Optical Detection of Ultrasound in Photoacoustic Imaging
Photoacoustic (PA) imaging offers unique capabilities in studying biological tissue based on optical absorption contrast. The sensitivity and bandwidth in detecting laser-induced ultrasonic signals are crucial for attaining high-quality and high-resolution PA images. Recent studies have shown that optical detection of ultrasound can provide improved detection angle and sensitivity over significantly extended bandwidth. In this review, we provide an overview of recent technological advances in optical methods of ultrasound detection by classifying them based on their implementations in photoacoustic imaging. We further introduce a theoretical framework to generalize sensitivity, bandwidth, and spatial responses of optical ultrasound detection geometries.
Compound Radar Approach for Breast Imaging
This paper considers the problem of detecting tumour targets within breast phantoms using multistatic radar. To accurately image small, potentially cancerous targets, a significant number of multistatic channels are required in order to adequately calibrate-out unwanted skin reflections and increase immunity to clutter. However, increasing the density of antennas within an array is inevitably limited by the geometry of the microwave elements designed for biological applications. A novel compound imaging approach is presented to overcome these constraints and improve the imaging performance of a multistatic radar modality. Experimental data is acquired to evaluate the algorithm using constructed phantoms of varying complexity.
Epileptogenic Source Imaging Using Cross Frequency Coupled Signals from Scalp EEG
The epileptogenic zone (EZ) is a brain region responsible for seizure genesis. This study describes a novel EEG source imaging (ESI) method to estimate the EZ which uses cross frequency coupled potential signals (SCFC) derived from scalp EEG. Results were validated using 1) known surgical resections for Engel I-IV patients, and 2) through forward modelling with noise simulation. The SCFC demonstrated significant advantages over “raw” scalp EEG.
Noninvasive Electromagnetic Source Imaging and Granger Causality Analysis: An Electrophysiological Connectome (eConnectome) Approach
We present an electrophysiological connectome (eConnectome) approach to study underlying brain networks in a noninvasive manner. This approach was directly tested by estimating epileptic networks from EEG/MEG measurements in patients suffering from focal epilepsy. The results obtained from the proposed approach were consistent with invasive clinical findings, in these patients.
Electrical Stimulation of the Human Cerebral Cortex by Extracranial Muscle Activity: Effect Quantification with Intracranial EEG and FEM Simulations
One’s own EMG activity may act as an endogenous modality of brain stimulation. Using electrocorticography (ECoG) recordings combined with detailed finite element method (FEM) head modeling we show first results suggesting that the temporal pole might be exposed to EMG electric fields strong enough to modulate ongoing neuronal activity. This modulation could represent a new potential mechanism for the puzzling effects of gum chewing on cognition.
Time-Frequency Strategies for Increasing High-Frequency Oscillation Detectability in Intracerebral EEG
High-frequency oscillations (HFOs) are considered to be a good marker of the tissues which have to be removed. We investigated several methods to flatten (i.e. whiten) the spectrum to improve HFO detectability. Our method, the H0 z-score, provides an optimal framework for representing and detecting HFOs, independent of a baseline and a priori frequency bands.