## About

76

Publications

7,306

Reads

**How we measure 'reads'**

A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more

695

Citations

Introduction

Additional affiliations

January 2016 - January 2016

January 2016 - January 2016

## Publications

Publications (76)

The study of blood has been a subject of great interest for decades in understanding human physiology. The optical properties [absorption coefficient (μa), scattering coefficient (μs), and anisotropy coefficient (g)] of blood play key role in generation and determining the strengths of photoacoustic (PA) waves. Red blood cells (RBCs) are the domina...

A reconstructed image in photoacoustic tomography (PAT) imaging modality can be blurred because of some system-dependent effects – broad laser pulse, the limited bandwidth of the sensors, acoustically attenuating medium and transducers with finite-size apertures having Gaussian sensitivity profile. A robust deblurring method involving a system matr...

Sensor directivity in photoacoustic tomography (PAT) imaging is investigated. The photoacoustic (PA) signals with directivity effect were used to construct the system matrix needed for the Tikhonov regularization. This method provides improved PAT images.

We employ the polynomial-based interpolation methods for photoacoustic tomography (PAT). The nearest-neighbour, bilinear, bicubic, and biquintic interpolation algorithms were utilized to construct the model matrix. The performance of these interpolation techniques was studied.

Photoacoustic tomography (PAT) imaging employing polynomial-based interpolation methods is discussed. Nearest-neighbor, bilinear, bicubic and biquintic algorithms were implemented for the construction of the model matrix, and images were formed using the Tikhonov regularization and total variation (TV) minimization procedures. The performance of th...

The effect of sensor directivity on photoacoustic tomography (PAT) image reconstruction is examined. An analytical expression for the resultant PA signal, when emitted by an ensemble of spherical sources and detected by a planar sensor with finite aperture, is derived. This framework was employed to calculate the PA signal produced by a vasculature...

Optoacoustic (OA) field computation by utilizing k-Wave simulation toolbox for six commonly used nanoparticles (NPs) has been performed. The characterization of NPs is often accomplished by the numerical simulation approach. Although, these simulation techniques are complicated, very costly, time-taking and arduous. Accordingly, there is a prerequi...

Frequency dependent differential photoacoustic cross-section (DPACS) over a large frequency band (100–1000 MHz) has been computed and subsequently, morphological parameters of photoacoustic (PA) source have been quantified. Green’s function method has been employed for computing the DPACS for a series of ellipsoidal droplets (with varying aspect ra...

A frequency dependent differential photoacoustic cross-section (DPACS) over a large frequency band (100–1000 MHz) was computed, and subsequently, morphological parameters of a photoacoustic (PA) source were quantified. The Green’s function approach was utilized for calculating the DPACS for spheroidal droplets with varying aspect ratios, Chebyshev...

Photoacoustic (PA) field calculation using k-Wave simulation toolbox for normal and pathological red blood cells has been performed. The approach has been employed to compute the PA spectra produced by discocyte, stomatocyte, echno-cyte and sickle cell red blood cells (RBCs) over a large frequency range (100-3500 MHz). The shapes of normal and path...

A theoretical framework for photoacoustic (PA) signal simulation using a discrete particle approach is discussed and tomographic image reconstruction using such signals is reported. Various numerical phantoms in two dimensions were constructed by inserting monodisperse/polydisperse solid circles/discs of uniform strength occupying regular or random...

This work presents two variants of Born-series methods, for the first time, providing a numerical solution to the time-independent photoacoustic wave equation. These methods are effective in providing accurate solution even when there is a mismatch in speed-of-sound between the source and the ambient region. The traditional Born-series (TBS) and co...

The time-independent inhomogeneous photoacoustic wave equation is solved by the Born-series (BS) methods for erythrocyte. The convergent BS method provides accurate results even for strong speed-of-sound mismatch between the source and ambient medium

The combined effect of the transducer size and the width of the incident exciting light pulse in photoacoustic tomography (PAT) imaging has been studied. The transducers have been apodized with the Gaussian function and its full width at half-maximum (FWHM) has been varied to see its effect on blurring in PAT imaging. The Wiener filter has been use...

