1.Methods of verification and measurement of MLC-defined small field output factors for eight medical accelerators in Henan province
Xiaojun CHENG ; Chuanpeng HU ; Chenzhi JIA ; Suming LUO ; Hao WU
Chinese Journal of Radiological Medicine and Protection 2015;35(10):780-783
Objective To investigate muli-leaf collimator (MLC)-defined small field output factors calculated by the treatment planning system (TPS), and to study the measuring method of small field output factors verified by 0.015 cc PinPoint ionization chamber.Methods Eight medical accelerators for intensity-modulated radiation therapy (IMRT) were investigated in Henan province, and TPS-calculated output factors for various small fields (6 cm ×6 cm,4 cm ×4 cm,3 cm ×3 cm and 2 cm ×2 cm) were compared with published values recommended by IAEA.If the relative deviation was more than ± 3% for the 2 cm ×2 cm field size and ±2% for the fields of 6 cm ×6 cm, 4 cm ×4 cm and 3 cm ×3 cm, which was beyond the scope of IAEA allowed, the output factors will be measured and verified using 0.015 cc PinPoint ionization chamber and Unidos electrometer.Results TPS-calculated small field output factors for eight medical accelerators were compared with published values.The relative deviation of small field output factors for five pieces of equipment, which accounted for 62.5% of the total, met the IAEA's requirement, while the other three, which accounted for 37.5% of the total, did not.After measuring with PinPoint ionization chamber, the results from only three pieces of equipment met minimum IAEA's requirement.Conclusions MLC-defined small field output factors calculated by TPS for some medical accelerators in Henan need to be measured and corrected using micro-ionization chamber, and the measured values could be taken as the basis of radiation treatment planning.
2.TLD-based quality audit for radiotherapy dosimetry under reference and non-reference condition in Henan province
Xiaojun CHENG ; Chuanpeng HU ; Hongbing QIAO ; Kunjie WEI ; Suming LUO ; Zhijian HE
Chinese Journal of Radiological Medicine and Protection 2014;34(6):446-450
Objective To verify the reliability of radiotherapy dosimetric parameters in reference and non-reference conditions using thermoluminescent dosimeters (TLDs).Methods Using the established TLD method,the dose variations with different radiation field sizes and 45 ° wedge plate were verified for 10 photon beams of 6 MV,together with dosimetric parameters at the point of maximum axial dose for 4 electron beams of 9 MeV under reference and non-reference conditions.Comparisons were made between TLD results and finger ionization chamber results.Results The average relative deviation,for 6 MV photon beams,between TLD results and finger ionization chamber measurements was 4.7%,within ± 7% as required by the IAEA.The average relative deviation,for 9 MeV electron beam,between TLD results and plane parallel ionization chamber measurements was 2.4 %,not beyond ± 5% permitted by IAEA.Conclusions Using TLD method to verify the radiotherapy dosimetric parameters in reference and non-reference conditions was reliable,simple and feasible.
3.Comparison of gamma knife validation film's analysis results of different film dose analysis software
Xiaojun CHENG ; Conghua ZHANG ; Han LIU ; Fuyou DAI ; Chuanpeng HU ; Cheng LIU ; Zhongfu YAO
Chinese Journal of Radiological Medicine and Protection 2011;31(1):71-75
Objective To compare the analytical result of different kinds of film dose analysis software for the same gamma knife,analyze the reasons of difference caused,and explore the measurements and means for quality control and quality assurance during testing gamma knife and analyzing its result.Methods To test the Moon Deity gamma knife with Kodak EDR2 film and γ-Star gamma knife with GAFCHROMIC(R) EBT film,respectively.All the validation films are scanned to proper imagine format for dose analysis software by EPSON PERFECTION V750 PRO scanner.Then imagines of Moon Deity gamma knife are analyzed with Robot Knife Adjuvant 1.09 and Fas-09 1.0,and imagines of γ-Star gamma knife with Fas-09 and MATLAB 7.0.Results There is no significant difference in the maximum deviation of radiation field size ( Full Width at Half Maximum,FWHM) and its nominal value between Robot Knife Adjuvant and Fas-09 for Moon Deity gamma knife (t = -2.133,P >0.05).The analysis on the radiation field' s penumbra region width of collimators which have different sizes indicated that the differences are significant (t = - 8.154,P < 0.05 ).There is no significant difference in the maximum deviation of FWHM and its nominal value between Fas-09 and MATLAB for γ-Star gamma knife ( t = - 1.384,P >0.05 ).However,following national standards,analysis of φ4 mm width of collimators can obtain different results according to the two kinds software,and the result of Fas-09 is not qualified while MATLAB is qualified.The analysis on the radiation field' s penumbra region width of collimators which have different sizes indicates that the differences are significant ( t = 3.074,P < 0.05 ).The imagines are processed with Fas-09.The analysis of imagine in the pre-and the post-processing indicates that there is no significant difference in the maximum deviation of FWHM and its nominal value ( t = 0.647,P > 0.05 ),and the analytical result of the radiation field' s penumbra region width indicates that there is no significant difference as well ( t = -0.627,P > 0.05 ).Conclusion The study shows that different kinds of film dose analysis software may have some differences in analysis of the same gamma knife validation film,and the results may lead to the different decisions in accordance with national standard.
