JPH11290466A - Proton beam radiation direction determination supporting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate determination of a proton beam radiation direction in a treatment plan of radial beam treatment using a proton beam. SOLUTION: An enlarged Bragg peak (SOBP) width, a sticking-out part of a 100% dose region outside a focus, and a water equivalent thickness from the focus to a body surface are computed for plural radiation directions based on specified resolution, and distribution maps 101-103 for respective values are displayed. In addition, the distribution maps 101-103 are interlocked with a three-dimensional display surface 112. In determining a radiation direction, quantitative determination can be performed. In addition, by interlock with three-dimensional display, the radiation direction can be grasped by intuition, while a final radiation direction can be determined interactively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment plan which enables a proton beam treatment to effectively give a dose to a lesion while minimizing exposure to normal tissues.

[0002]

2. Description of the Related Art In radiotherapy using radiotherapy, it is necessary to give a sufficient therapeutic dose to lesions such as cancer while minimizing exposure to normal tissues. Therefore, in general, using image data obtained by an image diagnostic apparatus such as an X-ray CT apparatus, it is possible to determine from which direction and how much radiation should be irradiated before treatment based on a simulation result of a dose distribution and the like. A treatment plan to judge and decide is required.

On the other hand, radiation called proton beam used in proton beam therapy has a characteristic called "Bragg Peak". When a proton beam irradiates a substance, the dose rapidly increases at a certain depth from the surface and has a maximum value, and at a depth deeper, the dose rapidly decreases to zero. The position where this dose has the maximum value is called the Bragg peak. By utilizing such characteristics, it is possible to give a high dose only to a lesion and to give little dose behind the lesion. In using this Bragg peak characteristic in actual treatment, the lesion has a predetermined depth in the irradiation direction, so instead of using the Bragg peak as it is, a ridge filter installed in the proton beam irradiation device Enlarge Bragg Peak,
It is used so as to have a flat area by a certain width. This flat region with a constant width is enlarged by the Bragg peak (S
OBP: Spread Out of Bragg Peak).

[0004] In the case of proton beam therapy, if the width and position of SOBP are controlled, it is possible to apply a high dose only to the shape of the lesion and to give little dose behind the lesion. Will be possible. Therefore, in the treatment plan of proton beam therapy, it is important to determine the irradiation direction by understanding the shape of the lesion and the positional relationship between the normal tissue and the lesion around the lesion.

[0005] Such a treatment plan is generally implemented in software on a computer system. In the treatment plan, first, a three-dimensional region is set for a lesion and a notable normal tissue (for example, an organ which should not be irradiated with a proton beam) using the image data, and the coordinates are stored in a memory. Let it. Next, based on the irradiation range (called an irradiation field) determined according to the size of the lesion and the temporarily determined irradiation direction and irradiation intensity, the three-dimensional dose distribution inside the human body is calculated using image data according to a certain physical model. calculate. The results obtained in this way are evaluated using various evaluation means. For example, D is a graph showing the relationship between the dose and the tissue volume having the dose value for the lesion and each normal tissue.
VH (Dose Volume Histogram), 2D iso-dose diagram in which dose distribution is superimposed on a tomographic image of a human body, or 3D in which a dose distribution is superimposed on a human body tissue with 3D data as it is, and translucent and three-dimensionally displayed Display. Based on these, if it is judged that the dose distribution is desirable, the provisionally determined irradiation direction and irradiation intensity are adopted for treatment, otherwise, the irradiation direction and irradiation intensity are determined again and the dose distribution is calculated. And evaluate the results. In the treatment plan, the irradiation direction and the irradiation intensity to be adopted for the treatment are generally determined by such repetition.

It is a very time-consuming task for a person to make a treatment plan through this repetitive process. Therefore, several methods for calculating the irradiation direction and the irradiation intensity by mathematical processing have been proposed. For example, A. Brahme, P. Kall
man, B. Lind: "Optimization of the Probability of
Achieving Complication Free Yumor Control Usinga 3
D Pencil Beam Scanning Technique for Protons and H
eavy Ions "(Proceedings from the NIRS internationa
l workshop on heavy charged particle therapy and r
elated subjects. Chiba, Japan, 124/142, 1991)
B. Lind, A. Brahme: "Photon Field Quantities and U
nits for Kernel Based Radiation Therapy Planning a
nd Treatment Optimization "(Phys. Med. Biol., Vol.
37, 891/909, 1992). These methods calculate the irradiation direction and the irradiation intensity so as to give the optimum dose distribution based on the least squares method, and obtain the irradiation direction and the irradiation intensity from a desired dose distribution inside the human body.
It takes the form of a so-called inverse problem.

[0007]

However, when these methods are applied to the proton therapy planning, there is a problem that the calculation becomes complicated and the calculation time becomes long. Also,
Since it is premised that a desired dose distribution inside the human body is given as an input, there is also a problem that when handling a three-dimensional treatment plan, the time and effort required for the input becomes enormous.

An object of the present invention is to provide means for facilitating the determination of the irradiation direction of a proton beam in a treatment plan for radiation therapy using a proton beam.

