. Geometric calibration for half-cover scanning in circular cone-beam CT[J]. Editorial Office of Optics and Precision Engineering, 2013,21(7): 1659-1665
A highprecision method was investigated to realize the geometric calibration of halfcover scanning in circular conebeam Computed Tomography (CT). First
projected areas of steel balls were segmented from the background by using the Otsus method
and the mass centers of balls were calculated. Then
the elliptic functions for mass centers were fitted by the leastsquare algorithm
and the rotation angle of detector was determined by Chos geometric calibration method for circular scanning. Finally
the rotated mass centers were fitted as two ellipses
and the rest geometric parameters except the tilted angle of detector were calculated by using Noos geometric calibration method for circular scanning. Experimental results indicate that the measuring precisions of rotation angle and skew angle for the detector are 0.02 and 0.01
respectively
the measuring precisions of sourcedetectordistance and sourceobjectdistance are 0.05 mm and 0.01 mm
respectively; and the calculating precisions of orthogonal projection coordinates of source are 0.07 mm and 0.15 mm. The proposed method depress the geometric artifacts significantly
and can satisfy the demands of highprecision image reconstruction.
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references
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