Normal and accessory fissures of the lung: evaluation with contiguous volumetric thin-section multidetector CT

The purpose of this study was to use volumetric, 1.25 mm collimation MDCT read as softcopy and using a 2D and 3D viewer tool, to establish the frequency of normal and accessory fissures, the continuity of the fissures, whether the fissures are visible as a thin line, a hypovascular region, or both, and also to establish the interobserver agreement of readers. 150 consecutive MDCT examinations were retrospectively assessed. Interobserver agreement for each of these fissures was evaluated using the Kappa statistic. All subjects had a right and a left major fissure. 96.7% of subjects also had a right minor fissure. 40% had an accessory fissure, the most common, the left minor in 16% of subjects. Most of the three usual fissures were continuous, whereas fewer than half of accessory fissures were continuous. The majority (54-100%) of normal and accessory fissures were visualized as a thin line. There was substantial to excellent interobserver agreement on the presence or absence of fissures their continuity (k=0.96), and fair to excellent agreement on fissure morphology (k=0.37-1.0). The prevalence of fissures on MDCT, equivalent to autopsy studies, visualizing fissures as a thin line and high interobserver agreement is probably due to the high sensitivity of MDCT, secondary to thin-section volumetric imaging.