JP2023038962A - Radiotherapy system - Google Patents

Abstract

To provide a radiotherapy system capable of shortening a time required for re-planning of an adaptive treatment more than before.SOLUTION: A radiotherapy system 1 for emitting radiation performs first calculation that creates a new image on the basis of on an image during treatment planning and another image newer than the image during the treatment planning, performs second calculation creating a target dose distribution on the basis of the image during the treatment planning, a dose distribution, and the another image newer than the image during the treatment planning, and optimizes an irradiation parameter with the target dose distribution as a target.SELECTED DRAWING: Figure 4

Description

TECHNICAL FIELD The present invention relates to a radiotherapy system that treats an affected area such as a tumor by irradiating it with radiation such as particle beams.

A method of irradiating a patient with cancer or the like with radiation such as particle beams and X-rays is known. Particle beams include proton beams and carbon beams. A radiotherapy system used for irradiation forms a dose distribution suitable for the shape of a target such as a tumor inside the body of a patient fixed on a patient bed called a couch.

The internal conditions of the patient change day by day, such as changes in the shape of the target and changes in gas pockets in the intestinal tract. In order to improve irradiation accuracy, adaptive treatment, which recreates a treatment plan according to the patient's internal condition on the day of treatment, is becoming popular. In particular, on-line adaptive therapy refers to therapy that re-plans the treatment plan while the patient is fixed on the couch on the day of treatment.

Non-Patent Document 1 discloses a technique for determining the irradiation dose in online adaptive treatment in which a treatment plan is recreated on the spot according to the patient's internal condition on the day of treatment. In adaptive therapy, it is important to recreate the treatment plan so that the effect is equivalent to the originally planned original treatment plan. Non-Patent Literature 1 discloses a method of modifying the dose distribution according to the image on the day of treatment and determining the dose so as to reproduce the dose distribution as a target.

Phys. Med. Biol. 63 (2018) 085018

In the method of Non-Patent Document 1, the dose distribution of the original treatment plan is deformed according to the image of the treatment day, and the irradiation parameters are optimized to realize the deformed dose distribution. For example, maximum and minimum doses to the target and surrounding normal organs can be re-planned to be equivalent to the original treatment plan.

On the other hand, since the target dose distribution is determined by the deformation, it was clarified that the desired dose distribution may not be obtained depending on the deformation result.

Specifically, it is possible to obtain a dose distribution with a narrow high-dose area outside the target, which ensures robustness against misalignment, and a dose distribution with a steep dose gradient that is difficult to achieve by optimizing irradiation parameters. . If the desired target dose distribution cannot be obtained, the number of iterations of optimization may increase and the time required for replanning may increase. Further improvements are desired to further reduce the burden on patients.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a radiotherapy system capable of shortening the time required for replanning adaptive treatment compared with the conventional system.

The present invention includes a plurality of means for solving the above problems. One example is a radiotherapy system for irradiating radiation, which comprises an image at the time of treatment planning and an image newer than the image at the time of treatment planning. performing a first calculation to create a new image based on the alternate image, and a target target based on the planning image, the dose distribution, and the alternate image newer than the planning image; A second calculation is performed to create a dose distribution, and irradiation parameters are optimized with the target dose distribution as a target.

According to the present invention, adaptive therapy can be shortened compared to the conventional method. Problems, configurations and effects other than those described above will be clarified by the following description of the embodiments.

1 is an overall configuration diagram of a radiotherapy system according to Example 1. FIG. 2 is a schematic diagram of software used in the replanning system of the radiotherapy system according to Example 1; FIG. 4 is a flow chart at the time of re-planning in the radiotherapy system according to Example 1. FIG. It is a figure which shows the data flow from step S101 to step S104 of FIG. FIG. 4 is a diagram showing a data flow during replanning in a general radiotherapy system; It is an example of a cross-sectional image in the body axis direction of a treatment planning image in the radiotherapy system according to the embodiment. It is an example of the dose distribution of the treatment plan in the radiotherapy system according to the embodiment. It is an example of a cross-sectional image in the body axis direction of a treatment planning image in the radiotherapy system according to the embodiment. It is an example of a cross-sectional image in the body axis direction of a treatment day image in the radiotherapy system according to the embodiment. It is an example of a cross-sectional image in the body axis direction of a treatment day image in the radiotherapy system according to the embodiment. It is an example of a setting screen of the workflow manager 10 in the radiotherapy system according to the embodiment. It is an example of the result of creating a target dose distribution in a general radiotherapy system. It is an example of the result of creating a target dose distribution in the radiotherapy system according to the example.

