GPP10 Presentation Time: 10:10 AM: Using 3D Printed Vaginal Individualized Applicator (VIA) to Simplify Needle Insertion, Guide Needle Distribution and Optimize Dosimetry for Gynecologic Interstitial and Cervix Hybrid Brachytherapy

Abstract

<h3>Purpose</h3> Optimally placing interstitial needles either as part of hybrid procedures for the treatment of cervical cancer or for interstitial only gynecologic brachytherapy requires time and expertise. Individualized templates to guide needles to dosimetrically beneficial positions could simplify interstitial and hybrid procedures, decrease procedure time, improve needle distribution and optimize dosimetry. <h3>Materials and Methods</h3> We developed a novel approach using 3D printed Vaginal Individualized Applicator (VIA) templates that contain internal channels that guide interstitial needles from the vaginal introitus to the desired locations within the tumor. The use of 3D printing allows for curved and angled needle trajectories allowing needle distribution to be individualized based on patient and tumor anatomy, such as having a narrow vaginal applicator with needle paths to cover a much wider tumor diameter. The channel directions and needle depths are based on a pre-planning approach. Following a pre-procedure MRI, CTV contours are drawn and converted to a Computer Aided Design (CAD) format. Within the 3D design software, a simple 25 mm diameter cylinder is used to start. Needle paths are manually designed to cover the target following a set of basic rules, which include needle spacing and bending angles. The cylinder with curved needle paths is intended to be slid over the tandem after insertion, or used on its own with a needle in the central location (Figure 1A). The resulting design is 3D printed with biocompatible materials and sterilized pre-procedure. Depending on the printing options (in-house printer or external vendor), the process takes from one week to 24 hours, thereby enabling fraction-to-fraction modifications. <h3>Results</h3> We have created and used clinically 3D printed VIA templates for both hybrid cervix brachytherapy for patients with narrow vaginal canals and for interstitial only gynecologic brachytherapy. The VIA design allows for dwell times within the needles and also within the cylinder component. By allowing the placement of needles from the vaginal introitus, the VIA increases the ease and simultaneously decreases the complexity of optimally placing interstitial needles within the region of the tumor. This design approach also allows additional needles to be placed through available potential channels, if found to be needed, following 3D imaging with CT or MRI, without removing any of the applicator (Figure 1B). For hybrid procedures (n=7), use of the VIA decreased procedure time by 45% (from 33.1 to 18.3 minutes) and improved or maintained excellent dosimetry with an average CTV V100% of 93.4% vs. 90.9% for other hybrid applicators. Similarly, in using the VIA for interstitial-only cases (n=1), we found that needle placement was reduced by 30 minutes or 33% quicker than standard interstitial procedures with similar dosimetry (CTV V100% 95.4 % for VIA vs. 93.4%). <h3>Conclusions</h3> Our team developed a novel 3D printed VIA template that significantly facilitates gynecologic interstitial and cervix hybrid brachytherapy by simplifying the placement of needles, decreasing procedure time and optimizing dosimetry. The clinical data above demonstrates the benefits of this approach for patients with narrow vaginal canals that do not accommodate commercial hybrid applicators. The VIA can easily be designed to facilitate interstitial gynecologic brachytherapy for multiple clinical situations.