If you're like me and don't know a lot about radiation, PEMMorsels has a good introduction, as does the Short Coat:
- 1 Sv= 100 rem. We use milliSieverts in most medical imaging.
- Neoplasms have typically been associated with radiation in excess of 50 mSv
- Background radiation = 3.5 mSv/year
- Background Cancer Incidence = 420:1000 (42%)
- Medical radiation is between 0-100 mSv
- Routine abdominal CT scan estimated exposure quoted as 8-10 mSv
- Actual calculated radiation: Average 11-20 mSv (Range 4-45 mSv)
- Multiphase abdomen and pelvis CT scanning: median 31 mSv (Range 6-90 mSv)
- Chest CT for suspected pulmonary embolus: median 10 mSv (Range 2-30 mSv)
- Routine head CT median: 2-3 mSv (Range 0.3-6 mSv)
- 2-3 brain CT triples the risk of brain tumours
- 5-10 brain CTs triples the risk of leukaemia
- Per 10,000 patients, a head CT might cause a brain tumour and leukaemia in one person.
- At 10 mSv Lifetime Attributable Risk of developing a cancer is 1:1000
- One additional cancer for every 4000 CT heads.
And this is the risk if it all goes right! If it goes wrong, the doses could be a lot more. And if there is a radiation emergency, what would you do?
Times are changing, and we're moving away from CT scans, and towards observation. So think carefully before you do the CT scan.
All of this is nicely summarised by St Emelyns - there is often no right answer, and you have to balance the risks.