[Pelvimetry with compute tomography]

In 1993, Ullevaal University Hospital started CT pelvimetry. The accuracy of CT pelvimetric measurements and a low fetal dose are very important. In our study we tested the accuracy of CT pelvimetry and measured the fetal dose and the effective dose to the mother.

A lead scalar was exposed in different heights compared to the isocentre. Measurements were done at front and side scout views and compared to the real scale. Dose estimates were done in CT dosimetry (NRPB). Effective doses to patient as well as fetal doses were measured in this study. Fetal dose was estimated as uterus dose.

Our results show that the measurements are overestimates when the table is moved away from the isocentre against the tube. If the table is moved away from the tube and against the detector, the measurements are underestimates. The measurements in the isocentre are accurate. This means that CT pelvimetric measurements are accurate if the patient is placed in the isocentre. In our study the estimated fetal dose was 0.74 mGy and mother's effective dose was 0.3 mSv.

Our results show that the fetal dose is as low or lower than with conventional pelvimetry. The CT pelvimetric measurements are accurate if they are performed on patients in the isocentre. We recommend that CT pelvimetry replace conventional pelvimetry.