JP2001276239A - Radiation energy distribution regulating mechanism and radiation irradiation method and device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a dose distribution reproducing approximately a three- dimensional shape without using a correction device prepared for each patient. SOLUTION: A plurality of boluses 44A to 44E, at least inside diameters of which can be varied, a ring bolus insertion means to insert each of the ring boluses into radiation irradiation routes, in accordance with an energy shape in the necessary depth direction of passed radiation, and a collimator 50 to shield radiation to unnecessary radiation areas in accordance with a necessary plane energy shape are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation energy distribution adjusting mechanism and a radiation irradiation method and apparatus using the same, and more particularly, to a patient suitable for use in a clinical proton therapy system, for example, a patient. The present invention relates to a radiation energy distribution adjusting mechanism for adjusting the energy distribution of radiation irradiated from outside to an affected part into an arbitrary shape, and a radiation irradiation method and apparatus using the same.

[0002]

2. Description of the Related Art A charged particle is accelerated at high speed and high energy in a vacuum by a particle accelerator, and X-rays generated by this are accelerated.
Electron beam, neutron beam, proton beam, pion beam, heavy ion beam, etc.
External radiation therapy in which gamma rays or the like from a cobalt teletherapy device are radiated percutaneously from the outside of a patient to a lesion has become an important therapy together with surgery in the treatment of solid cancer. In particular, since damage to normal tissues around the affected area can be reduced, the demand is expected to increase further in future medical practice where the quality of life (QOL) of patients is emphasized.

[0003] In the radiation treatment by external irradiation, it is important to avoid the surrounding normal tissues or important organs and to give the affected part an irradiation dose distribution that matches the shape of the affected part as accurately as possible. In proton therapy, as shown in FIG. 1, only the cancerous tissue is covered with the Bragg peak P by utilizing the property that the proton beam incident on the substance gives the maximum dose at the Bragg peak P immediately before stopping. By doing so, we try to realize this ideal.

[0004] In the operation of radiotherapy, as shown in FIG. 2, first, in step 100, an X-ray CT image of an affected part is taken. Based on the captured image, a treatment plan is made in step 110 in consideration of the patient's body contour, affected area, and surrounding vital organs. Based on the number of irradiation portals, the direction, and the radiation intensity determined in this treatment plan, in step 120, selection and processing of a fixing auxiliary tool for finely adjusting the irradiation radiation are performed. Next, in step 130, after the patient is positioned 132, irradiation treatment by irradiation 134 is performed.

FIG. 3 shows the configuration of a radiotherapy system. In this radiotherapy system, radiation generated by a radiation generator 10 such as an accelerator passes through a radiation transport device 12 and is guided to a gantry nozzle 14 for irradiating a patient 8 with radiation. In the gantry nozzle 14, the radiation is adjusted to a uniform energy distribution by the radiation observation / adjustment mechanism 16, and then the radiation energy shape forming mechanism 18
The desired energy distribution to be irradiated to the affected part is adjusted, and this is irradiated from outside the patient 8 toward the affected part. Since the dose distribution in the patient is determined by the energy distribution of the radiation, it is planned in advance in consideration of the shape of the affected part.

That is, radiation obtained from the accelerator, for example, a proton beam, has a narrow beam shape, and its energy (the depth of the Bragg peak P) is constant. On the other hand, cancer tissues have various sizes and complicated shapes, the depth in the body is not constant, and the density of the tissue through which proton beams have to pass is not uniform. Therefore, in order to perform proton beam therapy, the proton beam is expanded to (1) a beam wide enough to irradiate the entire cancer at one time, and (2) its energy is adjusted according to the depth of the cancer. (3) Provide an energy distribution according to the thickness of the cancer so as to uniformly irradiate the entire cancer tissue having a depth, and (4) reduce the unevenness of the cancer contour and the tissue through which the proton beam passes. It is necessary to make appropriate corrections.

Therefore, in the conventional external radiotherapy, in order to compensate for the dose distribution in the patient, the radiation energy shape forming mechanism 18 is used when the skin surface of the irradiation site is not flat or the target to be irradiated is Energy distribution correction devices, such as compensation filters, have been used to compensate for dose distribution distortions when they have an inclination with the skin surface.

The compensating filter may be a wedge filter which is a filter plate used in a conventional radiotherapy, for example, such that a spatial isodose curve of a passed beam has a constant slope, or placed on the skin surface. There are boluses used to flatten the irregularities on the illuminated surface. In recent heavy ion beam therapy, a therapy for creating a patient bolus for reproducing the affected part shape from a plurality of irradiation directions for each patient to be treated has been attempted.

