On minimal focal distance of a focused ultrasound probe for neuromodulation.

Authors: Chu YC, Ho CY, Chuo Y, Wu HH, Wang JL

Focal distance is a key parameter for a focused ultrasound probe, especially in mouse brain stimulation where targets are right below the skull. A closed-form solution for the minimal focal distance with a given transducer size was derived in this study to facilitate precise focal spot alignment with targets in the mouse brain. The spherical profile corresponding to the minimal focal distance does not produce accurate focusing. An iterative algorithm based on Snell's law was introduced for lens profile calculation. With a suitable step size, an accurate lens profile can be obtained for the minimal focal distance.

Introduction

Purpose Transcranial ultrasound stimulation

Study Objective To determine the minimal focal distance of a focused ultrasound probe that still enables effective neuromodulation.

Disease model healthy

Targeted brain region(s) choroid plexus

Cargo name and characteristics Focused ultrasound (FUS) — a physical/acoustic neuromodulation modality delivered by a focused ultrasound probe; not a biological cargo (no AAV/protein/small molecule/nanoparticle), delivers focused acoustic energy to neural tissue

Outcomes and Safety

Brain Region

Ultrasound Parameters

Ultrasound instrument PZT transducer

FUS Frequency 3 MHz

Focal Characteristics No details about focal size, focal depth, or beam diameter are reported in the text.

Treatment frequency unclear

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