Review the research progress of electronic irradiation field imaging device in dose verification Yang Yong Dai Jianrong Hu Yimin as a new radiotherapy auxiliary device. At present, it is mainly used to verify the position of patients before or during treatment. By comparing the image of the irradiation field with the digital reconstruction image generated by the simulation positioning film or the treatment planning system. Verify the geometric accuracy of the radiation field settings when the patient is positioned. With the application of intensity-modulated conformal radiation therapy in clinic, the intensity distribution of intensity-modulated radiation field generated by the reverse treatment plan and the distribution of the patient's body and scene are verified. And real-time monitoring of the dose during treatment becomes extremely important. Currently. The methods used to achieve this goal are mainly film measurement semiconductor measurement and thermoluminescence measurement. These methods have their disadvantages. Can not meet the requirements of intensity modulated conformal radiation therapy. Although the design of 1 is mainly to verify the geometric position of the patient's treatment irradiation field, but. As a fast dimensional dose measurement system IIM1 Ding to obtain a large amount of radiation field dose information in a short time, in the intensity-modulated radiation field to verify the design of the automatic compensator and its thickness inspection. Real-time patient dose is similar to 1 and monitoring; it has wide application prospects. In recent years. Many scholars have done a lot of theoretical and experimental research in this area, and research work in this area has become a research hotspot of conformal radiation therapy. This article will focus on the application of 10 in the field of accelerator irradiation field quality control and patient dose verification. The structure and dosimetry characteristics of a volume 1 are currently commonly used. According to the different methods of radiation detection, they are mainly divided into fluorescent light. Three types of solid detector and liquid ionization chamber. The following mainly introduces the structure and dosimetry characteristics of scanning liquid ionization chamber type 3001. For other types, the structure of 5 can refer to literature 1 such as 0 to find 3, which is mainly composed of 3 parts like the central screwing and display system of the wiper system. Rack cross arm. The probe system includes an array of 256 to 256 liquid ionization chambers. The array of ionization chambers is made up of layers and a thick liquid substance. As ionizing mass. The liquid medium body is printed by two pieces, and the ionization curtain array formed by the central pole has. 1.1 Detection area. Knowing that the distance from 1 to 3 is 1.271 Li and 1.271 Li. In front of the Ji 1 Tun Li array, there is a yip, and the stainless steel as an electronically balanced built material is equivalent to the thickness of water. The central control and display system consists of a computer and corresponding software located outside the treatment room for observation and processing of images. The frame support arm fixes the probe system on the accelerator frame. Can make the probe system retractable. The probe array can be moved along the central axis of the irradiation field within a fixed range. When collecting image signals. Yang Yong, Department of Radiation Therapy, Bridge Hospital, Chinese Academy of Medical Sciences, Chinese Union Medical University, swollen ionization chamber array was scanned progressively. Polarization voltage 300 is applied to each row of ionization chambers in sequence. And measure the ionization current collected on each electrode.

Thereby forming an image of 256,256 thrillins. The payment to the company usually has 2 sampling modes. Namely standard mode and quick mode. When using standard sampling mode. All 256-line ionization chambers are sequentially gated by high voltage.

Can get the highest resolution. But the collection time is longer 5.98. When using the fast sampling mode, the interleaved 128-line ionization chamber is simultaneously gated by high voltage. The acquisition time is shorter by 1.58, but the resolution is reduced.

