Static intensity modulation method and system suitable for X-ray ultrahigh dose rate radiotherapy

Abstract

The invention provides a static intensity modulation method suitable for X-ray ultrahigh-dose-rate radiotherapy, and relates to the technical field of X-ray radiotherapy, and the method comprises the steps: measuring an attenuation curve of a static intensity modulator material on a plane where a static intensity modulator is located and at different positions away from a beam current central axis with respect to an accelerator initial beam current through a dose distribution experiment; calculating the material thickness required by each position based on the initial beam dose distribution, the predetermined dose distribution and the attenuation curve to obtain the thickness distribution of the static intensity modulator; and static intensity modulation of the X-ray ultrahigh dose rate radiotherapy is carried out through the static intensity modulator with determined thickness distribution. By the adoption of the scheme, static intensity modulation of X-ray ultrahigh-dose-rate radiotherapy is achieved.

Description

Technical Field

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

[0002] The FLASH effect was discovered by irradiating experimental animals with ultra-high dose rate rays. In the prior art, radiotherapy using the FLASH effect is called FLASH radiotherapy or ultra-high dose rate radiotherapy. The biggest feature of FLASH radiotherapy is to use the FLASH effect generated by ultra-high dose rays (generally considered > 40 Gy / s) to protect normal tissues without affecting tumor killing. FLASH radiotherapy was first achieved using electron beams, and then using protons, carbon ions, etc.

[0003] Traditional X-ray radiotherapy often uses intensity modulation technology (IMRT) to better cover the tumor target area and protect normal tissues. Intensity modulation is generally achieved by the movement of a multi-leaf collimator on the accelerator head. However, the dose rate of FLASH radiotherapy is extremely high and the irradiation time is extremely short, making it difficult to achieve intensity modulation through the mechanical movement of the multi-leaf collimator. Summary of the Invention

[0004] This application aims to solve at least one of the technical problems in the related art to some extent.

[0005] To this end, the first object of this application is to propose a static intensity modulation method applicable to X-ray ultra-high dose rate radiotherapy, which realizes the static intensity modulation of X-ray FLASH radiotherapy.

[0006] The second object of this application is to propose a static intensity modulation system applicable to X-ray ultra-high dose rate radiotherapy.

[0007] To achieve the above object, the first aspect embodiment of this application proposes a static intensity modulation method applicable to X-ray ultra-high dose rate radiotherapy, including:

[0008] Through a dose distribution experiment, measure the attenuation curve of the static intensity modulator material for the initial beam of the accelerator at different positions on the plane where the static intensity modulator is located and at different distances from the beam central axis;

[0009] Based on the initial beam dose distribution, the predetermined dose distribution, and the attenuation curve, calculate the material thickness required for each position to obtain the thickness distribution of the static intensity modulator;

[0010] Perform static intensity modulation of X-ray ultra-high dose rate radiotherapy through the static intensity modulator with the determined thickness distribution.

[0011] Optionally, in an embodiment of this application, performing a dose distribution experiment includes:

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

[0013] Step 202: Set the distance from the slit formed by the pair of central leaves when projected onto the plane where the static intensity modulator is located from the X-ray focus to the beam central axis x as r. Use a detector to measure the dose distribution of the line next to the leaves facing the slit, and take the maximum value of the dose as the dose value D(r, t) at the position r.

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

[0015] Optionally, in an embodiment of the present application, obtaining the attenuation curve includes:

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

[0017] Optionally, in an embodiment of the present application, calculating the material thickness required for the position r includes:

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

[0019] To achieve the above object, an embodiment of the second aspect of the present invention proposes a static intensity modulation system applicable to X-ray ultra-high dose rate radiotherapy, including:

[0020] An attenuation curve acquisition module for measuring the attenuation curve of the static intensity modulator material for the initial beam of the accelerator at different positions from the beam central axis on the plane where the static intensity modulator is located through a dose distribution experiment;

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

[0022] A static intensity modulation module for performing static intensity modulation of X-ray ultra-high dose rate radiotherapy through the static intensity modulator with a determined thickness distribution.

