Histological examination of focused ultrasound effects on human brain tissue

Of recent interest in neuromodulation is the use of Low Intensity Focused Ultrasound [1] (FUS), itself a topic of significant interest and of several experiments conducted recently in humans with FUS [2,3]. The FDA Guidance on acoustic output for diagnostic ultrasound limits the derated spatial-peak temporal-average ultrasound intensity (ISPTA.3) to 0.72 W/cm2. Much of the human neuromodulation work has been conducted at this limit [2]. However, as this threshold was established principally for diagnostic, as opposed to therapeutic ultrasound, some groups have conducted research at higher intensities [4], upwards of 6.16 W/cm2 to understand better what range of intensities is most effective for neurostimulation.