The main purpose of the 10 system scale is to correct ① artifacts generated when the high voltage is switched ② background readings of the electrometer caused by the sensitivity of each ionization chamber unit; the correlation of the frame angle. The reason for the difference in sensitivity of each ionization chamber unit is mainly the difference in electrode shape. The unevenness of the electrode surface and the difference in the local thickness of the liquid medium in the ionization chamber 1 The main steps of the system calibration are as follows 6,7, determine the image and sampling mode ②Choose the appropriate detector position usually at the source detector from the irradiation field to ensure 10 The entire sensitive detection area of ​​325, 325, within the range of the irradiation field, the background image of the collection group when 10 accelerators do not emit beam; 6 like. It is used to measure the sensitivity of each ionization chamber unit. The two sets of images are averaged to obtain two scale images, one is the background image without radiation, and the other is the image obtained by the panfield bed. The image is corrected and calculated. The pixel values ​​in the image output file are the data after removing the influence of background scattering and corrected for the difference in sensitivity of each pixel unit. The panning image 1.1 is used in the calibration method described above; 1.1 The Zuo brother who corrected the sensitivity of each ionization chamber unit is called the image calibration mode. For high-energy photons. Due to the structure of the accelerator equalizer. The dose distribution of the panfield will appear uplift near the edge of the irradiation field, resulting in a difference in the intensity distribution of about 35% in the sensitive measurement range of the probe, which affects the scale of images in different areas. Therefore, in order to accurately measure the dose. The influence of this factor must be considered. There are two main solutions. According to the size of the photon energy, a fixed thickness of 610 nanometers is added to the incident surface of the probe, and the solid water is uniform to the irradiation field. In this way, the dose distribution in the sensitive detection range is clever. The average hook can be up to 1., 1.51. Another method is to use the dimensional dose distribution measured by the dimensional water tank to make point-by-point correction of the unevenness of the dose in the panfield 18. Calibration method for the correction of the unevenness of the dose distribution in the irradiation field Called the dose scale mode to measure the dose. but. To measure the absolute dose, you must also determine the relationship between the pixel value of the irradiation field image and the irradiation dose rate after the system scale. This relationship is characterized by the characteristic curve. 168. The main factors affecting the characteristic curve are the sampling mode, which is because Different sampling modes have different effective signal magnification and photon energy. After considering the influence of the thickness of the built-up area, the light energy will be affected by the characteristic curve. ③ Due to the non-rigidity of the liquid ionizing material, the measurement results of the frame angle are set. There is a certain effect when 1 is used for dose measurement. The effect of this effect must be considered; different accelerator pulse repetition frequency settings have different characteristic curves, and the type 1 Dan characteristic curve is basically independent of the size of the irradiation field. The long-term stability of only 0 is 3 months. 1.3. The relationship between the pixel value and the irradiation dose rate is non-linear, and the following square root function can be used to fit the pixel value of the pixel, which is the dose rate of the corresponding point; The coefficient obtained by fitting the data. There are also other authors who use different forms of functions to fit the characteristic curve. Although the function form is not aggressive, the results obtained are very close. The deviation between the fitted value and the measured value is within 1, and the measurement of the radiation field dose and the cross-sectional distribution of the radiation field dose is performed after the system scale and characteristic curve measurement. It can be used to measure the dose and cross-sectional distribution of the radiation field at the position of the detector when there is a phantom or attenuation material in the radiation field. The data obtained is the transmitted dose trananission lose of the object. Most applications in inverse dosimetry are inseparable from the measurement of the field dose. The second class used only 0 to measure the radiation of the 6th concubine's ray, hitting 0 = 138.5, the isocenter irradiation field is 23, and the dose cross-sectional distribution of the 23rd center row 129th row. And compared with the dimension of the water tank 1.5 under the same conditions 1.5. Except for large deviations in dose drops. 1; et al. 17 used the tax and dose modes at the = 150 collision site to measure the dose cross-sectional distribution of flat and wedge-shaped fields with different irradiation field sizes of 6% and 8 cubits, respectively. And the results are measured with a balance cap; 35.10, off-axis. In other taxes, the deviation is as high as 12. In the study of 3 melons and so on. Under the 1.5, 1 quantity of water, the backscatter contribution is not included. , Etc. 171 The results measured in the air with the ionization chamber did not include side scattering, while the results included side scattering. Private, etc. studied the influence of the above factors on the measurement of the radiation field dose, and used the deconvolution method to correct the side scattering in the 0 result. The deviation from the measurement result of the ionization chamber in the air is 0.5, regardless of whether the uniform or non-uniform phantom is corrected by deconvolution in the entire measurement range. 0 The deviation of the off-axis ratio measured from the deviation of the off-axis ratio measured in air 2.

These studies show that Type 8 has high measurement accuracy.