Angular distribution of a differential photoacoustic cross-section (DPACS) has been examined for various nonspherical axisymmetric particles. The DPACS as a function of measurement angle has been computed for spheroidal particles with varying aspect ratios and fitted with a tri-axes ellipsoid form factor model to extract shape parameters. Similar s...

Photoacoustic tomographic (PAT) image reconstruction with apodized sensors is discussed. A Gaussian function was used to model axisymmetric apodization of sensors, and its full width at half-maximum (FWHM) was varied to investigate the role of apodization on the PAT image reconstruction. The well-known conventional delay-and-sum (CDAS) algorithm an...

The photoacoustic (PA) field calculation using a Green's function approach for nonspherical axisymmetric fluid particles is discussed. The PA fields have been computed for spheroidal droplets, Chebyshev particles and normal and pathological red blood cells (RBCs) over a large frequency band (10–1000 MHz). Theoretically constructed RBC contours have...

The effective medium theory (EMT) was recently developed to model the ultrasound backscatter from aggregating red blood cells [Franceschini, Metzger, and Cloutier, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 58, 2668–2679 (2011)]. The EMT assumes that aggregates can be treated as homogeneous effective scatterers, which have effective propertie...

A detailed derivation of a quantity, defined as the acoustic power per unit solid angle far from the illuminated volume divided by the intensity of the incident light beam and termed as differential photoacoustic (PA) cross section, is presented. The expression for the differential PA cross section per unit absorbing volume retains two terms, namel...

A new theoretical approach for photoacoustic (PA) image simulation of an ensemble of cells with endocy-tosed gold nanoparticles is presented. Each cell was approximated as a fluid sphere and suspended in a nonabsorbing fluid medium. It was assumed that the cellular optical absorption coefficient changed greatly because of endocytosis of nanoparticl...

A methodology for simulating photoacoustic (PA) images of samples with solid spherical absorbers acquired using linear array transducer is described. Two types of numerical phantoms (i.e. polystyrene beads suspended in agar medium) of two different size regimes were imaged with a 40 MHz linear array transducer utilizing this approach. The frequency...

A theoretical approach to model photoacoustic (PA) signals from mixtures of melanoma cells (MCs) and red blood cells (RBCs) is discussed. The PA signal from a cell approximated as a fluid sphere was evaluated using a frequency domain method. The tiny signals from individual cells were summed up obtaining the resultant PA signal. The local signal to...

The effect of endocytosis of gold nanoparticles (AuNPs)
on photoacoustic (PA) signal is examined using computer
simulations. It assumes that the endocytosed
AuNPs significantly enhance cellular optical absorption
but do not alter thermophysical parameters. The
PA signals were computed employing a theoretical
model at various cell and intracellular...

Photoacoustic (PA) measurements on confined and unconfined hemoglobin molecules are presented. In vitro experiments were performed with porcine red blood cells (RBCs) at 532 and 1064 nm at various laser fluences. Fluence was gradually changed from 8 to 21 mJ/cm2/pulse for 532 nm and 353 to 643 mJ/cm2/pulse for 1064 nm. PA signals from suspended RBC...

Ultrasonic backscattered signals from blood contain frequency-dependent information that can be used to obtain quantitative parameters reflecting the aggregation level of red blood cells (RBCs). The approach is based on estimating structural aggregate parameters by fitting the spectrum of the backscattered radio-frequency echoes from blood to an es...

The effect of confinement of hemoglobin molecules on photoacoustic (PA) signal is studied experimentally. The PA amplitudes for samples with suspended red blood cells (SRBCs) and hemolyzed red blood cells (HRBCs) were found to be comparable at each hematocrit for 532 nm illumination. The difference between the corresponding amplitudes increased wit...

The accuracy of the photoacoustic (PA) technique to assess blood oxygen saturation (SO2) using two laser beams was examined theoretically. A Monte Carlo technique was used to simulate 2D tissue configurations, and the PA signals from many red blood cells (RBCs) were constructed by summing the signals emitted by the individual cells. The level of ox...

