A 25 yo female is 7 weeks pregnant and has suspected Pulmonary embolus and the ED doctor is considering a CTPA. The foetal dose associated with this CT has been estimated to be 0.08mSv. What are the potential radiation risks to the foetus and how you would communicate these to the ED doctor.
I would inform the ED doctor that the dose of radiation to the foetus is low however there are two types of radiation risks to the embryo: stochastic and deterministic risks.
- Deterministic risk: As the foetus dose is less than 100mSv , there will be no deterministic risks.
- Stochastic risk: Approx 6-10% per 1Sv = 1000 mSV, hence 1 in 10 000 people would develop a cancer per 1 mSv. At 0.05mSv, the foetal stochastic risk would be increased by 1 in 200 000. The baseline childhood risk of cancer is 1 in 500.
Hence, overall, the stochastic risk is low to the embryo, however would need to justify and optimise the CTPA, attain informed written consent from the patient for the CTPA, as well as to consider the possibility of using an alternative scan such as VQ scan or whether the scan is necessary. The patient should receive information of these potential risks and be directed to Inside Radiology for further information.
Which organ dose would be most relevant to be calculated for this patient?
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