A Bragg peak broadening method for point scanning proton or heavy ion beam and a radiotherapy system

Abstract

The present invention discloses a Bragg peak broadening method for a point scanning proton or heavy ion beam and a radiotherapy system. The Bragg peak broadening method is characterized in that a porous material is placed on the path of the point scanning proton or heavy ion beam, the porous material is perpendicular to the beam travel direction, and the point scanning proton or heavy ion beam generates energy stratification (Energy Straggling) after passing through the porous material, thereby broadening the Bragg peak of the proton or heavy ion beam. This method can broaden the Bragg peak of the proton or heavy ion beam, can reduce the number of energy layers required for proton or heavy ion treatment, and thus can improve the treatment efficiency of the point scanning proton or heavy ion equipment.

Description

Technical Field

[0001] The invention relates to the field of medical radiotherapy, and in particular to a Bragg peak broadening method for point scanning proton or heavy ion beam and a radiotherapy system. Background Art

[0002] Protons and heavy ions are currently advanced treatment technologies in the field of radiotherapy. Since ions have the physical properties of the Bragg peak, they can quickly deposit energy in the Bragg peak area, while the dose in the incident area and the end of the beam is low, thereby reducing the exposure dose to normal tissues around the target area.

[0003] As a cutting-edge technology in ion radiotherapy, point scanning technology is gradually replacing passive beam transmission technology using compensators and collimators. However, the Bragg peak width of monoenergetic protons or heavy ions, especially low-energy heavy ions, is very small. For example, the half-width of the Bragg peak of 160MeV / u carbon ions is less than 1mm. Radiotherapy using this carbon ion beam requires the superposition of many layers of monoenergetic carbon ions with different energies to ensure the dose flatness of the treatment target volume (PTV). Usually, a passive energy modulation device is placed on the beam path to broaden the Bragg peak of the heavy ions, thereby obtaining a Bragg peak with a larger half-width, thereby reducing the number of monoenergetic heavy ion layers required and improving irradiation efficiency.

[0004] The most common device for broadening the Bragg peak is a ridge filter. It is made of a PMMA plate with a 3mm thick pin structure. This structure has been used in carbon ion beam therapy. However, after the beam passes through the device with this structure, it needs to be transported over a long distance to become uniform (60cm-80cm). In addition, due to the scattering effect of the device, the lateral broadening of the proton beam will be significantly increased, so ridge filters are usually not used in proton beam therapy. Summary of the invention

[0005] The object of the present invention is to provide a Bragg peak broadening method for point scanning proton or heavy ion beam which can achieve the broadening of the Bragg peak.

[0006] The technical solution adopted by the present invention to solve the above problems is:

[0007] A Bragg peak broadening method for point scanning proton or heavy ion beam, characterized in that:

[0008] Place the porous material in the path of the point scanning proton or heavy ion beam, with the porous material perpendicular to the beam travel direction.

[0009] The point scanning proton or heavy ion beam produces energy strangulation after passing through the porous material, thereby broadening the Bragg peak of the proton or heavy ion beam.

[0010] As a preferred method, the steps for matching the beam Bragg peak broadening degree and the thickness of the porous material required clinically are as follows:

[0011] (1) Step S1, by measuring the integrated depth dose distribution curve (IDD) of the monoenergetic beam and the integrated depth dose distribution curve after being broadened by the porous material, the equivalent water thickness of the porous material is calculated;

[0012] (2) Step S2, obtaining the Bragg peak broadening capability of the porous material for a proton or heavy ion beam through iteration;

[0013] (3) Step S3, manufacturing a porous material beam Bragg peak broadening device of corresponding thickness according to the broadening ability of the porous material and the beam Bragg peak broadening degree required clinically.

[0014] Preferably, the function formula for the degree of expected broadening of the Bragg peak of the proton or heavy ion beam is:

[0015]

[0016] Using the dataset BM0(z) and the dataset BM mod (z), calculate the thickness D of the porous material t, and iterate to get σ t ,

[0017] In the formula, Br mod (z) is the expected broadening degree or IDD of a proton or heavy ion beam after passing through a porous material; Br0(z) is the measured IDD of a monoenergetic proton or heavy ion beam; z is the equivalent water thickness through which the beam passes; N(t'|t,σ t ) is the probability that the equivalent water thickness is t' when the proton or heavy ion beam flows through the porous material; t is the equivalent water thickness of the porous material; σ t It is the ability of porous materials to broaden the Bragg peak of proton or heavy ion beam.

