Quantitative T2 Changes and Susceptibility-Weighted Magnetic Resonance Imaging in Murine Pregnancy

Objective: To evaluate gestational age-dependent changes in the T2 relaxation time in normal murine placentas in vivo. The role of susceptibility-weighted imaging (SWI) in visualization of the murine fetal anatomy was also elucidated. Methods: Timed-pregnant CD-1 mice at gestational day (GD) 12 and GD17 underwent magnetic resonance imaging. Multi-echo spin echo and SWI data were acquired. The placental T2 values on GD12 and GD17 were quantified. To account for the influence of systemic maternal physiological factors on placental perfusion, maternal muscle was used as a reference for T2 normalization. A linear mixed-effects model was used to fit the normalized T2 values, and the significance of the coefficients was tested. Fetal SWI images were processed and reviewed for venous vasculature and skeletal structures. Results: The average placental T2 value decreased significantly on GD17 (40.17 +/- 4.10 ms) compared to the value on GD12 (55.78 +/- 8.13 ms). The difference in normalized T2 values also remained significant (p = 0.001). Using SWI, major fetal venous structures like the cardinal vein, the subcardinal vein, and the portal vein were visualized on GD12. In addition, fetal skeletal structures could also be discerned on GD17. Conclusion: The 12 value of a normal murine placenta decreases with advancing gestation. SWI provided clear visualization of the fetal venous vasculature and bony structures. (C) 2014 S. Karger AG, Basel