3D-printed template and optical needle navigation in CT-guided iodine-125 permanent seed implantation

Initial needle tracking with the first standalone combined infrared camera - CT system for brachytherapy-analysis of tracking accuracy and uncertainties

PURPOSE

A prototype infrared camera - cone-beam computed tomography (CBCT) system for tracking in brachytherapy has recently been developed. We evaluated for the first time the corresponding tracking accuracy and uncertainties, and implemented a tracking-based prediction of needles on CBCT scans.

METHODS

A marker tool rigidly attached to needles was 3D printed. The precision and accuracy of tool tracking was then evaluated for both static and dynamic scenarios. Euclidean distances between the tracked and CBCT-derived markers were assessed as well. To implement needle tracking, ground truth models of the tool attached to 200 mm and 160 mm needles were matched to the tracked positions in order to project the needles into CBCT scans. Deviations between projected and actual needle tips were measured. Finally, we put our results into perspective with simulations of the system's tracking uncertainties.

RESULTS

For the stationary scenario and dynamic movements, we achieved tool-tracking precision and accuracy of 0.04 ± 0.06 mm and 0.16 ± 0.18 mm, respectively. The tracked marker positions differed by 0.52 ± 0.18 mm from the positions determined via CBCT. In addition, the predicted needle tips in air deviated from the actual tip positions by only 1.62 ± 0.68 mm (200 mm needle) and 1.49 ± 0.62 mm (160 mm needle). The simulated tracking uncertainties resulted in tip variations of 1.58 ± 0.91 mm and 1.31 ± 0.69 mm for the 200 mm and 160 mm needles, respectively.

CONCLUSION

With the innovative system it was possible to achieve a high tracking and prediction accuracy of marker tool and needles. The system shows high potential for applicator tracking in brachytherapy.

Experimental validation of the accuracy of robotic-assisted radioactive seed implantation for tumor treatment

An experimental validation of a robotic system for radioactive iodine-125 seed implantation (RISI) in tumor treatment was conducted using customized phantom models and animal models simulating liver and lung lesions. The robotic system, consisting of planning, navigation, and implantation modules, was employed to implant dummy radioactive seeds into the models. Fiducial markers were used for target localization. In phantom experiments across 40 cases, the mean errors between planned and actual seed positions were 0.98 ± 1.05 mm, 1.14 ± 0.62 mm, and 0.90 ± 1.05 mm in the x, y, and z directions, respectively. The x, y, and z directions correspond to the left-right, anterior-posterior, and superior-inferior anatomical planes. Silicone phantoms exhibiting significantly smaller x-axis errors compared to liver and lung phantoms (p < 0.05). Template assistance significantly reduced errors in all axes (p < 0.05). No significant dosimetric deviations were observed in parameters such as D90, V100, and V150 between plans and post-implant doses (p > 0.05). In animal experiments across 23 liver and lung cases, the mean implantation errors were 1.28 ± 0.77 mm, 1.66 ± 0.69 mm, and 1.86 ± 0.93 mm in the x, y, and z directions, slightly higher than in phantoms (p < 0.05), with no significant differences between liver and lung models. The dosimetric results closely matched planned values, confirming the accuracy of the robotic system for RISI, offering new possibilities in clinical tumor treatment.

A retrospective study on unresectable or inoperable head and neck cancers treated with stereotactic ablative brachytherapy

Purpose

The aim of the present study was to assess the clinical efficacy and safety of stereotactic ablative brachytherapy (SABT) for unresectable or inoperable head and neck cancers.

Material and methods

This study retrospectively assessed clinical data of 37 patients with unresectable or inoperable head and neck cancers treated with SABT from October 2016 to October 2021. Variables evaluated included local efficacy, local control rate (LCR), overall survival (OS) rate, and radiological adverse effects.

Results

The median follow-up was of 34 months (range, 5-59 months), and LCR at 6, 12, and 24 months was 89.2%, 78.2%, and 69.4%, respectively. The median survival time was 16 months [95% confidence interval (CI): 10.5-21.5 months], and the OS rate at 6, 12, and 24 months was 97.3%, 70.3%, and 34.5%, respectively. The results of univariate analysis revealed that the type of pathology and gross tumor volume (GTV) D₉₀ were related to LCR (p < 0.05). However, the type of pathology, GTV D₉₀, age, and implantation site were related to OS rate (p < 0.05). The results of multivariate analysis showed that the type of pathology and GTV D₉₀ were substantially related to LCR and OS rate (p < 0.05). The evaluation of post-operative radiological adverse reactions revealed that seven cases (18.9%) developed grade 1-2 skin reactions, four cases (10.8%) developed grade 1-2 oral mucosal outcomes, and no cases developed grade 3 or higher adverse reactions. Post-operative seed dislocation occurred in three patients with tongue cancer.

Conclusions

SABT has produced good local control and mild adverse reactions in the treatment of unresectable or inoperable head and neck cancers. Additionally, it is safe, feasible, minimally invasive, and has fewer adverse effects than other treatment modalities.

Clinical application and accuracy assessment of imaging-based surgical navigation guided 125I interstitial brachytherapy in deep head and neck regions

Brachytherapy has the advantages of being minimally invasive and highly conformal, and it achieves good results in head and neck tumors. To precisely implant the radioactive seeds according to the preplan in deep head and neck regions, the surgical navigation is applied. This study aims to explore the clinical application and accuracy of imaging-based surgical navigation-guided 125I interstitial brachytherapy in terms of seed position. We included 41 patients with tumors in deep head and neck regions. The brachytherapy treatment plan was designed, and the preplanned data were transferred to the navigation system. Needle implantation and seed delivery were performed under surgical navigation system guidance with or without the combination of individual template. The treatment accuracy was evaluated by comparing seed cluster locations between the preoperative treatment plan and the postoperative treatment outcome. A total of 2879 seeds were delivered. The range, mean and median distances between the geometric centers of the preoperative seed point clusters and the postoperative seed point clusters were 0.8-10.5 mm, 4.5 ± 2.3 mm and 4.1 mm, respectively. The differences between preoperative and postoperative volumes of the minimum bounding box of seed point clusters were nonsignificant. In conclusion, the imaging-based surgical navigation system is a promising clinical tool to provide the preplanned data for interstitial brachytherapy intraoperatively, and it is feasible and accurate for the real-time guidance of needle implantation and seed delivery in deep head and neck regions.

Re-Irradiation for Recurrent Cervical Cancer: A State-of-the-Art Review

The recurrence rate of cervical cancer after primary treatment can reach 60%, and a poor prognosis is reported in most cases. Treatment options for the recurrence of cervical cancer mainly depend on the prior treatment regimen and the location of recurrent lesions. Re-irradiation is still considered as a clinical challenge, owing to a high incidence of toxicity, especially in in-field recurrence within a short period of time. Recent advances in radiotherapy have preliminarily revealed encouraging outcomes of re-irradiation. Several centers have concentrasted on stereotactic body radiation therapy (SBRT) for the treatment of well-selected cases. Meanwhile, as the image-guiding techniques become more precise, a better dose profile can also be achieved in brachytherapy, including high-dose-rate interstitial brachytherapy (HDR-ISBT) and permanent radioactive seed implantation (PRSI). These treatment modalities have shown promising efficacy with a tolerable toxicity, providing further treatment options for recurrent cervical cancer. However, it is highly unlikely to draw a definite conclusion from all of those studies due to the large heterogeneity among them and the lack of large-scale prospective studies. This study mainly reviews and summarizes the progress of re-irradiation for recurrent cervical cancer in recent years, in order to provide potential treatment regimens for the management of re-irradiation.