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.
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.
Mayerhoefer
Marius E
ME
Department of Radiology, MR Center, Medical University of Vienna, Vienna, Austria. marius.mayerhoefer@meduniwien.ac.at
Welsch
Goetz H
GH
Riegler
Georg
G
Mamisch
Tallal C
TC
Materka
Andrzej
A
Weber
Michael
M
El-Rabadi
Karem
K
Friedrich
Klaus M
KM
Dirisamer
Albert
A
Trattnig
Siegfried
S
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
D003287:Contrast Media; D005682:Gadolinium