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Purpose: To minimize the unwanted radiation exposure to the rectum during radiation therapy of pelvic tumors by physically moving the rectum away from the field of radiation in a minimally invasive method.
Methods: Rectal Retractor is an innovative device which uses Nitinol (NiTi) as a shape memory alloy for a safe and controlled actuation. NiTi has the capability to change its shape to a predefined geometry displacing rectal tissue when a small amount of current is applied. The NiTi actuation system is then embedded in a flexible biocompatible rubber tube that is equipped with an inflatable balloon in the distal portion. A prototype has been fabricated and we have evaluated its performance and safety on a fresh cadaver, measuring the displacement and maximum temperature of the device during the actuation.
Results: The actuation of the device happened in less than 30 seconds with temperature remaining around 40OC. Temperature levels were confirmed with both mathematical modeling using COMSOL differential equation solver package and measurement using thermocouple. Comparison of the CT scan images of the fresh cadaver test confirmed that the rectal retractor prototype was able to move the rectum away from the prostate as seen in support document CT scan by as much as 1.6 cm.
Conclusion: This work proposed a Rectal Retractor device which is able to reduce side effects of the radiation therapy in all pelvic tumors in vicinity of rectum by creating a physical distance between the rectum and the field of radiation. It is minimally invasive to apply and gets to its full extension in less than one minute. This device can be used as a reliable solution to sparing the rectum as an OAR, and offers numerous other advantages in radiation therapy applications of pelvic cancers, including the ability to allow higher dose delivery.