Dosimetry verification of 3D-printed individual template based on CT-MRI fusion for radioactive 125I seed implantation in recurrent high-grade gliomas

Purpose: To verify the accuracy and efficacy of three-dimensional printing individual template (3D-PIT) with computed tomography-magnetic resonance imaging (CT-MRI) fusion for radioactive iodine-125 (I-125) seed implantation in high-grade brain gliomas. Material and methods: Between June 2017 and June 2018, 16 patients with recurrent high-grade gliomas (rHGG) underwent radioactive seed implantation with 3D-PIT. The prescribed dose was 120-140 Gy. We compared the dose distribution of the postoperative plan with the preoperative plan. Dose parameters included D-90, V-100, V-200, conformity index (CI), and external index of the target volume (EI). Local control and early complications were also analyzed. Results: Sixteen treatment areas were reported in our study. Median gross tumor volume (preoperative) of patients was 64.2 cm(3), median needle number was 8, and median number of implanted I-125 seeds was 60. For postoperative plans, the median D-90, V-100, and V-200 was 152.1 Gy, 96.8%, and 49.1%, respectively, and 151.7 Gy, 97.0%, and 48.9%, respectively, in preoperative plans. Comparing with the preplanned cases, the dose of the target volume was slightly higher; the high-dose area of the target volume was larger in postoperative cases, but the difference was not statistically significant (p > 0.05). Actual dose conformity of the target volume was greater than preplanned, and the difference was not statistically significant (p > 0.05). Local control was 81.25% and 75% at 3 and 6 months after implantation, respectively. No serious early toxicities were observed. Conclusions: 3D-PIT based on the CT-MRI fusion images can result in good accuracy for positioning and dose distribution in radioactive seed implantation for treatment of rHGG.