Background:Imaging evaluation of the placenta is of prime importance in evaluation of IUGR. This has conventionally been performed with ultrasound, and more recently with MRI. To our knowledge, however, DWI of the normal placenta has seldom been studied.
Objectives:In this study, we aim to correlate ADC values of the normal placenta with Grannum classification.
Patients and Methods:From December 2010 to December 2011, 66 pregnant mothers with normal ultrasound and MRI (with the exception of borderline ventriculomegaly), and no evidence of IUGR at time of ultrasound were referred for fetal MRI (indications including borderline ventriculomegaly and family history of anomalies). After excluding patients who did not provide consent, technically inadequate images and mothers who gave birth to small for gestational age fetuses, 38 mothers with singleton malignancies were enrolled into the study. In addition to the usual fetal MRI sequences including the HASTE images, two sets of DWI images with b values of 0,1000 and b = 50,400,800 were obtained. ADC values were calculated using manual free-hand ROI drawn over the largest visible placenta. ADC values were correlated with Grannum classification using Kruskal-Wallis test. Also the ADC values obtained from the two sets of ADC values (b = 0, 1000 and b = 50,400,800) correlated with the gestational age using linear regression.
Results:ADC values obtained from b values of 0,1000 show significant correlation with gestational age using linear regression (P = 0.000), however, the ADC values obtained from the b values of 50,400,800, failed to show statistically significant correlation with GA (P = 0.076). Also ADC values obtained from b values of 0,1000 show significant correlation with Grannum classification using Kruskal-Wallis (P = 0.004) while the ADC values obtained from the b values of 50,400,800 failed to show statistically significant correlation with Grannum class (P = 0.236). Using linear regression analysis, ADC values obtained from b values of 0, 1000 show a better fit correlated with gestational age (R = 0.60) than the ADC values obtained from b values of 50,400,800 (R = 0.087).
Conclusions:Various sets of b values result in ADC values with various degrees of correlation with Granuum classification and gestational age. Comparing the two sets of b value in our study, the set including b = 0 resulted in a better fit both with gestational age and with Granuum classification.
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