2.5. Near infrared spectroscopy (NIRS)

NIRS is a functional imaging technology that measures changes in blood flow that occur during voiding. It enables non-invasive evaluation of oxygen-dependent hemodynamic changes and works on the premise that reactive hyperaemia occurs with voiding.

Oxy-haemoglobin and deoxy-haemoglobin (HHb) respectively represent oxygen supply and consumption of the tissue. The sum of oxy-haemoglobin and HHb represents the total blood perfusion of the tissue [49], [50], [51]. NIRS measures changes in the hemoglobin concentration and oxygen consumption in biological tissues, mainly from the venous blood compartment [52], [53].

Farag et al. developed a classification model that successfully classified 89% of patients with 89.3% sensitivity, 87.5% specificity, 96.3% PPV and 87.5% NPV for BOO (AUC: 0.96) [54]. However another study showed no significant correlation between NIRS and BOO with an AUC for diagnosing BOO at 0.484 [55].