Dosimetric measurements in isolated human coronary arteries: comparison of commercially available iridium(192) with strontium/yttrium(90) emitters.

BACKGROUND Intravascular brachytherapy is being applied more and more in patients with coronary artery disease for the prevention of restenosis subsequent to balloon angioplasty, in particular after stent implantation. Several radiation sources (beta- and gamma-emitters) are available in clinical routine. It was the purpose of this study to compare the radiation doses at the level of the adventitia in diseased and stented human coronary arteries for (192)Ir and (90)Sr/Y emitters in routine use. In contrast to previously published work, we performed dosimetry instead of calculating depth-dose distribution by use of the Monte Carlo system. METHODS AND RESULTS Postmortem calcified human coronary artery segments were stented and placed in an organ bath. Commercially available gamma-emitters ((192)Ir; Cordis Checkmate) and beta-emitters ((90)Sr/Y; Novoste Beta-Cath) were used. Relative dose distributions along the adventitia were measured by a specially designed scintillation detector system. Whereas dose perturbations caused by stents and calcified plaque were negligible for the (192)Ir source, radiation from the beta source was significantly impaired (as much as 40%) at the level of the adventitia (3.0-mm vessel diameter). Dose perturbation was clearly dependent on the extent and severity of calcification, less affected by stent material. CONCLUSIONS Dose perturbation caused by calcified plaque and metallic stents is significant for beta-sources. This dosimetric difference between beta- and gamma-emitters in diseased coronary arteries should be considered when calculating doses in intravascular brachytherapy.