2in1 Quick tool for the application of accelerator field quality control; verification of intensity distribution of intensity modulated radiation field; design of compensator and verification of thickness distribution, shape. 1 certificate etc. , Equal size. Uranium water tanks were used to measure penumbra of irradiation fields of different shapes and sizes. Since the spatial resolution of only 0 is higher than the ionization chamber, so. The measurement result of 0 is more accurate than that of the ionization chamber. Fluorescent button 10 measured the flatness and uniformity of the irradiation field with fluorescent type 10. And compared with the measurement results of the water tank, the deviation is 1.5 hours. They also add 3 to the multi-leaf collimator 1 and 1 cent to 1.

The reproducibility of the suppression field setting was studied, and the 1 image was used to measure the intensity change of the sunny field edge 1. With a step size of 1, the dose contour of the shadow area of ​​Dong 1 is measured, and the point with the largest gradient change in the curve is obtained by interpolation as the boundary point of the irradiation field. This method is used to determine the accuracy of the setting, and the measurement is repeated more than 20 times. Available, set complex viscosity.

2 Verification of the intensity distribution of the intensity-modulated irradiation field The methods currently used to verify the intensity distribution of the intensity-modulated irradiation field mainly include film semiconductor thermoluminescence and colloidal measurement. These methods have their own shortcomings as a dimensional dose verification tool, which can be quickly and conveniently obtained. Dose distribution information. Therefore, it can be used to verify the intensity distribution of the intensity-modulated field. 1 to wait 5 to use the scanning liquid ionization chamber type Jiang 1 to verify the intensity of the static intensity modulation field; according to the principle of static intensity modulation, each irradiation field consists of several subfields corresponding to each subfield irradiation.

Collect the image like this, for an intensity-modulated irradiation field with a subfield.

Get 10 images of the number of groups. For the dose at the location in the irradiation field. The formula 1 is called to calculate the dosage rate of prime 1 through special sigmoid curve. The position is 1 if it is the exposure of the first person field, the unit is muscle. 1 also 1 leg 1 etc. 5 were measured for a complex intensity-modulated field with 88 subfields and an intensity-modulated field with 18 subfields. The results are compared with the semiconductor array measurement results and the maintenance treatment system calculation results. Except in areas where the dose drops significantly.

Compensator design and thickness distribution verification The compensator is used to compensate for tissue unevenness and tissue defects in conventional radiation therapy. Physical intensity modulation can also be used to achieve intensity-modulated conformal radiation therapy. Jiang has many advantages in dose measurement and verification, which can be easily used for compensator design and verification. 79. etc. 7 developed a technique for automatically designing compensators. And this technology is used to design compensator to correct lung unevenness. The principle is to first determine the characteristic curve of the compensator under a certain energy. The so-called characteristic curve of the compensator refers to the relationship between the thickness of the compensator and the pixel value of the electron irradiation field image measured by Qiao 0, and then use the compensation target to determine the thickness of the compensator. The specific algorithm of the distribution can be referred to in articles 17, 20, etc. In this method, the design includes the lung and mediastinum irradiation field to determine the thickness of the mediastinal area and lung area, when the radiation field is irradiated in the future. Each field is compensated with half of the calculated compensation thickness to obtain a uniform mid-plane dose distribution. The method was tested with a human model. And verified by thermoluminescence measurement. The results showed that the non-uniformity of the radiation dose of the single front field decreased from 16.0 before using the compensator to 0.6 after use; Dose distribution. Compare with the result of 0 measurement. Three kinds of phantoms were used for verification, and the results were obvious in the center of the irradiation field. For a uniform phantom, the calculation results deviate from the Dan 0 measurement result by 1 .; yes; 1 post 01 body 2 using the back projection algorithm. Calculate the outgoing dose and mid-plane dose, and perform dose verification. Outgoing dose is defined as the dose at the maximum dose depth within the exit surface of the phantom. The median household dose is defined as a retreat center. The measured transmission dose of Li 191 and other 191 at the surface was calculated by using the inverse ratio of 1 to calculate the emitted dose. And compare with the semiconductor measurement results. It was found that the deviation of the person increased as the distance from the exit surface of the phantom to the detector increased. When the large phantom deviation reaches 8. This is in agreement with the results of Qing 1 et al. 12 and 01 .; 0 et al. 4 measured with film. In clinical practice, in order to avoid, 3 collides with the treatment bed. At the same time, in order to improve the magnification of the image of the irradiation field and how to divide the image, it is often relied on the larger Yang Sang 401. Therefore.

