[Development of helical CT and clinical application]

We applied helical CT to examinations of the clinical image diagnosis. Scanning was performed continuously while the couchtop of the CT scanner was shifted at a constant speed. The entire lung field could be scanned during a single holding of the breath when the couchtop speed was 20 mm/s. Tumors as small as 2 mm were detected. The diagnostic detectability and accuracy of helical CT were far superior to those conventional chest radiography. During abdominal examination, the target organ could be scanned at any specified phase (preferably arterial) during the injection of contrast medium. We detected very small hepatic tumors which could not be detected by conventional CT. Helical CT produced continuous data, which was reconstructed to display three-dimensional image. Helical CT could be used in mass screening for the detection of early lung cancer and in computer-aided diagnosis.