SPECTROSCOPY, IMAGING, OTHER TECHNIQUES |
Mapping complex myoarchitecture in the bovine tongue with diffusion spectrum magnetic resonance imaging
Richard J. Gilbert 1*, Lee H Magnusson 1, Vitaly J. Napadow 2, Thomas Benner 2, Ruopeng Wang 2 and Van J. Wedeen 2
1 Massachusetts Institute of Technology
2 Massachusetts General Hospital
* To whom correspondence should be addressed. E-mail: rgilbert{at}mit.edu.
Submitted on June 13, 2005
Revised on September 29, 2005
Accepted on 17 March 2006
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Abstract |
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The ability to resolve complex myofiber populations is important for relating architectural structure with mechanical function in muscular tissues. To address this issue for the case of the tongue, we employed Diffusion Spectrum Imaging (DSI), an MRI method for determining fiber alignment within anatomical regions comprised of myofiber populations with multiple orientations. By specifically varying gradient field strength, molecular displacement in a tissue can be determined by Fourier transforming the echo intensity against gradient strength at fixed gradient pulse spacing. The displacement profiles are visualized by graphing 3D isocontour icons for each voxel, with the isocontour shape and size representing the magnitude and direction of the constituting fiber populations. To validate this method, we simulated diffusive motion and a DSI experiment within the constraints of crossing fibers, and determined that DSI accurately depicts arbitrary angular relationships between crossing fibers. Considering the fiber relationships existing in the whole bovine tongue, we compared the images obtained by DSI with those obtained by DTI in an anterior slice of the lingual core, a region known to possess extensive fiber crossing. Distinct fiber population heterogeneity exists in the anterior core region of the bovine tongue. In contrast to DTI, which depicts the anterior core solely as a region with mixed fiber populations, i.e. low anisotropy, DSI shows 2 distinct fiber populations, with an explicit orthogonal relationship to each other. In imaging the whole lingual tissue, we discerned arrays of crossing and non-crossing fibers involving the intrinsic and extrinsic muscles, which merged at interface regions. We conclude that DSI has the capacity to determine 3D fiber orientation in complex myoarchitectural regions of muscular tissues.
Key Words:
diffusion imaging, lingual muscle, magnetic resonance imaging, tongue mechanics
