JPH10314323A - Irradiation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an irradiation as planned by arranging a fifth process for switching a layer with which a particle ray beam is irradiated at a timing determined by a fourth process to previously clarify a distribution of a dose irradiated to an affected part at a planning stage, which enables setting of the parameters for an apparatus corresponding to the distribution of the dose. SOLUTION: Irradiation is started (S101) and a dose of an integral monitor is always read out during the irradiation to a certain split layer (S102) to be always compared with a projected monitor dose used in the subsequent procedure (S103). When the dose of the integral monitor reaches the projected monitor dose, immediately, with the altering of setting in the execution of a fixed procedure, for example, an irradiation to the subsequent split layer is carried out. (S104) The monitor returns to the dose monitoring mode again and repeated up to the end of the irradiation. (A106) In the supervising of the integral monitor, fast repeated reading therefrom must be done but in stead, preset sealers or the like can be used if necessary and an interrupt processing is carried out according to the values on the dose monitored by a control calculator thereby getting rid of useless reading loop.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an irradiation method for irradiating an affected part three-dimensionally with radiation (mainly charged particle beams).

[0002]

2. Description of the Related Art Radiotherapy is performed by irradiating an affected part with radiation. The target area is a region where a high dose is to be given (irradiation) centered on the affected area, and in order to make the distribution of the dose (biological dose) given to each point of the patient ideal from the medical requirements of radiation therapy, In general, it is ideal to provide a uniform dose inside the target and minimize the dose outside the target.

In conventional radiotherapy using charged particle beams, various devices are used to transform a particle beam (charged particle beam) from an accelerator into a particle beam conforming to the shape of a target. FIG. 16 shows the configuration of a particle beam therapy system used in a general two-dimensional irradiation method.

[0006] In FIG. 16, the irradiation area of a fine and single energy particle beam 1 accelerated by an accelerator (not shown) is expanded by a beam expansion device 2 in a direction perpendicular to the irradiation direction of the particle beam 1. And particle beam 1
Is adjusted to the irradiation shape of the target 6 in the patient 5 fixed to the patient fixing device 4 by the irradiation field forming device 3 as irradiation range forming means.

[0005] The dose characteristics of the particle beam irradiated to the patient 5 in the depth direction in the body are determined by a range modulator 7, a range adjuster 8, and a range compensator (bolus), as described later in detail. 9 conforms to the shape of the target 6. The operation control and monitoring of these various devices of the radiation therapy apparatus are performed by the control computer 12.

[0006] The number of particles of the particle beam 1 irradiated to the patient 5 is monitored by the dose monitor 10 at a stage before the irradiation to the patient 5, and a predetermined specified dose is applied to the dose monitor 1.
When 0 is measured, the irradiation of the particle beam 1 is stopped based on the control signal from the beam control mechanism 11.

Here, the incident particle beam 1 is applied to the scatterer 1 by a beam expanding device 2 for producing a flat particle intensity (that is, a uniform particle distribution) in the irradiation field of the particle beam 1.
3 is a single scatterer method that spreads Gaussian distribution (FIG. 17)
(A)) The particle beam 1 scattered by the scatterer 13 is further scattered by the scatterer 14 arranged concentrically with the scatterer 13 to add strong scattering to the vicinity of the concentric portion to improve the flatness. Body method (FIG. 17 (b)), the phase is 9 at the same frequency
Alternating currents, which are shifted by 0 degrees, respectively, rotate the incident particle beam 1 around the particle beam axis by two sets of electromagnets 15 and 16 which deflect the incident particle beam 1 in directions orthogonal to each other. In addition, there is a Wobbler method of scattering by the scatterer 13 (FIG. 17C).

The irradiation field forming device 3 for adjusting the irradiation field of the particle beam 1 to the projection shape of the target 6 includes:
As shown in FIG. 18, a multi-leaf collimator in which the rotation angle around the particle beam axis can be freely changed, and the shape of the irradiation field can be freely changed by sliding a leaf composed of a number of stacked metal plates. Alternatively, a fixed-shaped patient collimator uniquely created for each target 6 is already known and used.

The patient-fixing device 4 is generally a so-called bed-type or chair-type treatment table, and the treatment table on which the patient 5 is fixed is moved and rotated by driving an electromagnetic motor (not shown). .

Generally, there are a plurality of dose monitors 10 for monitoring and measuring the dose to be irradiated, and there is a case where the flatness of the particle beam 1 to be irradiated is monitored.

Beam control mechanism 1 for controlling beam irradiation
A method 1 uses a mechanical shutter, a method of stopping the extraction of the particle beam 1, a method of discarding the particle beam 1 to a place where there is no problem, and the like.

Next, a range modulation device 7 and a range adjustment device 8
Will be described. Regarding the incident direction in which the particle beam 1 reaches, the reach (range) of the particle beam 1 in the substance
Is determined by the energy, and the particle beam 1 traveling in a substance has the property that it stops traveling in the substance and gives the strongest dose immediately before reaching.

The dose characteristic of the particle beam 1 having a single energy is as shown in FIG. 19A, and the high dose portion immediately before the stop of the particle beam 1 stops at the peak portion. The flat low dose portion before the peak portion is called a plateau portion, and the low dose portion attenuated after the peak portion is called a tail portion. Here, the reaching depth of the particle beam is defined by the amount of the substance that the particle beam passes, that is, the density × the distance.

In order to adjust the dose distribution characteristics of the particle beam in the depth direction of arrival to the thickness of the target, a range adjusting device 8 is used.
To adjust the depth of arrival of the particle beam in the body by using, and expand and flatten the peak part, which is the high-dose region, by using the range modulation device 7 to obtain an appropriate energy distribution for the particle beam. To have.

As the range modulation device 7, a ridge filter or the like as shown in FIG. 20 is used. This is to change the amount of energy attenuation depending on the position at which particles pass through the wedge by the fine wedge-shaped additional substance. Range modulation device 7
FIG. 19B shows the dose characteristics when the peak portion of the particle beam is expanded and flattened using the method shown in FIG. 19B. This portion is referred to as an expanded SOBP (Spred Out).
Bragg Peak).

A range adjusting device 8 for adjusting the in-vivo range of the particle beam, that is, the reaching depth (hereinafter referred to as the range) to adjust the peak portion to the in-body depth of the target is provided with a pair of devices. An analog range shifter which is composed of wedge-shaped blocks and adjusts the thickness of an additional material by simultaneously taking them in and out (FIG. 21)
(A)), a digital range shifter for adjusting the thickness of an additional material by inserting an arbitrary number of plates having the same thickness (FIG. 2)
1 (b)), the thinnest plate is set as the reference plate thickness, twice as large,
A binary range shifter (Fig. 21 (c)) that adjusts the additional material thickness using a combination of plates with thicknesses of 8 times, 16 times, and 2 powers (Fig. 21 (c)), and controls the accelerator to reduce the energy of the particles. Variable acceleration energy type that adjusts the range without changing the material thickness by directly changing (Fig. 21 (d))
There is.

These range adjusting devices 8 have the following features. The use of an analog range shifter enables a range adjustment with a high degree of freedom, but in order to change the set value, it is necessary to accelerate and decelerate the wedge-shaped block with high speed and high accuracy. Since the digital range shifter can be set only in fixed steps, the degree of freedom of the set value is reduced, but the range can be adjusted with high precision and the control is relatively simple. The binary range shifter has the same features as the digital range shifter, but the number of plates to be moved when changing the depth changes instead of reducing the total number of plates.

The range compensator 9 created for each treatment in accordance with the shape of the target 6 is formed of, for example, a plastic resin in order to correct the position dependence of the depth of the target 6 in the irradiation field. The range of the body is adjusted by changing the thickness of a plate-like object depending on the position.