[0018] Preferably, in step S1, the calculation method of the equivalent water thickness t of the porous material is as follows:

[0019] (1) Step S1.1: Using the BM0(z) data set, fit the z value at 80% of the peak height at the end of the Bragg peak, denoted as z p80％ ;

[0020] (2) Step S1.2, using BMmod (z) data set, the z value at 80% of the peak height at the end of the Bragg peak is obtained by fitting, denoted as z' p80％ ;

[0021] (3) Step S1.3, the average equivalent water thickness t of the porous material with a thickness D is calculated by formula 3:

[0022] t=z p80％ -z' p80％ (3)

[0023] Preferably, in step S2, the Bragg peak broadening capability σ of the porous material to the proton or heavy ion beam is t The iterative calculation method is as follows:

[0024] (1) Step S2.1, initialization σ t =1, maximum number of iterations MaxP = 100000, data set B mod (z), data set B0(z), equivalent water thickness t;

[0025] (2) Step S2.2, calculate BM0(z) and N(t'|t,σ t ) is convolved to get BC mod (z) dataset;

[0026] (3) Step S2.3, calculate the data set BC moc (z) with the dataset BM mod (z) The average error Err between each point m Denoted as e;

[0027] (4) Step S2.4, P = P + 1;

[0028] (5) Step S2.5, compare P with MaxP. If P is greater than MaxP, jump to step 2.8 and output the result σ t , otherwise, randomly generate σ t ';

[0029] (6) Step S2.6, calculate the convolution of BM0(z) and N' by using Formula 1 and Formula 2 to obtain BC' mod (z) dataset;

[0030] (7) Step S2.7, calculate the data set BC' mod (z) with dataset BM mod (z) The average error Err between each point m ', if Err m '>e, continue to step 4, otherwise σ t =σ t ';, continue to step 4;

[0031] (8) Step S2.8, output the Bragg peak broadening ability σ of the porous material to the proton or heavy ion beam t ;

[0032] Preferably, in step S3, according to the broadening capability of the porous material and the beam Bragg peak broadening degree required clinically, a method for manufacturing a porous material beam Bragg peak broadening device of corresponding thickness is as follows:

[0033] (1) Step S3.1: Using Formula 1 and Formula 2, input σ t , by iteratively adjusting t, BC with different degrees of broadening are obtained mod (z) dataset.

[0034] (2) Step S3.2, obtain each BC by fitting mod The difference between the half-width at half maximum of the (z) data set and the BM0(z) data set, n is the Bragg peak broadening of the proton or carbon ion beam required clinically, FWHM mod -FWHM0≥n, that is, the calculated broadening degree meets the clinical needs, and when the Bragg peak broadening of the proton or carbon ion beam is n, the average equivalent water thickness of the required porous material is t.

[0035] Preferably, the porous material is a material that is internally porous or a porous material generated when stacked.

[0036] Compared with the prior art, the present invention has the following advantages and effects:

[0037] (1) This method can broaden the Bragg peak of the proton or heavy ion beam, which can reduce the number of energy layers required for proton or heavy ion treatment, thereby improving the treatment efficiency of the point scanning proton or heavy ion device.

[0038] (2) When this method is used to broaden the Bragg peak of a proton or heavy ion beam, it can be used close to the patient without affecting the uniformity of the beam.

[0039] (3) When this method is used to broaden the Bragg peak of a proton or heavy ion beam, it can be applied to broaden the Bragg peak of a proton beam when used close to a patient without significantly increasing the side scatter of the proton beam.

[0040] (4) This method uses porous materials to broaden the Bragg peak of a proton or heavy ion beam. The equipment is simple and feasible with low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the structure of the radiotherapy system according to an embodiment of the present invention.

[0042] Figure 2 Schematic diagram of the structure of the Bragg peak broadening device of the radiotherapy system according to the embodiment of the present invention.

[0043] Figure 3 It is a schematic diagram of the installation structure of the container of the radiotherapy system according to an embodiment of the present invention.

[0044] Figure 4 Schematic diagram of the upper structure of the container of the radiotherapy system according to the embodiment of the present invention.

[0045] Figure 5 Schematic diagram of the bottom structure of the container of the radiotherapy system according to an embodiment of the present invention.

[0046] Figure 6 It is a schematic flow chart of the Bragg peak broadening method according to an embodiment of the present invention.

[0047] Figure 7 It is a schematic diagram of the range shift and Bragg peak broadening effect produced by monoenergetic carbon ions after stacking spherical nano-mineral crystals with a geometric thickness of 5 cm and PP plastic particles in an embodiment of the present invention.

