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The net fractional depth dose: A basis for a unified analytical description of FDD, TAR, TMR, and TPR
Author(s) -
van de Geijn J.,
Fraass B. A.
Publication year - 1984
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 - 10.1118/1.595581
Subject(s) - basis (linear algebra) , mathematics , computer science , physics , geometry
The net fractional depth dose (NFD) is defined as the fractional depth dose (FDD) corrected for inverse square law. Analysis of its behavior as a function of depth, field size, and source–surface distance has led to an analytical description with only seven model parameters related to straightforward physical properties. The determination of the characteristic parameter values requires only seven experimentally determined FDDs. The validity of the description has been tested for beam qualities ranging from 6 0 Co gamma rays to 18‐MV x rays, using published data from several different sources as well as locally measured data sets. The small number of model parameters is attractive for computer or hand‐held calculator applications. The small amount of required measured data is important in view of practical data acquisition for implementation of a computer‐based dose calculation system. The generating function allows easy and accurate generation of FDD, tissue–air ratio, tissue–maximum ratio, and tissue–phantom ratio tables.