Magnetic Resonance Imaging and Computed Tomography May Carry Similar (but Very Low) Risks of Carcinogenesis

In comparing magnetic resonance imaging (MRI) and computed tomography (CT), it is often stated thata significant advantage of MRI is its lack of ionizing radiation, which may contribute to carcinogenesis. This article questions whether this concern is justified. First, the basis for the linear no-threshold (LNT) hypothesis, which suggests a carcinogenic potential of CT, is now considered weak. Historically, the foundation of the LNT model was not grounded in robust scientific data, and the epidemiological evidence indicating an increased cancer incidence in children undergoing CTscans is not scientifically reliable. Both MRI and CT examinations elevate reactive oxygen species, leading to DNA damage, chromosomal aberrations, and micronucleus formation. Following a single scan with either MRI or CT, the γH2AX index in human lymphocytes increased to a similar degree; however, the small amounts of DNA damage produced are efficiently repaired, thus not resulting in carcinogenesis. While it may be argued that ionizing radiation induces more complex DNA damage than electromagnetic fields, no studies have compared the quality of DNA damage between MRI and CT at clinically relevant exposure levels. Considering the effective defense mechanisms of living organisms, infrequent MRI and CT examinations do not appear to pose an increased risk of carcinogenesis.