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Purpose To preliminarily verify the accuracy of navigation-assisted seed implantation by comparing pre-operative and actual differences in puncture characteristics and dosimetry in computed tomography (CT)-guided, navigation-assisted radioactive iodine-125 seed implantation, using 3D-printed templates for malignant tumors’ treatment. Material and methods A total of 27 tumor patients, who were treated with seed implantation under combination guidance in our hospital between December 2019 and December 2020 were enrolled in this study. Navigation needles (n = 1-3) were placed in each patient to obtain pre-operative and intra-operative puncture information, such as angle, depth, insertion point, and tip position. Moreover, dosimetry parameters in pre-operative and post-operative plans, including D90, V100, V150, V200, minimum peripheral dose (MPD), conformal index, external index, and homogeneity index of target area were investigated. Results Mean errors of the angle, depth, insertion point, and tip position were 0.5 ±0.5°, 4.0 ±2.0 mm, 1.7 ±1 mm, and 3.1 ±1.8 mm, respectively. There were no significant differences between intra-operative and pre-operative angles (p = 0.271), but there was a significant difference in the depth (p = 0.002). Errors of the angle, depth, and insertion point were larger for the pelvic/retroperitoneal area than for the head and neck/chest wall (p < 0.05). With the exception of MPD, there was no significant difference in dosimetry indices between post-operative and preoperative plans (p > 0.05). Conclusions Seed implantation under combination guidance showed good accuracy, and the actual intra-operative puncture information and post-operative doses were in agreement with those in the pre-operative plan, thereby demonstrating promising prospects for further development.

Purpose To investigate the accuracy and dosimetry of 3D-printing non-coplanar template (3D-PNCT)-assisted computed tomography (CT)-guided iodine-125 seed implantation (125I-SI) for recurrent chest wall cancer (rCWC). Material and methods This was a retrospective study of 19 patients with 22 rCWC treated with 3D-PNCT-assisted CT-guided 125I-SI, from Mar 2017 to Mar 2020 in our institute. Results Mean needle entrance deviation was 4.50 ±2.70 mm, mean angular deviation was 3.40 ±3.10 degrees, and mean depth deviation was 5.20 ±5.20 mm. No significant difference was found for dosimetric parameters (except conformity index) between pre-plan and post-plan; D90, D100, V100, V150, and V200 were 157.74 ±24.23 and 151.71 ±33.62 (p = 0.228), 85.36 ±34.09 and 70.46 ±23.48 (p = 0.067), 0.93 ±0.04 and 0.90 ±0.07 (p = 0.068), 0.64 ±0.16 and 0.64 ±0.16 (p = 0.984), and 0.35 ±0.17 and 0.37 ±0.18 (p = 0.382) for pre-plan and post-plan, respectively. Conformity index, external index, and homogeneity index were 0.57 ±0.16 and 0.52 ±0.15 (p = 0.007), 0.73 ±0.55 and 0.79 ±0.53 (p = 0.096), and 0.31 ±0.15 and 0.30 ±0.14 (p = 0.504) for pre-plan and post-plan, respectively. Median follow-up time was 8 months (range, 3-30 months). Complete response was observed in 4/22 (18.1%), partial response in 13/22 (59.1%), stable disease in 4/22 (18.1%), and progression disease in 1/22 (4.5%) of the cancers. Among patients with pain before 125I-SI, pain relief rate was 87.5% (7/8). No peri-operative complications of more than grade 2 were observed. Conclusions 3D-PNCT-assisted CT-guided 125I-SI may be safe and feasible as palliative therapy for non-surgical candidates and painful patients with rCWC.

Purpose To compare post-implant dosimetric parameters of computed tomography (CT)-guided radioactive iodine-125 (125I) seed (RIS) implantation assisted with and without three-dimensional printing non-coplanar template (3D-PNCT) in locally recurrent rectal cancer (LRRC). Material and methods One hundred and fifty-five LRRC patients treated by CT-guided RIS implantation assisted with or without 3D-PNCT from October 2003 to May 2019 were included in this study. Propensity score matching (PSM) method (1 : 1) was used to adjust for differences between the 3D-group (with 3D-PNCT) and the CT-group (without 3D-PNCT). After PSM, dosimetric parameters [D90 (dose that covered 90% of target volume), D100 (dose that covered 100% of target volume), V100 (percentage of gross tumor volume (GTV) receiving 100% of prescription dose), V150 (percentage of GTV receiving 150% of prescription dose), HI (homogeneity index), CI (conformity index), and EI (external index)] of the two groups were compared. Results After PSM, 45 pairs of matched cases were selected for analysis and differences in variables between the two groups were balanced. For the 3D-group, median values of D90, D100, V100, V150, EI, and HI were 142.6 Gy (73.7-218.2 Gy), 73.7 Gy (26.2-169.3 Gy), 94.1% (74.3-100%), 71.8% (35.4-98.3%), 0.7 (0.1-30.7), and 0.20 (0-0.60), respectively, and corresponding values were 119.9 Gy (39.8-159.3 Gy), 47.0 Gy (13.0-200.9 Gy), 89.9% (38.6-100%), 62.8% (14.8-100%), 0.39 (0-11.01), and 0.30 (0-0.95), respectively, for the CT-group. Parameters including D90, D100, V100, V150, and EI in the 3D-group were significantly higher than those in the CT-group (p < 0.001, p < 0.001, p < 0.001, p < 0.001, and p = 0.006, respectively). Conclusions 3D-PNCT can improve the accuracy of radioactive seed implantation by increasing the dose delivered to the tumor and reducing the number of "cold" spots of dose.

