High-density speckle contrast optical tomography of cerebral blood flow response to functional stimuli in the rodent brain

Noninvasive, three-dimensional, and longitudinal imaging of cerebral blood flow (CBF) in small animal models and ultimately in humans has implications for fundamental research and clinical applications. It enables the study of phenomena such as brain development and learning and the effects of pathologies, with a clear vision for translation to humans. Speckle contrast optical tomography (SCOT) is an emerging optical method that aims to achieve this goal by directly measuring three-dimensional blood flow maps in deep tissue with a relatively inexpensive and simple system. High-density SCOT is developed to follow CBF changes in response to somatosensory cortex stimulation. Measurements are carried out through the intact skull on the rat brain. SCOT is able to follow individual trials in each brain hemisphere, where signal averaging resulted in comparable, cortical images to those of functional magnetic resonance images in spatial extent, location, and depth. Sham stimuli are utilized to demonstrate that the observed response is indeed due to local changes in the brain induced by forepaw stimulation. In developing and demonstrating the method, algorithms and analysis methods are developed. The results pave the way for longitudinal, nondestructive imaging in preclinical rodent models that can readily be translated to the human brain

Decoding human mental states by whole-head EEG+fNIRS during category fluency task performance

Objective: Concurrent scalp electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS), which we refer to as EEG+fNIRS, promises greater accuracy than the individual modalities while remaining nearly as convenient as EEG. We sought to quantify the hybrid system's ability to decode mental states and compare it with unimodal systems. Approach: We recorded from healthy volunteers taking the category fluency test and applied machine learning techniques to the data. Main results: EEG+fNIRS's decoding accuracy was greater than that of its subsystems, partly due to the new type of neurovascular features made available by hybrid data. Significance: Availability of an accurate and practical decoding method has potential implications for medical diagnosis, brain-computer interface design, and neuroergonomics

Does wearing a non-medical face mask cause changes in cerebral hemodynamics?

We present a study investigating the effect of non-medical face masks (FFP2 and surgical) on cerebral hemodynamics measured by transcranial hybrid diffuse optics, and on systemic physiology in 13 healthy adults (age: 23-33 years)

Effects of red blood cell transfusion on neonatal cerebral hemodynamics: a TD-NIRS and DCS study

Anemia is a common problem in preterm neonates, and red blood cell transfusion (RBCT) is used to improve oxygen delivery. In order to limit the risk of possible complications new strategies to minimize the need for RBCTs are needed, as assessment of hemoglobin concentration in blood ([Hb]) alone appears to be an inadequate biomarker. In this study, we search for hemodynamic and metabolic thresholds to help define the need of RBCT in anemic newborns. The effect of RBCTs on cerebral tissue oxygen saturation (StO2) and blood flow (measured as Blood Flow Index, BFI) was estimated using a non-invasive hybrid diffuse optical device that combines Time Domain NIRS (TD-NIRS) and Diffuse Correlation Spectroscopy (DCS) techniques (BabyLux device). We enrolled 18 clinically stable neonates receiving RBCT at Neonatal Intensive Care Unit (NICU) of Ospedale Maggiore Policlinico in Milan. Tissue oxygen extraction (TOE) and the cerebral metabolic rate of oxygen consumption index (CMRO2I) were computed, the Wilkinson signed rank test for paired data was performed to compare data before and after RBCT. Preliminary results are in accordance with previous publications as regards cerebral oxygenation: a significant increase in StO2 (from 56.62 ± 5.20% to 63.85 ± 4.95%, p<0.05) and reduction in TOE (from 41.35 ± 5.9 % to 31.04 ±5.41%, p<0.05) were observed. The response in cerebral blood flow was smaller (only 10%) but also more variable, so conclusions regarding the effect of transfusion on cerebral oxygen metabolism are still uncertain

An optical biomarker of hypoxic-ischaemic injury severity in the neonatal brain

We present a new optical platform that combines broadband near-infrared spectroscopy and diffuse correlation spectroscopy for identification of brain injury severity in a preclinical model of hypoxic-ischemic encephalopathy of the neonatal brain

An optical biomarker of hypoxic-ischaemic injury severity in the neonatal brain

We present a new optical platform that combines broadband near-infrared spectroscopy and diffuse correlation spectroscopy for identification of brain injury severity in a preclinical model of hypoxic-ischemic encephalopathy of the neonatal brain

Cerebrovascular reactivity to carbon dioxide tension in newborns: Data from combined time-resolved near-infrared spectroscopy and diffuse correlation spectroscopy

Significance: Critically ill newborns are at risk of brain damage from cerebrovascular disturbances. A cerebral hemodynamic monitoring system would have the potential role to guide targeted intervention. Aim: To obtain, in a population of newborn infants, simultaneous near-infrared spectroscopy (NIRS)-based estimates of cerebral tissue oxygen saturation (StO2) and blood flow during variations of carbon dioxide tension (pCO2) levels within physiologic values up to moderate permissive hypercapnia, and to examine if the derived estimate of metabolic rate of oxygen would stay constant, during the same variations. Approach: We enrolled clinically stable mechanically ventilated newborns at postnatal age >24 h without brain abnormalities at ultrasound. StO2 and blood flow index were measured using a non-invasive device (BabyLux), which combine time-resolved NIRS and diffuse-correlation spectroscopy. The effect of changes in transcutaneous pCO2 on StO2, cerebral blood flow (CBF), and cerebral metabolic rate of oxygen index (tCMRO2i) were estimated. Results: Ten babies were enrolled and three were excluded. Median GA at enrollment was 39 weeks and median weight 2720 g. StO2 increased 0.58% (95% CI 0.55; 0.61, p < 0.001), CBF 2% (1.9; 2.3, p < 0.001), and tCMRO2 0.3% (0.05; 0.46, p 0.017) per mmHg increase in pCO2. Conclusions: BabyLux device detected pCO2-induced changes in cerebral StO2 and CBF, as expected. The small statistically significant positive relationship between pCO2 and tCMRO2i variation is not considered clinically relevant and we are inclined to consider it as an artifact

Cerebral oxygenation and blood flow in term infants during postnatal transition : BabyLux project

Objectives: A new device that combines, for the first time, two photonic technologies (time-resolved near-infrared spectroscopy and diffuse correlation spectroscopy) was provided and tested within the BabyLux project. Aim was to validate the expected changes in cerebral oxygenation and blood flow. Methods: A pulse oximeter and the BabyLux device were held in place (right hand/wrist and frontoparietal region, respectively) for 10 min after birth in healthy term infants delivered by elective caesarean section. Pulse oximeter saturation (SpO 2 ), cerebral tissue oxygen saturation (StO 2 ) and blood flow index (BFI) were measured over time. Tissue oxygen extraction (TOE) and cerebral metabolic rate of oxygen index (CMRO 2 I) were calculated. Results: Thirty infants were enrolled in two centres. After validity check of data, 23% of infants were excluded from TOE and CMRO 2 I calculation due to missing data. As expected, SpO 2 (estimate 3.05 %/min; 95% CI 2.78 to 3.31 %/min) and StO 2 (estimate 3.95 %/min; 95% CI 3.63 to 4.27 %/min) increased in the first 10 min after birth, whereas BFI (estimate -2.84 710 -9 cm 2 /s/min; 95% CI -2.50 710 -9 to -3.24 710 -9 cm 2 /s/min) and TOE (estimate -0.78 %/min; 95% CI -1.12 to -0.45 %/min) decreased. Surprisingly, CMRO 2 I decreased (estimate -7.94 710 -8 /min; 95% CI -6.26 710 -8 to -9.62 710 -8 /min). Conclusions: Brain oxygenation and BFI during transition were successfully and simultaneously obtained by the BabyLux device; no adverse effects were recorded, and the BabyLux device did not limit the standard care. The preliminary results from clinical application of the BabyLux device are encouraging in terms of safety and feasibility; they are consistent with previous reports on brain oxygenation during transition, although the interpretation of the decreasing CMRO 2 I remains open. Trial registration number: NCT02815618