The simultaneous photoacoustic assessment of oxygen saturation and red
blood cell aggregation is presented. Aggregation was induced on porcine
red blood cells using Dextran-70 at multiple hematocrit levels. Samples
were exposed to 750 nm and 1064 nm for each hematocrit and aggregate
size in order to compute the oxygen saturation. As the size of the...

Possibility of using the photoacoustic (PA) technique to determine hematocrit level was investigated. The PA experiments were conducted with porcine RBCs suspended in phosphate buffered saline (PBS) solution. It was shown that parameters, namely, peak to peak, envelope, positive peak and absolute negative peak of time domain PA signals could be use...

This study aims to investigate the role of red blood cell (RBC) concentration on photoacoustics (PAs). The time dependent PA signals from a collection of RBCs were simulated using a recently developed theoretical model. This model assumes each RBC as a fluid sphere and the PA signals from many cells are generated by adding the contributions from th...

A computer simulation study on the possibility of using photoacoustic (PA) technique to differentiate intraerythrocytic stages of malarial parasite is reported. This parasite during its development substantially converts hemoglobin into hemozoin. This conversion is expected to alter the cellular absorption leading to changes in the PA emission of a...

Red blood cell (RBC) aggregation and oxygenation are important markers for a variety of blood disorders. No current technique is capable of simultaneously measuring aggregation/oxygenation levels noninvasively. We propose using photoacoustic ultrasound spectroscopy (PAUS) for assessing both phenomena. This technique relies on frequency-domain analy...

Malaria parasite during its intraerythrocytic devel-opment digests considerable amount of hemoglobin (Hb) of the host red blood cell (RBC) and converts into a polymerized form of heme, referred to as hemozoin (Hz). The molar extinction coefficient of Hz greatly differs from that of Hb at certain optical wavelengths. Consequently, light absorption a...

Red blood cell (RBC) aggregation is a reversible process which occurs in the presence of increased plasma fibrinogen concentration and low flow conditions. It results in the RBCs forming structures that resemble “stacks of coins” and/or clusters impairing blood flow and the ability of oxygen to diffuse to surrounding tissues. We investigate the use...

The feasibility of detecting red blood cell (RBC) aggregation with photoacoustics (PAs) was investigated theoretically and experimentally using human and porcine RBCs. The theoretical PA signals and spectra generated from such samples were examined for several hematocrit levels and aggregates sizes. The effect of a finite transducer bandwidth on th...

A theoretical model investigating the dependence of optoacoustic (OA) signal on blood oxygen saturation (SO(2)) is discussed. The derivations for the nonbandlimited and bandlimited OA signals from many red blood cells (RBCs) are presented. The OA field generated by many RBCs was obtained by summing the OA field emitted by each RBC approximated as a...

In this paper we examine the potential of using photoacoustic (PA)
spectroscopy for the monitoring of red blood cell (RBC) aggregation
phenomena. The process of RBC aggregation has been shown to occur during
periods of increased plasma fibrinogen concentration and periods of
decreased blood flow (leading to diminished shear forces on the
aggregates...

Red blood cells (RBCs) aggregate in the presence of increased plasma
fibrinogen and low shear forces during blood flow. RBC aggregation has
been observed in deep vein thrombosis, sepsis and diabetes. We propose
using photoacoustics (PA) as a non-invasive imaging modality to detect
RBC aggregation. The theoretical and experimental feasibility of PA...

A theoretical model examining the effects of erythrocyte oxygenation on optoacoustic (OA) signals is presented. Each erythrocyte is considered as a fluid sphere and its optical absorption is defined by its oxygen saturation state. The OA field generated by a cell is computed by solving the wave equation in the frequency domain with appropriate boun...

A theoretical model to study the effects of erythrocyte oxygenation on photoacoustic (PA) signals is described. An erythrocyte was considered as a fluid sphere and for such a sphere the PA field was computed by using a frequency domain approach. The linear superposition principle was used to obtain the resultant PA field generated by a collection o...

The aggregation of red blood cells (RBCs) is a phenomenon that is governed by plasma fibrinogen concentration and the shear forces of flow. We propose the use of photoacoustics (PA) for the detection and characterization of RBC aggregation. A 2D simulation study was performed to investigate the dependence of the PA signal on hematocrit for non-aggr...

