Effects of ultrasound and ultrasound contrast agent on vascular tissue

While ultrasound and US contrast agents are widely used, their impact on the physiological response of vascular tissue to vasoactive agents has not been investigated in detail.In the present study, rat dorsal aortas were treated with US via a clinical imaging transducer in the presence or absence of the US contrast agent, Optison. Aortas treated with both US and Optison were unable to contract in response to phenylephrine or to relax in the presence of acetylcholine. Histology of the arteries was unremarkable. When the treated aortas were stained for endothelial markers, a distinct loss of endothelium was observed. Importantly, terminal deoxynucleotidyl transferase mediated dUTP nick-end-labeling (TUNEL) staining of treated aortas demonstrated incipient apoptosis in the endothelium.Taken together, these ex vivo results suggest that the combination of US and Optison may alter arterial integrity and promote vascular injury; however, the in vivo interaction of Optison and ultrasound remains an open question.Ultrasound (US) is widely used clinically: applications include fetal development monitoring [1] and monitoring of cerebral hemorrhages [2]. The clinical use of US contrast agents produces few side effects and the safety profile drives the technology. US contrast agents have been developed to enhance imaging via the generation of echo signals at the tissue-gas interface and following microbubble collapse. Intravascular ultrasound (IVUS) [3] has revolutionized the imaging of coronary circulation and virtual histology is the product of the IVUS imaging. In addition, trans-esophageal echocardiography studies are frequently used to assess ventricular function. Intravascular gene transfer using microbubbles has been achieved, which has the potential to interdict into disease processes via gene therapy [4].Optison is a first generation US imaging agent that is comprised of a suspension of microspheres. These microspheres, 3–4.5 uM in diameter (32 uM maximum), consist of t