A COMPARISON OF GD-153 AND CO-57 AS TRANSMISSION SOURCES FOR SIMULTANEOUS TCT AND TL-201 SPECT

In this study we investigated the potential of Gd-153 and Co-57 as tra nsmission sources. Since both of these sources have higher energy phot opeaks higher than that of the predominant Tl-201 photons, they will r esult in contamination of the emission data. The amount of contaminati on and the ease of compensating for it are important factors in select ing an isotope for the transmission source. These factors were investi gated and, based on these studies, we conclude that both isotopes resu lt in a level of contamination that is significant in comparison to ty pical Tl-201 emission count levels. While Gd-153 results in approximat ely 50% more contamination of the emission data than Co-153, the objec t dependence of the contamination for both isotopes is such that conta mination compensation will be difficult. In fact, compensation may be somewhat easier for Gd-153. As a result, selection of one of these iso topes may be based on other considerations such as cost and usability with other emission isotopes.