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Analyzing and understanding the movement of the mitral valve is of vital importance in cardiology, as the treatment and prevention of several serious heart diseases depend on it. Unfortunately, large amounts of noise as well as a highly varying image quality make the automatic tracking and segmentation of the mitral valve in two-dimensional echocardiographic videos challenging. In this paper, we present a fully automatic and unsupervised method for segmentation of the mitral valve in two-dimensional echocardiographic videos, independently of the echocardiographic view. We propose a bias-free variant of the robust non-negative matrix factorization (RNMF) along with a window-based localization approach, that is able to identify the mitral valve in several challenging situations. We improve the average f1-score on our dataset of 10 echocardiographic videos by 0.18 to a f1-score of 0.56.

We consider the problem of identifying frames in a cardiac ultrasound video associated with left ventricular chamber end-systolic (ES, contraction) and end-diastolic (ED, expansion) phases of the cardiac cycle. Our procedure involves a simple application of non-negative matrix factorization (NMF) to a series of frames of a video from a single patient. Rank-2 NMF is performed to compute two end-members. The end members are shown to be close representations of the actual heart morphology at the end of each phase of the heart function. Moreover, the entire time series can be represented as a linear combination of these two end-member states thus providing a very low dimensional representation of the time dynamics of the heart. Unlike previous work, our methods do not require any electrocardiogram (ECG) information in order to select the end-diastolic frame. Results are presented for a data set of 99 patients including both healthy and diseased examples.

A back-end processing system involving high-speed signal processing functions to form and exhibit an image is developed for real-time visualization of the mouse heart. The studies have shown that high-speed back-end processing system is capable of providing high spatial resolution images with fast temporal resolution.

3-D images of both 5 pairs of nylon wires embedded in a clear gelatin phantom and an 8 mm diameter cylindrical anechoic cyst phantom acquired from a 256 * 256 2-D array transducer made from a 1-3 composite are described. The cross-section of the cyst is visible in the azimuth B-scan whereas the long axes are observed as a rectangle in the elevation B-scan and C-scans.

The article discusses a recently developed technique called the dual apodization with cross-correlation (DAX), which is used for the novel sidelobe and clutter suppression in ultrasound imaging. DAX is shown to be extremely useful in improving the contrast-to-noise ratio, which then leads to an easier visualization of anechoic cysts and blood vessels.

The design of a low-cost bipolar pulse generator for high-frequency (HF) ultrasound applications is described. The pulse generator can generate N cycle bipolar pulses with center frequency over 60 MHz and the pulser can be used in high-frequency ultrasound Doppler and B-mode imaging applications with arrays.

Three acquisition strategies are presented that use synthetic aperture techniques with 2-D arrays, each of which prioritizes volume acquisition time, resolution, or sensitivity. A two-dimensional (2-D) array of 256 x 256 = 65,536 elements, with total area 4 x 4 = 16 cm.sup.2, serves as a flexible platform for developing acquisition schemes for 3-D rectilinear ultrasound imaging at 10 MHz using synthetic aperture techniques.

A digital field programmable gate array (FPGA)-based, real-time, high frequency beamformer was implemented in FPGA chip, which reduces hardware complexity. The results showed that the 30 MHz array has the -6 dB width of 68 mum in axial and 370 mum in lateral direction at 6.4mm.

A real-time 3-D rectilinear scanner using a 4:1 receive mode multiplexing with a 2-D array containing over 65,000 elements to improve the image quality compared to that of previous periodic array is developed. Theoretical simulations and analysis reveal an increase of about 13 dB in sensitivity.

A real-time rectilinear volumetric scanning system is described. Such a system could be useful for abdominal, breast, or vascular imaging, especially for real-time interventional radiological procedures.