JP5401391B2 - Particle beam therapy planning apparatus and therapy planning method - Google Patents

Description

  The present invention relates to a particle beam therapy planning apparatus and therapy planning method for a particle beam therapy apparatus used for cancer therapy and the like.

  In the particle beam therapy, treatment is performed by irradiating a target tumor cell with a particle beam (a charged particle beam such as a proton beam or a carbon beam). X-rays are the most widely used radiation therapy, but there is an increasing demand for cancer treatments using proton beams and particle beams typified by carbon beams that have high dose concentration to the target. .

Excessive irradiation and insufficient dose may lead to side effects on normal tissues other than tumors and tumor recurrence. Also in the particle beam therapy system, it is required to irradiate a designated dose so as to concentrate on the tumor region as accurately as possible. In the particle beam therapy, the use of the scanning method is spreading as a method of concentrating the dose. This is a method in which a thin particle beam is deflected by two sets of scanning electromagnets and guided to an arbitrary position in a plane, so that irradiation is performed so as to fill the inside of the tumor, and a high dose is given only to the tumor region.
In the case of the scanning method, a patient-specific instrument such as a collimator for shaping the distribution into a tumor shape is basically unnecessary. Further, there is an advantage that various distributions can be formed.

  In order to realize this, a process of creating a plan using a treatment planning apparatus before actual irradiation is extremely important. The treatment planning apparatus simulates the dose distribution in the patient body by numerical calculation based on the information in the patient body obtained from the CT image or the like. The operator determines irradiation conditions such as the direction of beam irradiation, beam energy, irradiation position, and dose while referring to the calculation result of the treatment planning apparatus. The general process is briefly described below.

  The operator first inputs a target area to be irradiated with the particle beam from the input device. Mainly, using a CT image of a patient displayed on a display device, a target region is input to each slice of the CT image. The input data is stored as three-dimensional region data by the operator registering in the treatment planning apparatus. If necessary, enter and register the positions of important organs where the radiation dose should be kept as low as possible.

  The beam irradiation position (hereinafter referred to as a spot) for realizing the dose distribution designated by the operator and the amount to be irradiated are determined by the treatment planning apparatus. Usually, the spot position is determined first, and then the dose for each spot is determined so as to satisfy the dose distribution condition input by the operator. Here, the spot position determination process will be described in detail. The process of determining the dose is detailed in Non-Patent Document 1, for example.

  In scanning irradiation, after irradiating a specified amount of beam to a certain point, the beam is stopped once, moved to the next point to be irradiated and then irradiated again, and the beam is also moved while moving the irradiation position. There is a raster system that does not stop. Here, description will be made on the premise of the spot scanning method.

  The spot position in the plane perpendicular to the beam traveling direction is determined by the amount of excitation of the scanning electromagnet. The dose distribution in the traveling direction of the particle beam gives most of the dose near the peak that appears just before the beam stops. This position is considered as a spot position with respect to the beam traveling direction. This spot position is arranged so as to cover the target area stored as three-dimensional area data.

  In the spot scanning method, spot positions are determined discretely. The interval between adjacent spots in the lateral direction (direction perpendicular to the beam traveling direction) is determined by the beam size. FIG. 10 schematically shows this state. As shown in FIG. 10, the dose distribution in the horizontal direction can be approximated by a Gaussian distribution shape, and 1001 represents the dose distribution by the spot at the end. Reference numerals 1002, 1003, and 1004 denote dose distributions by spots arranged so as to be arranged on the right side of the spot represented by 1001. Actually, a spot also exists on the right side of 1004. The interval between adjacent spots is d, and the individual beam size is σ. The sum of the dose distribution by the beam irradiated to these spots is 1005. In FIG. 10, the interval d is approximately the same as the beam size σ, but if the interval d is about 1.5 times or less of the beam size σ, the total dose distribution 1005 does not appear uneven, and a uniform region 1006 is formed. Is done.

