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Absence of the portal system in a first trimester case associated with hygroma and aorto-umbilical fistula. (A): Transverse plane of the upper abdomen with color Doppler applied, showing umbilical cord insertion, stomach, the prominent hepatic artery and no afferent liver venous perfusion; (B): midsagittal plane reconstructed from a three-dimensional volume acquisition were the crown-rump ...
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.
Spectral doppler through pulmonary vein. Spectral doppler is presented similarly to M-mode in which the doppler information is plotted as a spectrogram. This can be both "continuous" and "pulse" wave where the former shows the spectrum along a specific line and the latter shows within a small window along that line.
Doppler ultrasonography showing absence of flow and hyperechogenic content in deep vein thrombosis of the subsartorial vein. Coronal plane, seen from medial side of lower leg, showing thrombosis of the fibular veins , with hyperechoic content and only marginal blood flow.
The sign is an imaging finding using a 3.5–7.5 MHz ultrasound probe in the fourth and fifth intercostal spaces in the anterior clavicular line using the M-Mode of the machine. This finding is seen in the M-mode tracing as pleura and lung being indistinguishable as linear hyperechogenic lines and is fairly reliable for diagnosis of a pneumothorax.
An endoscopic ultrasound probe placed in the esophagus can also be used to visualize lymph nodes in the chest surrounding the airways (bronchi), which is important for the staging of lung cancer. Ultrasound can also be performed with an endoscopic probe inside the bronchi themselves, a technique known as endobronchial ultrasound.
Comparatively, transthoracic ultrasound must first traverse skin, fat, ribs and lungs before reflecting off the heart and back to the probe before an image can be created. All these structures, along with the increased distance the beam must travel, weaken the ultrasound signal thus degrading the image and Doppler quality. [citation needed]
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.