In-vivo measurement of CNS tissue oxygenation and metabolism is critical in health and disease. Broadband-near infrared spectroscopy is a non-invasive optical technique which measures tissue oxygenation, haemodynamics and metabolism through in-vivo quantification of concentration changes of oxy- and deoxy-haemoglobin (Δ[HbO2] and Δ[HHb]) and oxidised cytochrome-c-oxidase (Δ[oxCCO]). Current commercially available NIRS systems only use a few wavelengths to measure concentration change that fails to provide accurate Δ[oxCCO] measurement. Broadband-NIRS instruments however, use more than 100 wavelengths which enables quantification of change in [oxCCO], an important marker of cellular oxidative metabolism. These systems tend to be bulky, requiring extensive calibrations and trained staff to operate them; making them less versatile and difficult to be adapted in the clinical environment. Furthermore, existing broadband-NIRS systems quantify chromophore concentration changes assuming a fixed optical pathlength across all the subjects using a previously measured DPF (differential pathlength factor) with time or frequency domain systems. This thesis describes the development of a portable broadband-NIRS system called mini-CYRIL “CYtochrome Research Instrument and appLication”, based on easily sourced components. A miniature white light source (HL-2000-HP) and miniature spectrometers (QE65pro and Ventana VIS-NIR) by Ocean Optics were customised for measuring CNS tissue oxygenation and metabolism. While having the features of commercially available NIRS systems in terms of portability, ease of use and no need for wavelength calibration, in terms of performance mini-CYRIL is comparable to broadband-NIRS instruments providing reliable Δ[oxCCO] measurements that have been validated and assessed through in-vivo tissue studies in (a) preclinical model of: (i) neonatal hypoxic-ischaemic (HI) encephalopathy, (ii) multiple sclerosis (MS) and (iii) low-light level therapy in the aged retina; (b) infants during brain functional activation. Mini-CYRIL is furthermore novel in offering calculation of absolute change in the concentration of chromophores based on real-time measurement of the optical path of light traversing the tissue. None of the current NIRS systems offer this feature which is crucial in case of changing pathology following an injury