In ultrasound tissue characterization dealing with cellular aggregates (such as tumors), it can be hypothesized that cell microstructure and spatial distribution dominate the backscatter signal. Effects of spatial organization and size distribution of nuclei in cell aggregates on ultrasound backscatter are examined in this work using 2-D computer s...

A two dimensional simulation study was performed to investigate the photoacoustic signal properties of non-aggregated and aggregated erythrocytes. Spatial distributions of non-aggregated blood samples were generated by employing a Monte Carlo method and aggregated blood samples were simulated using a hexagonal packing scheme. For the non-aggregatin...

A computer simulation study to produce ultrasonic backscatter coefficients (BSCs) from red blood cell (RBC) clusters is discussed. The simulation algorithm is suitable for generating non-overlapping, isotropic, and fairly identical RBC clusters. RBCs were stacked following the hexagonal close packing (HCP) structure to form a compact spherical aggr...

A Monte Carlo simulation study on ultrasound backscattering by cell aggregates with poly-disperse cells is discussed. The nuclei in a cell aggregate were assumed as scatterers and the Anderson model was used to obtain backscattering amplitude for each nucleus. The resultant backscatter echo from many particles was determined by using linear superpo...

This study aims to explain the contribution of changes in cellular size variance (CSV) to increases in ultrasound-integrated backscatter (UIB) measured from cell samples undergoing cell death. A Monte Carlo algorithm was used to compare simulations of 2D distributions of cells, uniform (CSV = 0) versus heterogeneous (CSV > 0) and the same mean cell...

A method for the sizing of a cell in suspension by ultrasonic means is discussed. The technique uses frequency minima of the backscatter intensity pattern for an acoustically weak scatterer and provides a simple formula for scatterer size estimation in the framework of the Born approximation. The technique has been implemented here to examine perfo...

A new approximate formula for scattering amplitude of a plane acoustic wave by a sphere is presented. It is based on a similar formula introduced long ago by Hart and Montroll in the context of scattering of light by a sphere. The scattering amplitude is shown to consist of two terms. The first term is related to the scattering amplitude in the mod...

A Monte Carlo study on ultrasound backscattering by red blood cells (RBCs) is presented for three-dimensional (3D) distributions of particles. The cells were treated as classical spherical particles and accordingly, the Boltzmann distribution was considered to describe probability distribution of energy states of a system composed of such particles...

Accuracy of a recently proposed modified Born approximation (MBA) has been examined for size determination of an isolated scatterer. Two methods have been employed for this purpose. One is based on the analysis of the angular scattering pattern of plane waves and the other on analysis of the power spectrum of the backscattered pulse. In each case,...

We present a Monte Carlo study on ultrasound backscattering by three-dimensional distributions of aggregated red blood cells (RBCs). In this study, particles were allowed to interact attractively with neighbors to form aggregates. The interaction potential energy profile between a pair of particles was mimicked by the Morse potential. The strength...

This paper describes step-by-step development of a custom-made measurement system and also provides an assessment of the reliability of the set-up. The angular distribution of the scattered field generated by a sufficiently long cylindrical scatterer in water medium has been measured by this system. The measured values have been compared with the t...

Exploiting the models of Human Visual System based on Gaussian derivatives and their non-localization property in spectral domain, a new design of low pass filter is proposed in this work. The filter is designed by a weighted combination of the Gaussian derivative family which makes the passband of this filter almost equiripple. This design princip...

The validity domain of a modified Born approximation (MBA) has been examined for the scattering of a pulsed plane wave (PPW). This new approximation has been compared with exact results and also with the conventional Born approximation (BA). Comparisons have been made for the scattering by a homogeneous sphere. Error charts have been presented for...

Two new approximations for predicting the elastic scattering of plane acoustic waves by a weak scatterer are proposed. The approximations have been obtained by drawing analogy between acoustic and light scattering problems. The validity of these approximations has been examined numerically for the exactly soluble case of scattering by a homogeneous...

The full text of this letter is given in the PDF file.