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In this patient, the hernia is in the linea alba (between the rectus muscles) and it contains only fat. The video clip demonstrates small movements of herniated fat while the patient is bearing down with no evidence of bowel involvement. The movement of the herniated structure is an ensuring sign that the herniated structure is neither incarcerated nor strangulated.

http://minipcreview.com/?post_type=post Speed Displacement and Refraction Artifact


best tadalafil brands in india The speed of sound within a material is dependent on its density and elastic properties. Ultrasound image processing assumes a constant speed of sound in human tissue of 1540 m/sec. In clinical sonography, the ultrasound beam may encounter a variety of materials such as air, fluid, fat, soft tissue, and bone. When sound travels through material with a velocity significantly slower than the assumed 1540 m/sec, the returning echo will take longer to return to the transducer. The image processor assumes that the length of time for a single round trip of an echo is related only to the distance traveled by the echo. The echoes are thus displayed deeper on the image or further lateral than they really are. This is referred to as the speed displacement artifact; in clinical imaging, it is often recognized when the ultrasound beam encounters an area of focal fat such as perirenal fatty tissue in this case. A change in velocity of the ultrasound beam as it travels through two adjacent tissues with different density and elastic properties may produce a refraction artifact. In refraction, nonperpendicular incident ultrasound energy encounters an interface between two materials with different speeds of sound. When this occurs, the incident ultrasound beam changes direction. The degree of this change in direction is dependent on both the angle of the incident ultrasound beam and the difference in velocity between the two media. The ultrasound display assumes that the beam travels in a straight line and thus misplaces the returning echoes to the side of their true location. In clinical imaging, this artifact may also be recognized in pelvic structures deep to the junction of the rectus muscles and midline fat. Refraction artifact may cause structures to appear wider than they actually are or may cause an apparent duplication of structures as demonstrated in this case in the upper pole of the left kidney which is disappeared with deep breathing when the kidney is located.
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