2.
The percentage of glomerular capillary hemorrhage (GCH) from histology for the different ultrasound frequency sources, each plotted as a function of the peak rarefactional pressure amplitude (PRPA). Typically, the bioeffect increased rapidly above an apparent threshold both for diagnostic ultrasound (DUS) exposure and for laboratory system (LAB) exposure. For the DUS at 5.0 MHz and 7.4 MHz, no GCH was induced even for the highest available PRPA. For the LAB at 7.5 MHz, the GCH was not significant for the histological evaluation (although GCH was evidenced by blood filled tubules grossly visible on the surface of the kidneys).