Radiation-optimized wide-volume CT pelvimetry: Size-adjusted foetal dosimetry and combined radiologists scoring-based...

Computed tomography (CT) pelvimetry provides reproducible three-dimensional assessment of maternal pelvic dimensions but remains limited by concerns regarding foetal radiation exposure. This study evaluated whether wide-volume CT (VMCT) acquisition provided on an 80-detector-row system could substantially reduce radiation dose while preserving pelvimetric landmark visibility. A previously validated size-adjusted foetal head dose (SAFHD) model integrating maternal size-specific dose estimate (SSDE) and foetal head geometry was applied to provide individualized dosimetry.

In this retrospective study, 100 pregnant patients underwent CT pelvimetry using either conventional helical mode CT (HMCT, n = 50) or wide-volume CT (VMCT, n = 50) at 100 kV. Acquisition parameters, CTDI_vol, DLP, SSDE_pelvis, and SAFHD were used for benchmarking. Eight key pelvimetric landmarks were qualitatively scored (5-point scale) by two experienced radiologists. Quantitative ROI analysis assessed attenuation, noise, signal-to-noise ratio (SNR), and figure of merit (FOM = SNR²/dose). Statistical comparisons between groups were performed using an independent-samples Student's t-test.

VMCT reduced CTDI_vol from 4.41±1.51 to 1.34±0.20 mGy (-69.6%) and DLP from 100.27±33.34 to 30.60±4.46 mGy.cm (-69.5%). SSDE_pelvis decreased from 5.20±1.80 to 1.58±0.23 mGy (-69.6%), while SAFHD decreased from 5.38±1.48 to 2.36±0.19 mGy (-56.0%). Main cohort dose reduction was 67.62±6.62%. Landmark visibility remained high (mean 4.0-4.6/5) with overlapping variability. Mean attenuation differences were ≤5 HU between protocols. Noise increased modestly with SNR reduction of 7-9%; however, bone SNR remained >30. FOM improved approximately 2-2.5-fold across tissues with VMCT.

Wide-volume CT pelvimetry achieved a consistent two-thirds reduction in scanner output and maternal size-adjusted dose, with a 56.0% reduction in size-adjusted foetal dose, while maintaining robust anatomical landmark conspicuity and improved dose efficiency. VMCT represents a viable low-dose alternative when CT pelvimetry is clinically indicated.

CT scans can be used to measure the pelvis during pregnancy, but there are concerns about radiation exposure to the unborn baby. This study compared two CT scanning methods by reviewing scans from 100 pregnant patients to see if a newer approach could lower radiation while still providing clear images. This study found that the newer method greatly reduced radiation to both the parent and fetus while still showing key anatomical landmarks clearly. This matters because it may allow safer use of CT when needed during pregnancy.