An embodiment of the radiotherapy system of the present invention will be described below with reference to the drawings. The following description and drawings are examples for explaining the present invention, and are appropriately omitted and simplified for clarity of explanation. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

In the drawings for explaining the embodiments, portions having the same functions are denoted by the same reference numerals, and repeated description thereof will be omitted.

The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention. As such, the present invention is not necessarily limited to the locations, sizes, shapes, extents, etc., disclosed in the drawings.

When there are a plurality of components having the same or similar functions, they may be described with the same reference numerals and different suffixes. However, if there is no need to distinguish between these multiple constituent elements, the subscripts may be omitted in the description.

<Example 1>
Embodiment 1 of the radiotherapy system of the present invention will be described with reference to FIGS. 1 to 13. FIG.

First, the overall configuration of the radiotherapy system will be described with reference to FIG. FIG. 1 is an overall configuration diagram of a radiotherapy system according to a first embodiment.

The radiotherapy system 1 according to the first embodiment, as shown in FIG. An irradiation device 30 , an irradiation control device 31 , a rotating gantry 40 , a gantry control device 41 , a couch 50 and a couch control device 51 are provided.

A bed on which the patient 60 is placed is called a couch 50 . Couch 50 can move in directions of three orthogonal axes and can rotate about each axis based on instructions from couch control device 51 . These movements and rotations can move the position of the target 61 to a desired position.

The imaging device 20 measures three-dimensional images of a patient 60 and a target 61 fixed to the couch 50 based on instructions from the imaging control device 21 . A three-dimensional image is a CT image, a cone beam CT image, or an MRI image, and is hereinafter referred to as a treatment day image.

The irradiation device 30 generates radiation used for treatment based on instructions from the irradiation control device 31 . Specifically, a desired dose distribution is formed on the target 61 by controlling the energy of the radiation, the irradiation position and the irradiation dose. Part of the irradiation device 30 is installed on a rotating gantry 40 and can rotate together with the rotating gantry 40 . The rotating gantry 40 is moved to a desired angle based on instructions from the gantry control device 41 . By changing the angle of the rotating gantry 40, it is possible to irradiate radiation from a desired angle.

The patient positioning system 11 calculates the position correction amount of the patient 60 with respect to the irradiation device 30 based on the CT image at the time of treatment planning (hereinafter referred to as treatment planning image) and the treatment day image acquired by the imaging device 20 . The operator 70 confirms the calculation result and determines the position correction amount. Based on the determined position correction amount, the installation position of the couch 50 is calculated and set in the couch control device 51 .

The re-planning system 12 generates a composite CT image for re-planning based on the treatment planning image and the treatment day image. Furthermore, target and normal tissue regions are identified on the composite CT image and their contour data are generated. Also, based on the composite CT image and contour data, radiation irradiation parameters are optimized to create a plan for the day. Furthermore, the dose distribution of the daily plan is obtained and displayed on the display device 102 of the workflow manager 10 . The operator 70 checks the screen displayed on the display device 102 to determine whether or not to use the plan for that day for treatment on that day.

The patient QA system 13 verifies the plan for the day, and the operator confirms and approves the verification results.

The workflow manager 10 is connected to the imaging controller 21, exposure controller 31, gantry controller 41, couch controller 51, patient positioning system 11, replanning system 12 and patient QA system 13 to monitor the progress of the treatment workflow. monitor and manage;

The workflow manager 10 includes an input device 101 for inputting various parameters, a display device 102, a memory (storage medium) 103, a database (storage medium) 104, and an arithmetic processing unit 105 ( a control device that is an arithmetic element) and a communication device 106 .

