Verification of dose parameters under reference and non-reference conditions for radiotherapy in Liaoning province / 中华放射医学与防护杂志

Objective To verify the reliability of dose parameters of radiotherapy under reference and non-reference conditions by using TLD.Methods Dose parameters were verified by using TLDs under reference and non-reference conditions,including the maximum dose in axel of 5 electron beams with energy of 9 MeV and the variations of dose by depth,source-skin distance,exposure field and 45° wedge for 10 photon beams with energy of 6 MV in 5 hospitals.Results The average relative deviation of 6 MV photon beam measured between TLDs and finger ionization chambers were 4.45％,within ± 7％ as required by IAEA.The average relative deviation of 9 MeV electron beam measured between TLDs and plane parallel chambers were 2.45％,within ± 5％ was required by IAEA.Conclusions Measuring dosimetric parameters by using TLDs under reference and non-reference conditions was reliable and feasible.

Dosimetric verification for radiotherapy quality audit under reference and non-reference conditions in Jiangsu province / 中华放射医学与防护杂志

Objective To verify the methodology for auditing dosimetric parameters in reference and non-reference conditions with thermoluminescent dosimeters (TLDs).Methods Under reference and non-reference conditions,the established TLD methods were used to observe the absorbed dose variations with depth,SSD,field size and 45 wedges for 10 photon beams at 5 hospitals.Dosimetric parameters,including doses at Dmax points in axis,on 5 electron beams of 9 MeV were measured.The measurement results were compared between the TLDs and plane parallel ionization chambers.Results For 6 MV photon beams,the relative deviation of between finger ionization chamber method and TLD chips was in the range of-1.7％ to 5.4％ under on-axis non-reference conditions,and-6.3％ to-0.6％ under off-axis non-reference conditions,respectively,all within the range of ≤ ± 7％ as required by the IAEA.The relative deviation between plane parallel chamber and TLD method was-2.3％ to 3.7％,within ± 5％ as required by the IAEA.Conclusions It is convenient and feasible to use TLD method for quality audits of dosimetric parameters in radiotherapy.

Verification of dosimetric methodology for auditing radiotherapy quality under non-reference condition in Hubei province / 中华放射医学与防护杂志

Objective To verify the reliability of TLD-based quality audit for radiotherapy dosimetry of medical electron accelerator in non-reference condition by monitoring the dose variations from electron beams with different field sizes and 45° wedge and the dose variations from photon beams with different field sizes and source-skin distance.Methods Both TLDs and finger ionization chambers were placed at a depth of 10 cm in water to measure the absorbed dose from photon beams,and also placed at the depth of maximum dose from electron beams under non-reference condition.TLDs were then mailed to National Institute for Radiological Protection,China CDC for further measurement.Results Among the 70 measuring points for photon beams,58 points showed the results with a relative error less than ± 7.0％ (IAEA's acceptable deviation:± 7.0％) between TLDs and finger ionization chambers measurements,and the percentage of qualified point numbers was 82.8％.After corrected by P,value,62 points were qualified and the percentage was up to 88.6％.All of the measuring points for electron beams,with the total number of 24,presented a relative error within ± 5.0％ (IAEA's acceptable deviation:± 5.0％) between TLDs and finger ioization cylindrical chambers measurements.Conclusions TLD-based quality audit is convenient for determining radiotherapy dosimetric parameters of electron beams in non-reference condition and can improve the accuracy of the measuring parameters in connection with finger chambers.For electron beams of 5 MeV ＜ E0 ＜ 10 MeV,the absorbed dose parameters measured by finger ionization chambers,combined with TLD audit,can help obtain the precise and reliable results.

TLD-based quality audit for radiotherapy dosimetry under reference and non-reference condition in Henan province / 中华放射医学与防护杂志

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.