[0009]

SUMMARY OF THE INVENTION A proton beam irradiation direction determination support system according to the present invention is a system for supporting the determination of a proton beam irradiation direction, and utilizes shape information of a lesion to be irradiated with a proton beam. Then, for a plurality of irradiation directions, a calculation means for calculating the value of the enlarged Bragg peak width required to cover the lesion, and a display means for displaying a distribution map showing the distribution of the calculated values It is characterized by the following.

In this case, when the lesion is covered by using the calculated enlarged Bragg peak width, the volume of the region protruding from the lesion is calculated, and the distribution diagram showing the distribution of the calculated volume value is shown in FIG. It may be displayed.

Further, the proton beam irradiation direction determination support system further includes an input unit for inputting image data including a lesion to be irradiated with proton beams, and an extracting unit for extracting shape information of the lesion from the image data. You may have it.

In this case, the water equivalent distance from the lesion to the body surface may be calculated, and a distribution diagram showing the distribution of the calculated water equivalent distance may be displayed.

The display means displays a mark at a position on the distribution map corresponding to the selected irradiation direction, and at a position having a symmetry relationship when the values of the distribution map have symmetry with respect to the irradiation direction. You may make it. Further, the lesion and its surrounding tissue and the proton beam may be three-dimensionally displayed, and the direction of the three-dimensionally displayed proton beam may be linked with the mark on the distribution map.

The latitude and longitude values of the selected irradiation direction, the value of the enlarged Bragg peak width corresponding to the irradiation direction, the value of the volume difference between the lesion and the area where the enlarged Bragg peak width covers the periphery of the lesion, Further, the value of the water equivalent distance from the focus center to the body surface may be displayed.

If the expanded Bragg peak width that can be adopted in proton beam therapy is limited, the irradiation direction corresponding to the expanded Bragg peak width may be specially displayed on each distribution map. Here, the special display refers to, for example, displaying a different color or method from other points or lines in the distribution map in order to clarify the selectable irradiation direction.

A proton beam irradiation direction determination support method according to the present invention is a method for supporting determination of a proton beam irradiation direction,
Using the shape information of the lesion to be irradiated with the proton beam, for a plurality of irradiation directions, calculating the value of the expanded Bragg peak width required to cover the lesion, and showing the distribution of the calculated values. Displaying a distribution map.

In this case, when the lesion is covered by using the calculated enlarged Bragg peak width, the step of calculating the volume of the region protruding from the lesion for a plurality of irradiation directions, and the step of calculating the distribution of the calculated volume value And displaying a distribution map as shown.

Further, in the above method, inputting image data including a lesion to be irradiated with a proton beam;
Extracting shape information of a lesion from the image data.

In this case, the method may further include a step of calculating a water equivalent distance from the lesion to the body surface for a plurality of irradiation directions, and a step of displaying a distribution map showing a distribution of the calculated water equivalent distance. It may be.

[0020]

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

First, a proton therapy system to which the embodiment of the present invention is applied will be described. FIG. 12 shows such a proton therapy system. As shown in the figure, the present system includes an X-ray CT apparatus 1201 and a treatment planning apparatus 12.
02 and a treatment device 1204. The treatment device 1204 includes an accelerator 1206, a gantry 1208, an irradiation nozzle 1209, a treatment bed 1210, and a control device 1205 for controlling these.

The X-ray CT apparatus 1201 acquires a tomographic image of a human body to be treated. The tomographic image of the human body acquired by the X-ray CT apparatus 1201
Is input to The treatment planning device 1202 calculates a dose distribution based on various parameters 1203, and evaluates / determines the result. Then, these parameters 1203 are changed several times to determine the most appropriate irradiation condition. The determined irradiation conditions are stored in the control device 120 in the treatment device 1204.
5 is input. According to the irradiation conditions, the controller 1205 controls the maximum range of the proton beam, the SOBP of the proton beam, the rotation angle of the gantry 1208, the parameters of various devices such as a ridge filter installed in the irradiation nozzle 1209, and the position of the treatment bed 1210. And the rotation angle.

FIG. 13 shows a computer system for realizing the treatment planning device 1202. As shown in the figure, the system includes a computer main body 1301, an input device 1302 for inputting data such as image data and an operator's instruction, and a display device 1303 for displaying a calculation result based on the input data. And a storage device 1304 for storing the treatment planning software itself and output results.

FIG. 2 is a diagram showing a state of treatment by the proton beam therapy system. As shown in FIG.
A ridge filter 204, a bolus 205, and a patient collimator 206 toward a lesion 202 inside the human body 201.
Irradiated via The graph shown on the right side of the figure shows the deep dose distribution 209 when the proton beam 203 was irradiated.
The horizontal axis D208 represents the dose, the SOB
The relative dose [%] when the dose at P210 is 100%, and the vertical axis z207 indicates the depth of the proton beam in the irradiation direction.

