THE EFFECT OF ULTRASOUND ON MICROVASCULAR HEMODYNAMICS IN SKELETAL MUSCLE " EFFECT ON ARTERIOLES

Abstract--A skeletal muscle model (rat cremaster muscle) has been described for the evaluation of ultrasonic bioeffects on the microscopic vasculature. One MHz pulsed ultrasound (mark-space 100tzsec:100/~sec) was administered to the tissue at 1.25, 2.5, 5.0 and 10.0Wcm-2 (temporal average) while continuously measuring lumen diameter, volume flow, and rate of vasomotion (intrinsic cyclic constriction and relaxation) in three different sizes of arterioles (100, 50, 30 #m inner diameter). No change in these parameters was noted at intensities below 5 Wcm-2. Above 5 Wcm-2 there was a 25 % decrease in diameter and a 44 % decrease in volume flow in the smallest arterioles observed, as well as a 29 % decrease in flow in the largest arteriole feeding the tissue. The rate of vasomotion i the smallest arterioles increased 20x in the same intensity range. None of these effects or their magnitude could be attributed to simple tissue heating in the same temperature ange t34-36.5°C) as obtained with ultrasound exposures