title: Feasibility of MR elastography of the intervertebral disc.
abstract: Low back pain (LBP) is a costly and widely prevalent health disorder in the U.S. One of the most common causes of LBP is degenerative disc disease (DDD). There are many imaging techniques to characterize disc degeneration; however, there is no way to directly assess the material properties of the intervertebral disc (IVD) within the intact spine. Magnetic resonance elastography (MRE) is an MRI-based technique for non-invasively mapping the mechanical properties of tissues in vivo. The purpose of this study was to investigate the feasibility of using MRE to detect shear wave propagation in and determine the shear stiffness of an axial cross-section of an ex vivo baboon IVD, and compare with shear displacements from a finite element model of an IVD motion segment in response to harmonic shear vibration. MRE was performed on two baboon lumbar spine motion segments (L3-L4) with the posterior elements removed at a range of frequencies (1000-1500Hz) using a standard clinical 1.5T MR scanner. Propagating waves were visualized in an axial cross-section of the baboon IVDs in all three motion-encoding directions, which resembled wave patterns predicted using finite element modeling. The baboon nucleus pulposus showed an average shear stiffness of 79±15kPa at 1000Hz. These results suggest that MRE is capable of visualizing shear wave propagation in the IVD, assessing the stiffness of the nucleus of the IVD, and can differentiate the nucleus and annulus regions.
authors.affiliation: Mayo Graduate School, Biomedical Engineering and Physiology Track, Mayo Clinic, Rochester, Minnesota, USA. Electronic address: BenAbraham.Ephraim@mayo.edu.
authors.forename: Ephraim I
authors.initials: EI
authors.lastname: Ben-Abraham
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA. Electronic address: Chen.Jun@mayo.edu.
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA. Electronic address: jpfelmlee@mayo.edu.
authors.forename: Joel P
authors.initials: JP
authors.lastname: Felmlee
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA. Electronic address: rossman.phillip@mayo.edu.
authors.forename: Phil
authors.initials: P
authors.lastname: Rossman
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA. Electronic address: manduca.armando@mayo.edu.
authors.forename: Armando
authors.initials: A
authors.lastname: Manduca
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA. Electronic address: an.kainan@mayo.edu.
authors.forename: Kai-Nan
authors.initials: KN
authors.lastname: An
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA. Electronic address: ehman.richard@mayo.edu.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Ehman
mesh_terms: D000818:Animals; D054459:Elasticity Imaging Techniques / Q000379:methods*; D020342:Finite Element Analysis; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging* / Q000473:pathology; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging* / Q000473:pathology; D017116:Low Back Pain; D008159:Lumbar Vertebrae / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009038:Motion; D010215:Papio; D011312:Pressure; D014732:Vibration
keywords: Baboon; Disc degeneration; Finite element; Intervertebral disc; Magnetic resonance elastography; Shear stiffness