Seaman Family Magnetic Resonance Research Centre, and the Calgary Stroke Program, Department of Clinical Neurosciences, University of Calgary, Foothills Medical Centre, 1403-29 St NW, Calgary, AB, Canada

Correspondence to:
Correspondence to:
Dr P A Barber
Experimental Imaging Centre, University of Calgary, 3330 Hospital Drive NW, Calgary T2N 4N1, Canada; pabarber{at}ucalgary.ca

Background and objectives: Controversy exists about the optimal imaging technique in acute stroke. It was hypothesised that CT is comparable with DWI, when both are read systematically using quantitative scoring.

Methods: Ischaemic stroke patients who had CT within six hours and DWI within seven hours of onset were included. Five readers used a quantitative scoring system (ASPECTS) to read the baseline (b) and follow up CT and DWI. Use of MRI in acute stroke was also assessed in patients treated with tissue plasminogen activator (tPA) by prospectively recording reasons for exclusion. Patients were followed clinically at three months.

Results: bDWI and bCT were available for 100 consecutive patients (admission median NIHSS = 9). The mean bDWI and bCT ASPECTS were positively related (p<0.001). The level of interrater agreement ranged from good to excellent across all modalities and time periods. Bland–Altman plots showed more variability between bCT and bDWI than at 24 hours. The difference between bCT and bDWI was 2 ASPECTS points. Of bCT scans with ASPECTS 8–10, 81% had DWI ASPECTS 8–10. Patients with bCT ASPECTS of 8–10 were 1.9 times more likely to have a favourable outcome at 90 days than those with a score of 0–7 (95% CI 1.1 to 3.1, p = 0.002). The relative likelihood of favourable outcome with a bDWI ASPECTS 8–10 was 1.4 (95% CI 1.0 to 1.9, p = 0.10). Of patients receiving tPA 45% had contraindications to urgent MRI.

Conclusion: The differences between CT and DWI in visualising early infarction are small when using ASPECTS. CT is faster and more accessible than MRI, and therefore is the better neuroimaging modality for the treatment of acute stroke.

Abbreviations: ASPECTS, Alberta Stroke Programme Early Computed Tomography Score; CT, computed tomography; DWI, diffusion-weighted imaging; EIC, early ischaemic changes; FLAIR, fluid attenuated inversion recovery; MRA, magnetic resonance angiography; MRI, magnetic resonance imaging; mRS, modified Rankin scale; NIHSS, National Institutes of Health Stroke Scale; tPA, tissue plasminogen activator

Keywords: computed tomography; diffusion weighted imaging; ischaemic stroke; thrombolysis

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