Biology subjects

Franceschini, M. A.

Publications and source records attributed to Franceschini, M. A..

3 recordsLinked to original sources

bioRxiv2025

Mapping human cerebral blood flow with high-density, multi-channel speckle contrast optical spectroscopy

Recently, speckle contrast optical spectroscopy (SCOS) enabled non-invasive, high signal-to-noise-ratio (SNR) human cerebral blood flow (CBF) measurements, relevant for both neuroscience and clinical monitoring of diseases with CBF dysregulation. Single channel SCOS measurements limit the information obtained to only one location on the head. In this work, we develop a multi-channel SCOS system to map spatial heterogeneity in CBF changes during human brain activation. Using a galvanometer, we temporally multiplexed a free-space laser to 7 source fibers positioned at different locations on the head. Diffuse light collected from the tissue is captured by fiber bundles projecting to 17 complementary metal-oxide semiconductor (CMOS) cameras, resulting in 50 source-detector channels measuring optical density (OD) and relative CBF changes covering an area of 7.6 cm by 6.6 cm on the head. We validated the spatial specificity and stability of the system using a liquid flow phantom. We then measured brain activity during a word-color Stroop task in 15 subjects and obtained brain activation maps. The average signal changes in the channel showing the largest activation were 1.7 x 10-2 in {Delta}OD and 6.6% in CBF.

bioengineering↗

bioRxiv2024

Pathlength-selective, interferometric diffuse correlation spectroscopy (PaLS-iDCS)

Diffuse correlation spectroscopy (DCS) is an optical method that offers non-invasive assessment of blood flow in tissue through the analysis of intensity fluctuations in diffusely backscattered coherent light. The non-invasive nature of DCS has enabled several clinical application areas for deep tissue blood flow measurements, including neuromonitoring, cancer imaging, and exercise physiology. While promising, in measurement configurations targeting deep tissue hemodynamics, standard DCS implementations suffer from insufficient signal-to-noise ratio (SNR), depth sensitivity, and sampling rate, limiting their utility. In this work, we present an enhanced DCS method called pathlength-selective, interferometric DCS (PaLS-iDCS), which uses pathlength-specific coherent gain to improve both the sensitivity to deep tissue hemodynamics and measurement SNR. Through interferometric detection, PaLS-iDCS can provide time-of-flight (ToF) specific blood flow information without the use of expensive time-tagging electronics and low-jitter detectors. The technique is compared to time-domain DCS (TD-DCS), another enhanced DCS method able to resolve photon ToF in tissue, through Monte Carlo simulation, phantom experiments, and human subject measurements. PaLS-iDCS consistently demonstrates improvements in SNR (>2x) for similar measurement conditions (same photon ToF), and the SNR improvements allow for measurements at extended photon ToFs, which have increased sensitivity to deep tissue hemodynamics ([~]50% increase). Further, like TD-DCS, PaLS-iDCS allows direct estimation of tissue optical properties from the sampled ToF distribution. This method offers a relatively straightforward way to allow DCS systems to make robust measurements of blood flow with greatly enhanced sensitivity to deep tissue hemodynamics without the need for time-resolved detection, enabling further applications of this non-invasive technology.

bioengineering↗

bioRxiv2019

Transcranial Near-Infrared Light: Dose-Dependent Effects on EEG Oscillations but not Cerebral Blood Flow

ObjectiveOur objective was to assess whether transcranial photobiomodulation (tPBM) with near-infrared light (NIR) shows modulatory effects on cerebral electrical activity through electroencephalogram (EEG) and cerebral blood flow (CBF). BackgroundtPBM has emerged as a novel intervention for several neuropsychiatric conditions due to its neuroprotective and neuroenhancement effects. MethodsWe conducted a single-blind, sham-controlled pilot study to test the effect of continuous (c-tPBM), pulse (p-tPBM) and sham (s-tPBM) transcranial photobiomodulation on EEG oscillations and CBT using diffuse correlation spectroscopy (DCS) in a sample of ten healthy subjects [6 F/ 4 M; mean age 28.6 {+/-} 12.9 (SD) years]. c-tPBM NIR (830 nm; 54.8 mW/cm{superscript 2}; 65.8 J/cm{superscript 2}; 2.3 kJ) and p-tPBM (830 nm; 10Hz; 54.8 mW/cm{superscript 2}; 33%; 21.7 J/cm{superscript 2}; 0.8 kJ) were delivered concurrently to the frontal areas (F4, Fp2, Fp1, F3 - total surface 35.8 cm{superscript 2}) by four LED clusters (TPBM-1000 Litecure). EEG and DCS recordings were performed weekly before, during, and after each tPBM session (in sequence: c-tPBM, s-tPBM and p-tPBM). ResultsOnly c-tPBM significantly boosted gamma (t = 3.02, df = 7, p < .02) and beta (t = 2.91, df = 7, p < .03) EEG spectral powers in eyes-open recordings and gamma power (t = 3.61, df = 6, p < .015) in eyes-closed recordings, with the largest effects in the posterior regions. There was no significant effect of NIR-tPBM on CBF compared to sham. ConclusionsOur data suggest a dose-dependent effect of tPBM with NIR (c-tPBM) on cerebral gamma and beta neuronal activity. Altogether, our findings support the neuromodulatory effect of transcranial NIR.

neuroscience↗