[Evaluation of pelvic irradiation during x-ray computed tomography]

Accidental irradiation of an early and unknown pregnancy during abdomino-pelvic computed tomography has not yet been reported, but this situation will certainly occur as the indications for this type of investigation are extended. Assessment of foetal risk depends essentially, as in ordinary radiology, upon the X-ray dose received by the foetus. Only a few studies have been devoted to determination of the "gonad dose" received during an abdomino-pelvic scan. In ten patients undergoing abdomino-pelvic scan with a mean of 22.1 +/- 4.7 exposures per patient, the authors used a small thermoluminescent dose-meter placed in the uterus or endocervix to measure the gonad dose received. The dose delivered to the uterus was 1.67 cGy +/- 1.14 per patient, i.e. approximately the same as for hysterography (1.27 cGy). Thus any abdomino-pelvic scan before twelve weeks should be viewed as an indication for therapeutic abortion, whilst after twelve weeks the amount of radiation received does not in itself represent an indication for abortion.