AbstractID: 8047 Title: Investigation of the Sources of Tendon Orientation Dependence
in MRI
We first reported in 1985 the need for radiologists to be aware of the strong orientational
variation in the T2 relaxation time of tendon and other collagen rich tissues. Specifically
the increase of visible signal at the magic angle 54.5 degrees relative to the magnetic field
is easily confused with tears in tendons or ligaments caused by traumatic joint injury.
The molecular basis of orientational dependence is related to motional anisotropy of
water molecule motion adjacent to the protein surface but the details of the multiple
component T2 relaxation were difficult to explain. This study uses an NMR study of
tendon with a titration of water on the protein to demonstrate that water is highly
structured in six chains of water arranged in hexagonal symmetry in each of the three
channels between the a-chains that form the triple helix of the procollagen molecule. At
the magic angle the three water chains inside the cleft relax with a T2 ~ 4 msec due to the
confined mobility while the three outward facing water molecules have a long relaxation
time T2 ~ 20 msec due to greater mobility. The proposed hydration model explains all
the known features of water on natural collagen and may have wider application in
understanding this the behavior of collagen rich tissues.