The evolution of near infrared spectroscopy in urology

Abstract

In the 50 year history of NIRS, biomedical applications in urology are recent. This review summarizes technical advances and novel enquiry that have led to hemodynamic monitoring of the testis, measures of renal function, evaluation of the pelvic floor in women, and interrogation of the bladder. An overview is given of how bladder spectroscopy has evolved and the evidence that non-invasive transcutaneous optical monitoring of the anterior bladder wall now enables variations in the organ's hemodynamics and oxygen supply and demand to be identified in real time. Research indicates that bladder blood flow and oxygenation differ in health and disease, and because NIRS monitors changes in the microcirculation bladder spectroscopy adds physiologic information not available by other means, including via the current invasive method for evaluation of voiding dysfunction. Confidence that bladder NIRS yields physiologic data comes from the patterns of chromophore change and tissue oxygen saturation observed corresponding to variations in these parameters in NIRS studies of other tissues in response to known physiologic events. Importantly, when interpreted based on this prior research, novel insight is gained about probable causal pathologies underlying bladder dysfunction. Studies to date warrant further research, continued refinement of instrumentation, extension of the scope of monitoring, and exploration of diagnostic software algorithms.

Near-Infrared Spectroscopic Screening for Bladder Disease in Africa: Training Rural Clinic Staff to Collect Data of Diagnostic Quality

“…In this project, the presence of bladder outlet obstruction (BOO) results in a negative trend in O 2 Hb/tHb. We have previously reported on the comparable diagnostic accuracy of NIRS to invasive pressure flow studies for bladder outlet obstruction (88% specificity, 84% precision), also that real time diagnosis is possible through analysis of the NIRS-derived trends of chromophore change using a validated algorithm [23,27,28], and that these concepts remain valid when monitoring the bladder through pigmented skin [18,19].…”

“…The device used in this project evolved through a series of prototypes and custom software upgrades. Design criteria to suit it for use in rural Africa included a "user friendly" interface and operating software intended to make it intuitively operable by anyone familiar with use of technology at the level of an Android cell phone, with core features based on our validated optical method for noninvasive transcutaneous diagnosis of bladder outlet obstruction [23]. The result was a custom-made miniature, self-contained unit with wireless capacity.…”

“…As validated in other biomedical applications using CW NIRS, such chromophore data allow changes in tissue hemodynamics and oxygenation to be inferred [25]; in bladder NIRS, such changes occur as the detrusor muscle contracts during spontaneous voiding [23,26]. The physiologic changes in the microcirculation of the detrusor differ in health and disease and characteristic patterns of change have been described which can contribute to diagnosis [23]. In this project, the presence of bladder outlet obstruction (BOO) results in a negative trend in O 2 Hb/tHb.…”

Development of a near-infrared spectroscopy interface able to assess oxygen recovery kinetics in the right and left sides of the pelvic floor

“…1 Novel optical systems have been applied in urology, including direct measurement of bladder muscle oxygenation and hemodynamics using near-infrared spectroscopy (NIRS). 2 But, for assessment of pelvic floor muscle (PFM) function, which is central to treatment for UI using pelvic floor muscle therapy (PFMT), 3 measurement parameters relating to oxygen recovery kinetics are lacking, yet, in sports medicine such parameters are currently measured using NIRS. [4][5][6] The pelvic floor comprises a layer of muscles that span the floor of the pelvis, and provides a voluntarily control mechanism for maintaining urinary continence.…”

Andrew J. Macnab – An innovator and pioneer in the field of Biomedical Near Infrared Spectroscopy

“…More recently, Andrew has focused on the application of NIRS to study the human bladder, making non-invasive physiological assessment of common and debilitating conditions possible for the first time. This is discussed in his review article published in this issue of the journal [6].…”