Transcranial ultrasound modulation

Ultrasound neuromodulation is a promising technology for probing brain function and treating brain dysfunction given its non-invasiveness and high spatiotemporal resolution. Recent years have witnessed rapid advances in this field including both stimulatory and inhibitory effects in cortical and subcortical brain regions. This chapter summarizes the basic physics and recent findings on the mechanisms of ultrasound neuromodulation and experimental applications in cell and tissue preparations, rodents, large animals, non-human primates, and humans. The ultrasound hardware is briefly described, as well as the major relevant tradeoffs in pulse parameters. Safety data as well as general considerations and limitations for using ultrasound for neuromodulation are also discussed.

Acousto optic imaging beyond the acoustic diffraction limit using speckle decorrelation

Acousto-optic imaging (AOI) enables optical-contrast imaging deep inside scattering samples via localized ultrasound modulation of scattered light. However, the resolution in AOI is inherently limited by the ultrasound focus size, prohibiting microscopic investigations. In recent years advances in the field of digital wavefront-shaping allowed the development of novel approaches for overcoming AOI’s acoustic resolution limit. However, these approaches require thousands of wavefront measurements within the sample speckle decorrelation time, limiting their application to static samples. Here, we show that it is possible to surpass the acoustic resolution-limit with a conventional AOI system by exploiting the natural dynamics of speckle decorrelations rather than trying to overcome them. We achieve this by adapting the principles of super-resolution optical fluctuations imaging (SOFI) to AOI. We show that naturally fluctuating optical speckle grains can serve in AOI as the analogues of blinking fluorophores in SOFI, enabling super-resolution by statistical analysis of fluctuating acousto-optic signals.

A nanoparticle enabled focused ultrasound-stimulated magnetic resonance imaging spotlight

Periodic high-intensity focused ultrasound modulation of a nanoparticle generates reversible MRI T1 relaxivity changes at the 1.5 mm3 focal point. A modulation enhancement map spotlights the region of interest by increasing contrast almost 100-fold.