JP2010253049A - Radiotherapy apparatus and radiation fluoroscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To support a therapist so as to be capable of easily positioning a subject and reconfirming an affected region. <P>SOLUTION: Scintillator plates 5b and 5c generate fluorescence respectively according to predetermined absorption energy distribution by therapeutic radiation N. A light shielding plate 5d shields the fluorescence generated by the scintillator plates 5b and 5c, in respectively different directions. Cameras 5e and 5f respectively captures an image of the fluorescence generated by the scintillator plates 5b and 5c from respectively directions not shielded. Then, using the image captured by the cameras 5e and 5f, a controller generates images separated by each biological tissue included in the affected region being an area subjected to therapy. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radiotherapy apparatus and a radioscopic apparatus.

  Conventionally, in a treatment using a radiotherapy apparatus, a fluoroscopic image or CT (Computed) using X-rays in an energy region (for example, several tens of keV to several hundreds of keV) with high contrast of a living tissue (for example, bone, muscle, fat, etc.). Tomography) The treatment plan was based on the image. Furthermore, in recent years, from the viewpoint of ensuring the safety of treatment, not only the mechanical alignment of the subject and the irradiation field, but also the reconfirmation of the affected area by X-ray fluoroscopy images taken from the same viewpoint as the center of the therapeutic radiation source. Has come to be done.

  In order to perform such alignment and reconfirmation, in recent years, a high energy fluoroscopic device called an EPID (Electronic Portal Imaging Device) has begun to be used. The EPID is an apparatus that captures a fluoroscopic image using therapeutic radiation having energy of several MeV as a radiation source. For such EPID, a “planar X-ray detector” or “scintillator plate, lens system and imaging sensor” using a semiconductor is used, but the latter is usually mounted from the viewpoint of radiation resistance.

  FIG. 11 is a diagram illustrating an example of a conventional EPID. For example, as shown in FIG. 11, as a scintillator plate, for example, one “metal / phosphorus scintillation detector” is provided, and after reflecting the fluorescent image with a mirror, the reflected fluorescent image is photographed with a “video camera”. EPID of the mechanism to perform is known (see, for example, Patent Document 1).

JP 2001-238969 A

  However, in the conventional technique described above, there is a problem that it is difficult for the operator to perform alignment of the subject and reconfirmation of the affected area as described below.

  As described above, conventional EPID uses therapeutic radiation having an energy of several MeV. However, it is known that with a radiation of several MeV, the contrast of a fluoroscopic image to be taken becomes low.

  FIG. 12 is a diagram illustrating a mass energy absorption coefficient with respect to photon energy for each living tissue. As shown in FIG. 12, when the photon energy is several tens keV to several hundreds keV, the difference in mass energy absorption coefficient among bones, muscles, and fats is relatively large, but the difference is small at several MeV. Here, it is known that the mass energy absorption coefficient and the mass attenuation coefficient are in a monotonically increasing relationship. Therefore, regarding the mass attenuation coefficient, when the photon energy is several tens keV to several hundreds keV, the difference is relatively large among bones, muscles, and fats, and the difference is small at several MeV. Therefore, when imaging is performed using X-rays, the contrast is high when the photon energy is several tens keV to several hundreds keV, and the contrast is low when the photon energy is several MeV.

  For example, the above-described alignment of the subject and reconfirmation of the affected area are performed by comparing a CT image using X-rays of several tens of keV to several hundreds of keV with a fluoroscopic image taken by EPID. FIG. 13 is a diagram showing a CT image using X-rays of several tens keV to several hundreds keV and an image photographed by EPID. In FIG. 13, the upper image is a CT image, and the lower image is a fluoroscopic image taken by a conventional EPID. As shown in FIG. 13, the image quality is very different between the CT image and the EPID image. For this reason, it is very difficult for the surgeon to compare the respective images and re-confirm the subject area and the affected area.

  The present invention has been made in view of the above, and a radiotherapy apparatus and a radioscopy apparatus that can assist an operator so that a subject can be easily aligned and an affected area can be reconfirmed easily. The purpose is to provide.

  In order to solve the above-mentioned problems and achieve the object, the present invention according to claim 1 is a radiation generating means for generating therapeutic radiation used for treatment of a subject, and a treatment generated by the radiation generating means. Provided between at least two scintillator plates that generate fluorescence according to a predetermined absorption energy distribution by radiation and between the at least two scintillator plates, and shields the fluorescence generated by each scintillator plate in different directions. Reference is made using a light shielding plate, at least two photographing means for photographing images of fluorescence generated by each scintillator plate from directions not shielded by the light shielding plate, and images taken by the at least two photographing means. Image processing means for generating an image for use And features.