The ridge filter 204 is for expanding the Bragg peak to have a flat area by a certain width. The bolus 205 is a type of a distance compensation filter, and the rear end of the SOBP 210 is
It serves to adjust to the trailing end. Bolus 20
The shape of No. 5 is determined so that the water equivalent depth from the bolus 205 to the trailing edge of the lesion 202 becomes a constant value. Then, depending on the shape of the lesion, almost no dose is given before the lesion. Patient collimator 206
Is for shielding the horizontal direction other than the lesion 202 so that the proton beam is not irradiated.

When a lesion is irradiated with a proton beam in this way, the position of the SOBP can be controlled by adjusting the incident energy of the proton beam. Therefore, if the water equivalent depth from the body surface to the lesion and the water equivalent thickness in the depth direction of the lesion are known, it is possible to make the SOBP match the lesion well. The water equivalent depth from the body surface to the lesion and the water equivalent thickness in the depth direction of the lesion can be obtained using image data taken by an X-ray CT apparatus.

As described above, since the SOBP width is defined by the ridge filter 204, its value is constant regardless of the location. If the SOBP width is determined in accordance with the maximum value of the water equivalent thickness of the lesion, At the position where the maximum value is not attained, the SOBP protrudes toward the leading edge of the lesion. That is, some normal tissue near the lesion has a 100
% Dose. It is unavoidable that such protruding portions exist to some extent, but it is desirable that the amount is small. Therefore, next, the protruding portion will be considered.

For the sake of simplicity, consider a proton beam irradiation in a two-dimensional section. FIG. 3 is a diagram showing the relationship between the irradiation direction, the shape of the lesion, and the protruding portion. When the irradiation direction 301 is determined as shown in FIG.
In order to completely cover with OBP, the SOBP width needs to be adjusted to the maximum length (depth) 303 that the lesion can take when the lesion 302 is viewed in this direction. Further, the spread in the direction perpendicular to the irradiation direction needs to be the lateral length 304 of the lesion as viewed from the irradiation direction. SOBP width 303
Is defined by the ridge filter and is constant everywhere, regardless of its position. Therefore, the area of the 100% dose area is ultimately obtained by multiplying the product of the maximum vertical length (SOBP width) 303 and the horizontal length 304 of the lesion. equal. On the other hand, the area of a lesion can be obtained by an extraction process from image data.
Therefore, if the latter is subtracted from the former, it will
05 area. In addition, since the area of the lesion is a constant value, the area of the protruding portion 305 becomes the minimum after all, because the product of the maximum length 303 of the lesion viewed from a certain direction and the horizontal length 304 perpendicular thereto. This is the case when the irradiation direction is selected in a direction that minimizes. When this is extended to three dimensions, the volume of the protruding portion is equal to the product of the maximum length of the lesion (SOBP width) viewed from a certain direction and the projected area of the lesion in that direction, and this product is minimized. When the irradiation direction is selected in such a direction, the volume of the protruding portion is minimized.

FIG. 3 shows, as other examples, a case where the shape of the lesion is a circle (b) and a case where the lesion is a rectangle (c). As shown in FIG. 3B, when the shape of the lesion is a circle, the maximum longitudinal length 307 and the lateral length 308 of the lesion are equal to the diameter of the circle, and are constant regardless of the irradiation direction. Therefore, the area of the protruding portion 309 has a constant value regardless of the irradiation direction. On the other hand, as shown in FIG. 3C, when the shape of the lesion is rectangular, the protruding portion 313 becomes completely zero in the irradiation direction perpendicular to each side of the rectangle. from now on,
In general, it is considered that the protruding amount is hard to be reduced even when the irradiation direction is changed as the lesion is closer to a circle, and the protruding amount is easily reduced when the irradiation direction is changed as the lesion is closer to a rectangle.

From the above, in the treatment planning of the proton beam therapy, it is first conceivable to adopt the irradiation direction in which the volume of the protruding portion is minimized as the final solution. However, there are cases where such an irradiation direction cannot be adopted as the final solution. For example, when the direction is selected, the SOBP width required to cover the lesion is uniquely determined correspondingly. However, in actual treatment, it is often used by selecting from several ridge filters prepared in advance.
Ridge filters that can realize the OBP width are not always provided.

In addition, even if the irradiation direction in which the volume of the protruding portion is minimized is selected, the distance between the lesion and the body surface becomes long in that direction, which may unnecessarily expose many normal tissues. . Therefore, the volume of the protruding part, SO
It is preferable to determine the irradiation direction while considering three pieces of information such as the BP width and the water equivalent distance from the lesion to the body surface.

In the embodiment of the present invention, the above three information (S
The following method is used to adopt the OBP width, the volume of the protruding portion, and the water equivalent distance from the lesion to the body surface) and to facilitate comparison of these pieces of information.

First, the irradiation direction is represented by a set of latitude and longitude. FIG. 4 shows a coordinate system used in the following description. As shown in the figure, there is a lesion 402 inside a human body 401, and the origin of coordinates is taken at the center. The irradiation direction 403 is specified by a longitude θ404 and a latitude φ405.

Under such a coordinate system, the latitude and longitude are changed according to a predetermined resolution (in increments of angle), and the above three values are calculated for each irradiation direction. The distribution of the values is displayed using shades and contour lines.