[0023] Optionally, in an embodiment of the present application, performing a dose distribution experiment includes:

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

[0025] Step 202: Set the distance from the slit formed by the pair of central leaves to the beam central axis x when projected onto the plane where the static intensity modulator is located from the X-ray focus. Use a detector to measure the dose distribution of the line immediately below the leaves facing the slit, and take the maximum value of the dose as the dose value D(r,t) at the position r.

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

[0027] Optionally, in an embodiment of the present application, obtaining the attenuation curve includes:

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

[0029] Optionally, in an embodiment of the present application, calculating the material thickness required for the position r includes:

[0030] From the attenuation curve A(r,t) at the position r, obtain the material thickness t required to achieve the corresponding attenuation coefficient according to the difference between the initial beam dose distribution and the predetermined dose distribution.

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

[0032] Additional aspects and advantages of the present application will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present application. Description of the Drawings

[0033] The above-mentioned and / or additional aspects and advantages of the present application will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0034] Figure 1 It is a schematic flowchart of a static intensity modulation method applicable to X-ray ultra-high dose rate radiotherapy provided by Embodiment 1 of the present application;

[0035] Figure 2 It is a schematic flowchart of the attenuation curve measurement in the embodiment of the present application;

[0036] Figure 3 Schematic flow chart of using a static intensity modulator for X-ray FLASH radiotherapy according to an embodiment of the present application;

[0037] Figure 4 Schematic structural diagram of a static intensity modulation system applicable to X-ray ultra-high dose rate radiotherapy provided by an embodiment of the present application. Specific embodiments

[0038] The embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application.

[0039] The static intensity modulation method and system applicable to X-ray ultra-high dose rate radiotherapy according to an embodiment of the present application will be described below with reference to the accompanying drawings.

[0040] Figure 1 Schematic flow chart of a static intensity modulation method applicable to X-ray ultra-high dose rate radiotherapy provided by Embodiment 1 of the present application.

[0041] As Figure 1 shown, the static intensity modulation method applicable to X-ray ultra-high dose rate radiotherapy includes the following steps:

[0042] Step 101, through a dose distribution experiment, measure the attenuation curve of the static intensity modulator material for the initial beam of the accelerator at different positions on the plane where the static intensity modulator is located and at different distances from the beam central axis;

[0043] Specifically, this embodiment is applicable to static intensity modulation of conventional dose rate or ultra-high dose rate accelerators. An accelerator refers to a device that accelerates electrons using electromagnetic fields and electrons bombard a target to generate X-rays, including but not limited to a normal temperature linear accelerator, a superconducting linear accelerator, a petal-shaped accelerator, etc.

[0044] In this embodiment, the initial beam is the X-ray beam output by the accelerator, which can be flattened or unflattened.

[0045] The measurement method of the dose distribution of the initial beam is: use a detector that can realize the measurement of ionization radiation dose (including but not limited to a gas ionization chamber, a semiconductor detector, a scintillation detector) to measure the dose distribution on a predetermined plane.

[0046] In this embodiment, for the measurement of the attenuation curve, see the schematic diagram in Figure 2 :

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

[0048] 2) Place the slit at a distance x from the beam central axis. When projected from the X-ray focus onto the plane of the static intensity modulator, the distance from the central axis is r. Then use a detector to measure the dose distribution of the line directly below the slit-opening leaves, and take the maximum value of the dose as the dose value D(r,t) at the position of this slit.

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

[0050] 4) Change the thickness t of the material, repeat the measurements in 2) and 3), obtain the r-D(r,t) curves at different thicknesses, and then the attenuation curve at a specific r can be obtained.

[0051] Step 102: Calculate the material thickness required at each position based on the initial beam dose distribution, the predetermined dose distribution, and the attenuation curve, to 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, so as to complete the design. The design requires measuring the attenuation curve A(t,r) of the static intensity modulator material for the initial beam of the accelerator at different positions from the beam central axis on the plane where the static intensity modulator is located (that is, the relationship curve between dose attenuation and thickness t at the r position, hereinafter referred to as the attenuation curve). When designing, the attenuation coefficient at the position with the highest predetermined dose rate is set to 1. According to the difference between the predetermined dose and the initial beam dose at each position, calculate the attenuation coefficient. At this time, calculate the distance r from the focus of the line connecting this position and the X-ray focus to the beam central axis on the plane of the static intensity modulator, and then use iterative algorithms or interpolation algorithms, etc., to calculate the material thickness t required to achieve this attenuation coefficient from the attenuation curve A(r,t) at the r position, so as to design the thickness distribution of the static intensity modulator.

