[Quantitative brain SPECT imaging with scatter and attenuation compensation: comparison of sequential and simultaneous acquisition of transmission and emission data].

Scatter and attenuation correction for brain SPECT of a phantom and a normal volunteer was performed using the Triple Energy Window method combined with a transmission scan. 99mTc-ECD and 99mTc solution were used as an emission tracer and a transmission source, respectively. We employed a triple-headed SPECT gammacamera system equipped with fan-beam collimators for acquisition with line transmission sources placed at the focal lines of the fanbeam collimators. Two mode, sequential mode and simultaneous mode, of data acquisition protocols were examined. In the sequential mode, a transmission scan was carried out using three external sources for the brain phantom without emission tracer. After removing all sources, an emission scan was performed on the brain phantom containing the tracer. In the simultaneous mode, the injection was followed by a simultaneous transmission-emission scan using one transmission source. The same study was conducted out for the normal volunteer, after confirming the effectiveness of these protocols with phantom studies. Corrected SPECT count values obtained with two protocols were almost identical. Simultaneous mode had advantages in avoiding misalignment between transmission and emission data and in shorter acquisition time than sequential mode.