JPH05269215A - Stereotaxic radio-active radiation type therapeutic device incorporating monitoring function - Google Patents

Abstract

PURPOSE:To monitor a shift of the position of irradiation of X-rays during treatment by detecting a value of leakage X-rays transmitted through a body to be checked from a stereotaxic collimator together with the value of therapeutic X-rays transmitted through the body. CONSTITUTION:A circular multi-element type X-ray detector 4 is provided on the X-ray transmission side of a patient 6, facing a porous collimator 3 so as to detect X-rays transmitted from the patient 4 from the porous collimator 3 in order to issue an electric signal. Further, the detection electric signal from the detector 4 is delivered to a computer through a coupling part 5 so as to be visualized and displayed on a CRT for monitoring. When a positional shift is detected, the degree of the positional shift is fed-back so as to carry out a positional adjustment to a gantry, a stereotaxic collimator, a treating bed or the like for compensation. Accordingly, the position of irradiation in a lesion can be confirmed during treatment, thereby it is possible to rapidly compensate the position of irradiation even though an erroneous position is irradiated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stereotactic radiotherapy apparatus for squeezing an X-ray flux and irradiating it in a concentrated manner to treat an affected area.

[0002]

2. Description of the Related Art As a conventional example of a stereotactic radiotherapy apparatus, there is a patent application publication No. 2-503521. In this conventional example, the treatment table is rotated about a vertical axis, the gantry is rotated about a horizontal axis, and various therapeutic X-rays are applied to the affected area via a collimator for localization method attached to the tip of the gantry. It tries to irradiate from a wide angle. This stereotactic treatment has the advantage that it is very effective in treating malignant tumors and that radiation exposure to the surrounding normal tissues is significantly reduced.

As described above, in the stereotactic method, the dose to be administered to the lesion is very large as compared with the conventional radiotherapy. Therefore, when irradiation is accurately concentrated on the lesion, a very large therapeutic effect can be expected, but if the irradiation position is misaligned with respect to the lesion, the damage to normal tissue will be great, and It can be fatal as well. Therefore, in the localization method, the irradiation position must always be matched with the position of the lesion with extremely high accuracy. As such a positioning method, conventionally, the lesion position is measured in advance by another diagnostic device (CT, MRI, simulator, etc.), and the measured lesion position is adjusted only by the mechanical accuracy of the stereotactic radiotherapy apparatus. The method was taken. Alternatively, before treatment, there is a method of performing irradiation after confirming the irradiation position by so-called linacography, in which irradiation is performed with a low dose in a wide irradiation field to obtain a transmission image. Linacgraphy is fluoroscopic imaging by radiation of a therapeutic accelerator that is mainly performed in conventional radiotherapy other than stereotactic method. Even when a transmission image is taken using a therapeutic use flux, if the irradiation field is wide enough to allow sufficient judgment of the patient's anatomical position, the irradiation position monitor during the treatment could be performed by the conventional technique. However, in the radiation treatment in a very small irradiation field such as performed by the stereotactic method, the anatomical position of the patient cannot be determined only by using the therapeutic use flux. Therefore, until now, in the stereotactic method, the position of the irradiation was not monitored during the treatment, and the irradiation position was confirmed by the linac graph in a wide irradiation field including the therapeutic use flux taken immediately before the treatment, and only the mechanical accuracy was guaranteed.

[0004]

However, in the prior art, at the stage of transferring a patient from another diagnostic device to a therapeutic device,
The lesion may be displaced from the position measured before the treatment. In addition, the patient's condition can be reproduced very well, and even if the transmission image can be confirmed immediately before the treatment, the irradiation position cannot be confirmed at all during the treatment. It is also conceivable that the lesion part will shift from the irradiation position. In order to perform reliable positioning as described above, it is necessary to grasp the position of the lesion and the irradiation position even during treatment so that the lesion is always irradiated with certainty.

It is an object of the present invention to provide a stereotactic radiotherapy apparatus that monitors a transmission image so that the irradiation position can be surely confirmed even during the treatment by such a stereotactic method.

[0006]

According to the present invention, there is provided a therapeutic gantry which has a means for converting an electron beam into X-rays and is rotatably supported, and an irradiation head which is supported by the therapeutic gantry and emits X-rays. A collimator for a localization method for thinning the X-ray flux from the irradiation head, and a patient-mounting treatment table having a rotation direction different from the rotation direction of the gantry. And a monitoring unit for monitoring leaked X-rays that pass through the collimator for localization method in the peripheral portion of the therapeutic X-ray emitting unit of the collimator for localization method and localization method.

