Static intensity modulated method and system for x-ray super high dose rate radiotherapy

Abstract

The application provides a static intensity modulation method suitable for X-ray super high dose rate radiotherapy, and relates to the technical field of X-ray radiotherapy, and the method comprises the following steps: measuring the attenuation curve of the static intensity modulator material at different positions from the beam flow center axis on the plane where the static intensity modulator is located to the initial beam flow of an accelerator through a dose distribution experiment; calculating the required material thickness of each position based on the initial beam flow dose distribution, the predetermined dose distribution and the attenuation curve, so as to obtain the thickness distribution of the static intensity modulator; and performing the static intensity modulation of the X-ray super high dose rate radiotherapy through the static intensity modulator with the thickness distribution. The static intensity modulation of the X-ray super high dose rate radiotherapy is realized by adopting the above scheme.

Description

Technical Field

[0001] This application relates to the field of X-ray radiotherapy technology, and in particular to a static intensity-modulated radiotherapy method and system suitable for ultra-high dose rate X-ray radiotherapy. Background Technology

[0002] The FLASH effect was discovered by irradiating experimental animals with ultra-high dose rate radiation. Current technologies utilizing the FLASH effect in radiotherapy are called FLASH radiotherapy or ultra-high dose rate radiotherapy. The most significant characteristic of FLASH radiotherapy is that it uses ultra-high dose radiation (generally considered >40 Gy / s) to generate the FLASH effect, achieving the goal of protecting normal tissues without affecting tumor killing. FLASH radiotherapy was initially achieved using electron beams, and later using protons, carbon ions, and other methods.

[0003] Traditional X-ray radiotherapy often utilizes intensity-modulated radiotherapy (IMRT) to achieve better coverage of the tumor target area and protection of normal tissues. IMRT is generally achieved through the movement of a multi-leaf collimator on the accelerator head. However, FLASH radiotherapy has an extremely high dose rate and a very short irradiation time, making it difficult to achieve IMRT through the mechanical movement of a multi-leaf collimator. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in the related art.

[0005] Therefore, the first objective of this application is to propose a static intensity modulation method suitable for X-ray ultra-high dose rate radiotherapy, thereby realizing static intensity modulation of X-ray FLASH radiotherapy.

[0006] The second objective of this application is to provide a static intensity-modulated radiotherapy system suitable for ultra-high dose rate X-ray radiotherapy.

[0007] To achieve the above objectives, the first aspect of this application proposes a static intensity-modulated radiotherapy method suitable for ultra-high dose rate X-ray radiotherapy, comprising:

[0008] The attenuation curves of the static intensity modulated beam material at different distances from the beam center axis on the plane where the static intensity modulated beam is located were measured through dose distribution experiments.

[0009] The required material thickness at each location is calculated based on the initial beam dose distribution, the predetermined dose distribution, and the attenuation curve, thus obtaining the thickness distribution of the static intensity modulated transformer.

[0010] Static intensity modulation of X-ray ultra-high dose rate radiotherapy using a static intensity modulator with a defined thickness distribution.

[0011] Optionally, in one embodiment of this application, a dose distribution experiment is performed, including:

[0012] Step 201: set the static intensity modulator material with thickness t at the position where the static intensity modulator is placed, open a pair of center leaves of the multi-leaf collimator with a predetermined width to form a slit, and close the other leaves;

[0013] Step 202: set the distance from the X-ray focal point to the slit formed by the center pair of leaves on the plane where the static intensity modulator is located as r, measure the dose distribution of a line opposite to the slit leaf using a detector, and take the maximum value of the dose as the dose value D(r, t) at position r;

[0014] Step 203: repeat step 202, and adjust r and / or t at each repetition to obtain the r-D(r, t) curve at different positions r and different thicknesses t, and obtain the attenuation curve A(t, r) of the initial beam of the accelerator at different positions from the beam center axis x.

[0015] Optionally, in an embodiment of the present application, the attenuation curve is obtained by:

[0016] setting the attenuation coefficient of the position with the highest dose rate as 1, and calculating the attenuation coefficient according to the difference between the predetermined dose and the initial beam dose at each position.

