Interobserver variability in angiographic measurement and morphologic characterization of intracranial aneurysms: a report from the International Study of Unruptured Intracranial Aneurysms.

PURPOSE To determine the variability in assessment of the principal inherent characteristics of intracranial aneurysms through the evaluation of interobserver variability for material with uniform quality. METHODS Blinded interpretations of a single set of cerebral arteriograms of 55 aneurysms were evaluated by several statistical approaches. RESULTS Excellent correlations were found for the detection and measurement of aneurysms after adjusting for geometric distortion caused by magnification. Progressively decreasing correspondence was found for factors that characterized morphology, including, in order, determination of margins, assessment of accessory appendages, and identification of a neck. DISCUSSION Correction for geometric distortion was the most critical factor that influenced uniform measurement of size. Standards for measurement and morphologic characteristics were subsequently established for use in the International Study of Unruptured Intracranial Aneurysms.