ESTIMATION OF FETAL VOLUME BY MAGNETIC-RESONANCE-IMAGING AND STEREOLOGY

The current methods to monitor fetal growth in utero are based on ultr asound image measurements which, lacking a proper sampling methodology , may be biased to unknown degrees. The Cavalieri method of stereology guarantees the accurate estimation of the volume of an arbitrary obje ct from a few systematic sections. Non-invasive scanning methods, and magnetic resonance imaging (MRI) in particular, are valuable tools to provide the necessary sections, and therefore offer interesting possib ilities for unbiased quantification. This paper describes how to estim ate fetal volume in utero with a coefficient of error of less than 5% in less than 5 min, from three or four properly sampled MRI scans. MRI was chosen because it does not use ionizing radiations on the one han d, and it offers a good image quality on the other. The impact of pote ntial sources of bias such as fetal motion, chemical shift and partial voluming artefacts is discussed. The methods are illustrated on four subjects monitored between weeks 28 and 40 of gestation.