Co-registration of PET and MRI in different courses of MS using Cobalt-55 as a Calcium-tracer.

Multiple Sclerosis (MS) is an auto-immune central nervous system (CNS) inflammation. At this moment, MRI is the most accurate paraclinical test in MS to monitor disease activity, although poorly correlated with clinical impairment. PET using Co-55 as a Ca-tracer may visualize Co-transport across the neuronal membrane, Ca-mediated inflammatory processes and passive leakage through a breach in the blood-brain barrier. Co-registration of MRI and Co-PET may actually allow identification of clinically active lesions. MRI and Co-PET were performed as described elsewhere. Based on a statistic parametric mapping (SPM-96)-software package, MRI and Co-PET were superimposed. A semi-automated technique was used to count the MS-lesions. We included four groups of eight MS-patients with relapsing-remitting (RR), primary progressive (PP), progressive relapsing (PR) and secondary progressive (SP) courses and eight healthy volunteers. MS was assessed in terms of impairment using Kurtzke's Expanded Disability Status Scale (EDSS) and Scripps Neurological Rating Scale (NRS). Co-PET displayed focal uptake throughout the MS brain, both in the grey and white matter. All four patients groups (as compared to controls) demonstrated a more inhomogeneous distribution of Co-spots with a tendency to show clustering, most evident in RR-MS. SPM-analysis revealed an essentially different distribution pattern of MS spots on MRI and Co-PET. (Merging of) Co-PET and MRI may eventually form complementary tools for identifying clinically relevant lesions, thus providing a more reliable secondary outcome measure in MS.