阅读说明：本技术 利用多传感器进行三维射束分析仪的ssd精确调整方法 (SSD (solid State disk) accurate adjustment method for three-dimensional beam analyzer by using multiple sensors ) 是由 杨国涛 熊秋锋 龚岚 黄成刚 张秋辰 于 2020-05-23 设计创作，主要内容包括：本发明公开了一种利用多传感器进行三维射束分析仪的SSD精确调整方法,通过三维射束分析仪的扫描支架,并配合液位传感器,获取线阵光敏CCD与三维射束分析仪水面的固有距离；通过线阵光敏CCD,并控制升降平台的升降,获取准确的SSD距离；线阵光敏CCD主要完成对野灯暗线的判断,以及SSD刻度线的判断。本发明有效的避免了人眼观察和估读SSD引起的误差,提高了利用三维射束分析仪对放射治疗设备水中剂量分布检测的准确性。(The invention discloses a method for accurately adjusting SSD of a three-dimensional beam analyzer by utilizing multiple sensors, which comprises the steps of obtaining the inherent distance between a linear array photosensitive CCD and the water surface of the three-dimensional beam analyzer through a scanning bracket of the three-dimensional beam analyzer and by matching with a liquid level sensor; the accurate SSD distance is obtained by linear array photosensitive CCD and controlling the lifting of the lifting platform; the linear array photosensitive CCD mainly completes the judgment of the dark line of the wild lamp and the judgment of the SSD scale mark. The invention effectively avoids the errors caused by human eye observation and SSD estimation, and improves the accuracy of detecting the dose distribution in water of the radiotherapy equipment by using the three-dimensional beam analyzer.)

1. A method for performing SSD fine tuning of a three-dimensional beam analyzer using multiple sensors, comprising the steps of:

step 1: setting a program-controlled lifting platform for lifting the three-dimensional beam analyzer; the distance between the linear array photosensitive CCD and the liquid level sensor in the Z-axis direction of the three-dimensional beam analyzer is a mechanical fixed distance;

step 2: descending the Z axis of the three-dimensional beam analyzer, and stopping when the liquid level sensor reads;

and step 3: turning on a wild lamp of the linear accelerator, moving an X axis and a Y axis of the three-dimensional beam analyzer, and when all or the central part of display pixels of the linear array photosensitive CCD reach the minimum value, indicating that a hidden line AB of the wild lamp is found and superposed;

and 4, step 4: turning off the wild lamp and turning on the distance measuring lamp; the lifting platform is lifted, and when the linear array photoresistors are all displayed to be 255 or more than 128, the lifting is stopped;

and 5: reading a liquid level value a cm displayed by a liquid level sensor; manually reading the scale X cm of the scale mark of the SSD, and inputting a main program;

step 6: the main program judges whether the SSD is larger than that given by the standard, if the SSD is 100cm, X is smaller than 100cm, the main program controls the lifting platform to ascend by (100-X) cm, otherwise, the lifting platform descends by (X-100) cm;

wherein, the main program judging process is as follows:

step 6.1: firstly, reading a liquid level value, judging whether the liquid level value is zero, if so, sending a control instruction to a three-dimensional beam analyzer, and descending a Z axis; if not, judging whether the liquid level exceeds the range, if so, sending a control instruction to the three-dimensional beam analyzer to raise the Z axis, and if not, recording the current liquid level value a cm;

step 6.2: turning on the wild lamp, and moving the linear array photosensitive CCD to the vicinity of the dark line;

step 6.3: reading a pixel value of the linear array photosensitive CCD; judging whether the pixel values are all zero, if not, sending a control command to a three-dimensional beam analyzer, scanning the point on the X axis in a positive direction at a distance of 0.1mm for 20mm, returning to the starting point if the point is not found, and scanning in a negative direction at a distance of 0.1mm for 20 mm; if all the pixels are zero, turning off the wild lamp and turning on the distance measuring lamp;

step 6.4: reading the pixel value of the linear array photosensitive CCD again; judging whether all the pixel values are larger than 127 and not larger than 127, sending a lifting instruction to the lifting platform, and scanning the interval of 0.1 mm; if all the pixel values are larger than 127, manually reading the scale value Xcm and inputting the scale value Xcm into a program;

step 6.5: judging whether the distance is larger than 100 cm; if the distance is larger than 100cm, sending an instruction of descending (X-100) cm to the lifting platform, wherein the distance is 0.1 mm; if the distance is less than 100cm, sending a command of ascending (100-X) cm to the lifting platform, wherein the distance is 0.1 mm;

step 6.6: after the adjustment is finished, sending a command of lifting by 3-a cm to the lifting platform, wherein the distance is 0.1 mm;

and 7: then, the height is raised by (3-a) cm.

