Development of a subject-standing-type cone-beam computed tomography for chest and orthopedic imaging

A subject-standing-type cone-beam computed tomography (CT) with high spatial resolution has been developed as a new three-dimensional imaging modality for subjects standing or sitting naturally on a turntable. A 16-in. X-ray image intensifier and charge coupled device camera acquires a 12-bit 5122-pixel projection at 60 f/s and the rotation period is 4.8 or 9.6 s for 288 or 576 projections, respectively. To reduce image noise, the system controls the X-ray pulse duration and iris-opening area through real-time analysis of the projection image. To improve CT accuracy and eliminate artifacts, the veiling glare of the image intensifier and scattered X-rays are corrected. Human chest and orthopedic studies with about 50 patients were conducted. Three-dimensional images with a spherical field of view with a diameter of 21-25 cm, 0.4- to 0.5-mm voxels and a 512(3) matrix were obtained. In coronal, sagittal and volume rendering images, the surface of arthrosis was visualized smoothly with a resolution higher than that of conventional CT. In the case of gonarthrosis, narrowing of the clearance at the surface of arthrosis was visualized clearly under body-weight burdening, which would be difficult if the subject was lying down.