Assessing the efficacy of near-infrared imaging for evaluation of intraoperative flap oxygenation in hypospadias reconstructive surgeries

Hypospadias is a common pediatric genital defect characterized by incomplete development of the ventral penile tissue. This often results in the urethral opening being more proximal than normal, and may affect urination, sexual function, fertility, and social life. Hypospadias is generally treated with a complex reconstructive procedure whereby donor tissue is transferred from the patient to correct abnormalities in the urethral plate, prepuce, or deeper structures. Successful tissue transfer depends on maintenance of a robust vascular supply, as inadequate perfusion can result in suboptimal outcomes, such as poor healing or urethral fistula. The donor tissue blood supply is currently evaluated by visual examination performed by the surgeon. This is a subjective measure and can be confounded by surgical experience, creating a need for an objective intraoperative method for assessing penile tissue oxygenation and viability. Near-infrared imaging (NIRI) is a non-invasive, non-contact optical imaging technique that leverages the differential absorption properties of hemoglobin in its oxygenated and deoxygenated forms to compute the microvascular tissue oxygen saturation (StO2). We applied a handheld NIRI device that is focused 30cm from the imaging site to evaluate how penile tissue oxygenation evolves throughout the surgical intervention. The ventral and dorsal aspects of the penis were imaged during critical surgical steps, such as before and after urethroplasty. For all images, the anatomical region of interest was segmented in MATLAB and its average oxygenation was calculated. Time-series oxygenation data shows that surgical manipulation of the ventral aspect of the penis to correct meatal displacement indeed increases oxygenation. Mobilization of a coverage flap from the dorsal aspect slightly reduces its oxygenation, though not to an appreciable extent.