Optimization of detector geometry for aliasing artifact reduction in the third-generation CT

Jiang Hsieh

doi:10.1117/12.273986

2 May 1997 Optimization of detector geometry for aliasing artifact reduction in the third-generation CT

Jiang Hsieh

Proceedings Volume 3032, Medical Imaging 1997: Physics of Medical Imaging; (1997) https://doi.org/10.1117/12.273986
Event: Medical Imaging 1997, 1997, Newport Beach, CA, United States

Abstract

Many clinical applications demand CT scanners to provide 15 to 20 line pairs per centimeter resolution. For a conventional third generation CT scanner, this demand present a special challenge because of the inherent sampling limitations. If special care is not taken, aliasing artifacts could result. These artifacts typically appear as fine streaks irradiating from high density objects.One of the methods used to achieve aliasing-free CT images is to increase the sampling density by x-ray focal spot wobbling. This is achieved by first acquiring a projection with focal spot at one position. The gantry is then rotated to a position so that the detector cells straddle the cell positions at the previous view.At the same time, the focal spot is deflected back so that it overlaps the previous focal spot position. The two set of projections form an interlaced projection with much higher sampling density. Since the detector cells form an arc concentric to the x-ray focal spot, the interlaced samples are not uniformly spaced. Detailed analysis indicates that the position displacement increases as a function of the detector angle, which results in less effective aliasing artifact reduction for objects located away from the iso-center. To overcome this shortcoming,w e propose a new detector geometry. Computer simulations have shown that further aliasing artifact reduction can be achieved for off-centered objects. In addition, an improvement in in-plane resolution can be realized, due to an increase in the magnification factor and a reduction in the effective detector cell cross-section. We further show that a closed form solution for the tomographic reconstruction is possible when certain constraints are met.

Citation Download Citation

Jiang Hsieh "Optimization of detector geometry for aliasing artifact reduction in the third-generation CT", Proc. SPIE 3032, Medical Imaging 1997: Physics of Medical Imaging, (2 May 1997); https://doi.org/10.1117/12.273986

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KEYWORDS

Sensors

X-ray computed tomography

Scanners

Reconstruction algorithms

Fluctuations and noise

Computer simulations

Tomography

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