DOSIMETRIC CONSIDERATIONS FOR CATHETER-BASED BETA-EMITTER AND GAMMA-EMITTER IN THE THERAPY OF NEOINTIMAL HYPERPLASIA IN HUMAN CORONARY-ARTERIES

Purpose: Recent data indicate that intraluminal irradiation of coronar y arteries following balloon angioplasty reduces proliferation of smoo th muscle cells, neointima formation, and restenosis. We present calcu lations for various isotopes and geometries in an attempt to identify suitable source designs for such treatments. Methods and Materials: An alytical calculations of dose distributions and dose rates are present ed for Ir-192, I-125, Pd-103, P-32, and Sr-90 for use in intracoronary irradiation, The effects of source geometry and positioning accuracy are studied. Results: Accurate source centering, high dose rate, well- defined treatment volume, and radiation safety are all of concern; 15- 20 Gy are required to a length of 2-3 cm of vessel wall (2-4 mm diamet er), Dose must be confined to the region of the angioplasty, with redu ced doses to normal tissues, Beta emitters have radiation safety advan tages, but may not have suitable ranges for treating large diameter ve ssels. Gamma emitters deliver larger doses to normal tissues and to st aff, Low energy x-ray emitters such as I-125 and Pd-103 reduce these r isks but are not available at high enough activities, The feasibility of injecting a radioactive liquid directly into the angioplasty balloo n is also explored, Conclusions: Accurate source centering is found to be of great importance. If this can be accomplished, then high energy beta emitters such as Sr-90 would be ideal sources. Otherwise, gamma emitters such as Ir-192 may be optimal. A liquid beta source would hav e optimal geometry and dose distribution, but available sources, such as P-32 are unsafe for use with available balloon catheters. Copyright (C) 1996 Elsevier Science Inc.