Appropriate interslice gap for screening coronal paranasal sinus tomography for mucosal thickening.

The objective of this study was to establish the appropriate interslice gap for screening coronal paranasal sinus tomography to identify sinus mucosal thickening. We reviewed 100 coronal paranasal sinus tomographic scans (interslice gap, 2 mm) that had been performed at our institution between January 2004 and November 2004 to evaluate rhinosinusitis. Digital photographs of all slices from each tomographic scan were taken. The intervening slices were eliminated to form six different sets of interslice gaps of 4, 6, 8, 10, 16, and 20 mm. The remaining slices for each set were moved to corresponding folders created on a computer to catalog each interslice gap. The same specialist evaluated each folder of interslice gap. The paranasal sinuses, the ethmoid infundibulum, and the frontal recess were evaluated for mucosal thickening. The sensitivity, specificity, and accuracy of each interslice gap in detecting mucosal thickening were calculated by accepting the results of 2-mm-thick slices as the gold standard. The interslice gap of 2 mm was compared with that of other interslice gaps using the chi-square test for dependent groups (the McNemar test). The value of 20 mm interslice gap in detecting sinus mucosal thickening was found to be significantly low when compared with the interslice gap of 2 mm (P = 0.022). Using coronal paranasal sinus tomography, an interslice gap up to 16 mm may be used to detect sinus mucosal thickening.