title: Transient and microscale deformations and strains measured under exogenous loading by noninvasive magnetic resonance.
abstract: Characterization of spatiotemporal deformation dynamics and material properties requires non-destructive methods to visualize mechanics of materials and biological tissues. Displacement-encoded magnetic resonance imaging (MRI) has emerged as a noninvasive and non-destructive technique used to quantify deformation and strains. However, the techniques are not yet applicable to a broad range of materials and load-bearing tissues. In this paper, we visualize transient and internal material deformation through the novel synchrony of external mechanical loading with rapid displacement-encoded MRI. We achieved deformation measurements in silicone gel materials with a spatial resolution of 100 µm and a temporal resolution (of 2.25 ms), set by the repetition time (TR) of the rapid MRI acquisition. Displacement and strain precisions after smoothing were 11 µm and 0.1%, respectively, approaching cellular length scales. Short (1/2 TR) echo times enabled visualization of in situ deformation in a human tibiofemoral joint, inclusive of multiple variable T(2) biomaterials. Moreover, the MRI acquisitions achieved a fivefold improvement in imaging time over previous technology, setting the stage for mechanical imaging in vivo. Our results provide a general approach for noninvasive and non-destructive measurement, at high spatial and temporal resolution, of the dynamic mechanical response of a broad range of load-bearing materials and biological tissues.
authors.affiliation: Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Deva D
authors.initials: DD
authors.lastname: Chan
authors.forename: Corey P
authors.initials: CP
authors.lastname: Neu
mesh_terms: D000369:Aged, 80 and over; D002102:Cadaver; D002358:Cartilage, Articular / Q000503:physiopathology*; D019245:Compressive Strength; D004548:Elasticity; D005260:Female; D005269:Femur / Q000503:physiopathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007719:Knee Joint / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D012828:Silicones / Q000737:chemistry; D013314:Stress, Mechanical; D013977:Tibia / Q000503:physiopathology*; D016474:Weight-Bearing / Q000502:physiology*
chemical_list: D012828:Silicones