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Theses, Masters


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1.3 PHYSICAL SCIENCES, Atomic, Molecular and Chemical Physics

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Successfully submitted for the award of Master of Philosophy (M.Phil) to the Dublin Institute of Technology, 2009.


Renal Artery stenosis is one of the major causes of curable renovascular hypertension.An early investigation of renal artery stenosis helps in the management of renovascular hypertension by alternative, less-invasive methods such as drug treatments, thereby reducing the risk involved in the surgery. Therefore an early investigation of renal artery stenosis has been always an attractive goal for the physicians. The renal artery stenosis affects the blood velocity profile in the renal artery. These profiles can be investigated by quantitative Doppler Ultrasound measurements obtained by flow experimentations and can be used as a tool for the identification of renal artery stenosis. In the present study, the velocity profiles produced in anatomically realistic renal artery wall-less flow phantoms were investigated by physiological flow experimentations. The renal artery flow phantoms mimic renal vasculature anatomically and acoustically as well as representing symmetrical (30%, 50% and 70%) and asymmetrical (25%, 35% and 45%) stenosis conditions. A physiological flow of velocity between 2 – 40 cms-1 was produced in each renal artery flow phantom. The blood mimicking fluid (BMF) velocity was determined at regular axial and radial intervals of 1mm, using Siemens Antares Ultrasound system with a broadband curvilinear transducer (C5-2). The physiological velocity profiles in each phantom were investigated. By studying the characteristics of the physiological velocity profiles in the
anatomically realistic renal flow phantoms, a greater understanding of renal flow behavior in the normal and diseased conditions can be obtained. These flow characteristics can serve as a basis for identification and quantification of the degree of stenosis. The flow characteristics in the investigated velocity profiles may lead to earlier detection of renal artery stenosis using noninvasive ultrasonic methods. Subcutaneous fat is a well documented limitation of renal imaging. Recent studies have indicated that the subcutaneous fat introduces an error in the maximum velocity estimation and
thereby in the quantification of degree of stenosis. In the present thesis, the effect of a fat mimicking layer on: a) physiological velocity profiles and b) the shape and profile of Spectral Doppler velocity waveforms was studied. The knowledge of how the subcutaneous fat affects the physiological waveforms and thereby the clinical diagnosis is important while using the physiological flow waveforms and the physiological velocity profiles as a criteria for identification of renal artery stenosis.



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