[Utility of thin-section/high-pitch helical CT for the assessment of small lung nodules]

To determine the utility of thin-section/high-pitch CT for the assessment of small lung nodules, a lung phantom was scanned on 1 mm width collimation at variable pitches of 1.0, 1.5, 2.0, 2.5 and 3.0. Images obtained at pitch 3.0 were degraded visually. Secondly a bead phantom was scanned on 1 mm width collimation at pitches of 1.0, 1.5, 2.0 and 3.0. Focus size was determined with a variable setting of small and large. We obtained maximum and full width at half maximum (FWHM) scans and performed a clinical study of small lung nodules on 1 mm width at pitch 2.0 on small focus. Thirdly, we estimated the image quality of 1 mm/2 mm helical scans in comparison with 1 mm/1 mm helical scans. Comparison was made using axial, MPR and 3D-CT (MIP) images. The axial and MIP images were almost equal qualitatively, whereas MPR images were degraded, especially in the near region of the heart and great vessels, due to motion artifacts. We emphasize the utility of 1 mm/2 mm helical CT in scanning a much larger volume with the same breath holding.