Three systems for the localized heating of the spinal cord of the mouse have been evaluated by measuring the temperatures in the spinal canal (Tsp); at a reference location dorsal to the spine (Tdo), and by numerically calculating temperature distributions throughout two-dimensional transverse cross-sections through the middle of the heated region. The systems assessed were water bath heating alone, water bath-rf combination and rf heating alone with oblique, dorsally located electrodes. It has been established that (1) for all systems delta T (where delta T = Tdo-Tsp) decreased throughout a 1 h heating period-this was attributed to changes in blood flow; (2) there existed a considerable variation in the experimental value of delta T, particularly for rf heating. The resulting error in the estimation of Tsp from a measured value of Tdo can be reduced by making use of the observed correlation between delta T and the slope of a temperature decay curve measured at the beginning of the heating period; (3) rf alone best spares adjacent visceral and superficial tissues from significant elevation of temperature.
Animals Body Temperature