title: Accuracy of cartilage and subchondral bone spatial thickness distribution from MRI.
abstract: OBJECTIVE
  To assess three-dimensional measurement accuracy of articular cartilage (AC) and subchondral bone (SB) thickness from MRI.
  
  
  METHODS
  A computer program was used to calculate AC and SB thickness from MRI (three-dimensional spoiled gradient echo (SPGR),.31-mm resolution, 1-mm slice thickness) of six adult femoral heads. Specimens were imaged in five anatomical planes ranging between +30 degrees to -30 degrees from neutral and cut into 2-mm thick sections along the five anatomical planes. Faxitron x-ray was used to produce microradiographic (.05-mm resolution) images of the sections.
  
  
  RESULTS
  In-plane measurement accuracy was.165 +/-.108 mm for AC thickness and.387 +/-.174 mm for SB thickness. Taking into account chemical-shift misregistration in SB thickness, accuracy of measurements improved to.213 +/- 128 mm. Out-of-plane (three-dimensional) thickness accuracy of the model, assessed by numerical simulation, was.015 mm. However, three-dimensional thickness errors in specimens were.319 +/-.256 mm for AC and.253 +/-.183 mm for SB thickness.
  
  
  CONCLUSIONS
  Errors in three-dimensional AC thickness were attributed to volume-averaging effects caused by oblique intersection of the image plane with the joint surface. Errors in three-dimensional SB thickness were attributed to chemical-shift artifact. We conclude that accuracy of AC thickness is within clinically acceptable standards but that more sophisticated pulse sequences are needed to improve the measurement of SB thickness.
authors.affiliation: Department of Orthopaedic Surgery, Biomotion Laboratory and MGH Institute of Health Professions, Graduate Programs in Physical Therapy, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts 02114, USA. cmcgibbon@partners.org
authors.forename: Chris A
authors.initials: CA
authors.lastname: McGibbon
authors.forename: Jenny
authors.initials: J
authors.lastname: Bencardino
authors.forename: Eren D
authors.initials: ED
authors.lastname: Yeh
authors.forename: William E
authors.initials: WE
authors.lastname: Palmer
mesh_terms: D000328:Adult; D002356:Cartilage / Q000033:anatomy & histology*; D005270:Femur Head / Q000033:anatomy & histology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008954:Models, Biological; D015203:Reproducibility of Results; D012984:Software