  The spot interval d is arranged at a constant interval for beams having the same energy. For example, in Patent Document 1, control is performed so that the interval is different for each beam having different energy, but the spot interval in a plane irradiated with the same energy is constant. In Patent Document 2, the beam size of the particle beam at the irradiation region boundary is controlled to be small, but the interval between the beams irradiated under the same conditions is constant.

JP 2000-162391 A JP 2001-212253 A

Lomax A: Intensity modulation methods for proton radiotherapy, Phys. Med. Biol. 44, 185-205, 1999.

  In a charged particle beam with low energy, scattering in the irradiation apparatus or the patient's body is large, and the beam size is large. In this case, the spot interval can be set large to the same extent. A larger spot interval reduces the number of spots and contributes to a reduction in the overall irradiation time.

  However, when the spot interval is increased, there are the following problems. In FIG. 10, a region 1006 where the integrated dose 1005 indicating the total dose of the charged particle beam irradiated to the patient is uniform is about twice the beam size σ from the center position of the spot located at the end. It becomes inside rather than the position where it entered. That is, in order to ensure a uniform distribution within the target, it is necessary to irradiate the beam also outside the target. Therefore, when the treatment planning apparatus places a spot, a margin of 2 to 3 times the spot size is added outside the area where a uniform dose is to be ensured, and the spot position falls within the area including this margin. Consider the condition of selecting.

  In FIG. 11, an area including a margin is represented by 1102. In the condition of FIG. 11A, the region 1006 where the dose distribution 1005 is uniform and the target region 1101 substantially coincide. However, in some cases, the situation as shown in FIG. In FIG. 11B, the uniformity of the target area 1006 is ensured, but the same dose as that in the target area 1101 is also irradiated in the non-target area 1103 where the irradiation dose is desired to be reduced as much as possible.

If you try to secure a uniform dose distribution within the target by fixing the spot spacing for charged particle beams of the same energy, a high-dose region may be formed outside the originally required position. . In order to prevent this, it is necessary to reduce the spot interval. However, since the number of spots increases, it works in the direction of extending the irradiation time. Further, Patent Document 2 discloses a treatment planning method in which a spot diameter is changed in each region by grouping the vicinity of the irradiation region boundary and other regions. In this treatment planning method, the spot diameter entering the vicinity of the irradiation area boundary is set smaller than the spot diameters of other areas, thereby ensuring a uniform dose distribution within the target.
In the method as disclosed in Patent Document 2, a device for switching the beam diameter is required, and the configuration and control become complicated.

  The above-described problems include a target area input unit that inputs a target area to be irradiated with a particle beam, an irradiation area setting unit that sets an irradiation area that includes the target area, and an irradiation spot that irradiates a particle beam within the irradiation area And determining an irradiation spot such that the calculation device arranges the irradiation spot on the outline of the irradiation area and the interval between adjacent irradiation spots is equal to or less than a predetermined set value. Can be solved by.

  According to the present invention, it is possible to provide treatment plan information capable of forming a desired dose distribution without complicating the device configuration.

It is a figure showing the flow until a treatment plan is drawn up by suitable one Embodiment of this invention. It is a figure showing the flow of this invention apparatus in suitable one Embodiment of this invention. It is explanatory drawing which shows the structure of the treatment plan apparatus which is preferable one Embodiment of this invention. It is a figure explaining the input of the target area | region within the slice of CT data. It is explanatory drawing which shows the procedure of the method of calculating the energy of the particle beam in an Example. It is explanatory drawing which shows the procedure of the method of calculating the information of the stop position of the particle beam in an Example. It is a figure showing the target shape in the stop position of the particle beam extracted by the method of the Example. It is explanatory drawing which shows the procedure of the method of calculating the spot space | interval of the Y direction within a target area | region. It is explanatory drawing which shows the procedure of the method of calculating the spot space | interval of the Y direction within a target area | region. It is a conceptual diagram showing a mode that uniform dose distribution is formed with a some spot. It is a conceptual diagram showing the relationship between the uniform area | region of FIG. 10, and a target area | region. It is a conceptual diagram showing the display method of dose distribution. It is a figure showing the example of DVH.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

〔Example〕
A treatment planning apparatus which is a preferred embodiment of the present embodiment will be described with reference to FIGS. 1 and 2. The treatment planning apparatus of the present embodiment draws up a treatment plan for particle beam treatment by the scanning irradiation method.
FIG. 1 is a diagram showing a flow of treatment planning when the treatment planning apparatus of the present embodiment is used. FIG. 2 is a diagram illustrating a processing flow of the treatment planning apparatus according to the present embodiment. FIG. 3 is a diagram illustrating an overall configuration of the treatment planning apparatus.

