JP4159229B2 - Radiation energy distribution adjusting mechanism and radiation irradiation apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, radiation energy distribution adjustment mechanism, and relates to a radiation irradiation equipment using the same, irradiation particularly suitable for use in clinical proton therapy systems, for example towards the affected area from the outside of the patient the energy distribution of the radiation, the energy distribution control mechanism of radiation to adjust the arbitrary shape, and to a radiation irradiation equipment using the same.
[0002]
[Prior art]
X-rays, electron beam, neutron beam, proton beam, pion beam, heavy particle beam, etc. generated by accelerating charged particles at high speed and high energy in vacuum by particle accelerator, or γ from cobalt teletherapy device External radiation therapy in which a lesion or the like is irradiated percutaneously from the outside of a patient's body is an important therapeutic method together with surgery in the treatment of solid cancer. In particular, since the damage to normal tissues around the affected area can be reduced, it is considered that the demand will increase more and more in the future medical field where the quality of life (QOL) of patients is important.
[0003]
In this radiotherapy by external irradiation, it is important to avoid surrounding normal tissues or important organs and to give an irradiation dose distribution that matches the shape of the affected part as accurately as possible to the affected part. As shown in FIG. 1, the proton beam treatment utilizes the property that a proton beam incident on a substance gives a maximum dose at the Bragg peak P immediately before stopping, so that only cancer tissue is covered by the Bragg peak P. By doing so, this ideal is to be realized.
[0004]
In the radiation therapy operation, as shown in FIG. 2, first, in step 100, an X-ray CT image of the affected part is taken. On the basis of the photographed image, in step 110, a treatment plan is made in consideration of the patient's body contour, the affected area, and surrounding important organs. Based on the number and direction of irradiation gates and the radiation intensity determined in this treatment plan, in step 120, selection and processing of a fixing aid for fine adjustment of the radiation to be irradiated are performed. Next, in step 130, after the patient is positioned 132, irradiation treatment by irradiation 134 is performed.
[0005]
FIG. 3 shows the configuration of the radiation therapy system. In this radiotherapy system, radiation generated by a radiation generator 10 such as an accelerator is guided through a radiation transport device 12 to a gantry nozzle 14 for irradiating the 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 adjusts the radiation to an arbitrary energy distribution desired to be irradiated to the affected area. Irradiate from outside to the affected area. 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.
[0006]
That is, the radiation obtained from the accelerator, for example, a proton beam, has a thin beam shape, and its energy (the depth of the Bragg peak P) is also constant. On the other hand, cancer tissue has various sizes and complicated shapes, the depth in the body is not constant, and the density of the tissue through which the proton beam must pass is not uniform. Therefore, in order to perform proton beam treatment, the proton beam is expanded to (1) a wide beam that can be irradiated by the entire cancer at once, and (2) the energy is adjusted according to the depth of the cancer. (3) The energy distribution is given according to the thickness of the cancer so that the entire deep cancer tissue can be irradiated uniformly, and (4) the cancer contour and the non-uniformity of the tissue through which the proton beam passes It is necessary to make corrections accordingly.
[0007]
Therefore, in the conventional external radiation therapy, in order to compensate for the dose distribution in the patient body, the radiation energy shape forming mechanism 18 uses the skin surface of the irradiation site when the skin surface is not flat or the target to be irradiated is the skin surface. In the case of an inclination, an energy distribution correction device such as a compensation filter for compensating for distortion of the dose distribution has been used.
[0008]
As this compensation filter, for example, a wedge filter, which is a filter plate used in conventional radiotherapy, in which a spatial isodose curve of a passed beam has a certain inclination, or placed on the skin surface, the irradiation surface There are boluses that are used to flatten the irregularities. In recent heavy particle beam therapy, a treatment method for creating a patient bolus for reproducing the shape of an affected part from a plurality of irradiation directions for each patient to be treated has been attempted.
[0009]
Further, in the mechanism for finally adjusting the radiation to be irradiated, the energy distribution correction tool and the irradiation field shaping tool for shaping the irradiation field by shielding the area irradiated with unnecessary radiation are usually used at the same time. is there.
