Image intensifier-based computed tomography volume scanner for angiography

A prototype volume computed tomography (CT) system for use in angiography was designed, constructed, and tested. The system consisted of a fixed X-ray tube, a conventional image intensifier (II) coupled to a charge-coupled device camera, and a computer-controlled turntable on which phantoms were placed. We wanted to predict, through phantom studies, the imaging performance of an II-based volume CT for direct three-dimensional (3D) reconstruction of vascular structures.

To explore the imaging performance of the system for reconstructing a vascular structure, two sets of projection images of a vascular phantom, acquired over 250 projection angles with two different-sized IIs, were digitized and used for a direct 3D conebeam reconstruction. The signal-to-noise ratio (SNR) of each reconstructed image was measured. From these measurements, image quality was accessed as a function of the number of reconstructions averaged and the different orientations. The spatial resolution limits of the system were measured from the 3D reconstructed images of a specially designed resolution phantom for different orientations and locations.

The measured SNRs of all direct 3D reconstruction images were reasonably good, and back-ground noise levels measured from 3D reconstruction images were almost 30 Hounsfield units. The measured spatial resolution of the system was 0.5 line pairs per millimeter. However, spatial resolution was reduced around the edge of the II to nearly half that measured in the central area of the field of view.

An II-based volume CT scanner can produce direct 3D reconstructions of vascular structures with good image quality for intraarterial angiography.