Absolute near-infrared oximetry for urology: A quantitative study of the tissue hemoglobin saturation before and after testicular torsion in a rabbit model

We present an experimental study on four rabbits to demonstrate the feasibility of near-infrared spectroscopy in the non-invasive assessment of testicular torsion. We used a multi-distance frequency-domain method, based on a fixed detector position and a 9-mm linear scan of the illumination optical fibers, to measure absolute values of pre- and post-operative testicular oxygen saturation. Unilateral testicular torsions (by 0 degrees, 540 degrees or 720 degrees) on experimental testes and contralateral sham surgeries (no torsion) on control testes were performed and studied. Our results showed (a) a consistent baseline absolute tissue oxygen saturation value of 78% +/- 5%; (b) a comparable absolute saturation of 77% +/- 6% on the control side (testes after sham surgery); and (c) a significantly lower tissue oxygen saturation of 36% +/- 2% on the experimental side (testes after 540 degrees or 720 degrees torsion surgery). These results demonstrate the capability of frequency domain near-infrared spectroscopy in the assessment of absolute testicular hemoglobin desaturation caused by torsion, and show promise as a potential method to serve as a complement to conventional color and spectral Doppler ultrasonography.