Acoustic holograms for transcranial focusing of arbitrary ultrasonic fields into the brain

Abstract

We design 3D printed lenses that generate acoustic holograms correcting the aberrations of the skull and producing ultrasonic fields with the shape of brain structures. Using experimental techniques on a human skull phantom (HSP), a multiple-point focusing lens is designed to simultaneously focus at both human hippocampi; 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 shapes 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 at the lens surface. Lens height is obtained assuming each element to vibrate as a Fabry-Pérot resonator. Resulting lenses are 3D printed with SLA techniques. The three studied cases show similar results in simulation and experiment with and without the HSP: for the multi-focal beam, the reconstructed field accurately matches the target foci; for the curved trajectory beam, the holographic lens reconstructs the target acoustic image; for the broad focus beam, results present the same qualitative performance and provide 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{Jimenez-GambinJimenezBenllochEtAl2019,
 author = {Sergio Jiménez-Gambín and Noé Jiménez and José María Benlloch and Francisco Camarena},
 booktitle = {ISTU 2019: 19th International Symposium for Therapeutic Ultrasound. Barcelona, Spain. 13-15 June},
 editor = {Conference proceedings},
 isbn = {ISBN: 978-84-87985-30-4},
 month = {6},
 organization = {International Society for Therapeutic Ultrasound},
 pages = {197},
 publisher = {European Focused Ultrasound Charitable Society},
 series = {Poster},
 title = {Acoustic holograms for transcranial focusing of arbitrary ultrasonic fields into the brain},
 year = {2019}
}