Related Experiment Video
Updated: Jun 5, 2026
Noninvasive In Vivo Small Animal MRI and MRS: Basic Experimental Procedures
Published on: October 20, 2009
Serial MR imaging of intramuscular hematoma: experimental study in a rat model with the pathologic correlation
Yeon Soo Lee1, Soon Tae Kwon, Jong Ok Kim
1Department of Radiology, Daejeon St. Mary's Hospital, The Catholic University of Korea, Daejeon 301-723, Korea.
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.
Materials And 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.
Conclusion:
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.
Insights
Magnetic resonance imaging (MRI) of rat intramuscular hematomas reveals distinct temporal changes. These findings correlate with pathology, showing increased signal intensity on T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI) throughout the healing process.
Area of Science:
- Biomedical imaging
- Musculoskeletal research
- Animal models in research
Background:
- Intramuscular hematomas require accurate imaging for diagnosis and monitoring.
- Understanding the temporal evolution of hematoma characteristics is crucial for clinical interpretation.
- Magnetic resonance imaging (MRI) offers detailed soft tissue contrast for evaluating hematomas.
Purpose of the Study:
- To characterize the serial magnetic resonance imaging (MRI) findings in experimentally induced intramuscular hematomas in rats.
- To correlate these MRI observations with concurrent pathological findings over time.
- To elucidate the temporal dynamics of intramuscular hematoma healing using advanced imaging techniques.
Main Methods:
- Intramuscular hematomas were surgically induced in 30 rats.
- Serial MRI scans (T1WI, T2WI, GRE) were performed at multiple time points from day 1 to 8 weeks post-injury.
- Relative signal intensities were quantified, and pathological specimens were collected and analyzed at each time point.
Main Results:
- T1WI showed an initial isointense or high signal intensity rim, persisting for 8 weeks.
- T2WI demonstrated high signal intensity from day 4 onwards, with a dark rim appearing after 7 days, indicative of hemosiderin.
- Gradient echo (GRE) imaging consistently showed low signal intensity throughout all stages.
Conclusions:
- Experimentally-induced intramuscular hematomas exhibit increased signal intensity on both T1WI and T2WI from the acute phase.
- These MRI findings are pathologically correlated with a robust blood supply and rapid muscle healing response.
- T2WI and GRE imaging reveal a high signal with a peripheral dark rim from 7 days to the chronic stage.
