If radiation hits a tissue stem cell, it can damage the DNA and also cause cell mutation. If that mutation subsequently survives apoptosis and immune processes, then it would result in cancer. Reports based on epidemiological studies of Hiroshima and Nagasaki atomic bomb survivors and other data indicate that the risk of fatal cancer to a person exposed to 100 milligrays of radiation over the entire body increases by 0.5 %. No significant increase was confirmed for whole-body exposures of 100 milligrays or less. Though the exposure dose during examinations is not uniform, it is on average about 10 to 15 milligrays during a PET-CT scan, which scans the entire body. During coronary artery CT scans, which involves higher localized dose levels, the heart absorbs a dose of about 50 milligrays.
Effects of Radiation on the Body