Tissue Temperature by Near-Infrared Spectroscopy

Clyde H. Barlow, Katherine A. Kelly, and Jeffrey J. Kelly

The Evergreen State College, Olympia, WA 98505

C.H. Barlow, K.A. Kelly and J.J. Kelly  (1995)  Tissue temperature by near-infrared spectroscopy.  In Optical Tomography, Photon Migration, and Spectroscopy of Tissue and Model Media, (eds. Chance, B. and Alfano, R.R.), SPIE, 2389:818-828. Optical determinations of tissue temperature by near-infrared (NIR) spectroscopy provides the basis for measuring localized changes in tissue metabolism associated with cognition, mechanical work, inflammation or malignancy. Absorbance changes in NIR spectra of tissue water are shown to correlate with tissue sample temperature. Digital tissue transmission spectra (700-1600nm) of samples 1-5 mm thick of bovine and avain muscles were obtained over temperatures ranging from 17 to 45C. Reflectance spectra (800-2000nm) were obtained from blocks of porcine muscle over the temperature range 14 to 46C.

Multilinear regression analysis of the correlation between absorbance or reflectance and tissue temperature demonstrated that each O-H bond overtone spectral region (960, 1200, 1450 and 1920nm) has a high correlation with tissue temperature. Transmission results gave Standard Error of y Estimates (SEE) and Standard Error of Prediction (SEP) form cross-validation analysis of 0.02 to 0.12C for SEE (R2>0.999) and 0.04 to 0.12C for SEP (R2>0.999). Reflectance results gave SEE's of 0.06 to 0.24C.

Combinations of O-H vibrational modes of water give rise to NIR absorbance in solution and tissue. The spectra show a regular shift to shorter wavelength absorbance as temperature increases. Such shifts may be due to decreasing hydrogen-bonding with increasing temperature. These studies have established that the temperature dependent changes in water NIR spectra can be utilized to evaluate tissue temperature with precision and accuracy.

Keywords: muscle, temperature, water, near infrared, spectroscopy

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Last modified: 01/08/2000