title: Reanalysis precision of 3D quantitative computed tomography (QCT) of the spine.
abstract: OBJECTIVE
  To evaluate the precision of 3D QCT of the spine.
  
  
  METHODS
  Interoperator analysis reproducibility of two different 3D QCT analysis systems (QCTPro from Mindways Software Inc and MIAF-Spine from the Institute of Medical Physics, University of Erlangen) was evaluated in 29 postmenopausal women. For each analysis system four different trained operators analyzed all scans independently. Results of the vertebrae L1 and L2 were averaged. With QCTPro BMD of the central trabecular elliptical VOI was analyzed. With MIAF-Spine integral, trabecular and cortical BMD, BMC and volume were analyzed in the total vertebral body, the elliptical cylinder and the Osteo VOIs that were further subdivided into superior, mid and inferior subVOIs, each.
  
  
  RESULTS
  Precision errors (%CVrms) for the central trabecular VOI that is also used in the traditional single slice QCT techniques were 1.7+/-2.2% and 0.6+/-0.6% for QCTPro and MIAF-Spine, respectively. For MIAF-Spine integral BMD precision errors were lowest in the total and mid Osteo subVOIs (0.5+/-0.5%). Trabecular BMD precision errors were lowest in the mid subVOIs (0.6+/-0.6%). For trabecular BMD there were no differences among the total vertebral body, elliptical cylinder and Osteo VOIs. Cortical BMD precision errors were lowest in the mid total vertebral body subVOI (2.1+/-1.9%) and slightly higher in the mid of the Osteo subVOI. Precision errors in the superior and inferior subVOIs were typically 50% to 100% higher compared to the mid subVOIs.
  
  
  CONCLUSIONS
  Compared to QCTPro MIAF-Spine uses an automated 3D segmentation and an anatomic vertebral coordinate system to position a variety of analysis VOIs. This results in better precision than the more manually assisted analysis used by QCTPro. In-vivo precision errors will be approximately 0.5% higher compared to the analysis precision errors reported here (13). The results demonstrate that with 3D QCT in-vivo precision errors of about 1%-1.5% for trabecular and 2.5% to 3% for cortical bone can be obtained in postmenopausal women.
authors.affiliation: Institute of Medical Physics, University of Erlangen, Germany. klaus.engelke@imp.uni-erlangen.de
authors.forename: Klaus
authors.initials: K
authors.lastname: Engelke
authors.forename: André
authors.initials: A
authors.lastname: Mastmeyer
authors.forename: Valérie
authors.initials: V
authors.lastname: Bousson
authors.forename: Thomas
authors.initials: T
authors.lastname: Fuerst
authors.forename: Jean-Denis
authors.initials: JD
authors.lastname: Laredo
authors.forename: Willi A
authors.initials: WA
authors.lastname: Kalender
mesh_terms: D015519:Bone Density; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D008875:Middle Aged; D017698:Postmenopause; D015203:Reproducibility of Results; D012984:Software; D013131:Spine / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed