title: Feasibility of texture analysis for the assessment of biochemical changes in meniscal tissue on T1 maps calculated from delayed gadolinium-enhanced magnetic resonance imaging of cartilage data: comparison with conventional relaxation time measurements.
abstract: OBJECTIVE
  To (1) establish the feasibility of texture analysis for the in vivo assessment of biochemical changes in meniscal tissue on delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC), and (2) compare textural with conventional T1 relaxation time measurements calculated from dGEMRIC data ("T1(Gd) relaxation times").
  
  
  METHODS
  We enrolled 10 asymptomatic volunteers (7 men and 3 women; mean age, 27.2 +/- 4.5 years), without a history of meniscus damage, in our study. MRI of the right knee was performed at 3.0 T. An isotropic, 3-dimensional (3D), double-echo steady-state sequences was used for morphologic evaluation, and a dual flip angle 3D gradient echo sequence was used for T1(Gd) mapping. All MRI scans were performed 90 minutes after injection of 0.2 mmol/kg of Gd-diethylenetriamine pentaacetic acid (DTPA), and subsequently, during application of a compressive force (50% of the body weight) in the axial direction. Regions of interest, covering the central portions of the posterior horn of the medial meniscus, were defined on 3 adjacent sagittal sections. Based on the relaxation time maps, mean T1(Gd), as well as the T1(Gd) texture features derived from the co-occurrence matrix (COC: Angular Second Moment, Entropy, Inverse Difference Moment) and wavelet transform (WAV: WavEnLL, WavEnHL, WavEnHH, WavEnLH), were calculated. Paired t tests were used to assess differences between baseline and compression, and intraclass correlation coefficients (ICC) were calculated to establish the intrarater reliability of the measurements.
  
  
  RESULTS
  Mean T1(Gd) (-67.3 ms, P = 0.011), Angular Second Moment (-0.0002, P = 0.009), Entropy (+0.033, P = 0.025), WavEnLL (+1011.16, P = 0.002), WavEnHL (+18.64, P = 0.012), and WavEnLH (+72.74, P = 0.035) differed significantly between baseline and compression. Intrarater reliability was substantial for mean T1(Gd) relaxation times (ICC = 0.99-1.0), and also for T1(Gd) co-occurrence matrix (ICC = 0.63-0.92) and WAV (ICC = 0.86-0.98) features.
  
  
  CONCLUSIONS
  Texture features extracted from T1 maps calculated from dGEMRIC data are feasible for the in vivo assessment of biochemical changes in the menisci, such as might be induced by mechanical loading. Thus, T1(Gd) texture features complement conventional relaxation time measurements. Further studies are necessary to determine whether the mechanical compression, or a prolonged Gd-DTPA uptake, or both, are responsible for the observed decrease in mean T1(Gd) relaxation times in the menisci.
authors.affiliation: Department of Radiology, MR Center, Medical University of Vienna, Vienna, Austria. marius.mayerhoefer@meduniwien.ac.at
authors.forename: Marius E
authors.initials: ME
authors.lastname: Mayerhoefer
authors.forename: Goetz H
authors.initials: GH
authors.lastname: Welsch
authors.forename: Georg
authors.initials: G
authors.lastname: Riegler
authors.forename: Tallal C
authors.initials: TC
authors.lastname: Mamisch
authors.forename: Andrzej
authors.initials: A
authors.lastname: Materka
authors.forename: Michael
authors.initials: M
authors.lastname: Weber
authors.forename: Karem
authors.initials: K
authors.lastname: El-Rabadi
authors.forename: Klaus M
authors.initials: KM
authors.lastname: Friedrich
authors.forename: Albert
authors.initials: A
authors.lastname: Dirisamer
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
mesh_terms: D000328:Adult; D003287:Contrast Media; D005240:Feasibility Studies; D005260:Female; D005682:Gadolinium; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008592:Menisci, Tibial / Q000000981:diagnostic imaging* / Q000473:pathology; D011877:Radionuclide Imaging; D015203:Reproducibility of Results; D013223:Statistics as Topic; D013997:Time Factors; D055815:Young Adult
chemical_list: D003287:Contrast Media; D005682:Gadolinium