Showing papers by "Osama M. Mukdadi published in 2008"

Noninvasive assessment of human jawbone using ultrasonic guided waves

Abstract: The problem of detecting defects in jawbones is an important problem. Existing methods based on X-rays are invasive and constrain the achievable image quality. They also may carry known risks of cancer generation or may be limited in accurate diagnosis scope. This work is motivated by the lack of current imaging modalities to accurately predict the mechanical properties and defects in jawbone. Ultrasonic guided waves are sensitive to changes in microstructural properties and thus have been widely used for noninvasive material characterization. Using these waves may provide means for early diagnosis of marrow ischemic disorders via detecting focal osteoporotic marrow defect, chronic nonsuppurative osteomyelitis, and cavitations in the mandible (jawbone). Guided waves propagating along the mandibles may exhibit dispersion behavior that depends on material properties, geometry, and embedded cavities. In this work, we present the first study in the theoretical and experimental analysis of guided wave propagation in jawbone. Semianalytical, finite-element (SAFE) method is used to analyze dispersion behavior of guided waves propagating in human mandibles. The geometry of the cross section is obtained by segmenting the computed tomography (CT) images of the jawbone. The cross section of the mandible is divided in two regions representing the cortical and trabecular bones. Each region is modeled as a linear Hookean material. The material properties for both regions are adopted from the literature. The experimental setup for the guided waves experiment is described. The results from both numerical analysis and guided waves experiment exhibit variations in the group velocity of the first arrival signal and in the dispersion behavior of healthy and defected mandibles. These results shall provide a means to noninvasively characterize the jawbone and accurately assess the bone mechanical properties. Our study is not aimed at characterizing the bone density in human mandibles. Rather, it is aimed to assess bone mechanical properties and defects that cannot be diagnosed by X-ray or other imaging modalities. This work may pave the way to the development of inexpensive noninvasive devices to detect small defects in human mandibles.

High frequency precise ultrasound imaging system to assess mouse hearts and blood vessels

Abstract: Genetically modified mice provide a powerful tool for understanding the molecular mechanisms and pathogenesis of human cardiovascular diseases like human atherosclerosis [1]. Numerous mouse strains are available today with phenotypes relevant to human cardiovascular diseases [1,2]. These mouse strains have prompted the development of techniques for assessing the cardiovascular function and morphology of living mice. Recently, several imaging techniques have been emerged as promising non-invasive imaging modalities, such as electron-beam computed tomography, magnetic resonance imaging, positron emission tomography, optical coherent tomography, and ultrasound biomicroscopy (UBM) [3,4]. Although these systems are capable of detecting anatomic and functional information, they may not be suitable to image mouse heart vasculatures. The small size and rapid movement of mouse hearts require systems acquiring images using temporal resolution of less than 10 ms with spatial resolution of 100 μm or less [4]. However, in mice, which have extremely small coronary arteries and high heart rates, the coronary circulation constitutes a great challenge for these available imaging techniques.Copyright © 2008 by ASME

Noninvasive Measurement of Brachial Wall Mechanics During Flow-Mediated Vasodilation Using 2D Ultrasound Strain Tensor Imaging

Abstract: Atherosclerosis has become one of the contributing factors of cardiovascular diseases. Endothelial dysfunction is considered a key factor in the development of atherosclerosis [1]. Flow-mediated vasodilatation (FMD) measurement in brachial and other conduit arteries has become a common method to asses the endothelial function in vivo [2]. Fluid shear-stress increases due to blood flow increases, thus stimulating endothelial cell production and release of nitric oxide, a potent endogenous vasodilator. The mechanical behavior of the arterial wall during vasodilatation is considered an indication for endothelial health. In FMD measurement, the endothelium-dependent variation in arterial diameter in response to reactive ischemia-induced hyperemia is measured by comparing the luminal diameter of the brachial artery before and after the ischemia of the forearm induced by pressurizing a cuff [3]. Ultrasound imaging modalities has been widely used in the FMD analysis as a noninvasive low-cost tool, which can be used to track the arterial diameter change with time. Most of the FMD measurements in the literature are based on tracing the vessel wall boundary manually. Since this process is time consuming and may introduce human errors, automatic measurement techniques have been implemented [3,4]. These techniques utilize image processing algorithms to identify the edges of arterial walls, and then calculate the relative displacement change with time.Copyright © 2008 by ASME