Analysis on the accuracy of CT-guided radioactive I-125 seed implantation with 3D printing template assistance in the treatment of thoracic malignant tumors

Experts consensus on 3D-printing template-assisted CT-guided radioactive iodine-125 seed implantation for recurrent soft tissue carcinoma in China

Permanent radioactive iodine-125 seed implantation (RISI), known as radioactive seed implantation, is a minimally invasive internal radiation technique. This method involves implanting 125I seeds (4.5 × 0.8 mm, encapsulated in a nickel-titanium alloy) into tumors under image guidance. The radionuclide continuously releases low energy γ-rays, effectively killing tumor cells. RISI delivers high local doses with minimal damage to surrounding normal tissues. It is performed through image-guided percutaneous puncture, accompanied by high precision, minimal trauma, and rapid recovery. In Western countries, RISI is primarily utilized for early-stage prostate cancer. In 2002, Professor Junjie Wang introduced computed tomography (CT)-guided technology for RISI, expanding its indications to head and neck, thoracic, abdominal, pelvic, and spinal tumors. In 2014, he proposed the concept of image-guided interventional brachytherapy, advancing minimally invasive brachytherapy. In 2015, he integrated three-dimensional 3D-printing template (3D-PT) with CT-guided technology, significantly enhancing the precision, quality, and efficiency of RISI, and introduced the concept of stereotactic brachytherapy. Over nearly 20 years, RISI has developed into a standardized procedure, involving preoperative planning, intraoperative optimization, and postoperative verification, highlighting its role in comprehensive cancer treatment. The main treatments for soft tissue sarcoma (STS) include surgery or surgery combined with radiotherapy and chemotherapy. However, STS is prone to local recurrence, and effective treatments are lacking after recurrence. Experts have conducted extensive trials on RISI for the treatment of recurrent STS (r-STS), accumulating significant clinical experience. This study aimed to establish standards and consensus on 3D-PT-assisted CT-guided RISI for the treatment of r-STS.

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.

The Use of 3D Printing Technology in Gynaecological Brachytherapy-A Narrative Review

Radiation therapy, including image-guided adaptive brachytherapy based on magnetic resonance imaging, is the standard of care in locally advanced cervical and vaginal cancer and part of the treatment in other primary and recurrent gynaecological tumours. Tumour control probability increases with dose and brachytherapy is the optimal technique to increase the dose to the target volume while maintaining dose constraints to organs at risk. The use of interstitial needles is now one of the quality indicators for cervical cancer brachytherapy and needles should optimally be used in ≥60% of patients. Commercially available applicators sometimes cannot be used because of anatomical barriers or do not allow adequate target volume coverage due to tumour size or topography. Over the last five to ten years, 3D printing has been increasingly used for manufacturing of customised applicators in brachytherapy, with gynaecological tumours being the most common indication. We present the rationale, techniques and current clinical evidence for the use of 3D-printed applicators in gynaecological brachytherapy.

3D printing in brachytherapy: A systematic review of gynecological applications

PURPOSE

To provide a systematic review of the applications of 3D printing in gynecological brachytherapy.

METHODS

Peer-reviewed articles relating to additive manufacturing (3D printing) from the 34 million plus biomedical citations in National Center for Biotechnology Information (NCBI/PubMed), and 53 million records in Web of Science (Clarivate) were queried for 3D printing applications. The results were narrowed sequentially to, (1) all literature in 3D printing with final publications prior to July 2022 (in English, and excluding books, proceedings, and reviews), and then to applications in, (2) radiotherapy, (3) brachytherapy, (4) gynecological brachytherapy. Brachytherapy applications were reviewed and grouped by disease site, with gynecological applications additionally grouped by study type, methodology, delivery modality, and device type.

RESULTS

From 47,541 3D printing citations, 96 publications met the inclusion criteria for brachytherapy, with gynecological clinical applications compromising the highest percentage (32%), followed by skin and surface (19%), and head and neck (9%). The distribution of delivery modalities was 58% for HDR (Ir-192), 35% for LDR (I-125), and 7% for other modalities. In gynecological brachytherapy, studies included design of patient specific applicators and templates, novel applicator designs, applicator additions, quality assurance and dosimetry devices, anthropomorphic gynecological applicators, and in-human clinical trials. Plots of year-to-year growth demonstrate a rapid nonlinear trend since 2014 due to the improving accessibility of low-cost 3D printers. Based on these publications, considerations for clinical use are provided.

CONCLUSIONS

3D printing has emerged as an important clinical technology enabling customized applicator and template designs, representing a major advancement in the methodology for implantation and delivery in gynecological brachytherapy.