Attenuation correction with low activity sources

The aim of this study was to test the influence of the source decay on the performance of the attenuation-corrected (AC) thallium-201 ((/sup 2/01)Tl) single photon emission tomography using a gadolinium-153 (/sup 153/Gd) line source. Three acquisitions were performed using the same line source during a period of 26 months. The activity of the source was 300 mCi for the first acquisition and 30 mCi for the last one. For each phantom acquisition AC and NC (non-corrected) /sup 201/Tl SPECT was performed. AC and NC images were evaluated by a 31-segment semiquantitative analysis. Comparisons between the circumferential count density profiles of the AC and NC segmented polar map were done. Evident degradation in the AC performance was demonstrated for line source activity lower then 60 mCi. From noise propagation the authors estimated that source activity higher then 300 mCi would give poor improvement in the AC performance.