Measurement of flow-mediated vasodilatation (FMD) in brachial and other conduit arteries has become a common
method to asses the status of endothelial function in vivo. In spite of the direct relationship between the arterial wall
multi-component strains and FMD responses, direct measurement of wall strain tensor due to FMD has not yet been
reported in the literature. In this work, a noninvasive direct ultrasound-based strain tensor measuring (STM) technique is
presented to assess changes in the mechanical parameters of the vascular wall during FMD. The STM technique utilizes
only sequences of B-mode ultrasound images, and starts with segmenting a region of interest within the artery and
providing the acquisition parameters. Then a block matching technique is employed to measure the frame to frame local
velocities. Displacements, diameter change, multi-component strain tensor and strain rates are then calculated by
integrating or differentiating velocity components. The accuracy of the STM algorithm was assessed using a phantom
study, and was further validated using in vivo data from human subjects. Results indicate the validity and versatility of
the STM algorithm, and describe how parameters other than the diameter change are sensitive to pre- and post-occlusion,
which can then be used for accurate assessment of atherosclerosis.
The use of ultrasound in dentistry is still an open growing area of research. Currently, there is a lack of imaging
modalities to accurately predict minute structures and defects in the jawbone. In particular, the inability of 2D
radiographic images to detect bony periodontal defects resulted from infection of the periodontium. This study
investigates the feasibility of high frequency ultrasound to reconstruct high resolution 3D surface images of human
jawbone. Methods: A dentate and non-dentate mandibles were used in this study. The system employs high frequency
single-element ultrasound focused transducers (15-30 MHz) for scanning. Continuous acquisition using a 1 GHz data
acquisition card is synchronized with a high precision two-dimensional stage positioning system of ±1 μm resolution for
acquiring accurate and quantitative measurements of the mandible in vitro. Radio frequency (RF) signals are acquired
laterally 44-45.5 μm apart for each frame. Different frames are reconstructed 500 μm apart for the 3D reconstruction.
Signal processing algorithms are applied on the received ultrasound signals for filtering, focusing, and envelope
detection before frame reconstruction. Furthermore, an edge detection technique is adopted to detect the bone surface in
each frame. Finally, all edges are combined together in order to render a 3D surface image of the jawbone. Major
anatomical landmarks on the resultant images were confirmed with the anatomical structures on the mandibles to show
the efficacy of the system. Comparison were also made with conventional 2D radiographs to show the superiority of the
ultrasound imaging system in diagnosing small defects in the lateral, axial and elevation planes of space. Results: The
landmarks on all ultrasound images matched with those on the mandible, indicating the efficacy of the system in
detecting small structures in human jaw bones. Comparison with conventional 2D radiographic images of the same
mandible showed superiority of the 3D ultrasound images in detecting defects in the elevation plane of space. These
results suggest that the high frequency ultrasound system shows great potential in providing a non-invasive method to
characterize the jawbone and detect periodontal diseases at earlier stages.
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