Diffusion-T2 correlated spectroscopy imaging to explore possible placental composition changes over gestation

Placenta plays a vital role for fetal growth and development during pregnancy. Currently, antenatal noninvasive imaging techniques to directly evaluate placental function remains challenge. Diffusion-T2 correlated spectroscopy imaging (DT2SI) can provide compositional information for different organs in-vivo. The aim of this study was to investigate the use of DT2SI as a tool to elucidate the placental composition change over gestation in healthy pregnancy.

Forty healthy singleton pregnancies were retrieved from our placental MRI research database. MRI was performed at 23.1-36.0 weeks of gestational age (GA) in a 3.0T system. DT2SI measurements were performed using DWI sequence with 7 b-values combining 4 TEs. ROIs were manually defined inside placenta on five cross-sectional slices covering the most central part of placenta. D-T2 Spectra were constructed and segmented into 9 compartments: A1_{(low D, short T2)}, A2_{(low D, medium T2)}, A3_{(low D, long T2)}, B1_{(medium D, short T2)}, B2_{(medium D, medium T2)}, B3_{(medium D, long T2)}, C1_{(high D, short T2)}, C2_{(high D, medium T2)}, C3_{(high D, long T2)}. Volume fraction V_m of each compartment m was obtained voxel by voxel, and general V_m of whole ROI was calculated for each participant. The relationships of V_m to GA were assessed by Pearson correlation.

Four to five peaks could be observed in the spectrum for most subjects. Strong correlation between DT2SI V_m and GA was found. V_A1 (r = 0.633, p < 0.001) showed a significant increase with GA. V_A2 (r=-0.465, p = 0.002) and V_A3 (r=-0.653, p < 0.001) showed a moderate/remarkable decrease. The compartment V_B1 (r = 0.358, p = 0.023), V_C1 (r = 0.411, p = 0.008) illustrate a slight/moderate increase. Other compartments have low concentration (average V < 3%).

Comprehensive information on evolution of placenta composition with gestation could be provided by DT2SI, suggesting its unique value for assessing placental function during pregnancy.