As shown in FIG. 3, the treatment planning apparatus 301 includes an input device 302, a display device 303, a memory 304, an arithmetic processing device 305, and a communication device 306. An arithmetic processing device 305 is connected to the input device 302, the display device 303, the memory (storage device) 304, and the communication device 306.
The treatment planning apparatus 301 is connected to the data server 307 via a network. Specifically, the communication device 306 of the treatment planning device 301 is connected to the data server 307 via the network and exchanges data.

  A patient to be treated has previously taken a CT image for treatment planning using a CT apparatus. Data (CT data) related to the CT image for treatment planning imaged by the CT apparatus is stored in the data server 307. This CT data is three-dimensional data in which CT values are recorded for each small area called a voxel. The treatment planning apparatus 301 makes a treatment plan using this CT data.

  When a medical worker (engineer or doctor) who is an operator inputs patient information (patient ID) from the input device 302, the treatment planning device 301 starts creating treatment plan information of the patient corresponding to the patient ID (step) 101). First, the input device 302 outputs the input patient ID to the arithmetic processing device 305. The arithmetic processing unit 305 reads CT data of the target patient from the data server 307 based on the input patient ID. That is, the treatment planning apparatus 301 receives the CT data of the patient corresponding to the patient ID from the data server 307 through the network connected to the communication apparatus 306 and stores it in the memory 304. Further, the treatment planning apparatus 301 creates a CT image for treatment planning based on the received CT data, and displays it on the display device 303. The display device 303 displays an image in each slice (each layer) obtained by dividing the region including the affected area of the patient into a plurality of layers.

  The operator inputs an area (target area) to be designated as a target for each slice of the CT image using the input device 302 (device such as a mouse) while checking the CT image displayed on the display device 303. To do. The target area is an area that is determined to be irradiated with a particle beam, for example, including an area that the operator has determined to be a cancerous part of a patient. When the input of the target area for all slices is completed, the operator inputs an input end signal from the input device 302. When receiving the input end signal, the treatment planning apparatus 301 stores and registers the information of the target area in all slices in the memory 304 (step 102). Information registered in the memory 304 is three-dimensional position information indicating the target area input by the operator. If there is an important organ in the vicinity of the target area where the irradiation dose should be suppressed as much as possible, or if there is another area that needs to be evaluated or controlled, the operator can select these based on the image information displayed on the display device 303. The position information of the important organs is input from the input device 302. The position information of the important organs and the like is stored and registered in the memory 304 as with the target area information. FIG. 4 shows an example in which the display unit 303 displays the input target region 402 and the region 403 such as an important organ in an arbitrary slice (layer) 401 including the affected part, which is generated based on the CT data.

  Next, the process proceeds to a step of determining irradiation conditions for irradiating the target region 402 with the charged particle beam (step 103). The irradiation conditions to be determined by the operator include the irradiation direction and the number of irradiation gates for irradiating the charged particle beam, the irradiation dose of the charged particle beam for irradiating the target region, and the like. Irradiation conditions input from the input device 302 by the operator are stored in the memory 304. The treatment planning apparatus 301 of the present embodiment can change the interval between scanning irradiation spots (the interval between the irradiation spot irradiated with a charged particle beam with the same energy beam and the irradiation spot arranged next to the irradiation spot). It has a configuration. Specifically, the treatment planning device 301 holds an appropriate value (desired value) as an initial value of the spot interval. However, when the operator wants to change the spot interval from the initial value to another value, the input device By inputting the value from 302, the spot interval is changed. This spot interval may be set to the same value for all energy, or may be set by inputting different values for each energy.

