title: A comparison of similarity measures for use in 2-D-3-D medical image registration.
abstract: A comparison of six similarity measures for use in intensity-based two-dimensional-three-dimensional (2-D-3-D) image registration is presented. The accuracy of the similarity measures are compared to a "gold-standard" registration which has been accurately calculated using fiducial markers. The similarity measures are used to register a computed tomography (CT) scan of a spine phantom to a fluoroscopy image of the phantom. The registration is carried out within a region-of-interest in the fluoroscopy image which is user defined to contain a single vertebra. Many of the problems involved in this type of registration are caused by features which were not modeled by a phantom image alone. More realistic "gold-standard" data sets were simulated using the phantom image with clinical image features overlaid. Results show that the introduction of soft-tissue structures and interventional instruments into the phantom image can have a large effect on the performance of some similarity measures previously applied to 2-D-3-D image registration. Two measures were able to register accurately and robustly even when soft-tissue structures and interventional instruments were present as differences between the images. These measures were pattern intensity and gradient difference. Their registration accuracy, for all the rigid-body parameters except for the source to film translation, was within a root-mean-square (rms) error of 0.54 mm or degrees to the "gold-standard" values. No failures occurred while registering using these measures.
authors.affiliation: Division of Radiological Sciences, UMDS, Guy's Hospital, London UK.
authors.forename: G P
authors.initials: GP
authors.lastname: Penney
authors.forename: J
authors.initials: J
authors.lastname: Weese
authors.forename: J A
authors.initials: JA
authors.lastname: Little
authors.forename: P
authors.initials: P
authors.lastname: Desmedt
authors.forename: D L
authors.initials: DL
authors.lastname: Hill
authors.forename: D J
authors.initials: DJ
authors.lastname: Hawkes
mesh_terms: D000465:Algorithms; D005471:Fluoroscopy; D006801:Humans; D019047:Phantoms, Imaging; D013131:Spine / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed