Vascular impedance is a frequency dependent quantity relating a vascular compartment's flow dynamics to pressure changes. Although vascular impedance has been investigated in larger arteries using Doppler ultrasound, probing the smaller microvasculature using similar techniques is difficult due to their small cross-sectional area. However, recent developments using diffuse optics have enabled the possibility of measuring blood flow and volume in arterioles and other microvasculature. This research presents a method to estimate the arteriole impedance non-invasively using diffuse correlation spectroscopy (DCS) as well as near-infrared spectroscopy (NIRS).

High-density speckle contrast optical tomography (HD-SCOT) is a potentially attractive technique for bedside imaging of cerebral blood flow (CBF). To evaluate the performance of HD-SCOT, we built a pipeline with an anatomical head model for simulating measurements and reconstructed images. We observed that the cortical region is well represented by measurements with source-detector distance at least 29 mm. Including larger source-detector distances can reduce localization errors but with reduced signal-to-noise ratio (SNR). Imaging performance is highly dependent on the exposure time, with optimal exposure time dependent on the noise model. Future HD-SCOT systems will be designed using these results.

One sedative drug to induce anesthesia during surgery is propofol. It diminishes the cerebral metabolic rate of oxygen (CMRO2), preventing memory formation and is coupled with a decrease in the cerebral blood flow (CBF). Anesthesia depth is commonly monitored by the bispectral index (BIS) to avoid awareness. Optical hybrid near-infrared spectroscopies have the potential to assess CMRO2 and other physiological signals (i.e. CBF). Optical signals acquired alongside BIS in surgeries were compared to it and provided additional information. Overall, agreement was found at different levels (group analysis, single subject analysis and simultaneity in time of changes).

An innovative camera-based speckle contrast diffuse correlation tomography (scDCT) technology has been developed recently, which enables noncontact, noninvasive, high-density, 3D imaging of cerebral blood flow (CBF) distributions. This study demonstrated the capability and safety of scDCT technique for imaging of CBF distributions in a neonatal piglet model of transient ischemic stroke. Moreover, power spectral density analyses of low-frequency oscillations (LFOs) and the network connections over the brain were assessed before and after the induction of acute ischemic stroke. The stroke resulted in a substantial decrease in CBF, attenuations in resting-state LFOs, and functional connectivity disruptions in motor and somatosensory cortices.

Cerebral autoregulation (CA) as a mechanism to protect the brain from ischemia or hypoperfusion may play an important role related to post-stroke interventions such as the physiotherapy and the outcome. Here, we present a non-invasive assessment of the CA status by diffuse correlation spectroscopy (DCS) measures calculating the DCS moving correlation coeffcient CBFx with arterial blood pressure (ABP). The measurements are performed during the first mobilization after the onset of the symptoms. The CBFx is compared to values obtained in a healthy population showing signicantly higher values in the stroke population. This may pave the way for personalized treatment.

The current study is aimed at investigating the influence of radiotherapy on the optical properties of white matter in patients with brain gliomas using cross-polarization OCT. It was performed on ex vivo samples of peritumoral white matter collected from patients with primary surgery and patients who underwent a course of radiotherapy before surgery. The enhancement of scattering properties in case of use of radiotherapy was detected and the optical coefficients that most accurately reflect the relationship between the optical and morphological properties of white matter in both groups of patients were determined.

Studying brain development requires child-friendly imaging modalities and stimulus paradigms. High density diffuse optical tomography provides enhanced image quality over fNIRS and is validated extensively against fMRI in adults. Movie viewing reduces head motion and increases task engagement. Movie features are tracked and correlated with brain activity to map multiple processing pathways in parallel. We propose machine learning methods to extract high-level audiovisual features to avoid the time-consuming, subjective task of manual coding these feature regressors. Using a Faster Region-based Convolutional Neural Network, we achieve high correlation values between manually and automatically generated face regressors and regression coefficient maps.

A limiting factor for personalizing therapies in stroke patients is the inability to continuously monitor the cerebral status of patients. In particular, potential impairment of cerebral autoregulation (CA) in these patients may incur certain risks during their mobilization. We have used hybrid diffuse optical techniques to measure new biomarkers related to CA status as well as metabolic health in a large cohort of stroke patients in order to determine biomarkers indicative of clinical improvement. If validated, these results can pave the way towards personalization of stroke therapy based on direct measures of cerebral health.

Current standard-of-care methods for measuring intracranial pressure (ICP) are highly invasive. To overcome this limitation, we recently demonstrated non-invasive quantification of ICP in an animal model using morphological analysis of the pulsatile cerebral blood flow (CBF) measured with Diffuse Correlation Spectroscopy. Here, we present results from a pilot study in pediatric patients admitted to an intensive care unit. We show that the CBF pulsatile waveform changes with ICP. Using a regression forest-based machine learning algorithm on a cohort of patients (n>15) we demonstrate that ICP extraction in humans can be possible, suggesting the potential for successful clinical translation in future.