Six-minute MRI may rival CT for evaluating ischemic stroke

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Move over CT, MR imaging has just gotten faster. A technique developed by researchers at the University of Arizona in Tucson and the University of California, Los Angeles may help to establish MRIs as the go-to modality for evaluating acute ischemic stroke.

CT has become the imaging technology of choice for assessing stroke patients, due to its speed and accuracy. MRIs have better quality images on average and offer no radiation risk to the patient. However, MRIs have heretofore been a slower technology and therefore less attractive when minutes count.

Published online June 10 in Stroke, the study led by Kambiz Nael, MD of the Department of Medical Imaging at University of Arizona, explored the use of an approximately six-minute MRI protocol. This was done through the use of faster imaging tools and parallel acquisition techniques. 

“Rapid acquisition time in EPI [echo-planar imaging] is made possible by rapid gradient switching that permits the acquisition of all frequency and phase encoding steps during a single pulse cycle,” they wrote. Parallel imaging allowed for enhancement of speed through slice-encoding direction or undersampling in phase and reduction of distortion and artifacts normally found in longer sequences like EPI.

Researchers ran 84 MRIs, 62 initial patient scans and 22 repeated scans and assessed the resulting images for signs of stroke. With diagnostic image quality in 90 to 100 percent of subscans, clinicians were able to identify that 95 percent of the patients reviewed had acute infarction. Observers were able to detect acute intracranial hemorrhages on EPI-gradient recalled echo in 13 patients. Repeated scans occurred due to follow-up intravenous tissue-type plasminogen activator, endovascular recanalization and decline in mental status.

Nael et al attributed part of the new protocol’s success to improvements seen in the past decade in MRI hardware as well as to the parallel imaging technique. “[M]ulticoil technology for better signal reception and higher magnetic fields (≥3T) with higher afforded signal-to-noise ratio, have increased the efficiency to apply fast imaging tools,” they stated.

Nael et al added, “Because the described technology is commercially available, fast and effective MRI protocols are on the horizons for the next decade with comparable acquisition time and proficiency with other cross-sectional techniques, such as CT.” This would provide clinicians with safer, faster and clearer technology for assessing acute ischemic stroke patients.

They suggested the protocol could be used in research settings and recommended more studies to assess its usefulness as a diagnostic and evaluative tool in clinical practice.