MR Imaging and T2 Mapping of Femoral Cartilage
In Vivo Determination of the Magic Angle Effect
Timothy J. Mosher1,
Harvey Smith1,
Bernard J. Dardzinski2,3,
Vincent J. Schmithorst2 and
Michael B. Smith1,4
1
Department of Radiology—MC H066, Center for Nuclear Magnetic Resonance
Research, M108 NMR Building, M.S. Hershey Medical Center, Pennsylvania State
University College of Medicine, 500 University Dr., Hershey, PA 17033.
2
Imaging Research Center, The Children's Hospital Research Foundation,
Children's Hospital Medical Center, Cincinnati, OH 45229.
3
Departments of Radiology and Pediatrics, University of Cincinnati College of
Medicine, 3333 Burnet Ave., Cincinnati, OH 45229.
4
Department of Cellular and Molecular Physiology, Pennsylvania State University
College of Medicine, Hershey, PA 17033.
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Fig. 1A. —Sample MR images obtained from asymptomatic 23-year-old man.
T2-weighted source image shows uniform signal intensity in posterior femoral
condyle (arrow) without hypointense striations of radial zone
observed in weight-bearing cartilage (arrowhead).
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Fig. 1B. —Sample MR images obtained from asymptomatic 23-year-old man.
Calculated magnitude map shows uniform intensity in posterior femoral condyle
(arrow).
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Fig. 1C. —Sample MR images obtained from asymptomatic 23-year-old man.
Calculated T2 map shows longer T2 values in superficial layers of posterior
femoral condyle (arrow) oriented 55° relative to
B0.
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Fig. 2. —Three-dimensional plot of cartilage T2 as function of
normalized distance and orientation to B0. For all orientations,
cartilage T2 values are long near bone—cartilage interface and decrease
to minimum near normalized distance of 0.2-0.4. Cartilage T2 then increases
toward articular surface. At all normalized distances, cartilage T2 is longest
when oriented 55°. Greatest variation in cartilage T2 as a function of
orientation is in superficial 20% of cartilage (normalized distance =
0.8-1.0).
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Fig. 3. —Graph showing percent change in cartilage T2 (relative to
0°) as a function of orientation to B0. Greatest variation in
T2 is observed in superficial cartilage (dashed line, normalized
distance [ND] = 0.9). Least variation in cartilage T2 occurs in the radial
zone (solid line, ND = 0.3). Dotted line represents 0.6 ND.
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Fig. 4. —Drawing of cross-sectional structure of articular cartilage
illustrating orientation of collagen fibers. In radial zone of cartilage
collagen fibers are preferentially arranged perpendicular to the subchondral
bone surface. Anisotropic arrangement of collagen fibers in radial zone forms
theoretical basis for the magic angle effect in articular cartilage.
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Copyright © 2001 by the American Roentgen Ray Society.
