THE USE OF A REALISTIC HEAD BRAIN PHANTOM FOR CALIBRATION OF ACTIVITYCONCENTRATION MEASUREMENTS WITH SPECT

A realistic head/brain phantom was used to check the quantification of activity concentrations resulting from SPECT reconstructions using fi ltered back-projection. The phantom consisted of a hollow brain cast, fillable with fluid and embedded in a human skull. It was filled with saline solutions with different activity concentrations of Tc-99m. The salt density was varied to test the influence of different absorption coefficients within the brain. Activity concentrations were calculate d within 48 computer-generated ROIs on the reconstructed SPECT slices. The mean activity concentration was correct within +/- 5% when an abs orption coefficient was applied, which was correlated to the absorptio n measured by transmission of an external source through the middle of the phantom. The relative standard deviation of measured activities o f all 48 ROIs was of the order of 10%. The results show that a homogen eous activity concentration in brain can be quantified accurately with SPECT.