Purpose: Diffusion-weighted imaging (3 directions) and diffusion tensor imaging (9 directions) were compared for their sensitivity to detect ischemic lesion.
Materials and methods: 41 patients (18 supposed transient ischemic attacks, 23 arterial stroke, MRI<or=48h) presenting with stroke syndrome were imaged using two diffusion sequences (3 directions, 2 excitations, acquisition time: 40 seconds and 9 directions, 1 excitation, acquisition time: 50 seconds, other parameters being identical). The following variables were compared (Wilcoxon test): number and extent of lesions, MRI signal and absolute ADC values, relative signal intensity and ADC ratio. Fractional anisotropy was measured within the principal lesion on the 9 directions sequence.
Results: 24 patients presented a lesion on both sequences. Four of them (including one TIA) had more lesions (<5 mm) on the 9 directions sequence than on the 3 directions sequence. Both sequences were normal for the 17 remaining patients (TIA=4, differential diagnosis=7, indeterminate=6). No significant difference was found for the other study parameters between 3 vs 9 directions sequences. There was a 10% decrease of the mean fractional anisotropy in ischemic lesion.
Conclusion: By showing more lesions than standard diffusion-weighted imaging and providing quantitative anisotropy measurements, diffusion tensor imaging could replace the standard 3 directions diffusion-weighted sequence.