Proton rotation intensity modulated radiation method and equipment

Abstract

The invention belongs to the field of medical physical simulation calculation, and provides a proton rotation intensity modulated radiation method and equipment, and the method comprises the steps: S1, carrying out the beam spot filling of a target region; s2, the beam spots are divided into different radiation fields according to the equivalent water depth thickness in the beam spot incidence process; and S3, continuously outputting proton beams in the rotation process of the accelerator to complete the rotation intensity-modulated radiation therapy. The technical scheme of the invention is a novel proton rotation intensity modulated radiation method, and provides more possibilities for the development of the proton rotation intensity modulated radiation therapy technology.

Description

Technical Field

[0001] The present invention belongs to the field of medical physics simulation and calculation, and particularly relates to a method and device for proton rotational intensity modulated radiotherapy. Background Art

[0002] In recent years, proton therapy has attracted the attention of many researchers because of its better target conformity and the ability to treat deep tumors better. After protons enter the human body, a Bragg peak is formed at the end of the range. Most of the energy is deposited at the Bragg peak, and more precise and conformal radiotherapy can be achieved by adjusting the energy to make the Bragg peak fall at a specified position.

[0003] Proton rotational intensity modulated therapy has received much attention because of its ability to continuously output proton beams during the rotation of the gantry. Compared with intensity modulated proton therapy (IMPT), proton rotational intensity modulation can significantly reduce the damage to organs at risk and has the potential advantage of providing robust plan quality. The present invention proposes a method and device for realizing proton rotational intensity modulated radiotherapy by filling the target area with beam spots and dividing the beam spots into radiation fields at different angles. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method and device for proton rotational intensity modulated radiotherapy to solve the problems in the prior art. The technical solution adopted by the present invention is as follows:

[0005] A method for proton rotational intensity modulated radiotherapy, comprising the following steps:

[0006] Step S1: Convert the voxel indices included in the target area into three-dimensional coordinates with the isocenter as the origin, and interpolate the target area coordinates according to the beam spot spacing to obtain the coordinate values of the filled beam spots;

[0007] Step S2: Obtain the equivalent water depth thickness of each beam spot through a path tracking method, and divide the beam spots into different radiation fields according to the equivalent water depth thickness when the beam is incident from different angles;

[0008] Step S3: Continuously output proton beams during the rotation of the accelerator.

[0009] Further, step S1 includes:

[0010] Step S1.1: Coordinate conversion. When importing a case into MATLAB software, the voxels included in the target area can be obtained. The three-dimensional coordinate values of the target area voxels with the isocenter as the origin are obtained by exporting the subscript indices of the voxels, the CT resolution of the voxels, and the coordinate values of the isocenter, denoted as ind_X i 、ind_Y i 、ind_Z ii is the subscript index of the i-th voxel, ct.x, ct.y, ct.z represent the resolution of the CT, isoCenter is the coordinate value of the isocenter with the first voxel in the upper left corner of the CT as the coordinate origin. The coordinate value of the i-th voxel with the isocenter as the origin is:

[0011] X i = ind_X i *ct.x - isoCenter(1)

[0012] Y i = ind_Y i *ct.y - isoCenter(2)

[0013] Z i = ind_Z i *ct.z - isoCenter(3)

[0014] S1.2. Fill the target area with beam spots. Select the beam spots whose Bragg peak deposition positions are on the paths of the incident and exit target areas. Cover the target area in the incident depth direction with the Bragg peaks of the beam spots on this path. Obtain the three-dimensional coordinate values of the target area voxels through step S1.1. Set the beam spot pitch bw = 5 mm, and interpolate the coordinates of the target area voxels to obtain the beam spot coordinate values:

[0015] [x, y, z] = unique(bw * round([XYZ] / bw))

[0016] Among them, the round function is used to round the numerical value to the nearest integer; the unique function is used to obtain unique values.

[0017] Furthermore, step S2 includes:

[0018] Step S2.1. Obtain the equivalent water depth thickness. Calculate the equivalent water depth thickness of the beam incident on the human body to the beam spot coordinates obtained in step S1.2:

[0019] Equivalent water depth thickness = L·ρ

[0020] Among them, L represents the length of the ray passing through the voxel, and ρ represents the tissue density corresponding to the voxel;

[0021] Step S2.2. Divide the beam spots into different fields of view. Calculate the equivalent water depth thickness of the fields of view every 5° in 360° to the beam spot coordinates obtained in step S1.2 through step S2.1, and divide the beam spots with the same equivalent water depth thickness into the same field of view. The energy selected is the energy closest to the Bragg peak deposition position of the equivalent water depth thickness value.

