A Magnetic Resonance-Guided Focused Ultrasound Neuromodulation System With a Whole Brain Coil Array for Nonhuman Primates at 3 T
Ye Li, Jo Lee, Xiaojing Long, Yangzi Qiao, Teng Ma, Qiang He, Peng Cao, Xiaoliang Zhang, Hairong Zheng
IEEE Transactions on Medical Imaging 2020 · 10.1109/tmi.2020.3019087
Abstract
The phased-array radio frequency (RF) coil plays a vital role in magnetic resonance-guided focused ultrasound (MRgFUS) neuromodulation studies, where accurate brain functional stimulations and neural circuit observations are required. Although various designs of phased-array coils have been reported, few are suitable for ultrasound stimulations. In this study, an MRgFUS neuromodulation system comprised of a whole brain coverage non-human primate (NHP) RF coil and an MRI-compatible ultrasound device was developed. When compared to a single loop coil, the NHP coil provided up to a 50% increase in the signal-to-noise ratio (SNR) in the brain and acquired better anatomical image-quality. The NHP coil also demonstrated the ability to achieve higher spatial resolution and reduce distortion in echo-planer imaging (EPI). Ultrasound beam characteristics and transcranial magnetic resonance acoustic radiation force (MR-ARF) were measured for simulated positions, and calculated B 0 maps were employed to establish MRI-compatibility. The differences between focused off and on ultrasound techniques were measured using SNR, g-factors, and temporal SNR (tSNR) analyses and all deviations were under 2.3%. The EPI images quality and stable tSNR demonstrated the suitability of the MRgFUS neuromodulation system to conduct functional MRI studies. Last, the time course of the blood oxygen level dependent (BOLD) signal of posterior cingulate cortex in a focused ultrasound neuromodulation study was detected and repeated with MR thermometry.
Abstract via europepmc.
Exposures
Exposure 1: FUS to posterior cingulate cortex
Target: posterior cingulate cortex — “posterior cingulate cortex (PCC)”
Device: custom-built · custom-designed, homemade MRI-compatible single crystal-based ultrasound transducer ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 300 | ✓✓✓ |
| Pulse duration (ms) | not reportedimplied by duty cycle ÷ PRF: 0.5 ms (not stated by the paper) | ⚑ |
| Pulse repetition frequency (Hz) | 200 | ✓✓✓ |
| Duty cycle (%) | 10 | ✓✓✓ |
| Sonication duration (s) | 1 | ✓✓✓⚑ |
| Free-field pressure (kPa) | 758 | ✓✓✓⚑ |
|---|---|---|
| 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 |
Sine wave, 300 kHz, PRF 200 Hz, pulse duty cycle 10%, stimulus duration 1 s and stimulus duty cycle 50%. Each fMRI stimulation lasted 30 seconds with a 10-second pause after each.
Flags from extraction
n_subjects— Four monkeys used in the study; the paper does not say how many received the PCC neuromodulation session.exposures[0].timing.sonication_duration_s— Protocol does not fit four numbers: stimulus duration 1 s with 50% stimulus duty cycle, within 30 s stimulation periods; 1 s recorded.exposures[0].free_field.pressure_kpa— 758 kPa measured in free field with the peak acoustic pressure settings; the neuromodulation sentence does not restate pressure.exposures[0].timing.pulse_duration_ms— Pulse duration not stated; not computed.direction_of_effect— BOLD increase only; shown in a figure, a technical demonstration.exposures[0].device.family— Homemade transducer; manufacturer not named.