  According to a sixth aspect of the present invention, there is provided between the at least two scintillator plates that generate fluorescence according to a predetermined absorbed energy distribution by the therapeutic radiation used for the treatment of the subject. And a light shielding plate that shields the fluorescence generated by each scintillator plate in different directions, and at least two images that capture images of the fluorescence generated by each scintillator plate from directions that are not shielded by the light shielding plate. The image processing apparatus includes: an imaging unit; and an image processing unit that generates an image for reference using images captured by the at least two imaging units.

  According to the first or sixth aspect of the present invention, there is an effect that it is possible to assist the surgeon so that the subject can be easily aligned and the reconfirmation of the affected area can be easily performed.

FIG. 1 is a diagram illustrating an overall configuration of the radiation therapy apparatus according to the first embodiment. FIG. 2 is a diagram illustrating the configuration of the radioscopy unit according to the first embodiment. FIG. 3 is a diagram illustrating the configuration of the radioscopic part according to the second embodiment. FIG. 4 is a diagram illustrating the configuration of the radioscopic part according to the third embodiment. FIG. 5 is a diagram illustrating the configuration of the radioscopic part according to the fourth embodiment. FIG. 6 is a diagram illustrating the configuration of the radioscopic part according to the fifth embodiment. FIG. 7 is a diagram illustrating a state in which an object plane oblique to the optical axis is photographed with a normal video camera. FIG. 8 is a principle diagram for explaining the principle of Scheimplg. FIG. 9 is a schematic diagram showing a correspondence relationship between the image A on the virtual plane and the image B on the scintillator plate surface. FIG. 10 is a schematic diagram showing a correspondence relationship between the image B on the scintillator plate surface and the image C on the image sensor surface. FIG. 11 is a diagram illustrating an example of a conventional EPID. FIG. 12 is a diagram illustrating a mass energy absorption coefficient with respect to photon energy for each living tissue. FIG. 13 is a diagram showing a CT image using X-rays of several tens keV to several hundreds keV and an image photographed by EPID.

  Embodiments of a radiation therapy apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  First, the overall configuration of the radiotherapy apparatus according to the first embodiment will be described. FIG. 1 is a diagram illustrating an overall configuration of the radiotherapy apparatus according to the first embodiment. As shown in FIG. 1, the radiotherapy apparatus 100 according to the first embodiment includes a top plate 1, a stand 2, a gantry 3, a treatment head 4, a radioscopic part 5, and a control device 6.

  The top board 1 is a bed on which a subject H to be subjected to radiation therapy is placed. The stand 2 supports the gantry 3 and includes a driving device for rotating the gantry 3 therein. The gantry 3 supports the treatment head 4 and the radioscopy unit 5 so as to face each other with the top plate 1 interposed therebetween, and the treatment head 4 and the radioscopy unit around the horizontal axis G where the subject H is located. 5 is moved. The gantry 3 includes an electron gun, a waveguide guide, and the like (not shown).

  The treatment head 4 generates therapeutic radiation used for treatment of the subject H. Specifically, the treatment head 4 includes a waveguide guide 4a, a bending magnet 4b, a target 4c, and a collimator 4d. The electron beam L generated by the electron gun of the gantry 3 is accelerated by the waveguide guide 4a and then enters the bending magnet 4b. The bending magnet 4b causes the electron beam L to collide with the target 4c by directing the direction of the incident electron beam L downward. As a result, therapeutic radiation N is generated. The generated therapeutic radiation N is irradiated to the subject H after the irradiation shape and dose distribution are adjusted by the collimator 4d.

  The radioscopy unit 5 detects the radiation that has passed through the subject H, and captures a fluoroscopic image for easy alignment of the subject H and reconfirmation of the affected area. The radiation fluoroscopic unit 5 will be described in detail later.

  The control device 6 controls the entire radiotherapy device 100. For example, the control device 6 rotates the gantry 3 by driving a drive device included in the stand 2 in accordance with an instruction from the operator. Further, for example, the control device 6 performs predetermined image processing on an image photographed by a camera included in the radiation fluoroscopic unit 5 and displays the image subjected to the image processing.

  Under such a configuration, in the first embodiment, the radioscopy unit 5 simultaneously captures fluoroscopic images corresponding to a plurality of types of absorbed energy distribution, and the captured images and the tip of the mass absorption coefficient of each living tissue. Using the test value information, an image separated for each living tissue is generated in real time. As a result, it is possible to present to the operator in real time an image separated for each living tissue or a composite image arbitrarily weighted and added. Therefore, according to the first embodiment, it is possible to assist the operator so that the alignment of the subject and the reconfirmation of the affected area can be easily performed.

  Next, the configuration of the radiation fluoroscopic unit 5 according to the first embodiment will be described. FIG. 2 is a diagram illustrating a configuration of the radioscopy unit 5 according to the first embodiment. The radioscopy unit 5 according to the first embodiment is conventional in that it captures a fluoroscopic image and reconfirms the alignment by capturing from the same viewpoint as the center of the therapeutic radiation source in the radiation therapy apparatus 100. This is the same as EPID using one scintillator plate. Therefore, the radioscopic part 5 is disposed at a position facing the center of the therapeutic radiation source across the subject H.

  As shown in FIG. 2, the radiation fluoroscopic unit 5 according to the first embodiment includes a dark box 5a, two scintillator plates 5b and 5c, a light shielding plate 5d, and two cameras 5e and 5f. The first camera 5e has a first lens system and a first image sensor inside, and the second camera 5f has a second lens system and a second image sensor inside. is doing.

  Here, the scintillator plates 5b and 5c have different absorbed energy distributions. The scintillator plates 5b and 5c are arranged inside the dark box 5a so that the plate surfaces are orthogonal to the central axis F of the therapeutic radiation N after being bonded together via the light shielding plate 5d. Yes.

  Here, a case where a light shielding plate is used as a means for regulating the direction of fluorescence generated by each scintillator plate will be described. However, for example, an X-ray filter having a light shielding effect may be used instead of the light shielding plate. Good.

  In the above configuration, the therapeutic radiation N generated when the accelerated electron beam L hits the target 4c can be regarded as a point light source centered on the collision position between the target 4c and the electron beam L. This point light source corresponds to the center of the therapeutic radiation source, and is adjusted so that the radiation intensity is substantially uniform regardless of the direction by passing through the flattening filter 7.

Then, after passing through the collimator 4d and the subject H, the therapeutic radiation N strikes the first scintillator plate 5b and generates first fluorescence. Next, the therapeutic radiation N passes through the light shielding plate 5d, and then the second scintillator plate 5c having a different absorption energy distribution.
In this case, second fluorescence is generated. Here, since the light shielding plate 5d is provided only to prevent the first fluorescence and the second fluorescence from being mixed, it hardly affects the therapeutic radiation N such as attenuation and scattering.

  An image obtained by photographing the first fluorescence (hereinafter referred to as “first fluorescence image”) is photographed in real time by the first lens system and the first imaging sensor of the camera 5e. Similarly, an image obtained by photographing the second fluorescence (hereinafter referred to as “second fluorescence image”) is also photographed by the second lens system and the second imaging sensor of the camera 5f. Since the geometric arrangement of each lens system and imaging sensor is fixed, the photographed image was photographed on a virtual plane Π (a plane perpendicular to the central axis F of the therapeutic radiation N) shown in FIG. Inverted to image. This inverse transformation will be described later in detail.

  In this way, the fluorescence image fluorescence images photographed by the cameras 5e and 5f are transmitted to the control device 6, respectively.

  The control device 6 generates an image separated for each living tissue or a combined image arbitrarily weighted and added based on the fluorescence images taken by the cameras 5e and 5f. Specifically, when the control device 6 receives the first fluorescence image captured by the camera 5e and the second fluorescence image captured by the camera 5f, the control device 6 obtains a priori information such as a mass source weak coefficient for each tissue. Based on this, an image separated for each living tissue and a composite image arbitrarily weighted and added are generated. Further, the control device 6 performs distortion correction / affine transformation or the like on the captured image in real time to convert it into a geometrically congruent image.

  In each of the first fluorescent image and the second fluorescent image, the signal position of the pixel at the same position corresponds to the integral value of the X-ray absorption of each tissue with respect to the X-ray sources having different absorption energy distributions. Therefore, it is possible to solve the inverse problem for each pixel from the a priori value information of the representative mass source weak coefficient of each tissue, and it is possible to finally separate the images for each tissue.

  Here, an example of a method for generating an image separated for each living tissue will be specifically described. Here, it is assumed that the living tissue is composed only of bones and muscles. In general, the intensity I of X-rays after X-rays having a certain energy E are absorbed by the subject is expressed by the following equation (1).

In the above formula _{(1), I 0 (E} ) is the X-ray intensity in the absence of the subject, μ (E) is the mass source weak coefficient ^(cm 2 / g), ρ is the density (g / ^cm 3), t is the thickness (cm). Subscripts B and M mean bone and muscle, respectively.

Further, in the first fluorescence image, “X-ray intensity when there is no subject” is I ₀₁ , “X-ray intensity measured by the first scintillator plate” is I ₁ , and “tissue mass source weak coefficient” ”Are μ _B1 and μ _M1 , respectively,“ X-ray intensity when there is no subject ”in the second fluorescence image is I ₀₂ , and“ X-ray intensity measured with the second scintillator plate ”is I ₂ The “tissue mass source weak coefficient” is μ _B2 and μ _M2 .

Here, I ₁ and I ₂ are measured values detected by the scintillator plate, and I ₀₁ , I ₀₂ , μ _B1 , μ _M1 , μ _B2 , and μ _M2 are given as a priori values. The following expressions (2) and (3) are established.

By solving this simultaneous linear equation, the bone density ρ _B t _B and the muscle density ρ _M t _M can be obtained for all pixels. Thus, equation (4) shown below, can produce a separated bone image I _B and muscles image I _M corresponding to the formula (5).

  By executing such a series of procedures, the control device 6 generates in real time an image separated for each living tissue based on the fluorescence images taken by the cameras 5e and 5f. In this way, the control device 6 refers to an image separated for each living tissue or a composite image that is arbitrarily subjected to weighting and addition processing, so that a conventional “transmission image using therapeutic radiation as a radiation source” can be used. "Makes it easier to see images that were difficult to distinguish.

  As described above, in the first embodiment, the target 4c generates the therapeutic radiation N used for the treatment of the subject H. Further, the scintillator plates 5b and 5c generate fluorescence according to a predetermined absorbed energy distribution by the therapeutic radiation N, respectively. The light shielding plate 5d shields the fluorescence generated by the scintillator plates 5b and 5c in different directions. The cameras 5e and 5f respectively capture fluorescent images generated by the scintillator plates 5b and 5c from directions that are not shielded by the light shielding plate 5d. And the control apparatus 6 produces | generates the image isolate | separated for every biological tissue contained in the affected part area | region which is a treatment object area | region using the image image | photographed with the cameras 5e and 5f.

  Therefore, according to the first embodiment, it is possible to assist the operator so that the alignment of the subject and the reconfirmation of the affected area can be easily performed. Specifically, an “image with an equivalently high contrast ratio” can be used by presenting an image separated for each tissue or a composite image arbitrarily weighted and added to the operator in real time. As a result, it becomes easy to align the subject and reconfirm the affected area.

  In the first embodiment, the case where two types of scintillator plates are used has been described. However, the present invention is not limited to this. For example, two or more types of scintillator plates may be used. Therefore, in the following, as Example 2, a case where two or more types of scintillator plates are used will be described. In addition, since the whole structure of the radiotherapy apparatus concerning the present Example 2 is fundamentally the same as that of what was shown in FIG. 1, and only the structure of a radioscopy part differs, Here, this Example 2 The structure of the radioscopic part concerning this will be described.

  FIG. 3 is a diagram illustrating the configuration of the radioscopic part according to the second embodiment. As shown in FIG. 3, the radioscopic part according to the second embodiment is configured by stacking radiologically transparent parts 15 and 25 in a direction along the central axis F of the therapeutic radiation N.

  The first radiation fluoroscopic unit 15 includes a dark box 15a, two scintillator plates 15b and 15c, a light shielding plate 15d, and two cameras 15e and 15f. The second radiation fluoroscope 25 includes a dark box 25a, two scintillator plates 25b and 25c, a light shielding plate 25d, and two cameras 25e and 15f.

  Here, the arrangement of the scintillator plates 15b and 15c, the light shielding plate 15d, and the cameras 15e and 15f in the dark box 15a in the first radioscopic part 15 is the same as the scintillator plate in the dark box 5a in the radioscopic part 5 of the first embodiment. The arrangement is the same as that of 5b and 5c, the light shielding plate 5d, and the cameras 5e and 5f.

  Further, the arrangement of the scintillator plates 25b and 25c, the light shielding plate 25d, and the cameras 25e and 25f in the dark box 25a in the second radioscopic part 25 is also the scintillator plate 5b in the dark box 5a in the radiological part 5 of the first embodiment. And 5c, the arrangement of the light shielding plate 5d, and the cameras 5e and 5f.

  Here, as in the first embodiment, a case where a light shielding plate is used as a means for regulating the direction of fluorescence generated by each scintillator plate will be described. For example, instead of the light shielding plate, a light shielding effect is provided. An X-ray filter may be used.

  Here, the scintillator plates 15b and 15c of the first radioscopic part 15 and the scintillator plates 25b and 25c of the second radiological part 25 have different absorbed energy distributions. Therefore, according to the radioscopy part concerning the present Example 2, the radiation of four types of energy distribution can be detected.

  In other words, in the second embodiment, even when four types of biological tissues exist in the affected area, images corresponding to the respective biological tissues can be generated. Similarly, for example, according to a radioscopic part having a scintillator plate having n types of absorbed energy distributions, n types of tissue images can be obtained.

  As described above, in the second embodiment, two or more types of scintillator plates detect radiation according to different absorption energy distributions. Therefore, according to the present Example 2, the image isolate | separated for every kind of biological tissue can be produced | generated.

  In the first and second embodiments, the case where the scintillator plates are arranged so that the flat plate surface is orthogonal to the central axis F of the therapeutic radiation N has been described. However, the present invention is not limited to this. Absent. For example, each scintillator plate may be arranged such that the plate surface obliquely intersects with the central axis F of the therapeutic radiation N. Therefore, in the following, as a third embodiment, a case where the scintillator plates are arranged so that the plate surface obliquely intersects with the central axis F of the therapeutic radiation N will be described. The overall configuration of the radiotherapy apparatus according to the third embodiment is basically the same as that shown in FIG. 1 and only the configuration of the radioscopic part is different. The structure of the radioscopic part concerning this will be described.