Normally, the shape of the range compensator 9 is such that the surface formed by the end on the deep side in the body of the peak portion of the dose matches the shape of the half surface on the deep side of the target 6. The dose distribution produced by the two-dimensional irradiation method is as shown in FIG.

[0020]

In such conventional radiotherapy, two-dimensional irradiation is performed, and the dose distribution in the body depth direction is the same in the irradiation field, and the high dose region is the same in the depth direction. Will have a thickness. Therefore, for an actual target having a three-dimensional shape (variable in thickness), it is ideally desirable to create a dose distribution according to the shape. Unnecessarily high doses will be applied to the area.

In order to produce an ideal dose distribution by two-dimensional irradiation, it is necessary to rely on multiport irradiation in which the irradiation direction, irradiation center position and the like are variously changed, and the treatment plan and treatment control become complicated. . Reducing the number of irradiation gates and simplifying treatment is important for efficient treatment facility operation.

The present invention has been made in order to solve the above-mentioned problems, and has clarified in advance a three-dimensionally formed dose distribution for irradiating an affected part at a planning stage of irradiation, and has been adapted to the dose distribution. It is an object of the present invention to provide an irradiation method capable of setting parameters of devices and performing irradiation as planned.

[0023]

According to the present invention, there is provided an irradiation method, comprising: a dividing interval for dividing a target into layers based on a range of a high-dose region of a particle beam irradiated from a beam irradiating apparatus. A first step of defining the target, a second step of dividing the target into layers based on the division intervals determined in the first step, and a predetermined dose and a height of the particle beam irradiated to the entire target. A third step of obtaining a dose to be applied to each of the layers divided in the second step based on the intensity of the beam corresponding to the dose region portion, and a predetermined step in the layers divided in the second step. A fourth step of determining the timing at which the intensity of the particle beam irradiated to the layer that has been irradiated reaches the predetermined dose irradiated to the layer determined in the third step, and a step between the beam irradiation apparatus and the target. Placed in The irradiation range in the direction orthogonal to the lamination direction of the layers is determined for each layer to be irradiated with the particle beam by the irradiation range forming means, and the beam is irradiated by the beam irradiation device at the timing obtained in the fourth step. And a fifth step of switching a layer to be irradiated with the beam.

A first step of determining a division interval for dividing the target into layers based on a range of a high-dose region of the particle beam irradiated to the target from the beam irradiation apparatus; A second step of dividing the target into layers at regular intervals along the shape of the body surface on which the particle beam is incident, based on the division interval determined in the above, and a predetermined dose applied to the entire target A third step of determining a dose to be applied to a unit area in each of the layers divided in the second step based on the beam intensity corresponding to a high-dose area portion of the particle beam, and a second step At which the intensity of the particle beam irradiated to the predetermined layer in the layers divided by the step reaches the dose irradiated to the unit area in the predetermined layer determined in the third step The fourth step of finding The irradiation range in the direction orthogonal to the layer stacking direction is determined for each unit area irradiated with the particle beam by the irradiation range forming means arranged between the beam irradiation device and the target, and the beam is irradiated by the beam irradiation device. ,
And a fifth step of switching a unit area to be irradiated with the particle beam based on the timing obtained in the fourth step.

The fifth step is a step in which the multi-leaf collimator constituting the irradiation range forming means waits in front of the range where the beam is irradiated with all the leaf pairs closed,
Simultaneously moving all the leaves on one side of the leaf pair and opening the multi-leaf collimator by an amount corresponding to the range to be irradiated, and starting the irradiation of the beam to the range to be irradiated, and reaching the timing for each range to be irradiated Moving the leaf on the other side of the leaf pair at the time to close the multi-leaf collimator and stop the irradiation of the beam to the irradiated area.

The fifth step is a step in which the multi-leaf collimator constituting the irradiation range forming means waits in front of the range where the beam is irradiated in a state where all the leaf pairs are closed; Simultaneously moving all the leaves on the side and opening the multi-leaf collimator by an amount corresponding to the range to be irradiated, and starting irradiation of the beam to the range to be irradiated, and when the timing for each range to be irradiated is reached, the other side Move the leaves to stop irradiation to the area to be irradiated, move all leaf groups on one side simultaneously, open the multi-leaf collimator by the amount corresponding to the area to be irradiated next, and move to the area to be irradiated next. And starting the irradiation of the beam.

The timing is estimated from an approximate function obtained from a relationship between a plurality of predetermined unit areas and timings in the unit areas.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. In the irradiation method according to the first embodiment, the range of the beam is adjusted using the range compensator 9 so as to reach the shape of the surface of the target 6 opposite to the surface on which the beam is incident. Further, the target 6 is further divided into multiple layers (divided into layers having a constant thickness) at regular intervals (SOBP width described later) from the opposite surface.

Then, in consideration of the size of the SOBP width, a high-dose area portion (a region portion corresponding to the SOBP width) is irradiated to each of the affected area divided into multiple layers in consideration of the size of the SOBP width as described later. As described above, two-dimensional partial irradiation as in the conventional example is performed, and these beam irradiations performed on all of the affected area divided into multiple layers in this manner are superimposed to ideally apply to the affected area. Gives a close three-dimensional dose distribution. The method of realizing this will be described below.

In addition, not only in the first embodiment but also in other embodiments, regarding dose calculation for preparing an irradiation plan, only dose characteristics in the depth direction in the body are considered. Actually, the beam spreads in the horizontal direction due to the interaction with the substance inside or outside the body, but after the irradiation plan is created, it is sufficient to carry out calculation and study including those effects and correct the plan as necessary .

FIG. 1 is a flowchart showing the procedure of the irradiation method according to the first embodiment, which will be described with reference to FIG.
First, in the irradiation condition input stage, condition parameters necessary for subsequent calculations are input as shown below. After selecting a device to be used in the treatment device (step S11),
Determination (designation) of the thickness of a layer that divides the affected part into a number of layers with respect to the target 6 at a constant thickness, and a range modulation device 8 that gives a beam the SOBP width described later, which is the closest to the thickness of the layer. Is selected (step S12).

However, since the thickness of the layer is set to the step width of the range adjustment of the range adjusting device 8 for irradiating each divided layer, the thickness cannot be arbitrarily determined depending on the range adjusting device 8 to be used. However, the thickness of the layer to be divided as much as possible and this SOBP
It is desirable that the difference be as small as possible so that the widths match.

The three-dimensional irradiation is carried out by irradiating the target 6 for each divided layer while adjusting the equipment for each divided layer (for example, adjusting the range corresponding to each divided layer). In consideration of the possibility of temporal position fluctuation, irradiation of each of the divided layers is repeated a plurality of times. The repetition of this series of irradiation is called a sweep, and the number of times of sweeping (the number of times of repeated irradiation) is also given here (step S13). The order in which the target 6 is swept according to the division layer is also specified in step S13.

Here, the order of layers irradiated in a certain sweep may be different for each sweep, and may be performed in an efficient order in consideration of adjustment of equipment for each sweep. Usually, the irradiation area is moved to the next adjacent layer in order,
When one sweep is completed, a sweep is performed in the original reverse direction, and one reciprocation is performed with two sweeps.

In the next irradiation condition calculation step of calculating the dose given to each divided layer, setting parameters of various devices are calculated based on the conditions input in the previous irradiation condition input step.

As in the prior art, the range compensator 9 is used, for example, by a ray tracing method so that the beam reaches the surface of the target 6 opposite to the surface on which the beam is incident. A range compensator 9 formed in a concave shape corresponding to the shape of the surface on the opposite side is created.
21).

Next, in order to perform irradiation for each divided layer, the target 6 is divided into layers as described later (step S).
22). That is, the layer division of the target 6 will be described with reference to FIG. 2. The layer division of the target 6 is performed at regular intervals (SOBP width described later) from the surface opposite to the surface on which the beam is incident. The target 6 is divided into several layers (for example, six layers in FIG. 2) (layer division).