In the case of the volume of the protruding portion and the SOBP width,
These maps have symmetry. That is, when the irradiation direction is considered as a point on the unit spherical surface, a value calculated in a certain irradiation direction and the value calculated in the opposite direction are equal (point symmetry). Therefore, in calculating the volume of the protruding portion and the SOBP width, it is sufficient to calculate those values only for points on the hemisphere. On the other hand, in the case of the water equivalent distance from the lesion to the body surface, one center of the lesion is determined, and the water equivalent thickness from that to the body surface is determined. Since this generally has no symmetry like the other two, it needs to be calculated in all directions.

FIG. 5, FIG. 6, and FIG.
The conceptual diagram of each distribution map of the width, the volume of the protruding part, and the water equivalent distance from the lesion to the body surface is shown. These are examples when the distribution of each value is displayed by contour lines. SOBP
In the width distribution chart 501, the horizontal axis represents the longitude θ502 and the vertical axis represents the latitude φ503 based on the polar coordinate system of FIG.
The irradiation direction (point on the distribution map) having the same value is the contour line 50.
4 and so on. The minimum point 505 at which the value becomes the smallest
Is displayed with a cross. In the case of the SOBP width, there are two minimum points 505 due to its symmetry. The distribution diagram 601 of the volume of the protruding portion in FIG. 6 and the distribution diagram 701 of the water equivalent distance from the lesion to the body surface in FIG. 7 are almost the same as those in FIG. However, since the water equivalent distance generally has no symmetry, there is only one minimum point 705.

If these three maps are displayed at the same time, it is easy to narrow down the desired irradiation direction by comparing and examining them with each other. When the operator selects an irradiation direction (a point on the distribution map) by a mouse pick operation or the like on each distribution map, the selected direction is marked on the distribution map. The three distribution maps are linked to each other, and when an irradiation direction is selected on a certain distribution map, a mark is displayed at a position corresponding to that direction on all the distribution maps. In this way, by linking the three distribution maps, when a certain irradiation direction is selected,
This makes it easier to determine the two types of information, and makes it easier to determine the irradiation direction.

In each distribution map, the distribution of values may be represented by shading instead of contour lines. Further, the contour of the value distribution may be displayed in such a manner that the distribution of the values is represented by shading.
The number and color of the contour lines are arbitrarily set, for example, according to an instruction from the operator.

If there are restrictions on the types of ridge filters that can be adopted, SOBP determined according to the ridge filter
A width value is registered, and a point (contour line) corresponding to the irradiation direction having that value is specially displayed on the SOBP width distribution diagram 501. The special display refers to, for example, displaying a different color from the other points (contour lines) so as to be distinguished from the other points (contour lines). Furthermore, for the other two distribution maps,
The same point (curve) as the point (curve) specially displayed in the distribution chart 501 is specially displayed. In this way, when an existing ridge filter is used, the irradiating direction that can be adopted is specified, so that it is easy to select the irradiating direction under the restrictions. If it is necessary to use an SOBP width that cannot be realized by an existing ridge filter, a new filter that realizes the SOBP width in the employed irradiation direction will be manufactured.

Next, the SOBP distribution diagram 50 as described above is used.
1. Display processing for displaying the protruding partial volume distribution chart 601 and the water equivalent thickness distribution chart 701 will be described.

FIG. 8 is a flowchart for explaining the display processing of the SOBP distribution chart and the protruding partial volume distribution chart.

First, as a preparatory step before performing the actual display processing, a lesion and a shape and a position of a target tissue are set.
An area setting process is performed (S1501). More specifically, a process of obtaining three-dimensional coordinates of the entire human body tissue, lesion, and normal tissue from three-dimensional image data stored in a three-dimensional array composed of voxels is performed. When attention is paid to a tomographic image of a human body, each point in the tomographic image is called a pixel, and when attention is paid to the entirety of a plurality of tomographic images, each internal point is called a voxel. The above processing identifies voxels in a region such as a lesion from three-dimensional image data, and stores the existence range in a memory in a computer.

There are various methods for setting a lesion area.
Here, an area specifying method in which an operator specifies a lesion area on a tomographic image displayed on the display device will be described.
The treatment plan generally uses image data captured by an X-ray CT apparatus, which is composed of a plurality of tomographic images of a human body. Display the tomogram on the computer screen,
First, find the one that has the lesion. Then, a curve surrounding the lesion area is drawn on the tomographic image using a pointing device such as a mouse. At this time, a flag is set in a memory area corresponding to each point inside the curve to identify the area as a lesion area. This allows the computer to determine that the tissue is a focus tissue. This processing is performed over all the tomographic images where the lesion exists, and the three-dimensional existence range of the lesion region is specified. In addition, as a method for obtaining three-dimensional coordinates, there are other methods such as a method using a threshold value of image density and a semi-automatic extraction method such as a region expanding method using tissue connection information.

By the above method, for example, one lesion and a plurality of normal tissues are set. Then, data on the set organization is stored in an internal memory or an external storage device.