[0053] In this embodiment, the manufacturing process of the static intensity modulator includes: when irradiating different patients, static intensity modulators with different shapes are required, and methods such as machining and 3D printing can be used for manufacturing, or material sheets with a certain thickness and size can be pre-manufactured and assembled into a static intensity modulator.

[0054] Step 103: Perform static intensity modulation for X-ray ultra-high dose rate radiotherapy through the static intensity modulator with a determined thickness distribution.

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

[0056] The static intensity modulation method applicable to X-ray ultra-high dose rate radiotherapy in the embodiments of the present application adjusts the beam intensity within the irradiation field through a material with a certain thickness distribution, so as to achieve static intensity modulation for X-ray FLASH radiotherapy.

[0057] To implement the above embodiment, the present application also proposes a static intensity modulation system applicable to X-ray ultra-high dose rate radiotherapy.

[0058] Figure 4 It is a schematic structural diagram of a static intensity modulation system applicable to X-ray ultra-high dose rate radiotherapy provided by the embodiments of the present application.

[0059] As Figure 4 shown, the static intensity modulation system applicable to X-ray ultra-high dose rate radiotherapy includes:

[0060] An attenuation curve acquisition module, configured to measure the attenuation curve of the static intensity modulator material for the initial beam of the accelerator at different positions from the beam central axis on the plane where the static intensity modulator is located through a dose distribution experiment;

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

[0062] A static intensity modulation module, configured to perform static intensity modulation for X-ray ultra-high dose rate radiotherapy through the static intensity modulator with a determined thickness distribution.

[0063] Optionally, in an embodiment of the present application, performing a dose distribution experiment includes:

[0064] Step 201: Place a static intensity modulator material with a thickness of t at the position where the static intensity modulator is placed, open a pair of central blades of the multi-leaf collimator by a predetermined width to form a slit, and close the other blades;

[0065] Step 202: Set the distance from the slit formed by the pair of central blades projected onto the plane where the static intensity modulator is located from the X-ray focus to the beam central axis x as r, use a detector to measure the dose distribution of the line directly below the slit blades, and take the maximum value of the dose as the dose value D(r, t) at the position r;

[0066] Step 203: Repeat Step 202. At each repetition, adjust r and / or t to obtain the 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 x from the central axis of the beam.

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

[0068] Set the attenuation coefficient at the position with the highest dose rate to 1, and calculate the attenuation coefficient according to the difference between the predetermined dose at each position and the initial beam dose.

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

[0070] From the attenuation curve A(r,t) at position r, obtain the material thickness t required to achieve the corresponding attenuation coefficient according to the difference between the initial beam dose distribution and the predetermined dose distribution.

[0071] It should be noted that the foregoing explanation of the embodiments of the static intensity modulation method applicable to X-ray ultra-high dose rate radiotherapy also applies to the static intensity modulation system applicable to X-ray ultra-high dose rate radiotherapy in this embodiment, and will not be repeated here.

[0072] In the description of this specification, the description with reference to terms such as "an embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0073] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0074] Any process or method description represented in a flowchart or otherwise described herein can be understood to represent a module, segment, or portion of code including one or more executable instructions for implementing a customized logical function or process. The scope of the preferred embodiments of the present application includes additional implementations, where functions may be executed in a substantially simultaneous manner or in a reverse order according to the involved functions, rather than in the order shown or discussed. This should be understood by those skilled in the art to which the embodiments of the present application pertain.

[0075] The logic and / or steps represented in a flowchart or otherwise described herein, for example, can be considered a sequenced list of executable instructions for implementing a logical function, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or in conjunction with such instruction execution systems, apparatus, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device. More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or other suitable processing as necessary, and then stored in a computer memory.

