Basal ganglia phantom simulation: improvement of relative quantitation in SPECT [I-123] dynamic neuroreceptor imaging

[I-123] labeled radiopharmaceuticals are being used to study neuroreceptor in monkey and human brain with a triple headed SPECT system. To optimize quantitative accuracies in monkey dynamic neuroreceptor studies, a combination of collimators (high-resolution fan-beam collimators (HRF), ultrahigh-resolution fan-beam collimators (UHRF)) with various filters including a Butterworth filtering, a count rate dependent 2-D Wiener (2-DW) prefiltering, 3-D Wiener postfiltering techniques (3-DW) has been studied. SPECT images of a monkey size cylindrical phantom containing two small vials representing regions of specific binding were acquired on a triple headed camera equipped with both HRF and UHRF. The vials were filled with a fixed concentration of [I-123] and the water in the cylinder around them were filled with three different concentrations to simulate the contrast between the basal ganglia (BG) and background (BKGD) for the representative early, middle, and late studies. The acquisition parameters were designed to simulate the dynamic neuroreceptor studies in monkey. The projection data were reconstructed with Butterworth 3.16, 2-DW, and 3-DW. The optimal threshold which yielded true volumes (5.36×2 ml) were found. The concentration ratios (BG/BKGD) were estimated as a function of threshold. The results indicate that the UHRF with 3-DW improves image quantitation in SPECT neuroreceptor imaging