Then, the deepest part in the body from the body surface (the surface on the side where the beam is incident) is defined as the first divided layer, and it is counted toward the body surface in order and the side on which the beam of the target 6 is incident. The layer closest to the surface is defined as the final divided layer, and the number of divided layers is defined as N _SL .

The acceleration energy given to the beam is adjusted by an accelerator (not shown) so that the beam reaches the deepest part of the target 9 divided into layers in consideration of the fact that the beam passes through the range compensator 9. The adjustment is performed for each divided layer as in the above-described conventional example (step S23).

The adjustment of the range by the range modulator 7, that is, the enlargement of the SOBP width of the beam, which will be described later, is performed such that the high-dose region irradiates the divided layer to be irradiated as in the conventional example. The amount is determined (step S24).
The setting of the multi-leaf collimator, which is a beam expanding device or an irradiation field forming device, is adjusted so that an irradiation field is formed in each partial irradiation region according to the shape of the layer-divided region as in the conventional example. Determine the amount (Step S2
5).

For example, when the irradiation field is set by the above-described Wobbler method for setting the irradiation field, the above-described wobble current and the scatterer thickness in two directions are adjusted. Even in the case of the single or double scatterer method, an optimum setting for the target divided layer may be similarly selected.

The setting (opening setting) of the multi-leaf collimator as the irradiation field forming device 3 is also set so that the irradiation field becomes the area of the irradiation surface of the divided layer to be irradiated by the target 6 every time the beam is irradiated. (The opening degree of the multi-leaf collimator may be set).

For example, if the target dose distribution monotonically increases in the beam irradiation field with the physical depth (depth in the body) as shown in FIG. The desired dose distribution can be obtained by adjusting the depth of the body within the range by using the method and adjusting the size of the irradiation field by using a multi-leaf collimator.

Here, when the irradiation is performed so that the high-dose area portion is irradiated from the surface on which the beam is incident to the deeper layer in the body, with reference to FIG. As can be seen, the plateau acts uniformly (irradiates) on the split layer on the shallow side of the body. Therefore, if the relatively small influence of the tail portion is ignored, a uniform dose distribution can be given to the target 6 by superimposing the dose distribution applied to each divided layer.

As the setting method of steps S21 to S25 described above, the two-dimensional irradiation method of the beam as in the conventional example can be applied as it is.

When the calculation of the irradiation conditions is completed as described above, the process proceeds to the stage of calculating the weight. The weight refers to the number of particles to be irradiated on each of the divided layers when the target 6 is irradiated. Here, the weight was calculated when the irradiation was performed so that the high-dose area portion was irradiated from the surface on which the beam was incident to the split layer deeper into the body. As can be seen with reference to FIG. 4, the plateau portion acts (irradiates) uniformly on the divided layer having a shallower body depth, and the tail portion also has a divided portion having a deeper body depth. This is for quantifying the dose to be irradiated in the high-dose region so that the layer works uniformly (irradiates), so that the dose is uniformly applied to each part of the target.

Therefore, as shown in FIG. 4, the beam dose characteristic function d (x) for calculating the number of irradiated particles is transferred from the body surface where the beam is incident to the deepest layer (the area of the first divided layer). A histogram is formed with the layer thickness δ as the bin width with the position of the surface on which the irradiation (partial irradiation 1) is performed as the origin (step S31).

Here, the dose characteristic function d (x) is defined as an average of biologically corrected doses absorbed into water per unit thickness when one particle of the beam enters water. Data obtained experimentally or by theoretical calculation,
The SOBP width is defined by the length (size) of the peak portion of the dose characteristic function d (x).

[0049] Also, in vivo depth bin i, body depth central value of X _i (position from its origin), is given by Equation (1). X _i = (i−0.5) · δ (1)

Then, the body depth bin i due to the partial irradiation n
Dose characteristics in the body (depth irradiation n in body depth bin i
Assuming that d _ni is the average value of the heat quantity given to the body and P _n is the bin number of the depth of the body irradiated at the peak, the relationship between the irradiations to the divided layers is given by equation (2), The area used for the dose calculation in the inside is obtained (step S3).
2). d _ni = d _{1 (n + i−1)} P _n = P ₁ −n + 1 (2)

The dose characteristic obtained by the target three-dimensional irradiation is a superposition of the irradiation dose (particularly, a high dose region portion, ie, a peak portion) to these divided layers. The number of particles per solid angle is weight w _n
In this case, the dose D _i given to the bin i in the three-dimensional irradiation is given by Expression (3), where L _i is the average geometric distance from the focal point (scatterer position) of the bin. Here, the region where the irradiation dose is calculated and the region where the beam is actually irradiated coincide with each other.

[0052]

(Equation 1)

Here, to obtain each weight w _n for making the dose D _n given to the depth bin n in the body into a target dose distribution, various known algorithms (solutions) are used as a general inverse problem. Applicable.

Here, as the simplest example, a method of obtaining the weight of each partial irradiation from the dose condition of the corresponding divided layer region (for example, the particle beam density of the irradiation beam determined for each divided layer) will be described.

First, the initial values of all the weights w _n are set to 0 (step S33). Next, assuming that the target total dose to be given to the entire target 6 is C and the dose at the peak portion (that is, the high dose region portion, the SOBP width region) is d _peak , the first division is performed using Expression (4). The weights w ₁ , w ₂ , w ₃ ,..., W _NSL are sequentially obtained from the irradiation of the layer (step S34).

[0056]

(Equation 2)

In the equation (4), max (x, y) is x or y
Δ _nm is a function that takes 1 when n and m are equal, and 0 otherwise, and always uses the latest value for the weight w _{n on} the right side.

After all the weights for each of the divided layers have been obtained, the operation of irradiating from the first divided layer to the last divided layer is repeated several times so that the dose applied to the target 6 approaches the target dose C. Can be.

[0059] Here, the evaluation of goodness of dose distribution, the tolerance dose of irradiating E, 1 if the P _i is within the depth bin i in the target, a value of 0 otherwise if one-dimensional bitmap representation of the target 6 to take, at the stage of calculation of the radiation dose of one way is finished to the target 6, the definition is the chi ² of small (predetermined value in equation (5) (Step S3).
5).

[0060]

(Equation 3)

Returning to the description, once the weights are determined, the procedure proceeds to the preparation of a procedure list for actually irradiating the beam. At first, in order to realize the irradiation of each divided layer with the obtained weight, the monitoring dose corresponding to the irradiation to each divided layer (the timing of switching the irradiation target (layer), the irradiation is actually monitored, The measured dose is calculated (step S41).

Regarding the irradiation of each divided layer, the dose monitor 1
The distance from the beam focal point is defined as L _M , the body depth X _M , the depth of the body X _M , and the physical dose characteristic not including the biological effect of the modified beam to be irradiated, d _phy (x). The difference of the dose characteristic due to the diffusion degree of the body and the depth in the body is corrected, and the physical dose M _n
Is calculated using Expression (6), the monitor dose in the irradiation to the divided layers is obtained under each setting condition.

M _n = (w _n · d _phy (X _M )) / L _M ² (6)

Actually, the monitor dose is 0 at the start of irradiation and is a quantity measured as an integral value of irradiation. In order to create a beam irradiation control command using the integrated monitor dose as a parameter, the divided layers in the respective sweeps are controlled. An integrated monitor dose to start irradiation is calculated (step S42).

Assuming that the number of sweeps is N _SW , the monitor dose applied to each divided layer in each sweep is M _n / N _SW ,
The monitor dose S ₀ given in one sweep is obtained by equation (7).

[0066]

(Equation 4)

For example, when irradiating the divided layers starting from the deeper layer in the body and reciprocating, if the amount obtained by integrating the monitor dose from the start of irradiation is defined as the integrated monitor dose, the partial irradiation n of the sweep number s is started. Integrated monitor dose S _sn
Is given by equation (8).

