CN113821970B - EPID gray scale-fluence calibration method, medium and equipment - Google Patents
EPID gray scale-fluence calibration method, medium and equipment Download PDFInfo
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- CN113821970B CN113821970B CN202110855134.1A CN202110855134A CN113821970B CN 113821970 B CN113821970 B CN 113821970B CN 202110855134 A CN202110855134 A CN 202110855134A CN 113821970 B CN113821970 B CN 113821970B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
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- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
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- A61N5/1048—Monitoring, verifying, controlling systems and methods
- A61N5/1071—Monitoring, verifying, controlling systems and methods for verifying the dose delivered by the treatment plan
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- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
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Abstract
The invention discloses an EPID gray-fluence calibration method, medium and equipment, wherein the method comprises the following steps: (1) The method comprises the steps of opening a radiation source into a radiation field with a certain size, irradiating an EPID with a certain MU, and collecting and forming a gray image; (2) Smoothing the gray level image, calculating the average value of the gray level of the central pixel, and determining the conversion factor of the gray level and the fluence of the portal image according to the corresponding MU value; (3) determining the EPID surface fluence; (4) And calculating to obtain a gray image on the EPID based on the EPID surface fluence and convolution kernel, taking the calculated gray image and the average value difference absolute value of the acquired gray image as an optimization target, and obtaining EPID calibration model parameters through an optimization algorithm. The invention is based on convolution and optimization method, can quickly obtain accurate calibration parameters, improves the efficiency of EPID gray-fluence calibration, and solves the problems of slow calibration process, low efficiency, incapability of ensuring the quality of results and the like existing in the traditional mode through direct calculation and manual parameter adjustment.
Description
Technical Field
The invention relates to the application fields of nuclear energy and nuclear technology, such as radiotherapy, industrial nondestructive testing and the like, in particular to an EPID gray scale-fluence calibration method, medium and equipment.
Background
The EPID receives radiation irradiation to generate a gray image, and the radiation source and the medium can be reconstructed and analyzed based on the gray image, so that the EPID is widely applied to the fields of radiation therapy dose monitoring, radiation therapy positioning, industrial nondestructive testing, medical image reconstruction and the like. Because the EPID surface has the influence of scattering, when the fluence of the radiation source is reversely pushed based on the EPID gray level image, certain deviation can be generated, the generated source intensity is inaccurate, and accurate input information can be provided for the radiation source and medium reconstruction only by modeling the EPID surface scattering, so that the research on the EPID gray level-fluence calibration method has important significance for radiation therapy monitoring, industrial detection, radiation therapy positioning, medical image reconstruction and the like.
At present, an EPID gray-fluence calibration method generally adopts a direct calculation and manual parameter adjustment mode, the contribution of each point to the fluence is calculated through manually set model parameters to obtain a gray map, then compared with the acquired gray map, the model parameters considered to be better by a modeler are continuously tried to be acquired, the calculated amount of the method is huge, the manual parameter adjustment is carried out, so that the EPID gray-fluence calibration process time is long, the calibration result quality cannot be ensured, and therefore, a method for rapidly calibrating the EPID by using optimization is necessary to develop.
Disclosure of Invention
The invention aims to: the invention aims to provide a rapid EPID gray-fluence calibration method, medium and equipment, which are used for solving the problem that EPID gray-fluence calibration is required in the fields of radiotherapy dose monitoring, industrial nondestructive testing, medical image reconstruction and the like.
The technical scheme is as follows: the invention discloses an EPID gray-fluence calibration method, which comprises the following steps:
(1) The method comprises the steps of opening a radiation source into a radiation field with a certain size, irradiating an EPID with a certain MU, and collecting and forming a gray image;
(2) Smoothing the gray level image acquired in the step (1) to obtain a smoothed gray level image, calculating the average value of the gray level of the central pixel according to the smoothed gray level image, and determining the conversion factor of the gray level and the fluence of the portal image according to the corresponding MU value;
(3) According to the principle of similar triangle, calculating the EPID surface fluence according to the field size of the ray source and the distance from the ray source to the EPID;
(4) And calculating to obtain a gray image on the EPID based on the EPID surface fluence and convolution kernel, taking the calculated gray image and the average value difference absolute value of the acquired gray image as an optimization target, and obtaining EPID calibration model parameters through an optimization algorithm.
