When pain and other symptoms arise from issues with your musculoskeletal system (bones, muscles, cartilage, tendons, ligaments, and joints) your doctor might order an imaging test to find the problem.
Technology allows for multiple ways to look inside the body; X-rays, CT scans, MRI, and ultrasounds. Depending on the issue and the source of pain, doctors will determine which method to use.
When is an ultrasound used versus an MRI?
MRI utilizes high-powered magnets to create 3-D images and is a high-contrast resolution modality that can detect changes in tissue. For example, an MRI of a muscle injury will show signs of water in the muscle, a sign of injury.
Ultrasound uses high-frequency sound waves to see inside the body and is a high-spatial resolution modality that provides more detailed internal images. An ultrasound of the same muscle injury will show individual fibers of the muscle and injury changes. Both MRI and ultrasound will detect large muscle injuries and tears. Ultrasound is best used for discovering and diagnosing muscle micro-tears and chronic conditions.
The musculoskeletal system contains many structures in a single area- nerves, muscles, tendons, joints, ligaments, bones, and connective tissue called fascia. Any of these can get injured or have abnormalities. Ultrasound can pinpoint the injured area and determine if the injury is connected to another structure. Musculoskeletal ultrasounds will show what happens to the affected area during movement, which is not possible with MRI or other imaging scans.
Unlike an MRI, ultrasound can be used for guiding injections such as corticosteroid shots.
When is an MRI used?
Ultrasounds have limitations. When a larger, more complicated injury is suspected your doctor will order an MRI. Ultrasounds do not show structures inside joints, only soft tissue. To check for damage to cartilage and bone, an MRI is needed. MRI is also recommended for conditions that effect deep or large areas of the body. For example, if a doctor needs to view a hand or a knee, an MRI is used.
MRI gives more detail than ultrasound and X-rays and is especially useful for imaging tendons, muscles, ligaments, and soft tissue injury.