June 23, 2010
Researchers say patients are currently at risk for receiving more radiation than necessary from Computed Tomography (CT scans) and increasing cancer risk due to a current lack of standardization, monitoring and regulation of how imaging equipment is used.
The editorial “Is Computed Tomography Safe?” by Rebecca Smith-Bindman, M.D. and researchers at the University of California appears in the June 24, 2010 issue of the New England Journal of Medicine (NEJM).
As an example of the type of radiation overexposure hazard patients face, the editorial tells the story of a 59-year-old schoolteacher who went to her local emergency room complaining of facial paralysis. Doctors performed CT and MRI (magnetic resonance imaging) scans. The scans were normal and they diagnosed her with Bell’s palsy, which went away shortly thereafter.
However, two weeks later the woman lost her hair in a band-like pattern and then developed vertigo and confusion. She returned to the ER where more she received more CT and MRI scans, which were normal. She then experienced fatigue, malaise, memory loss and confusion that interfered with her ability to work.
By examining records of the schoolteacher’s first CT scan, she received a radiation dose of 6Gy, about 100 times the average brain CT scan, 10 times the dose from the average brain-perfusion scan and triple the daily dose of radiation treatment for brain cancer.
According to the editorial, more than 378 patients in the U.S. received brain perfusion scans with similar radiation overdoses.
“Although such imaging techniques may have a role in diagnosis, there are few evidence based guidelines regarding their appropriate use, and institutional use varies widely, reflecting physicians’ preferences and manufacturers’ promotion of these capabilities, rather than scientific evidence of improved clinical outcomes,” said Rebecca Smith-Bindman, M.D.
Smith-Bindman and her colleagues calculated that the risk of cancer from a single CT scan could be as high as 1 in 80. Considering that each year, about 10% of the U.S. population receive a CT scan and some 75 million scans performed, a significant amount of the population may be at risk for increased radiation exposure and related cancers from these tests. They say an effort must be made to reduce patient radiation exposure and that the radiation dosage from CT scans could be reduced by 50% without reducing diagnostic accuracy.
The U.S. Food and Drug Administration (FDA) may approve such medical devices as CT scanners, but has no power to regulate the device’s usage. The editorial urged Congress to give the U.S. Food and Drug Administration oversight.
“If given a legislative mandate, the FDA could take the lead in creating standards and assessing compliance,” Smith-Bindman said. “Facilities that could not meet the standards should not be certified to conduct CT.”