When given access to patient radiation exposure histories, radiologists will take them into consideration when assessing the risk from future imaging studies. The problem though, according to a study published in the June issue of the American Journal of Roentgenology, is that radiologists mistakenly believe this is in keeping with the linear no-threshold model.
The linear no-threshold model says that additional cancer risk is linear in respect to absorbed doses, and only becomes zero at zero dose; this means that a new radiation exposure carries the same risk, regardless of previous exposures.
For the study, the researchers--led by Massachusetts General Hospital radiologist Pari Pandharipande--surveyed radiologists, asking them to make an imaging recommendation for a hypothetical patient with a history of undergoing CT scans. They were asked whether they incorporated cancer risks from previous imaging, reported acceptance or rejection of the linear no-threshold model, and understood the implications of the model in this setting. The expectation, the authors said, was that those radiologists acting in accordance with the model would disregard previously incurred cancer risks.
Of the 322 radiologists who completed the survey, 92 percent incorporated risks from the patient's exposure history during their decision making. More than half (61 percent) reported acceptance of the linear no-threshold model, with just 25 percent rejecting it and 15 percent not making a judgment. Among those who either accepted or rejected the linear no-threshold model, just 36 percent made decisions consistent with their model beliefs.
As reported by AuntMinnie.com, the authors said that the confusion about what the linear no-threshold model means is problematic because it could lead radiologists to avoid ordering beneficial imaging examinations in an effort to reduce radiation-associated cancer risks. The researchers concluded more education is needed about decision making and radiation dose. Last week, we reported that Salt Lake City-based Intermountain Healthcare is launching a system that will allow it to measure and report patients' cumulative radiation exposure from imaging examinations. Hospital officials said they hope tracking cumulative radiation dose from the 220,000 annual CT scans and radiology procedures will make it easier to make decisions about the appropriateness of imaging studies.
"Our findings raise concern that many radiologists have a limited understanding of how to address patient exposure histories when making prospective imaging decisions and underscore the need for related educational interventions," Pandharipande and colleagues said. "Our results also suggest that making individual patient exposure histories available to ordering physicians may lead to undesirable effects on decision-making regarding the use of imaging."