The mechanical and thermal effects of focused ultrasound can induce vasoconstriction, the reduction of blood vessel diameter, either temporarily or permanently.
Clinically, this could be used to treat vascular malformations or to block the downstream flow of blood in order to deprive tumors of nutrients.
When exposed to ultrasonic pulses of very short durations, blood vessels have been shown to constrict, though the mechanism is not well known. In preclinical studies, this vasoconstriction slowly reduced over a period of up to two weeks after the vessels had been affected by ultrasound. This temporary vasoconstriction occurs with minimal thermal effects, indicating that the mechanical activity of the ultrasound is most likely responsible for inducing the physiological change.
Alternatively, by utilizing the thermal effects of focused ultrasound, it has been proposed that superficial venous insufficiency – a disorder caused by valvular incompetence in the venous system – could be treated by shrinking the intermediate fibers, namely collagen, in the endothelial lining. In one preclinical study, focused ultrasound was used to cause vasoconstriction in the great saphenous vein, correcting the insufficiency.
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