The workflow manager 10 is composed of a device capable of various types of information processing, for example, an information processing device such as a computer.

The arithmetic elements are, for example, CPUs (Central Processing Units), GPUs (Graphic Processing Units), FPGAs (Field-Programmable Gate Arrays), and the like. The storage medium includes, for example, a magnetic storage medium such as a HDD (Hard Disk Drive), a semiconductor storage medium such as a RAM (Random Access Memory), a ROM (Read Only Memory), and an SSD (Solid State Drive). A combination of an optical disk such as a DVD (Digital Versatile Disk) and an optical disk drive is also used as a storage medium. In addition, known storage media such as magnetic tape media are also used as storage media.

The storage medium stores programs such as firmware. When the workflow manager 10 starts operating (for example, when the power is turned on), a program such as firmware is read from this storage medium and executed to control the workflow manager 10 as a whole. In addition to the programs, the storage medium also stores data required for each process of the workflow manager 10 .

Alternatively, some of the components constituting the workflow manager 10 may be interconnected via a LAN (Local Area Network), or interconnected via a WAN (Wide Area Network) such as the Internet. may

Although illustration is omitted, various devices and systems constituting the radiotherapy system 1, such as the patient positioning system 11, are also configured by information processing devices such as computers.

FIG. 2 is a schematic diagram of software used in an example replanning system 12 . The replanning system 12 has a contour generation module 121, a planning image generation module 122, a target dose distribution generation module 123, and an irradiation parameter optimization module 124, as shown in FIG.

FIG. 3 is a flow chart at the time of re-planning. The replanning system 12 receives and holds pre-generated treatment plan data and treatment day images from the database 104 of the workflow manager 10 before replanning is performed. Here, the treatment plan data includes a treatment plan image, contour data at the time of treatment planning, irradiation parameters, and dose distribution data of the treatment plan.

First, as shown in FIG. 3, the contour generation module 121 identifies target and normal tissue regions based on the treatment date image newer than the treatment planning image at the time of treatment planning, and generates contour data for them (step S101). ). Also, contour data for creating a target dose distribution is created for the treatment plan image and the treatment day image (step S101).

Next, the planning image generation module 122 generates a composite CT image used for replanning based on the treatment planning image and the treatment date image (step S102). The process of step S102 corresponds to the first calculation for creating a new image based on the treatment plan image and the treatment date image.

Specifically, in step S102, a composite CT image is generated by deforming the treatment plan image based on the treatment date image by non-rigid registration (deformable image registration; hereinafter referred to as DIR). At that time, the contour data created in step S101 may be used. Here, non-rigid registration means generating a vector that moves the position of each pixel of the image to be deformed to the corresponding pixel position of the target image, and deforming the image to be deformed so as to match the target image. show.

Next, the target dose distribution creation module 123 creates a target dose distribution for the treatment date based on the contour data for target and target dose distribution creation and the dose distribution data of the treatment plan (step S103). The process of step S103 corresponds to a second calculation for creating a target dose distribution based on the image at the time of treatment planning, the dose distribution, and another image newer than the treatment planning image.

Specifically, in step S103, based on the contour data for creating the target dose distribution, the treatment plan image is deformed with respect to the treatment date image by DIR, and a deformation amount DVF (Deformation Vector Field) is calculated. Furthermore, the target dose distribution is calculated by transforming the dose distribution of the treatment plan based on this DVF. Here, the deformation calculation for calculating the target dose distribution in step S103 uses calculation conditions and algorithms different from the deformation calculation in step S102.

Next, the irradiation parameter optimization module 124 obtains irradiation parameters for achieving the target dose distribution by optimization calculation based on the composite CT image generated in step S102 and the contour data generated in step S103 (step S104). Furthermore, the target dose distribution in the case of irradiation with the irradiation parameters obtained by the optimization calculation is calculated and displayed as a screen on the display device 102 of the workflow manager 10 (step S104).

