title: Time to stroke magnetic resonance imaging.
abstract: BACKGROUND
  Recent guidelines on stroke neuroimaging from the American Academy of Neurology (AAN) recommend magnetic resonance imaging (MRI) over computed tomography (CT) for stroke diagnosis when patients present within 12 hours of onset. We sought to estimate the proportion of stroke MRI that is performed within 12 hours.
  
  
  METHODS
  Using the best available data, we estimated total time from symptom onset to MRI with a Monte Carlo simulation. We modeled 3 times to MRI: time to presentation, time to emergency department (ED) MRI, and time to inpatient MRI. Total time to MRI was estimated by summing these time components while varying model parameters around our base model. Sensitivity analyses assessed the relative importance of model parameters to overall MRI timing.
  
  
  RESULTS
  In 2009, we estimate that 66% of stroke patients underwent MRI, 14% received an MRI in the ED, and 68% of all MRIs were obtained on hospital day 0 or 1. We estimate that 29% (95% confidence interval 24-33%) of stroke MRIs are obtained within 12 hours of onset. Sensitivity analyses revealed that even large clinical changes (eg, decreasing time to presentation) would only moderately influence this proportion. For example, if mean time to presentation were reduced to 30 minutes (from the base case estimate of 16 hours), the proportion of stroke MRI performed within 12 hours would only increase to 55.3%.
  
  
  CONCLUSIONS
  Stroke guidelines favor the use of MRI over CT only during the first 12 hours from symptom onset, yet less than one-third of stroke MRIs are actually performed within this timeframe.
authors.affiliation: Department of Veterans Affairs, Veterans Affairs Center for Clinical Management and Research, Ann Arbor Veterans Affairs Healthcare System, Ann Arbor, Michigan 48109, USA. jamesbur@med.umich.edu
authors.forename: James F
authors.initials: JF
authors.lastname: Burke
authors.forename: Jeremy B
authors.initials: JB
authors.lastname: Sussman
authors.forename: Lewis B
authors.initials: LB
authors.lastname: Morgenstern
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Kerber
mesh_terms: D003198:Computer Simulation; D019983:Guideline Adherence; D006297:Health Services Accessibility / Q000592:standards*; D006760:Hospitalization; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000592:standards; D009010:Monte Carlo Method; D017410:Practice Guidelines as Topic; D010818:Practice Patterns, Physicians' / Q000592:standards*; D011237:Predictive Value of Tests; D011379:Prognosis; D012042:Registries; D020521:Stroke / Q000175:diagnosis* / Q000473:pathology / Q000628:therapy; D013997:Time Factors; D061665:Time-to-Treatment