[0010]
For high-energy radiation, a block collimator that creates an irregularly shaped rectangular field by shielding unnecessary beam portions, as shown in FIG. A multi-leaf collimator that can be set to an irradiation field that matches the shape of the target to be irradiated by moving each rod-shaped collimator of about 1 cm, a plate that projects the shape of the affected area of the patient in the irradiation direction in advance, and the radiation does not pass through. There are patient collimators and the like that limit the irradiation field to the shape of the affected area by hollowing out the shape. The multi-leaf collimator is becoming standard equipment in recent high-energy radiation treatment apparatuses.
[0011]
Specifically, for example, in proton beam therapy, as shown in FIG. 5, an energy distribution that matches the shape of the irradiation target is formed. That is, the narrow proton beam 20 sent to the gantry nozzle 14 that is the irradiation unit is expanded in the lateral direction by a scatterer 22 made of lead having a thickness of several millimeters, for example, and expanded to a wide beam 24. To do. When a relatively uniform portion of 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 using a collimator described later, a treatment table below (not shown) In the above, an irradiation field having a diameter of several tens of centimeters necessary for treatment is obtained.
[0012]
The expanded beam 24 is incident on a fine degrader 26 for adjusting the maximum reach depth of the proton beam according to the depth of the treatment target (for example, the tumor 8C in the patient 8). The fine degrader 26 is composed of, for example, two wedge-shaped opposing acrylic blocks 26a and 26b. By adjusting the overlapping of the blocks 26a and 26b, the thickness of the portion through which the proton beam passes is continuously formed. Can be changed. The proton beam loses energy according to the thickness of the substance that has passed through, and the reachable depth changes. Therefore, by adjusting the fine degrader 26, the Bragg peak P shown in FIG. Can be matched.
[0013]
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 column-shaped metal rod whose thickness changes stepwise, and is arranged in a bowl shape. Proton beams that have passed through portions having different thicknesses form Bragg peaks P at different depths. By adjusting the width and height of the stairs, the peak width ΔP can be expanded by appropriately overlapping them.
[0014]
The proton beam that has passed through the ridge filter 28 is incident on a block collimator 30 for roughly shaping the planar shape of the proton beam. In addition to the final collimator described later, the reason why the block collimator 30 performs shaping is to prevent secondary radiation from being generated by the block collimator near the patient 8.
[0015]
The proton beam that has passed through the block collimator 30 is input to a bolus 32 that is, for example, a resin-made irregular filter, and correction is performed regarding the cross-sectional shape of the maximum depth of the tumor 8C and the tissue non-uniformity. The shape of the bolus 32 is calculated based on the outline of the tumor 8C and the electron density of the surrounding tissue obtained from, for example, X-ray CT data.
[0016]
The proton beam that has passed through the bolus 32 is incident on a final collimator 34 such as brass, and after final adjustment is made in accordance with the contour of the planar shape of the tumor 8C, the proton beam is irradiated to the patient 8 as a therapeutic proton beam 36. Is done.
[0017]
An outline of conventional radiation therapy using the energy distribution adjusting mechanism as described above is shown in FIGS. FIG. 6 is an example of X-ray irradiation in which a dose distribution D is formed on the patient's head 8H using the wedge filter 33. FIG. FIG. 7 shows an example of proton beam orthogonal double irradiation on the liver 8L of the patient. In this example, a patient bolus 32 corresponding to the affected part shape of the patient is processed and used to obtain a dose distribution D concentrated on the affected part shape. In these two examples, the energy distribution adjusting mechanism is fixed with respect to the irradiation direction.
[0018]
Moreover, the conventional treatment plan has performed the combination of the above-mentioned energy distribution correction apparatus on a trial and error basis based on an empirical rule. The same applies to the treatment plan in the heavy ion beam treatment, and an improvement in the irradiation method has been desired in order to further improve the treatment effect and treatment speed.
