Brain Edema and Intracerebral Necrosis Caused by Transcranial Low-Frequency 20-kHz Ultrasound

Background and Purpose— Ultrasound-accelerated thrombolysis is a promising approach toward acute stroke treatment. In previous in vitro studies, we demonstrated enhanced thrombus destruction induced by 20-kHz ultrasound. However, little is known about biological interactions of low-frequency ultrasound with brain tissue. The aim of this in vivo MRI study was to assess safety aspects of transcranial low-frequency ultrasound in rats. Methods— The cranium of 33 male Wistar rats was sonificated for 20 minutes (20-kHz continuous wave). Power output was varied between 0 and 2.6 W/cm 2 . Tympanal and rectal temperature was monitored. Diffusion-weighted imaging and T2-weighted imaging was performe…