title: Magnetic resonance imaging of the ear for patient-specific reconstructive surgery.
abstract: BACKGROUND
  Like a fingerprint, ear shape is a unique personal feature that should be reconstructed with a high fidelity during reconstructive surgery. Ear cartilage tissue engineering (TE) advantageously offers the possibility to use novel 3D manufacturing techniques to reconstruct the ear, thus allowing for a detailed auricular shape. However it also requires detailed patient-specific images of the 3D cartilage structures of the patient's intact contralateral ear (if available). Therefore the aim of this study was to develop and evaluate an imaging strategy for acquiring patient-specific ear cartilage shape, with sufficient precision and accuracy for use in a clinical setting.
  
  
  METHODS
  Magnetic resonance imaging (MRI) was performed on 14 volunteer and six cadaveric auricles and manually segmented. Reproducibility of cartilage volume (Cg.V), surface (Cg.S) and thickness (Cg.Th) was assessed, to determine whether raters could repeatedly define the same volume of interest. Additionally, six cadaveric auricles were harvested, scanned and segmented using the same procedure, then dissected and scanned using high resolution micro-CT. Correlation between MR and micro-CT measurements was assessed to determine accuracy.
  
  
  RESULTS
  Good inter- and intra-rater reproducibility was observed (precision errors <4% for Cg.S and <9% for Cg.V and Cg.Th). Intraclass correlations were good for Cg.V and Cg.S (>0.82), but low for Cg.Th (<0.23) due to similar average Cg.Th between patients. However Pearson's coefficients showed that the ability to detect local cartilage shape variations is unaffected. Good correlation between clinical MRI and micro-CT (r>0.95) demonstrated high accuracy.
  
  
  CONCLUSIONS
  This study demonstrated that precision and accuracy of the proposed method was high enough to detect patient-specific variation in ear cartilage geometry. The present study provides a clinical strategy to access the necessary information required for the production of 3D ear scaffolds for TE purposes, including detailed patient-specific shape. Furthermore, the protocol is applicable in daily clinical practice with existing infrastructure.
authors.affiliation: Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
authors.forename: Luc
authors.initials: L
authors.lastname: Nimeskern
authors.affiliation: Department of Otorhinolaryngology, Ulm University Medical Center, Ulm, Germany.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Feldmann
authors.affiliation: Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
authors.forename: Willy
authors.initials: W
authors.lastname: Kuo
authors.affiliation: Department of Otorhinolaryngology, Ulm University Medical Center, Ulm, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Schwarz
authors.affiliation: Department of Diagnostic and Interventional Radiology, Ulm University Medical Center, Ulm, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Goldberg-Bockhorn
authors.affiliation: Department of Diagnostic and Interventional Radiology, Ulm University Medical Center, Ulm, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Dürr
authors.affiliation: Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
authors.forename: Ralph
authors.initials: R
authors.lastname: Müller
authors.affiliation: Department of Otorhinolaryngology, Ulm University Medical Center, Ulm, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Rotter
authors.affiliation: Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
authors.forename: Kathryn S
authors.initials: KS
authors.lastname: Stok
mesh_terms: D004423:Ear / Q000473:pathology / Q000601:surgery*; D004425:Ear Cartilage / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D019651:Plastic Surgery Procedures / Q000379:methods*; D023822:Tissue Engineering; D055114:X-Ray Microtomography