Next, the volume of the designated lesion area is calculated (S1502). Since the vertical, horizontal, and height lengths of the voxel are known in the image data, the lesion volume is calculated using the length and stored in the memory.
Here, since the volume is calculated using the water equivalent distance, the volume is obtained by weighting the density of each voxel. The water equivalent distance is a distance between two points when the density of the human body tissue is assumed to be equal to that of water. A conversion method for calculating how many values a given value corresponds to water density of 1.0 with respect to image data obtained by an X-ray CT apparatus is, for example, given by a predetermined function, and weights the converted density. By performing the line segment between two points, the water equivalent distance can be calculated.

Next, an initial irradiation direction is set (S150).
3). That is, the latitude θ and the longitude φ that define the irradiation direction used for the first calculation are set.

When the above preparation processing is completed, the SOBP width in each irradiation direction and the volume of the protruding portion in each irradiation direction are calculated based on the lesion shape information obtained in the lesion region setting processing (S1501). Then, processing for displaying those distribution maps is performed.

For this purpose, resampling is first performed based on the set irradiation direction (S1504). When an arbitrary irradiation direction is considered, in general, a direction that obliquely crosses the above-mentioned tomographic images may be targeted. In such a case, re-take the grid points along the irradiation direction,
Voxels need to be reordered. Such a process is called resampling. Resampling may be performed only in a limited range including a lesion, or may be performed on the entire image data. Due to the resampling, the range of existence of the lesion area is re-developed on a new grid point.

Next, the maximum length of the lesion is calculated using the resampled three-dimensional data (S1505).
In this case, first, the data resampled in the irradiation direction at the present time is scanned, the one having the maximum width in the depth direction of the lesion is searched, and the length is obtained as the water equivalent thickness. Then, the obtained maximum value is stored in a memory in combination with the irradiation direction.

Next, the focus projection area is calculated for the current irradiation direction (S1506). That is, the range of the lesion in the direction perpendicular to the current irradiation direction is specified,
The projected area of the lesion is determined and stored in a memory. Again, the projected area is calculated using the water equivalent distance.

Next, the volume of the protruding portion is calculated (S1507). That is, the product of the focus vertical length obtained in S1505 and the focus projecting area obtained in S1506 is obtained, and the focus volume obtained in S1502 is subtracted from the product.
Calculate the protruding partial volume. The obtained value is stored in a memory in combination with the current irradiation direction.

Next, for all the directions to be calculated,
It is determined whether the processing has been completed (S1508). The direction to be calculated here is a half of all directions in the three-dimensional space because the SOBP width and the volume of the protruding portion are equal in a certain irradiation direction and the direction opposite thereto.

If the result of the determination is that there is still a direction that has not been calculated (S1508: NO), the irradiation direction is changed (S1509). That is, according to the set resolution, the latitude θ representing the current irradiation direction by a certain angle increment
And the longitude φ are changed, and the SOBP width and the volume of the protruding portion are calculated again in the changed direction (S15).
04 to S1507).

On the other hand, if the calculation of the maximum length in the vertical direction of the lesion and the protruding partial volume has been completed for all the necessary directions (S1508: YES), the focal length stored in the memory in a format corresponding to the irradiation direction is obtained. The values of the maximum length in the direction and the protruding partial volume are read out, and are shown in FIGS.
(S1510). The SOBP distribution map and the distribution map of the protruding partial volume as shown in FIG.

FIG. 9 is a flow chart for explaining the display processing of the water equivalent thickness distribution map.

First, the above-mentioned S1501 and S1502
By the same processing as that described above, the lesion area setting processing S1601
Then, an initial irradiation direction setting process S1602 is performed.

When the lesion area setting process S1601 and the initial irradiation direction setting process S1602 are completed, the water equivalent thickness between the lesion and the body surface is calculated (S1603). That is,
In the irradiation direction at the present time, the water equivalent thickness up to a predetermined point in the lesion and the body surface is calculated. The obtained value is stored in a memory in combination with the current irradiation direction. As one point in the lesion, for example, the center of a rectangular parallelepiped circumscribing the lesion is selected.

Next, it is determined whether all the directions to be calculated have been calculated (S1604). Since the water equivalent thickness between the lesion and the body surface generally has no symmetry, the directions to be calculated are all directions in the three-dimensional space. As a result of the determination, if there is a direction that has not been calculated yet (S1604: NO),
The irradiation direction is changed (S1605). That is, the latitude θ and longitude φ representing the current irradiation direction are changed by a certain angle according to the set resolution, and the water equivalent thickness from the lesion to the body surface is calculated again in the changed direction.

On the other hand, when the calculation of the water equivalent thickness between the lesion and the body surface has been completed for all directions (S1604: Y
ES), a water equivalent thickness distribution map is displayed (S1606).
That is, the value of the water equivalent thickness between the lesion and the body surface stored in the memory in a format corresponding to the irradiation direction is read, and a distribution diagram as shown in FIG. 7 is displayed.

The display processing for displaying the SOBP distribution map, the protruding partial volume distribution map, and the water equivalent thickness distribution map has been described separately for convenience as the processing in FIG. 8 and the processing in FIG. , The SOBP distribution map, the protruding partial volume distribution map, and the water equivalent thickness distribution map may be displayed by different processes, or all of them may be displayed by one process.

