Simultaneous functional near infrared spectroscopy of the brain and bladder

Background: Worldwide >2.3 billion individuals are affected by bladder disease. The current evaluative test is invasive, associated with complications and often declined. Non-invasive evaluation of bladder hemodynamics using continuouswave near-infrared spectroscopy (NIRS) is an established technique. Recently, fNIRS was shown to detect activity in the brain regions previously identified by fMRI to relate to bladder sensation and control of voiding. We now report a system for simultaneous wireless fNIRS measurements of bladder and brain. Method: Two dual-wavelength (760/850 nm) fNIRS systems were used in parallel. A 23-channel array (35 mm interoptode distance) housed in a neoprene cap was positioned over the bilateral frontal cortex, and a 4-channel grid of 4 emitters and 1 detector taped to the skin over the bladder. Natural bladder filling to capacity and spontaneous voiding were monitored in two volunteer subjects. Proprietary software (Oxysoft v3.2.56) linked the devices, and generated video and graphical displays of changes in oxygenated, de-oxygenated, and total hemoglobin from raw optical data recorded at 50 Hz. Results: Simultaneous brain and bladder data were captured in both subjects. Localized brain activity was evident on video as topographical colorimetric changes indicative of increases in oxyhemoglobin concentration in areas previously linked via fMRI to bladder sensation and function; signal intensity varied in relation to phases of voiding. In the bladder detrusor muscle oxyhemoglobin increased prior to permission to void; changes during uroflow differed between the symptomatic and asymptomatic subjects. Conclusion: Simultaneous wireless fNIRS of brain and bladder is feasible, and offers new physiological dimensions for evaluating bladder control and function.