[0019]
[Problems to be solved by the invention]
That is, the radiation energy distribution adjusting mechanism of the conventional radiotherapy system has the following problems in terms of treatment efficiency.
[0020]
(1) Since the irradiation pattern is configured only by a combination of relatively simple correction tools, the mechanical limitation is large for irradiation that avoids a complicated affected part shape and an important organ. In particular, when a highly transparent radiation quality such as a proton beam or heavy particle beam is used, even a multi-leaf collimator cannot be used for a small tumor.
[0021]
(2) Both the dose distribution correction tool and the irradiation field shaping tool are fixed at the time of radiation irradiation, and when it is desired to give different irradiation patterns, the correction tool must be re-equipped for each irradiation.
[0022]
(3) When a correction tool created for each treatment such as a patient bolus is used, there is a problem in the creation time and cost of the correction tool.
[0023]
(4) When a correction tool is created for each treatment, the correction tool once used becomes a radioactive waste, so that it is difficult to handle when it is discarded.
[0024]
The present invention has been made to solve the above-mentioned conventional problems, and a first object is to realize a three-dimensional dose distribution according to the shape of an affected part in a patient body without replacing a correction tool. To do.
[0025]
The second object of the present invention is to reduce the burden on the patient by improving the accuracy of radiotherapy and reducing the actual irradiation time.
[0026]
[Means for Solving the Problems]
The present invention relates to a radiation energy distribution adjusting mechanism for adjusting the energy distribution of irradiated radiation to an arbitrary shape, for correcting the cross-sectional shape of the maximum depth of the affected part , which is created by the radiation energy absorber . A group of plate boluses composed of a plurality of plate boluses, a plate bolus slide means for inserting each plate bolus into the radiation irradiation opening according to the required depth direction arrival dose of the passed radiation, and necessary plane According to the dose distribution, the first problem is solved by providing a collimator for shielding radiation to an unnecessary irradiation region.
[0027]
In addition, the plate bolus can be slid in one direction to realize a dose distribution having a curved surface whose curvature changes in a single direction.
[0028]
Alternatively, the plate bolus can be slid in two directions, and a dose distribution having an upwardly convex curved surface can be realized.
[0029]
Alternatively, the two plate boluses are provided and slidable in directions orthogonal to each other so that a dose distribution having a downwardly convex curved surface can be realized.
[0031]
Moreover, in the radiation irradiation apparatus for irradiating radiation of an arbitrary shape, the radiation energy distribution adjusting mechanism and the plate bolus in the energy distribution adjusting mechanism are automatically set according to the required dose distribution in the depth direction. by providing a plate bolus drive mechanism for entering and exiting is obtained by solving the previous SL second problem.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0033]
As shown in FIG. 8, the first embodiment of the radiation energy distribution adjusting mechanism according to the present invention has a simple radiation irradiation aperture instead of the slide bolus mechanism 40 instead of the patient bolus 32 and the final collimator 34 shown in FIG. And a geometrical collimator 50 having a simple geometric shape (here, a triangle).
[0034]
In addition, a multi-leaf collimator, a patient collimator, or the like can be used in combination depending on the treatment grade.
[0035]
The slide bolus mechanism 40 is made of a radiation energy absorber, for example, a plate bolus group 42 made up of a large number of plate boluses 44A to 44J having the same thickness, and the tip of each plate bolus 44A to 44J. As shown in FIG. 9, plate bolus slide mechanisms 46A to 46J (only 46A is shown in FIG. 9) and the plate boluses 44A to 44J are automatically inserted in accordance with the required dose in the depth direction. For example, as shown in FIG. 9, plate bolus drive mechanisms 48A to 48J (FIG. 9 only shows 48A), and an energy distribution that can be reproduced by a combination of the plate bolus group and a collimator. In response to an instruction from the operation terminal 52 to irradiate the divided target A plate bolus for sliding the plate boluses 44A to 44J in one direction by a necessary amount as shown by an arrow A in FIG. 8 or replacing the geometric collimator 50 with a geometric collimator having another opening shape. And a collimator control device 54.
