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A modified power‐law formula for inhomogeneity corrections in beams of high‐energy x rays
Author(s) -
Thomas Simon J.
Publication year - 1991
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 - 10.1118/1.596665
Subject(s) - imaging phantom , cobalt 60 , physics , stopping power , radiation , cobalt , polystyrene , dosimetry , beam (structure) , computational physics , power law , power (physics) , optics , irradiation , materials science , nuclear medicine , nuclear physics , nuclear magnetic resonance , mathematics , medicine , statistics , detector , metallurgy , polymer , quantum mechanics
The Batho power‐law formula is in common use in many treatment planning systems to correct for the presence of lungs and other inhomogeneities. While giving excellent agreement with measurement for Cobalt‐60 radiation, it tends to underestimate the lung correction required for higher energy x rays and is undefined for distances beyond an interface less than the buildup distance. This paper suggests a simple modification that greatly improves the agreement with measured data and gives a continuously defined function at all depths. Measurements have been made in a polystyrene and cork phantom to simulate the effects of lung; data are presented for beams of 8‐MV x rays, 16‐MV x rays, and Cobalt‐60 γ rays.