Objective: To study the surface radial dose distribution of different length radioactive biliary stents in different activity of (125)I seeds by treatment planning system.
Methods: After a radioactive biliary stent was positioned in measurement phantom, which were made of solid paraffin and polymethyl methacrylate, a CT scan was performed to get the stent images. The images were then transferred to the treatment planning system for planning. The maximum dose level slice nearest to the center of the stent was selected to calculate the surface radial dose distribution.
Results: The length of the stents (F=3 189.160, P<0.01) and the activity of the (125)I seeds (F= 811.509, P<0.01) can both significantly affect the cumulative radial dose distribution of the radioactive stent. Radial cumulative dose dose (Gy), stent length (cm), (125)I seeds activity (mCi) and distance from the stent surface (cm) meet the regression equation: ln dose =2.565+ 0.208 length+ 1.502 activity-0.738 distance (F=4 929.279, P<0.05).
Conclusions: The choice of suitable activity of radioactive (125)I should be based on treatment purpose in combination with the length and diameter of lesion and also with reference to the dose table. The measurement results are with smaller uncertainty, which can provide reference for the clinical application of dosimetry.