An Optimized Miniaturized Ultrasound Transducer for Transcranial Neuromodulation
Chenxue Hou, Yan Wu, Chunlong Fei, Zhihai Qiu, Zhaoxi Li, Xinhao Sun, Chenxi Zheng, Yintang Yang
Frontiers in Neuroscience 2022 · 10.3389/fnins.2022.893108
Abstract
Transcranial ultrasound stimulation (TUS) is a young neuromodulation technology, which uses ultrasound to achieve non-invasive stimulation or inhibition of deep intracranial brain regions, with the advantages of non-invasive, deep penetration, and high resolution. It is widely considered to be one of the most promising techniques for probing brain function and treating brain diseases. In preclinical studies, developing miniaturized transducers to facilitate neuromodulation in freely moving small animals is critical for understanding the mechanism and exploring potential applications. In this article, a miniaturized transducer with a half-concave structure is proposed. Based on the finite element simulation models established by PZFlex software, several ultrasound transducers with different concave curvatures were designed and analyzed. Based on the simulation results, half-concave focused ultrasonic transducers with curvature radii of 5 mm and 7.5 mm were fabricated. Additionally, the emission acoustic fields of the ultrasonic transducers with different structures were characterized at their thickness resonance frequencies of 1 MHz using a multifunctional ultrasonic test platform built in the laboratory. To verify the practical ability for neuromodulation, different ultrasound transducers were used to induce muscle activity in mice. As a result, the stimulation success rates were (32 ± 10)%, (65 ± 8)%, and (84 ± 7)%, respectively, by using flat, #7, and #5 transducers, which shows the simulation and experimental results have a good agreement and that the miniaturized half-concave transducer could effectively converge the acoustic energy and achieve precise and effective ultrasonic neuromodulation.
Abstract via europepmc.
Exposures
Exposure 1: Half-concave miniature transducers (#5, #7.5) and flat control, mouse motor cortex
Target: primary motor cortex — “primary motor cortex”
Device: custom-built · half-concave dimpled pic255 single-element transducer, 5 mm diameter ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 400 | ✓✓✓⚑ |
| Pulse duration (ms) | not reportedimplied by duty cycle ÷ PRF: 0.4 ms (not stated by the paper) | |
| Pulse repetition frequency (Hz) | 1,000 | ✓✓✓ |
| Duty cycle (%) | 40 | ✓✓✓ |
| Sonication duration (s) | 0.2 | ✓✓✓⚑ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported | |
| Pressure, domain unspecified (kPa) | 1,600 | ✓✓✓⚑ |
Sonication parameters were PRF 1 kHz, 40% duty cycle, 200 ms per trial; 20 trials per animal. Pulse duration not stated; whether the 200 ms is the whole train is not spelled out.
Flags from extraction
exposures[0].fundamental_frequency_khz— Abstract says transducers were characterised at their thickness resonance of 1 MHz, but the methods and acoustic measurements state 400 kHz; the stimulation frequency in the mouse experiment is not stated separately.exposures[0].unspecified_domain.pressure_kpa— 1.6 MPa appears only in a figure legend with no domain stated; same value reported for all transducers.exposures[0].timing.sonication_duration_s— 200 ms is listed unlabelled alongside PRF and duty cycle; read as train duration (latency window is also 200 ms).sham_type— Figure 9 legend shows a sham condition; its mechanism is not described.exposures[0].device.family— Transducers fabricated in-house from pic255 ceramic; no maker of the finished transducer named.