Magnetic Resonance Imaging (MRI) used during pregnancy to measure fetal brain size

A routine part of screening during pregnancy is to monitor the development of the fetus and this includes monitoring fetal growth using ultrasound. This assessment includes measuring skull dimensions e.g head diameter and/or circumference. These measurements are then used as an indirect indication of brain development. It is assumed that skull size is matched by brain size but the association is not always perfect.

Prenatal Diagnosis Front CoverQuantifying the growth of the fetal brain itself is a relatively new area of research and could possibly provide a more accurate way of assessing brain development. It is therefore important to establish reliable normal ranges. Our work focused on developing a method to acquire images of the whole fetal brain using Magnetic Resonance Imaging (MRI). These images were used to generate brain volumes to create a database of reference values. The study recruited pregnant women to undergo MR imaging in the University MRI Unit here at the University of Sheffield. All the fetuses we scanned were between 18 and 36 weeks old. We collected the MR images from 132 normally developing fetuses. Each MR image, from each fetus, was drawn around freehand using computer software. This allowed the anatomical boundaries of the brain to be identified and a set of volume data to be produced.

The software we used, in order to calculate the volume data, also generated a 3D model providing a representation of the surface of each fetal brain. Some of the resultant images were featured on the front cover of the journal ‘Prenatal Diagnosis’ (as shown right) which also published our research.

Having the resultant reference values from such a large number of fetuses is an important step in understanding how the brain grows during pregnancy.

They could also possibly be used as a reference tool in the clinical setting allowing comparison of brain volumes in fetuses with suspected abnormal development against the ‘normal’ range.

This information could potentially provide clinicians with additional information and help to direct clinical management during pregnancy.

The study has been published in journal ‘Prenatal Diagnosis’.
DOI: 10.1002/pd.4961

The project was funded by the National Institute for Health Research (NIHR) and part of the MERIDIAN study.