TY - JOUR ID - 73919 TI - Calculation of Equivalent Square Fields in Radiation Therapy by an Improved Vadash Correction Factor for Collimator Exchange Effects JO - Asian Pacific Journal of Cancer Prevention JA - APJCP LA - en SN - 1513-7368 AU - Tahmasebi Birgani, Mohammad Javad AU - Chegni, Nahid AU - Tahmasbi, Marziyeh AU - Fayazi, Raziye AU - Fatahi Asl, Jafar AU - Behrouz, Mohammad Ali AD - Department of Radiotherapy and Oncology, Golestan Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. AD - Department of Medical Physics, Medical School, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. AD - Department of Radiology Technology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. Y1 - 2018 PY - 2018 VL - 19 IS - 11 SP - 3053 EP - 3057 DO - 10.31557/APJCP.2018.19.11.3053 N2 - Background and objectives: To determine the head scatter factor, a formalism presented by Vadash and Bjärngardhas been employed to assess collimator exchange effects. The aim of this study was to determine the best Vadashcorrection factor (A) by introducing a new method based on the output factor measured in air for different square andrectangular fields. Materials and Methods: A new simple mathematical method based on selection of the best dosimetricdata was proposed to obtain the A value for Vadash to predict the equivalent square field size. Measurements wereperformed with a Farmer c UR - https://journal.waocp.org/article_73919.html L1 - https://journal.waocp.org/article_73919_dcbfcde9191090ae21a5c45c9d5fec35.pdf ER -