What is the difference between musculoskeletal ultrasound and MRI?

Musculoskeletal ultrasound and magnetic resonance imaging (MRI) are two types of imaging examinations, each with its own characteristics. Differences between the two examinations:

1. Different principles: Musculoskeletal ultrasound uses high-frequency sound wave echo signals to construct images, offering high resolution for soft tissue structures. It is particularly effective for real-time dynamic observation of superficial tissues such as muscles, tendons, and ligaments. MRI, on the other hand, is based on the magnetic moment changes of hydrogen nuclei in a strong magnetic field. It generates detailed images of internal body structures by exciting the nuclei with radiofrequency pulses and capturing the released energy signals. MRI provides high soft tissue contrast and can clearly display structures such as bones, muscles, blood vessels, and nerves.

2. Different examination methods: Musculoskeletal ultrasound uses high-frequency sound waves for imaging, forming images by transmitting sound waves into the body via an ultrasound transducer and receiving the reflected echo signals. MRI, however, induces resonance of hydrogen atoms in the body using a strong magnetic field, with subsequent signal detection and image generation by computer processing.

3. Imaging principles and image clarity: Musculoskeletal ultrasound relies on differences in tissue density to generate contrast, resulting in limited image clarity, although it has advantages in situations requiring real-time imaging. MRI enhances contrast between tissues by utilizing different physical properties, such as relaxation times, resulting in clearer images, making it suitable for examinations requiring detailed structural information.

4. Different application ranges: Due to its portability, absence of radiation exposure, lower cost, and real-time capability, musculoskeletal ultrasound is commonly used for rapid screening and diagnosis of sports injuries, joint diseases, and peripheral nerve disorders. MRI is more suitable for complex or deep musculoskeletal system diseases, such as spinal cord lesions, bone tumors, and arthritis. Its three-dimensional imaging capability helps comprehensively evaluate the extent and nature of lesions.