A5045664151- Photoacoustic and Ultrasonic Imaging
- Ultrasound Imaging and Elastography
- Ultrasound and Hyperthermia Applications
- Ultrasonics and Acoustic Wave Propagation
- Thermography and Photoacoustic Techniques
- Acoustic Wave Phenomena Research
- Optical Imaging and Spectroscopy Techniques
- Microwave Imaging and Scattering Analysis
- Advanced MRI Techniques and Applications
- Seismic Waves and Analysis
- Electromagnetic Simulation and Numerical Methods
- Flow Measurement and Analysis
- Seismic Imaging and Inversion Techniques
- Microfluidic and Bio-sensing Technologies
- Hearing Loss and Rehabilitation
- Underwater Acoustics Research
- Speech and Audio Processing
- Ultrasound and Cavitation Phenomena
- Model Reduction and Neural Networks
- Fractional Differential Equations Solutions
- Medical Imaging Techniques and Applications
- Advanced Numerical Methods in Computational Mathematics
- Orbital Angular Momentum in Optics
- Electromagnetic Scattering and Analysis
- Numerical methods in inverse problems
University College London
2016-2025
National Physical Laboratory
2017-2021
Brno University of Technology
2016-2019
Sheffield Hallam University
2017
York Teaching Hospital NHS Foundation Trust
2017
Royal Surrey County Hospital
2017
Chinese University of Hong Kong
2015
Australian National University
2011-2013
The University of Western Australia
2007
A new, freely available third party MATLAB toolbox for the simulation and reconstruction of photoacoustic wave fields is described. The toolbox, named k-Wave, designed to make realistic modeling simple fast. forward simulations are based on a k-space pseudo-spectral time domain solution coupled first-order acoustic equations homogeneous or heterogeneous media in one, two, three dimensions. functions can additionally be used as flexible reversal image algorithm an arbitrarily shaped...
The simulation of nonlinear ultrasound propagation through tissue realistic media has a wide range practical applications. However, this is computationally difficult problem due to the large size computational domain compared acoustic wavelength. Here, k-space pseudospectral method used reduce number grid points required per wavelength for accurate simulations. model based on coupled first-order equations valid wave in heterogeneous with power law absorption. These are derived from fluid...
The reconstruction of photoacoustic images typically neglects the effect acoustic absorption on measured time domain signals. Here, a method to compensate for in tomography is described. approach based time-reversal image and an absorbing equation state which separately accounts dispersion following frequency power law. Absorption compensation inverse problem achieved by reversing proportionality coefficient sign but leaving equivalent parameter unchanged. regularized filtering terms spatial...
The efficient simulation of wave propagation through lossy media in which the absorption follows a frequency power law has many important applications biomedical ultrasonics. Previous equations use time-domain fractional operators require storage complete pressure field at previous time steps (such are convolution based). This makes them unsuitable for three-dimensional problems interest. Here, equation that utilizes two derivative based on Laplacian is derived. These account separately...
The use of a novel all-optical photoacoustic scanner for imaging the development tumor vasculature and its response to therapeutic vascular disrupting agent is described. employs Fabry-Perot polymer film ultrasound sensor mapping waves an image reconstruction algorithm based upon attenuation-compensated acoustic time reversal. system was used noninvasively human colorectal xenografts implanted subcutaneously in mice. Label-free three-dimensional vivo images whole tumors depths almost 10 mm...
As transcranial ultrasound stimulation (TUS) advances as a precise, non-invasive neuromodulatory method, there is need for consistent reporting standards to enable comparison and reproducibility across studies. To this end, the International Transcranial Ultrasonic Stimulation Safety Standards Consortium (ITRUSST) formed subcommittee of experts several domains review suggest standardised parameters low intensity TUS, resulting in guide presented here. The scope limited aspects study....
A noninvasive, multimodal photoacoustic and optical coherence tomography (PAT/OCT) scanner for three-dimensional in vivo (3D) skin imaging is described. The system employs an integrated, all detection scheme both modalities backward mode utilizing a shared 2D with field-of-view of ~13 × 13 mm(2). waves were detected using Fabry Perot polymer film ultrasound sensor placed on the surface skin. transparent spectral range 590-1200 nm. This permits excitation beam (670-680 nm) OCT probe (1050 to...
Non-invasive, focal neurostimulation with ultrasound is a potentially powerful neuroscientific tool that requires effective transcranial focusing of to develop. Time-reversal (TR) using numerical simulations propagation can correct for the effect skull, but relies on accurate simulations. Here, requirements ultrasonic are established through review previously employed parameters, and consideration deep brain targets. The specific limitations finite-difference time domain (FDTD) k-space...
The reconstruction of images in photoacoustic tomography is reliant on specifying the speed sound within propagation medium. However, for vivo imaging, this value not normally accurately known. Here, an autofocus approach automatically selecting proposed. This based maximizing sharpness reconstructed image as quantified by a focus function. Several functions are investigated, and their performance discussed. method demonstrated using phantom measurements made medium with known vasculature...
Optical ultrasound transducers were created by coating optical fibres with a composite of carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS). Dissolution CNTs in PDMS to create the was facilitated functionalisation oleylamine. Composite surfaces applied using dip coating. Under pulsed laser excitation, pressures 3.6 MPa 4.5 at coated end faces achieved fibre core diameters 105 200 μm, respectively. The results indicate that CNT-PDMS coatings on could be viable alternatives electrical...
