Voxel‐based analysis of R2* maps in the healthy human brain

Abstract

Purpose: To develop a voxel-based analysis of an R2* map of healthy human brain that is automatic, reproducible, and realizable in a single examination on a 3T MR imager. Such a tool could be useful to measure iron accumulation in neurodegenerative diseases. Materials and Methods:In all, 18 healthy subjects underwent MR imaging at a field strength of 3T: 1) six consecutive T2*-weighted gradient-echo volumes were acquired using a segmented echo-planar imaging sequence and 2) a conventional dual-echo turbo spin echo sequence was also applied to acquire T2-weighted images. Images were realigned and spatial correction was performed using a template brain dataset with SPM2. For each subject we performed a voxelby-voxel nonlinear least-squares fitting of the data acquired at the six echo times to obtain a monoexponential signal decay curve. The reproducibility and sensitivity to age variation were assessed by voxel-based analysis. Results:The reproducibility tests in whole brain analysis showed little R2* variation. Furthermore, the statistical analysis, performed on each brain voxel, revealed a significant positive correlation between age and MR values located in regions where a slow and constant age-related iron deposition is known. Conclusion:Our method, combining data acquisition and data processing, demonstrates the feasibility of voxel-based analysis on an R2* map and affords a high degree of sensitivity and good reproducibility while maintaining high spatial resolution.

Differentiating maturational and aging-related changes of the cerebral cortex by use of thickness and signal intensity

“…Elevated iron concentrations have been observed in normal aging (Stankiewicz et al, 2007) and may contribute to myelin susceptibility (Bartzokis, 2004). Protracted maturational T2 alterations may persist into the third decade of life (Hassink et al, 1992) and quantitative relaxation studies have shown age-related alterations in T2 and T2* relaxation (Bartzokis et al, 1997;Bartzokis et al, 2004;Péran et al, 2007;Siemonsen et al, 2008). Our analyses showed that although cortical GM R2* showed strong age-related variability, including R2* in the statistical models only to a minor extent influenced estimated age effects on intracortical GM MP-RAGE signal intensity.…”

Differentiation of Typical and Atypical Parkinson Syndromes by Quantitative MR Imaging

“…TE range and resolution were chosen similar to those in established protocols at 3T. 9 For R2-mapping, a multi-spin-echo sequence was used with a 1.7-mm in-plane resolution and a 3.4-mm section thickness. Only even echoes were evaluated (at TE ϭ 30, 60, 90, 120, and 150 ms, TR ϭ 4500 ms) because these are not contaminated by stimulated echo signals.…”

A Potential Biomarker in Amyotrophic Lateral Sclerosis: Can Assessment of Brain Iron Deposition with SWI and Corticospinal Tract Degeneration with DTI Help?

“…[8][9][10][11][12][13][14] Recent studies advocated SWI as a potential in vivo marker to detect susceptibility changes among tissues, which aids in the identification of paramagnetic nonheme iron (ferritin and transferrin), which would appear hyperintense on filtered phase images. [15][16][17][18] These finding opened a new window to estimate the regional changes in iron content associated with ALS.…”