title: In vitro comparison of water displacement method and 3 Tesla MRI for MR-volumetry of the olfactory bulb: which sequence is appropriate?
abstract: OBJECTIVE
  Magnetic resonance imaging olfactory bulb (OB) volumetry (OBV) is already used as a complementary prognostic tool to assess olfactory disorders. However, a reference standard in imaging for OBV has not been established. The aim of this in vitro study was to compare volumetric results of different magnetic resonance sequences for OBV at 3 T to genuine OB volumes measured by water displacement.
  
  
  METHODS
  The volumes of 15 human cadaveric OBs were measured using the water displacement method in this institutional review board-approved prospective study. The magnetic resonance imaging protocol at 3 T included constructive interference in steady state (CISS), T2-weighted (T2w) three-dimensional (3D) sampling perfection with application-optimized contrasts using different flip-angle evolutions (SPACE), T2w two-dimensional (2D) turbo spin-echo (TSE), and T1-weighted (T1w) 3D fast low-angle shot (FLASH) sequences. Two blinded observers independently performed two OB volumetric assessments per bulbus and sequence. Intraobserver and interobserver reliabilities were assessed by intraclass correlation coefficients. Bland-Altman plots were analyzed to evaluate systematic biases and concordance correlation coefficients to assess reproducibility.
  
  
  RESULTS
  For both observers, intraclass correlation coefficient analysis yielded almost perfect results for intraobserver reliability (CISS, 0.94-0.98; T2w 3D SPACE, 0.93-0.98; T2w 2D TSE, 0.98-0.98; T1w 3D FLASH, 0.95-0.99). Interobserver reliability showed almost perfect agreement for all sequences (CISS, 0.98; T2w 3D SPACE, 0.89; T2w 2D TSE, 0.93; T1w 3D FLASH, 0.97). The CISS sequence yielded the highest mean concordance correlation coefficient (0.95) and the highest combination of precision (0.97) and accuracy (0.98) values. In comparison with the water displacement method, Bland-Altman analyses revealed the lowest systematic bias (-0.5%) for the CISS sequence, followed by T1w 3D FLASH (-1.3%), T2w 3D SPACE (-7.5%), and T2w 2D TSE (-10.9%) sequences.
  
  
  CONCLUSIONS
  Compared to the water displacement method, the CISS sequence is suited best to validly and reliably measure OB volumes because of its highest values for accuracy and precision and lowest systematic bias.
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital - Friedrich Schiller University Jena, Germany. hartmut.burmeister@med.uni-jena.de
authors.forename: Hartmut Peter
authors.initials: HP
authors.lastname: Burmeister
authors.forename: Constanze
authors.initials: C
authors.lastname: Möslein
authors.forename: Thomas
authors.initials: T
authors.lastname: Bitter
authors.forename: Rosemarie
authors.initials: R
authors.lastname: Fröber
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Herrmann
authors.forename: Pascal Andreas Thomas
authors.initials: PA
authors.lastname: Baltzer
authors.forename: Hilmar
authors.initials: H
authors.lastname: Gudziol
authors.forename: Matthias
authors.initials: M
authors.lastname: Dietzel
authors.forename: Orlando
authors.initials: O
authors.lastname: Guntinas-Lichius
authors.forename: Werner Alois
authors.initials: WA
authors.lastname: Kaiser
mesh_terms: D016477:Artifacts; D002102:Cadaver; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009830:Olfactory Bulb / Q000033:anatomy & histology*; D011446:Prospective Studies; D015203:Reproducibility of Results; D014867:Water
chemical_list: D014867:Water