Technical Field

The invention relates to the field of adjustment of three-dimensional beam analyzers, in particular to a method for accurately adjusting an SSD (solid State disk) of a three-dimensional beam analyzer by using multiple sensors.

Background

About 392.9 people with malignant tumor in 2015, and about 233.8 people with death account for about 23.91% of all the causes of death. On average, over 1 million people per day were diagnosed with cancer, and 7.5 people per minute were diagnosed with cancer. The cancer burden is in a continuously rising state compared to historical data. Over the last 10 years, the incidence of malignancy has remained on the order of 3.9% and mortality has remained 2.5% per year. According to WHO data, it is shown that about 70% of cancer patients require radiation therapy during the treatment, of which 40% can be cured.

In 2017, the national cancer center issued basic guidelines for radiotherapy quality control, on the basis of which, in 2017, the writing work of 5 special guidelines for radiotherapy issued this time was started, and after two years of review and modification, the guidelines were officially issued externally in this year. The first 5 radiotherapy quality control guidelines issued in China for different radiotherapy technologies and equipment are "quality control guidelines for medical electronic linear accelerators", "quality control and quality assurance for after-loading therapy machines", "quality assurance for helical tomotherapy systems", "quality control guidelines for radiotherapy recording and verification systems", and "practice guidelines for intensity modulated radiotherapy dose verification".

The three-dimensional beam analyzer is also called three-dimensional water tank, and is a large-scale instrument for measuring and analyzing the three-dimensional dose distribution of rays output by a medical electronic linear accelerator (or a 60Co therapeutic machine). The accelerator is a necessary tool for debugging various parameters of the accelerator in the production process of an accelerator manufacturer, and is also a measuring tool for parameters required by a Treatment Planning System (TPS). Data measured by the system is required for both accelerator production and clinical radiation treatment procedures. Therefore, the three-dimensional water tank plays a very important role in guaranteeing the quality of radiotherapy.

According to the specification of jjjg 589-2008 radiation source of medical electron accelerator, the Source Skin Distance (SSD) is the distance from the radiation source of radiotherapy equipment to the skin of a human body. When the underwater dose distribution detection is carried out on the radiotherapy equipment, the underwater dose distribution detection refers to the distance from a radioactive source of the radiotherapy equipment to the water surface in a water tank body of a three-dimensional beam analyzer. In order to perform quality detection on the radiotherapy equipment, various key dose parameters of the radiotherapy equipment must be detected. During the quantity value detection of some key dose parameters of radiotherapy equipment, the SSD needs to be adjusted to ensure that the distance from the water surface of the three-dimensional beam analyzer to the radioactive source is 100cm specified by the regulation.

The adjustment mode that adopts at present is that lift platform cooperation people eye observes, and it just can with the cross dark line coincidence of field to work as 100 cm's SSD scale mark, has the problem: the error of human eye observation is 0.1 mm-0.5 mm. The error of human eye judgment over 0.2mm exceeds the positioning precision requirement of the national standard YYT1538-2017 automatic scanning water model system performance and test method for radiotherapy, and the accuracy of the detection result is seriously influenced. These errors directly affect the PDD (percent depth dose) measurement data, especially the maximum dose point, which is a critical dose parameter, reducing the accuracy of the measurement results and, if ultimately transferred to the patient's treatment, causing risks of underexposure or overdose.

Disclosure of Invention

The invention aims to provide a method for accurately adjusting an SSD of a three-dimensional beam analyzer by using multiple sensors, which reduces the human error when the SSD is confirmed in the process of detecting the water dose distribution of radiotherapy equipment by using the three-dimensional beam analyzer, meets the positioning precision specified in the system performance and test method of an automatic scanning water model for radiotherapy of YYT1538 and 2017, improves the accuracy of the dose distribution detection result and reduces the physical damage to a radiotherapy patient.

In order to solve the problems, the invention adopts the technical scheme that:

a method for performing SSD fine tuning of a three-dimensional beam analyzer using multiple sensors, comprising the steps of:

step 1: setting a program-controlled lifting platform for lifting the three-dimensional beam analyzer; the distance between a linear array photosensitive CCD (charge coupled Device) and a liquid level sensor in the Z-axis direction of a three-dimensional beam analyzer is a mechanical fixed distance;

step 2: descending the Z axis of the three-dimensional beam analyzer, and stopping when the liquid level sensor reads;

and step 3: turning on a wild lamp of the linear accelerator, moving an X axis and a Y axis of the three-dimensional beam analyzer, and when all or the central part of display pixels of the linear array photosensitive CCD reach the minimum value, indicating that a hidden line AB of the wild lamp is found and superposed;

