Towards an Elastographic Atlas of Brain Anatomy

Abstract

Cerebral viscoelastic constants can be measured in a noninvasive, image-based way by magnetic resonance elastography (MRE) for the detection of neurological disorders. However, MRE brain maps of viscoelastic constants are still limited by low spatial resolution. Here we introduce three-dimensional multifrequency MRE of the brain combined with a novel reconstruction algorithm based on a model-free multifrequency inversion for calculating spatially resolved viscoelastic parameter maps of the human brain corresponding to the dynamic range of shear oscillations between 30 and 60 Hz. Maps of two viscoelastic parameters, the magnitude and the phase angle of the complex shear modulus, |G*| and φ, were obtained and normalized to group templates of 23 healthy volunteers in the age range of 22 to 72 years. This atlas of the anatomy of brain mechanics reveals a significant contrast in the stiffness parameter |G*| between different anatomical regions such as white matter (WM; 1.252±0.260 kPa), the corpus callosum genu (CCG; 1.104±0.280 kPa), the thalamus (TH; 1.058±0.208 kPa) and the head of the caudate nucleus (HCN; 0.649±0.101 kPa). φ, which is sensitive to the lossy behavior of the tissue, was in the order of CCG (1.011±0.172), TH (1.037±0.173), CN (0.906±0.257) and WM (0.854±0.169). The proposed method provides the first normalized maps of brain viscoelasticity with anatomical details in subcortical regions and provides useful background data for clinical applications of cerebral MRE.

The predictive link between matrix and metastasis

“…Reports on the mechanical properties (stiffness) of brain tissue are primarily limited to elastography [38, 39], a technique not commonly performed on in vitro model systems. Obtaining human brain tissue for ex vivo mechanical testing is challenging, therefore indentation studies are limited to animal models, and report Young’s moduli ranging from 1–2 kPa in Young’s modulus [40].…”

In vivo high-resolution magnetic resonance elastography of the uterine corpus and cervix

“…Using this technique, highly resolved maps of the magnitude (|G * |) and the phase angle (φ) of the complex shear modulus were obtained in the liver and spleen [11,14], the kidney [14] and the brain [15]. |G * | combines both elasticity and viscosity and therefore relates to the haptic material properties; φ quantifies the degree of fluidity, i.e.…”

Phantom evaluations of nonlinear inversion MR elastography

“…[18, 28, 32, 56] In our study, the damping ratio inclusion phantom allowed us to evaluate spatial resolution in the estimated damping ratio images. This phantom indicated that the limit in damping ratio spatial resolution was 8mm using NLI.…”

“…[25] Recent work in brain MRE has moved toward measuring small, low contrast structures to improve sensitivity to local changes in the mechanical microstucture as a vehicle to detect specific diseases. [26–28]…”