March 17, 2011 by dailybolusoflr
Radiation dose in early pregnancy
mSV or MilliSieverts is a measurement of the effective dose of ionizing radiation to the patient. It is an average dose and does not reflect age or gender and does not reflect the higher radios-sensitivity of particular tissues.
— Before 2 weeks: > 100 mSv risk for spontaneous abortion (this is a VERY large dose…remember that a pan scan CT for trauma patients gives about 40 mSV)
— Teratogenic effects
— Between 2 and 16-20 weeks at doses of > 50-150 mSv there is evidence of teratogenesis.
— 50mSv is a high dose but in your trauma patient, you can come close. .re-scan the abdomen and pelvis once and you are over 50 mSV
— 20 weeks: very unlikely to sustain any teratogenic effects even at higher doses
— Carcinogenic effects
— Always a risk
— Baseline risk of fatal childhood cancer 1 in 2000 (about 50% of childhood cancers are fatal)
— Fetal dose of 50 mSv is associated with a relative risk of 2 …this means that the risk of a fatal childhood cancer would increase to 1 in 1000 (the highest fetal dose from a single imaging study is from abdominal pelvic CT which equals about 15mSv)
For the purposes of the CDC table. . 0.05 Gy is equivalent to 50 mSv
Super complicated stuff. .but good to know there are some resources out there to help you talk to your patients.
Linda Regan, MD FACEP
Program Director, Emergency Medicine Residency
Johns Hopkins Medical Institutions
1830 East Monument Street
Baltimore, MD 21287