and 4, step 4: turning off the wild lamp and turning on the distance measuring lamp; the lifting platform is lifted, and when the linear array photoresistors are all displayed to be 255 or more than 128, the lifting is stopped;

and 5: reading a liquid level value a cm displayed by a liquid level sensor; manually reading the scale X cm of the scale mark of the SSD, and inputting a main program;

step 6: the main program judges whether the SSD is larger than that given by the standard, if the SSD is 100cm, X is smaller than 100cm, the main program controls the lifting platform to ascend by (100-X) cm, otherwise, the lifting platform descends by (X-100) cm;

wherein, the main program judging process is as follows:

step 6.1: firstly, reading a liquid level value, judging whether the liquid level value is zero, if so, sending a control instruction to a three-dimensional beam analyzer, and descending a Z axis; if not, judging whether the liquid level exceeds the range, if so, sending a control instruction to the three-dimensional beam analyzer to raise the Z axis, and if not, recording the current liquid level value a cm;

step 6.2: turning on the wild lamp, and moving the linear array photosensitive CCD to the vicinity of the dark line;

step 6.3: reading a pixel value of the linear array photosensitive CCD; judging whether the pixel values are all zero, if not, sending a control command to a three-dimensional beam analyzer, scanning the point on the X axis in a positive direction at a distance of 0.1mm for 20mm, returning to the starting point if the point is not found, and scanning in a negative direction at a distance of 0.1mm for 20 mm; if all the pixels are zero, turning off the wild lamp and turning on the distance measuring lamp;

step 6.4: reading the pixel value of the linear array photosensitive CCD again; judging whether all the pixel values are larger than 127 and not larger than 127, sending a lifting instruction to the lifting platform, and scanning the interval of 0.1 mm; if all the pixel values are larger than 127, manually reading the scale value Xcm and inputting the scale value Xcm into a program;

step 6.5: judging whether the distance is larger than 100 cm; if the distance is larger than 100cm, sending an instruction of descending (X-100) cm to the lifting platform, wherein the distance is 0.1 mm; if the distance is less than 100cm, sending a command of ascending (100-X) cm to the lifting platform, wherein the distance is 0.1 mm;

step 6.6: after the adjustment is finished, sending a command of lifting by 3-a cm to the lifting platform, wherein the distance is 0.1 mm;

and 7: then, the height is raised by (3-a) cm.

Compared with the prior art, the invention has the beneficial effects that: errors caused by SSD observation and estimation reading of human eyes are effectively avoided, and the accuracy of detecting the dose distribution in water of the radiotherapy equipment by using the three-dimensional beam analyzer is improved.

Drawings

Fig. 1 is a schematic view of a medical linear accelerator using a three-dimensional beam analyzer for inspection.

Fig. 2 is SSD scale lines.

Figure 3 is a linear accelerator wild light feature.

FIG. 4 is a schematic view of a sensor clamp.

Fig. 5 is an SSD auto-alignment operation flow.

Fig. 6 is a SSD adjustment main program.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. The invention aims to solve the problem of SSD human error in the process of detecting the dose distribution of radiotherapy equipment by using a three-dimensional beam analyzer, the SSD scale mark of the three-dimensional beam analyzer is identified by using a linear array photosensitive CCD, and then a lifting platform is controlled to finish the precise adjustment of the SSD. The invention is mainly divided into two parts: and identifying and controlling the lifting platform by the SSD scale marks.

Accurately adjusting the SSD scale distance; the scale lines of the SSD are identified by using the linear array photosensitive CCD, the reading of the SSD scale lines is manually input, the stepping motor is controlled according to the distance difference between the reading and the standard SSD, the lifting of the lifting platform is completed, so that the distance between the water surface of the three-dimensional beam analyzer and the radioactive source is adjusted, finally, whether the linear array photosensitive CCD is in place is confirmed, the final error of the SSD is controlled to be +/-0.1 mm, and the positioning precision requirement of YYT1538-2017 automatic scanning water model system performance and test method for radiotherapy is met.

In fig. 1, 1 is a medical linear accelerator, 2 is a radiation source point, 3 is a three-dimensional beam analyzer, 4 is a lifting platform support plate, 5 is a lifting platform lifting column (error 0.1mm), and 6 is a stepping motor. Source Skin Distance (Source Skin Distance: SSD): the distance from the center of the radioactive source to the center of the irradiation field of the body surface skin. When the three-dimensional beam analyzer is used for detecting radiotherapy equipment, for the detection of the medical linear accelerator, the SSD is the distance between a radiation source and the water surface, and the SSD is 100cm according to the JJG589-2008 medical electron accelerator radiation source.

