Irish study reveals widespread ignorance of radiation risks

A new Irish study has highlighted an alarming lack of knowledge among clinicians about radiation exposure and its potential risks.

CT examinations account for 36% of all radiological procedures performed in Ireland, but they contribute 56% of the collective population dose, according to T.M. Walshe, MRCS, from Galway University College Hospital, who is lead author of a scientific poster presented at RSNA 2009. Radiologists have the responsibility to justify a medical exposure, but referring clinicians should have a basic knowledge of the radiation prescribed and the associated risks.

Walshe and colleagues asked a cross-section of nonradiologist junior doctors at the Galway hospital, a tertiary referral center, to complete a multiple-choice questionnaire. The total number of respondents was 100, representing a response rate of 94.3%. About 31% were experienced doctors just below consultant level (14% specialist registrars and 17% registrars), 34% were senior house officers (one to three years postqualification from medical school), and 35% were interns (doctors in their first year practicing since qualification). Nearly half the respondents were from general surgery, and another third came from general medicine.

The authors asked participants to estimate the number of chest radiographs needed for an equivalent effective radiation dose to the patient from several common radiological investigations.

None of the junior doctors gave all correct answers. Only 38% correctly estimated the number of chest radiographs that would be equivalent to a cervical spine x-ray exam, while 81% underestimated the number of chest radiographs equivalent to a lumbar spine radiograph series and 72% underestimated the figure needed to match an isotope bone scan. Only 30% correctly estimated the effective radiation dose from a CT scan of the brain, with 48% underestimating the effective dose from brain CT and 50% underestimating the dose from a CT scan of the abdomen and pelvis.

A total of 8% of the junior doctors believed ultrasound involves the use of ionizing radiation, and 27% thought MRI involves radiation. Of all respondents, 8% were not aware that radiation exposure increases the risk of teratogenesis and spontaneous abortion, and 5% were unaware of the higher risks of radiation-induced malignancy in children.

Participants then had to estimate the additional lifetime risk of developing a brain tumor following a single CT scan of the brain. The correct answer is one in 10,000, but the risk was underestimated by 72% of the sample. For CT exams of the abdomen and pelvis, 89% underestimated the risk of developing a tumor (one in 2000).

Furthermore, 60% of the junior doctors said they never explained to patients about the risks versus the benefits of radiation exposure, and 55% said patients never asked them about the risks involved.

Of the sample, 52 worked in an environment where radiation is regularly used and where they are exposed to radiation, but just six of them had attended a radiation protection course. Only 13 of these 52 respondents said they always wore a thyroid shield when working with radiation, 24 said they sometimes wore a thyroid shield, and 15 said they never wore a shield. Only three of the junior doctors said they always wore lead glasses when working with radiation, five said they sometimes do so, and 44 said they never wore the glasses. A mere three respondents said they always wear dosimetry badges when working with radiation.

In addition, 31% of the sample were not aware that radiation dose to staff could be reduced by asking them to step back from the operating table during screening, and 52% were unaware that dose to staff could be cut by bringing the image intensifier closer to the patient.

"There is a concerning lack of knowledge of radiation dose and related risks of commonly requested radiological investigations and a lack of awareness of the alternatives to radiological modalities not involving radiation," Walshe concluded. "There is also poor understanding of methods of reducing radiation dose to nonradiology staff members and an urgent need to educate junior doctors about the risks of radiation."

This knowledge gap is an international problem that requires an international response, Walshe said.