Magnetic resonance imaging (MRI) can be used to determine the time of ischemic stroke onset, which would allow doctors to provide life-saving treatment, according to a new study published in the journal Radiology.

Acute ischemic stroke, in which a blood clot blocks the blood flow in the brain, can be treated with the drug plasminogen activator (tPA), which works by dissolving the clot to restore blood flow.

Plasminogen, however, should be administered within four and a half hours after the onset of the stroke, because the drug can cause bleeding in the brain if administered too late.

During the study researchers evaluated 130 ischemic stroke patients treated at Sainte-Anne Hospital in Paris between May 2006 and October 2008, where the time of stroke onset was well defined in all patients.

Researchers took an MRI of the patients within 12 hours of the onset of the stroke and analysed the MRI data. They were able predict the number of patients who had experienced stroke symptoms for longer than three hours with a greater than 90% accuracy.

Lead researcher Catherine Oppenheim said when the time of stroke onset is unknown MRI could help identify patients who are highly likely to be within the three-hour time frame when tPA is proven effective and approved for use.

“With the use of MRI, all stroke patients could be managed urgently, not just those patients with a known onset of symptoms,” Oppenheim said.