Dosimetric evaluation of I-125 seeds for treatment of portal vein tumor thrombosis

The portal vein tumor thrombosis (PVTT) is treated with an aid of a metallic stent to reduce portal vein pressure. In this study, a dosimetric evaluation of I-125 seeds was performed by using the Monte Carlo code, MCNP6.1. Our results provide isodose maps for a current configuration of I-125 seeds and would help to develop an optimized one. With the current configuration of I-125 seeds for the treatment of PVTT, there were clear hot spots and cold spots, since I-125 seeds were located at θ=0°, 90°, 180° and 270°. In addition, such hot spots and cold spots were observed along the z-axis. The maximum dose was delivered to z=3 or 9 mm at the surface of I-125 seeds. The amount of maximum dose was about 3.4 times higher than the normalized point. By applying our results to the clinical situations, one can change the number of I-125 seeds or its configurations to deliver the prescription dose uniformly and accurately.