After that, the operator 70 confirms the target dose distribution displayed on the display device 102 of the workflow manager 10 and determines whether or not it is applicable to the treatment on that day (step S105). If it is determined that the method is not applicable in step S105, the optimization conditions are changed, and then step S104 is executed again. If applicable, re-planning is complete and the intraday plan is verified by patient QA.

FIG. 4 shows the data flow from step S101 to step S104. The present embodiment is characterized in that the creation of the target dose distribution and the creation of the composite CT image are performed by different deformation calculations (first calculation and second calculation). For comparison, FIG. 5 shows the data flow during replanning by a typical radiotherapy system.

Next, a method for creating contour data for creating a target dose distribution and a method for creating a target dose distribution will be described with reference to FIGS. 6 to 10. FIG.

FIG. 6 shows an example of a cross-sectional image of the treatment planning image in the body axis direction. A target 61A is displayed in the body outline 62. FIG.

FIG. 7 shows an example dose distribution for a treatment plan. A high dose region 63 is formed with a width outside the target 61A and a low dose region 64 is formed around it. By extending the high-dose region 63 to the outside of the target 61A, it is possible to prevent the dose applied to the target 61A from decreasing even if the position of the target 61A during treatment changes.

FIG. 8 shows an example of a cross-sectional image of the treatment planning image in the body axis direction. An enlarged contour 65A obtained by enlarging the target 61A is displayed as the contour data for creating the target dose distribution. An enlarged contour 65A is created by three-dimensionally and isotropically enlarging the target 61A according to a preset enlargement amount. Further, as shown in FIG. 8, a plurality of enlarged outlines 65A can be created by changing the amount of enlargement.

FIG. 9 shows an example of a cross-sectional image in the body axis direction of the treatment day image. A target 61B is displayed in the body outline 62. FIG. FIG. 9 simulates a situation in which the target 61B on the day of treatment is reduced and partially recessed compared to the target 61A at the time of treatment planning.

FIG. 10 shows an example of a cross-sectional image in the body axis direction of the treatment day image. A contour 65B obtained by enlarging the target 61B is displayed as contour data for creating a target dose distribution. A contour 65B is created by three-dimensionally and isotropically enlarging the target 61B according to a preset enlargement amount. Also, as shown in FIG. 10, a plurality of contours 65B can be created by changing the amount of enlargement. The number of contours 65B to be created and the amount of enlargement thereof are the same as those of the enlarged contours 65A.

When creating the target dose distribution in step S103, based on the contour data for creating the target and target dose distribution, the treatment plan image is deformed with respect to the treatment day image by DIR, and the deformation amount DVF is calculated. Specifically, the DVF is calculated by enlarging and transforming the target 61A to match the target 61B, the enlarged outline 65A1 to the enlarged outline 65B1, and the enlarged outline 65A2 to the enlarged outline 65B2. By modifying the dose distribution of the treatment plan based on this DVF, the target dose distribution for the treatment day is calculated.

FIG. 11 shows an example of a setting screen of the workflow manager 10. As shown in FIG. An operator 70 operates the workflow manager 10 to specify the number of magnified contours to be created and the spacing to magnify.

Next, the effects of this embodiment will be described.

For comparison, first, a conventional target dose distribution creation method will be described. In the conventional method, the DVF is calculated by transforming based on the treatment plan image, treatment day image, target and normal tissue contour data, and the dose distribution of the treatment plan is transformed by the DVF (see FIG. 5).

FIG. 12 shows an example of the result of creating a target dose distribution by a conventional method. If the target 61B on the day of treatment shrinks compared to the target 61A at the time of treatment planning, and there is a partial depression, there is a possibility that the high dose region 63 of the target dose distribution will approach the target 61B accordingly. be. In this case, the high-dose region 63 outside the target 61B is narrowed, and there is a possibility that robustness against misalignment and errors in the composite CT image will be reduced. Furthermore, there is a possibility that a target dose distribution that is difficult to achieve by optimizing irradiation parameters, such as a high dose region 63 with a depression or a dose distribution with a steep dose gradient, can be obtained. In this case, due to the influence of dose distribution that is difficult to achieve during optimization, the number of iterations of optimization may increase and the time required for replanning may increase.

