Vascular Occlusion and Hemostasis
Focused ultrasound can be used to close blood vessels, with the potential to provide a noninvasive treatment of internal bleeding or a means of cutting off the blood supply to specific structures, such as tumors.
The heat generated by focused ultrasound can be used for hemostasis (e.g. to control internal bleeding) by thermally closing wounded blood vessels. One preclinical study found that focused ultrasound was able to achieve hemostasis in a punctured femoral artery in all of their test animals with durable, long-term results. Examination of the treated region has shown that the soft tissue surrounding the blood vessel hardens due to adventitia coagulation, creating a seal. This mechanism has many clinical applications including stopping liver hemorrhage, which can be difficult to treat and is a leading cause of death in patients who have had liver trauma.
Alternatively, it has been proposed that the mechanical effects of ultrasound can cause damage to vessel walls which exposes tissue factors. These tissue factors cause a cascade of biological reactions that result in the formation of a blood clot and eventual occlusion of the blood vessel. Furthermore, blood vessel occlusion with focused ultrasound has potential for the treatment of esophageal and gastric varices, arteriovenous malformations, and varicose veins without the risk of distant clot formation or the use of a catheter. It can also provide a noninvasive method to cut off the blood supply to benign or malignant tumors, effectively starving them of vital nutrients and making them more vulnerable to other treatments. Clinical research is ongoing utilizing this method to correct blood flow imbalances in twin-twin transfusion syndrome.
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