Next, another embodiment of the present invention will be described. In this embodiment, in addition to the above-described distribution maps of the SOBP width, the volume of the protruding portion, and the water equivalent distance from the lesion to the body surface, three-dimensional display is also used. 3
The dimensional display refers to displaying a lesion and some normal tissues around the lesion in a two-dimensional projection plane with three-dimensional shading. This makes it easy to intuitively understand what direction a certain irradiation direction is with respect to the actual human body.

In this embodiment, the tissue and the proton beam are
Two-dimensionally superimposed, both are displayed translucently on a two-dimensional projection plane. When a certain irradiation direction is selected on the distribution map, a proton beam indicating the selected irradiation direction is superimposed on the human body tissue and three-dimensionally displayed. This makes it possible to intuitively grasp the direction.

Conversely, if the irradiation direction is designated in the three-dimensional display, the direction may be displayed with a mark on the distribution map. In this way, it is possible to make a quantitative judgment using the distribution map for the irradiation direction intuitively grasped.

It is assumed that an arbitrary number of proton beams can be generated centering on a lesion and each beam can be set in an arbitrary direction. The focus center point is assumed to be a diagonal intersection point of a rectangular parallelepiped circumscribing the focus as an initial position, and that position can be adjusted thereafter.

In the three-dimensional display, the object to be displayed can be displayed by rotating it arbitrarily, or can be cut at an arbitrary cross section to display the inside. In addition, display / non-display can be selected for an arbitrary organization among the organizations for which the area has been set.

FIG. 10 is a diagram showing a state of three-dimensional display. As shown in FIG.
2. Heart 803, left lung 804, right lung 805, and lesion 806 are three-dimensionally displayed. Further, a proton beam 808 is formed on the body surface 801 corresponding to an arrow 807 indicating the irradiation direction.
To the lesion 806. In the case of observing for confirming the irradiation direction, by rotating them in a three-dimensional space, the state of irradiation can be observed from any direction. When the irradiation direction is determined using the three-dimensional image, the direction is designated or changed by dragging the proton beam 808 with a mouse cursor or the like. If the irradiation direction is set in multiple directions, the specified number of proton beam 808
Is displayed, and each proton beam is operated using a mouse or the like as in the case of one.

As described above, by using the distribution map and the three-dimensional display together, it is possible to present quantitative information in the distribution map and qualitative information in the three-dimensional display. In other words, by presenting these two different pieces of information at the same time, these pieces of information having different properties complement each other, making it easier to determine the irradiation direction.

FIG. 1 shows an example of a display screen of the proton beam irradiation direction determination support system according to the present invention described above. As shown in the figure, this display screen includes a distribution map 101 of the SOBP width, a distribution map 102 of the volume of the protruding portion, a distribution map 103 of the water equivalent thickness from the lesion to the body surface, a display method selection button 104, and the number of contour lines. Scroll bar 105 for setting, contour line number initialization button 106, contour line color palette 10
7, contour line color setting area 108, contour line color initialization button 1
09, numerical value table 110, resolution setting scroll bar 111, three-dimensional display screen 112, link button 113,
3D image latitude rotation scroll bar 115, 3D image longitude rotation scroll bar 116, 3D image display target selection button 117, generate button 118, delete button 1
19, and a select / move button 120.
The operator performs operations such as picking and dragging on the operation target using a pointing device such as a mouse on this screen.

The display method selection button 104 is a toggle button for setting whether to display the distribution map in shades or contour lines. The scroll bar 105 for setting the number of contour lines is
This is for setting the number of contour lines. The contour line number initialization button 106 is used to initialize a set value. The operator selects a color from the contour line color palette 107 and places it in the contour line color setting area 108 to set the contour line color. The contour color is initialized by a contour color initialization button 109.

The numerical value table 110 includes distribution maps 101 to 1
03, and the irradiation direction selected by the operator on the three-dimensional display screen.
The OBP width, the volume of the protruding portion, and the water equivalent thickness of the lesion and the body surface are indicated by numerical values. These values are shown in each distribution chart 1
Those marked with 01, 102 and 103 are associated with reference numbers.

The resolution setting scroll bar 111 is used to change the latitude / longitude angle intervals of the distribution diagrams 101 to 103. The operator uses this scroll bar 1
When the resolution is changed by using 11, the respective values are calculated according to the changed resolution, and the distribution diagrams 101 to 103 are displayed at the changed resolution.

When the interlock button 113 is picked, the distribution maps 101, 102, and 103 are displayed on the three-dimensional display screen 112.
The proton beam 114 is displayed corresponding to the irradiation direction selected in. The direction of the proton beam 114 can be changed by dragging.
The corresponding marks 01, 102 and 103 also move. When the interlock button 113 is picked again, the interlock display is not performed thereafter. By operating the three-dimensional image latitude rotation scroll bar 115 and the three-dimensional image longitude rotation scroll bar 116, the entire display object in the three-dimensional display screen 112 can be rotated.

