Functional imaging studies of cognition using 99mTc-HMPAO SPECT: empirical validation using the N-back working memory paradigm
Purpose Functional activation protocols are widely applied for the study of brain-cognition relations. Only few take advantage of the intrinsic characteristics of SPECT, particularly those allowing cognitive assessment outside of the camera, in settings close to the standard clinical or laboratory ones. The purpose of the study was to assess the feasibility of a split-dose activation protocol with 99mTc-HMPAO using low irradiation dose.
Materials and methods A two-scans protocol was applied to 12 healthy young volunteers using 270 MBq of 99mTc-HMPAO per scan, with each image associated to a particular experimental condition of the verbal n-back working memory task (0-back, 2-back). Subtraction method was used to identify regional brain activity related to the task.
Results Voxel-wise statistical analysis showed left lateralized activity associated with the 2-back task, compared to the 0-back task. Activated regions, mainly prefrontal and parietal, were similar to those observed in previous fMRI and 15O-PET studies.
Conclusion The results support the use of 99mTc-HMPAO SPECT for the investigation of brain-cognition relations and demonstrate the feasibility of optimal quality images despite low radiopharmaceutical doses. The findings also acknowledge the use of HMPAO as a radioligand to capture neuro-energetic modulations linked to cognitive activity. They encourage extending the application of the described activation protocol to clinical populations.
Ludwig, C., Chicherio, C., Terraneo, L., Slosman, D. O., & de Ribaupierre, A. (2008). The use of 99mTc-HMPAO SPECT in activation studies: Empirical validation using the n-back working memory task. European Journal of Nuclear Medicine and Molecular Imaging, 35, 4, 695-703.