A study of 40,777 stroke patients found 42 percent underwent brain imaging within the recommended 25 minutes of hospital arrival, researchers say. Lead author Dr. Adam Kelly, a neurologist at the University of Rochester Medical Center, said brain imaging is an essential tool in the diagnosis of a stroke and determines which treatment to pursue. Strokes caused by a blockage in one of the arteries that serve the brain -- ischemic strokes -- are candidates for the clot-busting drug tissue plasminogen activator, which can restore blood flow and improve clinical outcomes. However, this drug cannot be used when the symptoms are instead caused by a ruptured blood vessel in the brain. \"It is therefore essential that physicians are able to \'see\' what is occurring in the brain, and quickly,\" Kelly said in a statement. \"We were struck by the fact that less than half of patients with acute stroke symptoms did not receive a brain scan within recommended guidelines.\" The study published in the journal Stroke found individuals were less likely to receive timely brain scans if: -- The patient did not arrive at the hospital by ambulance. -- The patients were not white. -- The patients had certain risk factors for stroke such as diabetes, a prior history of stroke, were age 75 and older and peripheral vascular disease.