title: Phantom Study Investigating the Accuracy of Manual and Automatic Image Fusion with the GE Logiq E9: Implications for use in Percutaneous Liver Interventions.
abstract: OBJECTIVE
  To determine the accuracy of automatic and manual co-registration methods for image fusion of three-dimensional computed tomography (CT) with real-time ultrasonography (US) for image-guided liver interventions.
  
  
  METHODS
  CT images of a skills phantom with liver lesions were acquired and co-registered to US using GE Logiq E9 navigation software. Manual co-registration was compared to automatic and semiautomatic co-registration using an active tracker. Also, manual point registration was compared to plane registration with and without an additional translation point. Finally, comparison was made between manual and automatic selection of reference points. In each experiment, accuracy of the co-registration method was determined by measurement of the residual displacement in phantom lesions by two independent observers.
  
  
  RESULTS
  Mean displacements for a superficial and deep liver lesion were comparable after manual and semiautomatic co-registration: 2.4 and 2.0 mm versus 2.0 and 2.5 mm, respectively. Both methods were significantly better than automatic co-registration: 5.9 and 5.2 mm residual displacement (p < 0.001; p < 0.01). The accuracy of manual point registration was higher than that of plane registration, the latter being heavily dependent on accurate matching of axial CT and US images by the operator. Automatic reference point selection resulted in significantly lower registration accuracy compared to manual point selection despite lower root-mean-square deviation (RMSD) values.
  
  
  CONCLUSIONS
  The accuracy of manual and semiautomatic co-registration is better than that of automatic co-registration. For manual co-registration using a plane, choosing the correct plane orientation is an essential first step in the registration process. Automatic reference point selection based on RMSD values is error-prone.
authors.affiliation: Department of Radiology, Leiden University Medical Centre, Albinusdreef 2, 2300 RC, Leiden, The Netherlands. m.c.burgmans@lumc.nl.
authors.forename: Mark Christiaan
authors.initials: MC
authors.lastname: Burgmans
authors.affiliation: Department of Radiology, Leiden University Medical Centre, Albinusdreef 2, 2300 RC, Leiden, The Netherlands.
authors.forename: J Michiel
authors.initials: JM
authors.lastname: den Harder
authors.affiliation: Department of Radiology, Leiden University Medical Centre, Albinusdreef 2, 2300 RC, Leiden, The Netherlands.|Interventional and Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Philippa
authors.initials: P
authors.lastname: Meershoek
authors.affiliation: Interventional and Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Nynke S
authors.initials: NS
authors.lastname: van den Berg
authors.affiliation: Department of Interventional Radiology, Singapore General Hospital, Outram Road, Singapore, 169608, Singapore.
authors.forename: Shaun Xavier Ju Min
authors.initials: SXJM
authors.lastname: Chan
authors.affiliation: Interventional and Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Fijs W B
authors.initials: FWB
authors.lastname: van Leeuwen
authors.affiliation: Department of Radiology, Leiden University Medical Centre, Albinusdreef 2, 2300 RC, Leiden, The Netherlands.
authors.forename: Arian R
authors.initials: AR
authors.lastname: van Erkel
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008099:Liver; D064847:Multimodal Imaging / Q000379:methods; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014463:Ultrasonography / Q000379:methods*
keywords: Co-registration methods; Image fusion; Liver interventions; Phantom study; Volume navigation