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Ultrasound is defined by the American National Standards Institute as "sound at frequencies greater than 20 kHz". In air at atmospheric pressure, ultrasonic waves have wavelengths of 1.9 cm or less. Ultrasound can be generated at very high frequencies; ultrasound is used for sonochemistry at frequencies up to multiple hundreds of kilohertz.
Brachydactyly type D, also known as short thumb, [3] [1] stub thumb, [5] [6] or clubbed thumb, [5] [6] is a genetic trait recognised by a thumb being relatively short and round with an accompanying wider nail bed. The distal phalanx of such thumbs is approximately two-thirds the length of full-length thumbs.
Medical ultrasound includes diagnostic techniques (mainly imaging techniques) using ultrasound, as well as therapeutic applications of ultrasound. In diagnosis, it is used to create an image of internal body structures such as tendons, muscles, joints, blood vessels, and internal organs, to measure some characteristics (e.g., distances and velocities) or to generate an informative audible sound.
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This is the most common situation, in which the extra digit is on the ulnar side of the hand, thus the side of the little finger. This can also be called postaxial polydactyly. It can manifest itself very subtly, for instance only as a nubbin on the ulnar side of the little finger, or very distinctly, as a fully developed finger.
Examples: The thumb is on the radial side of the hand (the same as saying the lateral side); the ulnar side of the wrist is the side toward the little finger (medial side). Ventral and dorsal, which describe structures derived from the front (ventral) and back (dorsal) of the embryo, before limb rotation.
Even left untreated and affecting function the general diagnosis of brachydactyly does not impact life expectancy. Prognosis may differ with different types or syndromes. ie. brachydactyly-mesomelia-intellectual disability-heart defects syndrome or if brachydactyly is not isolated and is a part of a larger genetic condition.
Thumb hypoplasia is a spectrum of congenital abnormalities of the thumb varying from small defects to complete absence of the thumb. [1] It can be isolated, when only the thumb is affected, and in 60% of the cases [ 2 ] it is associated with radial dysplasia [ 1 ] (or radial club, radius dysplasia, longitudinal radial deficiency).