Thalamic glucose metabolism matched with ultra high resolution anatomy and tractography obtained by PET-MRI fusion imaging

Objectives The functional roles and anatomy of the thalamus are known. The metabolic activities and fiber connectivities are, however, not clearly shown in human yet. The purpose of present study is to identify each thalamic nucleus, its connectivity, and measure its corresponding glucose metabolism.

Methods A healthy volunteer was recruited. A bolus injection of [F18]FDG(185MBq) was given to the subject. Then, FDG uptake was simultaneously performed in the 7.0T MRI with 3D MPRAGE imaging. After the transport of the subject to the HRRT-PET by the shuttle bed, PET scanning was conducted for 30 minutes. After scanning, the PET and the MR images were automatically integrated by the fusion system. By additional image scanning and processing with DTI imaging, a tractography image was obtained to show the fiber connectivity in the thalamus.

Results The 7.0T MRI image clearly showed most of the thalamic nuclei: PUL, VL, VA, CM, AN, and MD. The ROIs of the thalamic nuclei were drawn from the 7.0T MR image and were used for PET-MRI fusion image which enabled us to measure the glucose metabolism of the corresponding nuclei from the PET images. Among the nuclei, MD showed the highest glucose uptake among the thalamic nuclei. At the right, the corresponding tractography image is added to show the fiber distribution in the central thalamic area.

Conclusions The PET-MRI fusion image enabled us to indentify each thalamic nucleus, its corresponding metabolism, and nerve fiber connectivity. Functional metabolic images and fiber connectivity will be important information to the function and disease mechanisms of thalamus such as schizophrenia, epilepsy, and pain.

Research Support The research was supported by the Converging Research Center Program through the Ministry of Education, Science and Technology (2010K001096). Authors would like to thank Dr. Calamante, Univ. of Melbourne for DTI images provided to us