  FIG. 4 is a diagram illustrating the configuration of the radioscopic part according to the third embodiment. As shown in FIG. 4, the radiation fluoroscope 35 according to the third embodiment includes a dark box 35a, two scintillator plates 35b and 35c, a light shielding plate 35d, and two cameras 35e and 35f.

  Here, the scintillator plates 35b and 35c have different absorbed energy distributions as in the scintillator plates in the first and second embodiments. In the third embodiment, the scintillator plates 35b and 35c are bonded to each other via the light shielding plate 35d, and the dark surfaces are set so that each plate surface obliquely intersects the central axis F of the therapeutic radiation N. It is arranged inside 35a. At this time, the scintillator plates 35b and 35c are provided so that the surface of the scintillator plate 35b faces the camera 35e and the surface of the scintillator plate 35c faces the camera 35f.

  Here, as in the first and second embodiments, a case where a light shielding plate is used as a means for regulating the direction of fluorescence generated by each scintillator plate will be described. For example, instead of a light shielding plate, a light shielding effect is used. You may use the X-ray filter which has.

  Thus, by arranging the scintillator plates 35b and 35c, for example, the thickness in the direction along the central axis F of the therapeutic radiation N can be reduced as compared with the radioscopic part 5 shown in FIG. . In this case, the processing flow is exactly the same except that the conversion calculation for back projecting the image captured by the imaging sensor onto the virtual plane is slightly changed.

  As described above, in the third embodiment, the scintillator plates 35b and 35c are provided obliquely so that the surfaces of the scintillator plates 35b and 35c face the camera 35e side and the camera 35f side, respectively. Therefore, according to the third embodiment, the thickness in the direction along the central axis F of the therapeutic radiation N can be reduced in the radioscopic part.

  By the way, although the said Example 1, 2, and 3 demonstrated the case where the several scintillator plate which each has different absorption energy distribution was used, this invention is not limited to this. For example, a plurality of scintillator plates having the same absorbed energy distribution may be used. Therefore, hereinafter, as Example 4, a case where a plurality of scintillator plates having the same absorbed energy distribution is used will be described. The overall configuration of the radiotherapy apparatus according to the fourth embodiment is basically the same as that shown in FIG. 1 and only the configuration of the radioscopic part is different. The structure of the radioscopic part concerning this will be described.

  FIG. 5 is a diagram illustrating the configuration of the radioscopic part according to the fourth embodiment. As shown in FIG. 5, the radioscopic part according to the fourth embodiment is configured by stacking two radioscopic parts 45 and 55 in the direction along the central axis F of the therapeutic radiation N, as in the second example. Has been.

  The first radiation fluoroscopic unit 45 includes a dark box 45a, two scintillator plates 45b and 45c, a radiation filter 45d, and two cameras 45e and 45f. The second radiation fluoroscopic unit 55 includes a dark box 55a, two scintillator plates 55b and 55c, a radiation filter 55d, and two cameras 55e and 55f.

  Here, each of the scintillator plates 45b, 45c, 55b and 55c has the same absorbed energy distribution. The scintillator plates 45b and 45c are disposed inside the dark box 45a so that the plate surfaces are orthogonal to the central axis F of the therapeutic radiation N after being bonded together via the radiation filter 45d. ing. In addition, the scintillator plates 55b and 55c are disposed inside the dark box 55a so that the plate surfaces are orthogonal to the central axis F of the therapeutic radiation N after being bonded together via the radiation filter 55d. ing.

  As the radiation filters 45d and 55d used here, for example, a “single-layer flat metal plate” made of a metal such as aluminum or lead, or a “multi-layer flat metal plate” in which those metal plates are laminated. Etc. are available. Each radiation filter also has a light shielding effect.

  Thus, by providing a radiation filter between a plurality of scintillator plates having the same absorption energy distribution, each scintillator plate detects radiation in a different band. This eliminates the need to prepare a plurality of types of scintillator plates having different absorbed energy distributions, thereby improving the degree of design freedom.

  As described above, in the fourth embodiment, the scintillator plates 45b, 45c, 55b, and 55c emit fluorescence according to the same absorbed energy distribution. The radiation filters 45d and 55d are arranged so that each scintillator plate emits fluorescence according to different absorbed energy distributions.

  Therefore, according to the fourth embodiment, since the apparatus can be configured using only the scintillator plate having one absorbed energy distribution, the degree of design freedom can be improved. In addition, the manufacturing cost can be reduced as compared to the case of preparing a plurality of types of scintillator plates having different absorption energy distributions.

