Investigators recently published a study in Scientific Reports examining whether patients undergoing myocardial perfusion single-photon emission computed tomography experience DNA damage due to repeated exposure to ionizing radiation.
Radiation exposure from interactions with radioactive materials in the environment accounts for approximately 80% of an individual's total exposure, while radiation for medical purposes comprises a much smaller amount. Although myocardial perfusion single-photon emission computed tomography (MPS)—a common, noninvasive cardiac imaging procedure used to diagnose coronary artery disease—exposes patients to low doses of radiation considered safe, the procedure may add to patients’ cumulative lifetime radiation. Previous studies have found a positive correlation between radiation doses and the risk of DNA damage, suggesting a potential risk even with low-dose radiation.
In the recent study, the investigators analyzed markers of DNA repair and damage in 32 patients aged 18 years and older undergoing Technetium (Tc)-99m–sestamibi MPS with a mean dose of 15.1 mCi. They collected peripheral blood samples at rest before radiotracer injection and within 60 to 90 minutes post-injection, using a single-cell gel electrophoresis assay to identify DNA strand breaks within the samples.
The investigators evaluated three factors: comet tail DNA percentage, tail length, and tail moment (defined as the product of both). In response to DNA damage, cells trigger genes and proteins responsible for apoptosis, DNA repair, cell cycle regulation, and chromatin remodeling. Therefore, the investigators used quantitative polymerase chain reaction (PCR) tests to determine the expression of the ATM, ATR, BRCA1, CDKN1A, and XPC genes.
The investigators discovered no statistically significant differences in comet tail DNA percentage, tail length, or tail moment between the pre- and post-injection samples. Further, quantitative PCR tests showed increased BRCA1 (P = .0053) and XPC (P = .0359) expression following the injections, but no statistically significant differences in expression pre- and post-injection among the other genes. The investigators hypothesized that the expression of these two genes was likely caused by low-level activation of DNA repair genes secondary to DNA damage.
The findings indicated that the ionizing radiation patients are exposed to during a single MPS may not be high enough to activate a large DNA repair response, representing an insignificant amount of DNA damage. However, these imaging tests should only be conducted when appropriate to avoid unnecessary radiation exposure.
A full list of disclosures can be found in the original study.