[0017] Optionally, in an embodiment of the present application, the thickness of the material required at position r is calculated by:

[0018] obtaining the thickness t of the material required to achieve the corresponding attenuation coefficient from the attenuation curve A(r, t) at position r according to the difference between the initial beam dose distribution and the predetermined dose distribution.

[0019] To achieve the above purpose, a second aspect of the present application provides a static intensity modulation system suitable for X-ray super high dose rate radiotherapy, comprising:

[0020] an attenuation curve acquisition module, configured to measure the attenuation curve of the static intensity modulator material at different positions from the beam center axis on the plane where the static intensity modulator is located by dose distribution experiment;

[0021] a static intensity modulator design module, configured to calculate the thickness of the material required at each position based on the initial beam dose distribution, the predetermined dose distribution, and the attenuation curve, and obtain the thickness distribution of the static intensity modulator;

[0022] a static intensity module, configured to perform static intensity modulation for X-ray super high dose rate radiotherapy by the static intensity modulator with the thickness distribution.

[0023] Optionally, in an embodiment of the present application, the dose distribution experiment is performed by:

[0024] Step 201: set a static intensity modulator material with thickness t at the position where the static intensity modulator is placed, open a pair of center leaves of a multi-leaf collimator with a predetermined width to form a slit, and close other leaves;

[0025] Step 202: set the distance from the X-ray focal point to the slit formed by the center pair of leaves on the plane where the static intensity modulator is located as r, measure the dose distribution of a line opposite to the slit leaf using a detector, and take the maximum value of the dose as the dose value D(r, t) at position r;

[0026] Step 203: repeat step 202, and adjust r and / or t at each repetition to obtain r-D(r, t) curves at different positions r and different thicknesses t, and obtain the attenuation curve A(t, r) of the initial beam of the accelerator at different positions from the beam center axis x.

[0027] Optionally, in an embodiment of the present application, the attenuation curve is obtained, comprising:

[0028] Set the attenuation coefficient of the position with the highest dose rate as 1, and calculate the attenuation coefficient according to the difference between the predetermined dose and the initial beam dose at each position.

[0029] Optionally, in an embodiment of the present application, the thickness of the material required at position r is calculated, comprising:

[0030] According to the difference between the initial beam dose distribution and the predetermined dose distribution, the thickness t of the material required to achieve the corresponding attenuation coefficient is obtained from the attenuation curve A(r, t) at position r.

[0031] The static intensity modulation method and system suitable for X-ray ultra-high dose rate radiotherapy in the embodiments of the present application adjust the beam intensity in the irradiation field through the material with a certain thickness distribution, and realize the static intensity modulation of X-ray FLASH radiotherapy.

[0032] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter in the description of embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0033] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description of embodiments of the present application, taken in conjunction with the accompanying drawings, in which:

[0034] Figure 1 A flowchart of a static intensity modulation method suitable for X-ray ultra-high dose rate radiotherapy provided in Embodiment One of the present application;

[0035] Figure 2 A flowchart of an attenuation curve measurement process of an embodiment of the present application;

[0036] Figure 3 A flowchart of a process of X-ray FLASH radiotherapy using a static intensity modulator according to an embodiment of the present application;

[0037] Figure 4 A structural diagram of a static intensity modulating system suitable for X-ray ultra-high dose rate radiotherapy according to an embodiment of the present application. DETAILED DESCRIPTION

[0038] Embodiments of the present application are described in detail below with reference to the accompanying drawings, in which the same or similar components have the same or similar designations and functions throughout various figures and / or portions of the drawings. Embodiments described below are examples in which specific language is used to describe the embodiments in order to aid the Understanding of the application and are not intended to limit the application otherwise. Unless otherwise specified, terms of approximation such as "about" and "substantially" include all values of plus or minus ten percent (10%) of the stated value.

[0039] A static intensity modulating method and system suitable for X-ray ultra-high dose rate radiotherapy according to an embodiment of the present application are described below with reference to the accompanying drawings.

[0040] Figure 1 A flowchart of a static intensity modulating method suitable for X-ray ultra-high dose rate radiotherapy according to an embodiment of the present application.

[0041] As shown in Figure 1 , the static intensity modulating method suitable for X-ray ultra-high dose rate radiotherapy includes the following steps:

[0042] Step 101: Measure the attenuation curve of the static intensity modulator material at different positions from the beam center axis on the plane where the static intensity modulator is located with respect to the initial beam of the accelerator through a dose distribution experiment.

[0043] Specifically, the present embodiment is suitable for static intensity modulation of a conventional dose rate or ultra-high dose rate accelerator, which refers to a device that accelerates electrons using electromagnetic fields, and the electrons hit a target to generate X-rays, including but not limited to a normal-temperature linear accelerator, a superconducting linear accelerator, a petal-type accelerator, etc.

[0044] In the present embodiment, the initial beam is the X-ray beam output by the accelerator, which can be smoothed or not smoothed.

[0045] The dose distribution of the initial beam is measured by using a probe that can measure ionizing radiation dose (including but not limited to a gas ionization chamber, a semiconductor probe, a scintillation probe) on a predetermined plane.

[0046] In the present embodiment, the attenuation curve is measured, and a schematic diagram is shown in Figure 2 :

[0047] 1) Put a material plate with thickness t on the position where the static intensity modulator is placed, close all the leaves of the multi-leaf collimator except the central pair of leaves, open the central pair of leaves to form a slit with a certain width.

[0048] 2) Put the slit at a distance r from the beam central axis, which is the distance from the X-ray focal point to the central axis when projected onto the static intensity modulator plane, and then use the detector to measure the dose distribution of a line directly below the slit leaf, and take the maximum dose as the dose value D(r, t) of the slit position.

[0049] 3) Then change the distance r of the slit from the beam central axis, repeat the measurement method of 2) to obtain the r-D(r, t) curve of a certain thickness t

[0050] 4) Change the thickness of the material t, repeat the measurement of 2) and 3) to obtain the r-D(r, t) curve under different thicknesses, and obtain the attenuation curve at a certain r.

[0051] Step 102, calculate the required material thickness at each position based on the initial beam dose distribution, the predetermined dose distribution and the attenuation curve, and obtain the thickness distribution of the static intensity modulator;

[0052] In this embodiment, the design of the static intensity modulator includes: calculating the material thickness at different positions of the static intensity modulator according to the difference between the predetermined dose distribution and the initial beam dose distribution, thereby completing the design. The design needs to measure the attenuation curve A(t, r) of the static intensity modulator material at different positions from the beam central axis in the plane where the static intensity modulator is located (i.e. the relationship curve between dose attenuation and thickness t at r position, hereinafter referred to as attenuation curve). When designing, the attenuation coefficient of the position with the highest predetermined dose rate is set to 1, and the attenuation coefficient is calculated according to the difference between the predetermined dose and the initial beam dose at each position. At this time, the distance r from the focal point of the static intensity modulator plane to the beam central axis is calculated using the connecting line between the position and the X-ray focal point, and then the material thickness t required to achieve the attenuation coefficient is calculated from the attenuation curve A(r, t) at r position using iterative algorithm or interpolation algorithm, thereby designing the thickness distribution of the static intensity modulator.

[0053] In this embodiment, the manufacturing process of the static intensity modulator includes: different shapes of static intensity modulators are needed when irradiating different patients, which can be manufactured using cutting processing, 3D printing, etc., or a material sheet with a certain thickness and size is manufactured in advance and assembled into a static intensity modulator.

[0054] Step 103, static intensity modulation of X-ray super high dose rate radiotherapy by the static intensity modulator with the determined thickness distribution.

[0055] In the embodiment, the procedure of the static intensity modulator for radiotherapy includes: measuring the initial beam dose distribution when the accelerator is calibrated, measuring the attenuation curve, adjusting the shape of the multi-leaf collimator according to the maximum outer contour of the irradiation field of the predetermined treatment plan, then installing and adjusting the static intensity modulator, then measuring the intensity-modulated dose distribution, and finally treating the patient. The overall flowchart is shown in Figure 3 .

[0056] The static intensity modulation method for X-ray ultra-high dose rate radiotherapy in the embodiment adjusts the beam intensity in the irradiation field by using the material with a certain thickness distribution, so as to realize the static intensity modulation of X-ray FLASH radiotherapy.