4.The image noise effect on the results of Gamma knife dosimetry parameters test.
Xiaojun CHENG ; Conghua ZHANG ; Chuanpeng HU ; Fuyou DAI ; Kunjie WEI ; Caifang CHU
Journal of Biomedical Engineering 2012;29(6):1089-1093
In order to analyze the image noise effect on the results of Gamma knife dosimetry parameter test, we tested the dosimetry parameters of the Gamma knives according to GBZ 168-2005. Radiological protection standards of X (gamma)-ray stereotactic radiosurgery for head treatment. Dose analysis software was applied to examine the testing film before and after image denoising, and SPSS 11.0 software was used for statistical analysis. The results showed that there was a significant difference in the results of the maximum deviation between radiation field size and its nominal value (t = 7.600, P < 0.01) and the radiation field's penumbra region width of collimators also had significantly different sizes (t = 5.334, P < 0.01) before and after image denoising. This study indicated that the image noise could influence the results of testing Gamma knife dosimetry parameters, so as to cause deviations.
Algorithms
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Artifacts
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Gamma Rays
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Head
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surgery
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Humans
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Radiometry
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instrumentation
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Radiosurgery
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instrumentation
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Radiotherapy Planning, Computer-Assisted
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methods
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Stereotaxic Techniques
5.Survey on the awareness and application of radiation shielding specifications for γ-ray radiotherapy room
Chenzhi JIA ; Chuanpeng HU ; Xiaojun CHENG ; Yongzhong MA ; Xiang DU ; Zechen FENG ; Zipo ZHAI ; Wei LI ; Zhen ZHANG
China Occupational Medicine 2023;50(1):94-98
6. Verification of doses to PTV and OAR and 2D dose distribution in IMRT for 8 accelerators in Henan province
Chuanpeng HU ; Chenzhi JIA ; Kunjie WEI ; Xian XUE ; Zhijian HE ; Suming LUO
Chinese Journal of Radiological Medicine and Protection 2020;40(2):140-144
Objective:
To use TLDs and radiochromic films to verify the prescribed doses to both planned target volume (PTV) and organ at risk (OAR) and the 2D dose distribution in IMRT.
Methods:
Eight accelerators of different models were selected in Henan province. The polystyrene phantom provided by IAEA was scanned using CT scanners and then the scanned images were transmitted to treatment planning system (TPS) for prescribing respectively the doses to PTV and OAR. IMRT was performed with phantom exposed to a 6 MV X-rays. The irradiated TLDs and films were delivered for measurement and estimation at Secondary Standard Dosimetry Laboratory at National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention.
Results:
According to IAEA requirements, the relative deviations of the TLD-measured and TPS-planned values were within ±7.0% for the prescribed doses to PTV and OAR. The measured results for PTV have shown that the relative deviation of TLD-measured and TPS-planned values were within -0.3% to 6.9% for 8 accelerators, all consistent with the IAEA requirements. For OAR, the relative deviations of TLD-measured and TPS-planned were within -7.0% to 0.3% for 6 accelerators, consistent with the requirements, whereas those for other 2 accelerators were within -10.8% to -8.4%, not up to the requirements. IAEA required that, for 2D dose distribution, the pass rate of 3 mm/3% be ≥90%. The measured values for 7 accelerators were from 90.2% to 99.9%, consistent with the requirements, whereas that for another one was 70.0%, not meeting the requirement.
