Musculoskeletal ultrasound is an injury assessment technique that uses high-frequency sound waves to create images of painful or injured muscles, tendons, ligaments, joints and soft tissues throughout the body. The images are transferred to a computer for an accurate assessment, helping to guide the treatment and rehabilitation process.
For ultrasound examination, patients sit or lie face-up on an examination table that can be tilted or moved. A clear water-based gel is applied to the affected area to be assessed. The gel ensures the contact of the transducer with the body and prevents the blockage of the sound waves from passing into the body. The ultrasound technologist presses the transducer firmly against the skin, sweeping over the area of interest or angling the sound beam at different locations to get the best result.
After the completion of the examination, patients are asked to dress and wait while ultrasound images are reviewed. This examination usually takes 15-30 minutes but may sometimes take longer time.
Patients going for ultrasound examination should wear comfortable, loose-fitting clothes and may need to remove all clothing and jewelry in the area to be examined. As ultrasound examination is very sensitive to motion, it is important for the patient to sit still during the exam.
Most ultrasound examinations are painless, fast and usually with no discomfort. Once the examination is complete, the gel is wiped off from the skin and patients can resume their normal activities immediately.
Ultrasound imaging follows the same principles involved in sonar used by bats, fishermen and weather services, where a sound wave strikes an object and then bounces back or echoes. By measuring these echo waves, one can determine the distance from the object, its size, shape and consistency. Similarly in ultrasound examination, a transducer sends the high-frequency sound waves into the body and receives/records the echoing waves. The sound waves bounce off the internal organs, fluids and tissues and are traced by the sensitive microphone in the transducer which records the tiny changes in the sound’s pitch and direction.
These signature waves are immediately measured and displayed by a computer, which successively creates a real-time image on the monitor. One or more frames of the moving pictures are generally captured as still images. Small loops of the moving real time images can also be saved.
Ultrasound imaging is used to detect changes in appearance of organs, tissues and vessels or certain abnormal masses such as tumors. Ultrasound scanning is noninvasive, widely available, easy-to-use with no harmful effects and is inexpensive. It does not use any ionizing radiation and provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies and needle aspiration. The results of ultrasound are not affected by the presence of cardiac pacemakers, ferromagnetic implants or fragments within the body making ultrasound an excellent alternative to MRI for claustrophobic patients. Structures such as tendons and cartilage can be better seen by ultrasound as compared to MRI.
Ultrasound has difficulty penetrating bone, therefore only outer surfaces can be seen. In order to visualize internal structures of bones, other techniques such as MRI may be employed.