title: Acetabular cartilage assessment in patients with femoroacetabular impingement by using T2* mapping with arthroscopic verification.
abstract: OBJECTIVE
  To evaluate the ability of T2* mapping to help differentiate damaged from normal acetabular cartilage in patients with femoroacetabular impingement (FAI).
  
  
  METHODS
  The institutional review board approved this retrospective study, and the requirement to obtain informed consent was waived. The study complied with HIPAA guidelines. The authors reviewed T2* relaxation time maps of 28 hips from 26 consecutive patients (mean patient age, 28.2 years; range, 12-53 years; eight male patients (nine hips) with a mean age of 26.7 years [range, 16-53 years]; 18 female patients (19 hips) with a mean age of 28.9 years [range, 12-46 years]). Conventional diagnostic 3.0-T magnetic resonance (MR) arthrography was augmented by including a multiecho gradient-recalled echo sequence for T2* mapping. After imaging, acetabular and femoral data were separated and acetabular regions of interest were identified. Arthroscopic cartilage assessment with use of a modified Beck scale for acetabular cartilage damage was performed by an orthopedic surgeon who was blinded to the results of T2* mapping. A patient-specific acetabular projection with a T2* overlay was developed to anatomically correlate imaging data with those from surgery (the standard of reference). Results were analyzed by using receiver operating characteristic (ROC) curves.
  
  
  RESULTS
  The patient-specific acetabular projection enabled co-localization between the MR imaging and arthroscopic findings. T2* relaxation times for normal cartilage (Beck score 1, 35.3 msec ± 7.0) were significantly higher than those for cartilage with early changes (Beck score 2, 20.7 msec ± 6.0) and cartilage with more advanced degeneration (Beck scores 3-6, ≤19.8 msec ± 5.6) (P < .001). At ROC curve analysis, a T2* value of 28 msec was identified as the threshold for damaged cartilage, with a 91% true-positive and 13% false-positive rate for differentiating Beck score 1 cartilage (normal) from all other cartilages.
  
  
  CONCLUSIONS
  The patient-specific acetabular projection with a T2* mapping overlay enabled good anatomic localization of cartilage damage defined with a T2* threshold of 28 msec and less.
authors: From the Center for Magnetic Resonance Research, Department of Radiology (J.E., C.Z., M.J.N., M.B., P.H.), Department of Orthopaedic Surgery (M.J.N., M.B., P.M.), and Division of Biostatistics, School of Public Health (J.H.), University of Minnesota, 2021 6th St SE, 2-130 CMRR Building, Minneapolis, MN 55455; and Department of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands (R.G.).
authors: Jutta
authors: J
authors: Ellermann
authors: Connor
authors: C
authors: Ziegler
authors: Mikko J
authors: MJ
authors: Nissi
authors: Rainer
authors: R
authors: Goebel
authors: John
authors: J
authors: Hughes
authors: Michael
authors: M
authors: Benson
authors: Peter
authors: P
authors: Holmberg
authors: Patrick
authors: P
authors: Morgan
mesh_terms: D000293:Adolescent; D000328:Adult; D001182:Arthroscopy; D002358:Cartilage, Articular / Q000473:pathology*; D002648:Child; D005260:Female; D057925:Femoracetabular Impingement / Q000473:pathology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies