Diffusion-Weighted Imaging in Fetuses with Severe Congenital Heart Defects

Case Reports

Three women were referred for MR imaging of the fetal brain after prenatal sonography showed congenital cardiac anomalies. All fetal brain MR imaging was performed as part of a study on CHD, which was approved by our institutional review board. Case 1 was a fetus at 32.14 weeks' gestational age at MR imaging with sonographic evidence of transposition of the great arteries, mild hydronephrosis, and a small cystic neck mass. T1- and T2-weighted imaging findings of the fetal brain were normal. Case 2 was a fetus at 34.57 weeks' gestational age with a hypoplastic left heart and mild pelviectasis on prenatal sonography. No abnormalities were evident on T1- or T2-weighted MR images. Case 3 was a fetus at 35.29 weeks' gestational age with a hypoplastic left heart identified on prenatal sonography. Fetal MR imaging demonstrated a hypoplastic corpus callosum. In Cases 1 and 2, a neonatal MR imaging was also performed, which demonstrated a normal appearance of the brain.

Diffusion-weighted imaging was performed on a 1.5T scanner with a b-value of 600 s/mm² applied in 3 orthogonal directions in addition to a single b = 0 s/mm² volume. Imaging parameters were TR = 4500 ms, TE = minimum, FOV = 32 × 32 cm, section thickness = 5 mm, and matrix = 128 × 128. To minimize motion artifacts, we acquired diffusion images during a maternal breath-hold. All acquired echo-planar images and the calculated ADC maps were visually examined, and those degraded by motion were excluded. Regions of interest were placed in the periatrial WM, thalamus, and basal ganglia, and ADC values were measured.

Fetuses with CHD were compared with a previously reported control fetal population comprising 28 fetuses with basal ganglia measurements, 33 fetuses with periatrial WM measurements, and 28 fetuses with thalamic measurements.⁴ The control population's gestational age at the time of the MR imaging ranged from 21 to 34 weeks. Statistical comparisons between the control population and the 3 fetuses with CHD were made with linear regression, including ADC and gestational age as variables. In addition, z scores of the individual patient measurements were calculated to determine their deviation from the control data.

ADC values in the periatrial WM and thalamus were higher for all fetuses with CHD compared with the control population (Fig 1). The average z score was 1.26 for the periatrial WM, 1.38 for the thalamus, and 0.40 for the basal ganglia (Fig 2). Regression analysis indicated a significant difference between patient and control thalamic ADC values (P < .05) and a strong trend not reaching significance between patient and control periatrial WM ADC values (P = .071). Patient and control basal ganglia ADC values were not significantly different (P = .53).

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Fig 1.

Three fetuses with congenital heart disease (diamonds) are compared with a control cohort (solid dots). The regression line was fit to the control population.

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Fig 2.

Z scores of individual ADC measurements in fetuses with CHD show deviation from the control population. A negative z score indicates that the ADC measurement was below the expected value from the control population.