Ultrasound computed tomography (USCT) is a non-invasive imaging technique that provides information about the acoustic properties of soft tissues in body, such as speed sound (SS) and attenuation (AA). Knowledge these can improve discrimination between benign malignant masses, especially breast cancer studies. Full wave inversion (FWI) methods for image reconstruction USCT provide best quality compared to more approximate methods. Using FWI, SS usually recovered time domain, AA frequency...
Photoacoustic Tomography (PAT) is an emerging biomedical "imaging from coupled physics" technique, in which the image contrast due to optical absorption, but information carried surface of tissue as ultrasound pulses. Many algorithms and formulae for PAT reconstruction have been proposed case when a complete data set available. In many practical imaging scenarios, however, it not possible obtain full data, or may be sub-sampled faster acquisition. such cases, that can incorporate prior...
A new model for simulating elastic wave propagation using the open-source k-Wave MATLAB Toolbox is described. The based on two coupled first-order equations describing stress and particle velocity within an isotropic medium. For absorbing media, Kelvin-Voigt of viscoelasticity used. are discretised in 2D 3D efficient time-stepping pseudospectral scheme. This uses Fourier collocation spectral method to compute spatial derivatives a leapfrog finite-difference scheme integrate forwards time....
High intensity transcranial focused ultrasound is an FDA approved treatment for essential tremor, while low-intensity applications such as neurostimulation and opening the blood brain barrier are under active research. Simulations of propagation used both focusing through skull, predicting intracranial fields. Maps skull acoustic properties necessary accurate simulations, can be derived from medical images using a variety methods. The maps range segmented, homogeneous models, to fully...
Computational models of acoustic wave propagation are frequently used in transcranial ultrasound therapy, for example, to calculate the intracranial pressure field or phase delays correct skull distortions. To allow intercomparison between different modeling tools and techniques by community, an international working group was convened formulate a set numerical benchmarks. Here, these benchmarks presented, along with results. Nine increasing geometric complexity defined. These include...
Several different reconstruction algorithms have been proposed for photoacoustic tomography, most of which presuppose that the acoustic properties medium are constant and homogeneous. In practice, there often unknown spatial variations in properties, these give, at best, only approximate estimates true image. The question as to approach is robust circumstances therefore one practical importance. Image by ¿time reversal¿-using a numerical propagation model with time-varying boundary condition...
Most reconstruction algorithms used in photoacoustic tomography do not account for the effects of acoustic attenuation on recorded signals. For experimental measurements made biological tissue, frequency dependent causes high components propagating waves to be significantly reduced. This signal loss manifests as a depth magnitude error and blurring features within reconstructed image. Here, general method compensating this using time-variant filtering is presented. The filter constructed...
The ability to noninvasively image embryonic vascular anatomy in mouse models is an important requirement for characterizing the development of normal cardiovascular system and malformations heart supply. Photoacoustic imaging, which can provide high resolution non invasive images vasculature based upon optical absorption by endogenous hemoglobin, well suited this application. In study, photoacoustic embryos were obtained ex vivo vivo. show intricate details depths up 10 mm, allowed whole be...
Model-based treatment planning and exposimetry for high-intensity focused ultrasound requires the numerical simulation of nonlinear propagation through heterogeneous absorbing media. This is a computationally demanding problem due to large distances travelled by waves relative wavelength highest frequency harmonic. Here, k-space pseudospectral method used solve set coupled partial differential equations equivalent generalised Westervelt equation. The model implemented in C++ parallelised...
Model-based treatment planning for transcranial ultrasound therapy typically involves mapping the acoustic properties of skull from an X-ray computed tomography (CT) image head. Here, three methods generating pseudo-CT (pCT) images magnetic resonance (MR) were compared as alternative to CT. A convolutional neural network (U-Net) was trained on paired MR-CT generate pCT T either T1-weighted or zero-echo time (ZTE) MR (denoted tCT and zCT, respectively). direct ZTE also implemented cCT). When...
Transcranial ultrasonic stimulation (TUS) is an emerging technology for non-invasive brain stimulation. Currently, there are no established guidelines the safe application of neuromodulation in humans beyond those used diagnostic ultrasound. Therefore, a series meetings, International Consortium Ultrasonic Stimulation Safety and Standards (ITRUSST) has expert consensus on considerations biophysical safety TUS. As with ultrasound, two main risks associated TUS: mechanical thermal bioeffects....
Abstract Transcranial ultrasound stimulation (TUS) has emerged as a promising technique for non-invasive neuromodulation, but current systems lack the precision to target deep brain structures effectively. Here, we introduce an advanced TUS system that achieves unprecedented in neuromodulation. The features 256-element, helmet-shaped transducer array operating at 555 kHz, coupled with stereotactic positioning system, individualised treatment planning, and real-time monitoring using...
A pseudospectral model of linear elastic wave propagation is described based on the first order stress-velocity equations elastodynamics. k-space adjustments to spectral gradient calculations are derived from dyadic Green’s function solution second-order equation and used (a) ensure exact for homogeneous timesteps arbitrarily large size, (b) also allows larger time steps without loss accuracy in heterogeneous media. The formulation wavefield be split easily into compressional shear parts....