Correlating Placental ADC Values with Gestational Age and Grannum Class in Normal Placentas

Abstract

Background: Recently there have been attempts to link fetal growth retardation to placental morphology as well as apparent-diffusion coefficient (ADC) values. Objectives: The purpose of this study was to investigate the possible correlation of apparent diffusion coefficient (ADC) values of normal placentas with different gestational ages and various Grannum grades (Gg). Patients and Methods: Thirty-eight women were included in this study. All women with singleton pregnancies referred for fetal MRI who were proven normal in pre/postnatal follow-up were included in the study. All placentas were evaluated by ultrasound trans-abdominally. The placenta was assessed for maximal thickness, subjective shape, presence of possible infarcts, sub-placental, and subchorionic hemorrhage. Placentas were also evaluated for G-grading and signal intensities in T2 half-fourier acquisition single-shot turbo spin-echo (HASTE) images. Diffusion weighted imaging (DWI) images were done using two b-value sets (0, 1000 and 50, 400, 800). Largest possible regions of interest (ROI) were drawn over the placenta and ADC values were correlated with gestational-age and Gg using linear regression and Kruskal-Wallis, respectively. Results: There were 11, 18, 9, 0 patients with normal looking placentas with Gg of 0, 1, 2, and 3 respectively. ADC values obtained from b values of 0, and 1000 show a significant correlation with gestational-age (R2 = 0.60, P = 0.000) and Gg (P = 0.004) respectively, while ADC values obtained from b values of 50, 400, and 800 did not show significant correlation with gestational age (R2 = 0.087, P = 0.073) or Gg (P = 0.236). Conclusion: ADC values which were obtained from sets of b values of 0 and 1000 correlated with placental maturity (both gestational age (GA) and Grannum grades). This can be attributed to lower b-values covering the microperfusion in addition to diffusion characteristics of the tissue.