Factors affecting dose distributions in brachytherapy of coronary arteries with P-32 linear source

Summary Background Long-term results of brachytherapy of coronary arteries may be influenced by inhomogeneity of the dose distribution. The dose distribution perturbations due to the presence of stent struts, guide wires and calcium deposits were therefore investigated. Aim The aim of the study was to investigate dose distribution perturbations due to the presence of stent struts, guide wire and calcium deposits during the irradiation. Both experimental and calculational techniques were applied to elucidate these influences. Materials/Methods The measurements were carried out with radiochromic foil in a phantom in the presence and absence of the stent and the guide wire. Due to the measurements being limited by the thickness of the detecting foil, the radial dose distribution with or without the metallic stent components were also performed using the MCNP Monte Carlo code. The same code was used to measure the influence of cholesterol plaques on dose distribution in the vessel walls. Results A large dose reduction in the area shielded by the guide wire was observed. The presence of the stent caused a 15% dose reduction behind the struts. The dose reduction caused by calcium deposits ranged from 11% to 32%. Conclusions These facts may increase the probability of late restenosis after irradiation due to underdosage. The inhomogeneity occurring behind the guide wire, stent struts and calcium deposits should be taken into account in the analysis of dose distributions for clinical applications.