  By the way, although the said Examples 1-4 demonstrated the case where the scintillator plate and the light shielding board or the filter for radiation were laminated | stacked, this invention is not limited to this. For example, the scintillator plate and the light shielding plate or the radiation filter may be separate structures. Therefore, in the following, as a fifth embodiment, a case where the scintillator plate and the light shielding plate are made separate structures will be described. The overall configuration of the radiotherapy apparatus according to the fifth embodiment is basically the same as that shown in FIG. 1 and only the configuration of the radioscopic part is different. The structure of the radioscopic part concerning this will be described.

  FIG. 6 is a diagram illustrating the configuration of the radioscopic part according to the fifth embodiment. As illustrated in FIG. 6, the radiation fluoroscopic unit 65 according to the fifth embodiment includes a dark box 65a, two scintillator plates 65b and 65c, a light shielding plate 65d, and two cameras 65e and 65f.

  Here, the scintillator plates 65b and 65c have different absorbed energy distributions. In the fifth embodiment, the scintillator plate 65b is provided on the upper surface of the dark box 65a, and the scintillator plate 65c is provided on the lower surface of the dark box 65a. In addition, the light shielding plate 65d is disposed inside the dark box 65a so as to obliquely intersect the central axis F of the therapeutic radiation N. Here, the light shielding plate 65d is provided so that the angle with respect to the upper surface and the lower surface of the dark box 65a is 45 degrees.

  In the fifth embodiment, the surface of the light shielding plate 65d is mirror finished. Therefore, the light shielding plate 65d functions as a “mirror” that reflects the fluorescence emitted from the scintillator plates 65b and 65c. That is, in the fifth embodiment, the fluorescence emitted from the scintillator plates 65b and 65c is once reflected by the light shielding plate 65d, and the mirror images are taken by the cameras 65e and 65f.

  As described above, in the fifth embodiment, the scintillator plates 65b and 65c are arranged so as to be orthogonal to the central axis F of the therapeutic radiation N. Further, the surface of the light shielding plate 65d is mirror-finished and arranged so as to be oblique to the central axis F of the therapeutic radiation N. Then, the cameras 65e and 65f take a fluorescent mirror image reflected on the light shielding plate 65d. The mirror image reflected on the light shielding plate 65d is in focus for all regions even when taken from an oblique direction, so that it is not necessary to perform correction related to distortion, and image processing can be performed easily.

  In each of the embodiments described above, when the scattered X-rays from the scintillator plate, the light shielding plate, and the radiation filter are an obstacle, a bucky device may be provided between the scintillator plates. Here, the “bucket device” is a collimator that can reciprocate mechanically at high speed.

  In the first to fourth embodiments described above, the fluorescent image on the scintillator plate is taken by the imaging sensor from an oblique direction through the lens system. In this case, when a fluorescent image is taken with a normal video camera, the lens surface and the image sensor surface are parallel, and thus it is not possible to take an image that is in focus in the entire area.

  FIG. 7 is a diagram illustrating a state in which an object plane oblique to the optical axis is photographed with a normal video camera. As shown in FIG. 7, when an object plane oblique to the optical axis is photographed with a normal video camera, only a part of the area is in focus, and an image in which all areas are in focus is photographed. I can't. As a method of avoiding such a focus problem, for example, there is a method of increasing the depth of field, but there is a limit to the depth of field that can be set.

  Therefore, for example, the lens system of the camera is arranged so that the lens surface and the image sensor surface always have a positional relationship that satisfies the Scheimplg principle. The “lens surface” here is a plane orthogonal to the lens optical axis and passing through the center of the lens. The “image sensor surface” is a light receiving surface inside the image sensor.

  FIG. 8 is a principle diagram for explaining the principle of Scheimplg. As shown in FIG. 8, according to the principle of Scheimplg, the object plane (Subject Plane), the lens plane (Lens Plane), and the image sensor plane (Image Plane) intersect at a single common intersection (Scheimpflug Intersection). Placed in. The object surface here corresponds to the scintillator plate surface in each of the embodiments described above.

  Thus, by arranging the scintillator plate, the lens system, and the image sensor so that the scintillator plate surface, the lens surface, and the image sensor surface are in a positional relationship that satisfies the Scheimplg principle, the fluorescent light that is in focus in the entire region is obtained. Images can be taken.

  Next, a method for inversely transforming a captured image on the virtual plane に shown in FIGS. In this case, the image on the virtual plane 直交 that is orthogonal to the central axis F of the therapeutic radiation N is “A”, the image on the scintillator plate surface (or the mirror surface of the radiation filter) is “B”, and the Scheimprug principle is satisfied. Assume that the image on the imaging sensor surface at that time is “C”, and the correspondence between the images is obtained.

  First, the correspondence between the image A on the virtual plane and the image B on the scintillator plate surface is derived. FIG. 9 is a schematic diagram showing a correspondence relationship between the image A on the virtual plane and the image B on the scintillator plate surface.

