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Muscle echo is normal
Last reviewed: 04.07.2025
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Individual muscle fibers are covered with endomysium, which is penetrated by a rich network of capillaries and nerve fibers. These muscle fibers are grouped into muscle bundles, surrounded by perimysium, which consists of connective and fatty tissue, blood vessels and nerves. Muscle fibers are enclosed in a dense connective tissue sheath called epimysium. The internal structure of muscle tissue depends on the function of the muscle. If the muscle fibers are located along the long axis of the muscle, then such muscles are designed for easy movements over a long distance. If the muscle fibers (unipennate, bipennate and circumpennate) are located at an angle to the long axis, then these muscles are designed for lifting weights over a short distance.
Each muscle has a belly and two tendons. There may be more than one belly, such as the rectus abdominis.
There may be several initial attachments for muscles that are connected into one belly, for example, for the biceps and triceps brachii, and for the quadriceps femoris. Attachment of the muscle to the bone occurs through tendons and fibro-osseous joints.
The feathery structure of muscles is best seen with longitudinal scanning. Muscles appear as homogeneous hypoechoic bundles separated by multiple parallel hyperechoic connective tissue layers (perimysium) like a "feather". These layers gradually pass into the tendinous part of the muscle.
When scanning transversely, the muscles appear as hypoechoic structures with small-point inclusions of the “starry sky” type.
The tissue harmonic mode more clearly works out the fibrous layers in muscle tissue and makes the ultrasound image of muscle tissue more colorful.
Panoramic scanning mode provides visualization of the entire length of the muscle, its transition to the tendon and the place of attachment to the bone.
Muscle tissue always has lower echogenicity than subcutaneous fat or tendons. When contracting, the thickness of the muscle increases, the course of the fibers changes slightly and the echogenicity of the muscle decreases.
On MRI scans, intact muscle tissue has an average signal intensity across all standard pulse sequences.
On T1-weighted images, the structure of muscle tissue is heterogeneous due to layers of adipose tissue, whereas on T2-weighted images, muscle tissue has a homogeneous structure of medium intensity, without hyperintense layers of adipose tissue.
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