The three-dimensional image display target selection button 117 is
A toggle button for specifying which organ in the three-dimensional display screen 112 is to be displayed. When the user selects the three-dimensional image display target selection button 117 again, the display of the organ disappears.

After the generation button 118 is picked, if the mouse cursor is picked on the distribution charts 101, 102, 103 or the three-dimensional display screen 112, a mark or a proton beam 114 is generated accordingly. be able to. If the erase button 119 is picked, the mark selected in the distribution charts 101, 102, and 103 or the proton beam 114 selected in the three-dimensional display 112 can be erased.

When the select / move button 119 is picked, the distribution map 101, 102, 103 or the mark selected on the three-dimensional display screen 112 or the proton beam 1
14 can be linked or moved.

Next, an operation example of the proton beam irradiation direction determination support system will be described.

FIG. 11 is a diagram corresponding to the operator's instruction.
5 is a flowchart illustrating a process performed by the system.

First, when the system is started, the system calculates the SOBP width, the volume of the protruding portion, and the water equivalent thickness from the lesion to the body surface by the processing described with reference to FIGS. The distribution map is calculated and the distribution of each value is represented by a set of latitude and longitude, and displayed using contour lines or the like (S1101). In this case, when displaying the distribution map for the first time, calculation and display are performed using the resolution (angle increments of latitude and longitude), the number of contour lines, and the color of the contour lines. Calculate and display using the calculated values.

Next, it is determined whether or not the operator has instructed to change the parameter (S1102). That is, it is determined whether or not a change in the number of contour lines or the contour line color has been instructed. As a result of the determination, if a change has been instructed, subsequently, it is determined whether or not the instruction is an instruction for transition to the initial state, that is, whether or not an instruction to return the number of contour lines and the contour line color to the initial state has been issued. (S1103). As a result of the determination, when returning to the initial state, various parameters are returned to the initial values, and each distribution map is redrawn according to the initial values (S1101).

On the other hand, if the instruction is not an instruction for initial state transition, the number of contour lines is changed to the specified number (S11).
04), changing the contour line color to the selected color (S110)
5). Then, each distribution map is displayed again according to the changed values (S1101).

The operator who obtains the desired display by the above operation appropriately designates the desired irradiation direction at an arbitrary position in an arbitrary number (S1106 to S1107). The designated direction is marked on the screen by the system. At this time, when a certain irradiation direction is designated, the system also displays the corresponding direction in the distribution map having symmetry in consideration of the symmetry of the irradiation direction in the forward and reverse directions. At this time, the colors and shapes of the marks are displayed in such a manner that the irradiation directions having a symmetrical relationship with each other can be understood.

Further, the operator appropriately selects an irradiation direction to be linked with the three-dimensional display from the irradiation directions specified as candidates (S1108 to S1109). in this case,
It is also possible to select a plurality.

Next, it is determined whether or not the resolution of each distribution map, that is, the change of the latitude / longitude angle increment is instructed by the operator (S1110). As a result of the determination, if the change is instructed, the system changes the angle increment of the latitude and longitude of each distribution map (S1111), and calculates the SOBP width and the like based on the changed resolution (angle increment). , A distribution map is displayed (S1101).

On the other hand, when the change of the resolution is not instructed, it is further determined whether or not to interlock with the three-dimensional display (S1112). That is, by the operator,
It is determined whether or not the link between the selected irradiation direction and the three-dimensional display has been instructed. If the result of the determination is that linking has been instructed, three-dimensional display is performed in conjunction with the selected irradiation direction (S1113). On the three-dimensional display screen, display / non-display of the tissue set in the area setting process can be designated. The display object can be rotated in any direction.

The operator determines the optimum irradiation direction by comparing and examining the irradiation direction candidates through the above-described operation. If you decide the irradiation direction,
It is determined whether the SOBP width in the irradiation direction is stored in the storage device (S1114). As a result of the determination, when saving, the SOBP width is saved in the storage device (S11).
15). The SOBP width stored in this way is used for selection (and fabrication, if necessary) of the ridge filter used in the actual proton beam therapy.

Subsequently, it is determined whether or not the determined irradiation direction is stored in the storage device (S1116). If the result of determination is that the irradiation direction is to be stored, the irradiation direction is stored in the storage device (S
1117), the process ends. An actual proton beam therapy is performed based on the irradiation direction stored in this manner.
On the other hand, when not saving, the process ends as it is.

[0087]

As described above in detail, in the proton beam irradiation direction determination support system according to the present invention, the SOBP width required to cover the lesion, the volume of the protruding portion when the lesion is covered with SOBP, and the lesion And the distribution map of the water equivalent distance to the body surface are displayed.By comparing each distribution map while keeping in mind which ridge filters can be used or what kind of ridge filter should be manufactured, irradiation can be performed. In determining the direction, a quantitative judgment can be made. Further, by linking with the three-dimensional display, it is possible to interactively narrow down the final irradiation direction while intuitively grasping the irradiation direction.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a display screen of a proton beam irradiation direction determination support system according to the present invention.