  As shown in FIG. 9, first, the center point of the therapeutic radiation source is a point P, and the central axis of the therapeutic radiation is a Z axis. That is, the point P is on the Z axis. A virtual plane orthogonal to the Z axis is defined as a plane plane, and an intersection between the Z axis and the plane plane is defined as a point Q. Further, two axes that pass through the point Q and are orthogonal to the Z axis are defined as an X axis and a Y axis. Further, a flat scintillator plate surface oblique to the Z axis is defined as a plane Σ, and an intersection point between the Z axis and the plane Σ is defined as a point R. Further, an X ′ axis and a Y ′ axis that are orthogonal to each other at the point R are set on the plane Σ. At this time, the Y ′ axis is set to be parallel to the Y axis on the plane surface.

The unit vector parallel to the X axis is e ₁ , the unit vector parallel to the Y axis (or Y ′ axis) is e ₂ , the unit vector parallel to the Z axis is e ₃ , and the unit vector parallel to the X ′ axis is and e _4. Further, when an arbitrary point on the plane surface is S, the point S is represented by the following equation (6) starting from the point Q, and the point P is represented by the following equation (7) starting from the point Q. It shall be represented by

  Furthermore, when a point that extends the line segment PS and intersects the plane Σ is a point T, it is assumed that the point T is expressed by the following equation (8) as a point on the plane Σ. Further, it is assumed that the point P is represented by the following formula (9) with the point R as the starting point.

  As a result, Expression (10) is derived from Expression (6) and Expression (7). Further, Expression (11) is derived from Expression (8) and Expression (9).

Here, since the vector PS and the vector PT are on the same straight line, if the proportionality coefficient between them is set to K, the relationship of the following formula (12) is established. Further, from the above definition, the unit vector e ₄ should be expressed by a linear combination of the unit vector e ₁ and the unit vector e ₃ . Therefore, the unit vector e ₄ is expressed by the following equation (13).

Then, by substituting equation (13) into equation (12) and using the fact that the unit vectors e ₁ , e ₂ , and e ₃ are independent of each other, the following equations (14) and (15) can be obtained by simple calculation. ), The relational expression of Expression (16) is derived.

From the above, the correspondence between the image A and the image B is that an arbitrary point S on the plane Π (coordinates (x ₁ , y ₁ ) when the point Q is the starting point on the plane Π) and the plane Σ This is the same as the corresponding relationship with the upper point T (coordinates (x ₂ , y ₂ ) when the point R is the starting point on the plane Σ), that is, the mapping from the point T to the point S is It can be seen that they are associated with Expression (14) and Expression (15).

  Subsequently, a correspondence relationship between the image B on the scintillator plate surface and the image C on the image sensor surface is derived. FIG. 10 is a schematic diagram showing the correspondence between the image B on the scintillator plate surface and the image C on the image sensor surface. Here, when it is assumed that the scintillator plate surface, the lens surface, and the image sensor surface are in a positional relationship that satisfies the Scheimplg principle, an arbitrary point T on the scintillator plate surface (= plane Σ) The relational expression of how to correspond to the point U is derived. Here, the imaging sensor surface is a plane Δ, the lens surface is a plane Γ, and the center point of the lens is a point O ′.

As shown in FIG. 10, here, it is assumed that the scintillator plate surface, the lens surface, and the image sensor surface satisfy the Schieimplug principle, so the common intersection of the plane Σ, the plane Γ, and the plane Δ is It becomes parallel to the Y axis (or Y ′ axis) shown in FIG. Therefore, co Tsuko lines of each plane is parallel to the unit vector e _2. Further, when the intersection of the X ′ axis shown in FIG. 9 and the common intersection of the plane Σ, the plane Γ, and the plane Δ is a point O, and the coordinates of an arbitrary point T are represented by a vector expression with the point O as a starting point, It is expressed as the following equation (17).

Here, an axis passing through the point O on the plane Δ and orthogonal to the common intersection line is taken as an X ″ axis, and a unit vector parallel to the X ″ axis is taken as e ₅ . Further, the light emitted from the point T always passes through the lens center O ′ and goes straight to reach the point U. Here, the point U is represented by the following formula (18) with the point O as the starting point.

For convenience of calculation, it is assumed here that the lens center O ′ is on a line passing through the point O and orthogonal to the common intersection line on the plane Γ. Actually, the lens surface and the lens center are arranged so as to satisfy such a relationship. In this case, the point O ′ is represented as the start point O by the following equation (19). At this time, the vector OO ′ is represented by a linear combination of the unit vector e ₄ and the unit vector e ₅ .

  Further, since the vector TO ′ and the vector UO ′ are in parallel with each other, if the proportionality coefficient between them is H, the following equation (20) is established.

If the unit vectors e ₂ , e ₄ , and e ₅ are used independently, the following relational expressions (21), (22), and (23) are derived by simple calculation.

