title: Automated three-dimensional registration of high-resolution peripheral quantitative computed tomography data to quantify size and shape changes of arthritic bone erosions.
abstract: OBJECTIVE
  To monitor size and shape changes of bone erosions and changes in BMD in the vicinity of the erosion and in the periarticular trabecular compartment of patients with RA using high-resolution peripheral quantitative CT (HR-pQCT) imaging and to compare an automated three-dimensional (3D) image processing technique with manual measurements of erosion width and depth.
  
  
  METHODS
  The shape of 40 bone erosions and composition of bone around the erosions were analysed in the MCP joints of 22 RA patients both manually and by semi-automated 3D image processing at two different time points. Periosteal segmentation was performed using volume growing and morphological operations. Image registration was applied for transfer of baseline segmentations to follow-up datasets.
  
  
  RESULTS
  Eight erosions decreased in size, 6 increased and 28 remained stable. Increasing erosions were more spherical and smaller at baseline compared with decreasing or stable erosions. BMD in the vicinity of shrinking erosions increased, while it decreased next to expanding erosions. There was moderate agreement in the determination of erosion volume between semi-automated and manual measurements, but agreement was poor when assessing changes in volume over time.
  
  
  CONCLUSIONS
  Longitudinal changes in erosion size and shape and of BMD in the vicinity of an erosion can be measured. BMD changes are associated with progression and regression of erosions. However, the semi-automated and manual approaches did not classify longitudinal changes of erosion volume in the same way. Further research is necessary to define the nature of these differences.
authors.affiliation: Institute of Medical Physics and dominique.toepfer@imp.uni-erlangen.de.
authors.forename: Dominique
authors.initials: D
authors.lastname: Töpfer
authors.affiliation: Institute of Medical Physics and.
authors.forename: Bastian
authors.initials: B
authors.lastname: Gerner
authors.affiliation: Department of Internal Medicine 3, Rheumatology and Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Finzel
authors.affiliation: Department of Internal Medicine 3, Rheumatology and Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kraus
authors.affiliation: Institute of Medical Physics and.
authors.forename: Oleg
authors.initials: O
authors.lastname: Museyko
authors.affiliation: Department of Internal Medicine 3, Rheumatology and Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Schett
authors.affiliation: Institute of Medical Physics and.
authors.forename: Klaus
authors.initials: K
authors.lastname: Engelke
mesh_terms: D000328:Adult; D000368:Aged; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology; D015519:Bone Density / Q000502:physiology; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008662:Metacarpophalangeal Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D018501:Antirheumatic Agents
keywords: bone erosions; high-resolution peripheral computed tomography; image processing; rheumatoid arthritis