[0076] It should be understood that various parts of the present application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application-specific integrated circuits having suitable combinational logic gate circuits, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0077] Those of ordinary skill in the art can understand that all or part of the steps carried out in the method of the above embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.

[0078] In addition, in each of the embodiments of the present application, each functional unit can be integrated into a processing module, can exist separately physically for each unit, or two or more units can be integrated into one module. The above integrated module can be implemented in the form of hardware or in the form of a software functional module. When the above integrated module is implemented 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 above-mentioned storage medium can be a read-only memory, a magnetic disk or an optical disc, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A static intensity modulation method suitable for X-ray ultra-high dose rate radiotherapy, characterized in that: include: Through the dose distribution experiment, the attenuation curve of the initial beam of the accelerator is measured when the static intensity modulator material is at different positions away from the beam center axis on the plane where the static intensity modulator is located; Calculate the material thickness required at each position based on the initial beam dose distribution, the predetermined dose distribution and the attenuation curve to obtain the thickness distribution of the static intensity modulator; Static intensity modulation of X-ray ultra-high dose rate radiotherapy is performed by a static intensity modulator that determines the thickness distribution.

2. The method according to claim 1, characterized in that The dose distribution experiment is performed, including: Step 201: a static intensity modulator material with a thickness of t is placed at a location where the static intensity modulator is placed, a pair of leaves at the center of the multi-leaf collimator are opened to a predetermined width to form a gap, and the other leaves are closed; Step 202: Set the distance from the gap formed by the central pair of blades when projecting the X-ray focus onto the plane where the static intensity modulator is located to the beam center axis x as r, use the detector to measure the dose distribution of a line under the blades facing the gap, and take the maximum dose value as the dose value D(r,t) at position r; Step 203: Repeat step 202. During each repetition, adjust r and / or t to obtain the rD(r, t) curve at different positions r and different thicknesses t, and obtain the attenuation curve A(t, r) for the initial beam of the accelerator at different positions from the beam center axis x.

3. The method according to claim 2, characterized in that Get the decay curve, including: The attenuation coefficient at the position with the highest dose rate is set to 1, and the attenuation coefficient is calculated based on the difference between the predetermined dose and the initial beam dose at each position.

4. The method according to claim 3, characterized in that 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 according to the difference between the initial beam dose distribution and the predetermined dose distribution.

5. A static intensity modulation system suitable for X-ray ultra-high dose rate radiotherapy, characterized in that: include: The attenuation curve acquisition module is used to measure the attenuation curve of the initial beam of the accelerator at different positions of the static intensity modulator material on the plane where the static intensity modulator is located and at different distances from the central axis of the beam through a dose distribution experiment; A static intensity modulator design module is used to calculate the material thickness required at each position based on the initial beam dose distribution, the predetermined dose distribution and the attenuation curve to obtain the thickness distribution of the static intensity modulator; The static intensity modulation module is used to perform static intensity modulation of X-ray ultra-high dose rate radiotherapy by determining the static intensity modulator of the thickness distribution.

6. The system according to claim 5, characterized in that The dose distribution experiment is performed, including: Step 201: a static intensity modulator material with a thickness of t is placed at a position where the static intensity modulator is placed, a pair of leaves at the center of the multi-leaf collimator are opened to a predetermined width to form a gap, and the other leaves are closed; Step 202: Set the distance from the gap formed by the central pair of blades when projecting the X-ray focus onto the plane where the static intensity modulator is located to the beam center axis x as r, use the detector to measure the dose distribution of a line under the blades facing the gap, and take the maximum dose value as the dose value D(r,t) at position r; Step 203: Repeat step 202. During each repetition, adjust r and / or t to obtain the rD(r, t) curve at different positions r and different thicknesses t, and obtain the attenuation curve A(t, r) for the initial beam of the accelerator at different positions from the beam center axis x.

7. The system according to claim 6, characterized in that Get the decay curve, including: The attenuation coefficient at the position with the highest dose rate is set to 1, and the attenuation coefficient is calculated based on the difference between the predetermined dose and the initial beam dose at each position.

8. The system according to claim 7, characterized in that 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 according to the difference between the initial beam dose distribution and the predetermined dose distribution.

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