COOLING SYSTEM PERMITS EFFECTIVE TRANSCUTANEOUS ULTRASOUND CLOT LYSISIN-VIVO WITHOUT SKIN DAMAGE

Previous in vivo studies have shown that transcutaneous ultrasound enh ances clot dissolution in the presence of either streptokinase or micr obubbles. However, ultrasound-induced skin damage has been a major dra wback. The objective was to evaluate the effect of a cooling system to prevent the skin damage that has heretofore been associated with tran scutaneous low-frequency high-intensity ultrasound clot dissolution. A fter thrombi were induced in both iliofemoral arteries in 15 rabbits, streptokinase (25,000 U/kg) was given intravenously and dodecafluorope ntane was injected slowly (2 mL/15 min) through an infusion catheter i nto the abdominal aorta. One iliofemoral artery was randomized to rece ive ultrasound treatment, and the contralateral artery was treated as a control (receiving streptokinase and dodecafluoropentane alone). In six rabbits (group 1), the skin below the ultrasound transducer was pr otected by the use of a balloon cooling system, and in the other nine rabbits (group 2), ultrasound was used without a cooling system. Seven of nine (78%) arteries treated without the cooling system, and six of six (100%) arteries treated with the cooling system were angiographic ally recanalized after ultrasound; streptokinase + dodecafluoropentane treatment. Thermal damage was present in the skin and soft tissues of all nine rabbits treated without a cooling system. However, the skin and soft tissues were grossly and histologically normal in the six rab bits in which the transcutaneous ultrasound was used with the cooling system. Low-frequency, high-intensity ultrasound energy can be deliver ed transcutaneously for clot dissolution without concomitant tissue da mage when coupled with the use of a cooling system to prevent thermal injury.