Near-infrared (NIR) spectroscopy is being applied to the solution of problems in many areas of biomedical and pharmaceutical research. The need for modern medical diagnostics to develop small portable instruments that enable fast and effective monitoring of the biological properties of the human body is apparent. We have developed a portable and robust spectrometer that consists of a two beam interferometer operating in the near-infrared wavelength range for real-time measurements. The device has limited spectral resolution and so methods of computational intelligence and advanced signal processing have been applied to the NIR data to produce more precise and informative diagnostic information. Our target application concerns blood and tissue status in a form that can be interpreted directly by the user, without special knowledge of spectral analysis. More specifically, theories and methods from the field of machine intelligence (learning algorithms, neural networks, etc.) were first applied to classify in vitro urea samples of different concentrations. The results are encouraging, with overall mean squared prediction errors of less than 10-4, and in vivo trials will follow to further develop the device. Non-intrusive diagnostics of this kind are suitable for point-of-care screening.
The current demand for versatile medical diagnostics has created a significant increase in the development of NIR spectroscopic techniques due to the relative transparency of body fluids and soft tissue in this spectral region. Specifically the non-invasive determination of blood substrates is a desirable measurement as a guide to the pathological condition of the patient, since blood forms the primary metabolic transport system for the body. There are well-defined needs for real-time near-infrared (NIR) monitoring instruments for in vivo clinical applications. This paper describes a compact and rugged FT-NIR instrument that has the potential to meet this need. A rapid software development environment was used to implement the active alignment, control and self-calibration algorithms. The current prototype has a spectral range of 500 - 2300 nm and collects a spectrum in 200 ms. The instrument has been validated with bandpass filters and water spectra. Hemoglobin (Hb) solutions and erythrocyte suspensions have also been measured. The well known water absorbance features around 1400 nm and 1900 nm have been observed along with HB features around 550 nm and we have verified the published blood spectra.
This paper describes a software development environment suitable for advanced signal processing and feedback control algorithms for interferometry. The significance of software fast prototyping tools is illustrated where theoretically challenging algorithms are to be implemented. Specifically, a case is discussed where advanced control is deemed necessary for reliable operation of FT-NIR instruments in an on-line environment. In this particular case, an interactive test bed for new algorithmic approaches is developed, such that advanced theories and methods can be rapidly tested and validated with the real-world interferometer hardware. This development environment also allows new interfacing concepts with mechanical and optical hardware to be tested. Use of this environment is illustrated for the case of a novel Michelson NIR spectrometer operating in the range 800-2200 nm.