Development and Evaluation of a Multifrequency Ultrafast Doppler Spectral Analysis (MFUDSA) Algorithm for Wall Shear Stress Measurement: A Simulation and In Vitro Study

Cardiovascular pathology is the leading cause of death and disability in the Western world, and current diagnostic testing usually evaluates the anatomy of the vessel to determine if the vessel contains blockages and plaques. However, there is a growing school of thought that other measures, such as wall shear stress, provide more useful information for earlier diagnosis and prediction of atherosclerotic related disease compared to pulsed-wave Doppler ultrasound, magnetic resonance angiography, or computed tomography angiography. A novel algorithm for quantifying wall shear stress (WSS) in atherosclerotic plaque using diagnostic ultrasound imaging, called Multifrequency ultrafast Doppler spectral analysis (MFUDSA), is presented. The development of this algorithm is presented, in addition to its optimisation using simulation studies and in-vitro experiments with flow phantoms approximating the early stages of cardiovascular disease. The presented algorithm is compared with commonly used WSS assessment methods, such as standard PW Doppler, Ultrafast Doppler, and Parabolic Doppler, as well as plane-wave Doppler. Compared to an equivalent processing architecture with one-dimensional Fourier analysis, the MFUDSA algorithm provided an increase in signal-to-noise ratio (SNR) by a factor of 4–8 and an increase in velocity resolution by a factor of 1.10–1.35. The results indicated that MFUDSA outperformed the others, with significant differences detected between the typical WSS values of moderate disease progression (p = 0.003) and severe disease progression (p = 0.001). The algorithm demonstrated an improved performance for the assessment of WSS and has potential to provide an earlier diagnosis of cardiovascular disease than current techniques allow

The use of Fluid Haemodynamics in the Diagnosis of Cardiovascular Disease

Currently the diagnostic methods used to detect cardiovascular disease largely rely on the inference of the presence of arterial stenosis. There is a clinical interest in the development of a diagnostic screening technique which can indicate the risk of developing cardiovascular disease at an early stage so that non-surgical treatments can be applied. The goal of this work was to develop and validate a diagnostic screening technique for cardiovascular disease using the mechanical biomarker wall shear stress. Improvements in wall shear stress measurements were made by using a 2D Fourier transform to extract additional spectral information from the ultrasound pulse and decrease the spectral variance by integrating across the bandwidth of transmitted frequencies. This technique was validated for a series of anatomically realistic flow phantoms which precisely mimicked the progression of wall stiffening that characterises cardiovascular disease. The newly developed spectral analysis technique demonstrated a higher diagnostic performance than the other techniques tested, both in terms of a greater degree of significance in detecting differences in vessel wall stiffness and in terms of the sensitivity and specificity of the technique. The technique could not be tested in pulsatile flow due to hardware limitations, but preliminary testing indicated that the increased performance of the technique would likely transfer to a physiological flow regime. The results of this work indicated that the algorithm had the potential to rival the diagnostic power of the current gold standard while being applicable at an earlier stage of cardiovascular disease

Doppler Parameters in Renal Transplant Dysfunction

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135678/1/jum2011302169.pd

Dynamic Sonographic Tissue Perfusion Measurement

The amount of blood passing through a tissue is a fundamental parameter since metabolism and its adaptation in disease is reflected by changes of perfusion. To evaluate the functional state of a tissue or an organ it is therefore helpful to know its perfusion intensity. Inflammation for example is highlighted by an increase of perfusion whereas chronic diseases are often accompanied by atrophy of tissue and reduction of organ perfusion. We developed and present here an overview of a simple but sensitive method to quantify tissue perfusion by means of simple color Doppler sonography. This dynamic tissue perfusion measurement (DTPM) uses color hue data to calculate the mean perfusion velocity and color pixel area to calculate the perfused part of a certain region of interest. All data are referred to full heart cycles thus reflecting all changes during a heart beat. With this approach a substantial step forward is made compared to traditional resistance index (RI) or contrast enhanced ultrasound (CEUS) sonographic techniques of blood flow evaluation. This paper describes DTPM basics and shows applications in a variety of fields

Ultrasound Imaging

This book provides an overview of ultrafast ultrasound imaging, 3D high-quality ultrasonic imaging, correction of phase aberrations in medical ultrasound images, etc. Several interesting medical and clinical applications areas are also discussed in the book, like the use of three dimensional ultrasound imaging in evaluation of Asherman's syndrome, the role of 3D ultrasound in assessment of endometrial receptivity and follicular vascularity to predict the quality oocyte, ultrasound imaging in vascular diseases and the fetal palate, clinical application of ultrasound molecular imaging, Doppler abdominal ultrasound in small animals and so on

Hemodynamics in the Stenosed Carotid Bifurcation with Plaque Ulceration

The presence of irregular plaque surface morphology or ulceration of the atherosclerotic lesion has been identified as an independent risk factor for ischemic stroke. Doppler ultrasound (DUS) is the most commonly performed non-invasive technique used to assess patients suspected of having carotid artery disease, but currently does not incorporate the diagnosis of plaque ulceration. Advanced Doppler analyses incorporating quantitative estimates of flow disturbances may result in diagnostic indices that identify plaque ulcerative conditions. A technique for the fabrication of DUS-compatible flow phantoms was developed, using a direct-machining method that is amenable to comprehensive DUS investigations. In vitro flow studies in an ensemble of matched model vessel geometries determined that ulceration as small as 2 mm can generate significant disturbances in the downstream flow field in a moderately stenosed carotid artery, which are detectable using the DUS velocity-derived parameter turbulence intensity (TI) measured with a clinical system. Further experimental results showed that distal TI was significantly elevated (P \u3c 0.001) due to proximal plaque ulceration in the mild and moderately stenosed carotid bifurcation (30%, 50%, 60% diameter reduction), and also increased with stenosis severity. Pulsatile computational fluid dynamics (CFD) models, with simulated particle tracking, demonstrated enhanced flow disruption of the stenotic jet and slight elevations in path-dependent shear exposure parameters in a stenosed carotid bifurcation model with ulceration. In addition, CFD models were used to evaluate the DUS index TI using finite volume sampling