The net fractional depth dose: a basis for a unified analytical description of FDD, TAR, TMR, and TPR.
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 60Co 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.
D003037:Cobalt Radioisotopes / Q000627:therapeutic use; D006801:Humans; D010315:Particle Accelerators; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy; D014894:Weights and Measures
D003037:Cobalt Radioisotopes