Statistical detection of nonvisible isodense subdural fluid collections.

An analytic method for detecting isodense subdural fluid collections from computed tomography (CT) scan pixel attenuation data is presented. Analysis of 44 CT scan levels from 8 patients with isodense subdural hematomas (ISDH) and 50 CT scan levels from 15 patients without ISDH indicates 6% false positive and 3% false negative errors if the analysis is restricted to noncontrast CT scans that demonstrate subcalvarial bilateral cortical attenuation symmetry in the pictorial display.