Serial MR Imaging of Intramuscular Hematoma: Experimental Study in a Rat Model with the Pathologic Correlation

Abstract

ObjectiveWe wanted to demonstrate the temporal changes of the magnetic resonance imaging (MRI) findings in experimentally-induced intramuscular hematomas in rats and to correlate these data with the concurrent pathologic observations.Materials and MethodsIntramuscular hematoma was induced in 30 rats. The MR images were obtained at 1, 4, 7 and 10 days and at 2, 3, 4, 6 and 8 weeks after muscle injury. The characteristic serial MRI findings were evaluated and the relative signal intensities were calculated. Pathologic specimens were obtained at each time point.ResultsOn the T1-weighted imaging (T1WI), the intramuscular hematomas exhibited isointensity compared to that of muscle or the development of a high signal intensity (SI) rim on day one after injury. The high SI persisted until eight weeks after injury. On the T2-weighted imaging (T2WI), the hematomas showed high SI or centrally low SI on day one after injury, and mainly high SI after four days. A dark signal rim was apparent after seven days, which was indicative of hemosiderin on the pathology. The gradient echo (GRE) imaging yielded dark signal intensities at all stages.ConclusionUnlike brain hematomas, experimentally-induced intramuscular hematomas show increased SI on both the T1WI and T2WI from the acute stage onward, and this is pathologically correlated with a rich blood supply and rapid healing response to injury in the muscle. On the T2WI and GRE imaging, high SI with a peripheral dark signal rim is apparent from seven days to the chronic stage.

A Potential Diagnostic Pitfall in the Differentiation of Hemorrhagic and Fatty Lesions Using Short Inversion Time Inversion Recovery: a Case Report

“…The selection of fat-suppression techniques depends on the purpose of the study, the amount of fat in the tissue, and the magnetic field strength. Frequency-selective fat saturation and STIR are most commonly used in clinical spine imaging (7,8).…”

Soft Tissue Masses

“…22.14 ). As early as 4 days after injury, a hypointense rim may be present at T2-W images, although no hemosiderin is present at histology; this may result from a boundary effect between two areas with different magnetic susceptibility [ 31 ]. The chronic hematoma often has a hypointense hemosiderin rim that may enhance.…”

“…When intramuscular hematomas were experimentally induced in rats, the low T2 signal ascribed to intracellular deoxyhemoglobin in the acute and subacute phases of brain hemorrhage never materialized, perhaps because blood fl ow in skeletal muscle allowed red blood cells to break down more rapidly than within the brain. However, at late stages hypointense hemosiderin did develop [ 31 ].…”

“…It is important to recognize that the absence of a blood-brain barrier in the soft tissues causes hemorrhage to behave differently there than in the brain. Blood products degrade more rapidly, and signal intensity progresses differently [ 31 ]. When intramuscular hematomas were experimentally induced in rats, the low T2 signal ascribed to intracellular deoxyhemoglobin in the acute and subacute phases of brain hemorrhage never materialized, perhaps because blood fl ow in skeletal muscle allowed red blood cells to break down more rapidly than within the brain.…”

The Pearls and Pitfalls of Magnetic Resonance Imaging of the Upper Extremity

“…Haemosiderin, the final ironcontaining product of hemoglobin degradation, contributes to the progressive low signal intensity that is commonly most conspicuous at the periphery of chronic hematomas on all pulse sequences, with characteristic susceptibility (blooming) artifact on gradient echo images (FIGURE 2). 17 GRE pulse sequences may help in some cases to detect areas of soft tissue mineralization because they are more sensitive to magnetic susceptibility artifacts than spin echo sequences. Unfortunately, soft tissue hemorrhage is usually not a single event in the musculoskeletal system, often with several episodes of hemorrhage over time, the appearance of which is complicated by muscle motion and limb movement.…”