Rjt. Corbett et al., VALIDATION OF A NONINVASIVE METHOD TO MEASURE BRAIN TEMPERATURE IN-VIVO USING H-1-NMR SPECTROSCOPY, Journal of neurochemistry, 64(3), 1995, pp. 1224-1230
The goal of this study was to evaluate the potential of using the diff
erence between the H-1 NMR frequencies of water and N-acetylaspartic a
cid (NAA) to measure brain temperature noninvasively. All water-suppre
ssed and non-water-suppressed H-1 NMR spectra were obtained at a field
strength of 4.7 T using a surface coil. Experiments performed on mode
l solutions revealed a decrease in the difference between NMR frequenc
ies for NAA and water as a linear function of increasing temperature f
rom 14 to 45 degrees C. Changing pH in the range 5.5-7.6 produced no d
iscernible trends for concurrent changes in the slope and intercept of
the linear relationship. There were minor changes in slope and interc
ept for solutions containing 80 or 100 mg of protein/ml versus no prot
ein, but these changes were not considered to be of sufficient magnitu
de to deter the use of this approach to measure brain temperature. The
protein content of swine cerebral cortex was found to remain constant
from newborn to 1 month old (78 +/- 12 mg/g; n = 41). Therefore, data
collected for the model solution containing 80 mg of protein/ml were
used as a calibration curve to calculate brain temperature in eight sw
ine during control, hypothermia, ischemia, postischemia, or death, ove
r a temperature range of 23-40 degrees C. A plot of 61 temperatures de
termined from H-1 NMR versus temperatures measured from an optical fib
er probe sensor implanted 1 cm into the cerebral cortex showed excelle
nt linear agreement (slope = 1.00 +/- 0.03, r(2) = 0.96). We conclude
that H-1 NMR spectroscopy presents a practical means of making noninva
sive measurements of brain temperature with an accuracy of better than
+/-1 degrees C.