title: Accuracy of Elastic Fusion of Prostate Magnetic Resonance and Transrectal Ultrasound Images under Routine Conditions: A Prospective Multi-Operator Study.
abstract: OBJECTIVE
  To evaluate in unselected patients imaged under routine conditions the co-registration accuracy of elastic fusion between magnetic resonance (MR) and ultrasound (US) images obtained by the Koelis Urostation™.
  
  
  METHODS
  We prospectively included 15 consecutive patients referred for placement of intraprostatic fiducials before radiotherapy and who gave written informed consent by signing the Institutional Review Board-approved forms. Three fiducials were placed in the prostate under US guidance in standardized positions (right apex, left mid-gland, right base) using the Koelis Urostation™. Patients then underwent prostate MR imaging. Four operators outlined the prostate on MR and US images and an elastic fusion was retrospectively performed. Fiducials were used to measure the overall target registration error (TRE3D), the error along the antero-posterior (TREAP), right-left (TRERL) and head-feet (TREHF) directions, and within the plane orthogonal to the virtual biopsy track (TRE2D).
  
  
  RESULTS
  Median TRE3D and TRE2D were 3.8-5.6 mm, and 2.5-3.6 mm, respectively. TRE3D was significantly influenced by the operator (p = 0.013), fiducial location (p = 0.001) and 3D axis orientation (p<0.0001). The worst results were obtained by the least experienced operator. TRE3D was smaller in mid-gland and base than in apex (average difference: -1.21 mm (95% confidence interval (95%CI): -2.03; -0.4) and -1.56 mm (95%CI: -2.44; -0.69) respectively). TREAP and TREHF were larger than TRERL (average difference: +1.29 mm (95%CI: +0.87; +1.71) and +0.59 mm (95%CI: +0.1; +0.95) respectively).
  
  
  CONCLUSIONS
  Registration error values were reasonable for clinical practice. The co-registration accuracy was significantly influenced by the operator's experience, and significantly poorer in the antero-posterior direction and at the apex.
authors.affiliation: Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Hôpital Edouard Herriot, Lyon, France.
authors.forename: Paul
authors.initials: P
authors.lastname: Moldovan
authors.affiliation: Hospices Civils de Lyon, Department of Radiation Oncology, Centre Hospitalier Lyon-Sud, Pierre-Bénite, France.
authors.forename: Corina
authors.initials: C
authors.lastname: Udrescu
authors.affiliation: Hospices Civils de Lyon, Department of Urology, Hôpital Edouard Herriot, Lyon, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Ravier
authors.affiliation: Inserm, U1032, LabTau, Lyon, France.
authors.forename: Rémi
authors.initials: R
authors.lastname: Souchon
authors.affiliation: Hospices Civils de Lyon, Service de Biostatistique et Bioinformatique, Lyon, France.|Université de Lyon, Lyon, France.|CNRS, UMR5558, Laboratoire de Biométrie et Biologie Evolutive, Equipe Biostatistique-Santé, Villeurbanne, France.
authors.forename: Muriel
authors.initials: M
authors.lastname: Rabilloud
authors.affiliation: Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Hôpital Edouard Herriot, Lyon, France.
authors.forename: Flavie
authors.initials: F
authors.lastname: Bratan
authors.affiliation: Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Hôpital Edouard Herriot, Lyon, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Sanzalone
authors.affiliation: Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Hôpital Edouard Herriot, Lyon, France.
authors.forename: Fanny
authors.initials: F
authors.lastname: Cros
authors.affiliation: Hospices Civils de Lyon, Department of Urology, Hôpital Edouard Herriot, Lyon, France.|Inserm, U1032, LabTau, Lyon, France.|Université de Lyon, Lyon, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Crouzet
authors.affiliation: Hospices Civils de Lyon, Department of Urology, Hôpital Edouard Herriot, Lyon, France.|Inserm, U1032, LabTau, Lyon, France.|Université de Lyon, Lyon, France.
authors.forename: Albert
authors.initials: A
authors.lastname: Gelet
authors.affiliation: Hospices Civils de Lyon, Department of Radiation Oncology, Centre Hospitalier Lyon-Sud, Pierre-Bénite, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Chapet
authors.affiliation: Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Hôpital Edouard Herriot, Lyon, France.|Inserm, U1032, LabTau, Lyon, France.|Université de Lyon, Lyon, France.
authors.forename: Olivier
authors.identifier: http://orcid.org/0000-0002-0030-478X
authors.initials: O
authors.lastname: Rouvière
mesh_terms: D000368:Aged; D004548:Elasticity; D057918:Fiducial Markers; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000592:standards; D008279:Magnetic Resonance Imaging; D008297:Male; D011467:Prostate / Q000000981:diagnostic imaging*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging; D012007:Rectum; D014463:Ultrasonography