[0068]

(Equation 5)

The integrated monitor dose S _sn obtained here is rearranged in ascending order (in order from the one corresponding to the first divided layer to the one corresponding to the n-th divided layer), and each division based on the integrated monitor dose is performed. A procedure list of irradiation control for irradiating the selected layer is created (step S43). In other words, this procedure list allows the user to specify what amount the integrated dose monitor will take and what operation to perform next (for example, switching of the divided layers to be irradiated according to the dose of the integrated dose monitor). .

When the integrated monitor dose becomes N _SW · S ₀ , that is, when the prescribed dose is given to all the divided layers, the beam irradiation is stopped. For example, the procedure list is given to the control computer, and the control computer may control each device according to the procedure.

For example, FIG. 4 shows a flowchart for the control computer to control each device according to the procedure list.
That is, the irradiation is started (step S101), the integrated monitor dose is always read out while irradiating a certain divided layer (step S102), and is always compared with the planned monitor dose to be subjected to the next procedure (step S103). As soon as the monitoring dose reaches the scheduled monitoring dose, the setting is changed as the execution of the determined procedure, for example, irradiation to the next divided layer is performed (step S104), and the monitoring dose monitoring state is returned.
This is repeated until the irradiation ends (step S106).

When monitoring the dose of the integral monitor, instead of repeatedly reading out the dose monitor 10 at high speed, if necessary, a plurality of preset scalers or the like are used to interrupt the control computer in accordance with the value of the dose monitor. A useless read loop can be eliminated.

Therefore, according to the first embodiment, the three-dimensionally formed dose distribution for irradiating the diseased part is clarified in advance in the planning stage of irradiation, and the parameter setting of the device corresponding to the dose distribution is set. And irradiation with a high degree of freedom as planned can be performed.

Embodiment 2 In the first embodiment, the two-dimensional irradiation for each of the divided layers is superimposed using the range compensator 9 so that the beam reaches the surface of the surface of the target 6 opposite to the surface on which the beam is incident. Thus, three-dimensional irradiation is realized. In the second embodiment, an irradiation method for realizing three-dimensional irradiation without using the range compensator 9 will be described. Therefore, it is possible to save the trouble of creating the range compensator 9 according to the shape of each affected part.

The procedure of the control method for the treatment apparatus shown in the second embodiment is almost the same as the flowchart (FIG. 1) shown in the first embodiment except for the step S21 in FIG. However, the formula for calculating the weight calculated for irradiation to each divided layer is different from that of the first embodiment, as described later.

As shown in FIG. 6, the layer division of the target 6 is different from that in the first embodiment, and the target 6 is divided into the beam on the surface of the target 6 in accordance with the uneven shape of the body surface on which the beam is incident. The surface is split into layers at regular intervals in the beam incident direction (in the depth direction of the body) from the surface on which light is incident, and the multi-leaf collimator and range adjustment device are adjusted according to the irradiation area of each divided layer. The two-dimensional partial irradiation as described above is performed for each of the divided layers, and the irradiation on the divided layers is superimposed to realize the three-dimensional irradiation.

When irradiating a beam to a divided layer one by one in accordance with each divided layer, the beam irradiation field is determined by the degree of opening of the multi-leaf collimator. Here, the layer division is performed according to the uneven shape of the body surface on which the beam is incident as described above, and the area (dose distribution) where the beam is irradiated according to the degree of opening of the multi-leaf collimator according to each division layer ), FIG.
As shown in FIG. 2, the size of each of the irradiation areas divided into layers does not necessarily have a monotonically increasing relationship as shown in FIG. 2 according to the physical depth from the body surface (body depth). Also, a desired dose distribution can be given by finely adjusting the multi-leaf collimator and the range adjusting device.

That is, as described above, when the irradiation is performed such that the high-dose area is irradiated to the deeper divided layer in the body, the plateau portion affects the divided layer which is shallower in the body. (Weak irradiation), over-irradiation occurs due to irradiation of the plateau near the center of the target 6 as compared with the case of Embodiment 1, and the dose distribution of the beam of the target 6 is strictly uniform. Does not.

However, from the viewpoint of the actual treatment, over-irradiation by the plateau near the center of the target 6 is not so much a problem in many cases. It is appropriate to consider a method of calculating the weight to bring the dose into a specified amount.

In the first embodiment, the target region where the dose to be irradiated is calculated and the region where the beam is actually irradiated coincide with each other. In the second embodiment, a further subdivided region is considered as a target region for which the dose is calculated.

As shown in FIG. 8, the dose calculation region is divided into two lateral directions which are both perpendicular to the beam irradiation direction and perpendicular to each other, so that each direction has a constant angle when viewed from the beam focal point. Voxels (Voxells, division points) are defined in three dimensions. The target 6 is represented by a bitmap using the three-dimensional voxels, and is represented by a function Q _ijk .

Here, the function Q _ijk is 1 if the center of the voxel of the body depth bin number i, one horizontal division number j, and the other horizontal division number k is within the target. This function takes a value of 0 in the case. Embodiment 2
Then, the weight of each divided layer is determined using the function Q _ijk . That is, the weight of each divided layer is calculated by subdividing it into the stage of the dose irradiated to the voxel. Therefore,
Equation (9) is employed as an equation for calculating the weight and an equation for determining the goodness of the dose distribution.

[0083]

(Equation 6)

Here, L _ijk is the average distance from the beam focal point of the voxel of the body depth bin number i, one horizontal division number j, and the other horizontal division number k, and the function max.
_jk (x, y) is a function that changes the subscripts j and k, respectively, and adopts the larger value of x or y.

Therefore, the above-described three-dimensional voxel is defined, the local weight of each divided layer is calculated using equation (9) as described above, and the same processing as in the first embodiment is performed. The dose to be irradiated and the monitor dose for each divided layer can be quantitatively grasped.

Therefore, according to the second embodiment, the three-dimensionally formed dose distribution for irradiating the diseased part is clarified in advance in the irradiation planning stage, and the parameter setting of the device corresponding to the dose distribution is made clear. And irradiation with a high degree of freedom as planned can be performed.

Embodiment 3 The irradiation method realized in the third embodiment is an example of a specific method for realizing irradiation to the divided layers according to the dose to be irradiated, which is grasped in the second embodiment, for example. The number of particles to be irradiated is changed depending on the position in the irradiation field (referred to as intensity modulation), and a dose distribution near ideal is provided without using the range compensator 9.

The three-dimensional irradiation method according to the third embodiment will be described below. Since the three-dimensional irradiation method described in the third embodiment is realized by moving all the leaf groups on one side of the multi-leaf collimator together as described later, the leaf group on one side may be configured by a large single leaf. The intensity modulation can be realized by moving each leaf on the opposite side in accordance with the irradiation of each layer.

As in the case of the second embodiment, the target 6 is moved from the surface of the surface of the target 6 on which the beam is incident (depth of the beam) in accordance with the unevenness of the body surface on which the beam is incident. Direction) into layers at regular intervals.
Further, the layered target 6 is further two-dimensionally (two lateral directions) divided with respect to the plane of projection of the beam from the beam focal point to define a three-dimensional voxel as a dose calculation area.

However, here, as shown in FIG. 9, the two-dimensional division is performed in a direction corresponding to the direction in which a plurality of leaf pairs of the multi-leaf collimator which are perpendicular to each other are stacked and the direction in which the leaves move. , And a dividing interval is defined with uniform fineness (at intervals) in each direction, the laminating direction is defined as a leaf direction, and the moving direction is defined as a sliding direction.

As described above, the two-dimensional dividing direction of the three-dimensional voxel is determined according to the leaf direction and the sliding direction of the leaves of the stacked multi-leaf collimator. The rotation around the axis must be fixed.