FIG. 2 is a diagram showing a state of treatment by a proton beam treatment system.

FIG. 3 is a diagram illustrating a relationship between an irradiation direction, a shape of a lesion, and a protruding portion.

FIG. 4 is a diagram showing a coordinate system used in an embodiment of the present invention.

FIG. 5 is a diagram showing an example of a SOBP width distribution diagram.

FIG. 6 is a diagram showing an example of a protruding partial volume distribution diagram.

FIG. 7 is a diagram showing an example of a water equivalent thickness distribution map from a lesion to a body surface.

FIG. 8 is a flowchart showing a display process of an SOBP distribution map and a protruding partial volume distribution map.

FIG. 9 is a flowchart illustrating a display process of a water equivalent thickness distribution map.

FIG. 10 is a diagram showing an example of three-dimensional display.

FIG. 11 is a flowchart illustrating an operation of the system according to an instruction of an operator.

FIG. 12 illustrates a proton therapy system in which an embodiment of the present invention is utilized.

FIG. 13 is a diagram showing a computer system for realizing the system according to the present invention.

[Explanation of symbols]

 101 SOBP distribution map 102 Overhanging partial volume distribution map 103 Water equivalent thickness distribution map 104 Display method selection button 105 Scroll bar for setting the number of contour lines 106 Contour line number initialization button 107 Contour line color palette 108 Contour line color setting area 109 Contour line color initialization button 110 Numerical table 111 Resolution setting scroll bar 112 Three-dimensional display screen 113 Interlocking button 114 Proton beam 115 Three-dimensional image latitude rotation scroll bar 116 Three-dimensional image longitude rotation scroll bar 117 Three-dimensional image display target selection button 118 Generate button 119 Delete button 120 Select / Move button

Claims (12)

[Claims] 1. A system for supporting the determination of a proton beam irradiation direction, which is required to cover a plurality of irradiation directions by using shape information of a lesion to be irradiated with proton beams. A proton beam irradiation direction determination support system, comprising: a calculating unit that calculates a value of an enlarged Bragg peak width; and a display unit that displays a distribution map showing a distribution of the calculated values. 2. The calculating means further calculates a volume of an area which protrudes from the lesion when the lesion is covered using the calculated enlarged Bragg peak width, and the display means further calculates the volume. 2. The proton beam irradiation direction determination support system according to claim 1, wherein a distribution diagram showing a distribution of volume values is displayed. 3. The image processing apparatus according to claim 1, further comprising: input means for inputting image data including a lesion to be irradiated with proton beams; and extracting means for extracting shape information of the lesion from the image data. Claim 2
4. The proton beam irradiation direction determination support system according to 4. 4. The calculation means further calculates a water equivalent distance from a lesion to a body surface, and the display means further displays a distribution map showing a distribution of the calculated water equivalent distance. The proton beam irradiation direction determination support system according to claim 3. 5. The display means displays a mark at a position on the distribution map corresponding to the selected irradiation direction, and at a position having a symmetrical relationship when the values of the distribution map have symmetry with respect to the irradiation direction. The proton beam irradiation direction determination support system according to any one of claims 1 to 4, wherein: 6. The display means further displays a lesion and its surrounding tissue and a proton beam three-dimensionally, and indicates that the direction of the three-dimensionally displayed proton beam and the mark on the distribution map are linked. The proton beam irradiation direction determination support system according to claim 5. 7. The display means further includes a latitude and longitude value of the selected irradiation direction, a value of an enlarged Bragg peak width corresponding to the irradiation direction, and a region where the lesion and the enlarged Bragg peak width cover the periphery of the lesion. 5. The proton beam irradiation direction determination support system according to claim 4, wherein a value of a volume difference from the target and a value of a water equivalent distance from a lesion center to a body surface are displayed. 6. 8. When the enlarged Bragg peak width that can be adopted in proton beam therapy is limited, the display unit specially displays an irradiation direction corresponding to the enlarged Bragg peak width on a distribution map. The proton beam irradiation direction determination support system according to any one of claims 1 to 7. 9. A method for supporting determination of a proton beam irradiation direction, which is required to cover a lesion in a plurality of irradiation directions by using shape information of a lesion to be irradiated with a proton beam. A method for determining a direction of proton beam irradiation, comprising: calculating a value of an enlarged Bragg peak width; and displaying a distribution map showing a distribution of the calculated values. 10. A step of calculating, for a plurality of irradiation directions, a volume of a region protruding from the lesion when the lesion is covered using the calculated enlarged Bragg peak width, and showing a distribution of the calculated volume value. The method according to claim 9, further comprising the step of displaying a distribution map. 11. The method according to claim 9, further comprising: inputting image data including a lesion to be irradiated with proton beams; and extracting shape information of the lesion from the image data. 1
0. The method for supporting the determination of the irradiation direction of proton beams according to 0. 12. The method further comprises: calculating a water equivalent distance from a lesion to a body surface for a plurality of irradiation directions; and displaying a distribution map showing a distribution of the calculated water equivalent distance. The method for determining the direction of irradiation of proton beams according to claim 11.