Monte Carlo Dose Calculation of 90Sr/90Y Source in Water Phantom

90Sr/90Y source has been used for the intravascular brachytherapy to prevent coronary restenosis in the patients who have undergone angioplasty. The aim of this research is to determine the dose distribution of 90Sr/90Y source in a water phantom. In the present work, MCNP code has been applied to calculate the dose distribution around a 3 cm length of 90Sr/90Y source in a 30×30×30 cm3 water phantom. Also, the exact geometry of the source has been used in this simulation. Tally *F8:e which is suitable for beta ray dosimetry has been evaluated with less than %5 relative error in a sphere having 0.2 mm radius. The isodose curve for 10, 20, 40, and 90% depth dose (PDD) were derived based on the calculated dose curves along the parallel and perpendicular axis to the source.Discussion and The results obtained in this work are in a good agreement with the experimental result published by Buckley et al. and the International Atomic Energy Agency (IAEA) report in a water phantom. Therefore, the result of this research can be used in the intravascular brachytherapy.