Ellipsoid scan: Chest cone-beam CT with a large ellipsoidal view field using a 16-inch X-ray image intensifier

We propose a cone-beam computed tomography (CT) system that has a large field of view and high image quality, and that can be applied to the chest imaging. This system uses a 16-inch X-ray image intensifier and a television camera. To enlarge the field of view, an ellipsoid-scan sequence is used, which requires the subject to be moved parallel to the transaxial plane during scanning. The contrast resolution is increased by applying a television camera with high sensitivity and nonlinear efficiency. We tested this system using a stationary apparatus, and obtained an isotropic three-dimensional image of a chest phantom which had 0.64-mm voxels and covered both lungs. This system attained better spatial resolution for coronal images and its contrast resolution in the transaxial images was only 3 to 7 times larger than conventional spiral-scan CT at the same X-ray dose. This system is promising for lung cancer screening, precise diagnosis and surgery.