![]() Motion artifacts are the result of movement during the data acquisition period. Motion is a very common cause of artifacts in magnetic resonance imaging (MRI). Figure 1D is from a breast MR image in which the phase-encoding direction is oriented horizontally from right to left. Figures 1A through 1C are from an abdominal MR image, and the phase-encoding direction is oriented vertically therefore, the artifact is also seen along this axis. They are observed only in the phase-encoding direction and can be the result of any periodic motion such as respiration, arterial pulsation, or cerebrospinal fluid pulsation.Ĥ. This artifact is referred to as a “ghosting artifact.” Ghosting artifacts appear in abnormal locations as replicas of the moving structure from which they result. There is a subtle high-signal lesion located equidistant to, but left of the aorta along the same horizontal plane as the low-signal lesion in the right hepatic lobe.ģ. Round low-signal lesion in the right hepatic lobe. However, given its location, oriented vertically just above the aorta, a pseudo-lesion as a result of pulsation artifact from the aorta is also in the differential.Ģ. The differential diagnosis of a subtle, T2 bright lesion in the liver includes hemangioma, metastatic disease, and primary liver tumor. Axial fat-suppressed T1W 3D-GRE sequence from a dedicated breast magnetic resonance (MR) image (different patient) demonstrates a round, low-signal lesion in the right hepatic lobe (black arrow) and a round high-signal lesion in the region of the spleen/abdominal wall (white arrow).ġ. Offending artifacts may obscure, distort, or completely misrepresent the true underlying electrophysiological signal sought.F IGURE 1B. These artifact signals may stem from, but are not limited to: light sources monitoring equipment issues utility frequency (50 Hz and 60 Hz) or undesired electrophysiological signals such as EMG presenting on an EEG-, EP-, ECG-, or EOG- signal. In medical electrophysiological monitoring, artifacts are anomalous (interfering) signals that originate from some source other than the electrophysiological structure being studied. ![]() When these assumptions are not maintained, artifacts occur. and acoustic energy of an echo is uniformly attenuated. ![]() These are: echoes originate only from the main ultrasound beam (while there are side lobes and grating lobes apart from the main ultrasound beam) echoes returns to transducer after a single reflection (while an echo can be reflected several times before reaching the transducer) depth of an object relates directly to the amount of time for an echo to reach the transducer (while an echo may reflect several times, delaying the time for the echo return to the transducer) speed of ultrasound in human tissue is constant, echoes travel in a straight path. In ultrasound imaging, several assumptions are made from the computer system to interpret the returning echoes. Physicians typically learn to recognize some of these artifacts to avoid mistaking them for actual pathology. These artifacts may be caused by a variety of phenomena such as the underlying physics of the energy-tissue interaction as between ultrasound and air, susceptibility artifacts, data acquisition errors (such as patient motion), or a reconstruction algorithm's inability to represent the anatomy. In medical imaging, artifacts are misrepresentations of tissue structures produced by imaging techniques such as ultrasound, X-ray, CT scan, and magnetic resonance imaging (MRI). This prediction is a statistical artifact, since it is spurious to use the model when the percentage of citizens making over $50,000 is so high, and gross error to predict an approval rating greater than 100%. For instance, imagine a hypothetical finding that presidential approval rating is approximately equal to twice the percentage of citizens making more than $50,000 annually if 60% of citizens make more than $50,000 annually, this would predict that the approval rating will be 120%. Such an artifact may be called a statistical artifact. In econometrics, which trades on computing relationships between related variables, an artifact is a spurious finding, such as one based on either a faulty choice of variables or an over-extension of the computed relationship. In microscopy, visual artifacts are sometimes introduced during the processing of samples into slide form. In computer science, digital artifacts are anomalies introduced into digital signals as a result of digital signal processing. In natural science and signal processing, an artifact or artefact is any error in the perception or representation of any information introduced by the involved equipment or technique(s). Diffraction spikes and the Airy disk are optical artifacts caused by the diffraction of light through the aperture of an optical system.
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