Dosimetric considerations for catheter-based beta and gamma emitters in the therapy of neointimal hyperplasia in human coronary arteries

Purpose: Recent data indicate that intraluminal irradiation of coronary arteries following balloon angioplasty reduces proliferation of smooth muscle cells, neointima formation, and restenosis. We present calculations for various isotopes and geometries in an attempt to identify suitable source designs for such treatments. Methods and Materials: Analytical calculations of dose distributions and dose rates are presented 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 diameter), Dose must be confined to the region of the angioplasty, with reduced doses to normal tissues, Beta emitters have radiation safety advantages, but may not have suitable ranges for treating large diameter vessels. Gamma emitters deliver larger doses to normal tissues and to staff, Low energy x-ray emitters such as I-125 and Pd-103 reduce these risks but are not available at high enough activities, The feasibility of injecting a radioactive liquid directly into the angioplasty balloon 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 have 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.