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Step-frequency continuous-wave (SFCW) modulation can have a role in the detection of small unmanned aerial vehicles (UAV) at short range (less than 1-2 km). In this paper, the theory of SFCW range detection is reviewed, and a spec...
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Step-frequency continuous-wave (SFCW) modulation can have a role in the detection of small unmanned aerial vehicles (UAV) at short range (less than 1-2 km). In this paper, the theory of SFCW range detection is reviewed, and a specific method for correcting the possible range shift due to the Doppler effect is devised. The proposed method was tested in a controlled experimental set-up, where a free-falling target (i.e., a corner reflector) was correctly detected by an SFCW radar. This method was finally applied in field for short-range detection of a small UAV.
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Aims: We recently reported the feasibility of the average pixel intensity (API) method for grading mitral regurgitation (MR) in a heterogeneous MR population. Since mitral valve prolapse (MVP) is an important cause of primary MR, ...
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Aims: We recently reported the feasibility of the average pixel intensity (API) method for grading mitral regurgitation (MR) in a heterogeneous MR population. Since mitral valve prolapse (MVP) is an important cause of primary MR, we more specifically investigated the feasibility of the API method and the MR flow dynamics in patients with MVP.
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Mitral regurgitation (MR) is one of the most common valvular lesions that are readily identified by transthoracic echocardiography. Color Doppler imaging is the modality of choice for the recognition of MR, and it plays an importa...
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Mitral regurgitation (MR) is one of the most common valvular lesions that are readily identified by transthoracic echocardiography. Color Doppler imaging is the modality of choice for the recognition of MR, and it plays an important role in the assessment of regurgitation severity. Continuous wave (CW) Doppler is commonly used to interrogate the MR signal, and this modality can provide highly useful data regarding several physiological and pathological parameters. In this manuscript, we present a series of cases that illustrate the various hemodynamic parameters that can be derived from analysis of the CW Doppler signal of MR.
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Background: Peak systolic velocity (PSV) is measured with pulse-wave (PW) Doppler with angle correction in patients with internal carotid artery stenosis (ICAS). However, the correlation between conventional angiography and PSV sh...
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Background: Peak systolic velocity (PSV) is measured with pulse-wave (PW) Doppler with angle correction in patients with internal carotid artery stenosis (ICAS). However, the correlation between conventional angiography and PSV shows considerable scattering. We hypothesized that measuring PSV without angle correction would lead to better inter-rater reliability. This hypothesis was tested using a sector probe and continuous-wave (CW) Doppler without angle correction. Methods: Consecutive patients with more than 50% ICAS were enrolled from a prospective database. PSV was measured with PW Doppler with angle correction (PW PSV) and CW Doppler without angle correction (CW PSV) by 2 examiners. The inter-rater reliabilities of PW PSV and CW PSV were analyzed by Spearman's rank correlation test. Results: A total of 37 ICAS sites (median 67 [interquartile range 57-78] % stenosis) were enrolled. Measuring PSV using a sector probe insonating nearly parallel to the flow was feasible in all cases. Inter-rater reproducibility of CW PSV (Spearman's rho = .810) was similar to that of PW PSV (Spearman's rho = .796). When limited to patients with a PSV greater than 200 cm/s with both PW Doppler examinations (25 ICAS sites), inter-rater reliability was relatively higher for CW PSV (Spearman's rho = .674) than for PW PSV (Spearman's rho = .423). Conclusions: Measuring PSV with CW Doppler using a sector probe was feasible. Inter-rater reliability was similar between PW Doppler with angle correction and CW Doppler without angle correction in evaluating PSV in patients with ICAS. CW Doppler appears to have better inter-rater reproducibility than PW Doppler in assessing high PSV. (C) 2016 National Stroke Association. Published by Elsevier Inc. All rights reserved.
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The impact of coronary artery disease (CAD) on all-cause mortality and overall disabilities is well-established. Percutaneous and/or surgical coronary revascularization procedures dramatically reduced the occurrence of adverse car...
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The impact of coronary artery disease (CAD) on all-cause mortality and overall disabilities is well-established. Percutaneous and/or surgical coronary revascularization procedures dramatically reduced the occurrence of adverse cardiovascular events in patients suffering from atherosclerosis. Specifically, guidelines from the European Society of Cardiology on the management of myocardial revascularization promoted coronary artery by-pass graft (CABG) intervention in patients with specific alterations in the coronary tree due to the higher beneficial effects of this procedure as compared to the percutaneous one. The left internal mammary artery (LIMA) is one of the best-performing vessels in CABG procedures due to its location and its own structural characteristics. Nevertheless, the non-invasive assessment of its patency is challenging. Doppler ultrasonography (DU) might perform as a reliable technique for the non-invasive evaluation of the patency of LIMA. Data from the literature revealed that DU may detect severe (>70%) stenosis of the LIMA graft. In this case, pulsed-wave Doppler might show peak diastolic velocity/peak systolic velocity < 0.5 and diastolic fraction < 50%. A stress test might also be adopted for the evaluation of patency of LIMA through DU. The aim of this narrative review is to evaluate the impact of DU on the evaluation of the patency of LIMA graft in patients who undergo follow-up after CABG intervention.
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AN APPRECIATION of the utility of echocardiographic Doppler spectral profile analysis in diagnosing cardiac pathology and guiding surgical intervention more than justifies an investment in obtaining proficiency in these skills. Gi...
