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Diffusion-weighted imaging for the evaluation of diffuse axonal injury in closed head injury
Thierry A G M Huisman1, A Gregory Sorensen, Klaus Hergan
1Department of Radiology, Neuroradiology Section, and MGH-NMR Center, Massachusetts General Hospital, Harvard Medical School, Charlestown-Boston, USA. thierry@nmr.mgh.harvard.edu
Purpose:
The purpose of this work was to compare diffusion-weighted imaging (DWI) with conventional MRI in the detection of shearing injuries in acute closed head injuries.
Method:
Twenty-five patients (19 male, 6 female) were examined within 48 h of trauma. Conventional MRI included T2-weighted fast spin echo, fluid-attenuated inversion recovery (FLAIR), and T2*-weighted gradient echo sequences. Full tensor DWI with calculation of apparent diffusion coefficient (ADC) maps was also performed. Lesions were identified and compared on all sequences.
Results:
Four hundred twenty-seven lesions were counted by the combined use of all sequences. DWI identified 70 lesions not seen on conventional MRI. DWI identified 310 shearing injuries, followed by T2/FLAIR (n = 248) and T2* (n = 202). The majority of DWI-positive lesions showed decreased diffusion (65%).
Conclusion:
DWI is valuable in closed head injury because it identifies additional shearing injuries not visible on T2/FLAIR or T2* sequences. Furthermore, DWI/ADC maps differentiate between lesions with decreased or increased diffusion. DWI is less sensitive than T2* imaging for detecting hemorrhagic lesions.