A simple equivalent tissue-air ratio method for calculating absorbed dose in a heterogeneous medium.

1 February 1983

journal article
research article
Published by Radiological Society of North America (RSNA) in Radiology

Vol. 146 (2) , 527-529
https://doi.org/10.1148/radiology.146.2.6849101

Abstract

Density correction factors for 60Co .gamma. rays and 8-MV X-rays were measured with an ionization chamber in water-equivalent phantoms containing simulated lung or bone inhomogeneities larger or smaller than the beam (beam sizes, 5 .times. 5 to 30 .times. 30 cm). Measurements were compared with values calculated from the effective SSD [skin-source distance] method, the generalized Batho power law method and a simplified equivalent tissue-air ratio (SETAR) method. The SETAR method may give the best overall agreement with experimental values, while the effective SSD and Batho algorithms are accurate only in certain situations. The SETAR method seems adequate for most clinical applications.

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