Abstract 18210: Quantitative Flow Cytometry Detects DNA Damage in Patients Undergoing Cardiac SPECT
Introduction: Radiation exposure to medical imaging has doubled in the last two decades, raising concerns for possible increased cancer risk. Despite being the primary source for low dose radiation exposure for cardiac patients, single-photon emission computed tomography (SPECT) remains the preferred functional test in the United States. Whether cardiac SPECT damages DNA is unknown. Hypothesis: We hypothesized that low dose radiation induces phosphorylation of histone 2AX (H2AX) and protein p53, two proteins in the DNA damage response pathway in vitro and in patients undergoing cardiac SPECT.
Methods: For in vitro study, whole blood from healthy volunteers (n=5) received either irradiation with a single dose of 50 mGy and 5,000 mGy, or sham-irradiation. Whole blood was maintained at 37° for 30 min or 2 h following irradiation. For in vivo study, blood was collected from adult patients immediately before and 2 h after SPECT and ECHO, respectively. After separation of T-lymphocytes, phosphorylation of H2AX and p53 was analyzed by quantitative flow cytometry.
Results: The in vitro study showed a significant and marked increase in phosphorylation of H2AX and p53 in T-lymphocytes after low (50 mGy) and high dose irradiation (5,000 mGy) compared with sham-irradiated controls. Similarly, patients undergoing cardiac SPECT (8-10 mSv) had increased phosphorylation of H2AX and p53, compared to Echo patients. Interestingly, this effect was also observed in only 20-30% of patients (Figure 1).
Conclusions: Single exposure to low dose radiation from cardiac SPECT can induce phosphorylation of radiation-responsive proteins, providing evidence that DNA can be damaged in some adult patients undergoing cardiac SPECT. Further study is needed identify the factors causing increased sensitivity to low dose radiation.
- © 2012 by American Heart Association, Inc.