Further, according to the present invention, there is provided a treatment gantry which has a means for converting an electron beam into an X-ray and is rotatably supported, an irradiation head which is supported by the treatment gantry and emits an X-ray, and an irradiation head. The collimator for localization method for thinning the X-ray flux and the treatment table for mounting a patient having a rotation direction different from the rotation direction of the gantry, and provided on the X-ray emission side of the collimator for localization method. And a porous collimator having a hole for passing the therapeutic X-ray and a porous for passing a leaking X-ray passing through the collimator for localization method,
An X-ray detector that opposes the porous collimator across the patient and detects X-rays from the multi-holes of the porous collimator through the patient, and the detection value of the X-ray detector is used to reach the treatment site. And a monitoring unit for monitoring the status of irradiation of therapeutic X-rays (position, contents of irradiation).

Further, the present invention provides that the above-mentioned monitoring unit uses a therapeutic X
It is assumed that the irradiation position of the line is monitored, and if the positional deviation occurs, the irradiation position is corrected (claim 3).

Further, according to the present invention, the X-ray detector converts the X-ray into an optical signal or an electric signal for detection (Claim 4).

[0010]

According to the present invention, leaked X-rays obtained by passing through the collimator for stereotactic method are obtained through the patient and detected to monitor the irradiation condition of therapeutic X-rays. 1). As a result, it is possible to observe the displacement of the therapeutic X-ray and the like only with the leaked X-ray without using other X-rays.

Further, according to the present invention, the scattered X-rays are removed from the leaked X-rays by the porous collimator, the leaked X-rays are surely detected, and the irradiation position of the therapeutic X-rays is monitored (claim 2). ). As a result, leaked X-rays can be reliably detected, and it becomes possible to accurately observe misalignment of therapeutic X-rays.

Further, according to the present invention, the irradiation position shift is corrected from the monitoring result (claim 3). As a result, the positional deviation can be corrected during irradiation.

Furthermore, according to the present invention, X-rays can be detected by optical or electric signals (claim 4), and monitoring can be performed reliably.

[0014]

FIG. 2 shows an embodiment of the therapeutic apparatus of the present invention, and FIG. 1 shows an embodiment centering on the monitoring unit. FIG. 3 shows an embodiment of a porous collimator. In FIG. 2, the therapeutic gantry 1
0 is supported by the gantry supporting portion 11. High energy electrons are applied to the gantry 10 from an electron accelerator 12 via a carrier system (not shown). Gantry 10
Has an X-ray target inside which emits X-rays by irradiating high-energy electrons. The irradiation head 14 is a gantry 1.
It is attached to the tip of No. 0 and emits X-rays from the X-ray target with a predetermined collimation. The localization method collimator 2 is a collimator for narrowing down the X-ray from the irradiation head 14 for treatment. Porous collimator 3
Is one of the features of this embodiment, and the collimator 2 for localization method is used.
Has a large number of holes in order to pass the beam flux beam that is normally emitted from the laser beam and the leakage X-ray that is transmitted and emitted from the collimator 2 for localization method and to remove unnecessary scattered rays.

The treatment table 13 is supported by the rotation support portion 15 and rotates about the vertical axis. A patient 6 is placed on the treatment table 13. The gantry 10 rotates about a horizontal axis. The rotation of the treatment table 13 is intermittent, for example, 20 ° rotation → stationary → 20 ° rotation (rotates 20 ° -40 °) → stationary → 20 ° rotation (rotates 40 ° -60 °) → ... As described above, the rotation of a predetermined pitch unit and the stop are repeated. During this stationary state, the gantry 10 rotates 180 ° or 360 ° while emitting X-rays to treat the lesion 7. In addition to this, it goes without saying that there are various systems such as a system in which the treatment table 13 and the gantry 10 rotate continuously with respect to each other.

A circular multi-element X-ray detector 4 is provided on the X-ray transmitting side of the patient 6 facing the porous collimator 3. The X-ray detector 4 detects X-rays (including leaked X-rays) from the porous collimator 3 that have passed through the patient as electric signals. This detected electric signal is taken out through the gantry coupling portion 5 and is used for monitoring.

FIG. 2 is an enlarged view of the monitor section, and the gantry 10 and the irradiation head 14 are omitted. X-rays from the X-ray target 1 as a radiation source enter the collimating hole 2A of the localization method collimator 2 and are subjected to line bundle focusing.
As shown in FIG. 3, the porous collimator 3 has porous 3A such as briquettes. A hole 3B for the collimating hole 2A is provided at the center of each of the perforations 3A so that the therapeutic X-rays with a focused beam bundle can pass therethrough. The holes other than the hole 3B are holes for allowing the leaked X-rays from the collimator 2 for localization method to pass therethrough and for removing unnecessary scattered rays. The exit direction of these holes, through which leaked X-rays pass, is the multi-element X facing each other.
This is the direction towards the corresponding detector element in the line detector.

