A laboratory CT scanner for dynamic imaging

Abstract

A high-resolution laboratory CT scanner has been developed for imaging objects undergoing periodic motion. The scanner comprises an x-ray image intensifier, optically coupled to a linear photodiode array. Gated time-evolved projections of a single slice of the moving object are acquired, reformatted, and reconstructed. The resulting series of CT images shows the object at different phases of its motion cycle. The scanner has an adjustable field of view (FOV) and the resolution can be as high as 3.2 mm-1 (for the 40-mm FOV). The spatial resolution depends on the inherent resolution of the scanner and on the object's velocity. For objects moving at 1 cm s-1, the spatial resolution is reduced by 9% in the direction of motion. The signal intensity in the reconstructed image is linear for materials with attenuation coefficients as high as 1.5 cm-1 (for a 90-kVp x-ray beam), with an average accuracy of +/- 0.02 cm-1. The average accuracy of circumference measurements made from the CT images is +/- 0.3 mm. Lastly, an application of this dynamic CT scanner to imaging excised human arterial specimens under simulated physiological pressure conditions is presented as an example.