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.

According to Shannon's sampling theorem, the sampling frequency should be twice the frequency being sampled. The nyquist frequency is the maximum frequency that can be sampled without aliasing. In ultrasound imaging, it is defined as half of the pulse repetition frequency.
NF = PRF/2 (nyquist frequency = pulse repetition frequency/2)
This is the so-called Nyquist limit. If the velocity of flow exceeds the Nyquist limit, the direction and velocity are inaccurately displayed and appear to change direction. Color flow Doppler capitalizes on this effect. This allows detecting flow disturbances from laminar to turbulent flow.

See also Aliasing Artifact, Repetition Rate, and Sampling Rate.

From Verathon Inc.;
'The Pediatric BladderScan® is the newest addition to Verathon Inc.'s trusted family of BladderScan® instruments. By enabling health care providers to measure a child's bladder volume noninvasively, this easy-to-use, handheld tool aids in the diagnosis and treatment of urinary conditions.'

See also Urologic Ultrasound, Pediatric Ultrasound, Mirror Artifact, Pelvic Ultrasound, Reflux Sonography and Ultrasonography.

In power mode the amplitude (power) of color Doppler signals is displayed, regardless of the velocity. Power does not have negative values and is independent of sampling frequency. An aliasing artifact does not occur in power mode images. Caused by plotting the quantity enhanced by echo contrast agents in a power map, power mode is often used in contrast Doppler ultrasound examinations.
Also known as energy mode.

Reflection of the sound beam occurs when it hits a boundary between materials having different acoustic impedance. The reflection (echo) is the portion of a sound that is returned from the boundary. The reflection time (the time taken for the wave to return to the probe) can be used to determine the depth of the object.
The reflection within the body produces the ultrasound image, but should be minimized at an ultrasound couplant to skin boundary where the couplant acts as an acoustic window through which the image is seen. The amount of sound waves, which are reflected back at the interface between two tissues is depend on the angle of incidence and the difference between the acoustic impedance values of the two tissues.
If the difference is great, a large part of the sound waves will be reflected back. If too much sound is reflected back and not enough waves are remaining to be able to penetrate the tissue, the imaging will be poor.
If the difference is small, a small amount will be reflected back. Enough sound signal remains to continue with ultrasound imaging.
If the ultrasound beam meets a rough surface or small object, the beam is scattered in all directions and only a small amount will be received by the probe.

See also False Distance Artifact, Target Strength, and Snells Law.