Blood flow occlusion in vivo using a single high intensity focused ultrasound exposure is investigated. A high power 1.7 MHZ, 150 mm focal length, piezoelectric ultrasound transducer was used to expose femoral vesels to free field spatial peak intensities in the range 750-4660 Wcm"2whilst being moved at constant speed. Pre-and post-FUS exposure, submillimetre resolution magnetic resonance datasets were squired using a Siemens Vision System (1 .5~, with and without contrast agent administration.

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... me minimum dose for reliable occlusion was 1200 Wcm-2. We believe this effeet can be exploited to treat conditions where alternative invasive treatments have high associated risks of mortality and morbidity.