Monte Carlo modeling of radiation dose distributions in intravascular radiation therapy

Radiation dose distributions are developed for balloon and wire sources of radioactivity within coronary arteries. The Monte Carlo codes MCNP 4B and E GS4 were used to calculate dose distributions for photons and electrons at discrete energies around such sources, with and without the presence of a h igh-density atherosclerotic plaque. An interactive computer program was dev eloped which then calculates dose distributions for many radionuclides by a pplying the emission spectra to the discrete energy grids calculated by the Monte Carlo codes, weighting appropriately for electron energy and abundan ce. Results for Re-186 and Re-188 balloon sources are shown in comparison t o an Ir-192 wire source. The program provides dose distributions as well as estimates of activity levels needed to deliver prescribed doses to the ves sel wall at selected distances from the lumen in a selected time interval. In addition, dose calculations are presented in this paper for other organs in the body, from photon radiation as well as from possible loss of liquid activity into the bloodstream in the case of a balloon rupture. These resu lts, especially the interactive computer program permitting easy comparison of various radionuclides and their physical characteristics, will greatly facilitate the comparison process and aid in the selection of the best cand idate(s) fur clinical use. (C) 2000 American Association of Physicists in M edicine. [S0094-2405(00)02005-8].