Development of a Wearable, Portable Broadband Near-Infrared Spectroscopy System for In-Vivo Measurements of Oxygenation and Metabolism

Tissue oxygenation and metabolism measurements are vital for the detection and prognosis of injury and disease. Broadband near-infrared spectroscopy (bNIRS) can non-invasively quantify changes in oxygenated and deoxygenated haemoglobin (∆[HbO], ∆[HHb]) and oxidised cytochrome-c-oxidase (∆[oxCCO]), providing complementary haemodynamic and mitochondrial information. However, most wearable NIRS systems cannot resolve oxCCO due to limited wavelength sampling, while laboratory bNIRS platforms that acquire hundreds of wavelengths are typically bulky and difficult to deploy clinically. This thesis describes the design and implementation of microCYRIL, a dual-channel, fibreless bNIRS system for wearable measurement of oxygenation and metabolism. microCYRIL integrates a miniature spectrometer (Hamamatsu C14384MA; 640–1050 nm, ∼14 nm FWHM resolution) with doped NIR-phosphor high-power LEDs to generate broadband illumination without quartz–tungsten–halogen sources or active cooling. The complete system is under 500 g and alternates measurements at 3 cm and 6 cm source–detector separations to provide complementary superficial and deeper sensitivity. Performance was evaluated in phantom and in-vivo experiments. In a blood phantom with oxygen displaced by nitrogen, microCYRIL recorded a decrease in [HbO] of 23.46 µMol with an increase in [HHb] of +24.56 µMol, while [oxCCO] remained negligible (+0.05 µMol). In a yeast respiration phantom, deoxygenation produced 18.00 µMol ∆[HbO], +22.60 µMol ∆[HHb], and a sustained metabolic change of 2.85 µMol ∆[oxCCO]. Finally, microCYRIL was deployed in a proof-of-concept patient study for transabdominal placental monitoring in seven expectant mothers (36–40 weeks gestation). Following a protocol revision increasing the 6 cm integration time from 1000 ms to 5000 ms, successful acquisitions were obtained in six participants, with ultrasound-measured skin-to-placenta depth of 1.69 ± 0.89 cm. These results demonstrate feasibility of wearable oxCCO-enabled monitoring of placental oxygenation and metabolism at the point of care.