Background:Portal-vein stent combined with one iodine-125 (I) seed strand has become a new treatment for portal vein tumor thrombosis. However, dosimetric aspects of this irradiation stent have not been reported. Therefore, we aimed to undertake dosimetric analyses comparing portal-vein stents combined with different numbers ofI seed strands.

Methods:A water cylinder was created by a treatment-planning system to simulate a portal-vein stent. The stent was combined with one, two, or threeI seed strands (Groups I, II, and III, respectively). At different prescribed doses (PDs),I seeds of identical activities were loaded on Groups I-III. Conformation number (CN), external volume index, and homogeneity index were calculated. Linear regression analyses were used to evaluate the obtained data.

Results:For identicalI seed activity, when theI seed strand increased from one chain to two, D(dose delivered to 90% of the target volume) increased by ≥184%; when it increased from two chains to three, Dincreased by ≥63%. When the PD was 105 Gy andI seed strands increased from one chain to two, V(percentage of the target volume receiving ≥90% of the PD) increased by 158-249%; when it increased from two chains to three, Vincreased by 7-175%. CN was correlated positively withI seed activity (B = 0.479, P < 0.001) and number ofI seed strands (B = 0.201, P < 0.001) and was independent of PD (B = -0.002, P = 0.078).

Conclusions:A portal-vein stent combined with a singleI seed strand could not meet dosimetry requirements. For a stent combined with twoI seed strands, when the PD was 105 Gy and seed activity was 0.7 mCi, the dose distribution could satisfy dosimetry requirements. For a stent combined with threeI seed strands, if the PD was 105, 125, or 145 Gy, the recommended seed activities were 0.5, 0.5, and 0.6 mCi, respectively.