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 voxel‐by‐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. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.