Room: Exhibit Hall | Forum 3
Purpose: To evaluate the capability to localize and sterilize a novel nitinol (NiTi) interstitial brachytherapy needle. The needle wall is thin enough, at 100 microns, to support a partially shielded radiation source for rotating shield brachytherapy (RSBT), and it is also mechanically flexible, sterilizable, and compatible with computed tomography (CT) and ultrasound (US) imaging. The needle has the potential to be magnetic resonance (MR)-conditional.
Methods: The nitinol needle prototype with a titanium tip and a 2.1 mm diameter was implanted into a prostate US phantom through a template grid (CIVCO Medical Solutions, Orange City, IA, USA) with 5 mm resolution. A stainless-steel (Bard Inc., Murray Hill, NJ, USA) control needle was also implanted, and the absolute positions and orientations of both needles were known. CT and US images of the phantom were acquired and analyzed. Needle reconstruction accuracy was quantified by comparing the needle tip position and orientation from the CT images to the absolute reference position and orientation. Sterilization capability was assessed by exposing four nitinol cylinders to varying numbers of sterilization cycles and analyzing for any chemical changes on the nitinol surface using electrochemical impedance spectroscopy.
Results: The nitinol needle geometry including the tip was clearly visible and well defined on the US and CT images. The reference and CT agreed within Â±1 mm. The chemical analysis of the sterilized nitinol needle pieces showed presence of an oxide layer of varying thickness depending on the number of sterilization cycles undergone.
Conclusion: The proposed nitinol needle was accurately identified and localized to within Â±1 mm for brachytherapy treatment planning. The stability and composition of the oxide layer created following needle sterilization needs to be investigated further to determine safety of re-use.
Funding Support, Disclosures, and Conflict of Interest: This work was funded by NIH 1R41 CA210737-01. Ryan Flynn has financial interest in pxAlpha, LLC, which is developing a Rotating Shield Brachytherapy product.