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a technique in which ultrasound waves are used to create two-dimensional images of internal organs
Ultrasound
Oscillations above the limit of human hearing, with a frequency of between 20 kHz and 10 GHz.
Uses 1. therapeutic use from vibration and absorption of the waves and conversion to warmth in the body, in diseases of the locomotor apparatus, particularly for rheumatic disease and the after-effects of injuries. 2. diagnostic use in the visualisation of body structures of different density. Cf. ultrasound diagnosis.
Ultrasound Diagnosis Diagnostic procedures which use ultrasound in impulse echo or constant frequency techniques.
1. Impulse echo technique (sonography) A quartz crystal is stimulated by high frequency electrical voltage to emit mechanical oscillations of constant frequency (emission function) or it emits oscillating voltages itself when it is irradiated with a reflected sound wave (detector function). The time between the emission of the impulse and the detection of the reflected sound waves (echoes) is proportional to the depth of the reflecting layer. The echo impulses are amplified and displayed on a screen. Principle use is the examination of the mobility of sections of the heart wall and heart valves during echocardiography.
2. Continuous frequency technique (Doppler technique) A crystal emits ultrasound waves of constant frequency. When the wave front meets a moving surface a fraction of the waves are reflected at altered frequency (Doppler effect). The interference between the frequencies of the incident and reflected beams can be converted into an audible low frequency and permits the calculation of the velocity and direction of the moving object, relative to the position of the ultrasound emitter. Examples of use include examination of foetal heart sounds in early pregnancy and in vascular surgery for the diagnosis of venous and arterial vascular disease such as constrictions (evaluation of the flow parameters).
3. Pulsed Doppler sonography (Pulsed Doppler technique) In contrast to the continuous frequency technique, sound waves are emitted in a pulsed packet of impulses and a piezocrystal functions simultaneously as emitter and receiver. After a set detection time only those signals are evaluated which correspond to a defined distance in the tissue. This makes it possible to classify the depth of the signal received.
urea
a nitrogenous waste product of protein metabolism
uremia
accumulation of toxic urinary waste products in the blood
uric acid
the end product of nucleic acid metabolism in the body
Urobilin
Break down product of bilirubin, which is excreted in the faeces or urine. It is formed from the precursor urobilinogen in the intestine or in urine which has stood for a long time. Urobilin can be detected by a rapid strip test or other test procedures in clinical chemistry. The excretion of urobilin is increased in liver diseases such as inflammation of the liver, cirrhosis, liver congestion, liver cancer and liver damage from toxins or infections. Cf. Probes of Liver Function.
uropathy
a disease of the urinary tract
urticaria
a condition in which red, itchy and swollen areas appear on the skin; also called hives
Uterus Carcinoma
Carcinoma of the womb, depending on the localisation, a distinction is made between cancer of the mucous membrane of the uterus (endometrial carcinoma) and cancer of the neck of the uterus (cervical carcinoma).
Glossary entries: Roche and Walter de Gruyter, Berlin
