Development & Clinical Application of an Arduino-based Functional Near Infrared Spectroscopy (fNIRS)

Monday, January 29, 2024

2:00 PM-4:00 PM

BIOMED PhD Thesis Defense

Title:
Development and Clinical Application of an Arduino-based Functional Near Infrared Spectroscopy (fNIRS)

Speaker:
Ardy Wong, PhD Candidate
School of Biomedical Engineering, Science and Health Systems
Drexel University

Advisor:
Kambiz Pourrezaei, PhD
Professor
School of Biomedical Engineering, Science and Health Systems
Drexel University

Details:
The primary goal of this thesis was to create a low-cost Arduino-based fNIRS system and its use in a variety of clinical settings.  While this system was used for several clinical applications, in this thesis we will focus on two clinical applications: during hemodialysis and during an olfactory test.

To date, the clinical use of functional near-infrared spectroscopy (NIRS) to detect cerebral ischemia has been largely limited to surgical settings. One important limiting factor has been the presence of motion artifacts, particularly during long-term monitoring of ambulatory patients. Here we present novel techniques to address the challenges of using NIRS to monitor ambulatory patients with kidney disease during approximately four 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 perfusion in real-time during HD treatment. In this study, we used NIRS to assess cerebral hemodynamic 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 developing 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.  

Objective assessment of olfactory function has diagnostic and legal value. An odor detection task was designed in which the subject reported the conscious sensing of an odorant via a button press while the hemodynamic activity from the forehead was monitored using a 4-channel fNIRS system. The task consisted of intermingled odor and non-odor trials. We recorded 17 subjects and each of them underwent 60 trials. The time domain analysis of the raw data showed that the hemodynamic activity was statistically different between the odor and non-odor trials especially for oxyhemoglobin in far channels. Pairwise correlation indicated that motor activity had a short-lasting influence on hemodynamic response while the hemodynamic response to different odors were highly correlated over time. In conclusion, we believe that fNIRS monitoring of hemodynamic response could be potentially used for objective assessment of odor detection in cases that subjective report is unreliable.

Contact Information

Natalia Broz
njb33@drexel.edu