  When the setting of the above irradiation conditions (step 103) is completed, the treatment planning apparatus 301 obtains treatment plan information according to an instruction from the operator (step 104). This treatment plan information includes information on the spot position of the charged particle beam irradiated to the patient and information on the target dose at each spot. A feature of the present embodiment is a spot position calculation method calculated by the treatment planning apparatus 301. The detailed flow of the spot position calculation method will be described with reference to FIG. Here, the spot position of the charged particle beam is determined by the amount of excitation to the scanning electromagnet and the energy of the charged particle beam. In the present embodiment, description will be made assuming that a charged particle beam is irradiated from only a single direction. However, in the case where irradiation is performed from a plurality of directions, the same processing is performed for each direction. The same effect can be obtained.

  First, the treatment planning apparatus 301 outputs the CT data of the patient and the information on the target area of the patient stored in the memory 304 to the arithmetic processing apparatus 305. In the scanning irradiation method, the trajectory of the charged particle beam is deflected by a scanning electromagnet. For this reason, the charged particle beam irradiated to each spot position does not become parallel, but is irradiated as a charged particle beam having a radiation source at a certain position. This is shown in FIG. In the particle beam therapy system, a point 501 called an isocenter, which is the center position of the apparatus, is defined, and positioning is usually performed so that this position coincides with the center of the target region 402. The treatment planning apparatus 301 holds the distance between the isocenter 501 and the radiation source 502.

  The arithmetic processing unit 305 of the treatment planning apparatus 301 first selects beam energy. The arithmetic processing unit 305 reads information on the angle at which the charged particle beam is irradiated among the irradiation condition information stored in the memory 304. Subsequently, the arithmetic processing unit 305 defines a surface 503 perpendicular to the straight line connecting the radiation source 502 and the isocenter 501, and divides the surface 503 with an appropriate resolution (usually several mm or less). Each divided area is called a pixel. Subsequently, the arithmetic processing unit 305 performs the voxel conversion of the CT data for each determined step (usually the same size as the pixel 504) along the straight line 505 connecting the center positions of the pixels 504 from the radiation source 502 side. Accumulate values. At this time, the CT value held in each voxel is integrated after being converted into a thickness when the substance in the voxel is converted into water by a table stored in the memory 304 of the treatment planning apparatus 301 in advance. This is called water equivalent thickness. The conversion from the CT value to the water equivalent thickness may be performed collectively before the calculation. The arithmetic unit 305 performs the same calculation for all the pixels obtained by dividing the plane 503 perpendicular to the beam traveling direction. By this operation, a water equivalent depth at an arbitrary position in the target region 402 is calculated.

  The arithmetic processing unit 305 calculates the position within the target and having the longest water equivalent distance on the trajectory along all the pixels obtained by dividing the plane 503 perpendicular to the beam traveling direction. If the energy at which the peak comes at this position is selected, the beam having the largest energy necessary for target irradiation is obtained. However, the particle beam therapy system is not capable of irradiating a charged particle beam having a continuous energy, and normally irradiates a charged particle beam having a discrete, determined value of energy. This energy list is held by the treatment planning apparatus 301. If there is no energy whose peak position matches the deepest depth in the target obtained here, the particle beam therapy system may insert a range shifter in front of the patient and finely adjust the stop position of the charged particle beam. It becomes possible. The treatment planning device 301 also calculates the thickness of the range shifter if necessary.

  Similarly, the lowest energy can be selected by the operation for obtaining the distance at which the target area 402 is at the shallowest position (step 202). In order to ensure a high dose area within the target, the number of energies may be increased by providing a margin for the maximum and minimum energy thus obtained.

  When the maximum energy and the minimum energy of the charged particle beam necessary for irradiating the target region 402 are determined, the spot positions are sequentially determined for all the charged particle beams having energy therebetween. Hereinafter, a procedure for selecting a spot position when a certain energy is selected will be described.

