Volumetric Reconstruction in the MicroCat Tomography System
A Thesis Presented for the
Master of Science Degree
University of Tennessee, Knoxville
Joshua Cates, May 2000
An isosurface rendering of the skull in a 3D MicroCat reconstruction.
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Abstract
A new system for x-ray cone-beam micro-tomography has been developed to screen mice for internal phenotypic
abnormalities at the Oak Ridge National Laboratory Mammalian Genetics Facility. Currently this
system uses an image reconstruction algorithm that is based on two-dimensional (fan-beam) reconstruction
techniques. The disparity between the actual scanner geometry and that assumed for reconstruction
purposes introduces artifacts into the reconstruction volume that become increasingly worse the
further their axial distance from the midplane. In order to reconcile this disparity and reduce
axial distortion artifacts, a volumetric reconstruction algorithm based on cone-beam geometry was
implemented. The volumetric algorithm is derived and its heuristic implementation is explained
within the constraints of the system, which limit the arclength of the scanning trajectory.
Reconstructions using the volumetric algorithm are analyzed and compared to reconstructions from the
current method. We show that our implementation produces images of equivalent quality in the midplane,
and a marked decrease in axial distortion elsewhere. Volume reconstruction times are shown to be
comparable to those currently achievable. The theoretical foundations are given for future work to
optimize the implementation through parallelization and by overcoming the data sufficiency problem.
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cates@cs.utk.edu . 10/12/00
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