Some patients show signs of potential DNA damage after SPECT

Some patients may have greater risk of DNA damage due to radiation exposure from SPECT myocardial perfusion imaging, even though the radiation dose is low, according to a study published Jan. 21 in Circulation: Cardiovascular Imaging.

Using single-cell gene expression profiling and quantitative flow cytometry, researchers looked at low-dose radiation exposure, as occurs with SPECT myocardial perfusion imaging, and DNA damage response pathways. Won Hee Lee, PhD, from the Stanford Cardiovascular Institute in California, and colleagues examined the effect of radiation on gene regulation through three parallel groups: 63 patients undergoing SPECT, 12 patients as a positive control undergoing invasive coronary angiograms, and 15 patients as a negative control undergoing echocardiography. SPECT patients had a technetium-99m tetrofosmin rest/exercise same-day protocol.

Blood samples were taken before and after each test. A group of patients also underwent a series of time point samples following the test.

They looked at the DNA-damage marker proteins H2AX, protein 53 and ataxia telangiectasia mutated protein, which are considered indicators of cellular damage, in 45 patients. The patients displayed no differences in phosphorylation in all three proteins compared with baseline but about one third of the patients showed increased protein phosphorylation in at least one marker.

Among serial samples, some patients still had detectable changes in gene expression at 48 hours after SPECT. However, in the majority of patients over time, regulation returned to normal. On average, trends toward downregulation occurred for a number of cell gene expression among T lymphocytes through 24 hours.

“[O]ur results also show that the risk of low-dose radiation is not zero, and, therefore, it should continue to be standard practice to perform all imaging studies at the lowest possible radiation dose without compromising diagnostic image quality,” Lee et al wrote.