The benefit of IV alteplase is time dependent, with earlier treatment within the therapeutic window leading to bigger A brain imaging study to exclude ICH is recommended as part of the initial evaluation of patients who are potentially eligible for these therapies. With respect to endovascular treatment, a pooled analysis of 5 randomized trials comparing EVT with medical therapy alone in which the majority of the patients were treated within 6 hours found that the odds of improved disability outcomes at 90 days (as measured by the mRS score distribution) declined with longer time from symptom onset to arterial puncture.42 treatment windows trials, which used advanced imaging to identify a relatively uniform patient group, showed limited variability of treatment effect with time in these highly selected patients.51,52 The absence of detailed screening logs in these trials limits estimations of the true impact of time in this population. To ensure that the highest proportion of eligible patients presenting in the 6- to 24-hour window have access to mechanical thrombectomy, evaluation and treatment should be as rapid as possible. Reducing the time interval from ED presentation to initial brain imaging can help to reduce the time to treatment initiation. Studies have shown that median or mean door-to-imaging times of 20 minutes can be achieved in a variety of different hospital settings.79 81 See Tables XVI and XVII in online Data Supplement 1. Noncontrast CT (NCCT) is effective to exclude ICH before IV alteplase administration. I A Recommendation revised from 2013 AIS Guidelines. Magnetic resonance (MR) imaging (MRI) is effective to exclude ICH before IV alteplase administration. I B-NR Recommendation revised from 2013 AIS Guidelines. CTA with CTP or MR angiography (MRA) with diffusion-weighted magnetic resonance imaging (DW-MRI) with or without MR perfusion is recommended for certain patients. I A New recommendation. 