FIG. 13 shows an example of the result of creating a target dose distribution by the method of this embodiment. In creating the target dose distribution according to this embodiment, the DVF is calculated by transforming based on the enlarged contour 65, and the dose distribution of the treatment plan is transformed by the DVF to obtain the target dose distribution for the treatment day. Therefore, by transforming the dose distribution into a dose distribution that maintains the spread of the high-dose region 63 outside the target 61, the proximity of the high-dose region 63 to the target 61B, depressions in the dose distribution, and steep dose gradients are reduced. As a result, a target dose distribution that is easy to achieve reduces the potential for increased optimization time and reduces the time required for re-planning during adaptive treatment. .

<Example 2>
A radiotherapy system according to a second embodiment of the present invention will be described.

The difference between the radiation therapy system of this embodiment and the radiation therapy system 1 of Embodiment 1 is the method of creating the enlarged contour 65 . In this embodiment, the enlarged contour 65 is created by the following two procedures (1) and (2).

(1) Enlarging the contour in the depth direction viewed from each irradiation direction of radiation by the water equivalent passage length. On the other hand, the direction seen from the lateral direction with respect to each irradiation direction of the radiation is enlarged by the actual distance. As a result, a partially enlarged contour is created for each irradiation direction.

(2) An enlarged contour is created by logical sum of partial enlarged contours for each irradiation direction.

Other configurations and operations are substantially the same as those of the radiotherapy system of the first embodiment, and details thereof are omitted.

Next, the effects of this embodiment will be described.

It is known that when there is a low density portion outside the target 61 in particle beam therapy such as the lung, the high dose region 63 near the target outside the treatment plan is not evenly spaced from the target 61 . Specifically, the range of the high dose region 63 changes according to the water equivalent path length seen from the irradiation direction.

In this embodiment, the enlarged contour 65 is created based on the water equivalent passage length viewed from the irradiation direction. Therefore, it becomes easy to approximate the shape of the enlarged outline 65A to the shape of the high dose region 63 of the treatment plan. This makes it easier to create a target dose distribution that maintains the spread of the high-dose region 63 outside the target 61. As a result, a target dose distribution that is easy to implement is obtained, and the optimization time may increase. can be lowered further.

<Example 3>
A radiotherapy system of Example 3 of the present invention will be described.

The difference between the radiotherapy system of this embodiment and the radiotherapy systems of other embodiments is the method of creating the enlarged contour 65 . In the radiotherapy system of this embodiment, filtering is applied to the created enlarged contour 65 in the radiotherapy system of the first or second embodiment to correct the enlarged contour 65 .

Specifically, an image filter such as a Gaussian filter is applied to the three-dimensional image obtained by replacing the inside and outside of the enlarged contour 65 with binary data. In the obtained three-dimensional image, an enlarged contour 65 is created by regarding voxels having a pixel value equal to or greater than a preset value as an internal area of the enlarged contour 65 .

Next, the effects of this embodiment will be described. In this example, an image filter is applied to create the enlarged contour 65 . Therefore, the depression of the enlarged outline 65 is reduced. As a result, a target dose distribution that is easy to implement can be obtained, and the possibility of increasing the optimization time can be further reduced.

<Example 4>
A radiotherapy system of Example 4 of the present invention will be described.

The difference between the radiotherapy system of this embodiment and the radiotherapy systems of other embodiments is the method of creating the target dose distribution. In the radiation therapy system of this embodiment, in the radiation therapy system of Embodiments 1 to 3, an image filter such as a Gaussian filter is applied to the created target dose distribution to correct the target dose distribution. , with a modified target dose distribution.

Next, the effects of this embodiment will be described. In this embodiment, an image filter is applied to create the target dose distribution. Therefore, depressions in the target dose distribution and steep dose gradients are reduced. As a result, a target dose distribution that is easy to implement is obtained, which further reduces the possibility of an increase in optimization time.

<Example 5>
A radiotherapy system according to Example 5 of the present invention will be described.

