Assessment of renal oxygenation during partial nephrectomy using hyperspectral imaging

Purpose: DLP® hyperspectral imaging is a technology that can be used to construct a highly sensitive, noninvasive, real-time tissue hemoglobin saturation map. This almost video rate technology may be a tool to monitor renal perfusion/oxygenation during hilar occlusion and kidney recovery. We describe our initial experience using hyperspectral imaging to assess renal hemoglobin saturation parameters during open partial nephrectomy for renal cortical tumors in humans. Materials and Methods: Hyperspectral images were collected intraoperatively during open partial nephrectomy. The kidney was actively illuminated using a hyperspectral imaging camera with visible light consisting of a chemometrically predetermined spectrum (520 to 645 nm) for hemoglobin. Spectroscopic reflectance images were captured by a focal plane array, which were digitally processed to visualize the percent of oxyhemoglobin at each image pixel. Results: Hyperspectral imaging was done in 21 patients with a mean age of 56 years who were undergoing partial nephrectomy. Mean clamp time was 37.0 minutes. Median baseline percent of oxyhemoglobin in all patients was 74.6%. Hyperspectral imaging revealed a median 20.0% decrease from normalized pre-occlusion baseline at a median 10.3 minutes of hilar occlusion, where it plateaued for the duration of kidney ischemia. Upon reperfusion the percent of oxyhemoglobin returned to baseline at a median of 5.8 minutes. Conclusions: Hyperspectral imaging is a real-time noninvasive method to assess renal oxyhemoglobin saturation intraoperatively throughout the kidney. A nadir percent of oxyhemoglobin is attained within 10 minutes of hilar occlusion. This knowledge may allow future surgical or pharmacological interventions that titrate or minimize ischemic injury in real time.