How Long Should You Avoid Close Contact — After a PET-CT?

The standard recommendation is 6 hours, counting from the time of your injection, not from when you leave the scan suite. This applies to young children and to any pregnant relatives. Some centres say up to 12 hours if you share a bed with an infant who cannot keep distance during the night. If your discharge sheet gives a different number, follow that — it may be adjusted for the specific dose you received or your child's age. When in doubt, call the centre that performed your scan.

Yes. Sitting next to a stranger on a bus or train for a short journey is not the sustained, close proximity the precaution is designed to prevent. The concern is prolonged contact — many minutes or hours — with the same person, particularly a child or pregnant woman. A short commute next to an adult you do not know does not meet that threshold. Travel home normally, and drink water on the way.

No, unless your partner is pregnant. If your partner is not pregnant, sharing a bed is fine — the distance precaution applies to young children and pregnant women, not to other adults. If your partner is pregnant, one night in a separate room is the simplest solution. After 6 hours from the time of your injection, that precaution is no longer necessary — so if the 6 hours pass before bedtime, you do not need to separate at all.

Tell the imaging team before your scan, or at check-in if you did not mention it beforehand. Most guidance advises a gap before resuming breastfeeding after an FDG PET-CT, and milk expressed during that window should be discarded rather than used. The exact timing depends on the tracer and dose you received, so the team who performed your scan is the right source for this advice — not a general figure. If you did not raise it at the time, call the centre before you feed again.

Children are more sensitive to ionising radiation than adults because their bodies are still developing. Rapidly dividing cells — found in growing tissues — are more affected by radiation than mature, stable cells. A young child also has a longer lifetime ahead, giving more time for any small risk to accumulate. These are the same reasons children receive reduced radiation doses in CT scans. The dose from being near you is low; the extra caution around children reflects that lower thresholds apply to them, not that the risk is large.

No. The CT scanner delivers a beam of X-rays during the scan, but those X-rays pass through you and stop — they do not make your body radioactive. Only the injected tracer stays in your body and continues emitting radiation after you leave. Once the scan is finished, the CT component carries no further concern. All the precautions after a PET-CT are about the tracer, not the CT.

No special precautions are needed for elderly adults who are not pregnant. Radiation protection guidelines single out young children, because of their developing tissues, and pregnant women, because of the fetus. Older adults at home do not fall into either group, and normal contact with them is fine throughout the day. If an elderly relative has a serious illness and their own treating doctor has specific concerns, that is worth raising with their team — but it is not part of the standard guidance.

Brief, unplanned contact is not what the precaution is designed to prevent. The guidance addresses sustained close proximity over many minutes, not a quick interaction that happened before you were aware of the recommendation. The additional exposure from a few minutes of holding is very small. There is nothing you need to do now except follow the precautions for the remainder of the 6-hour window. If you are worried, call the imaging centre — they can reassure you with the specifics of your scan and dose.