The vertebral trabecular model revisited: magnetic field distribution in the vicinity of osseous disconnections.
In the current paper a vertebral bone model is introduced that can be used for studying trabecular thinning and the formation of trabecular disconnections. Magnetostatic simulations are applied in MR-osteodensitometry to deduce the quality of trabecular bone from experimentally obtained susceptibility effects. The course of trabecular bone loss, which results in distinct interruptions and consequently severe mechanical impairment, is not assessable in the majority of such applied models. In the novel approach introduced here, analytical solutions of prolate ellipsoids were used to compute the disturbed magnetic fields within the proposed 3D model. The performed simulations focused on two variants of the vertebral model: an intact model and a pathological model accounting for microdamage. For both variants, magnetic resonance spectra were simulated for different bone volume fractions. Subsequently, resonance signals were obtained from the Fourier transform of the distribution with respect to time. The resonance time courses were analyzed through common signal models to estimate the relaxation time [Formula: see text] of the corresponding free induction decay. Detailed computations revealed the significant contribution of the microdamage to the susceptibility effect. Further, when comparing the line broadening effect between the intact and disrupted models a contradictory outcome was found. The damaged osseous network for the lower bone fraction resulted in faster decay of the transverse magnetization. In conclusion, a significant contribution of trabecular disconnections to the susceptibility effect has been shown by the presented model. Future dedicated MRI experiments can explore the use of this effect to assess the integrity of cancellous bone.
Graz University of Technology, Institute for Medical Engineering, Stremayrgasse 16/3, 8010 Graz, Austria.
Markus
M
Kraiger
Bernhard
B
Schnizer
Rudolf
R
Stollberger
D000465:Algorithms; D015519:Bone Density; D001842:Bone and Bones / Q000033:anatomy & histology*; D003198:Computer Simulation; D005583:Fourier Analysis; D006801:Humans; D008159:Lumbar Vertebrae / Q000033:anatomy & histology*; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods; D008962:Models, Theoretical