title: Assessing the multiscale architecture of muscular tissue with Q-space magnetic resonance imaging: Review.
abstract: Contraction of muscular tissue requires the synchronized shortening of myofibers arrayed in complex geometrical patterns. Imaging such myofiber patterns with diffusion-weighted MRI reveals architectural ensembles that underlie force generation at the organ scale. Restricted proton diffusion is a stochastic process resulting from random translational motion that may be used to probe the directionality of myofibers in whole tissue. During diffusion-weighted MRI, magnetic field gradients are applied to determine the directional dependence of proton diffusion through the analysis of a diffusional probability distribution function (PDF). The directions of principal (maximal) diffusion within the PDF are associated with similarly aligned diffusion maxima in adjacent voxels to derive multivoxel tracts. Diffusion-weighted MRI with tractography thus constitutes a multiscale method for depicting patterns of cellular organization within biological tissues. We provide in this review, details of the method by which generalized Q-space imaging is used to interrogate multidimensional diffusion space, and thereby to infer the organization of muscular tissue. Q-space imaging derives the lowest possible angular separation of diffusion maxima by optimizing the conditions by which magnetic field gradients are applied to a given tissue. To illustrate, we present the methods and applications associated with Q-space imaging of the multiscale myoarchitecture associated with the human and rodent tongues. These representations emphasize the intricate and continuous nature of muscle fiber organization and suggest a method to depict structural "blueprints" for skeletal and cardiac muscle tissue.
authors.affiliation: Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA, 02115, USA.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Hoffman
authors.affiliation: Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA, 02115, USA.
authors.forename: Erik N
authors.initials: EN
authors.lastname: Taylor
authors.affiliation: Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA, 02115, USA.
authors.forename: George E
authors.initials: GE
authors.lastname: Aninwene
authors.affiliation: Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University of Chicago, Maywood, IL, 60153, USA.
authors.forename: Sakthivel
authors.initials: S
authors.lastname: Sadayappan
authors.affiliation: Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA, 02115, USA.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Gilbert
mesh_terms: D000818:Animals; D038524:Diffusion Magnetic Resonance Imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D018485:Muscle Fibers, Skeletal; D009206:Myocardium; D012377:Rodentia; D014059:Tongue / Q000033:anatomy & histology*
keywords: Q-space imaging; diffusion weighted MRI; myoarchitecture