[Clinical usefulness of helical scanning CT (HES-CT) for orbital lesion]

Helical scanning CT (HES-CT) was applied to multiplanar reconstruction (MPR) and 3-D imaging for the diagnosis of 65 patients with orbital lesions. We employed the the Toshiba TCT-900S, a fourth-generation high-speed CT scanner equipped with a slip-ring system. In HES-CT, scanning was performed with continuous rotation of the X-ray tube for 30 s, while the couch top was simultaneously moved at a constant speed of 1 to 2 mm/s. Images were reconstructed from continuous raw data to obtain a slice pitch of 1 mm in the longitudinal direction. HES-CT was found to have some advantages over conventional thin slice CT: 1) a wide area could be scanned in a short time (30 s) without motion artifact, 2) small lesions could be easily detected because slice images could be generated with a fine pitch at arbitrary positions from continuous raw data, 3) MPR images had good continuity in the longitudinal direction, and 4) high contrast of structures was obtained in the orbital region. HES-CT was considered to be useful for the detection of orbital lesions.