Functional Identification Of The Primary Motor Area By Diffusion Tensor Imaging

Objective: To explore the usefulness of diffusion tensor imaging (DTI) in quick and stable identification of the primary motor area (PMA).Methods:Twenty patients with deep-seated brain tumors, 9 males and 11 females, aged from 13 to 63 years (mean±SD, 37.5±14.0 years), participated in this study at the Department of Radiology, the First Affiliated Hospital of Nanchang University between April 2008 and August 2009. All imaging studies were performed on a 3.0T SIEMENS magnetic resonance system (Siemens, Erlangen, Germany).20 patients were underwent 3-dimensional T1-weighted imaging for anatomical reference; gradient-echo, echo-planar imaging (EPI) for functional magnetic resonance imaging (fMRI); and single-shot, diffusion-weighted EPI for diffusion tensor imaging (DTI). All of the fMRI, DTI data were processed and analyzed with the software provided by Siemens (Leonardo syngo 2008A, Siemens) work station. On the basis of anatomical knowledge, corticospinal tract (CST) was reconstructed by placing one region of interest (ROI) in the cerebral peduncle of the midbrain and the other ROI in the ventral of the pons. Tracking stops at predefined thresholds of FA and turning angle to limit the detection of spurious fibers. We chose a FA threshold of 0.2 and a turning angle threshold of 60°. Motor activation signals were acquired by fMRI with hand clenching block active mode. Two techniques were compared to determine the accuracy for cortical mapping of PMA with CST in the 3D anatomic illustrations which fused the CST results and the fMRI activation signals.Results : All of the patients completed the fMRI motor activation task successfully. Significant functional activation areas were observed in the PMA of all 20 subjects. fMRI activation signals were distributed mainly in the contralateral central sulcus around the omega shape hand-knob. Three dimensional reconstructions showed that PMA activations were located mainly on the middle portion of precentral gyrus. The motor tracts (CST) consistently propagated from the pons and cerebral peduncle to the suspected PMA location. CST was located before the fMRI activation signals in the 3D anatomic illustrations which combined the CST results and the fMRI activation signals. Partial fibers may be related to hand movement were located inside of the fMRI activation signals and the other fibers were located in the medial of the precentral gyrus on the coronal view. There is a good correlation between CST and fMRI activation signals in identifying PMA.Conclusion: DTI enables identification of the PMA . Identifying PMA by CST is of great importance in the patients who present with paralysis and the children who could not cooperation.