It is necessary to adopt a more accurate method applicable to the clinic to convert the transmitted dose into the radiation dose. Numerous Yanjiu illuminates with volume-distributed compensators. The thickness distribution of the compensator is verified by comparing 10 the measured fluence distribution with the calculated fluence distribution. The calculated fluence is divided into the original ray and scattered rays. The original ray is calculated by the convolution of the source integration kernel and the exponential decay function. The scattering part is calculated using the magic cross section. For all test cases. All areas within 1.5 and 1 of the irradiation field boundary. The deviation between the calculation result and the measurement result 3., etc. 9 uses the fluorescent type, and 3 verifies the thickness distribution of the compensator. The basic principle is to measure the size of the part captured under certain energy and the irradiation field, and the intensity of the part under irradiation conditions. Furthermore, the thickness distribution of the compensator is determined, and the thickness distribution is compared with the thickness distribution calculated by the reverse treatment plan or directly obtained by geometric measurement to verify the compensator. Use this method to verify the thickness and error of the compensator. 5. The specific steps of the variable product algorithm of the phase-dose energy for the transmission dose 1 of the photon irradiation field are as follows at the 1 position in clinical use. Measure the transmitted dose of the phantom with m; extract the original ray part from the transmitted dose distribution; reversely reflect the original ray part into the patient to obtain the original ray fluence distribution in the body; the original body ray fluence distribution and dose deposition Integral kernel convolution to find the dose distribution in the body. The first step has been described in detail in the previous section. The following will be discussed separately. â‘  There are many algorithms for extracting the original ray fluence distribution to calculate the transmissive agent. Scattered radiation in the seems to be more commonly used, 2 and so on; the C algorithm proposed by et al. Is similar to the algorithm from Cong et al. Both use an iterative method to extract the original ray fluence distribution. The algorithm is introduced as an example. The transmission dose that reaches only a certain detection element is partially divided by the original ray and scattered rays.

30 Applied research in the verification of patient dose when other conditions remain unchanged but no phantom. The measured dose distribution is as follows, so at present, the applied research in the verification of patient dose is roughly divided into two categories according to its method. The design algorithm calculates the transmitted dose distribution at the detector plane, which is compared with the result of 10 measurements, which is called Positive calculation; the alternative ray pencil beam, the distribution of scattered rays reaching the probe is only related to the ray of the phantom along the ray direction, etc. is derived from the transmitted dose of the scene observation and other information. Therefore, the pencil beam scattering integration kernel can be superimposed to measure the 63.86 mid-plane dose addition; the dimensional dose distribution even in the patient's body. Comparing with the calculation results of the treatment planning system, the so-called back projection calculation.

1 Comparing the forward calculation of the transmitted dose distribution with the measurement results 10 can quickly obtain the transmitted dose distribution of the detector plane. If the planning system can calculate the transmitted dose distribution in the plane of the detector outside the patient. It is possible to compare those; to achieve the purpose of verifying the patient's dose. The research in this area is mainly carried out in 2.2. The basis of their algorithm is to expand the conventional physical school into a kind of 1; loyalty and buckle, including the extended phantom 1 Carlo simulation. Therefore, the measured transmission dose is only used as the original value of the original ray, and iterates 34 and 5. The corpse 3 can be degraded to the original ray. The physical model of the ratio of the scattered rays in the transmitted dose distribution to the original ray dose is 3 feet. The thickness of the mode, and the left 2 are constants. The distance from the isocenter to the common distance from the detector to the detector is the average energy of the ray. Using formula 6 can get the central axis l.liJSPR. For the off-axis position of 33, Qi Can et al. 127 made a detailed, 00 increase. The scattering dose distribution gradually widens and flattens. To, after 0501. The scattered dose distribution in the detection plane can be regarded as a constant. Therefore, for the commonly used range of clinical wind 40, formula 6 can be used to calculate the off-axis position 3. After getting 8. The following formula can be used to calculate 0. Probe T20. In the formula, 5 is the brother said that the transmittance is 7. 51 is passed through 20. The transmittance 57.57 after the plexiglass phantom can be obtained by 5 and 7, OR, and 71.