  It is assumed that a charged particle beam having a certain energy is selected (step 203). The arithmetic processing unit 305 determines the depth of the stop position of the energy beam (the position where the peak appears in the dose distribution) for the charged particle beam having the currently selected energy from a table held in the memory 304. read out. Subsequently, with respect to all the pixels obtained by dividing the plane 503 perpendicular to the beam traveling direction shown in FIG. 5, the depth equivalent to the water equivalent from the source 502 matches the stop position of the selected charged particle beam. Is calculated. This is shown in FIG. In FIG. 6, the water equivalent depth from the radiation source 502 is integrated along the straight line 602 for the pixel 601. This calculation may be performed while newly reading CT data from the source position, but the result calculated in step 202 may be used. When the position 603 that matches the stop position of the charged particle beam is obtained, the arithmetic processing unit 305 determines whether the position is inside or outside the target in the original CT data, and stores the result. . This is done for all pixels (step 204).

  The result of step 204 is as shown in FIG. For every pixel on the surface 503, it is recorded whether the currently selected beam stop position is within the target. In FIG. 7, reference numeral 701 denotes an area where the beam stop position is within the target, and 702 denotes an area where the beam stop position is outside the target. It can be said that the region 701 in the target is a shape obtained by projecting the target shape at the beam stop position onto a surface 503 that passes through the isocenter 501 and is perpendicular to the beam irradiation surface. For the region 701 in the target, the arithmetic processing unit 305 determines the spot position, that is, the excitation amount of the scanning magnet.

  In FIG. 7, the horizontal direction is defined as the X direction, and the vertical direction is defined as the Y direction. First, the arithmetic processing unit 305 determines from the spot interval in the Y direction. As described with reference to FIG. 11, it is difficult to form a uniform distribution in the target if the irradiation spot (irradiation position) is arranged only in the target region. Therefore, the arithmetic processing unit 305 determines an irradiation region 801 (FIG. 8) obtained by enlarging the region 701 by a width two to three times the beam size (step 205). This irradiation region 801 is a region including the target region. Further, the outermost dotted line of the irradiation region 801 shown in FIG. The arithmetic processing unit 305 may arrange the irradiation spots so that the irradiation spots appear only in the irradiation area 801. The enlargement amount here may be automatically calculated by the treatment planning device 301, or an operator can directly input a value from the input device 302. Here, the irradiation region 801 is set by expanding the region in the direction perpendicular to the beam traveling direction, but an irradiation region expanded in the beam traveling direction may be employed. In this case, the operation for enlarging the area needs to be performed before step 202.

When the irradiation area 801 is determined, the arithmetic processing unit 305 obtains a point 802 at the largest coordinate in the Y direction and a point 803 at the smallest coordinate in the irradiation area 801. The Y coordinate of the largest coordinate point 802 is Ymax, and the Y coordinate of the smallest coordinate point 803 is Ymin. The treatment planning apparatus 301 calculates the spot interval Dy in the Y direction by using (Expression 1) using the arithmetic processing apparatus 305 (step 206).
Dy = (Ymax−Ymin) / [(Ymax−Ymin) / D] (Formula 1)

  D in (Expression 1) is the spot interval set in step 103. When the calculation result in [] on the right side of (Expression 1) is x, [x] represents the smallest integer equal to or greater than x. By doing so, since Dy is always equal to or less than D, it is possible to avoid that the interval is widened beyond the set value D and a uniform dose distribution cannot be obtained. When Dy is obtained, scanning lines are arranged at intervals of Dy from the position of Ymin to the position of Ymax (step 207). That is, the arithmetic unit 305 sets the scan lines so that the interval between adjacent scan lines (the interval between a scan line and the scan line arranged next to it) is equal to or less than a predetermined set value D. decide. Irradiation spots are arranged on this scanning line.

