[Safety evaluation of iodine-125 seed implantation in rabbit liver tissue]

To evaluate the safety of iodine-125 seed implantation in the liver.

Twenty New Zealand rabbits were divided into control and treatment groups and in the latter, iodine-125 seeds of 37 MBq were implanted into the liver under CT guidance whereas nonradioactive seeds were implanted in the control rabbits. Four weeks after implantation, white blood cell count, liver functions, and renal functions were measured or evaluated for comparison with those before implantation. The rabbits were then anesthetized to collect the liver tissue for pathological examination with HE staining and cell apoptosis assay.

Obvious hepatic tissue necrosis was observed around the radioactive seeds in the treatment group. At a 5 mm distance to the seeds, a distinct boundary occurred between the necrotic hepatic cells and normal cells. The control rabbits, however, had normal liver structure around the seeds implanted. In situ cell apoptosis examination showed a distinct band of apoptotic cells in the liver tissue of rabbits in the treatment group, which was not found in the control group. Two weeks after iodine-125 irradiation, alanine aminotransferase significantly increased in the treatment group (t=6.285, P<0.001), but recovered two weeks later (t=2.002, P=0.06). No significant alterations occurred in aspartate aminotransferase, blood urea nitrogen, serum creatinine, hemoglobin, serum total bilirubin, white blood cell count, or platelet count after the seed implantation.

Iodine-125 seed implantation in the liver results in conformal irradiation dose distribution without obvious effects on the vital organs, demonstrating iodine-125 seed implantation as a safe and minimally invasive technique for hepatic cancer treatment.