[0048] Numbers in the figure: beam emitting end 1, patient positioning platform 2, Bragg peak broadening device 3, container 4, bracket 5, left container part 41, first enclosure 411, second enclosure 412, third enclosure 413, bottom plate 414, side support plate 415, right container part 42, baffle 421, baffle fixing frame 422, third guide rod 431, fourth adjusting screw 432, rotating column 433, adjusting worm gear 434, adjusting worm 435, base 51, first adjusting structure 5 2, first sliding seat 521, first adjusting screw 522, first guide rod 523, second adjusting structure 53, second sliding seat 531, second adjusting screw 532, second guide rod 533, third adjusting structure 54, mounting plate 541, first connecting rod 542, second connecting rod 543, first sliding block 544, third connecting rod 545, fourth connecting rod 546, second sliding block 547, second connecting block 548, third adjusting screw 549, first connecting block 5410 DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and by way of examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0050] See also Figure 1-Figure 6The radiotherapy system of this embodiment includes a synchrotron for accelerating protons and heavy ions, a beam emitting end 1 for emitting a beam, and a patient positioning platform 2 for adjusting the position of a patient, and is characterized in that a Bragg peak broadening device 3 is arranged between the beam emitting end 1 and the patient positioning platform 2, the Bragg peak broadening device 3 includes a container 4 and a bracket 5 for fixing the container 4, the container 4 is filled with a porous material, and in a working state, the left side and the right side of the container 4 are perpendicular to the beam emission direction.

[0051] The container 4 includes a left container part 41 and a right container part 42. The left side surface and the right side surface of the container 4 are respectively located on the left container part 41 and the right container part 42. The left container part 41 and the right container part 42 are relatively slidably arranged, and the thickness of the accommodating space of the container 4 can be adjusted.

[0052] The bracket 5 includes a base 51 on which are mounted a first adjustment structure 52 for adjusting the left-right position of the container 4 , a second adjustment structure 53 for adjusting the front-back position of the container 4 , and a third adjustment structure 54 for adjusting the top-bottom position of the container 4 .

[0053] The first adjustment structure 52 includes a first sliding seat 521, a first adjustment screw 522, a first adjustment nut, and a first guide rod 523. The first sliding seat 521 is slidably installed on the base 51 through the first guide rod 523. The first adjustment nut is fixed on the first sliding seat 521. The first adjustment screw 522 is rotatably installed on the base 51. The first adjustment screw 522 and the first adjustment nut cooperate, and the first adjustment screw 522 is arranged in the left and right directions.

[0054] The second adjustment structure 53 includes a second sliding seat 531, a second adjustment screw 532, a second adjustment nut, and a second guide rod 533. The second sliding seat 531 is slidably installed on the first sliding seat 521 through the second guide rod 533. The second adjustment nut is fixed on the second sliding seat 531. The second adjustment screw 532 is rotatably installed on the first sliding seat 521. The second adjustment screw 532 and the second adjustment nut cooperate, and the second adjustment screw 532 is arranged in the front-to-back direction.

[0055] The third adjustment structure 54 includes a mounting plate 541, a first connecting rod 542, a second connecting rod 543, a first slider 544, a third connecting rod 545, a fourth connecting rod 546, a second slider 547, a mounting plate 541, a third adjusting screw 549, a third adjusting nut, a first connecting block 5410 and a second connecting block 548. The middle part of the first connecting rod 542 and the middle part of the second connecting rod 543 are hinged. The upper end of the first connecting rod 542 and the upper end of the second connecting rod 543 are hinged to the mounting plate 541 and the first slider 544 respectively. The first slider 544 is slidably mounted on the mounting plate 541. The middle part of the third connecting rod 545 and the middle part of the fourth connecting rod 546 are hinged. The lower end of the third connecting rod 545 and the upper end of the fourth connecting rod 546 are hinged to the second sliding seat 531 and the second slider 547 respectively. The second slider 547 is slidably installed on the second sliding seat 531. The lower end of the first connecting rod 542 and the upper end of the third connecting rod 545 are hinged to the first connecting block 5410. The lower end of the second connecting rod 543 and the upper end of the fourth connecting rod 546 are hinged to the second connecting block 548. One end of the third adjusting screw 549 is rotatably installed on the second connecting block 548. The third adjusting nut is fixed on the first connecting block 5410. The third adjusting screw 549 and the third adjusting nut cooperate with each other, and the axis of the third adjusting screw 549 is set in the left and right direction.

[0056] The left container part 41 includes a first enclosing plate 411, a second enclosing plate 412, a third enclosing plate 413 and a bottom plate 414, wherein the first enclosing plate 411, the second enclosing plate 412 and the third enclosing plate 413 are respectively fixed to the front, left and right sides of the bottom plate 414, and the right container part 42 includes a baffle 421 and a baffle fixing frame 422, wherein the lower end of the baffle 421 is fixed to the baffle fixing frame 422, and the front end, the rear end and the lower end of the baffle 421 are respectively abutted against the first enclosing plate 411, the third enclosing plate 413 and the bottom plate 414 (the baffle 421 can slide relative to the first enclosing plate 411 and the third enclosing plate 413). , the distance between the front end of the baffle 421 and the first enclosure 411, the distance between the rear end of the baffle 421 and the third enclosure 413, and the distance between the lower end of the baffle 421 and the bottom plate 414 are controlled within 3 mm), the side support plate 415 is fixed on the bottom plate 414, the baffle fixing frame 422 is slidably installed on the side support plate 415 through the third guide rod 431, and the fourth adjusting screw 432 is rotatably installed on the side support plate 415, and the fourth adjusting screw 432 is located below the bottom plate 414, and the fourth adjusting nut is fixed on the baffle fixing frame 422, and the fourth adjusting screw 432 and the fourth adjusting nut cooperate with each other.

[0057] A rotating column 433 is fixed on the bottom plate 414 , and the rotating column 433 is rotatably mounted on the mounting plate 541 . An adjusting worm wheel 434 is fixed on the rotating column 433 , and an adjusting worm 435 is rotatably mounted on the mounting plate 541 . The adjusting worm wheel 434 and the adjusting worm 435 cooperate with each other.

[0058] The porous material is made of plastic foam, coal-based activated carbon, coconut shell activated carbon, spherical nano-mineral crystals, solid gel particles or solid plastic PP particle materials, and gaps are generated when stacked to form the porous material.

[0059] The container 4 is made of organic glass (PMMA) or carbon fiber board.

[0060] like Figure 5 As shown, the present embodiment provides a Bragg peak broadening method for point scanning proton or heavy ion beam, comprising the following steps:

[0061] (1) Filling and encapsulating the porous material in a container with a flat surface made of a non-metallic material;

[0062] (2) placing the container in the path of the point scanning proton or heavy ion beam, perpendicular to the direction of beam travel;

[0063] (3) Point scanning of proton or heavy ion beams, which produces energy strangulation after passing through porous materials, thereby broadening the Bragg peak of the proton or heavy ion beam.

[0064] Among them, the steps for matching the beam Bragg peak broadening required clinically with the thickness of the porous material are as follows:

[0065] (1) Step S1, by measuring the integrated depth dose distribution curve (IDD) of the monoenergetic beam and the integrated depth dose distribution curve after being broadened by the porous material, the equivalent water thickness of the porous material is calculated;

[0066] (2) Step S2, obtaining the Bragg peak broadening capability of the porous material for a proton or heavy ion beam through iteration;

[0067] (3) Step S3, manufacturing a porous material beam Bragg peak broadening device of corresponding thickness according to the broadening ability of the porous material and the beam Bragg peak broadening degree required clinically.

[0068] The following describes in detail the method and device for broadening the Bragg peak of a proton or heavy ion beam by taking the example of broadening the half-width of the Bragg peak of a carbon ion with an energy of 234.05 MeV / u by 6 mm.

[0069] The screened 2mm diameter nano-crystals are encapsulated in a container made of carbon fiber board. The internal space of the container is a rectangular structure with a length, width and height of 20cm, 5cm and 20cm respectively. The left and right end faces of the manufactured container are placed vertically on the beam path, at the front end of the peak-seeking device.

[0070] Using the peak-finding equipment, the IDD0 of the 235.05MeV / u monoenergetic carbon ion beam was measured.

[0071] The data set BM0(z) is used to represent the IDD of 235.05 MeV / u carbon ions after passing through the beam Bragg peak broadening device. mod , using the data set BM mod (z) indicates.

[0072] The functional formula for the degree to which the Bragg peak of a proton or heavy ion beam is expected to be broadened is:

[0073]

[0074] In the formula, BC mod (z) is the expected broadening degree or IDD of the proton or heavy ion beam after passing through the nanocrystalline; BM0(z) is the measured IDD of the monoenergetic proton or heavy ion beam; z is the equivalent water thickness through which the beam passes; N(t'|t,σ t ) is the probability that the equivalent water thickness is t' when the proton or heavy ion beam flows through the nano-mineral crystal; t is the average equivalent water thickness of the nano-mineral crystal; σ t It is the Bragg peak broadening ability of the proton or heavy ion beam after passing through the nano-mineral crystal.

[0075] (Note: The equivalent water thickness z that the beam passes through is not a specific value, but a data set. It is obtained through measurement. When measuring IDD (Integrated depth dose distribution curve of monoenergetic beam), z is the horizontal coordinate and is a variable. Note that z in formula 2 and z behind it are p80％ There is a difference. The z here is the data set, and the z behind it is p80％ , is the z value at 80% of the peak height at the end of the Bragg peak obtained by interpolating the data set z. For foaming materials with fixed geometric thickness, it is a fixed value.

[0076] The equivalent water thickness t' is an array consisting of the average equivalent water thickness t of the nanocrystalline and the Bragg peak broadening ability σ t It is the horizontal coordinate of N. N is a normal distribution function, which can be determined by only two parameters, t and σ. Then, a certain number of values ​​corresponding to the horizontal and vertical coordinates are taken as data groups for subsequent convolution operations and iterations.

[0077] Using the dataset BM0(z) and the dataset BM mod (z), calculate the t of 5cm thick spherical nano-crystal, and iterate to get σ t .

[0078] The calculation method of t is further described in detail:

[0079] (1) Step 1. Using the BM0(z) data set, fit the z value at 80% of the peak height at the end of the Bragg peak, denoted as z p80％ ;

[0080] (2) Step 2. Using BM mod (z) data set, the z value at 80% of the peak height at the end of the Bragg peak is obtained by fitting, denoted as z' p80％ ;

[0081] (3) Step 3. The average equivalent water thickness t of 5 cm thick spherical nano-mineral crystals is calculated by formula 3 to be 4 g / cm 2 :

[0082] (4) t = z p80％ -z' p80％ (3)

[0083] For σ t The iterative calculation method is further described in detail:

[0084] (1) Step 1. Initialize σ t =1, maximum number of iterations MaxP = 100000, data set B mod (z), data set B0(z), equivalent water thickness t;

[0085] (2) Step 2. Calculate BM0(z) and N(t'|t,σ t ) is convolved to get BC mod (z) dataset;

[0086] (3) Step 3. Calculate the data set BC mod (z) with dataset BM mod (z) The average error Err between each point m Denoted as e;

[0087] (4) Step 4. P = P + 1;

[0088] (5) Step 5. Compare P and MaxP. If P is greater than MaxP, jump to step 8 and output the result σ t , otherwise, randomly generate σ t ';

[0089] (6) Step 6. Using Formula 1 and Formula 2, calculate the convolution of BM0(z) and N' to obtain BC' mod (z) dataset;

[0090] (7) Step 7. Calculate the data set BC' mod (z) with dataset BMmod (z) The average error Err between each point m ', if Err m '>e, continue to step 4. Otherwise σ t =σ t ';, continue to step 4;

[0091] (8) Step 8. Output result σ t ;

[0092] The Bragg peak broadening ability σ of 5 cm thick spherical nano-crystal to proton or heavy ion beam is obtained. t 0.242g / cm 2 .

[0093] Assuming that clinical needs to broaden the Bragg peak of the proton or carbon ion beam by 6 mm, use Formula 1 and Formula 2 to input σ t , by iteratively adjusting t, BC with different degrees of broadening are obtained mod (z) data set. By fitting, we can get each BC mod The difference between the half-width at half maximum of the (z) dataset and the BM0(z) dataset, FWHM mod - When FWHM0≥6mm, the calculated broadening degree meets clinical needs. The average equivalent water thickness t of spherical nano-crystals required for the Bragg peak broadening of proton or carbon ion beam to 6mm is 1.83g / cm 2 .

[0094] The required geometric thickness D can be calculated by proportional calculation. As it has been measured that when D = 5cm, the value of t is 4g / cm 2 Then the iterative value of t is 1.83 g / cm 2 , the corresponding D value only needs to be obtained through inverse proportion. D / 1.83=5 / 4, when the clinical need is to widen the Bragg peak of the proton or carbon ion beam by 6mm, D=5 / 4*1.83=2.29cm.

[0095] The above contents described in this specification are merely examples of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, as long as they do not deviate from the contents of the present specification or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for broadening the Bragg peak of a point scanning proton or heavy ion beam, characterized in that: (1) Place the porous material on the path of the point scanning proton or heavy ion beam, with the porous material perpendicular to the beam travel direction. (2) Point scanning of the proton or heavy ion beam, which generates energy straggle after passing through the porous material, thereby broadening the Bragg peak of the proton or heavy ion beam; The steps for matching the beam Bragg peak broadening required clinically with the thickness of the porous material are as follows: (1) Step S1, by measuring the integrated depth dose distribution curve (IDD) of the monoenergetic beam and the integrated depth dose distribution curve after being broadened by the porous material, the equivalent water thickness of the porous material is calculated; (2) Step S2, obtaining the Bragg peak broadening capability of the porous material for a proton or heavy ion beam by iteration; (3) Step S3, manufacturing a porous material beam Bragg peak broadening device of corresponding thickness according to the broadening ability of the porous material and the beam Bragg peak broadening degree required clinically; The formula used to calculate the equivalent water thickness of the porous material in step S1 includes: The degree to which one can expect to broaden the Bragg peak of a proton or heavy ion beam is given by: Using the dataset BM0(z) and the dataset BM mod (z), calculate t of the porous material with geometric thickness D, and iterate to get σ t , In the formula, Br mod (z) is the expected broadening degree or IDD of a proton or heavy ion beam after passing through a porous material; Br0(z) is the measured IDD of a monoenergetic proton or heavy ion beam; z is the equivalent water thickness through which the beam passes; N(t'|t,σ t ) is the probability that the equivalent water thickness is t' when the proton or heavy ion beam flows through the porous material; t is the equivalent water thickness of the porous material; σ t The ability of porous materials to broaden the Bragg peak of proton or heavy ion beams; In step S1, the calculation method of the equivalent water thickness t of the porous material is as follows: (1) Step S1.1: Using the BM0(z) data set, fit the z value at 80% of the peak height at the end of the Bragg peak, denoted as z p80％ ; (2) Step S1.2, using BM mod (z) data set, the z value at 80% of the peak height at the end of the Bragg peak is obtained by fitting, denoted as z' p80％ ; (3) Step S1.3, the average equivalent water thickness t of the porous material with a thickness D is calculated by formula 3: t=z p80％ -z' p80％ (Formula 3); In step S2, the Bragg peak broadening capability σ of the porous material to the proton or heavy ion beam t The iterative calculation method is as follows: (1) Step S2.1, initialization σ t =1, maximum number of iterations MaxP = 100000, data set B mod (z), data set B0(z), equivalent water thickness t; (2) Step S2.2, calculate BM0(z) and N(t'|t,σ t ) is convolved to get BC mod (z) dataset; (3) Step S2.3, calculate the data set BC mod (z) with dataset BM mod (z) The average error Err between each point m Denoted as e; (4) Step S2.4, P = P + 1; (5) Step S2.5, compare P with MaxP. If P is greater than MaxP, jump to step 2.8 and output the result σ t , otherwise, randomly generate σ t '; (6) Step S2.6, calculate the convolution of BM0(z) and N' by using Formula 1 and Formula 2 to obtain BC' mod (z) dataset; (7) Step S2.7, calculate the data set BC' mod (z) and the data set BM mod (z), and calculate the average error Err m ’ between each point. If Err m ’ < e, continue with step 4, otherwise σ t = σ t ', and continue with step 4; (8) Step S2.8, output the Bragg peak broadening ability σ of the porous material to the proton or heavy ion beam t ; In step S3, according to the broadening ability of the porous material and the beam Bragg peak broadening degree required clinically, a method for manufacturing a porous material beam Bragg peak broadening device of corresponding thickness is as follows: (1) Step S3.1: Using Formula 1 and Formula 2, input σ t , by iteratively adjusting t, BC with different degrees of broadening are obtained mod (z) dataset; (2) Step S3.2, obtain each BC by fitting mod The difference between the half-width at half maximum of the (z) data set and the BM0(z) data set, n is the Bragg peak broadening of the proton or carbon ion beam required clinically, FWHM mod -FWHM0≥n, that is, the calculated broadening degree meets the clinical needs, and when the Bragg peak broadening of the proton or carbon ion beam is n, the average equivalent water thickness of the required porous material is t.

2. The Bragg peak broadening method according to claim 1, characterized in that: The porous material is made of plastic foam, coal-based activated carbon, coconut shell activated carbon, spherical nano-mineral crystals, solid gel particles or solid plastic PP particle materials, and gaps are generated when stacked to form the porous material.

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