FIG. 9 shows the positions of the scanning lines where the irradiation spots are arranged in this way. Next, a spot position is arranged on the scanning line. Consider a state in which a certain scanning line 901 is selected (step 208). Among the points on the line that are present in the irradiation region 801, a point 902 having the smallest X coordinate and a point 903 having the largest X coordinate are searched. The X coordinate of the point 902 having the smallest X coordinate is Xmin, and the X coordinate of the point 903 having the largest X coordinate is Xmax. The treatment planning device 301 uses the arithmetic processing device 305 to calculate the spot distance Dx in the X direction according to (Equation 2) (step 209).
Dx = (Xmax−Xmin) / [(Xmax−Xmin) / D] (Formula 2)

  When calculating Dx using (Equation 2), the arithmetic processing unit 305 arranges spots at intervals Dx from Xmin to Xmax (step 210). As a result, the spot position on the line 901 is determined. This operation is performed on all the scanning lines obtained in step 207 (step 211). By determining the irradiation spot in this way, the treatment planning apparatus 301 of the present embodiment sets a spot position on the contour of the irradiation area 801 and sets a predetermined interval between adjacent spot positions. The spot position is determined so as to be a value smaller than D. Further, in different scanning lines, the value of Dx obtained by (Equation 2) is also different. That is, according to the treatment planning apparatus 301 of the present embodiment, the interval between the irradiation spot is different for each scanning line.

  When the above operation for a certain energy (steps 203 to 211) is completed, one lower energy is selected and the same operation is performed (step 212). When this is performed until the minimum energy determined in step 203 is reached, the selection of the spot position ends (step 213).

  When the spot position is determined, the treatment planning device 301 starts the optimization calculation of the irradiation amount as it is. The treatment planning apparatus 301 determines the irradiation amount of the charged particle beam to each irradiation spot so as to approach the uniform dose distribution to the target set in step 103. In this calculation, a method using an objective function in which a deviation from a target dose with the irradiation dose for each spot as a parameter is quantified is widely adopted. The objective function is defined so that the dose distribution becomes small enough to meet the target dose. By searching for the dose that minimizes the dose function by iterative calculation, the optimal charged particle beam A target dose is calculated.

  When the target dose is determined by iterative calculation, the treatment planning apparatus 301 calculates a dose distribution by using the finally obtained spot position and the target dose for each spot. The calculated result is displayed on the display device 303. A display example on the display device 303 is shown in FIG. In FIG. 12A, the dose distribution at the slice 401 in the CT data of FIG. 4 is represented using an isodose line 1201. The isodose line 1201 is obtained by connecting equal dose positions with a line, and a plurality of isodose lines are drawn for each dose as shown in the figure. Isodose lines corresponding to different doses are distinguished by color coding. The operator determines on the display device 303 whether the isodose line corresponding to the designated dose covers the target area without excess or deficiency.

  In addition, as shown in FIG. 12B, it is possible to display the position of the spot superimposed on the isodose line. For example, a point 1202 in FIG. 12B indicates that a spot exists at this position. The irradiation amount for each spot can also be displayed by the size or color of the points. In the example of FIG. 12B, the size of the point is proportional to the irradiation amount of the corresponding spot. Not only the irradiation amount but also the energy of the beam irradiated to each spot can be represented by the color or shape of the point.

  A histogram called DVH (Dose Volume Histogram) shown in FIG. 13 is also widely used for confirming the dose distribution to the target area. In the graph of FIG. 13, the volume of the region in the target to which a dose equal to or greater than the value indicated by the horizontal axis (or the ratio to the target volume) is the vertical axis. The treatment planning device 301 calculates the DVH value using the arithmetic processing device 305 and displays it on the display device 303.

  The operator analyzes the dose distribution result using the isodose line 1201 and DVH displayed on the display device 303, and determines whether or not the dose distribution satisfies the target condition (step 106). If the distribution is not desirable, the process returns to step 103 to reset the irradiation conditions. This includes changing the irradiation direction and spot spacing. When the condition is changed, the treatment planning device 301 calculates the spot position and the dose according to the operator's instruction, and the new dose distribution result is displayed on the display device 303. When a desired result is obtained, the treatment planning is completed (step 107). The obtained irradiation conditions are stored in the data server 307 through the network.

