THE EVOLUTION OF FIELD DEPLOYABLE fNIR SPECTROSCOPY FROM BENCH TO CLINICAL SETTINGS

In the late 1980s and early 1990s,Dr.Britton Chance and his colleagues,using picosecond-long laser pulses,spearheaded the development of time-resolved spectroscopy techniques in an effort to obtain quantitative information about the optical characteristics of the tissue.These efforts by Chance and colleagues expedited the translation of near-infrared spectroscopy(NIRS)-based techniques into a neuroimaging modality for various cognitive studies.Beginning in the early 2000s,Dr.Britton Chance guided and steered the collaboration with the Optical Brain Imaging team at Drexel University toward the development and application of afield deployable continuous wave functional near-infrared spectroscopy(fNIR)system as a means to monitor cognitive functions,particularly during attention and working memory tasks as well as for complex tasks such as war games and air tra±c control scenarios performed by healthy volunteers under operational conditions.Further,these collaborative efforts led to various clinical applications,including traumatic brain injury,depth of anesthesia monitoring,pediatric pain assessment,and brain
computer interface in neurology.In this paper,we introduce how these collaborative studies have made fNIR an excellent candidate for specified clinical and research applications,including repeated cortical neuroimaging,bedside or home monitoring,the elicitation of a positive effect,and protocols requiring ecological validity.This paper represents a token of our gratitude to Dr.Britton Chance for his influence and leadership.Through this manuscript we show our appreciation by contributing to his commemoration and through our work we will strive to advance thefield of optical brain imaging and promote his legacy.

Assessment of cerebral oxygenation response to hemodialysis using near-infrared spectroscopy (NIRS):Challenges and solutions

To date,the clinical use of functional near-infrared spectroscopy(NIRS)to detect cerebral ischemia has been largely limited to surgical settings,where motion artifacts are minimal.In this study,we present novel techniques to address the challenges of using NIRS to monitor ambu-latory patients with kidney disease during approximately eight hours of hemodialysis(HD)treatment.People with end-stage kidney disease who require HD are at higher risk for cognitive impairment and dementia than age-matched controls.Recent studies have suggested that HD-related declines in cerebral blood flow might explain some of the adverse outcomes of HD treatment.However,there are currently no established paradigms for monitoring cerebral per-fusion in real-time during HD treatment.In this study,we used NIRS to assess cerebral hemo-dynamic responses among 95 prevalent HD patients during two consecutive HD treatments.We observed substantial signal attenuation in our predominantly Black patient cohort that required probe modifications.We also observed consistent motion artifacts that we addressed by devel-oping a novel NIRS methodology,called the HD cerebral oxygen demand algorithm(HD-CODA),to identify episodes when cerebral oxygen demand might be outpacing supply during HD treatment.We then examined the association between a summary measure of time spent in cerebral deoxygenation,derived using the HD-CODA,and hemodynamic and treatment-related variables.We found that this summary measure was associated with intradialytic mean arterial pressure,heart rate,and volume removal.Future studies should use the HD-CODA to implement studies of real-time NIRS monitoring for incident dialysis patients,over longer time frames,and in other dialysis modalities.