The collimator 2 for localization method is originally not good in the presence of leaked X-rays. Even if it leaks, it is required that the radiation dose not affect the patient and the surrounding area. Radiation that leaks through the collimator (hereinafter, leakage line) has a small dose, but the breakdown of the leakage line is a direct line directly coming from the radiation source and a scattered line generated by scattering in the collimator. Up to now, efforts have been made to reduce leak lines as unnecessary as much as possible. However, this leakage line is relatively widely distributed around the therapeutic use flux, and the dose can be easily adjusted by changing the thickness D of the collimator.
It has convenient characteristics for confirming the irradiation position by a transmission image during treatment. Therefore, in this embodiment, the leaked X-rays from the collimator for localization method are used to monitor the irradiation position deviation of the therapeutic X-rays. In FIG. 4, the center line of the collimator for localization method (corresponding to the center line of the therapeutic X-ray)
The distribution of the irradiation dose from is shown. Thus, therapeutic X
Since the amounts of the X-ray and the leaked X-ray are different, the two can be detected separately and used for monitoring. Incidentally, in the case where the leakage X-ray dose of the conventional collimator is small and it is not useful for monitoring, a collimator for localization method with a reduced thickness D may be used.

In normal fluoroscopy, about 10 mGy / min
Irradiate the dose rate of. If 2 Gy / min is used as the dose rate of therapeutic radiation in the stereotactic method, the dose rate used for fluoroscopy is about 0.5% of the dose rate used for treatment. For example, when a localization collimator is made of tungsten, the thickness of the collimator for attenuating 10 MV X-rays to 0.5% is about 7 cm. The collimator 3 for removing scattered rays is preferably as thick as possible. For example, about 4 cm
If the collimator for removing scattered rays is used, extra X-rays (scattered X-rays, etc.) transmitted through the collimator for localization method can be further attenuated to about 15% thereof.

The multi-element X-ray detector 4 detects the therapeutic X-rays that have passed through the patient and the leaked X-rays around them. Whether or not the therapeutic X-ray is irradiated to the normal position can be known by monitoring spots in the transmission image of the leaked X-ray and the transmission image of the treatment X-ray. For this reason, for the purpose of monitoring, the detection signal of the X-ray detector is taken into the computer through the coupling unit 5, and this is imaged and displayed on the CRT for monitoring. Further, in this monitoring, by comparing with the data based on the treatment plan established in advance, a more accurate state of the positional deviation can be known. Also, instead of displaying it on the CRT,
There is also a method of finding the positional deviation in data processing.

When the positional deviation is found, in order to correct the positional deviation, the positional deviation amount is fed back to adjust the position of the gantry, the position adjustment of the collimator for localization method, the position adjustment of the treatment table, etc. Correct the misalignment with. It may be automatic or manual.

FIG. 5 is a system diagram for realizing the embodiment of FIG. In this embodiment, a stereotactic radiotherapy device 20, a gantry treatment table control device 21, an AD converter 22, a treatment device operation console 23, an image processing device 24, a CRT monitor 25, 2 are provided.
6. An irradiation position comparison device 27, a treatment planning device 28, and an image diagnosis device 29.

First, the position and status of the treatment site are examined by the image diagnostic device 29, and the treatment plan is prepared in the treatment planning device 28. According to this plan, the treatment device 20
Under the control of the console 23, the control device 21 controls the stereotactic treatment. During this treatment, the transmission image is taken into the image processing device 24 through the AD converter 22 and displayed as an image on the CRT monitor 25, and the image data is compared with the treatment plan by the comparison device 27, and the positional deviation is detected. Whether or not it is occurring, and if it is occurring, the amount of deviation in which direction is calculated. And this comparative image is displayed on the CRT monitor 26 and visually confirmed by the doctor. The shift amount and the direction thereof are sent to the control device 21 and the position is corrected.

FIG. 6 shows another embodiment that achieves the same function as the perforated collimator. What is called a scattered X-ray removal grid is used for removing scattered X-rays incident on the image receiving surface during X-ray inspection. In this example, one scattered X-ray removing porous collimator was formed using two scattered X-ray removing grids 30 and 35. Grid 3
0 and 35 are both material layers having small X-ray absorption (for example, paper, wood, aluminum, resin, etc.) 32 and 36 (layers for obtaining transmitted X-rays) and material layers having large X-ray absorption (lead. Or tungsten) 31, 37 (layers for absorbing scattered X-rays) are alternately laminated. Grids 30 and 3
5 has a stacking direction perpendicular to each other in the vertical direction and the horizontal direction, and both grids 30 and 35 were superposed in the direction of the arrow to form one collimator. According to this collimator, the material layers 32 and 36 having small X-ray absorption are provided.
Has a cross region due to matrix intersection, and can achieve the same purpose as the porous collimator shown in FIG. Incidentally, 30A is a hole corresponding to the collimator hole for the localization method, and also has a similar hole corresponding to the grid 35.

