Effect of contrast agent on the incidence of ultrasound-induced lung hemorrhage in rats

Abstract

The objective is to test further the hypothesis that if inertial cavitation in the vasculature of the lung is the physical mechanism responsible for ultrasound-induced lung hemorrhage, then the addition of cavitation nuclei to the blood will enhance the occurrence of lung hemorrhage. A factorial design was used to study the effects of two types of injected agents (IA; 0.25 mL per rat of saline or Optison given intravenously) and two levels of pulsed ultrasound exposure (UE; in situ peak rarefactional pressures of 2.74 and 5.86 MPa) on the incidence and size of lung lesions. Ten 10-to-11-week-old Sprague–Dawley rats were exposed at each of the four combinations of IA and UE at 3.1 MHz for 10 s (1-kHz PRF, 1.2-microns PD). Rats administered contrast agent prior to exposure did not have an increase in lesion occurrence or size compared to rats that received saline with no contrast agent. These results provide further evidence that the mechanism of lung hemorrhage is not inertial cavitation. These findings are consistent with another group’s results from another species (mouse) showing no increase in the area of lung hemorrhage using a different contrast agent (Albunex) when exposed to pulsed ultrasound. [Work supported by NIH Grant No. R01EB02641.]