Room: AAPM ePoster Library
Purpose: To design a high-dose rate (HDR) brachytherapy catheter immobilizer devices for simply implementation in intra-operative procedures and evaluate the devices ability to reduce catheter displacement.
Methods: At our institution, HDR catheters are currently immobilized using dental putty (which is initially malleable and hardens over time) following free-hand template-free placement. We compare this method, which can be time consuming and inconsistent, to three other catheter immobilizer designs that do not require putty. Autodesk Fusion 360 (Autodesk) was used to develop designs: Design #1 was a rigid body, Design #2 was semi-flexible, and Design #3 was a flexible mesh. Prototypes were developed using polylactic acid (rigid) and thermoplastic polyurethane (flexible) material with a 3D-printer (Creality-Ender3). Each design was tested using a prostate agar phantom (CIRS Inc.) with free-hand inserted catheters – performed by WC with 1 year of training. Using a CT scanner (Siemens Sensation) with image resolution of 0.3x0.3x1mm, images were acquired before and after attempts to disturb catheters from their initial placement. Points near phantom entrance and catheter tip were compared to evaluate each design.
Results: Pre- and post-attempts to cause catheter movement showed <0.5mm displacement for Design #1 (rigid), 0.5mm for Design #2 (semi-flexible) and 2-3mm for Design #3 (flexible-mesh). However, rigidity of Design #1 makes it susceptible in causing movement of peripheral catheters for large surface deformations. Therefore, a semi-flexible design (such as Design #2) was preferred for patient surface conformality while also showing effective catheter immobilization.
Conclusion: We have designed and developed an effective HDR brachytherapy catheter immobilizers for free-hand insertion technique which provide consistent immobilization by reducing user-placement variability. Rigid templates are more prone to movement due to non-planar patient morphology. Moving forward, a semi-flexible design provided enough malleability forming tightly on the patient while providing rigidity to secure the immobilizer with almost no movement.