Displacement and functional ultrasound (fUS) imaging of displacement-guided focused ultrasound (FUS) neuromodulation in mice
Seongyeon Kim, Nancy Kwon, Md Murad Hossain, Jonas Bendig, Elisa E. Konofagou
NeuroImage 2024, 298, 120768 · 10.1016/j.neuroimage.2024.120768
Abstract
Focused ultrasound (FUS) stimulation is a promising neuromodulation technique with the merits of non-invasiveness, high spatial resolution, and deep penetration depth. However, simultaneous imaging of FUS-induced brain tissue displacement and the subsequent effect of FUS stimulation on brain hemodynamics has proven challenging thus far. In addition, earlier studies lack in situ confirmation of targeting except for the magnetic resonance imaging-guided FUS system-based studies. The purpose of this study is 1) to introduce a fully ultrasonic approach to in situ target, modulate neuronal activity, and monitor the resultant neuromodulation effect by respectively leveraging displacement imaging, FUS, and functional ultrasound (fUS) imaging, and 2) to investigate FUS-evoked cerebral blood volume (CBV) response and the relationship between CBV and displacement. We performed displacement imaging on craniotomized mice to confirm the in situ targeting for neuromodulation site. We recorded hemodynamic responses evoked by FUS while fUS imaging revealed an ipsilateral CBV increase that peaks at 4 s post-FUS. We report a stronger hemodynamic activation in the subcortical region than cortical, showing good agreement with a brain elasticity map that can also be obtained using a similar methodology. We observed dose-dependent CBV responses with peak CBV, activated area, and correlation coefficient increasing with the ultrasonic dose. Furthermore, by mapping displacement and hemodynamic activation, we found that displacement colocalized and linearly correlated with CBV increase. The findings presented herein demonstrated that FUS evokes ipsilateral hemodynamic activation in cortical and subcortical depths while the evoked hemodynamic responses colocalize and correlate with FUS-induced displacement. We anticipate that our findings will help consolidate accurate targeting as well as shedding light on one of the mechanisms behind FUS modulation, i.e., how FUS mechanically displaces brain tissue affecting cerebral hemodynamics and thereby its associated connectivity.
Abstract via europepmc.
Exposures
Exposure 1: FUS to left/center/right sonication sites at Bregma -0.5 mm (craniotomized cortex-to-subcortex)
Target: primary somatosensory cortex, primary motor cortex, striatum, globus pallidus, thalamus — “left (ML: -1.5 mm), center (ML: 0 mm), and right (ML: 1.5 mm) sonication with the same depth of FUS focus (DV: 3 mm) at Bregma -0.5 mm”
Device: Sonic Concepts · Sonic Concepts · H-215 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 4,000 | ✓✓✓ |
| Pulse duration (ms) | 150, 300swept | ✓✓✓⚑ |
| Pulse repetition frequency (Hz) | not reported | |
| Duty cycle (%) | not reported | ⚑ |
| Sonication duration (s) | 1, 10swept | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | deratingsingle value | |
| In-situ pressure (kPa) | 850, 3,390swept | ✓✓✓⚑ |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
During a session, mice were sonicated 7 times with 25-34 s interval using the 4 MHz FUS. Three FUS parameters (peak negative pressure PNP, sonication duration SD, pulse duration PD) were explored over 13 sessions repeated per target: PNP ranged 0.85-3.39 MPa (SD=10 s, PD=300 ms fixed), SD ranged 1-10 s (PNP=3.39 MPa, PD=300 ms fixed), and PD ranged 150-300 ms (PNP=3.39 MPa, SD=10 s fixed). An amplitude-modulated pulsing regime at 1 kHz AM frequency was used to minimize auditory confounding.
Flags from extraction
exposures[0].target.terms— FUS was targeted by spatial coordinate (ML/DV at Bregma) rather than a single named nucleus; activated structures spanning cortex and subcortex (S1, M1, caudate putamen, globus pallidus, reticular thalamic nucleus, thalamus) are listed based on the paper's activation-map description, not a single stated anatomical target.exposures[0].in_situ.pressure_kpa— Values are derated peak negative pressures ('all peak negative pressure values reported in this study was derated to account for attenuation in brain tissue'), i.e. an in-situ estimate via a derating equation, not a measured or simulated in-brain value.exposures[0].timing.pulse_duration_ms— Text states the PD=150-300 ms range test used 'SD = 10 ms' which is very likely a typo for 10 s (consistent with the SD sweep description elsewhere); recorded as stated in the text.exposures[0].timing.duty_cycle_pct— Paper does not state a numeric duty cycle for the 1 kHz amplitude-modulation pulsing scheme.n_sessions_per_subject— Paper states 13 parameter-combination sessions were repeated per target (3 targets) for the n=4 fUS-imaging cohort, but does not give a single explicit total sessions-per-animal count usable as one number.auditory_control— An audible-tone control (10 kHz, 90 dB) was used to test for auditory confounds in one mouse; this does not match a listed vocabulary term exactly so 'other' is used.