A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Atherosclerosis is a leading cause of cardiovascular death due to the increasing prevalence of the disease and the impact of risk factors such as diabetes, obesity or smoking. Sudden cardiac death is the primary consequence of coronary artery disease in 50% of men and 64% of women. Currently the only available strategy to reduce mortality in the at-risk population is primary prevention; the target population must receive screening for atherosclerosis. The value of screening for subclinical atherosclerosis is still relevant, it has become standard clinical practice with the emergence of new noninvasive techniques (radio frequency [RF] measurement of intima-media thickness [RFQIMT] and arterial stiffness [RFQAS], and flow-mediated vasodilatation [FMV]), which have been used by our team since 2007 and are based on detection marker integrators which reflect the deleterious effect of risk factors on arterial remodeling before the onset of clinical events. These techniques allow the study of values according to age and diagnosis of the pathological value, the thickness of the intima media (RFQIMT), the speed of the pulse wave (RFQAS), and the degree of endothelial dysfunction (FMV). This screening is justified in asymptomatic patients with cardiovascular risk factors (hypertension, diabetes, obesity, dyslipidemia, and tobacco smoking). Studies conducted by RF coupled with two-dimensional echo since 2007 have led to a more detailed analysis of the state of the arterial wall. The various examinations allow an assessment of the degree of subclinical atherosclerosis and its impact on arterial remodeling and endothelial function. The use of noninvasive imaging in screening and early detection of subclinical atherosclerosis is reliable and reproducible and allows us to assess the susceptibility of our patients with risk factors and ensures better monitoring of atherosclerosis, thus reducing the occurrence of cardiovascular events in the long term.

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Screening for subclinical atherosclerosis by noninvasive methods in asymptomatic patients with risk factors

Moving particles and the topographic bed under muddy water or in sediment-laden flow are often clouded by suspended sediments, making it hard to detect or analyze for visualization. This paper concerns applications of ultrasound imaging measurement method for the visual measurement of related water-sand parameters during sediment transport process in hydraulic model experiments. We use a B-mode ultrasound imaging system to measure the related parameters of suspended sediment concentration (SSC), underwater topographic riverbed, flow velocity and sediment incipient motion, conducted at a water channel. A comprehensive measuring system for the visualization of multiple water-sand parameters is established. Results show that the measurement and analysis of SSC and its space distribution, topography bedform, flow velocity and flow field, and sediment incipient velocity can be realized. Ultrasound imaging measurements of SSC and their space distribution can be shown in real time, and also dynamic monitoring and analysis of sediment incipient motion and topography bedform during the sediment transport process. This method realizes the experimental visualization of the topographic bed and sediment-laden flow. Application of an ultrasound imaging measurement system has promoted the development of sediment movement law research and related hydraulic model experiment measurement technique.

Applications of ultrasound imaging system for measuring water-sand parameters during sediment transport process in hydraulic model experiments

Non-invasive imaging is widely used to assess vascular dysfunction, including measurement of flow-mediated vasodilatation of the brachial artery (FMD), pulse wave velocity (PWV), the augmentation index (AI), and central blood pressure. Endothelial dysfunction, a main contributor of atherosclerosis is possible diagnostic tool by FMD. An arterial stiffness, assessing by the PWV and/or arterial dispensability and beta stiffness index have been associated with cardiovascular risk. Ultrasound-based methods are used to assess elastic properties of the arterial walls in studies of arterial stiffness and atherosclerosis. In asymptomatic individuals is essential in order to detect, predict and prevent cardiovascular diseases first be estimated based on the global assessment of risk factors? Nowadays is recommended in daily routine screening for coronary artery disease in asymptomatic individuals with intermediate (10-20% 10-year risk of coronary artery disease) or high risk (>20% 10-year risk of coronary artery disease) to provide a further screening.

/pdf/the-role-of-noninvasive-imaging-for-detection-high-risk-4whiqb9mwl.pdf

The Role of Noninvasive Imaging for Detection High Risk Patients with Subclinical Atherosclerosis

To study the influence caused by sampling,here a method,in which the comb function was introduced to sample the fringe patterns,was adopted.Combining with the knowledge of the convolution properties,the phase error caused by sampling in practical composite Fourier-transform propfilometry was discussed along two directions,one is along the phrase variation direction and the other is the vertical direction.The criterions for the selection of sampling frequency are derived respectively along both the directions,and the results indicate that the sampling frequency along the phrase variation direction must be at least four times as the fundamental frequency in order to avoid the spectrum overlapping,and along the orthogonal direction the sampling frequency must be at least three times as the larger frequency of the two carrier frequencies.The computer simulation and experiments verify the theories.

Influence of sampling on composite Fourier-transform propfilometry

Non-invasive measurement of the multiple velocity component of blood flow would be extremely useful for hemodynamic diagnosis of many cardiovascular problems such as athermoma, intimal hyperplasia, thrombus, and hemolysis. In recent years, Zheng et al. have developed a new ultrasound based velocimetry technique, termed echo particle image velocimetry (echo PIV) to measure the multiple velocity components. Based on the technique, we had optimize the velocimetry algorithm which is used for processing images and generating vectors, to improve the accuracy of the vectors and reduce computational cost of the algorithm.

A new velocimetry algorithm for optimizing ultrasonic PIV imaging method

To study the influence caused by sampling, here the method, in which the pectinate function was introduced to sample the fringe patterns, was adopted. Basing the knowledge of the convolution theorem, the phase error caused by sampling in practical composite Fourier-transform profilometry (CFTP) was discussed along two directions. The criterions for the selection of sampling frequency are derived and the results indicate that to avoid the spectrum overlapping, the sampling frequency along the phrase variation direction must be at least four times as the fundamental frequency, and along the orthogonal direction it must be at least three times as the larger frequency of the two carrier frequencies. The computer simulations and practical experiments verified the theories.

Influence of sampling on composite structured light pattern

We have recently developed an ultrasonic targeted imaging technique by taking advantage of wideband transient high frequency acoustic emission from ultrasound contrast agents. The imaging sequence includes a B-mode imaging pulse sequence in which a short pulse is transmitted with the outer low frequency arrays and received with the inner high frequency array (TLRH: transmit at low frequency and receive at high frequency), followed by a long radiation force pulse to induce immediate bubble adhesion using the center array, and a second B-mode imaging pulse sequence. The RF data obtained from the second B-mode pulse sequence is averaged and then subtracted by that from the first B-mode sequence. The imaging technique was tested in a targeted imaging phantom, where lipid-shelled biotin microbubbles flow within an avidin coated-cellulose. Results showed that tissue signals were suppressed up to 33 dB and a targeted bubble contrast-to-free bubble signal ratio of up to 23 dB was obtained from the composite sequence imaging.

Hairong Zheng

Papers

A new velocimetry algorithm for optimizing ultrasonic PIV imaging method

Influence of sampling on composite structured light pattern

A novel signal processing and imaging method for ultrasonic molecular imaging