In such a three-dimensional voxel, the voxel in which the bin number in the leaf direction is equal to the bin number in the sliding direction, that is, the voxel of each of the subordinate layers arranged in a columnar shape in the beam irradiation direction is the divided layer described above. Irrespective of this, all irradiation fields are the same.

In other words, paying attention to the columnar-aligned region (columnar portion), this is a columnar target formed by sequentially stacking divided layers having the same irradiation field in the beam irradiation direction. For the first embodiment, for example.
Weight can be calculated by the same method as in the case of.

This weight is independently calculated for each columnar area, and the weight given to each columnar area specified by leaf number j and slide number k for the n-th divided layer is w. _{If njk} is given, the number of particles of the beam irradiated corresponding to each voxel is given. In the case of the first or second embodiment, each of the divided layers corresponds to the region to be irradiated with the beam. However, in the case of the third embodiment, the above-described three-dimensional voxel of the divided layer corresponds to the region.

Therefore, the bin number in the depth direction in the body is i, the bin number in the leaf direction is j, and the bin number in the sliding direction is k.
Then, in the third embodiment, an ideal dose C _ijk and an allowable error E _ijk can be specified for each voxel. Further, as in the case of the second embodiment, a function Q that determines whether or not the voxel of the bin number i in the body depth direction, the number j in the leaf direction, and the bin number k in the sliding direction is within the target 6.
A three-dimensional bitmap representation of the target can be obtained using _ijk . Therefore, when it is desired to apply a uniform dose to the entire target 6, the dose can be obtained by Expression (10). C _ijk = C · Q _ijk (10)

As described above, even in the case of the third embodiment, the ideal dose C _ijk and the allowable error E _ijk can be specified for each voxel. Accordingly, the weight given by irradiation to each voxel and the evaluation are also expressed by the following equations. It can be obtained by (11).

[0097]

(Equation 7)

When the weight given to each voxel by irradiation is obtained, the monitor dose, the integrated monitor dose, etc. corresponding to this weight are obtained in the same manner as in the first embodiment, the irradiation control procedure, the multi-leaf collimator for each divided layer A control command for opening and closing the leaf can be created. As the monitor dose, the integrated monitor dose, and the like adopted in the second embodiment, those described in detail later will be adopted along with the operation described below.

For example, as the simplest irradiation procedure, a method is considered in which, for a certain divided layer divided in the depth direction of the body, each voxel of the layer is sequentially irradiated one by one, and two-dimensional irradiation is stacked. Can be In this case, the irradiation to the divided layer is performed for each voxel to be irradiated to the target layer using the high-dose area portion, but the leaf group is opened and the columnar one to which the voxel to be irradiated belongs belongs. Irradiation is simultaneously started on the other plurality of voxels in the row (the area of the columnar portion having the same bin number in the leaf direction and the bin number in the sliding direction) using the plateau portion or the tail portion.

That is, all leaf groups on one side of the multi-leaf collimator arranged opposite to each other are simultaneously moved to open the multi-leaf collimator corresponding to the target voxel, and the designated voxel is designated as the target voxel. After the irradiation according to the weight (monitor dose) is performed, the irradiation is performed by moving each leaf on the other side independently of the movement of the leaf group on one side and closing the multi-leaf collimator. The operation of the multi-leaf collimator will be described with reference to FIG.

The slide numbers, which are formed by a single column of a plurality of voxel groups and indicate the area to be irradiated, are sequentially numbered along the leaf moving direction.

First, for a certain divided layer to which the voxel to be irradiated belongs, all the leaf pairs of the multi-leaf collimator are closed and placed before the region of the columnar part to which the voxel to be irradiated first belongs. (Step a1).

All the leaves to be moved in advance are simultaneously moved by an amount corresponding to the area of the bin number (ie,
Open the multi-leaf collimator for the target voxel),
The irradiation of the region of the columnar portion to which the first irradiated voxel belongs starts (step b1).

When the number of irradiated particles for the first irradiated voxel has expired (ie, when the monitor dose has reached the timing for opening and closing the multi-leaf collimator).
Then, the leaf on the side to be moved is moved to close the multi-leaf collimator (step c1).

When all the leaf pairs are closed, the above-described operation is performed for the voxel to be irradiated next (steps a1 to c1).
Is repeated, and the above-described operation is sequentially repeated for all the other voxels in the layer, thereby completing the irradiation of the divided layer.

In this case, in the irradiation on the n-th divided layer, the leaf group to be moved ahead is opened for the irradiation of the k-th voxel irradiated on the layer,
After that, the number of particles irradiated per unit solid angle until the leaf on the side to be moved moves and all the leaves close,
That is, the weight w _Rnk is given by equation (12). w _Rnk = max _j (0, w _njk ) (12)

Further, while the leaf group to be moved in advance is kept open for the irradiation of the voxel irradiated in the k-th layer in the layer, the monitor dose is expressed by the following equation (13). Given. _{M Rnk = w Rnk · d dpy} (X M) / L M 2 (13)

Further, the number of sweeps is δ times, and the integral monitor dose when starting the partial irradiation on the n-th divided layer is S
_{As sn} , the integrated monitor dose S, which is the timing at which the leaf group to be moved in advance is moved to open the leaf group for irradiation of the k-th irradiated voxel in that layer,
_Rnsjk is given by equation (14).

[0109]

(Equation 8)

The integral monitor dose S _{Ls njk} at which the leaf is closed to move the leaf j on the side to be moved following the k-th irradiation of the voxel to be irradiated is given by equation (15). Can be S _Lsnjk = S _Rnsjk + w _njk / N _SW (15)

Therefore, the irradiation control procedure as in the first embodiment may be created based on the weight, the monitor dose, the integrated monitor dose, and the like as described above.

By the way, in the symmetric multi-leaf collimator, the leaf group on the side to be moved in advance and the leaf group on the side to be moved following are switched for each of the divided layers, so that a certain divided layer is irradiated. Therefore, when the irradiation target is moved to a certain divided layer to be irradiated next, leaf movement during irradiation can be minimized.

In this case, assuming that the leaf group to be moved ahead is the left-side leaf group (that is, the leaf group to the side opposite to the side that has been moved just before), the number of divisions in the sliding direction is N _K
In the equation (15), the variable R can be replaced with the variable L and the variable k can be replaced with the variable (N _K −k + 1) in consideration of the left and right exchange, and can be used.

In the irradiation method described above, the shape of the local irradiation field for each voxel becomes flat, and when the Wobbler method is used for beam expansion, the beam is flattened by adjusting the amplitude and phase of the above-described two directions of current. And the beam utilization efficiency can be increased.

In order to obtain a uniform beam intensity with a flat beam in the Wobbler method, it is necessary to make the waveform of the Wobbler current close to a triangular wave. However, in the above-described irradiation method, the number of particles is controlled for each voxel. Even if the beam intensity is not uniform, the number of particles at each voxel position is directly or indirectly monitored (monitored), and appropriate dose can be given to each voxel by performing control according to the measured value. it can.

Therefore, according to the third embodiment, a three-dimensionally formed dose distribution for irradiating the diseased part is clarified in advance in the irradiation planning stage, and setting of device parameters corresponding to the dose distribution is performed. And irradiation with a high degree of freedom as planned can be performed.

In addition, since the irradiation intensity of the local beam on the target 6 can be changed, it is possible to perform efficient irradiation (give a dose distribution) by giving a uniform glandular amount to the diseased part 5. .

The use of the intensity modulation described above can be applied to treatment using radiation other than charged particle beams such as X-rays. In the case of X-rays, division in the depth direction in the body is not performed, but an ideal three-dimensional dose distribution can be formed by multi-port irradiation combined with irradiation from different directions by changing irradiation intensity in the irradiation field.