After calculating the emission dose according to the above method from Equation 9. After the following corrections, you can get Zhongping and the agent Bianfang is inversely proportional to Tong Zhengqiaojiang =, the center is the center; the centripetal is the large dose. E4ftS.iE1 where 7 is the measured phantom transmittance. The correction of the scattering contribution of the mid-plane position and the exit position is different. The back-projected calculated outgoing dose and mid-plane dose have a better and better verification of the accuracy of the treatment planning algorithm and the actual irradiation dose.

The original ray part at the measuring element is only. That is, â‘¡ the back projection of the original ray fluence is to obtain the original ray fluence distribution of the detection plane, and then, if the patient 01 data is known, the original ray fluence in the phantom can be easily obtained by inverse square ratio and exponential attenuation correction The volume distribution of Zuyou, 7, 2 and the calculation formula 26 is the following distance, the geometric distance from the source to the point on the 0 plane; they are energy square, the attenuation factor of the ray in the water is point 2 to the exit surface of the phantom The equivalent path length. For the calculation of the exit dose, it is equal to the maximum dose depth hair.

Calculate the outgoing dose, mid-plane dose and committed dose distribution using 8-calculation phantom dose distribution. The above algorithm needs to know the 01 data of the phantom patient. , Xian 28 established an algorithm that does not require 01 data to calculate the emitted dose and mid-plane dose. In this algorithm, the outgoing dose spread function 0 percus 31 is used to describe the effect of a single pencil beam in the phantom on the scattered dose distribution in the outgoing dose. For the midpoint of the non-uniform phantom, the exit dose is calculated by the following formula 1 Hu Yimin. Irradiation field imaging system. Hu Yimin, editor in chief. Tumor radiophysics.

Beijing Atomic Energy Press, 1999.456471., 10 Yizhong. 7. Righteousness 1 is the point. The doses of the box rays and limb rays emitted at 7 places are on the evening of 7. , Transmittance measured immediately. The entropy reduction coefficient of generation distance 1 in the waterline is a constant of constant dimension. The values ​​of 3 and 72 are determined by analyzing the dependence of the scattered emission dose on the irradiation field. 10 types. Yang Xun is the backscattered dose and poor in the original shot. , 4 coffee on Ding, round 31 blood, blood touch, this Zhong Zhilie Xiannu taught cat Zuo 32 Qing milk. , Plus 20 Hu Yimin. Organization compensation technology. Hu Yimin, editor in chief. Tumor radiophysics. Beijing Atomic Energy Press, 1999.47580.

Date of receipt 19 Office 22 case reports Primary malignant lymphoma of the esophagus Column Zhang Zhi Ceying Yingquan Primary malignant lymphoma of the esophagus is extremely rare. So far, 5 cases have been reported in Chinese and 18 cases in English. Recent undergraduate admissions. Now reported as follows.

Patient female. 46 years old. He was admitted to the hospital in July 1999 for 5 months due to feeding choking, and he was able to enter semi-liquid food upon admission. Outer hospital esophagus, the middle and upper segments of the esophagus are long, thick, and the lumen is narrow. The physical examination was generally in a moderate condition, with shallow lymph nodes throughout the body and a heart. Examinations of lung and spleen were normal. The total number of white blood cells was 7.0, 109 B neutrophils accounted for 0.64. Lymphocytes accounted for 0.28. Eosinophils accounted for 0.03. The upper part of the middle esophagus of the review line was about 7.5. 2. The wall of the tube is stiff, the shape is not regular, there are 7, 41 filling defects in the cavity, and the lumen is narrow. Chest, thread heart. There was no abnormality in the lung mediastinum. Endoscopic examination showed 2,25 from the incisors, a raised mass in the posterior wall of the esophagus, with a ulcer in the center, hard mass, and easy bleeding when touched. The rest of the esophagus. The stomach and the ten fingers are not abnormal.

The biopsy specimen was confirmed by immunohistochemical examination as diffuse esophageal non-Hodgkin's malignant lymphoma, 6-cell type. Moderately malignant. On clinical examination, no other site was invaded and diagnosed as primary malignant lymphoma of esophagus. Radiation therapy + chemotherapy was given. Radiation therapy was performed with continent, radiation, 3 field exposures, 150, 25 times; supraclavicular prevention radiation 4218 times. After the radiation therapy, the esophagus was rechecked, and the swollen ribs and large ribs disappeared. After a week's rest, I was rechecked after adding chemotherapy of 51 new alkaloids. The tumors of the esophagus and the radiograph basically disappeared, and only a small length of 4 lumens narrowed. The tube wall is stiff. The mucosa is still smooth, and the barium agent passes smoothly.

The patient was reexamined in February 2000 with no abnormalities.

Discussion The digestive tract is the predominant site of extranodal lymphoma. Malignant lymphomas that invade the digestive tract account for 1020 of lymphomas, mostly non-Hodgkin lymphoma. Among them, foreign reports of invading the stomach accounted for 4850. The small intestine was second, followed by 3037. The ileocecal part accounted for 1218, and the remaining digestive tract was rare. Foreign scholars counted 7 cases of gastrointestinal infringement. No cases of esophageal invasion. The domestic emperor Dong Bian, the tumor is even rarer in the clinic. Another case was scattered.

So far, 5 cases have been reported in Chinese literature and 18 cases have been reported in English literature. The primary esophageal lymphoma, the esophagus and line show the same as esophageal cancer. When the following signs appear, it should be highly suspected that lymphoma may be 1 esophageal mucosal fold increase Thick; 2 submucosal nodules accompanied by large masses; 3 numerous niches and mucosal ulcers; 4 huge esophageal masses but no changes in esophageal stenosis. Endoscopy is not intentionally great. Straight; 2 although the mucous folds are thick. But the dilatation of the esophagus is still good; the nodular-like structure in the 3 walls. The nodules are connected like a bridge. The surface is smooth; 4 there are no obvious specific indicators for many clinical esophagus, radiographs and endoscopy. Therefore, the diagnosis is mainly confirmed by endoscopic biopsy. Diagnosis of primary gastrointestinal lymphoma must meet the following conditions: 1 superficial lymph nodes are not enlarged; 2 chest, radiographic examination is normal. No mediastinal lymphadenopathy; 3 mainly gastrointestinal lesions. If there are lymph nodes involved. It can only be limited to the lymphatic drainage area of ​​the affected site; 4 white blood cell count classification is normal; 5 no liver or spleen is affected.

Once clinically found that lymphoma invades the esophagus, there is often a stomach. The intestines and other digestive tracts may be invaded. Therefore, a full inspection is necessary. Only all meet the above 5 criteria. And there is no other gastrointestinal tract outside the esophagus. In order to be diagnosed as primary malignant lymphoma of esophagus, there are few cases of this disease. There are many treatment methods. Therefore, statistical analysis is not possible. But 1 advocates taking the technique. 1. Supplemented with postoperative radiation therapy or chemotherapy. After salvation, it depends on the clinical stage of the pathological type and whether radical surgery is performed. Recently, it has been advocated that radiation therapy + chemotherapy has the best effect. There are reports of those who survived 12 and 13 years. There are also authors reporting on primary digestive tract non-Hodgkin's lymphoma in stage 1 and stage. The efficacy of chemotherapy alone is no less than that of radiation therapy + chemotherapy, at least in some pathological types, in short. Primary lymphoma of the esophagus is clinically rare. Because its treatment and prognosis are different from other esophageal tumors. It should be included in the differential diagnosis of esophageal tumors,

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