Combined Use of Two Tracers for Brain Blood Flow Scanning in Dementia and Stroke
MetadataShow full item record
Brain blood flow imaging using single photon emission computed tomography (SPECT) is currently being utilized for the differential diagnosis of dementia and stroke. There are two tracers, Tc-99m-hexamethylpropyleneamine oxime (HM-PAO) and 1-123- isopropylamphetamine (IMP), which are commercially available for use in SPECT brain scans. These tracers produce grossly similar images which are blood flow dominated yet have different, though not completely understood, mechanisms of uptake. A study was undertaken to determine if the differences in the mechanisms of uptake manifest themselves in different images produced in the same patient. This could possibly reveal disease states where the use of one tracer would be more appropriate. A formula was generated which will correct for the overlap of the energy emissions of the two tracers. The counts at each pixel were computer corrected, by this formula, to produce "pure" images from each tracer. Patients were scanned using both tracers, injected within a minute of each other to eliminate any variability in the scan due to a change in the environment or thoughts of the patient. This produced two SPECT brain scans, of the same patient, in which the only variable was the tracer used. More patients are needed before any statistically significant statements about the tracers can be made, but dramatic differences in the images from the two tracers are already apparent through patients scanned with this technique.