A field size specific backscatter correction algorithm for accurate EPID dosimetry

Medical Physics
Sean L BerryCheng-Shie Wuu

Abstract

Portal dose images acquired with an amorphous silicon electronic portal imaging device (EPID) suffer from artifacts related to backscattered radiation. The backscatter signal varies as a function of field size (FS) and location on the EPID. Most current portal dosimetry algorithms fail to account for the FS dependence. The ramifications of this omission are investigated and solutions for correcting the measured dose images for FS specific backscatter are proposed. A series of open field dose images were obtained for field sizes ranging from 2 x 2 to 30 x 40 cm2. Each image was analyzed to determine the amount of backscatter present. Two methods to account for the relationship between FS and backscatter are offered. These include the use of discrete FS specific correction matrices and the use of a single generalized equation. The efficacy of each approach was tested on the clinical dosimetric images for ten patients, 49 treatment fields. The fields were evaluated to determine whether there was an improvement in the dosimetric result over the commercial vendor's current algorithm. It was found that backscatter manifests itself as an asymmetry in the measured signal primarily in the inplane direction. The maximum error is approxim...Continue Reading

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Citations

May 3, 2013·Medical Physics·Daniel W BaileyMatthew B Podgorsak
Jul 5, 2013·Medical Physics·Brian W King, Peter B Greer
Jan 10, 2012·Medical Physics·Sean L BerryCheng-Shie Wuu
Jun 1, 2014·Medical & Biological Engineering & Computing·Mahsheed SabetPeter B Greer
Nov 6, 2014·Medical Physics·Lalith K KumaraswamyMatthew B Podgorsak
Aug 3, 2012·Medical Dosimetry : Official Journal of the American Association of Medical Dosimetrists·Yen-Cho HuangChen-Yuan Chen
Sep 20, 2011·Medical Dosimetry : Official Journal of the American Association of Medical Dosimetrists·Pejman RowshanfarzadPeter B Greer
Nov 12, 2013·International Journal of Radiation Oncology, Biology, Physics·Sean L BerryCheng-Shie Wuu
Jul 7, 2012·Journal of Applied Clinical Medical Physics·Daniel W BaileyMatthew B Podgorsak
Jun 7, 2017·Technology in Cancer Research & Treatment·Stefano PecaWendy Lani Smith
Jun 7, 2017·Technology in Cancer Research & Treatment·Stefano PecaWendy Lani Smith
Nov 22, 2013·Journal of Applied Clinical Medical Physics·Ann Van EschChristof Baltes
Oct 22, 2010·Physics in Medicine and Biology·Pejman RowshanfarzadPeter B Greer
Dec 9, 2016·Journal of Applied Clinical Medical Physics·Narges MiriPeter Greer
May 19, 2011·Journal of Applied Clinical Medical Physics·Indra J DasPeter A S Johnstone

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