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A method for correcting for errors produced by variable magnification in three-dimensional tuned-aperture computed
1Department of Dentistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Objectives:
To develop and test a method for correcting tomosynthetic misregistration caused by variation in projective magnification.
Methods:
A tooth from a monkey was radiographed from various angles and distances using a solid-state sensor to which a plastic spacer with a wire frame was attached. The position of the tooth was fixed relative to both the frame and the sensor. Information derived from the frame's shadow was used to produce a series of tomosynthetic slices using tuned-aperture computed tomography (TACT(R)). One series was corrected for magnification errors and the other was not. Corresponding slices from each series were compared.
Results:
The corrected slice exhibited much less artifactual blur than its uncorrected counterpart. Linear traces through corresponding portions of these slice images demonstrated discrepancies in homologous dimensions attributable to systematic variations in projective magnification.
Conclusions:
Correcting for differences in projective magnification reduces both misregistration and scaling artifacts in tomosynthetically reconstructed volumes.