Volumetric Imaging and Reconstruction with Stationary Head CT System using Carbon Nanotube X-ray Source Arrays

Purpose: The purpose of this study was to evaluate a novel stationary head CT system (sHCT) enabled by the carbon nanotube (CNT) field emission x-ray source array for volumetric head imaging. A data processing and image reconstruction package was developed and demonstrated for the system. Methods: The experimental sHCT system consisted of three CNT x-ray source arrays placed in parallel imaging planes separately. During imaging, the sources stayed stationary while only the bed advancing through a tunnel formed by the parallel planes. In each imaging cycle, 135 projections were acquired over 232 degrees of view. A CT ACR 464 phantom and a Kyoto head phantom were imaged to evaluate the system performance. Image uniformity, signal to noise ratio, spatial resolution, CT number and detectability were investigated for the proposed system. All images were processed and reconstructed with an iterative reconstruction-based package. Total-variation (TV) regularization methods such as the adaptive steepest descent projection onto convex set (ASDPOCS) algorithm were implemented to reduce noises and artifacts caused by the reduced projection views. Results: Volumetric data with good uniformity, high spatial resolution, and detectability for both high- and low-resolution features were demonstrated for the proposed sHCT scanner. Two scan protocols, step-and-shoot and continuous mode were compared and proved to provide similar image quality while the latter increased the total scan speed. The SIRT-ASDPOCS algorithm effectively suppressed the sparse-view and limited-view artifact and enhance the contrast noise ratio. Conclusion: We demonstrated the feasibility of sHCT for volumetric head imaging using multiple CNT x-ray source arrays. The device provides 3D images with high fidelity. The prototype sHCT system is being installed at the UNC hospital for a patient imaging study.