Citation:
Daniel Francis, Jane Hodgkinson, Christopher Walton, Jeremy Sizer, Paul Black, Beth Livingstone, Dawn P. Fowler, Mitesh K. Patel and Ralph P. Tatam. Mid-IR spectroscopic instrumentation for point-of-care diagnosis using a hollow silica waveguide gas cell. Optical Diagnostics and Sensing XVII: Toward Point-of-Care Diagnostics. Photonics West, 27 January - 1 February 2017, San Francisco, CA, USA.
Abstract:
Laser spectroscopy provides the basis of instrumentation developed for the diagnosis of infectious disease, via
quantification of organic biomarkers that are produced by associated bacteria. The technology is centred on a multichannel
pulsed quantum cascade laser system that allows multiple lasers with different wavelengths to be used
simultaneously, each selected to monitor a different diagnostic biomarker. The instrument also utilizes a hollow silica
waveguide (HSW) gas cell which has a very high ratio of interaction pathlength to internal volume. This allows sensitive
detection of low volume gas species from small volume biological samples. The spectroscopic performance of a range of
HSW gas cells with different lengths and bore diameters has been assessed using methane as a test gas and a best-case
limit of detection of 0.26 ppm was determined. The response time of this cell was measured as a 1,000 sccm flow of
methane passed through it and was found to be 0.75 s. These results are compared with those obtained using a multi-pass
Herriot cell. A prototype instrument has been built and approved for clinical trials for detection of lung infection in
acute-care patients via analysis of ventilator breath. Demonstration of the instrument for headspace gas analysis is made
by monitoring the methane emission from bovine faeces. The manufacture of a hospital-ready device for monitoring
biomarkers of infection in the exhaled breath of intensive care ventilator patients is also presented.
