Brain T1 intensity changes after levodopa administration in healthy subjects: a voxel-based morphometry study.

Aim: To test T1 intensity variations induced by levodopa administration in the regional fixation area in the human brain.

Method: Using non-invasive magnetic resonance imaging (MRI) technique [T1-weighted sequence MPRAGE; TE/TR/TI = 5/25/800 ms; impulsion angle = 15 degrees; field of view = 256 x 230 x 180 mm3; acquisition matrix = 256 x 192 x 104; reconstruction matrix = 256 x 256 x 128), we tested changes in the T1 MRI signal intensity resulting in changes in the grey matter automatic classification after administration of a single dose of 100 mg of levodopa by a voxel-based morphometry method (VBM) in 12 healthy subjects.

Results: The VBM analysis demonstrated an increased number of voxels attributed to grey matter after levodopa administration in an anatomical cluster which included substantia nigra, tegmental ventral area and subthalamic nucleus bilaterally, the principal origin and first relay nuclei of projections in brain dopaminergic systems (t = 8.61; corrected for all grey matter volume P < 0.001).

Conclusion: Our results suggest that levodopa administration could induce an MRI T1 signal intensity variation that is not evident to the naked eye, but is detectable by measuring local signal intensities. Possible clinical applications are discussed.