Embodiment 4 As a modification of the irradiation method of realizing irradiation by performing intensity modulation in the irradiation field described in the third embodiment, the instantaneous irradiation field is maximized by adjusting the timing of the opening and closing operations of the leaves of the multi-leaf collimator. A method is conceivable.

First, with respect to a certain divided layer to which the voxel to be irradiated in the third embodiment belongs, all leaf pairs of the multi-leaf collimator are closed and the area of the columnar portion to which the voxel to be irradiated first belongs. (Step a2).

All of the leaves to be moved in advance are simultaneously moved by an amount corresponding to the area of the bin number (ie,
Open the multi-leaf collimator for the target voxel),
The irradiation of the region of the columnar portion to which the voxel to be irradiated first belongs starts (step b2).

When the number of irradiated particles of the target voxel has expired (ie, at the time when the monitoring dose which has reached the timing of opening and closing the multi-leaf collimator has been reached), the leaf on the side to be moved is moved. Move (step c2).

Here, the difference from the third embodiment is that, in step c2, as shown in FIG. 11, the leaf group to be moved ahead is moved to the leaf group to be moved following. The multi-leaf collimator moves ahead for the next irradiation of the voxel to be irradiated without waiting for the multi-leaf collimator to close completely, catching up with the movement of the leaf group to be moved first. Is open.

Therefore, in the case of the fourth embodiment, as compared with the case of the third embodiment, the leaf group to be moved ahead is moved, and the leaf to be moved is moved and moved ahead. In the fourth embodiment, since the multileaf collimator moves in advance for irradiation of a voxel-specific region to be irradiated next without waiting for the multileaf collimator to completely close in response to the movement of the leaf group on the side to be irradiated. Weight w _Rnk is calculated using equation (16) instead of equation (12) shown in the third embodiment. w _Rnk = max _j (0, w _njk −w _{nj (k + 1)} ) (16)

Equation (16) indicates that the number of particles required for the voxel to be irradiated whose irradiation has been started by the movement of the leaf group to be moved in advance is the number of particles required for the next voxel to be irradiated. If it is larger than this, it indicates that the movement of the leaf group to be moved earlier at that time is stopped at least by the difference.

Returning to the previous description, the above operation (steps a2 to c) is performed for the next voxel to be irradiated next.
2) is repeated, and the above-described operation is sequentially repeated for other voxels in the layer, thereby completing the irradiation of the divided layer.

Therefore, in the fourth embodiment, the weight w
_Rnk is calculated in the same _{manner as in} the third embodiment _{except that} the calculation of _Rnk is performed using the equation (16) instead of the equation (12) shown in the third embodiment.

Therefore, according to the fourth embodiment, the three-dimensionally formed dose distribution for irradiating the diseased part is clarified in advance in the planning stage of irradiation, and the parameter setting of the device corresponding to the dose distribution is set. And irradiation with a high degree of freedom as planned can be performed.

In addition, since the irradiation intensity of the local beam on the target 6 can be changed, it is possible to perform efficient irradiation such as giving a uniform dose to the affected part 5 (giving a dose distribution).

Further, since the instantaneous irradiation field can be enlarged as compared with the irradiation method shown in the third embodiment, the beam use efficiency is improved and the irradiation of the target 6 with the beam can be performed quickly.

This method is also applicable to treatment with radiation other than charged particle beams such as X-rays, as in the third embodiment.

Embodiment 5 FIG. Further, as a modification of the irradiation method of performing irradiation by performing intensity modulation in the irradiation field described in Embodiment 3, the movement of the patient is minimized by moving the patient to minimize the movement of the leaf of the multi-leaf collimator. A method of enlarging the irradiation area of the above is conceivable.

As shown in FIG. 13, by maximizing the movement of the patient (that is, the target 6), the leaf group on the side to be moved ahead of the multileaf collimator is not moved, and the case of the third embodiment is not changed. The same irradiation can be performed.

In the third embodiment, since the leaf group to be moved ahead is merely captured by the coordinate system that regards the target as being stationary, the target and the leaf group to be moved ahead are simply captured. If the relative positional relationship shown in the third embodiment is maintained, the leaf group on the side to be moved ahead of the coordinate system in which the setting parameters to the device are assumed to be stationary from the coordinate system is stationary. By converting the coordinate system into a coordinate system that can be regarded as irradiating, the same irradiation as in the third embodiment can be performed.

That is, for example, in the control command at the time of beam irradiation, what is understood as how to move the leaf with respect to the target may be interpreted as how to move the target with respect to the leaf.

However, moving the target changes the manner in which the beam irradiated to the target is diffused. Therefore, a region divided in parallel with the sliding direction of the leaves of the multi-leaf collimator is used as the dose calculation region.

The attenuation effect due to beam diffusion is not inversely proportional to the square of the geometric distance from the beam focal point, but is only inversely proportional. Therefore, L ² in the equation (11) for calculating the weight is calculated as follows. It is necessary to define the replacement weight by L in terms of the number of particles per unit angle.

Therefore, according to the fifth embodiment, not only the same effects as in the third embodiment can be obtained, but also by moving the patient, compared with the third embodiment, It is possible to obtain a larger irradiation area than the area that can be irradiated by moving the leaf of the multi-leaf collimator.

Further, since each leaf of the multi-leaf collimator can be opened and closed by one voxel, a single wobbler electromagnet can be obtained by uniquely fixing the set angle of the multi-leaf collimator. It should be noted that adaptation to X-ray therapy is possible as in the case of the third embodiment.

Embodiment 6 FIG. Further, the opening / closing operation (timing) of the leaf of the multi-leaf collimator described in the fourth embodiment.
As a modification of the irradiation method of realizing irradiation by performing intensity modulation in the irradiation field by adjusting the distance, the movement of the leaf of the multi-leaf collimator is minimized by moving the patient (target 6) as in the fifth embodiment. A method of enlarging the irradiation area of the patient (target 6) can be considered.

As shown in FIG. 13, by maximizing the movement of the patient (ie, the target 6), the fourth embodiment can be performed with the leading leaf group of the multi-leaf collimator completely fixed.
Irradiation equivalent to can be performed. As described in the fifth embodiment, that is, in the fourth embodiment, the leaf group to be moved ahead is merely captured in the coordinate system that captures the target as a stationary one. If the relative positional relationship shown in the fourth embodiment between the precedently moved leaf group and the precedently moved leaf group is maintained, the setting parameters for the device precede from the coordinate system in which the target is regarded as stationary. By converting the leaf group to be moved to a coordinate system in which the leaf group is regarded as stationary, the same irradiation as in the fourth embodiment can be performed.

However, in the sixth embodiment, as in the case of the fifth embodiment, the change of the voxel dividing method, the attenuation effect due to the geometric distance from the beam focal point, and the change of the formula for calculating the weight are the same. Required.

Therefore, according to the sixth embodiment, not only the same effects as in the fourth embodiment can be obtained, but also by moving the patient, compared with the fourth embodiment, An irradiation area larger than an area that can be irradiated by moving the leaf of the multi-leaf collimator can be obtained, and the configurations of the multi-leaf collimator and the beam expander can be simplified.

This method is also similar to the fourth embodiment in that it can be adapted to treatment with radiation other than charged particle beams such as X-rays.

Embodiment 7 FIG. The irradiation method described in the seventh embodiment realizes three-dimensional irradiation by controlling each device continuously (ie, finely) based on a function of particle intensity that is repeatedly measured at high speed. For this reason,
It is suitable for controlling devices that move continuously instead of devices that move intermittently with a fixed step width, such as analog range shifters and multi-leaf collimators.

