In the endovascular arm of the IMS III trial , the following time intervals were calculated : stroke onset to emergency department arrival ; emergency department to computed tomography ( CT ) ; CT to intravenous tissue plasminogen activator start ; intravenous tissue plasminogen activator start to randomization ; randomization to groin puncture ; groin puncture to thrombus identification ; thrombus identification to start of endovascular therapy ; and start of endovascular therapy to reperfusion .