Portal dose image (PDI) prediction for dosimetric treatment verification in radiotherapy. I. An algorithm for open beams

A method is presented for calculation of transmission functions for high energy photon beams through patients. These functions are being used in our clinic for prediction of portal dose images (PDIs) which are compared with PDIs measured with an electronic portal imaging device (EPID). The calculati...

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Bibliographic Details
Published inMedical physics (Lancaster) Vol. 25; no. 6; p. 830
Main Authors Pasma, K L, Heijmen, B J, Kroonwijk, M, Visser, A G
Format Journal Article
LanguageEnglish
Published United States 01.06.1998
Subjects
Algorithms
Humans
Neoplasms - radiotherapy
Phantoms, Imaging
Radiometry - instrumentation
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted - statistics & numerical data
Radiotherapy, High-Energy
Scattering, Radiation
Technology, Radiologic
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Summary:A method is presented for calculation of transmission functions for high energy photon beams through patients. These functions are being used in our clinic for prediction of portal dose images (PDIs) which are compared with PDIs measured with an electronic portal imaging device (EPID). The calculations are based on the planning CT-scan of the patient and on the irradiation geometry as determined in the treatment planning process. For each beam quality, the required input data for the algorithm for transmission prediction are derived from a limited number of measured beam data. The method has been tested for a PDI-plane at 160 cm from the focus, in agreement with the fixed focus-to-detector distance of our fluoroscopic EPIDs. For 6, 23 and 25 MV photon beams good agreement (approximately 1%) has been found between calculated and measured transmissions through anthropomorphic phantoms.
ISSN:0094-2405
DOI:10.1118/1.598293