Ratio of HETERO/HOMO for a single seed to HETERO/HOMO for a fully loaded ( seeds) 20 mm eye plaque. Note differences below 5 mm where the single seed model overestimates the heterogeneity correction factor. However, the ratio for , which is the ABS-recommended depth for lesion heights , is within .
HETERO/HOMO ratio averaged over seven plaque sizes. For all three radionuclides, dose to inner and outer sclera is reduced in comparison to dose calculated in HOMO water medium. Error bars represent
Dose (Gy) for a 16 mm COMS eye plaque with per seed to deliver . Seed model and heterogeneity correction were as follows: (a) HOMO model 200, (b) HETERO model 200, (c) HOMO model 6711, (d) HETERO model 6711, (e) HOMO model CS-1, and (f) HETERO model CS-1. Note increased penetration due to increased average photon energy.
Radial dose function using the line source approximation for the three seed models and comparison to reference Monte Carlo data.
HETERO central axis dose distributions for 10–22 mm diameter COMS eye plaques loaded with , , or brachytherapy seeds. The listed was chosen to deliver 85 Gy to a central axis depth of 5 mm for each plaque size. In addition, the ratio of HETERO/HOMO per starting particle is included, indicating the impact of attenuation and scatter in the plaque components as a function of treatment depth. Finally, to deliver 85 Gy in HOMO media is presented.
Fourth-order polynomial coefficients to calculate the HETERO/HOMO ratio per starting particle as a function of distance along the central axis for . Note that distance should be reported in mm.
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