Conclusions
The method to verify, using radiochromic film and TLD, the prescribed doses to PTV and OAR and the pass rate of 2D dose distribution is simple and reliable. It is an important step to implement quality control for IMRT and can provide effective support for medical or third-party service institution to verify clinically prescribed dose.
7.Assessment of Radiation Shielding Requirements in Room of Radiotherapy Installations—Part 1: General Principle (GBZ/T 201.1—2007): A survey of relevant personnel in technical service institutions
Hezheng ZHAI ; Quan WU ; Yunfu YANG ; Wei LI ; Xiaojun CHENG ; Chuanpeng HU ; Hailiang LI ; Zechen FENG ; Ribala HA ; Xiao XU ; Deming LIU ; Chuanwen WANG ; Chunyong YANG
Chinese Journal of Radiological Health 2023;32(5):479-483
Objective :
To evaluate the implementation, application, and problems and suggestions of the Radiation Shield-
ing Requirements in Room of Radiotherapy Installations—Part 1: General Principle (GBZ/T 201.1—2007) through a survey of relevant personnel in radiation health technical service institutions, and to provide a scientific basis for further revision and implementation of this standard.
Methods:
A questionnaire survey was conducted among randomly selected per-
sonnel in radiation health technical services across China, which mainly investigated the awareness, training, application, and
revision suggestions related to the GBZ/T 201.1—2007. The results were aggregated and analyzed.
Results:
A total of 184 evaluation questionnaires on the GBZ/T 201.1—2007 were collected from technical service staff in 25 provinces. Among the
responders, 64.1% thought that the standard had been widely applied; 91.8% thought that the standard could meet work
needs; only 54.3% ever received relevant training on the standard; 68.5% used the standard once or more per year; 33.7% thought that the standard needed to be revised.
Conclusion
The personnel in radiation health technical services have a high
awareness rate of the GBZ/T 201.1—2007 and its contents, but their familiarity with and application of the standard need to
be improved. Relevant departments should strengthen the training and promotion of the standard, and part of the standard should be revised.
8.Analysis of tracking evaluation results of Radiation Shielding Specification for Radiotherapy Room, Part 3: Radiotherapy Room of γ-Ray Sources (GBZ/T 201.3—2014): Relevant personnel in medical institutions
Xiang DU ; Chuanpeng HU ; Jin WANG ; Yongzhong MA ; Xiaosan XU ; Chunyong YANG ; Zechen FENG ; Hailiang LI ; Jianli WANG ; Hezheng ZHAI
Chinese Journal of Radiological Health 2023;32(5):489-494
Objective To investigate the awareness, implementation, and application of the Radiation Shielding Specification for Radiotherapy Room, Part 3: Radiotherapy Room of γ-Ray Sources (GBZ/T201.3—2014) by medical institution personnel, to collect problems and recommendations, and to provide a scientific basis for further amendments and implementation of the standard. Methods A questionnaire survey about the awareness, training and application situation and the modification advices of the standard was conducted among practitioners engaged in the production, use, and machine room design related to γ-ray source radiotherapy equipment (collectively referred to as medical institution personnel) in 12 provinces and direct-administered municipalities in China. The questionnaires were collected and a special Excel database was set up for statistical analysis using SPSS 22.0. Results A total of 126 practitioners responded and completed the questionnaire. Approximately 75.4% of respondents indicated that they either “understood” or “understood well” the standard; 42.86% received relevant training; 45.24% and 54.76% indicated that the standard “met” or “basically met” the requirements of detection of γ-ray radiotherapy equipment shielding or design of shielding room. The standard was highly evaluated for suitability. However, the awareness of the standard was inadequate, the rate of training participation was low, and its practical application was limited. Conclusion The standard generally aligns with the requirements for shielding room design in γ-ray radiotherapy. Some revisions should be done according to the current situation of γ-ray radiotherapy.