[0036]
The plate boluses 44 </ b> A to 44 </ b> J are slid so that the arrival dose in the depth direction of the passed radiation becomes, for example, a monotonous increase / decrease curvature curved surface.
[0037]
The gantry nozzle 14 including the slide bolus mechanism 40 and the geometrical collimator 50 is rotatable relative to the patient (rotating the gantry nozzle and / or patient bed) as indicated by an arrow B in FIG.
[0038]
The slide bolus mechanism 40 and the geometrical collimator 50 are designed so that, when a treatment plan is performed in advance so that the three-dimensional affected part shape can be entirely covered with a combination of a part of a monotonous increase / decrease curvature surface, It operates so as to have a radiation energy distribution that forms a dose distribution on an increasing / decreasing curvature surface.
[0039]
Alternatively, an irradiation pattern optimized based on a certain evaluation criterion is used.
[0040]
Here, the evaluation criteria may include a dose in the target, uniformity thereof, influence on surrounding normal tissue, a result based on DVH (dose volume histogram), and the like. Note that each of the irradiation patterns obtained by the optimization does not necessarily coincide with a part of the target shape directly.
[0041]
Specifically, the energy distribution of the incident radiation is adjusted by the plate bolus group 42 as shown in FIG. That is, when the radiation is uniformly incident on the whole part of the plate bolus group 42 from the vertical direction, the radiation that has passed through the plate bolus group is absorbed uniformly by each plate bolus, and thus the patient. There is a difference in the radiation reach distance after entering the body. Here, if attention is paid only to an isoenergetic line or energy peak of the irradiated radiation and this is expressed as an energy distribution, the energy on the monotonous increase / decrease curvature surface corresponding to the slide amount of the plate bolus as shown in FIG. A distribution E is formed. Further, the radiation for the unnecessary irradiation region is cut out by a geometric collimator 50 having a necessary opening shape (in addition to a triangle, a circle, an ellipse, a rectangle, etc.), and the gantry nozzle 14 is shown by an arrow B in FIG. By rotating in the -Y plane, the planned dose distribution D is finally formed in the patient.
[0042]
The shape of the dose distribution given by one irradiation determined by the plan may directly coincide with a part of the target shape, or may coincide with the target shape as a result of superimposing a plurality of irradiations. . In the latter case, the shape of the dose distribution given for each irradiation does not necessarily match a part of the target shape.
[0043]
Here, an example of treatment when the shapes for each time match will be described.
[0044]
From the operation terminal 52, as shown in FIG. 11, target shape data and manual division or automatic division algorithm are input to the slide plate / collimator controller 54.
[0045]
The slide plate / collimator control device 54 stores a target shape data storage memory 56 for storing target shape data input from the operation terminal 52 and a bolus pattern that can be realized by the plate bolus group 42 of the slide bolus mechanism 40. Slide bolus pattern memory 58, target shape data inputted from the target shape data storage memory 56, manual division or automatic division algorithm inputted from the operation terminal 52, and bolus inputted from the slide bolus pattern memory 58 A target three-dimensional dividing device 60 that three-dimensionally divides the target according to a pattern, and a divided target projected shape calculating device that calculates the projected shape of the divided target based on the output of the target three-dimensional dividing device 60 2 and a collimator pattern output device 62 for outputting to the collimator control device 70 a signal for switching the geometric collimator 50 so as to obtain a necessary collimator pattern based on the output of the divided target projection shape calculation device 62; Based on the output of the target three-dimensional dividing device 58, a divided target curved surface quantization device 66 that quantizes the curved surface of the divided target, and a necessary bolus pattern is obtained according to the output of the divided target curved surface quantization device 66. As described above, the slide bolus pattern output device 68 is configured to output a signal for driving the plate bolus drive mechanisms 48A to 48J to the slide bolus control device 72.
[0046]
Hereinafter, with reference to FIG. 12, the procedure of the radiotherapy operation | work using the said embodiment is demonstrated.
