Detection of pulmonary nodules with overlapping vs non-overlapping image reconstruction at spiral CT

The aim of this study was to analyze whether overlapping image reconstruction increases numbers of pulmonary nodules detected at helical CT. Forty-eight helical CT scans (21 with a slice thickness of 10 mm; 27 with a slice thickness of 5 mm) of patients with known pulmonary nodules were reconstructed both with overlapping and non-overlapping image reconstruction. Two readers recorded number and size of pulmonary nodules as well as diagnostic confidence. With overlapping image reconstruction each reader diagnosed more pulmonary nodules (slice thickness 10 mm: +24.0 and +26.7%, both p < 0.01; slice thickness 5 mm: +9.5 and +11.9%, both not significant) and more "definite" nodules (slice thickness 10 mm: +20.3%, p < 0.05, and +30.8%, p < 0.005; slice thickness 5 mm: +18.0 and +17.0%, both p < 0.05). Nodules diagnosed with overlapping image reconstruction only were almost exclusively smaller than the slice thickness. The increase in number of nodules detected was not associated with a decrease in diagnostic confidence. Overlapping image reconstruction improves detection of pulmonary nodules smaller than the slice thickness at spiral CT.