Decreased brain stiffness in Alzheimer's disease determined by magnetic resonance elastography

Abstract

Purpose To test patient acceptance and reproducibility of the 3D MRE brain exam using a soft vibration source, and to determine if MRE could noninvasively measure a change in the elastic properties of the brain parenchyma due to Alzheimer's disease (AD). Materials and Methods MRE exams were performed using an accelerated spin-echo EPI pulse sequence and stiffness was calculated with a 3D direct inversion algorithm. Reproducibility of the technique was assessed in 10 male volunteers, who each underwent 4 MRE exams separated into 2 imaging sessions. The effect of Alzheimer's disease on brain stiffness was assessed in 28 volunteers, 7 with probable AD, 14 age- and gender-matched PIB-negative (Pittsburgh Compound B, a PET amyloid imaging ligand) cognitively normal controls (CN-), and 7 age- and gender-matched PIB-positive cognitively normal controls (CN+). Results The median stiffness of the 10 volunteers was 3.07 kPa with a range of 0.40 kPa. The median and maximum coefficients of variation for these volunteers were 1.71% and 3.07%. The median stiffness of the 14 CN- subjects was 2.37 kPa (0.44 kPa range) compared to 2.32 kPa (0.49 kPa range) within the CN+ group and 2.20 kPa (0.33 kPa range) within the AD group. A significant difference was found between the 3 groups (p=0.0055, Kruskal-Wallis one-way analysis of variance). Both the CN+ and CN- groups were significantly different from the AD group. Conclusion 3D MRE of the brain can be performed reproducibly and demonstrates significantly reduced brain tissue stiffness in patients with AD.

Multiresolution MR elastography using nonlinear inversion

“…A moderate reduction in estimated mechanical property resolution will reduce the visibility of small scale mechanical property variations; however, many of the clinical MRE results reported to date have used a spatial average of mechanical properties taken over large regions. 2,5,17,31 A moderate reduction in the property resolution will not have a large effect on these types of measurements.…”

“…Images of the storage modulus, Re{μ}, have been found to be the most successful indicators of disease to date, with promising in vivo results having been reported for breast, 9,15 liver, 2,16 and brain. 17,18 Estimation of alternative mechanical parameters is also possible. For example, estimates of the loss modulus, Im{μ}, improved the specificity of breast cancer diagnosis, 4,19 and contrast has been observed in normal pressure hydrocephalus; 5 however, the loss modulus has been less successful in other applications.…”

Tissue mechanics regulate brain development, homeostasis and disease

“…The ECM composition is changed in the brains of individuals with Alzheimer's disease (Lau et al, 2013), and such changes can either directly or indirectly lead to synaptic and neural loss (BonnehBarkay and Wiley, 2009), which could be due to a loss of matrix molecules that are necessary to maintain the progenitor cell niches. Regional changes in brain stiffness in individuals with Alzheimer's disease have also been documented , and in this context, the overall decrease in stiffness, as measured by performing three-dimensional magnetic resonance elastography, could serve as a noninvasive diagnostic tool (Murphy et al, 2011).…”

Monitoring Cartilage Tissue Engineering Using Magnetic Resonance Spectroscopy, Imaging, and Elastography

“…[117][118][119] In these soft tissues, the macroscopic mechanical behavior (stiffness) has highly correlated changes in the tissue composition and structure identified by histology on a microscopic scale. Therefore, it is reasonable to expect that changes in the structure and composition of engineered cartilage during growth will alter the MRE-derived stiffness.…”