A liver sonography is a diagnostic tool to image the liver and adjoining upper abdominal organs such as the gallbladder, spleen, and pancreas. Deeper structures such as liver and pancreas are imaged at a lower frequency 1-6 MHz with lower axial and lateral resolution but greater penetration. The diagnostic capabilities in this area can be limited by gas in the bowel scattering the sound waves.
The application of microbubbles may be useful for detection of liver lesions and for lesion characterization. Some microbubbles have a liver-specific post vascular phase where they appear to be taken up by the reticuloendothelial system (RES). Dynamic contrast enhanced scans in a similar way as with CT or MRI can be used to studying the arterial, venous and tissue phase.
After a bolus injection, early vascular enhancement is seen at around 30sec in arterialized lesions (e.g., hepatocellular carcinomas (HCC), focal nodular hyperplasia (FNH)). Later enhancement is typical of hemangiomas with gradually filling towards the center. In the late phase at around 90sec, HCCs appear as defects against the liver background. Most metastases are relatively hypovascular and so do not show much enhancement and are seen as signal voids in the different phases.
Either with an intermittent imaging technique or by continuous scanning in a nondestructive, low power mode, characteristic time patterns can be used to differentiate lesions.

See also Medical Imaging, B-Mode, High Intensity Focused Ultrasound, Ultrasound Safety and Contrast Medium.

A matrix is a set of numbers arranged in a rectangular array. The array of numbers is divided in rows and columns. The matrix size determines the scan resolution.

The matrix size is the number of data points collected in one, two or three directions. Normally used for the 2D in plane sampling. The display matrix may be different from the acquisition matrix, although the latter determines the resolution.

Ultrasound is an ideal tool to examine the joints and surrounding soft tissues like tendons, ligaments and joint linings. Musculoskeletal and joint sonography is sensitive, without radiation exposure, easy accessible, quick, and has high patient tolerability with relatively low cost.
A real-time scanner allow the dynamic assessment of the musculoskeletal system and a specific examination for each patient. In addition, joint aspiration and injection accuracy can be improved. Probes with high frequency improve the image resolution and allow visualization of fine anatomic structures of the small parts. As musculoskeletal ultrasound (MSUS) is very operator dependent, experience and training is required. Ultrasound is also often used in the treatment of musculoskeletal disorders.

See also Ultrasound Therapy, Real-Time Mode, Artifact and Ultrasound Biomicroscopy.

A narrow or tuned Bandwidth describes a small frequency spectrum of pulses. With the Fourier transformation method a pulse or amplifier can be subscribed with its bandwidth. It is usually expressed with a 6dB drop of maximum amplitude, subscribing the bandwidth between the edges of the curve.
The selection of bandwidth is essential for achieving certain test results; narrow bandwidth for highly sensitive scans or broad banded for high resolution scans. The fast Fourier transformation uses beside the echo amplitude evaluation method the capability of the echo frequency / bandwidth information.