THE INVESTIGATION OF PLACENTAL RELAXATION AND ESTIMATION OF PLACENTALPERFUSION USING ECHO-PLANAR MAGNETIC-RESONANCE-IMAGING

Echo-planar imaging (EPI) is a form of magnetic resonance imaging (MRI ) which acquires images in milliseconds rather than minutes as with co nventional MRI. The images produced using EPI are affected by the phys iological environment in which the hydrogen atoms producing the signal s are found, a process referred to as relaxation. Also by producing im ages a matter of milliseconds apart, quantification of perfusion withi n the tissue being imaged is feasible. The objective of this study was to investigate T1 and T2 relaxation times along with perfusion in pla centae from normal pregnancies at different gestations and also to com pare these to pregnancies complicated by abnormal placental function. A cross-sectional study of normal and compromised pregnancies from 20 weeks to term and a longitudinal study of normal pregnancy were perfor med. Placental T1, T2 relaxation times, and perfusion were measured us ing echo-planar magnetic resonance imaging. Placental T1 and T2 relaxa tion times decreased in normal pregnancy (P<0.001). Relaxation times i n pregnancies associated with placental pathology appeared to be reduc ed for that gestation although the numbers were too small to allow any statistical validation. No differences in placental perfusion with ge station or between normal and compromised pregnancy were demonstrated using this technique. This is the first demonstration of placental mag netic resonance relaxation and perfusion measurements in normal pregna ncy using echo-planar magnetic resonance imaging. In the future it may be possible to identify compromised pregnancies by differences in pla cental T1 and T2 relaxation times, using this novel non-invasive techn ique. (C) 1998 W. B. Saunders Company Ltd.