Study of detectors response on the scatter radiation of 6 MV flattening filter free beams

R. D.T. Pratiwi, D. Ryangga, S. A. Pawiro

Research output: Contribution to journalConference articlepeer-review


Small field dosimetry which related to the use of Flattening Filter Free (FFF) beams is a great challenge because of the perturbation effects caused by the size of the detector's active volume or detector's materials. This phenomenon encourages researchers to do a further study about detector response. In this study, scatter and primary radiation from 6 MV FFF photon beams were studied to evaluate the detector response in small fields for a better understanding of the contribution of every phenomenon. Ion chamber and Gafchromic films were used in three measurement configurations representing open field measurement and approximations of both primary and scatter part of the beam, described as follows: (i) detectors positioned under steel block, exposing the detectors only to scatter part of radiation field, (ii) detectors positioned inside mini phantom, approximating the detector response to primary radiation with minimum scatter, (iii) detectors positioned in the standard open field, which was the superposition of the primary and scatter radiation. The results show that detector responses were heavily depended on its design (i.e. active volume) especially in small beams. The detector response in the open field could be reproduced from the blocked and primary beam set-up with a discrepancy ranging from 1.0% to 36%. Moreover, the volume averaging and other phenomenon affecting the detector response could be observed in the blocked beam.

Original languageEnglish
Article number012064
JournalJournal of Physics: Conference Series
Issue number1
Publication statusPublished - 6 Jun 2019
Event18th Asia-Oceania Congress of Medical Physics, AOCMP 2018 and 16th South-East Asia Congress of Medical Physics, SEACOMP 2018 - Bangsar South, Kuala Lumpur, Malaysia
Duration: 11 Nov 201814 Nov 2018


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