Pilot Study Evaluating a Rat Model of Radiation-induced Erectile Dysfunction Using an Image-guided Microirradiator

Objective To establish a feasible rat model of radiation-induced erectile dysfunction after targeted prostate irradiation using an image-guided irradiation unit specially designed for small-animal radiation research. Methods The X-RAD 225Cx research platform was used in the present study. We first performed quality assurance testing using a rat cadaver. After confirming dosimetry, 24 age-matched, young, adult, male rats were assigned to sham radiation or radiation to the prostate with doses of 15, 20, or 25 Gy. To confirm appropriate prostate irradiation, physiological erectile function was evaluated using intracavernous pressure (ICP) measurements with cavernous nerve electrical stimulation at 9 weeks after radiotherapy. Each animal was weighed at the time of ICP measurement. In addition, we investigated the cyclic guanosine monophosphate level in the penile cavernosa using a commercial enzyme-linked immunosorbent assay kit. Results Quality assurance results confirmed the accuracy of the irradiation technique. Dose-dependent decreases in ICP in irradiated rats were observed without major toxicity. No difference in body weight was noted among the experimental groups. Cyclic guanosine monophosphate levels were significantly decreased in the group that received 25 Gy compared with the age-matched sham-irradiated group. Conclusion High-precision imaging and targeting capabilities provided by the micro-IGRT platform enable us to develop a reproducible animal model of radiation-induced erectile dysfunction in prostate cancer research.