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SU‐E‐T‐718: Surface Dose and Build‐Up Dose Comparison of 6MV and 10MV Flattened with 6MV FFF and 10MV FFF Photon Beams with Different Detectors
Author(s) -
Nambiraj Arunai,
Sigamani Ashokkumar,
Kaviarasu K,
Rajesh T,
Karthikeyan S,
Subramanian Narayanan,
Meerza Kazem
Publication year - 2015
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4925082
Subject(s) - physics , detector , linear particle accelerator , imaging phantom , photon , beam (structure) , optics , materials science
Purpose: To compare measured surface dose and build‐up dose for 6MV and 10MV flattened(FB) with 6MV FFF and 10MV FFF photon beams with different detectors Methods: The surface dose for flattened and FFF photon beams from a Varian True beam medical linear accelerator were measured for square field sizes of 5Χ5 to 30Χ30 cm 2 using Scanditronix NACP ion chamber, CC 13, and Stereotactic field Detectors (SFD) along the central axis of the beam at 100 cm source to surface distance with IBA blue phantom and solid phantom Results: The consistency between the measured percentage depth dose data from all three detector types were observed for depths beyond the depth of the maximum dose, but were all clearly different from each other data in the build‐up region this is observed for both 6 and 10 MV flattened and FFF photon beams. The measured percentage surface doses obtained using the NACP parallel plate chamber, CC 13 and SFD without any correction factor values are varies from 0.322 to 0.519 and 0.524 to 0.709 and 0.370 to 0.585 for 6MV FB and 0.434 to 0.564 and 0.616 to 0.724 and 0.510 to 0.665 for 6MV FFF respectively for field sizes of 5Χ5 to 30Χ30 cm2 for the 6MV FB photon beams and 0.166 to 0.415 and 0.335 to 0.602 and 0.321 to 0.565 for 10MV FB and 0.268 to 0.473 and 0.406 to 0.550 and 0.372 to 0.523 for the 10MV FFF photon beams Conclusion: The measured surface dose clearly increases with increasing field size, regardless of the detector used in the measurement for both 6MV and 10MV flattened and FFF photon beams. Compare to NACP parallel plate chamber CC13 chamber is showing over response and SFD is showing lesser surface dose. Removal of flattening filter increases the surface dose irrespective of beam energy