There is also a method in which a fluorescent plate is provided in place of the X-ray detector, the visible light is generated from the fluorescent plate upon receiving the X-ray, and this is imaged by a TV camera. This is a method called the so-called fluorescent TV image method. In this case, TV
The computer captures the image pickup signal from the
It is displayed as an image on T or the like.

The image obtained in the embodiment is obtained in the form of a point image, but such an image can be made a clear image by complementing the image data. Image complementing techniques are already common in the field of nuclear medicine devices such as gamma cameras. Also, the spatial resolution of the image is improved by reducing the hole diameter of the multi-hole collimator and increasing the number of holes. Furthermore, it goes without saying that, in addition to the detection of the displacement of the treatment position, the grasp of the irradiation range and the irradiation condition from moment to moment can be monitored. Further, if the material of the porous collimator (including the example of FIG. 6) is constant, it is preferable that the leaked X-ray can be made uniform, but even if the material is non-uniform, this non-uniform If the calibration values are theoretically or actually measured in and, and the correction values are corrected, the nonuniformity is not a problem.

[0027]

According to the present invention, the irradiation position with respect to the lesion can be confirmed during the treatment, and even if the irradiation position is wrong, the correction can be performed quickly. Therefore, a large dose can be safely administered to the lesion and a high therapeutic effect can be obtained.

[Brief description of drawings]

FIG. 1 is an embodiment of a monitoring means of a stereotactic radiotherapy apparatus of the present invention.

FIG. 2 is an embodiment of the stereotactic radiotherapy apparatus of the present invention.

FIG. 3 is a diagram showing an embodiment of a porous collimator of the present invention.

FIG. 4 is a diagram showing irradiation distributions of therapeutic X-rays and leaked X-rays emitted from the collimator for stereotactic method of the present invention.

FIG. 5 is a system configuration example diagram of the stereotactic radiotherapy apparatus of the present invention.

FIG. 6 is a diagram showing another embodiment of a porous collimator.

[Explanation of symbols]

 1 Radiation Source 2 Collimator for Stereotactic Method 3 Porous Collimator 4 Multi-Element Type Radiation Detector 5 Coupling 6 Patient 7 Lesion 8 Treatment Use Flux 9 Fluorescence Use Flux 10 Treatment Gantry 11 Gantry Support 12 Electron Accelerator 13 Treatment Stand 14 irradiation head

Claims (4)

[Claims] 1. A treatment gantry which has a means for converting an electron beam into X-rays and is rotatably supported, an irradiation head which is supported by the treatment gantry and emits X-rays, and an X-ray from the irradiation head. A collimator for localization method for thinning a ray bundle, and a treatment table for mounting a patient having a rotation direction different from the rotation direction of the gantry, and a collimator for treatment X-rays and localization method which penetrates the patient. For treatment of X
A stereotactic radiotherapy apparatus having a monitoring function, which comprises a monitoring unit for monitoring leaked X-rays from a region around the radiation emitting unit. 2. A treatment gantry that has a means for converting an electron beam into X-rays and is rotatably supported, an irradiation head that is supported by the treatment gantry and emits X-rays, and an X-ray from the irradiation head. A collimator for localization method for narrowing the beam flux, and a patient-mounting treatment table having a rotation direction different from the rotation direction of the gantry, and provided on the X-ray emission side of the collimator for localization method, A porous collimator having a hole for passing a therapeutic X-ray and a porous for passing a leaking X-ray passing through a collimator for localization method, and an X-ray from the porous hole of the porous collimator facing the porous collimator with the patient in between. An X-ray detector that detects the radiation through the patient, and a monitoring unit that monitors the irradiation status (position and contents of irradiation) of the therapeutic X-ray to the treatment site using the detection value of the X-ray detector. When,
Stereotactic radiotherapy device with a monitoring function. 3. The monitoring function according to claim 1 or 2, wherein the monitoring unit monitors the irradiation position of the therapeutic X-ray, and corrects the irradiation position if a displacement occurs. Stereotactic radiotherapy equipment. 4. The stereotactic radiotherapy apparatus having a monitoring function according to claim 2, wherein the X-ray detector converts the X-ray into an optical signal or an electric signal for detection.