(55)Cobalt (Co) as a PET-tracer in stroke, compared with blood flow, oxygen metabolism, blood volume and gadolinium-MRI

Several studies have shown the feasibility of divalent cobalt (Co)-isotopes (Co-55 and Co-57) in imaging of neuronal damage in stroke, multiple sclero sis, cerebral tumors and traumatic brain injury. Little is known how region al Co uptake relates to other pathophysiological changes after stroke. Ther efore, we compared Co-55-PET with functional parameters such as regional ce rebral blood dow (rCBF) using (CO2)-O-15, regional oxygen metabolism (rCMRO (2)) using O-15(2), regional cerebral bloodvolume (rCBV) and post-gadoliniu m (Gd) T(1)w-MRI to assess the permeability of the blood-brain-barrier (BBB ). Sixteen patients (10 female; six male) aged 43 to 84 (mean 69) years wit h first ever stroke, as shown by CT or MRI, were examined with Co-55-PET an d (CO2)-O-15-, O-15(2)- and (CO)-O-15-PET in one single session, in a perio d varying from 0 to 30 days after stroke-onset. Regions of infarction on (C O2)-O-15- and O-15(2)-PET (defined by rCMRO(2) <65% or rCBF<45% of the cont ralateral value) were subsequently superimposed on the Co-55-PET scan. Clin ical status was established using the Orgogozo stroke scale, which was asse ssed both at day 1 and at discharge (at least 6 weeks after day 1). Accumul ation of Co-55 was Seen in eight out of 16 patients, occurring in areas sho wing a diminished oxygen metabolism, was only partially related to blood fl ow, and was located mainly outside the extent of the infarction or luxury p erfusion as seen on post-Gd T(1)w-MRI. Statistical analysis showed a negati ve correlation between the Orgogozo score at discharge and the uptake of ra dioactive cobalt. (C) 1999 Elsevier Science B.V. All rights reserved.