Further, in the mechanism for finally adjusting the radiation to be applied, the energy distribution correcting device and the irradiation field shaping device for shaping an irradiation field by shielding an area irradiated with unnecessary radiation are used at the same time. Is normal.

For high-energy radiation, a block collimator for creating an irregular rectangular irradiation field by shielding unnecessary beam portions, and as shown in FIG. A multi-leaf collimator that can be set in the irradiation field according to the shape of the target to be irradiated by moving a rod-shaped collimator of about several mm to 1 cm. There is a patient collimator or the like that limits an irradiation field to an affected part shape by cutting a plate into the shape. The multi-leaf collimator is becoming standard equipment in recent high energy radiation therapy apparatuses.

Specifically, for example, in proton beam therapy, FIG.
As shown in (1), an energy distribution matching the shape of the irradiation target is formed. That is, the narrow proton beam 20 sent to the gantry nozzle 14 as the irradiation unit is expanded in the lateral direction by a scatterer 22 made of, for example, lead having a thickness of several mm, and expanded into a wide beam 24. I do. When a portion having a relatively uniform energy near the central axis is cut out from the expanded beam 24 that spreads and propagates in a conical shape having the scatterer 22 as a vertex by using a collimator described below, a lower treatment table (shown in FIG. Above), the diameter required for treatment is more than 10 cm
Is obtained.

The expanded beam 24 is a fine degrader 26 for adjusting the maximum depth of the proton beam according to the depth of the treatment target (for example, the tumor 8C in the body of the patient 8).
Is incident on. The fine degrader 26 includes, for example, two wedge-shaped opposed acrylic blocks 26.
a, 26b. The thickness of the portion through which the proton beam passes can be continuously changed by adjusting the overlapping manner of the blocks 26a, 26b. The proton beam loses energy according to the thickness of the material that has passed, and the depth at which it can reach varies.
By adjusting 6, the Bragg peak P shown in FIG. 1 can be adjusted to the depth at which the treatment is required.

The proton beam transmitted through the fine degrader 26 is incident on a ridge filter 28 for providing a distribution ΔP in the energy depth of the proton beam corresponding to the thickness of the tumor 8C. The ridge filter 28 is, for example, a triangular prism-shaped metal rod whose thickness changes stepwise in a staggered manner. Since proton beams passing through portions having different thicknesses produce Bragg peaks P at different depths. By adjusting the width and height of the stairs, they can be superimposed appropriately and the peak width ΔP
Can be expanded.

The proton beam passing through the ridge filter 28 is incident on a block collimator 30 for roughly shaping the planar shape of the proton beam. The reason why the shaping is performed by the block collimator 30 in addition to the final collimator to be described later is to prevent generation of secondary radiation by the block collimator near the patient 8.

The proton beam that has passed through the block collimator 30 is input to a bolus 32, which is, for example, a resin-made irregular filter, and correction is made for the maximum depth of the tumor 8C and the non-uniformity of the tissue. This bolus 32
Is calculated based on the contour line of the tumor 8C and the electron density of the surrounding tissue obtained from, for example, X-ray CT data.

The proton beam having passed through the bolus 32 is incident on a final collimator 34 made of, for example, brass, and is finally adjusted to the contour of the planar shape of the tumor 8C. 8 is irradiated.

FIGS. 6 and 7 show an outline of a conventional radiotherapy using the above-described energy distribution adjusting mechanism. FIG.
Is an example of X-ray irradiation in which a dose distribution D is formed using a wedge filter 33 on the patient's head 8H. FIG.
Is an example of two-beam irradiation of proton beam orthogonally to the liver 8L of the patient. In this example, a patient bolus 32 corresponding to the shape of the affected part of the patient is processed and used to obtain a dose distribution D concentrated on the shape of the affected part. In these two examples, the energy distribution adjusting mechanism is fixed with respect to the irradiation direction.

Further, in the conventional treatment plan, the combination of the above-mentioned energy distribution correcting devices is performed by trial and error based on empirical rules. The same is true for the treatment plan in the heavy ion beam therapy, and improvement of the irradiation method has been desired in order to further improve the treatment effect and the treatment speed.

[0019]

That is, the radiation energy distribution adjusting mechanism of the conventional radiation treatment system has the following problems in terms of treatment efficiency.

(1) Since the irradiation pattern is constituted only by a combination of relatively simple correction tools, there is a large mechanical limitation on irradiation for avoiding a complicated affected part shape or an important organ. In particular, in the case of using a beam having high permeability such as a proton beam or a heavy particle beam, even a multi-leaf collimator cannot be used for a small tumor.

