VALIDATION OF THE 3-DIMENSIONAL ACQUISITION MODE IN POSITRON-EMISSION-TOMOGRAPHY FOR THE QUANTITATION OF [F-18] FLUORO-DOPA UPTAKE IN THE HUMAN STRIATA

Three-dimensional (3D) positron emission tomography (PET) is attractiv e for [F-18]fluoro-DOPA studies, since the sensitivity improvement is maximal for radioactive sources located in central planes, which is us ually the case for the human striata. However, the image quantitation in that mode must be assessed because of the nearly threefold increase in scattered coincidences. We report the results of [F-18]fluoro-DOPA studies performed on six normal volunteers. Each one was scanned in t he 3D and two-dimensional (2D) modes on the same tomograph. The quanti tation in the 3D and 2D modes was compared for a Patlak graphical anal ysis with the occipital counts as the input function (Ki) and a striat ooccipital ratio analysis. We find that, in 3D PET, a scatter correcti on is required to preserve the same quantitation as in 2D PET. When th e 3D data sets are corrected for scatter, the quantitation of the [F-1 8]fluoro-DOPA uptake, using the Patlak analysis, is similar in the 2D and 3D acquisition modes. Conversely, analysis of the striatooccipital ratio leads to higher values in 3D PET because of a better in-plane r esolution. Finally, using the 3D mode, the dose injected to the subjec ts can be reduced by a factor greater than 1.5 without any loss in acc uracy compared to the 2D mode.