DISCREPANCIES BETWEEN HMPAO AND ECD SPECT IMAGING IN BRAIN-TUMORS

Among several brain radiopharmaceuticals for SPECT imaging, Tc-99m com plexes of HMPAO and ECD are the most widely used. They are considered to be equal in their capacity to reflect regional cerebral blood flow; but discrepancies between HMPAO and ECD brain uptake have been report ed in stroke patients. This paper reports our observations regarding d iscrepancies between HMPAO and ECD SPECT in 14 of 23 patients with sus pected brain tumors or presumed metabolic cerebral abnormalities. We o btained similar conflicting results, namely focal HMPAO hyperactivitie s and isoactive ECD SPECT. The majority of these discrepancies were fo und in patients with brain tumors (10 of 13 patients), while only 4 of the 10 remaining patients with nontumoral process showed similar disc repant results. The physiopathology behind these observations is discu ssed here, and it is likely to be related to the specific response to cellular metabolic disorders rather than to perfusion disturbances.