According to the present embodiment, by obtaining an interval that optimally fits the tumor position, it is possible to reduce the irradiation amount outside the target to the maximum even when the spot interval is large.
The arithmetic unit 305 of the present embodiment arranges the irradiation spot on the outline of the irradiation region that includes the target region, and the interval between the adjacent irradiation spots is equal to or smaller than a predetermined set value D. The irradiation spot is determined for each scanning line. In this way, by extracting the target area shape near the stop position of the particle beam and changing the spot interval so that a uniform high-dose area is formed in this target area depending on the position in the irradiation area. In addition, it is possible to suppress the deviation between the high-dose region and the target region where the irradiation dose of the particle beam in the target region is uniform.

301 treatment planning device 302 input device 303 display device 304 memory 305 arithmetic processing device 306 communication device 307 data server 401 slice of CT data 402 target region 501 isocenter 502 radiation source 503 planes 504 and 601 planes 503 perpendicular to the beam traveling direction One of the pixels 505 A straight line 602 connecting the center positions of the points 502 and 504 A straight line 603 connecting the center positions of the points 502 and 601 A point 701 corresponding to the beam stop position on the straight line 602 A region where the beam stop position is within the target region 702 A region where the beam stop position is outside the target region 801 A region obtained by enlarging the region 701 (irradiation region)
802 Point 803 having the largest Y coordinate in the region 801 Point 901 having the smallest Y coordinate in the region 801 Line 902 on which a spot parallel to the X axis is arranged Point 903 having the largest X coordinate on the line 901 Most point on the line 901 Point with small X coordinate

Claims (9)

Target area input means for inputting a target area to be irradiated with a particle beam;
In an irradiation region set to include the target region, comprising an arithmetic unit that determines an irradiation spot that irradiates the particle beam,
The arithmetic unit is:
Wherein the irradiation spot located on the contour of the irradiation region, the spacing of the irradiation spots adjacent in the direction of scanning the particle beam, the Do so that the following predetermined set value, the said exposure area A treatment planning apparatus that calculates for each scanning line based on a length of a line that scans a particle beam, and determines an arrangement of the irradiation spots according to the calculated interval . The arithmetic unit is:
The interval between lines for scanning the particle beam is determined based on a width of the irradiation region in a direction perpendicular to the scanning direction of the particle beam and the predetermined setting value. Treatment planning device.   The treatment planning apparatus according to claim 1, further comprising a display device that displays the target area and the irradiation spot input by the target area input unit. The arithmetic unit is:
Determining a target dose value for each of the irradiation spots;
The treatment planning apparatus according to claim 3, wherein the display device further displays information on the target irradiation dose value determined by the arithmetic device. The arithmetic unit is:
Determining a target irradiation dose value for each of the irradiation spots, calculating a dose distribution to the target when irradiated with the target irradiation dose;
The treatment planning apparatus according to claim 3, wherein the display device further displays the dose distribution calculated by the arithmetic device. The arithmetic unit is:
The treatment planning apparatus according to claim 5, wherein the target irradiation dose value for each of the irradiation spots is obtained so that a dose distribution to the target falls within an allowable range. A treatment planning apparatus creates treatment plan information used for a particle beam irradiation system,
The treatment planning apparatus includes an arithmetic unit that determines an irradiation spot that irradiates the particle beam in a target region that is a target that irradiates the particle beam,
The arithmetic unit is:
Wherein the irradiation spot located on the contour of the irradiation region, the spacing of the irradiation spots adjacent in the direction of scanning the particle beam, the Do so that the following predetermined set value, the said exposure area A method of creating treatment plan information , comprising: calculating for each scanning line based on a length of a line scanning a particle beam, and determining an arrangement of the irradiation spot according to the calculated interval . The arithmetic unit is:
The line interval for scanning the particle beam is determined based on a width of the irradiation region in a direction perpendicular to the scanning direction of the particle beam and the predetermined set value. To create treatment plan information . The arithmetic unit is:
Determining a target dose value for each of the irradiation spots;
9. The method of creating treatment plan information according to claim 8, wherein information on the determined target irradiation dose value is displayed on a display device.

Images