When the ranging lamp of the linear accelerator is turned on, the SSD scale line shown in fig. 2 appears on the water surface, the SSD scale line is lighted, the interval between the SSD scale lines is 1cm from 0cm to 200cm, and the area without the display scale line is a dark area. The field lamp feature of the accelerator is shown in fig. 3, and the field lamp feature has light and shade changes to form a 'tian' shape, the outer ring of the 'tian' shape is a dark area, and the middle of the 'tian' shape is provided with two crossed dark lines and four bright areas. While the cross dark line is the AB, GT axis of the radiotherapy apparatus. During actual measurement, the SSD is adjusted manually, human eyes observe, and when the 100cm scale line of the SSD is overlapped with the dark line in the direction of the wild lamp AB, human errors are introduced in the process.

As shown in fig. 4, 7 is the Y-axis, 8 is the Z-axis, 9 is the X-axis, 10 is the liquid level sensor, and 11 is the line-array photosensitive CCD. The distance between the linear array photosensitive CCD and the liquid level sensor in the Z-axis direction is a mechanical fixed distance of 3 cm. The liquid level sensor adopts a magnetic liquid level sensor to measure the range by 20mm, and the precision is 0.1 mm. A TCD1209D linear array photosensitive CCD is adopted, and the CCD is composed of 2048 photodiodes, and the pixel size is 14 mu m x 14 mu m.

As shown in fig. 5, the operation steps of the present invention are as follows:

1. the Z-axis of the three-dimensional beam analyzer is lowered and stopped when the level sensor has a reading.

2. Turning on the field lamp of the linear accelerator, moving the X and Y axes of the three-dimensional beam analyzer, and when all (or the central part) of the display pixels of the linear array photosensitive CCD reach the minimum value, indicating that the dark line AB of the field lamp is found and is coincided.

3. Turning off the wild lamp and turning on the distance measuring lamp; and (3) lifting the lifting platform, and stopping lifting when the linear array photoresistors are all displayed 255 (or more than 128).

4. Reading a liquid level value a cm displayed by a liquid level sensor; and manually reading the scale mark X cm of the SSD scale mark, and inputting the main program.

5. And the main program judges whether the SSD is larger than that given by the standard, and if the SSD is 100cm and the X is smaller than 100cm, the main program controls the lifting platform to ascend by (100-X) cm, otherwise, the lifting platform descends by (X-100) cm. As shown in fig. 6:

1) firstly, reading a liquid level value, judging whether the liquid level value is zero, if so, sending a control instruction to a three-dimensional beam analyzer, and descending a Z axis; if not, judging whether the liquid level exceeds the range, if so, sending a control instruction to the three-dimensional beam analyzer to raise the Z axis, and if not, recording the current liquid level value a cm;

2) turning on the wild lamp, and moving the linear array photosensitive CCD to the vicinity of the dark line;

3) reading a pixel value of the linear array photosensitive CCD; judging whether the pixel values are all zero, if not, sending a control command to a three-dimensional beam analyzer, scanning the point on the X axis in a positive direction at a distance of 0.1mm for 20mm, returning to the starting point if the point is not found, and scanning in a negative direction at a distance of 0.1mm for 20 mm; if all the pixels are zero, turning off the wild lamp and turning on the distance measuring lamp;

4) reading the pixel value of the linear array photosensitive CCD again; judging whether all the pixel values are larger than 127 and not larger than 127, sending a lifting instruction to the lifting platform, and scanning the interval of 0.1 mm; if all the pixel values are larger than 127, manually reading the scale value Xcm and inputting the scale value Xcm into a program;

5) judging whether the distance is larger than 100 cm; if the distance is larger than 100cm, sending an instruction of descending (X-100) cm to the lifting platform, wherein the distance is 0.1 mm; if the distance is less than 100cm, sending a command of ascending (100-X) cm to the lifting platform, wherein the distance is 0.1 mm;

6) after the adjustment is finished, sending a command of rising by 3-a cm to the lifting platform, wherein the distance is 0.1mm

6. Then, the height rises by (3-a) cm, which is the inherent height of the machine, and the SSD adjustment ends.

The inherent distance between the linear array photosensitive CCD and the water surface of the three-dimensional beam analyzer is obtained through the scanning bracket of the three-dimensional beam analyzer and by matching with the liquid level sensor. And the accurate SSD distance is obtained by linear array photosensitive CCD and controlling the lifting of the lifting platform. The linear array photosensitive CCD mainly completes the judgment of the dark line of the wild lamp and the judgment of the SSD scale mark.