Transcranial acoustic holograms for arbitrary fields generation using focused ultrasound into the brain

Abstract

We present 3D printed holographic lenses that correct the aberrations of the skull and, simultaneously, produce arbitrary ultrasonic fields with the geometry of brain structures. Using experimental techniques on a human skull phantom (HSP), a multiple-point focusing lens is designed to focus at both human hippocampi at once; a beam following an arbitrary curved trajectory, i.e., a self-bending beam; and a holographic plate producing a broad focus that overlaps with the left hippocampus (LH). Skull and LH geometries and acoustic properties are obtained from CT-scans and MRI, respectively. Time-reversal (TR) method is used to obtain the magnitude and phase of the back-propagated field from the target shape towards the lens surface. The holographic lenses are designed assuming each pixel of the lens vibrates as a Fabry-Pérot resonator. The resulting lenses are 3D printed using SLA techniques. The three studied cases show similar results in simulation and experiment with and without the HSP: for the bi-focal beam, the reconstructed field accurately matches the target foci; for the curved trajectory beam, the target acoustic image is reconstructed by the designed holographic lens; for the broad focus beam, results present the same qualitative performance providing a similar overall covering of the LH. The reported holographic lenses can be used to control the spatial features of ultrasonic beams inside the skull in an unprecedented manner using single-element ultrasonic sources.

@inproceedings{JimenezICA2019,
 author = {Sergio Jiménez-Gambín and Noé Jiménez and José María Benlloch and Francisco Camarena},
 booktitle = {ICU 2019: International Congress on Ultrasonics. Bruges, Belgium. 3 - 6 September},
 editor = {Proceedings of Meetings on Acoustics},
 isbn = {ISBN: 978-84-87985-30-4},
 month = {10},
 organization = {KU Leuven},
 publisher = {AIP Publishing},
 series = {Invited},
 title = {Transcranial acoustic holograms for arbitrary fields generation using focused ultrasound into the brain},
 url = {https://kuleuvencongres.be/2019icu},
 year = {2019}
}