We will develop Raman tomography, a non-invasive platform technology, for the recovery of spatial and spectral information from live animals and human subjects. Raman tomography will provide measurements of bone quality at depths of up to 1 cm below the skin. Available quality indicators will include mineral/matrix ratio, mineral crystallinity and carbonate/phosphate ratio and collagen-fibril cross-link state. The technology requires only a CW laser, an imaging spectrograph and CCD detector. Two specially designed fiber optic probes that provide shaped and distributed laser light to excite spectra and an array of 50 or more collection fibers to recover spectra will be used. Guided by tissue optics measurements, a ring/disk probe will be developed for rapid, deep tissue spectroscopy. Similarly, a tomographic probe will be developed for recovery of spectroscopic images. Modified versions of proven chemometric and tomographic signal recovery algorithms will be used to recover spectra and bone quality indicators. We will investigate trade-offs among signal acquisition time, depth penetration and spatial/spectral detail. Optimized probes will be used to study fracture healing in wild type mice and brtl, a model of osteogenesis imperfecta type IV.. Studies will be performed on live anaesthetized mice and on excised limbs from animals sacrificed at four time points in the eight week tissue regeneration period. Excised limbs allow validation by direct measurement of dissected, sectioned tissue. Porcine models will be used as models for human subjects, because of similarities of skin and tendon optics, allowing progression to Raman tomography of cadaveric tibial and distal radius tissue. Finally, we will demonstrate application to human subjects using arthroplasty patients whose bone tissue is exposed during surgery, allowing measurement validation. Although the focus of this project is on bone tissue, the technology is broadly applicable. Relevance to public health: Raman tomography provides new information for assessment of bone quality and fracture risk unavailable by DEXA or micro-MRI. The instruments used are small, safe and non-invasive, requiring only that a laser light be shined on the subject's skin. The technology is also readily adapted to measurement of other important health indicators, including presence and extent of atherosclerotic plaque and levels of serum cholesterol.
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