In the above-described digital control in which the object is moved discontinuously at a fixed step width, even if the object is an analog device, the movement is performed intermittently. Although a mechanism or the like is required, analog control for performing continuous movement does not require a high acceleration, and the movement is stationary, so that such a mechanism is unnecessary. In the seventh embodiment, for convenience of explanation, an example in which the irradiation to the divided layers is continuously controlled as an improvement of the three-dimensional irradiation method described in the first or second embodiment will be described.

In the seventh embodiment as well, a control command (procedure list) for causing each device to perform continuous movement is created by a procedure substantially similar to the procedure shown in the first or second embodiment. It is necessary to partially modify the procedure as described below in order to perform continuous fine movement in.

That is, it is necessary to grasp the monitor dose as a reference for the irradiation control as a continuous function using an approximate function or the like.
The method is as follows.

In Embodiments 1 and 2, the thickness of the divided layer is adjusted to the SOBP width of the dose characteristic. However, here, the sizes of both are treated independently, and in consideration of continuous fine control, the divided layer is taken into account. , That is, the bin width shown in FIG. 4 described above, is made even smaller, and the dose characteristic of the irradiated beam is converted into a histogram.

Then, the high dose region portion of the bin portion where the dose characteristic peaks is adopted as a portion used for irradiation (a portion used for giving a high dose to the target).

At the time of irradiation, first, the range of the irradiated portion of the beam (the depth of the body reached by the portion of the bin) is adjusted, for example, to the deepest portion of the target body. Irradiation is performed, and subsequently, irradiation is sequentially performed on the divided layers from the deepest part of the target to the surface where the beam is incident, whereby three-dimensional irradiation can be performed.

Here, with such continuous control,
For example, as the integrated monitor dose as a reference for the irradiation control, a value obtained by calculating the optimal integrated monitor dose S _sn for the partial irradiation n for each beam irradiation as a continuous function as described below may be used. .

Here, a range control device is considered as an example of a device that is continuously controlled. Given the body depth median X _pn of the n-th division layer determined directly from the amount of adjustment the projected range.
The relationship between the integral monitor dose S _n of irradiation sweep s at the portion irradiated n is approximated by a polynomial.

Assuming that the order of the polynomial is N _D , the depth X _{p in} the body of the peak portion (the portion used to apply a high dose to the target of the histogram-formed beam) is a continuous function (approximation) of the integrated monitor dose S. Function) can be grasped as in equation (17).

[0155]

(Equation 9)

Then, a sweep s (s = 1, 2,...)
·, (N for N _{SW) D} +1) number of coefficients a _{sm (sm} =
1, 2,..., N _D ) are obtained by a simple least squares method.
Obtained by solving the given (N _D +1) pieces of simultaneous equations as in Equation (18).

[0157]

(Equation 10)

As a result, the optimum integrated monitor dose for the partial irradiation as a reference for the irradiation control at each irradiation can be grasped as a continuous function (approximate function).

The same applies to the adjustment of parameters (set values) of each device that changes with each beam irradiation, such as a beam expanding device, a multi-leaf collimator, a treatment table position, and the like. The parameters of each device can be set finely in response to the monitoring dose as a continuous function.

FIG. 14 is a flowchart showing the above-described device control process performed by the control computer using the output polynomial coefficient corresponding to the control command and the final integrated monitor dose for stopping irradiation for each device. Something like

Therefore, according to the seventh embodiment, the three-dimensionally formed dose distribution for irradiating the affected part is clarified in advance in the irradiation planning stage, and the setting of the equipment parameters corresponding to the dose distribution is performed. And irradiation with a high degree of freedom as planned can be performed.

It is considered that most of the time required for changing the set value of the device is required for mechanical movement of the device, but the change amount becomes smaller as the frequency of repetition increases, and the time required for the change becomes shorter accordingly. . Therefore, by grasping such an integrated monitor dose as a continuous function (approximate function), the time required for changing the set value does not depend on the readout frequency, but rather the acceleration / deceleration required for mechanical movement of the device is reduced. The continuous control of the mechanism which performs a dynamic movement becomes easy.

Embodiment 8 FIG. The continuous control procedure described in the seventh embodiment may be applied to the three-dimensional irradiation method with intensity modulation that maximizes the instantaneous irradiation field described in the fourth and sixth embodiments. The procedure for creating a weight, a monitor dose, and the like and a procedure for creating a control command as a basis for creating a control command for the device are the same as in the seventh embodiment. However, what is controlled continuously is a set value of a device whose irradiation condition changes with irradiation to each divided layer, and these give a polynomial for performing continuous control every time the irradiation condition changes.

The procedure list is created in accordance with the method described in the fourth and sixth embodiments, but the division of the leaves of the multi-leaf collimator in the sliding direction is made fine in correspondence with the continuous function for the voxels for calculating the dose. There is a need. Then, the created procedure list for each slice may be grasped as a continuous function according to the integrated monitor dose grasped as the continuous function shown in the seventh embodiment.

In this case, what is continuously controlled are the set values of the devices that change during irradiation of a certain divided region, such as the leaf positions of the multi-leaf collimator, the treatment table position, and the set values of the wobbler magnet. The control command is passed to the control computer as the setting values of the equipment fixed by irradiation to each division layer, the polynomial coefficients of the setting values of the equipment that change during irradiation to each division layer, and the end of each slice irradiation. This is the integrated monitor dose.

As shown in FIG. 15, the control computer performs continuous control of devices such as a multi-leaf collimator during irradiation of each divided layer based on the received control information for irradiating the integrated monitor dose as a continuous function. Then, the irradiation may be controlled on the basis of the integrated monitor dose, and the setting of a device such as a range shifter may be changed during the movement from the divided layer to the divided layer.

Therefore, according to the eighth embodiment, the three-dimensionally formed dose distribution for irradiating the diseased part is clarified in advance in the planning stage of irradiation, and the parameter setting of the device corresponding to the dose distribution is set. And irradiation with a high degree of freedom as planned can be performed.

It is considered that most of the time required for changing the set value of the device is required for mechanical movement of the device, but the change amount becomes smaller as the frequency of repetition increases, and the time required for the change becomes shorter accordingly. . Therefore, by grasping such an integrated monitor dose as a continuous function (approximate function), the time required for changing the set value does not depend on the readout frequency, but rather the acceleration / deceleration required for mechanical movement of the device is reduced. The continuous control of the mechanism which performs a dynamic movement becomes easy.

[0169]

According to the present invention, the first step of determining the division interval for dividing the target into layers based on the range of the high-dose region of the particle beam irradiated to the target from the beam irradiation apparatus. And a second step of dividing the target into layers based on the division interval determined in the first step, and a predetermined dose applied to the entire target and a high-dose area portion of the particle beam corresponding to the predetermined dose. A third step of determining a dose to be applied to each of the layers divided in the second step based on the intensity of the beam, and a step of irradiating a predetermined layer among the layers divided in the second step. A fourth step for determining the timing at which the intensity of the particle beam reaches the dose irradiated to the predetermined layer determined in the third step, and an irradiation range disposed between the beam irradiation apparatus and the target. Forming means The irradiation range in the direction perpendicular to the layer stacking direction is determined for each layer to be irradiated with the particle beam, the beam is irradiated by the beam irradiation device, and the particle beam is irradiated at the timing determined in the fourth step. And a fifth step of switching layers, so that a three-dimensionally formed dose distribution for irradiating the diseased part is clarified in advance in an irradiation planning stage, and setting of device parameters corresponding to the dose distribution is performed. It is possible to obtain an irradiation method capable of performing irradiation as planned by making it possible.

