High-resolution T2 imaging
of AC is able to quantitatively measure depth-dependent features of articular
cartilage (AC). When the cartilage articular surface (AS) is oriented normal
(0°) to the external magnetic field, healthy AC takes on a laminar appearance
that indicates the superficial zone (SZ), transitional zone (TZ), and radial
zone (RZ), where collagen fibers are oriented parallel, random, and
perpendicular to the AS [1]. When the AS is oriented at the magic angle (55°),
the nuclear dipolar interaction is minimized and the tissue appears
homogeneous. Compression of AC has effects that change many zonal properties [2,3],
and hypertrophy may alter the biomechanical function and depth-dependent
collagen ultra-structure of AC.
