Dosimetric Measurements in Isolated Human Coronary Arteries

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Abstract
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 (β- and γ-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 γ-emitters ( 192 Ir; Cordis Checkmate) and β-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 β-sources. This dosimetric difference between β- and γ-emitters in diseased coronary arteries should be considered when calculating doses in intravascular brachytherapy.

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