Purpose: To physically move the rectum away from the field of radiation through a minimally invasive solution which is compact, reliable, safe, and practical to use.
Methods: This innovative device uses Nitinol (NiTi) as a shape memory alloy for a safe and controlled actuation. Through applying a small amount of current to heat the NiTi wire, the NiTi will be capable of changing shape to a predefined geometry. The actual NiTi wire is fork shaped at distal part to avoid Coccyx bone when moving posteriorly. To assure safety and patient comfort, the NiTi is embedded in a flexible biocompatible rubber tube that is equipped with inflatable balloons in the distal portion to create a V-shape to avoid coccyx bone. A second generation prototype has been fabricated and preliminary cadaver testing is underway to show feasibility of this new design and efficacy.
Results: Our first generation cadaver testing indicated an actuation time of 30 seconds, and a temperature, which plateaued at 40OC. Temperature measurement was confirmed through mathematical modeling using the COMSOL partial differential equation solver package and mechanical measurement using thermocouples. Second generation prototype demonstrated similar behavior through phantom testing. The fork shape design of retractor and expanded balloons are expected to eliminate the blockage by Coccyx bone when the retractor is actuated, creating a desired distance between prostate and the anterior portion of the rectal wall.
Conclusion: A minimally invasive Rectal Retractor device is presented which is capable of physically removing rectal tissue from the vicinity of radiation field. Our fresh cadaver studies show that the device can easily create more than 1.5 cm distance between prostate and rectum. It gets actuated in less than a minute and can be used as a reliable solution to sparing the rectum in external beam and HDR applications of pelvic tumors.