Dosimetry of 188Re and 186Re sources based on Monte Carlo calculations for endovascular brachytherapy after balloon angioplasty

Background: Recent pre-clinical and clinical studies indicate that irradiation in the dose range of 15 to 30 Gy can reduce rate of restenosis in patients who have undergone an angioplasty. The use of filled balloon with radioactive solution was proposed as one of the possible intravascular irradiation techniques. Materials and Methods: The Monte Carlo N-particle Transport Code (MCNP4b) was used to calculate the dose rate distribution in the tissue equivalent material around the 188Re and 186Re liquid sources. Schematic of Medical Internal Radiation Dose (MIRD) for homogeneous distribution of radio-nuclide in a lesion was used for mean organ absorbed dose calculation due to the internal distribution. Results: Results indicate that 188Re liquid with 100 mCi/ml and 186Re liquid with 250 mCi/ml can deliver desired dose in the vessel wall to reduce restenosis. The dose ratio in depth of 0.5 mm to surface of vessel wall for 188Re and 186Re were 40% and 18%, respectively. Therefore in case of 186Re, there is a little non-uniformity with respect to the 188Re case. The delivery of form 186Re dose to normal tissue around target tissue is less than 188Re. Conclusion: Use of the Monte Carlo simulation with 188Re-DTPA and 186Re-DTPA for intra-vascular brachytherapy is a feasible method of delivering a desired dose to the vessel walls. Although188Re-DTPA delivers the desired dose to the target tissue with lower radioactive concentration (mCi/ml), but with the use of 186Re-DTPA, the delivery dose to normal tissue around the target tissue is less. Iran . J. Radiat. Res., 2004 2 (2): 89-95