Purpose We compared the three-dimensional printed non-coplanar template (3DPNCT) plans with 3D-printed coplanar template (3DPCT) plans for radioactive seed implantation (RSI) in lung cancer and explored the differences between the two technologies. Material and methods 33 patients with peripheral lung cancer that received 3DPCT-assisted RSI in our department between June 2017 and February 2018 were analyzed. A 3DPNCT plan was re-designed for all patients. The prescribed dose and seed activity in the new plan were the same as the 3DPCT plan. The data in the two plans were compared, including seed number, needle number, number of needles needed to cross the ribs, and dosimetry parameters. Dosimetry parameters included D90, Dmean, MPD (minimum peripheral dose), V100, V150, CI (conformity index), EI (external index), HI (homogeneity index) of target volume, D2cc of spinal cord and aorta, and V20 of affected side lung. We used a paired t-test and two groups of related non-parameters tests to examine statistical significance. A p value < 0.05 was considered statistically significant. Results We found no significant difference in dosimetry parameters (p > 0.05), except MPD. The mean MPD of the 3DPNCT plan was significantly higher than the 3DPCT plan (88.5 Gy and 81.8 Gy, respectively, p = 0.017). The number of needles used in the 3DPNCT plan and the number of needles needed to cross the ribs were significantly less compared with the 3DPCT plan (p = 0.000). Conclusions The dose distributions of the two 3DPCT plans were similar. 3DPNCT plan had a higher dose in target volume margin, with fewer needles and fewer breaks to the ribs.

Purpose The aim of this study was to evaluate the efficacy and safety of interstitial permanent low-dose-rate ultrasound-guided 125I seeds implantation of local head and neck recurrent tumors. Material and methods Sixty-four consecutive patients, with 81 lesions in total, underwent permanent implantation of 125I seeds under ultrasound guidance. Post-operative dosimetry was performed for all patients. Follow-up period ranged 103.5 months (median, 14 months). Results Among the 81 lesions, the totally response rate was 80.2%, and 22 (27%) and 43 (53%) lesions showed complete and partial remission. The 1-, 3-, and 5-year tumor control rates were 75.2%, 73.0%, and 69.1%, respectively. The results for cervical lymph node recurrence were better than those for recurrence or residual disease of primary head and neck neoplasms, with 5-year local control rates of 72.7% and 39.9%, respectively. D90 was an independent prognostic factor of the tumor control, and lesion recurrence location and time to tumor progression were prognostic factors of survival. As of the date of follow-up, 22 of 64 patients were still alive. The 1-, 3-, and 5-year overall survival rates were 57.4%, 31%, and 26.6%, respectively, with a median survival of 20 months. Grade 4 skin ulceration was seen in two patients; grade 1 or 2 skin reactions were seen in 11 patients (17%) who had received external beam radiotherapy before. Other severe complications were absent. Conclusions Interstitial permanent implantation of 125I seeds under ultrasound guidance is feasible, efficacious, and safe for refractory head and neck metastasis or recurrence.

Purpose The aim of this study was to evaluate the efficacy and safety of interstitial permanent low-dose-rate ultrasound-guided 125I seeds implantation of local head and neck recurrent tumors. Material and methods Sixty-four consecutive patients, with 81 lesions in total, underwent permanent implantation of 125I seeds under ultrasound guidance. Post-operative dosimetry was performed for all patients. Follow-up period ranged 103.5 months (median, 14 months). Results Among the 81 lesions, the totally response rate was 80.2%, and 22 (27%) and 43 (53%) lesions showed complete and partial remission. The 1-, 3-, and 5-year tumor control rates were 75.2%, 73.0%, and 69.1%, respectively. The results for cervical lymph node recurrence were better than those for recurrence or residual disease of primary head and neck neoplasms, with 5-year local control rates of 72.7% and 39.9%, respectively. D90 was an independent prognostic factor of the tumor control, and lesion recurrence location and time to tumor progression were prognostic factors of survival. As of the date of follow-up, 22 of 64 patients were still alive. The 1-, 3-, and 5-year overall survival rates were 57.4%, 31%, and 26.6%, respectively, with a median survival of 20 months. Grade 4 skin ulceration was seen in two patients; grade 1 or 2 skin reactions were seen in 11 patients (17%) who had received external beam radiotherapy before. Other severe complications were absent. Conclusions Interstitial permanent implantation of 125I seeds under ultrasound guidance is feasible, efficacious, and safe for refractory head and neck metastasis or recurrence.