A TEST OF THE HYPOTHESIS THAT DIAGNOSTIC ULTRASOUND DISRUPTS MYELINATION IN NEONATAL RATS

Neonatal rats were exposed or sham exposed for 30 min to pulsed ultras ound [2.25 MHz carrier frequency, 1 mu s pulse length, 50 Hz pulse rep etition frequency (PRF), 50 W/cm(2) I-max, 2 mW/cm(2) ITA], euthanised and prepared for electron microscopic analysis of the nodes of Ranvie r of the dorsal and ventral roots of the spinal cord. There was also a cage control. All materials were processed and scored blindly, evalua ting whether perinodal myelin was normal. Rats from all regimens had a reas of disrupted myelination. There was no statistically significant difference among the regimens for absence of myelination. The results did not confirm an earlier report that diagnostic ultrasound disrupts myelination in neonatal rats.