2D ultrasound imaging is a widely used technique in medical imaging that provides two-dimensional visual representations of internal structures. A handheld device known as a probe or transducer contains piezoelectric crystals that emit and receive ultrasound waves which penetrate tissues and bounce back as echoes. The echoes are detected and converted into electrical signals. These signals are processed and displayed on a monitor, creating a real-time 2D grayscale image, with different shades of gray representing various tissue densities. The brighter areas on the image correspond to structures that reflect more ultrasound waves, while darker areas represent structures that reflect fewer waves or are attenuated by intervening tissues. The 2D-mode (or B-mode) provides cross-sectional views of the scanned area, showing a single plane or slice of the scanned area at a time.

Key Features and Uses of 2D Ultrasound:

Comparison with 3D and 4D Ultrasound:
See also Ultrasound Technology, Sonographer, Ultrasound Elastography, Obstetric and Gynecologic Ultrasound.

In 3D ultrasound (US) several 2D images are acquired by moving the probe across the body surface or rotating inserted probes. 3D-mode uses the same basic concept of a 2D ultrasound but rather than take the image from a single angle, the sonographer takes a volume image. The volume image that is displayed on the screen is a software rendering of all of the detected soft-tissue combined by specialized computer software to form three-dimensional images.
The 3D volume rendering technique (VR) does not rely on segmentation (segmentation techniques are difficult to apply to ultrasound pictures) and makes it possible to obtain clear 3D ultrasound images for clinical diagnosis. A 3D ultrasound produces a still image. Diagnostic US systems with 3D display functions and linear array probes are mainly used for obstetric and abdominal applications. The combination of contrast agents, harmonic imaging and power Doppler greatly improves 3D US reconstructions.

3D imaging shows a better look at the organ being examined and is used for:

Fusion 3D imaging methods for generating compound images from two sets of ultrasound images (B-mode and Doppler images) enable the observation of the structural relationships between lesions and their associated blood vessels in three dimensions (maximum intensity projection).

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Echoes of deep lying structures within the body do not always come from the latest emitted sound pulse and can produce an aliasing artifact. Aliasing lowers the frequency components when the pulse repetition frequency is less than 2 times the highest frequency of a Doppler signal. This artifact can be problematical at Spectral or Color Doppler examinations.
Aliasing of the data displayed in pulsed wave technology is utilized as a benefit in determining transitions from laminar to turbulent flow.

See also Ultrasound Imaging Modes.

(A or amp) The SI base unit of electric current.
Definition: Two parallel conductors, infinitely long and having negligible cross section should be placed 1 meter apart in a perfect vacuum. One ampere is the current that creates between them a force of 0.2 microNewton per meter of length.
One ampere represents a current flow of 1 coulomb of charge per second.
One ampere of current results from a potential distribution of 1 volt per ohm of resistance, or from a power production rate of 1 watt per volt of potential.
The unit is known informally as the amp, but A is its official symbol and is named for the French physicist André-Marie Ampère.

See also System International.