[0047]
In the irradiation data calculation process 200 in the treatment plan, the three-dimensional affected part shape restored from the X-ray CT image in Step 210 is read, and in Step 220, the affected part shape is restored as three-dimensional data. Next, in step 230, an irradiation area according to the present invention is determined from among the restored three-dimensional shape. Next, in step 240, a combination pattern of plate boluses for reproducing a monotonous increase / decrease curvature surface (which plate bolus is slid how much) is calculated. Next, in step 250, a collimator pattern for limiting the irradiation area is calculated. Finally, in step 260, gantry position data is calculated.
[0048]
Next, before proceeding to the actual irradiation, the process proceeds to the alignment process 300, where the gantry position is read in step 310, the patient position is read in step 320, and the initial position of the gantry is calculated in step 330.
[0049]
In the radiation irradiation process 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 the entire gate irradiation has been completed. After the whole gate irradiation is completed, the irradiation is stopped in step 450.
[0050]
In this embodiment, a plate bolus drive mechanism is provided to automate the entry and exit of the plate bolus, so that a correction tool that has been created for each irradiation direction and replaced every time the irradiation direction changes is manually replaced. Is unnecessary, and the irradiation direction can be changed quickly, so that treatment with less burden on the patient can be performed. It is also possible to manually slide the plate bolus.
[0051]
In this embodiment, since the rectangular plate bolus is slid in one direction using the plate bolus slide mechanism having one degree of freedom, the configuration is simple. As in the second embodiment shown in FIG. 13, plate bolus drive mechanisms 49A to 49J (here, only 49A is shown) for moving the plate bolus in two directions (two directions orthogonal here) are provided. Each plate bolus can be slidable in two directions. When this two-degree-of-freedom plate bolus slide mechanism is used, as shown in FIG. 14, it is possible to realize a dose distribution having an upwardly convex curved surface having a curvature change.
[0052]
Alternatively, as in the third embodiment shown in FIG. 15, another plate bolus group 43 is added, two plate boluses of the same height are used, and a plate bolus slide mechanism with 1 + 2 degrees of freedom is used. As shown in FIG. 16, it is also possible to realize a dose distribution having a downwardly convex curved surface with a change in curvature so that each plate bolus forms an L-shaped opening. FIG. 17 shows the planar shape of the energy distribution in this case.
[0053]
Furthermore, an L-shaped plate bolus in which two plate boluses of the same height in the third embodiment are integrated may be provided so as to be movable in two directions.
[0054]
Moreover, in the said embodiment, since the thickness of each plate bolus is made the same, calculation is simple. It is also possible to change the thickness of the plate bolus to reduce the number of plates and simplify the configuration.
[0055]
Moreover, in the said embodiment, since a slide bolus mechanism and a geometric shape collimator are combined, a structure is simple. It is also possible to combine collimators having shapes other than geometric shapes, or to combine the multi-leaf collimator shown in FIG.
[0056]
In the above embodiment, the present invention has been applied to a proton beam treatment system, but the application target of the present invention is not limited to this, and also to a radiation treatment system other than a proton beam, or a general radiation irradiation system, Obviously, the same applies.
[0057]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the irradiation pattern of the radiation which has a curvature surface of a monotonous increase / decrease is realizable with the combination of radiation energy absorption material of a simple shape.
[0058]
Therefore, compared to the conventional treatment plan using a fixed mechanism such as a wedge filter, a dose distribution that approximately reproduces a three-dimensional shape using a monotonous increase / decrease curvature surface can be realized. The therapeutic effect is high in terms of protecting normal tissues.
[0059]
Also, in high energy radiation therapy, it is not necessary to create a bolus for each patient, and the waiting time until a patient bolus is created can be reduced to speed up the overall treatment. Therefore, the allowable range of change in irradiation time per unit time is greatly increased, and further advanced treatment planning is possible.
[0060]
In addition, no waste material that becomes radioactive waste such as a correction tool created for each patient is generated, and the problem of disposal processing does not occur.
