[Dosimetry verification of radioactive seed implantation with 3D printing template and CT guidance for paravertebral/retroperitoneal malignant tumor].

Objective: To compare the dose distributions of postoperative plans with preoperative plans for seeds implantations of paravertebral/retroperitoneal tumors assisted by 3D printing guide template and CT guidance, explore the effects of the technology for seeds implantations in dosimetry level and provide data support for the optimization and standardization in seeds implantation. Methods: Between December 2015 and July 2016, a total of 10 patients with paravertebral/retroperitoneal tumors (12 lesions) received 3D printing template assist radioactive seeds implantations in department of radiation oncology of Peking University Third Hospital, and included in the study. The diseases included cervical cancer, kidney cancer, abdominal stromal tumor, leiomyosarcoma of kidney, esophageal cancer and carcinoma of ureter. The prescribed doses was 110-150 Gy. All patients received preoperative planning design, individual template design and production, and the dose distribution of postoperative plan was compared with preoperative plan. Dose parameters including D(90), MPD, V(100), V(150,)conformal index(CI), EI of target volume and D(2cc) of organs at risk (spinal cord, aorta, kidney). Statistical software was SPSS 19.0 and statistical method was non-parameters Wilcoxon symbols test. Results: A total of 10 3D printing templates were designed and produced which were including 12 treatment areas.The mean D(90) of postoperative target area (GTV) was 131.1 (97.8-167.4 Gy) Gy. The actual seeds number of post operation increased by 3 to 12 in 5 cases (42.0%). The needle was well distributed. For postoperative plans, the mean D(90,)MPD, V(100,)V(150) was 131.1 Gy, 69.3 Gy, 90.2% and 65.2%, respectively, and which was 140.2 Gy, 65.6 Gy, 91.7% and 26.8%, respectively, in preoperative plans. This meant that the actual dose of target volume was slightly lower than preplanned dose, and the high dose area of target volume was larger than preplanned range, but there was no statistical difference in P value between the two groups except V(150)( P =0.004). The actual dose conformity of target volume was worse than preplanned (CI was 0.58 and 0.62, respectively) and the difference was statistically significant( P =0.019). The actual dose of external target volume was higher than preplanned (EI was 55% and 45.9%, respectively) and the difference had no significance. For organs at risk, the actual mean D(2cc) of spinal cord, aorta and kidney was 24.7, 54.4 and 29.7 Gy, respectively, which was higher than preplanned(20.6, 51.6 and 28.6 Gy, respectively), and there was no significant difference in two groups. Conclusions: Most parameters of postoperative validations for 3D printing template assisted seeds implantation in paravertebral/retroperitoneal are closed to the expectations of preoperative plans which means the improvement of accuracy in treatment.