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AN APPRECIATION of the utility of echocardiographic Doppler spectral profile analysis in diagnosing cardiac pathology and guiding surgical intervention more than justifies an investment in obtaining proficiency in these skills. Given the relatively low incidence of significant complications associated with transesophageal echocardiographic examination, the facile use of both spectral and color Doppler principles to diagnose unusual pathology is essential. Doppler modalities are used to characterize blood flow, pressure gradients, chamber dimensions, and other anatomic and physiological parameters. The authors present a case in which several Doppler principles were used to evaluate and diagnose the etiology of dyspnea and a high aortic valve gradient. ? 2022 Elsevier Inc.
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This review pays tribute to those pioneers in Doppler flow during an early and exciting period ranging from the end of the 1960s to the 1990s. Three major 'approaches' contributed to what is nowadays built into every patient's inv...
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This review pays tribute to those pioneers in Doppler flow during an early and exciting period ranging from the end of the 1960s to the 1990s. Three major 'approaches' contributed to what is nowadays built into every patient's investigation. The source was Daniel Kalmanson, who developed flow directionality, assigning a physiological meaning to the recordings. This was the first time Doppler flow was used on the heart, providing new insights in cardiac pathophysiology. The second approach relied on the Norwegian group who applied the laws of physics to fluid dynamics. Simplification of the formula provided a new non-invasive approach enabling quantification of valvular lesions and haemodynamic measurements. This new tool pushed back previous routine catheterisation. To crown it all, the introduction of colour Doppler flow, mainly relying on the Japanese groups, overcame the long-lasting scepticism of the scientific community: cardiologists started to 'believe' in the Doppler technique. Other innovative pioneers around the world joined the three groups to develop this new field of cardiology. At the turning of the new millennium, the Doppler technique is mature, through a strong methodology. Convergence of the three original approaches for mutual benefit, constant update of examination modalities according to improved technology, and new insights into cardiac dynamics, are the three cornerstones supporting this methodology. They should contribute to keep it alive and efficient, independently of the imaging modality of the future.
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To the Editor: Routine fetal heart examination is performed in the obstetric office using a portable continuous Wave Doppler (CWD) device [1], which produces sounds but not images. We explored the heart in adult patients using thi...
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To the Editor: Routine fetal heart examination is performed in the obstetric office using a portable continuous Wave Doppler (CWD) device [1], which produces sounds but not images. We explored the heart in adult patients using this method and we found it to be surprisingly informative. We decided then to define cardiac auscultation points and typical auditive patterns for the procedure. After that, we compared this method with classic auscultation (CA) in cardiologic patients, using color Doppler echocardiography (CDE) as a gold standard.
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Ways to measure blood perfusion using ultrasound techniques such as continuous-wave Doppler, pulsed Doppler, colour Doppler and power Doppler will be reviewed. From a certain standpoint, blood perfusion may be defined as the diffe...
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Ways to measure blood perfusion using ultrasound techniques such as continuous-wave Doppler, pulsed Doppler, colour Doppler and power Doppler will be reviewed. From a certain standpoint, blood perfusion may be defined as the difference betweenarterial inflow and arterial outflow from a considered volume, i.e. capillary flow. The low velocities and small blood volumes involved make the signal-to-noise ratio, dynamic range and frequency resolution critical factors in the detection system.Another limiting factor is tissue motion which obscures the blood signal. Perfusion may still under certain conditions be estimated with the first moment of the Doppler power spectrum, as obtained with any Doppler ultrasound method. Modern flow mappingtechniques also make it possible to estimate perfusion by counting the number of pixels that indicate flow, but low flow velocities cannot be included in the estimate. Future high-frequency systems may. however. provide very detailed images of minute flow distributions in superficial layers. Contrast agents are widely used today to enhance the blood signal, and a technique named harmonic imaging can suppress movement artefacts from surrounding tissue. Transient signals from disrupting contrast agentparticles in an ultrasound field can potentially be used for perfusion quantification. Future developments to extract the blood flow signal from its noisy environment, aside from contrast agents. may he multiple sample volumes, frequency compoundingand/or improved signal processing. The lack of an adequate perfusion phantom for verification of measurements of microcirculatory flow becomes, however, more apparent with improved detectability of slow flows.
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The paper describes an innovative ultrasound imaging method called Doppler Tomography (DT), otherwise known as Continuous Wave Ultrasonic Tomography (CWUT). Thanks to this method, it is possible to image the tissue cross-section i...
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The paper describes an innovative ultrasound imaging method called Doppler Tomography (DT), otherwise known as Continuous Wave Ultrasonic Tomography (CWUT). Thanks to this method, it is possible to image the tissue cross-section in vivo using a simple two-transducer ultrasonic probe and using the Doppler effect. It should be noted that DT significantly differs from the conventional ultrasound Doppler method of measuring blood flow velocity. The main difference is that when measuring blood flow, we receive information with an image of the velocity distribution in a given blood vessel (Nowicki, 1995), while DT allows us to obtain a cross-sectional image of stationary tissue structure. In the conventional method, the probe remains stationary, while in the DT method, the probe moves and the examined tissue remains stationary.This paper presents a method of image reconstruction using the DT method. First, the basic principle of correlation of generated Doppler frequencies with the location of inclusions from which they originate is explained. Then the exact process and algorithm in this method are presented. Finally, the impact of several key parameters on imaging quality is examined. As a result, the conclusions of the research allow to improve the image reconstruction process using the DT method.
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