Can three-dimensional pelvimetry using low-dose stereoradiography replace low-dose CT pelvimetry?

To evaluate the reliability of pelvimetric measurements performed using stereoradiographic imaging (SRI), and to assess maternal and fetal radiation doses compared to low-dose computer tomography (CT) pelvimetry.

Thirty-five pregnant women (mean age, 29.6±5.5 [SD] years; range: 20-41 years) were prospectively included. All women underwent simultaneous frontal and lateral low-dose SRI and low-dose CT examination of the pelvis. Pelvimetry measurements were obtained from both examinations and radiation doses obtained with the two techniques were compared.

SRI-CT correlation (Pearson coefficient correlation [r]; mean bias [mb]) was strong for transverse inlet diameter (r=0.92; mb=-0.09cm), anteroposterior diameter of the pelvic inlet (r=0.92; mb = 0.47cm), maximal transverse diameter (r=0.9; mb=0.21cm), sacrum length (r=0.9; mb=0.09cm). Correlation was good. Correlation was good for the sacrum depth (r=0.75; mb=0.06cm) and Magnin's index (r=0.7; mb=0.5cm). Correlation was moderate for anteroposterior diameter of pelvic outlet (r=0.6; mb=0.52cm). The fetal dose was 13.1 times lower using SRI (87±26μGy) than CT (1140±220μGy, P<0.0001). The effective maternal dose was 3.1 times lower using SRI (97±21μSv) than CT (310±60μSv; P<0.0001).

Pelvic inlet measurements using SRI are reliable. Compared to CT pelvimetry, SRI leads to a significant decrease in fetal and maternal radiation doses. These findings should prompt physicians to use SRI as the first-line approach for pelvimetry.