[0057] In order to realize the above-mentioned embodiment, the application further provides a static intensity modulation system suitable for X-ray ultra-high dose rate radiotherapy.

[0058] Figure 4 A structural schematic diagram of the static intensity modulation system suitable for X-ray ultra-high dose rate radiotherapy provided in the embodiment is shown in the figure.

[0059] As shown in the figure, the static intensity modulation system suitable for X-ray ultra-high dose rate radiotherapy includes: Figure 4

[0060] The attenuation curve acquisition module is configured to measure the attenuation curve of the static intensity modulator material at different positions from the beam center axis on the plane where the static intensity modulator is located with respect to the initial beam of the accelerator through the dose distribution experiment;

[0061] The static intensity modulator design module is configured to calculate the required material thickness of each position based on the initial beam dose distribution, the predetermined dose distribution and the attenuation curve, and obtain the thickness distribution of the static intensity modulator;

[0062] The static intensity modulation module is configured to perform the static intensity modulation of the X-ray ultra-high dose rate radiotherapy by the static intensity modulator with the thickness distribution.

[0063] Optionally, in one embodiment of the application, the dose distribution experiment includes:

[0064] Step 201: The static intensity modulator material with a thickness of t is placed at the position where the static intensity modulator is placed, and a pair of center leaves of the multi-leaf collimator is opened to a predetermined width to form a gap, and the other leaves are closed;

[0065] Step 202: The distance from the gap formed by the center pair of leaves on the plane where the static intensity modulator is located to the beam center axis x is set to r, the dose distribution of the line opposite to the gap leaf is measured by using the detector, and the maximum value of the dose is taken as the dose value D(r, t) at the position r;

[0066] ​Step 203: repeat step 202, and at each repetition, adjust r and / or t, to obtain the r-D(r, t) curve at different positions r and different thicknesses t, and obtain the attenuation curve A(t, r) of the initial beam of the accelerator at different positions x from the beam flow center axis.

[0067] Optionally, in an embodiment of the present application, obtaining the attenuation curve comprises:

[0068] Setting the attenuation coefficient of the position with the highest dose rate as 1, and calculating the attenuation coefficient according to the difference between the predetermined dose of each position and the initial beam dose.

[0069] Optionally, in an embodiment of the present application, calculating the required thickness of the material at position r comprises:

[0070] According to the difference between the initial beam dose distribution and the predetermined dose distribution, obtaining the required thickness t of the material to achieve the corresponding attenuation coefficient from the attenuation curve A(r, t) of the position r.

[0071] It should be noted that the foregoing description of the embodiment of the static intensity modulation method applicable to X-ray ultra-high dose rate radiotherapy is also applicable to the embodiment of the static intensity modulation system applicable to X-ray ultra-high dose rate radiotherapy, which will not be described here.

[0072] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0073] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0074] Any processes or methods described in the flowcharts or otherwise described herein can be understood as representing modules, segments, or portions of code that include one or more executable instructions for implementing specific logical functions or steps in the processes. The scope of preferred embodiments of the present application encompasses other implementations in which the steps are performed in a different order, including substantially simultaneously, or in reverse order, according to the functions involved, as will be understood by those skilled in the art of the embodiments described herein.

[0075] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a list of executable instructions for implementing the logic function, and can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor- containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For purposes of this specification, a "computer-readable medium" can be any apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable medium can be a more specific example (non-exhaustive list) including the following: an electronic connection having one or more wires (electronic apparatus), a portable computer diskette (magnetic apparatus), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium can even be paper or other suitable medium on which the program can be printed, as the program can be electronically obtained, for example, by optically scanning the paper or other medium, then

[0076] It should be understood that portions of the present application can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. As in another embodiment, if implemented in hardware, any of the following technologies known in the art or their combinations can be used: discrete logic circuitry having logic gates for implementing logic functions on data signals, application specific integrated circuits having appropriate combinational logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA), etc.

[0077] Those skilled in the art of the present technology can understand that all or part of the steps carried out by the above-mentioned embodiment method can be completed by programs instructing related hardware, and the programs can be stored in a computer readable storage medium. When the program is executed, it includes one of the steps of the method embodiment or a combination thereof.

[0078] In addition, each functional unit in each embodiment of the present application can be integrated into one processing module, or each unit can exist physically alone, or two or more units can be integrated into one module. The integrated module can be realized in the form of hardware or in the form of a software functional module. When the integrated module is realized in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer readable storage medium.

[0079] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-mentioned embodiments within the scope of the present application.

Claims

1. A static intensity-modulated radiotherapy method suitable for ultra-high dose rate X-ray radiotherapy, characterized in that, include: The attenuation curves of the static intensity modulated beam material at different distances from the beam center axis on the plane where the static intensity modulated beam is located were measured through dose distribution experiments. The required material thickness at each location is calculated based on the initial beam dose distribution, the predetermined dose distribution, and the attenuation curve, thus obtaining the thickness distribution of the static intensity modulated transformer. Static intensity modulation of X-ray ultra-high dose rate radiotherapy using a static intensity modulator with a defined thickness distribution; The dose distribution experiment includes: Step 201: Place a static intensity modulator material with a thickness of t at the location where the static intensity modulator is placed. The central pair of blades of the multi-leaf collimator open to a predetermined width to form a gap, while the other blades close. Step 202: Set the distance from the gap formed by the central pair of blades when the X-ray focus is projected onto the plane where the static intensity modulator is located to the beam central axis x as r. Use the detector to measure the dose distribution on the line directly opposite the blade with the gap, and take the maximum dose value as the dose value D(r,t) at position r. Step 203: Repeat step 202. In each repetition, adjust r and / or t to obtain the rD(r,t) curves at different positions r and different thicknesses t, and obtain the attenuation curves A(t,r) of the initial beam of the accelerator at different positions from the beam center axis x. Obtain the attenuation curve, including: The attenuation coefficient at the position with the highest dose rate is set to 1. The attenuation coefficient is calculated based on the difference between the predetermined dose and the initial beam dose at each position. Calculate the required material thickness at position r, including: From the attenuation curve A(r,t) at position r, the material thickness t required to achieve the corresponding attenuation coefficient is obtained based on the difference between the initial beam dose distribution and the predetermined dose distribution.

2. A static intensity-modulated radiotherapy system suitable for ultra-high dose rate X-ray radiotherapy, characterized in that, include: The attenuation curve acquisition module is used to measure the attenuation curve of the static intensity modulator material at different positions on the plane of the static intensity modulator and at different distances from the beam center axis for the initial beam of the accelerator through dose distribution experiments. The static intensity modulated beam design module is used to calculate the required material thickness at each location based on the initial beam dose distribution, the predetermined dose distribution, and the attenuation curve, thereby obtaining the thickness distribution of the static intensity modulated beam. The static intensity modulation module is used for static intensity modulation of X-ray ultra-high dose rate radiotherapy by using a static intensity modulator with a defined thickness distribution. The dose distribution experiment includes: Step 201: Place a static intensity modulator material with a thickness of t at the location where the static intensity modulator is placed. The central pair of blades of the multi-leaf collimator open to a predetermined width to form a gap, while the other blades close. Step 202: Set the distance from the gap formed by the central pair of blades when the X-ray focus is projected onto the plane where the static intensity modulator is located to the beam central axis x as r. Use the detector to measure the dose distribution on the line directly opposite the blade with the gap, and take the maximum dose value as the dose value D(r,t) at position r. Step 203: Repeat step 202. In each repetition, adjust r and / or t to obtain the rD(r,t) curves at different positions r and different thicknesses t, and obtain the attenuation curves A(t,r) of the initial beam of the accelerator at different positions from the beam center axis x. Obtain the attenuation curve, including: The attenuation coefficient at the position with the highest dose rate is set to 1. The attenuation coefficient is calculated based on the difference between the predetermined dose and the initial beam dose at each position. Calculate the required material thickness at position r, including: From the attenuation curve A(r,t) at position r, the material thickness t required to achieve the corresponding attenuation coefficient is obtained based on the difference between the initial beam dose distribution and the predetermined dose distribution.

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