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Diffusion and perfusion magnetic resonance imaging following closed head injury in rats
Y Assaf1, A Holokovsky, E Berman
1School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv, Israel.
Abstract:
Diffusion-, perfusion-, T1-, and T2-weighted magnetic resonance imaging (MRI) were performed at 1-2 h, 24 h, and 1 week following closed head injury (CHI) in rats, and data was compared with hematoxylin and eosin histology. At 1-2 h, large areas of low perfusion in the damaged hemisphere overestimate the histological damage. In the first 2 h, the histological damage seems to be a superposition of abnormalities in the T1- and diffusion-weighted images. In areas with more than 10% reduction in the apparent diffusion coefficients (ADCs), reduced regional cerebral blood volume (r-CBV) was also observed. The decrease in ADCs and rCBV correlated with r = 0.78. Changes in the MRI parameters revealed the following: (a) Further reduction in ADC occurred from 83+/-15% at 1-2 h after trauma to 69+/-9% at 24 h, and 1 week later a marked elevation in the ADC values is observed. (b) Blood perfusion measurements performed 1-2 h posttrauma revealed a pronounced reduction in r-CBV (53+/-18%) in the damaged hemisphere in all rats. At 24 h postimpact, areas of hyper- and hypoperfusion were observed. One week later, similar perfusion was found in both hemispheres of all rats. (c) T2 hyperintensity at 24 h overestimated the histological damage found at 1 week. At one week following the trauma, the T2 hyperintensity underestimated the histological damage. It is concluded that CHI, which is a heterogeneous insult, should be studied by a combination of MRI techniques. The superposition of the abnormalities seen on T1 and on the diffusion-weighted MR images at early time point represents best the histological damage. Both T2 and rCBV images are less informative in terms of actual histological damage.
Insights
Magnetic resonance imaging (MRI) techniques, including diffusion and T1-weighted, best represent early histological damage after closed head injury (CHI) in rats. Other MRI methods like T2 and perfusion imaging were less informative for assessing injury severity.
Area of Science:
- Neuroscience
- Radiology
- Trauma Research
Background:
- Closed head injury (CHI) is a complex insult requiring accurate assessment methods.
- Magnetic resonance imaging (MRI) offers various sequences to evaluate brain injury.
- Histological analysis provides a gold standard for tissue damage but is invasive and retrospective.
Purpose of the Study:
- To compare the effectiveness of different MRI sequences (diffusion, perfusion, T1, T2) in characterizing histological damage following CHI in rats.
- To determine the optimal MRI approach for assessing early and evolving brain injury after trauma.
Main Methods:
- Performed diffusion-, perfusion-, T1-, and T2-weighted MRI at 1-2 hours, 24 hours, and 1 week post-CHI in rats.
- Correlated MRI findings with hematoxylin and eosin (H&E) histology.
- Analyzed changes in apparent diffusion coefficients (ADCs) and regional cerebral blood volume (r-CBV).
Main Results:
- Early (1-2 h) T1- and diffusion-weighted MRI abnormalities, particularly reduced apparent diffusion coefficients (ADCs), best correlated with histological damage.
- Perfusion imaging (r-CBV) showed initial hypoperfusion that normalized by 1 week; T2 hyperintensity varied in its correlation with damage over time.
- A strong correlation (r=0.78) was observed between decreased ADCs and reduced r-CBV in the early injury phase.
Conclusions:
- A combination of MRI techniques is essential for comprehensively evaluating the heterogeneous nature of CHI.
- Early diffusion-weighted and T1-weighted MRI sequences are most informative for reflecting histological damage immediately after trauma.
- T2-weighted imaging and perfusion measurements (r-CBV) were found to be less reliable indicators of actual histological damage in this model.