AbstractID: 8004 Title: Generic activity nomogram for ¹²⁵I prostate implants
A power-law model was developed that predicts the activity necessary to treat to a given minimum peripheral dose in prostate
brachytherapy. The nomogram model was derived for the generic
source designs.
125
I brachytherapy source and then applied for several different
An ellipsoidal-cylindrical model was used to describe the treated volume.
In the simulation, Patterson-Parker
(modified peripheral) loading was used. Available consensus values for TG43 dosimetric parameters of the various brachytherapy
sources were used. The simulation method was validated by predicting the results of earlier workers for the model 6711 source and
for both ellipsoidal and sphero-cylindrical models. The nomogram was determined from simulations for a range of volumes, 13.7 to
73.6 cm3, having both base-to-apex height and average dimension ranging from 3 to 5.2 cm. For each volume, the model surface was
sampled by 778 points at which the integral (full decay) dose from 36 to 134 seeds was calculated. On average, the nomogram differs
from simulation results by about 1% [-2, +4 % range]. Given the validation for the 6711 source, the theoretical nomogram of this
work is expected to compare well with experience in clinical prostate brachytherapy. Comparisons of predicted activity to actual
activity for selected seed models are presented.