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The water‐equivalence of phantom materials for 90 Sr – 90 Y beta particles
Author(s) -
Buckley Lesley A.,
Thomadsen Bruce R.,
DeWerd Larry A.
Publication year - 2001
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 - 10.1118/1.1376176
Subject(s) - imaging phantom , polystyrene , dosimeter , materials science , dosimetry , brachytherapy , water equivalent , dose profile , optics , nuclear medicine , composite material , polymer , physics , radiation therapy , meteorology , snow , medicine
Intravascular brachytherapy requires that the dose be specified within millimeters of the source. High dose gradients near brachytherapy sources require that the source‐detector distance be accurately known for dosimetry purposes. Solid phantoms can be designed to accommodate these stringent requirements. This study reports dosimeter readings from90Sr – 90 Y sources measured in water, A150, polystyrene and in an epoxy‐based water‐equivalent plastic. Measurements showed that while A150 and the epoxy‐based plastic agreed well with water when the surface of the source contacted the detector housing, the relative response in the phantoms decreased with increasing depth in phantom, falling to ∼0.55 those of water at a depth of 5 mm. Readings in polystyrene were within 4% of those in water between 1 and 2 mm depth. However, while polystyrene followed water more closely than the other two materials, at greater depths the relative response in polystyrene to water varied from 0.65 to 1.34. When the density of the materials is accounted for, the relative response in A150 is nearly constant with increasing areal density. Furthermore, the response in A150 shows the closest agreement with that in water of any of the solid materials for higher areal densities. For values below 0.3g / cm 2 , polystyrene shows the closest agreement with water.