Avoiding inadvertent fetal exposure to radiation in nuclear medicine examinations – proactively improving the process by failure mode and effects analysis

Introduction: The radiation dose to the fetus from a diagnostic nuclear medicine procedure should present no risk of fetal death, organ malformation, impairment of growth or mental development. For the majority of diagnostic medical procedures, the associated radiation risks of childhood cancer due to fetal exposure are very low. Exposure of pregnant women to higher dose procedures in excess of ten milligray, however, may result in a doubling of the childhood cancer risk compared with the natural rate. We performed a quality improvement project to proactively redesign the process in our institute with a view to avoiding inadvertent fetal exposure to radiation in diagnostic nuclear medicine examinations.

Methods: A failure mode and effects analysis was performed. We organised the team, mapped the current process, identified potential weaknesses, rated the relative impact, and modified the process accordingly.

Results: Our team was composed of the unit head, senior clinicians, technologists, a nurse and a physicist. The current process was mapped (see figure 1) where five potential weaknesses were identified: 1. There may be failure to recognise a female patient of child-bearing age. 2. Patients with cognitive impairment may not be able to verbally confirm pregnant status, last menstruation period and/or sexual history. 3. Potential fetal radiation risks may be wrongly classified. 4. Patients’ declaration that pregnancy can be excluded may not be reliable. 5. Pregnancy test can be false negative. Accordingly, we have redesigned the process (see figure 2): 1. A red sticker will be put on the cover of the clinical folder of all female patients of child-bearing age. 2. For patients with cognitive impairment, pregnancy test will be performed. If negative, examination may proceed. Examination can only proceed with consent by two medical officers either from the ward (in-patient) or within department (out-patient). 3. A list of low-risk scans was produced by consensus of team members, including only studies for which SPECT/CT are rarely performed or the range of the CT normally does not extend to lower abdomen/pelvis. 4. For those patients declaring no pregnancy on the ground of condom or oral contraceptive use, they will have to further declare that the use has been consistent and proper. 5. When the date of a low-risk examination falls out of 28 days of last menstrual period, examination should be postponed unless urgent examination is needed for benefits that far outweigh the potential radiation risks to fetus.

Conclusions: For most diagnostic nuclear medicine procedures, the radiation risks of childhood cancer due to fetal exposure is very small (particularly if the exposure occurs later in pregnancy). However, some examinations yielding fetal doses in excess of 10 milligray could involve increased levels of risk that should be avoided, if possible, even in unrecognised pregnancies. Failure mode and effects analysis provides an effective tool to proactively improve the process with a view to avoiding inadvertent fetal exposure to radiation in nuclear medicine examinations. Last but not least, it is worth noting that even in case of unfortunate fetal radiation exposure in excess of 10 milligray, the additional childhood cancer risk is still low in absolute terms. Termination of the pregnancy would not be justified solely on the basis of the radiation risk to the unborn child.

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