(2) The dose distribution correcting device and the irradiation field shaping device are both fixed at the time of irradiation, and when a different irradiation pattern is to be provided, the correction device must be re-equipped for each irradiation. .

(3) When a correction tool created for each treatment, such as a patient bolus, is used, there is a problem in the time and cost for creating the correction tool.

(4) When a correction tool is prepared for each treatment, the correction tool that has been used once becomes radioactive waste, and it is difficult to handle it when discarding.

The present invention has been made in order to solve the above-mentioned conventional problems, and it is a first object of the present invention to realize a three-dimensional dose distribution according to the shape of a diseased part in a patient without replacing a correction tool. Subject.

A second object of the present invention is to improve the accuracy of radiotherapy and shorten the actual irradiation time to reduce the burden on the patient.

[0026]

According to the present invention, there is provided a radiation energy distribution adjusting mechanism for adjusting the energy distribution of irradiated radiation into an arbitrary shape. A ring bolus group consisting of multiple ring boluses that can be
Ring bolus insertion means for inserting each ring bolus into the radiation irradiation path according to the required depth direction radiation dose of the passed radiation, and unnecessary irradiation area according to the required planar dose distribution The first problem has been solved by providing a collimator for shielding radiation to the light source.

Further, the inner diameter of the plurality of ring boluses is
The inner diameter can be made different by changing or changing each other.

Further, by dividing the plurality of ring boluses in the circumferential direction, the ring bolus can be moved in and out with a small stroke, and the size of the apparatus can be reduced.

Further, a radiation irradiation opening of the collimator is
It is a simple geometry that facilitates manufacture.

Further, the second problem is solved by irradiating a radiation capable of obtaining a three-dimensional dose distribution according to the shape of an affected part in a patient using the radiation energy distribution adjusting mechanism. .

In the same radiation irradiating apparatus, the energy distribution adjusting mechanism of the radiation and the ring bolus in the energy distribution adjusting mechanism are automatically moved in and out in accordance with the required depth-wise arrival amount of the passed radiation. The above-mentioned second problem is also solved by providing a ring bolus drive mechanism for performing the above.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 8, a first embodiment of a radiation energy distribution adjusting mechanism according to the present invention comprises a circular collimator 40 instead of the block collimator 30 shown in FIG.
A ring bolus mechanism 42 replacing the patient bolus 32,
In place of the final collimator 34, there is provided a geometric collimator 50 in which the radiation irradiation aperture has a simple geometric shape (here, a triangle).

It should be noted that a multi-leaf collimator, a patient collimator, or the like can be used in combination depending on the treatment grade.

The ring bolus mechanism 42 includes a plurality (five in the figure) of ring boluses 44A made of a radiation energy absorber, for example, having the same plate thickness and different inner diameters.
And a ring bolus driving mechanism 46A to 46E made of, for example, a ball screw for entering and leaving each ring bolus 44A to 44E as necessary, and an energy distribution reproducible by a combination of the ring bolus and the collimator. To illuminate the target
In response to an instruction from the operation terminal 52, the ring bolus 4
A ring bolus / collimator controller 54 for storing unused ones of the 4A to 44E or replacing the geometric collimator 50 with a geometric collimator having another opening shape is provided.

In the present embodiment, when a treatment plan is performed such that the three-dimensional affected part shape can be entirely covered with a combination of a part of the ellipsoidal surface, the incident radiation forms the planned ellipsoidal dose distribution. It operates so as to have a radiation energy distribution as follows.

Alternatively, an irradiation pattern optimized based on a certain evaluation criterion is used.

Here, the evaluation criteria are the dose in the target, its uniformity, the influence on the surrounding normal tissue, DVH (do
A result based on se volume histogram) can be considered. Note that each of the irradiation patterns obtained by the optimization does not necessarily need to directly correspond to a part of the target shape.

Here, focusing only on the equal energy lines or energy peaks of the irradiated radiation and expressing this as an energy distribution, it is assumed that the radiation uniformly enters the entire ring bolus group from the vertical direction. Radiation that has passed through the ring bolus group is uniformly absorbed by each ring bolus, causing a difference in the radiation reaching distance after the radiation enters the patient. If this is illustrated by an equal energy surface, a rotationally symmetric elliptical energy distribution E corresponding to the combination of the ring boluses is formed. Furthermore,
The planned dose distribution D is finally formed in the body by cutting out the radiation to the unnecessary irradiation area by the geometrical collimator 50 having the necessary irradiation opening shape (a triangle, a circle, an ellipse, a rectangle, etc.). Is done.

