title: Intra- and inter-observer reliability of quantitative analysis of the infra-patellar fat pad and comparison between fat- and non-fat-suppressed imaging--Data from the osteoarthritis initiative.
abstract: The infra-patellar fat pad (IPFP), as intra-articular adipose tissue represents a potential source of pro-inflammatory cytokines and its size has been suggested to be associated with osteoarthritis (OA) of the knee. This study examines inter- and intra-observer reliability of fat-suppressed (fs) and non-fat-suppressed (nfs) MR imaging for determination of IPFP morphological measurements as novel biomarkers. The IPFP of nine right knees of healthy Osteoarthritis Initiative participants was segmented by five readers, using fs and nfs baseline sagittal MRIs. The intra-observer reliability was determined from baseline and 1-year follow-up images. All segmentations were quality controlled (QC) by an expert reader. Reliability was expressed as root mean square coefficient of variation (RMS CV%). After QC, the inter-observer reliability for fs (nfs) imaging was 2.0% (1.1%) for IPFP volume, 2.1%/2.5% (1.6%/1.8%) for anterior/posterior surface areas, 1.8% (1.8%) for depth, and 2.1% (2.4%) for maximum sagittal area. The intra-observer reliability was 3.1% (5.0%) for volume, 2.3%/2.8% (2.5%/2.9%) for anterior/posterior surfaces, 1.9% (3.5%) for depth, and 3.3% (4.5%) for maximum sagittal area. IPFP volume from nfs images was systematically greater (+7.3%) than from fs images, but highly correlated (r=0.98). The results suggest that quantitative measurements of IPFP morphology can be performed with satisfactory reliability when expert QC is implemented. The IPFP is more clearly depicted in nfs images, and there is a small systematic off-set versus analysis from fs images. However, the high linear relationship between fs and nfs imaging suggests that fs images can be used to analyze IPFP morphology, when nfs images are not available.
authors.affiliation: Paracelsus Medical University Salzburg & Nuremberg, Institute of Anatomy, Strubergasse 21, A-5020 Salzburg, Austria. Electronic address: eva.steidle@pmu.ac.at.
authors.forename: E
authors.initials: E
authors.lastname: Steidle-Kloc
authors.affiliation: Paracelsus Medical University Salzburg & Nuremberg, Institute of Anatomy, Strubergasse 21, A-5020 Salzburg, Austria.
authors.forename: W
authors.initials: W
authors.lastname: Wirth
authors.affiliation: Paracelsus Medical University Salzburg & Nuremberg, Institute of Anatomy, Strubergasse 21, A-5020 Salzburg, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Ruhdorfer
authors.affiliation: Paracelsus Medical University Salzburg & Nuremberg, Institute of Anatomy, Strubergasse 21, A-5020 Salzburg, Austria.
authors.forename: T
authors.initials: T
authors.lastname: Dannhauer
authors.affiliation: Paracelsus Medical University Salzburg & Nuremberg, Institute of Anatomy, Strubergasse 21, A-5020 Salzburg, Austria.
authors.forename: F
authors.initials: F
authors.lastname: Eckstein
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging / Q000473:pathology*; D000368:Aged; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007717:Knee / Q000000981:diagnostic imaging / Q000473:pathology; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000473:pathology*; D010329:Patella / Q000000981:diagnostic imaging / Q000473:pathology*; D011446:Prospective Studies; D011786:Quality Control; D015203:Reproducibility of Results
keywords: Hoffa fat pad; Infra-patellar fat pad; Knee joint; Magnetic resonance imaging; Morphology; Osteoarthritis; Reliability