Using thallium-201 (Tl-201) as a radiotracer substitute for technetium-99m (Tc-99m) could lead to more downstream testing, increased costs and more radiation exposure, according to research published in Circulation: Cardiovascular Imaging. According to the researchers, from the University of Ottawa Heart Institute, Tl-201 is considered to be a "suboptimal radiotracer;" to that end, they wanted to understand the impact of using Tl-201 during a Tc-99m shortage.
The researchers looked at data from 7,402 consecutive patients referred for SPECT MPI studies to diagnose and assess coronary heart disease during the time the facility switched from Tc-99m to Tl-201. The patients were grouped according to those who underwent studies before the switch with Tc-99m (2,938 patients), during the switch with Tl-201 (2,959 patients), and after with Tl-201 (1,505 patients).
The researchers found that 21.4 percent of the patients in the Tl-201 group underwent downstream testing, compared to 12.1 percent in the Tc-99m group. The costs associated with downstream procedures were $165.22 for Tl-201 per person, compared to $90.97 for Tc-99m.
Radiation exposure for the SPECT study was 19.89 mSv for Tl-201 compared to 10.44 mSv for Tl-201, while the per patient radiation dose for downstream tests using radiation was 3.68 mSv for the Tl-201 group compared to 2.48 mSv for the Tc-99m group.
Much of the global supply of Tc-99m is supplied by the Canadian Chalk River nuclear reactor in Ontario, which was temporarily shut down in 2009; it is expected to close by 2016, CardiovascularBusiness reported.
"Although Tl-201 provided a short-term solution to the unexpected Tc-99m shortage, long-term cost-effective solutions should be areas of future study," the researchers concluded.
Researchers at TRIUMF, a subatomic physics laboratory based in Vancouver, are working to develope and deploy cyclotron production of Tc-99m, which would eliminate the need for a nuclear reactor.