Medical Ultrasound Imaging
Saturday, 4 May 2024
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Cross talk is an ultrasound artifact in which strong sound signals in one directional channel leak into another, appearing as a mirror image of the spectral display on the opposite side of the baseline. Cross talk distinguishes the condition of undesired crossover of transmitted sound waves into the receiving transducer in a continuous wave Doppler system. Also called Mirror Artifact. •
The Nyquist frequency describes the highest frequency that can be sampled in a pulsed ultrasound system. To record higher frequencies the zero baseline can be shifted in the desired direction. See also Nyquist Limit, and Sampling Rate. •
Stress echocardiograms are used for detection of coronary artery disease, or to determine the cardiac performance. Stress echocardiograms are less performed to evaluate pulmonary artery pressures, pulmonary hypertension or the significance of valvular heart disease. Stress increases the degree to which the heart contracts. After a myocardial infarction there will be a region of the heart muscle that contracts abnormal at rest. This area may worsen with stress. A coronary artery blockage most often do not impairs the function of the heart at rest. With stress, a region of the heart does not receive enough blood to work effectively and wall motion abnormalities occur. The echocardiographer compares rest and exercise and can determine the presence and severity of a coronary artery blockage. Stress echocardiograms involve: A bicycle stress echocardiogram involves transthoracic echocardiography performed at the rest baseline and after or during different stages of physical exercise. A dobutamine stress echocardiography uses the drug dobutamine instead physical exercise. Transthoracic echocardiograms are routinely performed during stress and rest. Cardiovascular stress represents a minimal risk to the patient. See also Transesophageal Echocardiography, Echocardiography, M-Mode, Curved Transducer, Doppler Ultrasound, History of Ultrasound and History of Ultrasound Contrast Agents.  Further Reading: News & More: •
A phantom is used to control the imaging performance of ultrasound transducers. The spatial resolution, dead zone, linear fidelity, depth of penetration and image uniformity is important for the image quality. For the axial and lateral resolution, the standard definition is the resolution of objects parallel and perpendicular to the path of the sound beam. Ultrasound pictures created by scans of specially designed ultrasound phantoms can quantify the imaging quality and transducer performance. Phantoms contain one or more materials that simulate a tissue in its interaction with ultrasound. Several phantoms are available specifically for quality control. Transducer characterization consists of a standard pulse echo analysis and insertion loss measurement for each probe. The quality variation from the baseline should be tracked over a period. Further Reading: Basics: Result Pages : | Share This Page     Look Ups |
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[last update: 2023-11-06 01:42:00]