Quotient of the particle velocity normal to a wall to the sound pressure acting on the wall.
See filter, high-pass.
Quotient of the sound pressure acting on a wall to the particle velocity normal to the wall.
A strong, low-frequency clutter signal tending to obscure the Doppler frequency spectrum of interest, often arising from motion of the walls of a blood vessel.
An electronic signal filter in a Doppler system that rejects echo information from low-velocity reflectors such as stationary or slow-moving tissue. This filtering is needed to keep high-amplitude tissue echoes from saturating the Doppler receiver, masking very low-amplitude echoes from flowing blood.
See wall thump.
Initial enhancement of a vascularized lesion, a vessel lumen, or a cardiac chamber, usually used in visualization of flow with contrast agents. A lesion (or vessel or chamber) becomes rapidly or slowly enhanced.
Related terms: wash-out, wash-in–wash-out curve
De-enhancement of a vascularized lesion, a vessel lumen, or a cardiac chamber. A formerly enhanced lesion (or vessel or chamber) becomes rapidly or slowly less enhanced than previously, usually used in visualization of flow with contrast agents. The time of wash-out indicates whether a lesion becomes hypoenhanced, which is a feature of malignancy. Conversely, sustained enhancement is commonly encountered in benign lesions.
Related terms: wash-in, wash-in–wash-out curve
Graphic plotting intensity of a microbubble signal over time from contrast medium injection. Also called a time- intensity curve.
Related terms: wash-in, wash-out curve
A situation in which part or all of a technique is performed under water.
The unit of power; 1 W = 1 joule per second (J/s).
A unit of intensity; 1 W/cm2 = 104 W/m2.
See acoustic wave.
The graphic representation of an acoustical or electrical parameter as a function of time.
An imaginary surface passing through all particles that are in the same phase of vibration within a propagating sound wave.
See acoustic wavelength.
See acoustic wavelength.
A tiny wave.
2π times the number of oscillations per unit length. Wavenumber (k) = 2π/λ, where λ is the wavelength. The unit is radian per meter or reciprocal meter (m–1).
See acoustic wavelength.
As the velocity pulse of blood flow travels along the arterial tree, reflections, consisting of pressure waves traveling in a proximal direction (toward the heart), occur at discontinuities of fluid impedance, mainly at branch points.
Related term: reflection
As the velocity pulse of blood flow travels along the arterial tree, reflections, consisting of waves traveling in a proximal direction, occur at discontinuities of fluid impedance, mainly at branch points.
With respect to the cardiovascular system, the velocity of propagation of a pressure pulse along the arterial tree. This velocity varies from about 5 m/s in the aorta to about 5 cm/s in small vessels.
Related term: velocity of sound
Noise whose power spectral density is essentially independent of frequency.
A member of the set of positive integers and 0, ie, the numbers 0, 1, 2, 3, ..., etc. There is no fractional or decimal part. Whole numbers are also known as the counting numbers.
An adjective referring to the ability of a device to pass a very wide range of frequencies in a signal. Wideband also refers to a signal that contains frequency components distributed over a wide range.
Related term: Compare with narrow bandwidth and broadband
A transducer technique used in linear arrays to expand the lateral field of view. Using electronic timing delays as in phased array imaging, the ultrasound beam is steered to view beyond the lateral edges of the transducer.
See scanning window.
A relatively signal-free area between the arterial Doppler shift signal and the baseline during the systolic portion of a Doppler spectral display. The window tends to be obliterated by turbulent flow.
Container filled with medium having a known sound speed in which thin wires are fixed at regular distances. Used for calibration of the time base (distance calibration) and estimation of axial and lateral resolution.
See acoustic working frequency.
Process of enlarging a region of interest by optimizing the scanning parameters and rescanning the region. Instruments that have this feature allow the operator to first select the region to be enlarged by applying cursors to the original image. Only echo data arising from within the zoomed region are written to the memory, and all pixels in the memory are used to represent this region. Thus the image should not lose the detail that it might when using read zoom.
Related term: read zoom