Correlation of laminated MR appearance of articular cartilage with histology, ascertained by artificial landmarks on the cartilage

The object of this study was to correlate the laminae of articular cartilag e on magnetic resonance (MR) imaging with histologic layers. T1- and fast s pin-echo T2-weighted images of articular cartilage with artificial landmark s were obtained under high gradient echo strength (25 mT/m) conditions and a voxel size of 78 x 156 x 2000 mu m. Images were also obtained with a) cha nged frequency-encoding directions; b) changed readout gradient strength; a nd c) a varied number of phase-encoding steps. T2 mapping was performed wit h angular variations. Artificial landmarks allowed accurate comparison betw een the laminae on MR images and the histologic zones. No alterations of th e laminae were noted by changing the frequency gradient direction. Altering readout gradient strengths did not show a difference in the thickness of t he laminae, and increasing the phase-encoding steps resulted in a more dist inct laminated appearance, ruling out chemical shift, susceptibility, and t runcation artifacts. The T2 mapping profile showed an anisotropic angular d ependency from the magic angle effect. In conclusion, the laminated appeara nce of articular cartilage on spin-echo and fast spin-echo MR images correl ated with the histologic zones rather than MR artifacts. J. Magn. Reson. Im aging 1999:10:57-64. (C) 1999 Wiley-Liss, Inc.