title: Validation of the CT-MRI image registration with a dedicated phantom.
abstract: OBJECTIVE
  The present study was aimed at verifying the automatic registration of the Focal (Elekta) platform with a dedicated phantom.
  
  
  METHODS
  A phantom that simulates the pelvis region in a stylised way and finalised to the registration of computed tomography-magnetic resonance images was designed and realised. After acquiring the two sets of images, the registration was performed both in automatic and manual mode to verify whether they were comparable. To test the repeatability of the automatic registration, some known rigid transformations were imposed to the original images. If the registration method works correctly, parameters which bring the images into alignment must always be the same.
  
  
  RESULTS
  Automatic registration performed by the software did not prove satisfactory, whereas if a specific tool [volume of interest (VOI) tool] allowing the calculation to be limited to the landmark region was used, the registration parameters were comparable with those of the manual registration. Regarding the repeatability of the automatic registration, the software brought the images in the correct alignment performing translations and rotations along the longitudinal axis up to 40°, while it was not satisfactory for rotations along the transverse axes.
  
  
  CONCLUSIONS
  The experimental results showed that in clinical application automatic registration is reliable if the VOI tool that includes visible landmarks in both studies is used. However, because the algorithm did not prove sensitive to rotations along the transverse axes, the position of the patient during the examinations plays a crucial role.
authors.affiliation: PH3DRA Laboratories (PHysics for Dating Diagnostic Dosimetry Research and Applications), Dipartimento di Fisica e Astronomia, Università di Catania and INFN-Catania, Via Santa Sofia 64, 95123, Catania, Italy. sofia.spampinato@ct.infn.it.|Struttura Complessa di Radiodiagnostica e Radioterapia, Azienda Ospedaliero-Universitaria Policlinico di Catania, Via Santa Sofia 78, 95123, Catania, Italy. sofia.spampinato@ct.infn.it.
authors.forename: Sofia
authors.initials: S
authors.lastname: Spampinato
authors.affiliation: PH3DRA Laboratories (PHysics for Dating Diagnostic Dosimetry Research and Applications), Dipartimento di Fisica e Astronomia, Università di Catania and INFN-Catania, Via Santa Sofia 64, 95123, Catania, Italy.|Dipartimento di Specialità Medico-Chirurgiche, Scuola di Specializzazione in Fisica Medica, Università degli Studi di Catania, Via Santa Sofia 78, 95123, Catania, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Gueli
authors.affiliation: Struttura Complessa di Radiodiagnostica e Radioterapia, Azienda Ospedaliero-Universitaria Policlinico di Catania, Via Santa Sofia 78, 95123, Catania, Italy.|Dipartimento di Specialità Medico-Chirurgiche, Scuola di Specializzazione in Fisica Medica, Università degli Studi di Catania, Via Santa Sofia 78, 95123, Catania, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Raffaele
authors.affiliation: Struttura Complessa di Radiodiagnostica e Radioterapia, Azienda Ospedaliero-Universitaria Policlinico di Catania, Via Santa Sofia 78, 95123, Catania, Italy.|Dipartimento di Specialità Medico-Chirurgiche, Scuola di Specializzazione in Fisica Medica, Università degli Studi di Catania, Via Santa Sofia 78, 95123, Catania, Italy.
authors.forename: Concetta
authors.initials: C
authors.lastname: Stancampiano
authors.affiliation: Struttura Complessa di Radiodiagnostica e Radioterapia, Azienda Ospedaliero-Universitaria Policlinico di Catania, Via Santa Sofia 78, 95123, Catania, Italy.
authors.forename: Giovanni Carlo
authors.initials: GC
authors.lastname: Ettorre
mesh_terms: D000465:Algorithms; D006801:Humans; D008279:Magnetic Resonance Imaging; D064847:Multimodal Imaging; D019047:Phantoms, Imaging / Q000592:standards*; D014057:Tomography, X-Ray Computed; D054928:Validation Studies as Topic