[0022] A proton intensity-modulated radiotherapy device includes a beam spot filling processing module, a beam spot division processing module, and a proton output processing module, where:

[0023] Spot filling processing module, which performs spot filling on the target area;

[0024] Spot division processing module, which divides the spot into different radiation fields according to the equivalent water depth thickness during the incident process of the spot;

[0025] Proton output processing module, which continuously outputs proton beams during the rotation of the accelerator.

[0026] The present invention has the following beneficial effects: The present invention uses a path tracking function to calculate the equivalent water depth thickness of the spot. By first filling the target area with spots and then dividing the spots into different radiation fields for treatment plan delivery, proton intensity modulated radiotherapy can be achieved, which can significantly improve the accuracy, ensure the accuracy and uniformity of target area coverage, and divide the spots into different radiation fields according to the equivalent water depth thickness, realizing the precise delivery of proton beams. Description of the Drawings

[0027] Figure 1 It is a schematic flow chart of the method of the present invention;

[0028] Figure 2 It is a distribution diagram of the brain case after spot filling the target area obtained in Embodiment 1 of the present invention;

[0029] Figure 3 It is a dose distribution diagram of the brain case obtained in Embodiment 1 of the present invention;

[0030] Figure 4 It is a dose-volume histogram of the brain case obtained in Embodiment 1 of the present invention. Specific Embodiments

[0031] Next, in combination with the Figures 1-4 in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. If not specifically specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0032] Such as Figure 1 , a proton intensity modulated radiotherapy method specifically includes the following steps:

[0033] Step S1, convert the voxel index included in the target area into three-dimensional coordinates with the isocenter as the origin, and interpolate the target area coordinates according to the spot pitch to obtain the coordinate values of the spots to be filled.

[0034] Step S1.1. Coordinate transformation. When importing a case into MATLAB software, the voxels contained in the target area can be obtained. By exporting the subscript indices of the voxels, the CT resolution of the voxels, and the coordinate values of the isocenter, the three-dimensional coordinate values of the target area voxels with the isocenter as the origin can be obtained. Denote ind_X i 、ind_Y i 、ind_Z i as the subscript indices of the i-th voxel, ct.x, ct.y, ct.z represent the CT resolution, and isoCenter is the coordinate value of the isocenter with the first voxel in the upper left corner of the CT as the coordinate origin. Then the coordinate value of the i-th voxel with the isocenter as the origin is,

[0035] X i =ind_X i *ct.x - isoCenter(1)

[0036] Y i =ind_Y i *ct.y - isoCenter(2)

[0037] Z i =ind_Z i *ct.z - isoCenter(3)

[0038] Step S1.2. Beam spot filling the target area. The position where the original beam spot deposits energy in the target area, i.e., the energy of the beam spot, is determined by the path tracking method to track the positions where the beam enters and exits the target area, i.e., the equivalent water depth thickness (WET) after the beam enters the human body, given the target area coordinates and the beam coordinates. Select the beam spots whose Bragg peak deposition positions are on the path of the beam entering and exiting the target area, and cover the target area in the incident depth direction with the Bragg peaks of the beam spots on this path. The present invention first proposes beam spot filling the target area. Figure 2 It is a brain case with a prescribed dose of 30 Gy / 15 fractions. Based on obtaining the three-dimensional coordinate values of the target area voxels through Step S1.1, assuming the beam spot spacing is bw = 5 mm, the beam spot coordinate values are obtained by interpolating the coordinates of the target area voxels.

[0039] [x,y,z] = unique(bw*round([XYZ] / bw))

[0040] Among them, this formula uses the MATLAB language. The round function is used to round the numerical value to the nearest integer; the unique function is used to obtain unique values.

[0041] Step S2. Obtain the equivalent water depth thickness (WET) of each beam spot through the path tracking method, and divide the beam spots into different radiation fields according to the WET under the condition that the beam is incident from different angles.

[0042] Step S2.1: Obtain the equivalent water depth thickness (WET). When a high-energy proton beam irradiates water or a medium, there is a Bragg peak at the end of its energy deposition range. In proton radiotherapy, the non-uniform medium has a significant impact on the Bragg peak of the proton beam. Therefore, converting the range of the proton beam after it enters the non-uniform human body into an equivalent water depth can select a more accurate energy and deposit the Bragg peak at a more accurate position. This invention calculates the equivalent water depth thickness of the beam from the entrance of the human body to the beam spot coordinates obtained in step S1.2 through a path tracking function.

[0043] Equivalent water depth thickness = L·ρ

[0044] Where L represents the length of the ray passing through the voxel, and ρ represents the tissue density corresponding to the voxel.

[0045] Step S2.2: Divide the beam spots into different radiation fields. When the proton beam irradiates the human body from different angles and reaches the same beam spot coordinates obtained in step S1.2, the WET values are not equal. In proton intensity-modulated radiotherapy with rotation, in order to continuously output a proton beam during the rotation process, it is required that the energy of each radiation field is equal. In step S2.1, calculate the WET of the radiation fields at intervals of 5° in 360° to the beam spot coordinates obtained in step S1.2, and divide the beam spots with the same WET into the same radiation field. The selected energy is the energy with the WET value closest to the deposition position of the Bragg peak.

[0046] Step S3: Continuously output a proton beam during the rotation of the accelerator to complete intensity-modulated radiotherapy with rotation.

[0047] Regarding the implementation of proton intensity-modulated radiotherapy with rotation, previous studies have achieved continuous output of a proton beam during the rotation of the accelerator. This invention only adjusts the number and energy of the beam spots of each beam, and can also complete the delivery of proton intensity-modulated radiotherapy with rotation.

[0048] This invention also relates to a proton intensity-modulated radiotherapy device with rotation, including a beam spot filling processing module, a beam spot dividing processing module, and a proton output processing module;

[0049] The beam spot filling processing module fills the beam spots in the target area;

[0050] The beam spot dividing processing module divides the beam spots into different radiation fields according to the equivalent water depth thickness (WET) during the incident process of the beam spots;

[0051] The proton output processing module continuously outputs a proton beam during the rotation of the accelerator to complete intensity-modulated radiotherapy with rotation.

[0052] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, variations, modifications, and substitutions made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A proton rotational intensity modulated radiotherapy method, characterized in that, It includes the following steps: Step S1: Convert the voxel indices included in the target area into three-dimensional coordinates with the isocenter as the origin, and interpolate the target area coordinates according to the beam spot pitch to obtain the coordinate values of the filled beam spots; Step S2: Obtain the equivalent water depth thickness of each beam spot through the path tracking method, and divide the beam spots into different radiation fields according to the equivalent water depth thickness in the case of the beam incident from different angles; Step S3: Continuously output proton beams during the rotation of the accelerator.

2. The proton intensity modulated radiation method according to claim 1, characterized in that, Step S1 includes: Step S1.

1. Coordinate transformation. When importing a case into MATLAB software, the voxels contained in the target area can be obtained. By exporting the subscript index of the voxels, the CT resolution of the voxels, and the coordinate values of the isocenter, the three-dimensional coordinate values of the target area voxels with the isocenter as the origin are obtained, denoted as ind_X i , ind_Y i , ind_Z i is the subscript index of the i-th voxel, ct.x, ct.y, ct.z represent the CT resolution, isoCenter is the coordinate value of the isocenter with the first voxel in the upper left corner of the CT as the coordinate origin, and the coordinate value of the i-th voxel with the isocenter as the origin is: X i = ind_X i *ct.x - isoCenter(1) Y i = ind_Y i *ct.y - isoCenter(2) Z i = ind_Z i *ct.z-isoCenter(3) S1.2: Fill the target area with beam spots, select the beam spots whose Bragg peak deposition positions are on the paths of entering and exiting the target area, cover the target area in the incident depth direction with the Bragg peaks of the beam spots on this path, obtain the three-dimensional coordinate values of the target area voxels through Step S1.1, set the beam spot pitch bw = 5mm, and interpolate the coordinates of the target area voxels to obtain the beam spot coordinate values: [x,y,z]=unique(bw*round([XYZ] / bw)) Among them, the round function is used to round the numerical value to the nearest integer; the unique function is used to obtain unique values.

3. The proton intensity modulated radiotherapy method according to claim 2, characterized in that, Step S2 includes: Step S2.1: Obtain the equivalent water depth thickness, and calculate the equivalent water depth thickness of the beam incident on the human body to the beam spot coordinates obtained in Step S1.2: Equivalent water depth thickness = L·ρ Among them, L represents the length of the ray passing through the voxel, and ρ represents the tissue density corresponding to the voxel; Step S2.2: Divide the beam spots into different radiation fields, calculate the equivalent water depth thickness of the radiation fields at every 5° in 360° to the beam spot coordinates obtained in Step S1.2 through Step S2.1, and divide the beam spots with the same equivalent water depth thickness into the same radiation field, and its energy is selected as the energy closest to the Bragg peak deposition position of the equivalent water depth thickness value.

4. A proton intensity-modulated radiotherapy device, which adopts a proton intensity-modulated radiotherapy method according to claim 1, characterized in that, It includes a beam spot filling processing module, a beam spot division processing module, and a proton output processing module, where: The beam spot filling processing module fills the target area with beam spots; The beam spot division processing module divides the beam spots into different radiation fields according to the equivalent water depth thickness during the beam spot incident process; The proton output processing module continuously outputs proton beams during the rotation of the accelerator.

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