Lefebvre, A. T. | Search bioRxiv

bioRxiv2026

Non-contact optical imaging of tissue deformation enables in vivo cardiovascular monitoring

Significance: Continuous, non-invasive monitoring of cardiovascular physiology provides critical information for clinical decision-making and patient care. Emerging optical sensors enable non-contact measurement of physiological parameters such as heart rate and respiratory rate, but current methods are limited in their ability to capture spatially resolved physiological waveforms. Aim: We aimed to extend the capabilities of non-contact cardiovascular monitoring by using an imaging-based approach from which spatially resolved physiological waveforms can be extracted and cardiovascular biomarkers can be derived in vivo. Approach: We implemented a digital holographic imaging sensor to continuously measure calibrated tissue motion for in vivo assessment of cardiovascular biomarkers in six adult male Sprague-Dawley rats, with validation against electrocardiographic and invasive arterial blood pressure measurements. Results: Heart rate and pulse arrival time-derived pulse wave velocity calculated from digital holographic imaging demonstrate strong agreement with reference-derived metrics (concordance correlation coefficient [≥] 0.98). Heart rate variability shows moderate agreement with reference-derived metrics (concordance correlation coefficient [≥] 0.59).

bioengineering↗

bioRxiv2023

High-resolution label-free transcranial imaging of in vivo neural activity via interferometric measurement of tissue deformation

Rapid sub-nanometer neuronal deformations have been shown to occur as a consequence of action potentials in vitro, allowing for registration of discrete axonal and synaptic depolarizations and thus providing a novel signature for recording neural activity (1-3). We demonstrate that this signature can be extended to in vivo measurements through recording of rapid neuronal deformations on the population level with optical phase-based recordings. Complicating these measurements is the optical phase noise due to microvascular flow as well as the presence of significant tissue clutter (deformation) associated with physiologic processes (e.g., heart and respiratory rate). These recordings were acquired using a full-field holographic imaging system with spatiotemporal resolutions of less than 1 ms and 0.1 mm3 over a 3 mm diameter field of view (FOV). Our system demonstrates, for the first time, the ability to non-invasively record in vivo tissue deformation associated with population level neuronal activity. We confirmed this technique across a range of neural activation models, including direct epidural focal electrical stimulation (FES), activation of primary somatosensory cortex via whisker barrel stimulation, and pharmacologically-induced seizures. Calibrated displacement measurements of the associated tissue deformations provided additional insight into the underlying neural activation mechanisms. Collectively, we show that holographic imaging provides a pathway for high-resolution, label-free, non-invasive recording of transcranial in vivo neural activity at depth, making it highly advantageous for studying neural function and signaling.

neuroscience↗