Enhancement artifacts occur if decreasing of the echo amplitude is not equal with penetration depth caused by inhomogeneous tissue layers and fluids like cysts or air-filled regions. The enhancement artifact appears as a hyperintense (hyperechoic) signal. The attenuation of the ultrasound wave in fluids is much lower as the attenuation in other tissues, therefore tissues distal to fluid are enhanced. Artificial enhancement may also be found distal to a homogeneous solid tumor surrounded by adipose tissue, due to the comparatively high attenuation in fat.

See also Boundary Layer, and Half-Value Layer.

Ultrasound enhancement is the increase in reflection amplitude from objects that lie behind a weakly attenuating structure. Contrast agent particles enhance the reflectivity of blood.
The enhancement artifact may occur in structures below a cyst.

A thyroid ultrasound evaluates the size and shape of the thyroid gland and parathyroid glands. A thyroid ultrasound can show nodules, cysts, tumors, and an enlargement, but a sonogram cannot determine the function of the thyroid. Ultrasound guides the placement of the needle during a thyroid fine needle aspiration biopsy.

See also Sonographic Features, Ultrasound Imaging Modes, Anechoic, Beam Width Artifact and Enhancement Artifact.

Gray scale [also grayscale, grey scale = brit.] produces basically black and white images with series of shades of gray. Solid areas appear white and fluid areas appear black, varying from black at the weakest intensity to white at the strongest. Gray scale resolves artifacts as small as 1 mm. The display is made by transmitting bursts of energy and analyzing the returning signal. Gray scale pictures are limited to the gray scale tones; color pictures display more information because the color is added to the gray scale.
Most ultrasound contrast agents also improve gray scale visualization of the flowing blood to such a degree that the tissue echogenicity increases. Gray scale enhancement of flow in an organ promises to improve lesion detection, along with the ability to differentiate between normal and abnormal areas, using many of the criteria already routinely used in CT and MRI.

See also Compress, Densitometry, Triplex Exam and QB-Mode.

From Hitachi Medical Corporation (HMC), sales, marketing and service in the US by Hitachi Medical Systems America Inc.;
Powerful, flexible, and fast, the HI VISION™ 8500 - EUB-8500 diagnostic ultrasound scanner combines leading edge technologies with user-oriented operation for exceptional imaging and functionality.
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