Search results
Results from the WOW.Com Content Network
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.
Optoacoustic imaging, using the photothermal effect, for the accuracy of spectroscopy with the depth resolution of ultrasound; Photoacoustic Imaging, a technique to detect vascular disease and cancer using non-ionizing laser pulses; Ultrasound imaging, using very high frequency sound to visualize muscles and internal organs
Ultrasound image showing the liver, gallbladder and common bile duct. Medical ultrasound uses high frequency broadband sound waves in the megahertz range that are reflected by tissue to varying degrees to produce (up to 3D) images. This is commonly associated with imaging the fetus in pregnant women. Uses of ultrasound are much broader, however.
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.
Photoacoustic imaging or optoacoustic imaging is a biomedical imaging modality based on the photoacoustic effect.Non-ionizing laser pulses are delivered into biological tissues and part of the energy will be absorbed and converted into heat, leading to transient thermoelastic expansion and thus wideband (i.e. MHz) ultrasonic emission.
Functional ultrasound imaging (fUS) is a medical ultrasound imaging technique for detecting or measuring changes in neural activities or metabolism, such as brain activity loci, typically through measuring hemodynamic (blood flow) changes.
In genetics, coverage is one of several measures of the depth or completeness of DNA sequencing, and is more specifically expressed in any of the following terms: Sequence coverage (or depth) is the number of unique reads that include a given nucleotide in the reconstructed sequence.
The ratio of the imaging depth to the aperture size is known as the F-number. Dynamic aperture is keeping this number constant by growing the aperture with the imaging depth until the physical aperture cannot be increased. A modern medical ultrasound machine has a typical F-number of 0.5.