Effects of Ultrasound on the Cells of the Vascular Wall

Ultrasound is used both to image structures within the body and to treat damaged tissues. There have been many investigations into the safety of ultrasound, with very positive outcomes, but the mechanisms by which it exerts beneficial effects are largely unexplained. We have recently observed a new phenomenon that ultrasound of low therapeutic intensity causes arteries to contract. The effect is reversible and arises from a direct interaction of ultrasound with the cells, rather than from damage to the tissue. This behaviour has implications for assessment of both the safety of ultrasound and its therapeutic effects. We therefore propose to investigate the phenomenon in greater detail. First we propose to establish exactly how the pattern of ultrasound exposure determines the magnitude of the effect. We shall then investigate whether some vessels are more sensitive than others: there is reason to believe, for example, that the small vessels determining the delivery of blood to specific organs might particularly responsive. This would have considerable physiological implications and such information is essential for assessing biological effects. Finally we shall attempt to establish the mechanisms through which ultrasound exerts its effects on the cells. This knowledge could be clinically important in finding ways of either preventing or stimulating the response as required