The difference between the radiotherapy system of this embodiment and the radiotherapy systems of other embodiments is the method of creating the target dose distribution. In the radiotherapy system of the present embodiment, the enlargement contour 65 is not used during deformation to create the target dose distribution, and a penalty term is added to the objective function for deformation calculation to reduce depressions and steep dose gradients in the target dose distribution. do. Specifically, a penalty term for the dose gradient after deformation and a penalty term for the depression of the dose distribution in the depth direction as seen from the irradiation direction are added.

Next, the effects of this embodiment will be described. In this embodiment, the target dose distribution is created by modified calculation in which a penalty term for reducing depressions and steep dose gradients in the target dose distribution is added to the objective function. Therefore, depressions in the target dose distribution and steep dose gradients are reduced. As a result, a target dose distribution that is easy to implement is obtained, which further reduces the possibility of an increase in optimization time.

<Others>
It should be noted that the present invention is not limited to the above examples, and includes various modifications. The above embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations.

Some or all of the above configurations, functions, processing units, processing means, and the like may be realized by hardware by designing integrated circuits, for example. Moreover, each of the above configurations, functions, etc. may be realized by software by a processor interpreting and executing a program for realizing each function. Information such as programs, tables, and files that implement each function can be stored in a recording device such as a memory, a hard disk, or an SSD, or a recording medium such as an IC card, an SD card, or a DVD.

Further, the control lines and information lines indicate those considered necessary for explanation, and not all control lines and information lines are necessarily indicated on the product. In practice, it may be considered that almost all configurations are interconnected.

1: Radiation Therapy System 10: Workflow Manager 11: Patient Positioning System 12: Replanning System 13: Patient QA System 20: Imager 21: Imaging Controller 30: Irradiation Device 31: Irradiation Controller 40: Rotating Gantry 41: Gantry Control Apparatus 50: Couch 51: Couch Control 60: Patient 61: Target 61A: Target on Treatment Planning Image 61B: Target on Treatment Day Image 62: Body Contour 63: High Dose Area 64: Low Dose Area 65A, 65A1, 65A2 : Enlarged contours 65B, 65B1, 65B2 of the target on the treatment plan image: Treatment day Contour 70 of the enlarged target on the image: Operator 101: Input device 102: Display device 103: Memory (storage medium)
104: Database (storage medium)
105: Arithmetic processing device 106: Communication device 121: Contour creation module 122: Planning image creation module 123: Target dose distribution creation module 124: Irradiation parameter optimization module

Claims (8)

A radiotherapy system that emits radiation,
performing a first calculation to create a new image based on the treatment planning image and another image newer than the treatment planning image;
performing a second calculation to create a targeted target dose distribution based on the treatment planning image, the dose distribution, and another image newer than the treatment planning image;
A radiotherapy system characterized by optimizing irradiation parameters with the target dose distribution as a target. In the radiotherapy system of claim 1,
A radiotherapy system, wherein the first calculation and the second calculation include non-rigid registration. In the radiotherapy system according to claim 2,
The radiotherapy system, wherein the second calculation includes non-rigid registration using target contour data of the treatment planning image and the different image and contour data created by enlarging the contour. In the radiotherapy system according to claim 3,
A radiotherapy system, wherein the contour data is created by enlarging the contour according to an equivalent water path length viewed from the irradiation direction of the radiation. In the radiotherapy system according to claim 3,
A radiotherapy system that applies an image filter to the contour data to create corrected contour data, and uses the corrected contour data. In the radiotherapy system according to claim 3,
A radiotherapy system characterized by creating and using a modified target dose distribution by applying an image filter to the target dose distribution. In the radiotherapy system according to claim 2,
In the second calculation, the non-rigid registration objective function includes a penalty term for the dose gradient after deformation and a penalty term for the depression of the dose distribution in the depth direction viewed from the radiation irradiation direction. radiation therapy system. In the radiotherapy system according to claim 2,
A radiotherapy system, wherein different calculation conditions or algorithms are used for the non-rigid registration of the first calculation and the non-rigid registration of the second calculation.

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