Imaging properties of a rotation-free, arrayed-source micro-computed tomography system

Abstract

We study the three-dimensional reconstructions and imaging properties of a proposed rotation-free micro-computed tomography (CT) system. The system uses linear arrays of the carbon nano-tube (CNT)-based X-ray sources which have ultra-short switch time and are individually addressable. With such sources, the micro-CT system is able to achieve ultrahigh temporal resolution, reduce dose and facilitate gated imaging. A square and a hexagonal geometry have been proposed for the system. In the square geometry, two linear source arrays and two area detectors form a square; whereas in the hexagonal geometry, three linear source arrays and three area detectors form a hexagon. The tomographic angular sampling for both of the geometries requires no motion of the sources or subject. Based on the sinogram maps, the hexagonal geometry has improved angular coverage than the square geometry. The ordered-subset convex iterative algorithm is implemented in both geometries for reconstructions from cone-beam projection data. Mean squared errors at the uniform regions in the reconstructed images are calculated to quantify the artifact level. Point spread functions are examined for point objects located at different axial and transverse positions throughout the FOV. Variance images are generated from 100 reconstructions with simulated Poisson noise and the mean variance are calculated for different regions of interest. The effect of gaps between the source arrays and the detectors is also studied. The reconstructed images from both geometries are generally consistent with the phantom, although some streaking artifacts due to the limited-angle nature of the geometries are observed. The gapfree hexagonal geometry produces lower mean squared error in the reconstructed images, lower FWHM of the point spread functions and lower variance. However, in more realistic situations where gaps appear between the source arrays and the detectors, the angular coverage of the hexagonal geometry degrades faster, resulting in an increase in artifacts, so that the square geometry becomes superior in this case.