respect to the one or more rigid structures in order to position the beam path center with respect to the one or more rigid structures, corresponding to the location of the isocenter relative to the one or more rigid structures.

34. The system of claim 33 wherein said therapeutic imaging system is used with a proton beam therapy system having a proton source, a beam emitting system with a nozzle mounted on a gantry such that said X-ray beam is directed toward a patient from a range of angles, wherein said therapeutic imaging system is capable of generating said patient orientation images at a range of orientation orientations of said gantry.