title: Segmentation and quantification of bone erosions in high-resolution peripheral quantitative computed tomography datasets of the metacarpophalangeal joints of patients with rheumatoid arthritis.
abstract: OBJECTIVE
  To develop a precise three-dimensional (3D) segmentation technique for bone erosions in high-resolution peripheral quantitative CT (HR-pQCT) datasets to measure their volume, surface area and shape parameters. Assessment of bone erosions in patients with RA is important for diagnosis and evaluation of treatment efficacy. HR-pQCT allows quantifying periarticular bone loss in arthritis.
  
  
  METHODS
  HR-pQCT scans with a spatial resolution of about 120 µm of the second to fourth metacarpophalangeal joints were acquired in patients with RA. Erosions were identified by placing a seed point in each of them. After applying 3D segmentation, the volume, surface area and sphericity of erosions were calculated. Results were compared with an approximation method using manual measurements. Intra- and interoperator precision analysis was performed for both the 3D segmentation and the manual technique.
  
  
  RESULTS
  Forty-three erosions were assessed in 18 datasets. Intra- and interoperator precisions (RMSCV/RMSSD) for erosion volume were 5.66%/0.49 mm(3) and 7.76%/0.76 mm(3), respectively. The correlation between manual measurements and their simulation using segmentation volumes was r = 0.87. Precision errors for the manual method were 15.39% and 0.36 mm(3), respectively.
  
  
  CONCLUSIONS
  We developed a new precise 3D segmentation technique for quantification of bone erosions in HR-pQCT datasets that correlates to the volume, shape and surface area of the erosion. The technique allows fast and effective measurement of the erosion size and could therefore be helpful for rapid and quantitative assessment of erosion size.
authors.affiliation: Institute of Medical Physics, University of Erlangen-Nuremberg, Henkestr. 91, 91052 Erlangen, Germany. dominique.toepfer@imp.uni-erlangen.de.
authors.forename: Dominique
authors.initials: D
authors.lastname: Töpfer
authors.forename: Stephanie
authors.initials: S
authors.lastname: Finzel
authors.forename: Oleg
authors.initials: O
authors.lastname: Museyko
authors.forename: Georg
authors.initials: G
authors.lastname: Schett
authors.forename: Klaus
authors.initials: K
authors.lastname: Engelke
mesh_terms: D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008662:Metacarpophalangeal Joint / Q000000981:diagnostic imaging*; D008875:Middle Aged; D012372:ROC Curve; D011856:Radiographic Image Enhancement; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: HR-pQCT; bone erosions; image processing; metacarpophalangeal joints; precision analysis; rheumatoid arthritis