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Verification of positioning accuracy of MLC leaves of 8 medical accelerators in IMRT in Henan province / 中华放射医学与防护杂志
Chinese Journal of Radiological Medicine and Protection ; (12): 137-140, 2019.
Article in Chinese | WPRIM | ID: wpr-734329
ABSTRACT
Objective To measure the positioning accuracy of multi-leaf collimators (MLC) leaves by using radiochromic films,with aim to providing data in support of IAEA's methodology validation.Methods The present study focused on 8 accelerators (Varian,Elekta and Siemens machines) at 6 hospitals in Henan province with highly skilled physicists.The 25 cm × 25 cm radiochromic films were put on 30 cm × 30 cm homogeneous solid phantoms and covered with a 2.0-cm-thick homogeneous solid phantom slabs.The CT-scanned images were transmitted to TPS for plan formulation.With 6 MV X-ray,MLC created 5 strip 3 cm × 0.6 cm picket fence field,each with 3.0 cm strip separation.The SSD was 100 cm at the maximum dose point,with a 250 MU to each strip.The irradiated radiochromic films were returned to IAEA for analysis within one week and compared with the values given by IAEA.Results The difference of film-measured and TPS-planned positions of MLC leaves for each strip picket fence should be within ± 0.5 mm as required by IAEA.For 7 of 8 accelerators selected,the differences of accurately measured MLC leaf positions were all within ±0.5 mm,which were in line with the IAEA requirements,with only other one being beyond-0.5 mm,not consistent with the IAEA requirements.The differences of film-measured actual widths between each pair and all pairs of leaves were within ±0.75 mm as required by IAEA for 7 accelerators,whereas the other one was outside ± 0.75 mm,not consistent with the IAEA requirements.The standard deviation of film-measured actual width of MCL leaf between each pair and all pairs for 7 accelerators were ≤ 0.3 mm as required by IAEA,whereas the other one was 0.5 mm,not consistent with IAEA requirements.Conclusions The MLC positioning accuracy of a few of medical accelerators in Henan is not qualified.It is of great significance to carry out regular quality examination as well as third-party verification to ensure precise delivery of radiotherapy.

Full text: Available Index: WPRIM (Western Pacific) Language: Chinese Journal: Chinese Journal of Radiological Medicine and Protection Year: 2019 Type: Article

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Full text: Available Index: WPRIM (Western Pacific) Language: Chinese Journal: Chinese Journal of Radiological Medicine and Protection Year: 2019 Type: Article