A first step of determining a division interval for dividing the target into layers based on the range of the high-dose region of the particle beam irradiated to the target from the beam irradiation apparatus; A second step of dividing the target into layers at regular intervals along the shape of the body surface on which the particle beam is incident, based on the division interval determined in the above, and a predetermined dose applied to the entire target A third step of determining a dose to be applied to a unit area in each of the layers divided in the second step based on the beam intensity corresponding to a high-dose area portion of the particle beam, and a second step At which the intensity of the particle beam irradiated to the predetermined layer in the layers divided by the step reaches the dose irradiated to the unit area in the predetermined layer determined in the third step The fourth step of finding The irradiation range in the direction orthogonal to the layer stacking direction is determined for each unit area irradiated with the particle beam by the irradiation range forming means arranged between the beam irradiation device and the target, and the beam is irradiated by the beam irradiation device. ,
And a fifth step of switching a unit area to be irradiated with the particle beam based on the timing obtained in the fourth step. Irradiation that clarifies the three-dimensionally formed dose distribution to irradiate the affected part in advance in the planning stage of irradiation, and also enables setting of equipment parameters corresponding to the dose distribution to perform irradiation as planned. You can get the way.

In the fifth step, the multi-leaf collimator constituting the irradiation range forming means waits in front of the range where the beam is irradiated in a state where all the leaf pairs are closed. Simultaneously moving all the leaves on the side and opening the multi-leaf collimator by an amount corresponding to the range to be irradiated, and starting irradiation of the beam to the range to be irradiated; Moving the leaf on the other side to close the multi-leaf collimator and stop irradiating the beam to the area to be irradiated, so that the three-dimensionally formed dose distribution to irradiate the diseased part in the irradiation planning stage It is possible to obtain an irradiation method which makes it possible to set the parameters of the device corresponding to the dose distribution, which is clarified in advance, and which can perform irradiation as planned.

In the fifth step, the multi-leaf collimator constituting the irradiation range forming means waits in front of the range where the beam is irradiated with all the leaf pairs closed, and one of the leaf pairs Simultaneously moving all the leaves on the side and opening the multi-leaf collimator by an amount corresponding to the range to be irradiated, and starting irradiation of the beam to the range to be irradiated, and when the timing for each range to be irradiated is reached, the other side Move the leaves to stop irradiation to the area to be irradiated, move all leaf groups on one side simultaneously, open the multi-leaf collimator by the amount corresponding to the area to be irradiated next, and move to the area to be irradiated next. Starting the irradiation of the beam, the three-dimensionally formed dose distribution for irradiating the affected area is clarified in advance at the planning stage of irradiation, and the parameters of the equipment corresponding to the dose distribution are determined. Irradiation method capable of performing irradiation of planned to allow setting can be obtained.

Further, since the timing is estimated from an approximate function obtained from a relationship between a plurality of predetermined unit areas and the timing in the unit area, a three-dimensionally formed dose distribution for irradiating the affected part is obtained. Can be clarified in advance in the irradiation planning stage, and an irradiation method capable of setting the parameters of the equipment corresponding to the dose distribution and performing irradiation as planned can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an irradiation method according to a first embodiment.

FIG. 2 is an explanatory diagram of an irradiation method according to the first embodiment.

FIG. 3 is an explanatory diagram of an irradiation method according to the first embodiment.

FIG. 4 is an explanatory diagram of an irradiation method according to the first embodiment.

FIG. 5 is an explanatory diagram of an irradiation method according to the first embodiment.

FIG. 6 is an explanatory diagram of an irradiation method according to a second embodiment.

FIG. 7 is an explanatory diagram of an irradiation method according to a second embodiment.

FIG. 8 is an explanatory diagram of an irradiation method according to a second embodiment.

FIG. 9 is an explanatory diagram of an irradiation method according to a third embodiment.

FIG. 10 is an explanatory diagram of an irradiation method according to a third embodiment.

FIG. 11 is an explanatory diagram of an irradiation method according to a fourth embodiment.

FIG. 12 is an explanatory diagram of an irradiation method according to a fifth embodiment.

FIG. 13 is an explanatory diagram of an irradiation method according to a sixth embodiment.

FIG. 14 is an explanatory diagram of an irradiation method according to a seventh embodiment.

FIG. 15 is an explanatory diagram of an irradiation method according to an eighth embodiment.

FIG. 16 is an explanatory diagram of a conventional beam irradiation method.

FIG. 17 is an explanatory view of a conventional beam irradiation method.

FIG. 18 is an explanatory view of a conventional beam irradiation method.

FIG. 19 is an explanatory diagram of a conventional beam irradiation method.

FIG. 20 is an explanatory diagram of a conventional beam irradiation method.

FIG. 21 is an explanatory diagram of a conventional beam irradiation method.

FIG. 22 is an explanatory diagram of a conventional beam irradiation method.

[Explanation of symbols]

Claims (5)

[Claims] A first step of determining a division interval for dividing the target into layers based on a range of a high-dose region of a particle beam irradiated to the target from a beam irradiation apparatus; A second step of dividing the target into the layers based on the division intervals determined in the step, and corresponding to a predetermined dose applied to the entire target and a high dose region portion of the particle beam. A third step of obtaining a dose to be applied to each of the layers divided in the second step based on the intensity of the beam to be irradiated; and a predetermined layer in the layers divided in the second step. A fourth step of determining a timing at which the intensity of the particle beam irradiated to the predetermined layer reaches the dose irradiated to the predetermined layer determined in the third step; and the beam irradiation apparatus and the target. The irradiation range in the direction perpendicular to the stacking direction of the layers is determined for each layer to be irradiated with the particle beam by the irradiation range forming means disposed between the layers, and a beam is irradiated by the beam irradiation device, A fifth step of switching a layer to be irradiated with the particle beam based on the timing obtained in the fourth step. 2. A first step of determining a division interval for dividing the target into layers based on a range of a high-dose region of a particle beam irradiated to the target from a beam irradiation device; A second step of dividing the target into layers at regular intervals along the shape of the body surface on which the particle beam is incident, based on the division interval determined in the step; and irradiating the entire target. A third step of obtaining a dose applied to a unit area in each layer divided in the second step based on a predetermined dose and a beam intensity corresponding to a high-dose area portion of the particle beam. And the intensity of the particle beam irradiated to a predetermined layer among the layers divided in the second step is determined by the third step. Illuminates the middle unit area A fourth step of determining the timing at which the particle beam reaches a certain dose; and the irradiation range forming means arranged between the beam irradiation device and the target causes the particle beam to set an irradiation range in a direction orthogonal to the layer stacking direction. A fifth step of determining a unit area to be irradiated, irradiating a beam by the beam irradiation apparatus, and switching a unit area to be irradiated with the particle beam by the timing obtained in the fourth step. An irradiation method, characterized in that: 3. A fifth step is a step in which the multi-leaf collimator constituting the irradiation range forming means waits in front of the range where the beam is irradiated in a state where all the leaf pairs are closed; Simultaneously moving all the leaves on one side, opening the multi-leaf collimator by an amount corresponding to the irradiation range, and starting irradiation of the beam to the irradiation range; and reaching the timing for each irradiation range. 3. The irradiation method according to claim 2, further comprising the step of: moving the leaf on the other side of the pair of leaves to close the multi-leaf collimator and stopping the irradiation of the beam to the irradiated area. . 4. A fifth step is a step in which the multi-leaf collimator constituting the irradiation range forming means waits in front of a range where the beam is irradiated in a state where all the leaf pairs are closed; Simultaneously moving all the leaves on one side, opening the multi-leaf collimator by an amount corresponding to the irradiation range, and starting irradiation of the beam to the irradiation range; and reaching the timing for each irradiation range. At the point in time, moving the leaves on the other side to stop the irradiation on the irradiated area, simultaneously moving all the leaves on the one side, and moving the multi-leaf collimator by an amount corresponding to the next irradiated area. 3. An irradiation method according to claim 2, further comprising the step of opening and irradiating the next irradiation area with a beam. 5. The timing according to claim 2, wherein the timing is estimated from an approximate function obtained from a relationship between a plurality of predetermined unit areas and timings in the unit areas.
5. The irradiation method according to any one of claims 1 to 4.