Measurement of apparent diffusion coefficient (ADC) in fetal organs and placenta using 3 Tesla magnetic resonance imaging (MRI) across gestational ages

Diffusion-weighted imaging (DWI) is a technique used to probe the random microscopic motion of water protons in living tissue, represented by a parameter measurement of apparent diffusion coefficient (ADC) values. This study aimed to measure the ADC values of various fetal organs and placenta using 3T at various gestational ages. This was a prospective observational study. A total of 103 singleton pregnancies from 20 to 38 weeks of gestational age were included. Diffusion-weighted imaging was performed in the axial plane from the fetal head to the trunk with the following parameters: TR: 2000-2500 ms; TE: 88 ms; FOV: 250 mm; 256 matrix; slice thickness: 4 mm with a 0 mm gap; acquisition time: 1 min, 18 s. Diffusion gradient values were b = 0 and b = 700 s/mm². ADC was measured in fetal brain regions (frontal white matter, occipital white matter, centrum semiovale, pons, thalamus, cerebellum, and fetal organs (lungs, kidney, and placenta). ANOVA was used to calculate the mean ADC values. Karl Pearson's coefficient of correlation was used to evaluate the correlation between ADC values and increasing gestational age. The mean ADC values of brain regions were: frontal white matter (1.64 ± 0.08 × 10^{- 3} mm² /s, F-39.10,p-<0.001), occipital white matter (1.64 ± 0.06 × 10^{- 3} mm²/s, F-26.14, p-<0.001), centrum semiovale (1.62 ± 0.03 × 10^{- 3} mm²/s, F-49.88,p-<0.001, pons (1.23 ± 0.09 × 10^{- 3} mm²/s F-9.14,p-<0.001) ), Thalamus (1.21 ± 0.07 × 10^{- 3} mm²/s, F-13.54,p-<0.001) and cerebellum (1.36 ± 0.10 × 10^{- 3} mm² /s, F-4.19,p-<0.001). The mean ADC values of fetal organs were lung (1.92 ± 0.15 × 10^{- 3} mm² /s, F-28.24, p-<0.001), kidney (1.34 ± 0.11 × 10^{- 3} mm² /s, F-1.05, p- 0.37) and placenta (1.94 ± 0.11 × 10^{- 3} mm² /s, F-160.33, p-<0.001). White-matter regions showed a significant positive correlation with increasing gestational age. Statistically, a negative correlation was observed between increasing gestational age and ADC measurements obtained in the thalamus, cerebellum, pons, and kidney. This will be one of the first few studies to provide the ADC values of the fetal brain and fetal organs using 3T MRI. The current study shows that diffusion-weighted MRI can offer a promising technique to evaluate the structural development of fetal organs and can potentially lead to a biomarker for predicting the functionality of the fetal organs in abnormalities.