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SU‐E‐T‐322: The Effects of Microsphere and Surrounding Material Composition on Y‐90 Dose Kernels
Author(s) -
Paxton A,
Davis S,
DeWerd L
Publication year - 2011
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 - 10.1118/1.3612276
Subject(s) - microsphere , glass microsphere , monte carlo method , dosimetry , materials science , range (aeronautics) , computational physics , nuclear medicine , physics , mathematics , composite material , statistics , medicine , chemical engineering , engineering
Purpose: To investigate the effects of microsphere and surrounding material composition on Y‐90 dose kernels. Methods: Dose kernels can be convolved with activity concentrations to calculate non‐uniform dose distributions for patient‐specific dosimetry of Y‐90 microsphere treatments. Monte Carlo simulations were completed with EGSnrc user code EDKnrc to calculate the dose rate at multiple radial distances around various Y‐90 microsphere sources. Glass and resin microsphere simulations were completed with average diameter and density values as well as maximum values based on those given in literature. Both water and liver (as defined in ICRU44, density of 1.06g/cm̂3) were used as the surrounding/scoring material. Point source simulations in water were compared to ICRU72 reference data to validate the simulations. Point source simulations were also completed in water with a density of 1.06g/cm̂3 to evaluate the effects of the density of the surrounding material. All simulations had statistical uncertainties less than 1%.Results: Point source simulations agree to within 2% of the ICRU72 reference data over the range investigated. Glass and resin microsphere simulations in water show a slight decrease in dose rate relative to ICRU72 near the maximum range of Y‐90. The maximum differences were −3.1% and −1.9%, respectively. Simulations in liver show large differences relative to ICRU72, approaching 60% near the maximum range of Y‐90. However, this deviation can be mostly attributed to the difference in density between water and liver Conclusions: The presence of microsphere material causes slight differences in the dose kernel near the maximum range of Y‐90. Large differences were seen in simulations in liver relative to those in water. This is mostly attributed to differences in density of the materials. For accurate patient‐specific dosimetry, it would be necessary to take these differences into account in the calculation of delivered dose.