title: Serial MR imaging of intramuscular hematoma: experimental study in a rat model with the pathologic correlation.
abstract: OBJECTIVE
  We 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.
  
  
  METHODS
  Intramuscular 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.
  
  
  RESULTS
  On 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.
  
  
  CONCLUSIONS
  Unlike 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.
authors.affiliation: Department of Radiology, Daejeon St. Mary's Hospital, The Catholic University of Korea, Daejeon 301-723, Korea.
authors.forename: Yeon Soo
authors.initials: YS
authors.lastname: Lee
authors.forename: Soon Tae
authors.initials: ST
authors.lastname: Kwon
authors.forename: Jong Ok
authors.initials: JO
authors.lastname: Kim
authors.forename: Eun Seok
authors.initials: ES
authors.lastname: Choi
mesh_terms: D000818:Animals; D006406:Hematoma / Q000175:diagnosis* / Q000473:pathology; D006614:Hindlimb; D008279:Magnetic Resonance Imaging; D018482:Muscle, Skeletal / Q000473:pathology*; D009135:Muscular Diseases / Q000175:diagnosis* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors