A comparison of Gd-153 and Co-57 as transmission sources for simultaneous TCT and Tl-201 SPECT

The authors have previously described a method for simultaneous acquisition of TCT and Tl-201 SPECT using a Tc-99m transmission source. However, for clinical implementation Tc-99m is impractical, especially for high activity sources required for short acquisition times. In this study the authors investigated the potential of Gd-153 and Co-57 as transmission sources. Since both of these have higher energy photopeaks higher than the predominant Tl-201 photons, they will result in contamination of the emission data. Thus, the amount of contamination and the ease of compensating the contamination are important properties in selecting an isotope. The authors have investigated the amount of contamination for each of these sources as well as properties affecting the difficulty of contamination compensation. Based on these studies the authors conclude that, while Co-57 results in somewhat less contamination, contamination from Gd-153 may be easier to compensate for. As a result, selection of one of these isotopes may be based on other considerations such as cost and usability with other emission isotopes