Study calls for more consistent standards to lower dose variation

A new study suggests that greater dose variations may be due to use of scanners by different medical staffs

January 04, 2019
by John R. Fischer , Staff Reporter
A new study says variations in CT radiation dose exposure may have more to do with staff than patient differences or the machine used.

Compiled by an international research team, the findings suggest that greater differences in the amount of radiation dose from CT scanners are primarily due to how different medical staffs use the machines, ushering in the need for more consistent dose standards to protect patients from unnecessary radiation risks.

"The benchmarks and standards exist through a variety of sources as to how to set up CT examinations. The question is why aren’t those standards accessed or followed or recognized," Dr. Donald Frush, a professor of radiology and pediatrics in Duke’s department of radiology who was not a part of the study, told HCB News. "I think fundamentally practices and people who run those things are doing many things at one time from an imaging standpoint."

CT radiation doses vary on high levels across patients, institutions and countries. Research, however, shows that exposures can be reduced by 50 percent or more without mitigating image quality and diagnostic accuracy.

Evaluating dose CT data across seven countries, the team reviewed more than two million scans from 151 institutions. The exams consisted of abdomen, chest, combined chest and abdomen, and head evaluations taken between November 2015 and August 2017 from 1.7 million adults.

Researchers adjusted data for different variables related to the patient, such as sex and size, finding little change in dose variation across countries. Adjustment of patient characteristics, for instance, still saw a fourfold range in mean effective dose for abdominal scans and a proportional 17-fold range in high-dose scans. Similar variations were found with chest scans and combined abdomen scans, and little change was also found when adjusting factors such as institution type or machine manufacturer and model.

When adjusting for the technical factor of how scanners are used by medical staff, however, nearly all dose variation was substantially reduced or eliminated across nations.

An observational study, the research does not establish cause and was limited by the exclusion of several technical factors: the lack of information on other imaging modalities used on patients, the use of a single indication on a single machine model, and focus on only institutions that invest in dose monitoring software rather than ones that do not.

It does, however, suggest that optimizing doses based on a consistent standard can be achieved.

"Fundamentally, I think that in order to have a sort of concerted consistent effort across the entire landscape of CT practices, we as the healthcare community need to have a better strategy than what we have now," said Frush. "We have sort of relied on radiologists to drive this. The radiologists are doing a lot of other things. The technologists could help drive this. They’re front line and dealing with CT and patients all the time. They have the expertise and knowledge. We should have administrators, radiologists, technologists and many others involved in this process."

The findings were published in The BMJ.

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