Musculoskeletal ultrasound

Musculoskeletal ultrasound is a musculoskeletal imaging technique that adds a different and complementary dimension of imaging evaluation to the traditional modalities of plain radiography, computerized tomography (CT), and magnetic resonance imaging (MRI).

Recognized advantages of the modality include the ready availability of ultrasound equipment, the relatively low cost of the procedure compared with advanced imaging such as CT and MRI, and that the exam uses non-ionizing radiation.

Other advantages of the modality include an ability to image patients with a contraindication to MRI (e.g., patients with some types of pacemakers) and that ultrasound experiences much less artifact when imaging patients with surgical hardware.

Musculoskeletal ultrasound also allows dynamic evaluation of patients, which can improve the radiologic interpretation of the clinical relevance of findings seen in a static image (e.g. shoulder impingement).

Standard high-frequency ultrasound probes also resolve finer imaging detail than many types of clinical musculoskeletal MRI. The axial resolution of a 10 MHz probe is 150 μm. A 1.5 T MRI scanner with a field of view of 12 x 6 cm and a matrix of 256 x 256 pixels, with a slice thickness of 0.5 cm has a resolution of 469 x 469 μm.

Despite its many strengths, however, musculoskeletal ultrasound also has some limitations in the complete evaluation of musculoskeletal disorders. Radiography and CT provide much better evaluation of mineralization and the spatial relationship of fractures. MRI is invaluable for assessment of bone marrow, bone tumors, and joints and muscles that aren't accessible to high resolution ultrasound probes (e.g. the spine, the sacroiliac joints, the cruciate ligaments). Musculoskeletal ultrasound also encounters its own set of artifacts, such as anisotropy, and requires a solid knowledge base and background in ultrasound technique for safe and accurate results.