Thick-section reformatting of thinly collimated helical CT for reduction of skull base-related artifacts

OBJECTIVE. Our purpose was to evaluate thick-section reformatted helical CT of the brain base as a technique for reducing skull base-related artifacts and to compare it with conventional CT. MATERIALS AND METHODS. Twenty-three patients with suspected intracranial ab normalities related to the brain base, as determined either by clinical exa mination or at the time of imaging, were evaluated with contrast-enhanced c onventional CT of the brain (5-mm collimation, 140 kVp, 170 mA, 2-sec rotat ion time) and reformatted helical CT (l-mm collimation, 1.5 pitch, 120 kVp, 220 mA). Helical sections were reformatted to a thickness of 5 mm by a vol ume-averaging algorithm using a computer workstation. Three observers retro spectively and blindly reviewed the images and qualitatively scored artifac ts at the foramen magnum, middle cranial fossa, anterior cranial fossa, int erpetrous region, and internal occipital protuberance. Image graininess and observer confidence were also scored. Paired statistical analyses using sc ore differences in each patient were possible. RESULTS. Reformatted helical CT reduced skull base-related artifacts across all five anatomic regions (p < 0.05). The foramen magnum showed the greate st reduction in artifacts and the anterior cranial fossa the least. Image g raininess was increased on reformatted CT compared with conventional CT (p < 0.05), but observer confidence remained higher for reformatted CT (p < 0. 05). Total additional scan time was 3.15 +/- 0.38 min with 5.3 +/- 1.2 min required for reformatting. CONCLUSION. Reformatted CT significantly decreases skull base-related artif acts in the brain, improving observer confidence in evaluation of the brain base and adding an average of only 8.45 +/- 1.6 min of scanning and proces sing time to each examination.