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Ultrasonic backscatteredsignals contain information regarding the scatterer structures of the imaged biological tissues; a uniform scatterer distribution could be represented by periodicities in the backscattered signals. This work aims to characterize these scatterer periodicities using wavelet improved cepstral analysis. This technique was tested on simulated ultrasound signals, where the periodicity...
Understanding of the propagation of ultrasound through a bubbly medium is a challenging task because of the nonlinear dynamics of the bubbles and their effect on the attenuation and sound speed of the medium. The majority of the studies on this subject apply linear models, which will generate inaccurate results, especially at higher-pressure excitations. These studies have also ignored the effect...
We present a new technique for photoacoustic (PA) image formation, termed ‘F-Mode’, which capitalizes on variations in the power spectrum of PA signals to produce images with object specific contrast. The technique is applied to a PA dataset by calculating the signal power spectrum at each scan location, segmenting it into discrete frequency bands, and then forming an image representing the spatial...
Lipid-stabilized microbubbles are used in various clinical ultrasound (US) applications such as diagnostics imaging and therapeutics. The characteristics of the microbubbles such as size, shell material, and US frequency dictate the acoustic response of these microbubbles. Therefore, monodispersed microbubbles with the length-scale (1–7 μm in diameter) relevant to the biomedical ultrasound applications...
Photoacoustic (PA) imaging has been proposed for cancer treatment monitoring. Tumor oxygen saturation (sO2) should in principle be related to vascular parameters such as blood flow. In this work, in-vivo PA estimates of sO2 were compared to power Doppler (pD) measures of vascularity hours after the administration of microbubbles (MB), radiation therapy (XRT), individually or combined (MB-XRT).
The usage of microbubbles (MBs) is limited to the blood pool due to their large size yet the detection of biomarkers on tumor cells and effective drug delivery, require MBs to reach the tumor tissue outside of the vasculature. To tackle these problems, nanobubbles (NBs) are proposed as a potential alternative. NBs can pass through submicron blood vessels and extravasate to tissue. Due to their higher...
Our group has previously demonstrated that lower shear rate in the pulsatile blood flow yields greater red blood cell (RBC) aggregation which in turn results in a higher oxygen saturation (sO2) level and a higher photoacoustic (PA) signal. Higher shear rates led to disaggregation thereby decreasing the PA signal amplitude and the sO2. These results suggest that the interrelationship between the sO...
Understanding of the propagation of ultrasound through a bubbly medium is a challenging task because of the nonlinear dynamics of the bubbles and their effect on the attenuation and sound speed of the medium. The majority of the studies on this subject apply linear models, which will generate inaccurate results, especially at higher-pressure excitations. These studies have also ignored the effect...
Microbubbles (MBs) excited by ultrasound (Us) are used as contrast agents for the detection of blood vessels. MBs can also be used to enhance drug delivery. However, the usage of MBs is limited to the blood pool due to their large size; where detection of biomarkers on tumor cells and effective drug delivery, requires MBs to reach the tumor tissue outside of the vasculature.
Most chemotherapeutics (CTs) are delivered systemically, causing nausea, hair loss, fatigue and a compromised immune system. Biocompatible in situ forming implants (ISFIs) are drug delivery vehicles which are injected as a liquid before solidifying in tissues and ultimately breaking down. By dissolving CTs in an ISFI solution, they can be injected directly to the tumour site and released in a controllable...
Imaging speckle arises from the interference of waves from randomly distributed sources. Here, we provide a theoretical basis and experimental evidence for the presence of speckle in photoacoustic (PA) imaging across multiple ultrasonic (US) detection frequencies.
We develop a new microfluidic technique to generate lipid-stabilized microbubbles of 1–7 μm diameter. We shrink microbubbles that are initially O(100) μm in diameter by using a vacuum system. We use a polydimethylsiloxane (PDMS) microfluidic device to generate microbubbles in a conventional flow focusing orifice. The bubbles pass through a serpentine channel while under vacuum pressure, and shrink...
Advances in ultrasound technology have fueled the emergence of Point-Of-Care Ultrasound (PoCU) imaging, including improved ease-of-use, superior image quality, and lower cost ultrasound. One of the approaches that can make the adoption of PoCU universal is to make the data acquisition module as simple as a "stethoscope" while further processing and image construction can be done using cloud-based...
Photoacoustic or PA waves, generated from blood cells, create distinct spectral features in the Fourier domain, for example, maxima and minima. In this way, high-frequency PA signals can be used to identify and distinguish blood cells. However, due to finite bandwidth of physical systems, many interesting Fourier features are invisible within the observed bandwidth. To overcome this challenge, we...
Cancer is a major public health problem all over the world. It is currently the second leading cause of death in the United States, and is expected to surpass heart diseases as the leading cause of death in the next few years. To overcome this problem, researchers are discovering new treatments and developing imaging technologies that can aid in early detection of cancer. In this work, we investigate...
Scattering from the extracellular matrix (ECM) is currently being investigated, using a decellularization technique, which involves removing cells from tissue while preserving the ECM. This work aims to investigate the use of the mean scatterer spacing, using cepstral analysis techniques, for the differentiation between cellularized and decellularized mouse kidneys. After decellularization, the mean...
In the last decade, photoacoustic techniques have been used extensively to acquire label free oxygen saturation (SO2) images of blood vessels both in vivo and ex vivo. Recent advances in photoacoustic microscopy have pushed the in vivo resolution limit of photoacoustic SO2 mapping to that of a single cell. In this work, we use a photoacoustic microscope equipped with a 0.9 GHz ultrasound transducer...
Plane wave ultrasound imaging (PW) with coherent compounding can improve the image quality in terms of contrast, SNR, and lateral resolution compared to the conventional PW method. When the number of PW transmissions is small, the image quality still need improvement. In this paper, we proposed to first estimate the synthetic transmit aperture imaging (STA) data with regularized singular-value decomposition...
High frequency ultrasound measurements were made of sea urchin oocytes at 40 MHz and compared to numerical simulations. The urchin oocytes are non-nucleated cells, and have uniform size and biomechanical properties; thus, the signals measured from each cell are similar, unlike typical nucleated mammalian cells. The power spectra calculated from the measured time domain signals were periodic, with...
The complex scattering of ultrasound from biological tissues is not fully understood. The relationship between tissue structure and scattering is further complicated by variations in scattering sources and number density with varied imaging frequency. Above 100 MHz, where the resolution volume is on the order of a cell, single cells have been well studied, but not collections of cells. Over the range...
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