The step (1) specifically comprises the following steps:
(1.1) setting the opening size and the beam output MU of a ray source;
(1.2) irradiating the EPID;
(1.3) collecting gray-scale images generated on the portal imaging device.
The step (2) specifically comprises the following steps:
(2.1) smoothing the acquired gray level image;
(2.2) calculating an average gray value of the gray image center area;
and (2.3) calculating the conversion factor of the gray scale and the fluence of the emergent field image according to the average gray scale value and the MU value of the central area.
The step (4) specifically comprises the following steps:
(4.1) calculating the convolution kernel under the current solution according to the convolution kernel expression
(4.2) According to the formulaCalculating to obtain a Gray image Gray Epid C under the solution, wherein F D2G Gray and fluence conversion factors and F Epid are fluence graphs;
And (4.3) taking the minimum absolute value of the mean value difference between Gray Epid Ci and Gray EPIDM as an optimization target, and obtaining an optimal solution by using an optimization method, namely the optimal solution of the current model.
A computer storage medium having stored thereon a computer program which when executed by a processor implements the EPID gray-fluence calibration method described above.
A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the EPID gray-fluence calibration method described above when executing the computer program.
The beneficial effects are that: compared with the prior art, the invention has the following advantages: 1. the invention is based on convolution and optimization method, can rapidly obtain accurate calibration parameters, and improves the efficiency of EPID gray-fluence calibration; 2. the invention solves the problems of slow calibration process, low efficiency, incapability of ensuring the quality of results and the like in the traditional mode through direct calculation and manual parameter adjustment.
Drawings
FIG. 1 is a flow chart of an EPID gray-fluence calibration method.
Detailed Description
The technical scheme of the invention is further described below with reference to the accompanying drawings.
Example 1:
as shown in FIG. 1, the EPID gray-fluence calibration method comprises the following steps:
(1) The radiation source is opened to a certain size of radiation field, and the EPID is irradiated by a certain MU, so that a gray image is acquired and formed.
(1.1) Setting a portal imaging device standard; setting SSD as 100cm, setting SID as 160cm, and irradiating the accelerator with 10cm multiplied by 10cm radiation field with the irradiation intensity of 50MU;
(1.2) irradiating the EPID without any medium placed between the portal imaging devices;
(1.3) collecting gray-scale images generated on the portal imaging device.
(2) And (3) carrying out smoothing treatment on the gray level image acquired in the step (1) to obtain a smoothed gray level image, calculating the average value of the gray level of the central pixel according to the smoothed gray level image, measuring the gray level image and the corresponding MU value, and determining the conversion factors of the gray level and the fluence of the portal image.
(2.1) Performing Gaussian smoothing on the image;
(2.2) calculating the average gray value of 10 x 10 pixels in the center of the gray image;
and (2.3) calculating conversion factors of gray scale and fluence of the field image according to the average gray scale value of the gray scale image center and MU of the field.
(3) According to the principle of similar triangle, the EPID surface fluence is calculated from the field size of the source and the distance from the source to the EPID.
From the position parameters of the source and the EPID, the fluence of the region 16cm x 16cm in the center of the EPID surface was calculated to be 1.
(4) And calculating to obtain a gray image on the EPID based on the EPID surface fluence and convolution kernel, taking the absolute value of the mean value difference of the calculated gray image and the acquired dose image as an optimization target, and obtaining EPID calibration model parameters through an optimization algorithm.
(4.1) Calculating the convolution kernel under the current solution according to the convolution kernel expression
(4.2) According to the formulaCalculating to obtain a Gray image Gray Epid C under the solution, wherein F D2G Gray and fluence conversion factors and F Epid are fluence graphs;
And (4.3) taking the minimum absolute value of the mean value difference between Gray Epid Ci and Gray EPIDM as an optimization target, and obtaining an optimal solution by using an optimization method, namely the optimal solution of the current model.
Example 2:
a computer storage medium having stored thereon a computer program which when executed by a processor implements the EPID gray-fluence calibration method described above.
Example 3:
a computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the EPID gray-fluence calibration method described above when executing the computer program.
Claims (5)
1. The EPID gray-fluence calibration method is characterized by comprising the following steps:
(1) The method comprises the steps of opening a radiation source into a radiation field with a certain size, irradiating an EPID with a certain MU, and collecting and forming a gray image;
(2) Smoothing the gray level image acquired in the step (1) to obtain a smoothed gray level image, calculating the average value of the gray level of the central pixel according to the smoothed gray level image, and determining the conversion factor of the gray level and the fluence of the portal image according to the corresponding MU value;
(3) According to the principle of similar triangle, calculating the EPID surface fluence according to the field size of the ray source and the distance from the ray source to the EPID;
(4) Calculating to obtain a gray image on the EPID based on the EPID surface fluence and convolution kernel, taking the calculated gray image and the average value difference absolute value of the acquired gray image as an optimization target, and obtaining EPID calibration model parameters through an optimization algorithm; the step (4) is specifically as follows:
(4.1) calculating the convolution kernel under the current solution according to the convolution kernel expression
(4.2) According to the formulaCalculating to obtain a Gray image Gray EpidC under the solution, wherein F D2G Gray and fluence conversion factors and F Epid are fluence graphs;
And (4.3) taking the minimum absolute value of the mean value difference between Gray EpidC and Gray EPIDM as an optimization target, and obtaining an optimal solution by using an optimization method, namely the optimal solution of the current model, wherein Gray EPIDM represents a measurement Gray level image of the detection point.
2. The method according to claim 1, wherein the step (1) is specifically:
(1.1) setting the opening size and the beam output MU of a ray source;
(1.2) irradiating the EPID;
(1.3) collecting gray-scale images generated on the portal imaging device.
3. The method according to claim 1, wherein the step (2) is specifically:
(2.1) smoothing the acquired gray level image;
(2.2) calculating an average gray value of the gray image center area;
and (2.3) calculating the conversion factor of the gray scale and the fluence of the emergent field image according to the average gray scale value and the MU value of the central area.
4. A computer storage medium having stored thereon a computer program which, when executed by a processor, implements the EPID gray-fluence calibration method as claimed in any one of claims 1-3.
5. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the EPID gray scale-fluence calibration method of any one of claims 1-3 when the computer program is executed by the processor.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5295200A (en) * | 1991-01-09 | 1994-03-15 | Board Of Regents, The University Of Texas System | Method and apparatus for determining the alignment of an object |
| CN107041997A (en) * | 2016-02-05 | 2017-08-15 | 瓦里安医疗系统国际股份公司 | Beam of radiation is directed at the system measured with beam of radiation, method and apparatus |
| CN110237445A (en) * | 2019-07-05 | 2019-09-17 | 北京理工大学 | Based on EPID body 3-dimensional dose monitoring and verification method |
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| EP2701605A4 (en) * | 2011-04-27 | 2014-10-01 | Univ Virginia Commonwealth | 3d tracking of an hdr source using a flat panel detector |
| US9089696B2 (en) * | 2013-11-07 | 2015-07-28 | Varian Medical Systems International Ag | Time-resolved pre-treatment portal dosimetry systems, devices, and methods |
| FR3021225B1 (en) * | 2014-05-22 | 2016-07-01 | Scm Oncologie | METHOD OF ESTIMATING THE DOSE DELIVERED BY AN EXTERNAL RADIATION THERAPY SYSTEM |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5295200A (en) * | 1991-01-09 | 1994-03-15 | Board Of Regents, The University Of Texas System | Method and apparatus for determining the alignment of an object |
| CN107041997A (en) * | 2016-02-05 | 2017-08-15 | 瓦里安医疗系统国际股份公司 | Beam of radiation is directed at the system measured with beam of radiation, method and apparatus |
| CN110237445A (en) * | 2019-07-05 | 2019-09-17 | 北京理工大学 | Based on EPID body 3-dimensional dose monitoring and verification method |
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