CT and nuclear medicine tests do have a downside, however: they deliver doses of ionizing radiation from 50 to over 500 times that of a standard x-ray, such as a chest x-ray or mammogram. Scientists have raised concerns that such large doses of radiation plus the widespread and increasing use these diagnostic procedures may, in a small but significant way, pose a cancer risk in the general population.
“The use of CT in particular has gone up dramatically, and we’ve drastically lowered the threshold for using it,” said Dr. Rebecca Smith-Bindman, a visiting research scientist with NCI’s Radiation Epidemiology Branch (REB). “There’s a general belief that if you get a CT scan, you must be reasonably sick and must really need it. This is no longer true, and we are increasingly using CT scans in patients who are not that sick. There’s been drift not only in how often we use it but in how we use it.”
“We’ve only talked about the benefits of CT for the past 20 years, without considering any potential harm” she continued.
Research estimated that approximately 29,000 future cancers could be related to CT scans performed in the United States in that year alone, with women being at higher risk than men. About 35 percent of these cancers were projected to be related to scans performed in patients 35 to 54 years old, and 15 percent related to scans performed in children younger than 18.
The medical community has proposed many ways to reduce radiation exposure from diagnostic medicine without negatively impacting the quality of patient care:
- Reduce the number of CT exams by using other technologies (such as ultrasound or MRI) in cases where they would provide equal diagnostic quality.
- Limit the use of CT in healthy patients who would obtain little benefit (such as whole-body CT screening).
- Limit the use of repeat CT surveillance of patients in whom a diagnosis has already been made, when repeat scanning would lead to little change in their treatment.
- Track and collect information on radiation exposure for individual patients.