An inverse-geometry volumetric CT system with a large-area scanned source: A feasibility study

Department of Radiology, Stanford University, Stanford, California 94305, USA.
Medical Physics (Impact Factor: 3.01). 10/2004; 31(9):2623-7. DOI: 10.1118/1.1851913
Source: PubMed

ABSTRACT We propose an inverse-geometry volumetric CT system for acquiring a 15-cm volume in one rotation with negligible cone-beam artifacts. The system uses a large-area scanned source and a smaller detector array. This note describes two feasibility investigations. The first examines data sufficiency in the transverse planes. The second predicts the signal-to-noise ratio (SNR) compared to a conventional scanner. Results showed sufficient sampling of the full volume in less than 0.5 s and, when compared to a conventional scanner operating at 24 kW with a 0.5-s voxel illumination time (e.g., 0.5-s gantry rotation and pitch of one), predicted a relative SNR of 76%.

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    ABSTRACT: X-ray cone-beam computed tomography (CBCT) is widely used nowadays, mainly for its large volume coverage and hardware compatibility with open-gantry x-ray imaging systems. As the size of x-ray illumination increases, an inevitable and adverse effect is the boost of scatter contamination on the x-ray images, which becomes one of the fundamental limitations of CBCT imaging. The large scatter signals in CBCT cause severe streaking and cupping artifacts in the CT images and greatly hamper the applications of CBCT due to its degraded image quality as compared to that of the conventional x-ray CT scanner. Research on scatter correction has gained heated attention in recent years. In this review, we first analyze the magnitudes of scatter in CBCT and its resultant errors in the reconstructed images. The existing CBCT scatter correction methods are then summarized in several categories: pre-processing methods, and post-processing methods including measurement-based, software-based, hardware-based decomposition and hybrid methods. An important issue related to the post-processing methods, the noise increase in the scatter corrected images, is also discussed. Although numerous scatter correction methods have been proposed in the literature, each approach has its own strengths and drawbacks and an optimal and standard method is still elusive. This review provides a comprehensive summary of the current research on scatter correction, and suggests future directions from the authors' perspective.
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