Abstract WP36: Detection of Early Ischemic Changes in non-contrast Head CT improved by utilization of Standardized “Acute Stroke” Windowing of Images

Abstract

INTRODUCTION: Non-contrast head CT (NCCT) is the standard radiologic test performed in the emergency department (ED) for patients presenting with symptoms of acute stroke. Early ischemic changes (EIC) in NCCT are often missed by ED physicians and on-call radiologists. We assessed the hypothesis that detection of EIC can be improved by a standardized method of image evaluation. METHODS: Retrospective chart review was performed of the University of Tennessee Health Science Center prospective database of acute ischemic stroke from January - July 2012. Patients treated with IV TPA who had NCCT as the initial neuroimaging exam were identified and additional baseline characteristics were noted. EIC was defined as findings consistent with: 1) Hyperdense MCA/basilar artery sign 2) Sulcal effacement 3) Basal ganglia/subcortical hypodensity and 4) Loss of cortical gray-white differentiation. Initial NCCT was reviewed by a blinded neurology resident (except presenting complaints). First, images were reviewed with standard window settings of center and width level of 40 and 100 Hounsfield units (HU). Then, all images were interpreted with ”stroke windows” of center 35 and width of 30 HU. This was compared with the radiologists’ final report. Final interpretations based on "stroke windows" were compared with follow up imaging studies to assess accuracy. Fisher’s exact test was used for statistical analysis. RESULTS: NCCTs of 50 patients (42% females) with an average age 75.4 years and mean NIHSS of 13.4 were reviewed. The mean time to CT from symptom onset was 97.7 minutes. Out of 50 patients, radiologists detected EIC in 9 patients while authors detected EIC in 35 patients (18% vs. 70% with 100% accuracy; p < 0.0001). Hyperdense MCA sign although most commonly reported by radiologists, was better appreciated with "stroke windows" (14% and 56%; p <0.0198). Similarly, detection of the remaining EIC also improved with "stroke windows" (6% and 46%, P<0.0001) CONCLUSIONS: EIC although common in acute ischemic stroke are often missed by the interpreting radiologists. We conclude that the rates of detection can be significantly improved with standardized “Stroke Windows”. This has important implications in regards to rapid diagnosis and treatment of acute ischemic stroke.