Toggle Main Menu Toggle Search

Open Access padlockePrints

Fetal position and size data for dose estimation

Lookup NU author(s): Dr Keith Faulkner


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


In order to establish both positional and size data for estimation of fetal absorbed dose from radiological examinations, the depth from the mother's anterior surface to the mid-line of the fetal head and abdomen were measured from ultrasound scans in 215 pregnant women. Depths were measured along a ray path projected in the anteroposterior (AP) direction from the mother's abdomen. The fetal size was estimated from measurements of the fetal abdominal and head circumference, femur length and the biparietal diameter. The effects of fetal presentation, maternal bladder volume, placenta location, gestational age and maternal AP thickness on fetal depth and size were analysed. The fetal position from the anterior surface of the mother's abdomen is shorter for posterior placenta and empty bladder volume, but longer for anterior placenta and full bladder volume. Mean fetal depth (MFD) observed for all bladder volumes, fetal presentations and placenta locations increased from 6.5+/-0.5 cm to 10.2+/-10.7 cm over the duration of pregnancy. Similarly, mean fetal skull depth (FSD) increased from 6.6+/-0.6 cm to 9.8+/-0.6 cm over the period of pregnancy, but only from about 6.6 cm to 7.8 cm over the period (8-25 weeks) when damage to the developing brain has been observed to result in mental retardation. Using the range of mean fetal depth (4.7-13.9 cm) observed in this study and depth dose data at 75 kVp and 3.0 mmAl half value thickness (HVT), fetal absorbed dose would be overestimated by up to 66% or underestimated by up to 77% if the mean value of MFD (8.1 cm) is used rather than actual individual values. These errors increase with lower tube potential and filtration up to over 90% overestimation and up to 100% underestimation at 60 kVp and 1.0 mmAl filtration.

Publication metadata

Author(s): Osei EK, Faulkner K

Publication type: Article

Publication status: Published

Journal: British Journal of Radiology

Year: 1999

Volume: 72

Issue: 856

Pages: 363-370

Print publication date: 01/04/1999

ISSN (print): 0007-1285

ISSN (electronic): 1748-880X

Publisher: British Institute of Radiology