In FIG. 8, the circular collimator 4
Although the 0 and the ring bolus 44 are separate bodies, the ring bolus 44 may be embedded in the circular collimator 40 to be integrated as in the modification shown in FIG. FIG. 10 shows an example of a change in energy distribution after passing due to a difference in inner diameter of the ring boluses 44A and 44B, and FIG. 11 shows an example of a combined energy distribution.

The shape of the dose distribution given by one irradiation, which is determined by the plan, may directly match a part of the target shape, or may be made to coincide with the target shape as a result of superposition of a plurality of irradiations. You may.
In the latter case, the shape of the dose distribution given for each irradiation does not necessarily have to coincide with a part of the target shape.

Here, an example of treatment in the case where the shapes match each time will be described.

As shown in FIG. 12, target shape data and a manual division or automatic division algorithm are input from the operation terminal 52 to the ring bolus / collimator control device 54.

The ring bolus / collimator controller 5
4 is a target shape data storage memory 56 for storing target shape data inputted from the operation terminal 52.
According to the target shape data input from the target shape data storage memory 56 and the manual division or automatic division algorithm input from the operation terminal 52,
A target three-dimensional splitting device 58 for three-dimensionally splitting the target, a split target projected shape calculating device 60 for calculating the projected shape of the split target based on the output of the target three-dimensional splitting device 58, and a split target projected shape calculating device A collimator pattern output device 62 that outputs a signal for switching the geometrical collimator 50 to a required collimator pattern based on the output of the collimator pattern control device 70 and a ring bolus pattern included in the ring bolus mechanism 42. A ring bolus pattern storage memory 64 for storing, a split target irradiation energy distribution determining device 66 for determining an irradiation energy distribution of the split target based on the output of the ring bolus pattern storage memory 64 and the target three-dimensional splitting device 58; The division Getto in accordance with the output of the irradiation energy distribution determination device 66, as required ring bolus pattern is obtained, the ring bolus drive mechanism 46A~
And a ring bolus pattern output device 68 for outputting a signal for driving 46E to the ring bolus control device 72.

Hereinafter, the procedure of the radiotherapy operation using the above embodiment will be described with reference to FIG.

In the irradiation data calculation process 200 in the treatment plan, the restored three-dimensional affected part shape is read from the X-ray CT image in step 210, and the affected part shape is restored as three-dimensional data in step 220. Then, in step 230,
An irradiation area according to the present invention is determined from the restored three-dimensional shape. Next, at step 240, a combination pattern of ring boluses for reproducing an elliptical surface (how many ring boluses having an inner diameter, how many thicknesses are used, and how many are used) is calculated. Next, at step 250, a collimator pattern for limiting the irradiation area is calculated. Finally, at step 260, gantry position data is calculated.

Next, before proceeding to the actual irradiation, the process proceeds to the alignment process 300, in which the gantry position is read in step 310, the position of the patient is read in step 320, and the initial position of the gantry is calculated in step 330.

In the radiation irradiation processing 400, the gantry position is moved in step 410 based on the calculated data, a bolus pattern and a collimator pattern are set in step 420, and irradiation is performed in step 430. Steps 410 to 430 are performed for each irradiation direction until it is determined in step 440 that irradiation of all gates is completed. After irradiation of all gates, the irradiation is stopped in step 450.

In the present embodiment, a ring bolus drive mechanism is provided to automate the entry and exit of the ring bolus. Therefore, conventionally, a correction tool which has been created for each irradiation direction and which has been replaced every time the irradiation direction changes is used. Since there is no need for manual replacement and the irradiation direction can be changed quickly,
Treatment can be performed with less burden on the patient. Note that the ring bolus can be manually moved in and out.

In the present embodiment, the ring bolus is formed in a circular shape and is pulled out in one direction, so that the number of ring bolus drive mechanisms may be small, and the cost and weight can be reduced. Note that, as in the modified examples shown in FIG. 14 and FIG. In these cases, the moving distance of the ring bolus is reduced, and the size of the gantry nozzle can be reduced.

Further, in this embodiment, since a plurality of ring boluses having different inner diameters and a geometrical collimator are combined, the configuration is simple. It is also possible to use a ring bolus having a variable inner diameter, or to combine a collimator having a shape other than a geometric shape. Further, the multi-leaf collimator shown in FIG. 4 may be used instead of the circular collimator or the geometrical collimator.

In this embodiment, since the thickness of the ring bolus is the same, the calculation is easy. It is also possible to change the plate thickness so that a required change in the dose in the depth direction can be obtained with a small number of sheets.

