MR imaging outperforms CT for initial stroke evaluation

April 1, 2007

A multicenter prospective trial involving 1210 patients in Europe has found that the odds of a favorable clinical outcome were one-third higher for acute stroke patients who received diffusion/perfusion MRI to determine the appropriateness of tPA thrombolysis than for patients assessed with conventional noncontrast CT.

A multicenter prospective trial involving 1210 patients in Europe has found that the odds of a favorable clinical outcome were one-third higher for acute stroke patients who received diffusion/perfusion MRI to determine the appropriateness of tPA thrombolysis than for patients assessed with conventional noncontrast CT.

Results drawn from the Safe Implementation of Thrombolysis in Stroke trial were presented on 7 February at the 2007 International Stroke Conference in San Francisco.

Based on the findings, Prof. Peter D. Schellinger, a professor of neurology at the University of Erlangen in Germany, preferred MRI over conventional CT to recommend appropriate stroke treatment, especially beyond the three-hour time window for intra-arterial tPA administration. MRI also proved superior during the first three hours after symptom onset, a period where CT has long played an essential role for initial stroke evaluation.

"The conflict that we still have here is what is better: CT or MRI? I think the winner is MRI, and we have evidence for that," Schellinger said.

The study revolved around the use of noncontrast CT performed on 714 patients within three hours of onset of stroke symptoms, diffusion/perfusion MR imaging performed on 322 patients within three hours of symptom onset, and perfusion/perfusion MRI performed on 174 patients from three to six hours after symptom onset. The patients were treated at one of five stroke treatment centers in Barcelona and Heidelberg, Hamburg, Cologne, and Frankfurt, Germany. Interpreting physicians were blinded to results.

Multivariant analysis covering the patients' ages, treatment timing, and clinical outcomes based on mortality and intracranial hemorrhage rates found that MRI raised the probability for a favorable outcome by nearly 35% compared with CT. Univariant analysis found no statistically significant differences for the two imaging modalities, however.

MRI's impact on outcomes was greatest for patients who received intra-arterial tPA thrombolysis three to six hours after symptom onset. The odds for a favorable outcome were 46.7% higher than for patients who did not receive a DWI/PWI MR evaluation. MRI's use resulted in a 48% reduction in the probability of symptomatic intracranial hemorrhage. It was not responsible for any loss of time compared with CT for patients who qualified for treatment within the three-hour time limit, and MRI's superiority over CT was seen among patients treated within this window, Schellinger said. For these patients, 38.8% examined with MRI experienced positive outcomes compared with 35.6% of patients evaluated with CT.

"The positive impact of MRI seems to be accentuated beyond the three-hour time window. And within the window, I would say that it is at the discretion of the treating physician if they want to use CT or MR, but evidence for the diagnostic superiority of MRI is there," Schellinger said.

According to a study published in the March 13 issue of Neurology, men are more likely than women to benefit from the use of tissue plasminogen activator within three hours after stroke.

The study involved 333 people who were treated with tPA. It found that men were more than three times as likely as women to achieve functional independence at three months after tPA treatment, despite the fact that fewer men than women survived three months after treatment.