title: Inherently 3-dimensional method for measurement of computed tomographic resolution anisotropy.
abstract: OBJECTIVE
  Current techniques to measure computed tomography (CT) spatial resolution use separate methods for in-plane and out-of-plane directions. The growing use of near-isotropic voxel size necessitates a new single method that inherently measures resolution in any direction.
  
  
  METHODS
  We introduce a method using a set of numerous glass microspheres suspended in a small volume from which a mean sphere image is constructed. Projecting asymptotes after imaging different microsphere sets with decreasing diameters provides an inherently 3-dimensional measure of spatial resolution and anisotropy. We apply the method to both a flat-panel and multidetector CT scanner.
  
  
  RESULTS
  The full-width at half-maximum from line profiles through mean sphere in transverse directions corresponds to known microsphere diameters. Increased longitudinal full-width at half-maximum corresponds to known anisotropy, which is larger for a multidetector CT scanner than for a flat-panel CT scanner.
  
  
  CONCLUSIONS
  A new single method to measure CT resolution is inherently isotropic.
authors.affiliation: Department of Radiology, Massachusetts General, Hospital, Boston, MA 02114-2698, USA. sejones@partners.org
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Jones
authors.forename: Michael
authors.initials: M
authors.lastname: Grasruck
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schmidt
authors.forename: Ijad
authors.initials: I
authors.lastname: Madisch
authors.forename: Ryan
authors.initials: R
authors.lastname: Egeland
authors.forename: Tom
authors.initials: T
authors.lastname: Brady
authors.forename: Rajiv
authors.initials: R
authors.lastname: Gupta
mesh_terms: D016880:Anisotropy; D021621:Imaging, Three-Dimensional; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*