Chapter 6: Ultrasound Imaging

Ultrasound Imaging

Ultrasound is a cross-sectional imaging method based on sound waves reflected off soft tissues and tissue interfaces. Ultrasound predates computed tomography (CT) and magnetic resonance imaging (MRI) for soft tissue imaging. It is increasingly employed in imaging of the musculoskeletal system.

History

Diagnostic ultrasound has its origins in sonar (sound navigation and ranging), a technique developed as a navigation tool for submarines and for the detection of objects under water. Ultrasound was employed in an unsuccessful attempt to locate the wreck of the Titanic in 1912 and was widely used in the submarine warfare of World War I (1914–1918).¹

Medical use of diagnostic ultrasound started in the 1940s, and in the early 1950s the ability to detect lumps in breast tissue was demonstrated. Although ultrasound was the first technique available for accurate diagnosis of soft tissue lesions, it was not until the 1980s that ultrasound gained widespread acceptance for the evaluation of the musculoskeletal system.

Ultrasound in Rehabilitation

Physical therapists have a long history with ultrasound as a form of biofeedback. Such application of ultrasound, sometimes referred to as real-time ultrasound imaging or rehabilitative ultrasound imaging (RUSI), is growing. But diagnostic musculoskeletal ultrasound imaging (DMUS) is also increasingly employed in rehabilitation for diagnosing musculoskeletal disorders.²

Rehabilitative Ultrasound Imaging

According to a consensus statement by an international symposium on rehabilitative ultrasound, “RUSI is a procedure used by physical therapists to evaluate muscle and related soft tissue morphology and function during exercise and physical tasks. RUSI is used to assist in the application of therapeutic interventions aimed at improving neuromuscular function.”³

Physical therapists have been at the forefront of rehabilitative ultrasound imaging (RUSI) for more than two decades, and ultrasound is routinely used in physical therapy clinics to examine the activity of the stabilizing musculature of the lumbar spine, as well as other muscles. Numerous studies have employed ultrasound to obtain real-time information about the role of the multifidus and transversus abdominis (TrA) muscles in stabilization of the lumbar spine.⁴ Findings related to normal and abnormal function of the transversus abdominis have been used to devise exercise regimens for stabilization employing low-level co-contractions of transversus abdominis and multifidus. These regimens have been successfully used to guide treatment of nonspecific low back pain and disk herniations.⁵ Furthermore, ultrasound has been employed to measure segmental lumbar spine motion and to guide rehabilitation of the shoulder.^6,7

Diagnostic Musculoskeletal Ultrasound Imaging

In contrast to the voluminous research in rehabilitative ultrasound, physical therapists rarely publish research on diagnostic musculoskeletal ultrasound (DMUS).⁸ This is surprising because physical therapists seem to have the prerequisite knowledge to become competent ultrasonographers of the musculoskeletal system. They have solid knowledge of musculoskeletal ...