Foreign body and injection granulomas also frequently calcify. Besides calcification of a hematoma, other traumatic causes include sequelae of previous surgery, irradiation, and thermal injuries. They are associated with traumatic, ischemic, neuropathic, infectious, and neoplastic conditions. Such conditions include renal osteodystrophy (less commonly, primary hyperparathyroidism), hypoparathyroidism, hypervitaminosis D, milk–alkali syndrome (prolonged excessive intake of milk and alkali for heartburn in peptic ulcer disease, often associated with renal insufficiency), sarcoidosis, and processes associated with massive bone destruction (e.g., metastases, multiple myeloma, and leukemia).ĭystrophic calcifications represent calcium deposits in damaged tissue without metabolic derangement. Metabolic (metastatic) calcifications are associated with a disturbance in calcium/phosphorous metabolism, resulting in the deposition of calcium in normal tissues ( Fig. They can be classified as metabolic (metastatic), dystrophic, or idiopathic. Soft tissue calcifications can easily be appreciated by CT. Differentiation of actual invasion of neighboring structures such as the neurovascular bundle and bone from simple distortion and pressure defects by the adjacent mass is not always feasible. Overestimation of a soft tissue mass with CT is possible because of adjacent soft tissue edema. Hibernoma (brown fat tumor, typically involving the shoulder region, chest wall, or thigh)Įlastofibroma (between the inferior margin of the scapula and chest wall) Lipoblastoma (lipoma in infancy and early childhood) Macrodystrophia lipomatosa (neural fibrolipoma with macrodactyly) Neural fibrolipoma (fibrolipomatous hamartoma usually of the median nerve in the wrist) Lipoma arborescens (diffuse synovial lipoma in the knee) Lipoma (subcutaneous, intermuscular, intramuscular, and synovial) Table 11.1 Fat-containing soft tissue lesions The poorly defined border on the posteroinferior border (arrowheads) indicates that the cyst is ruptured. A fluid-containing lesion (arrows) hypodense to the surrounding muscles is seen. A fatty lesion (arrows) between the scalp and skull is seen. Complete fatty replacement of all muscles in the thigh is seen. Fat-containing lesions are summarized in Table 11.1 and cystic lesions in Table 11.2. A fluid-containing lesion appears hypodense to muscle and has a density similar to water or slightly above it (range 0–20 HU). The density of fat ranges from − 50 to − 100 HU. Besides lipomas and cysts, other lesions may contain adipose tissue or fluid, respectively. 11.3), CT rarely allows a specific histologic diagnosis based on attenuation values and appearance. With the exception of a few lesions, such as lipomas ( Fig. Certain limitations of CT in the evaluation of soft tissue masses, however, must be recognized. It allows definition of the exact dimensions of a lesion and its relationship to nearby neurovascular structures and bone. CT is of little use in the differentiation of these conditions, but it may play an important role in the localization, distribution, and assessment of the extent of muscular involvement.ĬT is useful in the evaluation of soft tissue masses. It is observed with muscular dystrophies, neuropathies, ischemias, and metabolic and systemic myopathies, as well as idiopathically ( Fig. Fatty replacement of muscle may be complete and homogeneous or incomplete and inhomogeneous, but it is not characteristic for a specific disease. In many muscle diseases, the muscle fibers become necrotic and degenerate or are replaced by fat and connective tissue. Normal muscles are of soft tissue density and are separated from each other by fatty septa. Compared with MRI, CT is more sensitive for the diagnosis of both tiny soft tissue calcifications and air collections and facilitates differentiation between the two.įor CT, the contrast characteristics of soft tissue disease depend on the relative proportions of fat, water, and mineral. Magnetic resonance imaging (MRI) is far superior to computed tomography (CT) for the visualization of soft tissue pathology because of greater soft tissue contrast and an overall improved tissue characterization based on signal behavior on different pulse sequences and relaxation parameters. 11 Soft Tissue Disease Burgener\, Francis A.
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