Lung density effect on 125I dose distribution.

Perturbations in 125I implant dose distribution due to lung tissue variations have been investigated. Dose correction factors for a point source, a planar, and a volume implant have been calculated using a model which accounts for the changes in primary photon attenuation and in buildup factor when the medium is lung rather than water. Results of our calculation show that the change in dose is about 9% and 20% in the core and the periphery, respectively, of a representative implanted volume whose density is 0.25 relative to water.