From the above, the correspondence relationship between the image B and the image C is that the arbitrary point T on the plane （(coordinates (x ′ ₂ , y ′ ₂ ) when the point O is the starting point on the plane Π, and the plane This is the same as the correspondence with the point U on Δ (coordinates (x ₃ , y ₃ ) when the point O is the starting point on the plane Δ), and the correspondence, that is, the mapping from the point U to the point T is It can be seen that they are associated with each other by the equations (21) and (22).

Finally, the coordinates (x ₂ , y ₂ ) (= vector RT) of the point T when the point T is the starting point on the plane Σ and the coordinates (x ′ ₂ , y ′ ₂ ) when the point O is the starting point ) (= Vector OT). In FIG. 10, the following vector expression (24) is established between the point T, the point R, and the point O.

At this time, the vector OR is a constant vector parallel to the x ′ axis. Therefore, when x ′ ₂₀ is a constant, the vector OR is expressed by the following equation (25).

  Therefore, the following relational expressions (26) and (27) are derived by simple calculation.

  Here, from the equations (21) and (22), and the equations (26) and (27), the point U can be mapped to the point T. Further, according to the equations (14) and (15), the point T It can be seen that S can be mapped. That is, it can be seen that the image C is associated with the image B on a one-to-one basis, and the image B is associated with the image A on a one-to-one basis.

  From the above, it can be seen that the image C on the imaging sensor surface Δ can be converted while maintaining a one-to-one relationship with the image A on the virtual plane Π. Therefore, in each of the above-described embodiments, a plurality of images obtained by different scintillator plates photographed by the radioscopy unit have image information photographed by the image sensor and position information of the optical system (even if the scintillator plate positions are different). = The position of the scintillator plate, the position of each lens, and the position of each image sensor) can be inversely converted (inverse mapped) into an image on a virtual plane Π. By combining this with the biological tissue separation algorithm described above, a separated image for each biological tissue can be obtained.

  In addition, if Cone-Beam CT imaging is performed using the radioscopic part described in the above-described embodiment, a metal having energy of several MeV is relatively easily transmitted through the metal. Therefore, for each tissue without streak artifacts. It is also possible to obtain a tomographic image.

DESCRIPTION OF SYMBOLS 1 Top plate 2 Stand 3 Gantry 4 Treatment head 4a Wave guide 4b Bending magnet 4c Target 4d Collimator 5,15,25,35,45,55,65 Radioscopic part 5a, 15a, 25a, 35a, 45a, 55a, 65a Dark box 5b, 5c, 15b, 15c, 25b, 25c, 35b, 35c, 45b, 45c, 55b, 55c, 65b, 65c Scintillator plate 5d, 15d, 25d, 35d, 45d, 55d, 65d, 45d For light shielding plate or radiation Filter 5e, 5f, 15e, 15f, 25e, 25f, 35e, 35f, 45e, 45f, 55e, 55f, 65e, 65f, camera 6 control device 7 flattening filter 100 radiation therapy device

Claims (6)

Radiation generating means for generating therapeutic radiation used for treatment of a subject;
At least two scintillator plates each generating fluorescence according to a predetermined absorbed energy distribution by the therapeutic radiation generated by the radiation generating means;
A light shielding plate that is provided between the at least two scintillator plates and shields the fluorescence generated by each scintillator plate in different directions;
At least two photographing means for photographing images of fluorescence generated by each scintillator plate from directions not shielded by the light shielding plate;
A radiotherapy apparatus comprising: an image processing unit that generates a reference image using images captured by the at least two imaging units. The at least two scintillator plates each emit fluorescence according to the same absorption energy distribution,
The radiation according to claim 1, wherein the light shielding plate is a radiation filter having a light shielding effect, and the at least two scintillator plates are arranged to emit fluorescence according to different absorption energy distributions. Therapeutic device.   3. The radiotherapy apparatus according to claim 1, wherein the scintillator plate and the light shielding plate are disposed so as to be orthogonal to a central axis of therapeutic radiation generated by the radiation generating unit. . The scintillator plate is disposed so as to be orthogonal to the central axis of the therapeutic radiation generated by the radiation generating means,
The light-shielding plate has a mirror-finished surface and is disposed so as to be oblique to the central axis of the therapeutic radiation generated by the radiation generating means.
The radiotherapy apparatus according to claim 1, wherein the imaging unit captures a mirror image of the fluorescence reflected on the light shielding plate. The photographing means has a lens and an image sensor,
The radiotherapy according to any one of claims 1 to 4, wherein the scintillator plate, the lens, and the image sensor are arranged such that their surfaces intersect at a single common intersection line. apparatus. At least two scintillator plates each generating fluorescence according to a predetermined absorbed energy distribution by therapeutic radiation used for treatment of the subject;
A light shielding plate that is provided between the at least two scintillator plates and shields the fluorescence generated by each scintillator plate in different directions;
At least two photographing means for photographing images of fluorescence generated by each scintillator plate from directions not shielded by the light shielding plate;
A radioscopy apparatus comprising: image processing means for generating a reference image using images taken by the at least two photographing means.

Images