Simultaneous multi-target ultrasound neuromodulation in freely-moving mice based on a single-element ultrasound transducer
Jiaru He, Yiyue Zhu, Canwen Wu, Junwei Wu, Yan Chen, Maodan Yuan, Zhongwen Cheng, Lvming Zeng, Xuanrong Ji
Journal of Neural Engineering 2023, 20, 016021 · 10.1088/1741-2552/acb104
Abstract
Objective. Ultrasound neuromodulation has become an emerging method for the therapy of neurodegenerative and psychiatric diseases. The phased array ultrasonic transducer enables multi-target ultrasound neuromodulation in small animals, but the relatively large size and mass and the thick cables of the array limit the free movement of small animals. Furthermore, spatial interference may occur during multi-target ultrasound brain stimulation with multiple micro transducers. Approach. In this study, we developed a miniature power ultrasound transducer and used the virtual source time inversion method and 3D printing technology to design, optimize, and manufacture the acoustic holographic lens to construct a multi-target ultrasound neuromodulation system for free-moving mice. The feasibility of the system was verified by in vitro transcranial ultrasound field measurements, in vivo dual-target blood-brain barrier (BBB) opening experiments, and in vivo dual-target ultrasound neuromodulation experiments. Main results. The developed miniature transducer had a diameter of 4.0 mm, a center frequency of 1.1 MHz, and a weight of 1.25 g. The developed miniature acoustic holographic lens had a weight of 0.019 g to generate dual-focus transcranial ultrasound. The ultrasonic field measurements' results showed that the bifocal's horizontal distance was 3.0 mm, the -6 dB focal spot width in the x -direction was 2.5 and 2.25 mm, and 2.12 and 2.24 mm in the y -direction. Finally, the in vivo experimental results showed that the system could achieve dual-target BBB opening and ultrasound neuromodulation in freely-moving mice. Significance. The ultrasonic neuromodulation system based on a miniature single-element transducer and the miniature acoustic holographic lens could achieve dual-target neuromodulation in awake small animals, which is expected to be applied to the research of non-invasive dual-target ultrasonic treatment of brain diseases in awake small animals.
Abstract via europepmc.
Exposures
Exposure 1: Single-target BBB opening, primary visual cortex (V1)
Target: primary visual cortex — “primary visual cortex (V1, bregma: 2.70 mm, lateral: 2.50 mm)”
Device: custom-built
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 1,100 | ✓✓✓ |
| Pulse duration (ms) | 0.5 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 1,000 | ✓✓✓ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 50% | |
| Sonication duration (s) | 1 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | measurementsingle value | |
| In-situ pressure (kPa) | 1,120 | ✓✓✓ |
| In-situ Isppa (W/cm²) | 32.06 | ✓✓✓ |
| In-situ Ispta (W/cm²) | not reported |
Ultrasound pulse waveform: tone-burst duration (TBD) 0.5 ms, pulse repetition period (PRP) 1.0 ms, sonication duration (SD) 1.0 s trains, inter-sonication interval (ISI) 4.0 s. Total duration of the sonication protocol (TDSP) for single-target BBB opening was 10 minutes, delivered with commercial microbubbles and Evans blue dye injected via tail vein.
Exposure 2: Dual-target bilateral primary somatosensory cortex hindlimb region (S1HL): BBB opening and freely-moving neuromodulation
Target: primary somatosensory cortex — “bilateral primary somatosensory cortex, hindlimb region (S1HL, bregma: 0.70 mm, lateral: 1.50 mm)”
Device: custom-built
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 1,100 | ✓✓✓ |
| Pulse duration (ms) | 0.5 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 1,000 | ✓✓✓ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 50% | |
| Sonication duration (s) | 1 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | measurementsingle value | |
| In-situ pressure (kPa) | 959, 944, 386, 374swept | ✓✓✓ |
| In-situ Isppa (W/cm²) | 27.54, 25.72, 4.28, 3.96swept | ✓✓✓ |
| In-situ Ispta (W/cm²) | not reported |
Same pulse waveform as the single-target exposure (TBD 0.5 ms, PRP 1.0 ms, SD 1.0 s trains, ISI 4.0 s), delivered simultaneously to two foci (bilateral S1HL) via a miniature transducer and acoustic holographic lens. Total duration of the sonication protocol (TDSP) was 10 minutes for the dual-target BBB-opening experiment and 40 minutes for the dual-target freely-moving neuromodulation experiment; in the neuromodulation experiment the sham group had the transducer driving voltage turned off.
Flags from extraction
n_subjects— n_subjects given as the list of ultrasound-exposed group sizes across the three sub-experiments (single-target BBB n=3, dual-target BBB n=3, dual-target neuromodulation stimulated n=3); the paper's overall total of 12 mice includes 3 sham animals never exposed to active ultrasound.exposures[1]— BBB-opening and freely-moving-neuromodulation sub-experiments at the same target/frequency (bilateral S1HL, 1.1 MHz) are combined into one exposure per the target x frequency rule, even though their purposes, pressures and total session durations (10 vs 40 min) differ.in_situ.method— Pressure/intensity fields were measured with a fibre-optic hydrophone 'inside the skull' (transcranial, ex vivo skull present); classified as in_situ measurement rather than free_field.exposures[*].timing.duty_cycle_pct— Paper states pulse repetition period (PRP=1.0 ms) and tone-burst duration (TBD=0.5 ms) but never states a duty cycle percentage; not recorded to avoid computing it from PD/PRP.