GSOR11 Presentation Time: 9:55 AM: 3D Printing Enhanced GYN Brachytherapy: From Novice to Expert in One Print with the TARGIT-FX

Abstract

<h3>Purpose</h3> It is well established in cervical brachytherapy that the addition of interstitial (IS) needles to intra-cavitary (IC) applicators can significantly enhance dosimetry by improving target coverage without increasing normal tissues doses. Accurate placement of interstitial needles requires significant technical skill and imaging guidance proficiency, thereby limiting the benefits to a subset of practitioners and patients. Available commercial combined IC/IS applicators restrict the available needle positions to often unsatisfactory locations for optimized dosimetry. We have developed and further improved our supplemental templates that attach to the tandem applicator and guides needles to optimized positions for different tumor topologies. This new TARGIT-FX (Tandem Anchored Radially Guiding Interstitial Template - Flexible eXtended) is 3D printed from biologically compatible materials, can be steam sterilized and provides multiple degrees of flexibility to simplify and facilitate interstitial needle insertion. <h3>Materials/Methods</h3> Our previously described IS needle guide (TARGIT), which facilitates placement of complementary needles in a tandem and ovoid implant, was redesigned with the purported goal of added flexibility and ease of use. The tandem attached small template was extended all the way to the vaginal introitus to allow needle insertion from outside the patient. The number of needle position options increased from four to nine to better cover a wider range of clinical situations: three paired width options ((2.0, 1.5 and 1.25 cm width) at the level of point A and three individual posterior locations (figure, insert E). The new design has been used clinically for 14 different patient implants During the procedure, the tandem is first inserted (Figure 1A), the TARGIT-FX is then slid over in position and secured over the tandem (Fig. 1B-C); after the ovoids are placed, needles can be inserted from outside the patient in the selected locations as clinically required (Fig. 1 D). Figure 1E show all the needle potential positions. The procedure time and relevant dosimetric parameters were tracked, as well as usability. <h3>Results</h3> The procedure time with the TARGIT-FX was decreased to 24 min from a benchmark of 29 min with the older TARGIT design (average over 68 implants). The V100% remained similar with 92.2% as compared to the 90.2% TARGIT benchmark, while organs at risk remained within constraints. The main goals of flexibility were achieved as follows: the larger number of needle positions enabled greater customization and live changes during the procedure based on the patient anatomy as visualized on live transrectal ultrasound. The ease of use, in particular the ability to reliably insert and position needles from outside the patient, enabled our medical residents under supervision to confidently perform the entire combined IS/IC implants and even first fraction implants. In addition, the new design enabled in one particular case the addition of a needle after the initial procedure, following the planning CT, as the needle could be inserted from outside with the patient lying on the CT table in scanning position. The reliability and consistency of needle placement with the new design may further increase speed since ultrasound imaging during the procedure may be reduced or omitted. <h3>Conclusion</h3> The 3D printed TARGIT-FX enables simple, fast and reliable interstitial needle insertion for combined tandem and ovoid and IS implants. The flexibility of the design enables new or less experienced users to improve the degrees of freedom and dosimetry of their combined IC/IS implants.