Abstract
Dosimetric comparison of extended dose range film with ionization measurements in water and lung equivalent heterogeneous media exposed to megavoltage photons
Highlights
The acquisition of accurate measured dosimetry data in inhomogeneous conditions is fundamental in evaluating the perturbative effect of inhomogeneities and in verifying or validating robust calculational algorithms
The variations with depth were in the order of 2– 4 % for the 25ϫ25 cm2 field for both energies; the highest difference 4.5% was reached at depth of 15 cm for the 6 MV beam for this field size
Film dosimetry is in general a convenient method to generate one- and two-dimensional dose distributions
Summary
The acquisition of accurate measured dosimetry data in inhomogeneous conditions is fundamental in evaluating the perturbative effect of inhomogeneities and in verifying or validating robust calculational algorithms. Many investigators have shown the existence of significant dose perturbation within, and beyond, low-density inhomogeneities for small fields of megavoltage photons.. The perturbations in lung result from the combined effects of a reduction in photon attenuation, loss of scattered photons, and increase in range of the secondary electrons. The magnitude of these perturbations depends on the extent and density of the inhomogeneity, the beam energy, field size, and depth.. The magnitude of these perturbations depends on the extent and density of the inhomogeneity, the beam energy, field size, and depth. Various authors have investigated the accuracy with which calculation models can predict measured dose in lung equivalent material. As physically realistic analytical approaches become more practical for dose calculation, e.g., Monte Carlo, and convolution/superposition, there is a need for reliable dose assessment to validate them in various media densities
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