Practical improvement of geometric parameter estimation for cone beam microCT imaging

Stacia A. Sawyer, Eric C. Frey

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Scopus citations


Accurate physical measurement of system geometric misalignments is difficult, so an accurate method of estimating the geometric parameters is needed. Several methods have been proposed that involve measuring projections of spheres at multiple projection views. For high resolution microCT systems, the estimation accuracy of the projected position of the sphere center is a critical factor in determining the geometric parameter accuracy. We have investigated several methods for improving the sphere center estimation. We simulated spheres of varying diameters and used several methods to estimate the positions of the projected sphere centers. The estimated center positions served as the input to methods for estimating the geometric parameters in order to assess the effect on geometric parameter accuracy. The center estimation methods investigated included computing the centroid and fitting the projection with a Gaussian or the analytic equation for the cone beam projection of a sphere. We found that the differences between the true and estimated projected center positions were smaller when fitted with the sphere's projection equation. In addition, using smaller spheres resulted in improved estimate accuracy. Using a phantom consisting of three 1 mm diameter spheres and with curve fitting to estimate the position of the spherical center, we were are able to obtain artifact-free reconstructions for a 42 μm pixel size on our prototype physical microCT system.

Original languageEnglish (US)
Title of host publication2005 IEEE Nuclear Science Symposium Conference Record -Nuclear Science Symposium and Medical Imaging Conference
Number of pages5
StatePublished - Dec 1 2005
EventNuclear Science Symposium Conference Record, 2005 IEEE - , Puerto Rico
Duration: Oct 23 2005Oct 29 2005

Publication series

NameIEEE Nuclear Science Symposium Conference Record
ISSN (Print)1095-7863


OtherNuclear Science Symposium Conference Record, 2005 IEEE
Country/TerritoryPuerto Rico

ASJC Scopus subject areas

  • Radiation
  • Nuclear and High Energy Physics
  • Radiology Nuclear Medicine and imaging


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