In the above embodiment, the present invention is applied to the proton beam therapy system. However, the application of the present invention is not limited to this. The radiotherapy system other than the proton beam, or a general radiation irradiation system. It is clear that the same can be applied to the above.

[0054]

According to the present invention, a radiation irradiation pattern can be implemented by combining radiation energy absorbing materials having simple shapes.

Therefore, as compared with a conventional treatment plan using a fixing mechanism such as a wedge filter, approximately three times
Since a dose distribution that reproduces a dimensional shape can be realized, the therapeutic effect is high in terms of protection of surrounding normal tissues, which is an original advantage of radiotherapy.

Further, in high-energy radiation therapy, time for creating a bolus for each patient is not required, and the waiting time until a patient bolus is created can be reduced, thereby speeding up the overall treatment. Therefore, the permissible range for changing the irradiation time per unit time is greatly increased, and a more advanced treatment plan is possible.

Further, no waste material as radioactive waste such as a correction tool prepared for each patient is generated, and there is no problem of disposal processing.

Further, the simplification of the irradiation pattern is also effective for speeding up the optimization process in the computer support of the treatment plan.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of proton beam therapy.

FIG. 2 is a flowchart showing a general radiotherapy operation procedure;

FIG. 3 is a block diagram showing an example of the radiotherapy system.

FIG. 4 is a plan view showing a configuration of a multi-leaf collimator conventionally used as a block collimator.

FIG. 5 is a perspective view showing the principle of energy distribution adjustment and irradiation field formation in proton beam therapy.

FIG. 6 is a cross-sectional view of the brain showing an outline of radiation therapy using a conventional energy distribution correcting device.

FIG. 7 is a sectional view of the same liver part.

FIG. 8 is a perspective view, including a partial block diagram, showing a configuration of an embodiment of an energy distribution adjusting mechanism according to the present invention.

FIG. 9 is a diagram showing a modification of the ring bolus used in the embodiment.

10 is a diagram showing an example of an energy distribution obtained by the ring bolus of FIG. 9 and a combination thereof.

FIG. 11 is a diagram showing an example of an energy distribution obtained by combining the ring boluses of FIG. 10;

FIG. 12 is a block diagram showing a configuration of an operation terminal and a ring bolus / collimator control device used in the embodiment.

FIG. 13 is a flowchart showing the procedure of a radiotherapy operation using the embodiment.

FIG. 14 is a perspective view showing a ring bolus divided into two and a driving mechanism thereof according to a modification of the present invention.

FIG. 15 is a perspective view showing a ring bolus divided into three parts and a driving mechanism thereof.

[Explanation of symbols]

 8 ... Patient 8C ... Tumor 8H ... Head 8L ... Liver 10 ... Radiation generator 12 ... Radiation transport device 14 ... Gantry nozzle 16 ... Radiation observation / adjustment mechanism 18 ... Radiation energy shape forming mechanism 40 ... Circular collimator 42 ... Ring bolus mechanism 44A to 44E ring bolus 46A to 46E ring bolus drive mechanism 50 geometrical shape collimator 52 operation terminal 54 ring bolus collimator control device 70 collimator control device 72 ring bolus control device

Claims (7)

[Claims] 1. A radiation energy distribution adjusting mechanism for adjusting the energy distribution of irradiated radiation to an arbitrary shape, comprising a plurality of ring boluses made of a radiation energy absorber and having at least different inner diameters. Ring bolus group, ring bolus insertion means for inserting each ring bolus into the radiation irradiation path according to the required depth direction dose of the passed radiation, and according to the required planar dose distribution And a collimator for shielding radiation to an unnecessary irradiation area. 2. The radiation energy distribution adjusting mechanism according to claim 1, wherein the plurality of ring boluses have mutually different inner diameters. 3. The radiation energy distribution adjusting mechanism according to claim 1, wherein the inner diameters of the plurality of ring boluses are variable. 4. A radiation energy distribution adjusting mechanism according to claim 1, wherein said plurality of ring boluses are divided in a circumferential direction. 5. The radiation energy distribution adjusting mechanism according to claim 1, wherein the radiation irradiation opening of the collimator has a simple geometric shape. 6. A radiation irradiating method comprising irradiating radiation of an arbitrary shape using the radiation energy distribution adjusting mechanism according to any one of claims 1 to 5. 7. A radiation irradiating apparatus for irradiating radiation of an arbitrary shape, wherein the radiation energy distribution adjusting mechanism according to any one of claims 1 to 5, and a ring bolus in the energy distribution adjusting mechanism. A ring bolus drive mechanism for automatically entering and exiting according to the required depth-wise arrival dose of the passed radiation, and a radiation irradiating device comprising: