Model-based correction of rapid thermal confounds in fluorescence neuroimaging of targeted perturbation
Neda Davoudi, Hector Estrada, Ali Özbek, Shy Shoham, Daniel Razansky
Neurophotonics 2024, 11 · 10.1117/1.nph.11.1.014413
Abstract
Significance An array of techniques for targeted neuromodulation is emerging, with high potential in brain research and therapy. Calcium imaging or other forms of functional fluorescence imaging are central solutions for monitoring cortical neural responses to targeted neuromodulation, but often are confounded by thermal effects that are inter-mixed with neural responses. Aim Here, we develop and demonstrate a method for effectively suppressing fluorescent thermal transients from calcium responses. Approach We use high precision phased-array 3 MHz focused ultrasound delivery integrated with fiberscope-based widefield fluorescence to monitor cortex-wide calcium changes. Our approach for detecting the neural activation first takes advantage of the high inter-hemispheric correlation of resting state Ca2+ dynamics and then removes the ultrasound-induced thermal effect by subtracting its simulated spatio-temporal signature from the processed profile. Results The focused 350 μm-sized ultrasound stimulus triggered rapid localized activation events dominated by transient thermal responses produced by ultrasound. By employing bioheat equation to model the ultrasound heat deposition, we can recover putative neural responses to ultrasound. Conclusions The developed method for canceling transient thermal fluorescence quenching could also find applications with optical stimulation techniques to monitor thermal effects and disentangle them from neural responses. This approach may help deepen our understanding of the mechanisms and macroscopic effects of ultrasound neuromodulation, further paving the way for tailoring the stimulation regimes toward specific applications.
Abstract via europepmc.
Exposures
Exposure 1: focused ultrasound stimulation of mouse cortex
Target: cerebral cortex — “mouse cortex”
Device: IGT / Imasonic · Imasonic ✓
| Waveform | continuous | |
|---|---|---|
| Fundamental frequency (kHz) | 3,000 | ✓✓✓ |
| Pulse duration (ms) | not applicable | ⚑ |
| Pulse repetition frequency (Hz) | not applicable | |
| Duty cycle (%) | not applicable | |
| Sonication duration (s) | 0.15 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | measurementmean or range across subjects | |
| In-situ pressure (kPa) | 2,500, 2,800swept | ✓✓✓ |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
Mice were sonicated through an intact skull with 150-ms duration pulses at 3 MHz (described elsewhere as 'a continuous 0.15 s duration US pulse'), with 20 repeated stimuli per experiment separated by a constant 10-s interval to minimize interference between consecutive stimulations.
Flags from extraction
n_sessions_per_subject— Each mouse underwent one described in vivo imaging/sonication experiment (with 20 repeated stimuli within it), but the paper never explicitly states the number of sessions per animal.exposures[0].timing.pulse_duration_ms— Classified as continuous wave per the burst rule (single uninterrupted 150-ms tone burst per trial, explicitly called 'a continuous 0.15 s duration US pulse' in the Fig. 4 legend); pulse_duration_ms and PRF are therefore null and sonication_duration_s carries the 150 ms burst length.