Magnetic resonance diffusion-weighted imaging: reproducibility of regional apparent diffusion coefficients for the normal fetal brain

Abstract

Objective: To evaluate the reproducibility of regional apparent diffusion coefficient (ADC) measurements of the normal fetal brain in the second and third trimesters of pregnancy.

Methods: Fifty normal singleton fetuses from healthy pregnant women between 19 and 37 weeks' gestation were studied without sedation. Single-shot diffusion-weighted images of the fetal brain were obtained using a 1.5-Tesla magnetic resonance scanner and a six-channel body array coil. ADC maps were created using 0 and 1000 b-values along three orthogonal directions. Two examiners independently measured ADC values in the cerebellar hemispheres (CH), pons, thalamus, basal ganglia (BG), centrum semiovale (CSO), and frontal (FWM), parietal (PWM), temporal (TWM) and occipital (OWM) white matter. Correlation between ADC values and menstrual age was assessed by linear regression analysis. The bias and agreement of ADC measurements were determined using Bland-Altman plots.

Results: ADC values either remained constant (BG, FWM, PWM, TWM, OWM, CSO) or decreased (CH, pons, thalamus) with advancing menstrual age. Mean intraobserver bias for ADC measurements was not significantly different from zero. Small interobserver differences in mean ADC measurements (i.e. a small mean bias) were detected for CH (1.26 ± 0.20 vs 1.20 ± 0.18 μm(2) /ms, P = 0.006), PWM (1.37 ± 0.29 vs 1.33 ± 0.26 μm(2) /ms, P = 0.02) and CSO (1.36 ± 0.29 vs 1.33 ± 0.28 μm(2) /ms, P < 0.0001). Measurement agreement was acceptable.

Conclusions: ADC measurements in normal unsedated fetuses in the second and third trimesters are reproducible except for small differences for PWM, CH and CSO between examiners.

Copyright © 2013 ISUOG. Published by John Wiley & Sons, Ltd.

Figures

Figure 1

Regions of interest (ROI) for fetal brain ADC measurements. Multiple axial ADC images from a fetal brain at 22.7 gestational weeks demonstrating sample ROI placement within the basal ganglia (a), pons (b), thalamus (c), centrum semiovale (d), frontal and parietal white matter (e), occipital white matter (f), temporal white matter (g), and cerebellar hemispheres (h).

Figure 2

Correlation between ADC values and menstrual age for different fetal brain regions: a) basal ganglia; R2=0.01; b) thalamus; R2=0.17; c) frontal white matter; R2=0.01; d) cerebellar hemispheres; R2=0.23; e) pons; R2=0.18; f) occipital white matter; R2=0.05, g) parietal white matter; R2=0.05, h) temporal white matter; R2=0.02, i) and centrum semiovale; R2=0.06. A significant menstrual agerelated decline in ADC values was observed in the pons, thalamus, and cerebellar hemispheres (p

Figure 3

Intra-observer bias and agreement for regional fetal brain ADC measurements. Intra-observer bias was not significantly different from zero. Intra-observer LOA ranged from −9.0 to 15.6%.

Figure 4

Inter-observer bias and agreement for regional fetal brain ADC measurements. Inter-observer LOA ranged from −8.4 to 18.8% Small differences in inter-observer bias were detected for cerebellar hemispheres (1.26 ± 0.20 vs. 1.20 ± 0.18, p = 0.006), parietal white matter (1.37 ± 0.29 vs. 1.33 ± 0.26, p = 0.02), and centrum semiovale (1.36 ± 0.29 vs. 1.33 ± 0.28, p