[0061]
Furthermore, simplification of the irradiation pattern is 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 treatment. FIG. 2 is a flowchart showing a general radiation treatment work procedure. FIG. 3 is a block diagram showing an example of a radiation treatment system. FIG. Fig. 5 is a plan view showing the configuration of a multi-leaf collimator used. Fig. 5 is a perspective view showing the principle of energy distribution adjustment and irradiation field formation in proton beam treatment. Fig. 6 is a diagram of radiation therapy using a conventional energy distribution correction device. Fig. 7 is a schematic cross-sectional view of the brain. Fig. 7 is a cross-sectional view of the liver. Fig. 8 is a perspective view including a partial block diagram showing the configuration of the first embodiment of the energy distribution adjusting mechanism according to the present invention. 9 is a plan view showing the configuration of a one-degree-of-freedom plate bolus slide mechanism used in the first embodiment. FIG. 10 is a perspective view showing an example of energy distribution realized by the first embodiment. FIG. 12 is a block diagram showing the configuration of an operation terminal and a slide plate / collimator control device used in the first embodiment. FIG. 12 is a flowchart showing a procedure of radiation therapy work using the first embodiment. FIG. 14 is a plan view showing the configuration of a two-degree-of-freedom plate bolus slide mechanism used in the second embodiment of the energy distribution adjusting mechanism according to FIG. 14 is a perspective view showing an example of energy distribution realized by the second embodiment. 15 is a perspective view showing the configuration of the main part of a plate bolus slide mechanism with 1 + 2 degrees of freedom used in the third embodiment of the energy distribution adjusting mechanism according to the present invention, and an example of the energy distribution realized thereby. FIG. FIG. 17 is a plan view showing an example of the arrangement of plate boluses according to the third embodiment. FIG. 17 is a plan view showing an example of energy distribution.
DESCRIPTION OF SYMBOLS 8 ... Patient 8C ... Tumor 8H ... Head 8L ... Liver 10 ... Radiation generator 12 ... Radiation transport device 14 ... Gantry nozzle 15 ... Irradiation opening 16 ... Radiation observation and adjustment mechanism 18 ... Radiation energy shape formation mechanism 40 ... Slide bolus mechanism 42, 43 ... Plate bolus group 44A-44J ... Plate bolus 46A-46J ... Plate bolus slide mechanism 48A-48J, 49A-49J ... Plate bolus drive mechanism 50 ... Geometric shape collimator 52 ... Operation terminal 54 ... Slide plate collimator control device 70 ... Collimator control device 72 ... Slide bolus control device

Claims (6)

In the radiation energy distribution adjustment mechanism for adjusting the energy distribution of the irradiated radiation to an arbitrary shape,
A plate bolus group composed of a plurality of plate boluses for correcting the cross-sectional shape of the maximum depth of the affected area , which is made of a radiation energy absorber,
Plate bolus slide means for inserting each plate bolus into the radiation irradiation opening according to the required depth direction arrival dose of the passed radiation,
A collimator for shielding radiation to unwanted irradiation areas according to the required planar dose distribution;
A radiation energy distribution adjustment mechanism characterized by comprising:   The radiation energy distribution adjusting mechanism according to claim 1, wherein the plate bolus is slidable in one direction.   The radiation energy distribution adjusting mechanism according to claim 1, wherein the plate bolus is slidable in two directions.   The radiation energy distribution adjusting mechanism according to claim 1, wherein two plate boluses are provided and slidable in directions orthogonal to each other.   The radiation energy distribution adjusting mechanism according to claim 1, wherein a radiation irradiation opening of the collimator has a simple geometric shape. In radiation SenTeru morphism apparatus for applying radiation having an arbitrary shape,
A radiation energy distribution adjusting mechanism according to any one of claims 1 to 5,
A plate bolus driving mechanism for automatically entering and exiting the plate bolus in the energy distribution adjusting mechanism in accordance with a necessary depth direction arrival dose of the passed radiation;
Radiation SenTeru morphism apparatus characterized by comprising a.

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