Abstract
Diffusion tensor imaging may aid brain ischemia assessment but is more time consuming than conventional diffusion-weighted imaging (DWI). We compared 3-gradient direction DWI (3DWI) and 20-gradient direction DWI (20DWI) standard vendor protocols in a hospital-based prospective cohort of patients with transient ischemic attack (TIA) for lesion detection, lesion brightness, predictability of persisting infarction, and final infarct size. We performed 3T-magnetic resonance imaging including diffusion and T2-fluid attenuated inversion recovery (FLAIR) within 72 h and 8 weeks after ictus. Qualitative lesion brightness was assessed by visual inspection. We measured lesion area and brightness with manual regions of interest and compared with homologous normal tissue. 117 patients with clinical TIA showed 78 DWI lesions. 2 lesions showed only on 3DWI. No lesions were uniquely 20DWI positive. 3DWI was visually brightest for 34 lesions. 12 lesions were brightest on 20DWI. The median 3DWI lesion area was larger for lesions equally bright, or brightest on 20DWI [median (IQR) 39 (18-95) versus 18 (10-34) mm2, P = 0.007]. 3DWI showed highest measured relative lesion signal intensity [median (IQR) 0.77 (0.48-1.17) versus 0.58 (0.34-0.81), P = 0.0006]. 3DWI relative lesion signal intensity was not correlated to absolute signal intensity, but 20DWI performed less well for low-contrast lesions. 3DWI lesion size was an independent predictor of persistent infarction. 3-gradient direction apparent diffusion coefficient areas were closest to 8-week FLAIR infarct size. 3DWI detected more lesions and had higher relative lesion SI than 20DWI. 20DWI appeared blurred and did not add information. http://www.clinicaltrials.gov. Unique Identifier NCT01531946.
Highlights
The risk of recurrent stroke after transient ischemic attack (TIA) is considerable [1], and clinical scores, as the ABCD2, have been validated and implemented in the guidelines [2]
No lesions were uniquely 20-gradient direction diffusion-weighted imaging (DWI) (20DWI) positive. 3-gradient direction DWI (3DWI) was visually brightest for 34 lesions. 12 lesions were brightest on 20DWI
The median 3DWI lesion area was larger for lesions bright, or brightest on 20DWI [median (IQR) 39 [18–95] versus 18 [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34] mm2, P = 0.007]. 3DWI showed highest measured relative lesion signal intensity [median (IQR) 0.77 (0.48–1.17) versus 0.58 (0.34–0.81), P = 0.0006]. 3DWI relative lesion signal intensity was not correlated to absolute signal intensity, but 20DWI performed less well for low-contrast lesions. 3DWI lesion size was an independent predictor of persistent infarction. 3-gradient direction apparent diffusion coefficient areas were closest to 8-week fluid attenuated inversion recovery (FLAIR) infarct size
Summary
The risk of recurrent stroke after transient ischemic attack (TIA) is considerable [1], and clinical scores, as the ABCD2, have been validated and implemented in the guidelines [2]. DWI lesions are heterogeneous, possibly as sign of varying degree of tissue damage, location, and recovery after reperfusion [18,19,20]. This influences the subsequent extent of infarction on follow-up examinations [21]. The more time-consuming DTI has been reported to be of value in assessing the presence and degree of brain ischemia in acute stroke and TIA [26,27,28,29] and aids the identification of small and low-contrast lesions, even beyond the capability of standard 3DWI [30]. We hypothesized that higher numbers of diffusion encoding gradients could add to qualitative lesion identification and delineation in a clinical setting
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