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Objectives To compare the diagnostic usefulness of high-field with low-field magnetic resonance imaging (MRI) and stereomicroscopic autopsy for examination of the heart in fetuses at or under 20 weeks' gestation. Methods Prior to invasive stereomicroscopic autopsy, MRI scans at 9.4, 3.0 and 1.5 T were performed on 24 fetuses between 11 and 20 weeks' gestation, including 10 fetuses with cardiac abnormalities. The ability to visualize different heart structures was evaluated according to the different field strength MRI magnets used and gestational age at examination. Results On 1.5- and 3.0-T MRI, only the heart situs and four-chamber view could be visualized consistently (in 75% or more of cases) when the fetus was beyond 16 weeks' gestation, but other heart structures could not be visualized for fetuses at any gestational age. In contrast, using high-field MRI at 9.4 T, the heart situs, four-chamber view and the outflow tracts could be visualized in all fetuses irrespective of gestational age. Using high-field MRI, the sensitivity for detecting an abnormality of the four-chamber view was 66.7% (95% CI, 30.1-92.1%) with a specificity of 80.0% (95% CI, 51.9-95.4%). For abnormalities of the outflow tracts, sensitivity was 75.0% (95% CI, 20.3-95.9%) and specificity 100.0% (95% CI, 83.3-100.0%). Eight fetuses out of 10 with congenital heart disease (CHD) were classified as having major CHD. High-field MRI at 9.4 T was able to identify seven out of the eight cases of major CHD. Conclusion High-field MRI at 9.4 T seems to be an acceptable alternative approach to invasive stereomicroscopic autopsy for fetuses with CHD at or below 20 weeks' gestation. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Objective To ascertain whether high-field magnetic resonance imaging (MRI) allows accurate estimation of the weight of various fetal organs at postmortem before 20 weeks' gestation. Methods From 23 fetuses at 9-20 weeks, following termination of pregnancy or in-utero fetal death (IUFD), 207 assorted fetal organs were evaluated by high-field MRI at 9.4 T prior to conventional autopsy. Fetal organ density was calculated by correlating volume and weight at autopsy using linear regression analysis, and this was used to estimate fetal organ weight by MRI. The relative error in MRI estimation of organ weight was calculated as follows: (|MRI weight − autopsy weight|/autopsy weight) × 100 (%). Multiple regression analysis was used to investigate the effect on the relative error of MRI organ weight estimates of gestational age at TOP or delivery following IUFD, autopsy weight, fetal organ examined, IUFD and fetal maceration. Results Of the 207 organs evaluated, 133 (64%) were examined for fetal organ density and 155 (75%) for fetal organ weight. Fifty-two organs were excluded from our analysis; 41 of these were from fetuses with IUFD, with 39 organs macerated. In 32 cases, exclusion was due to an inability to assess the organ both on MRI and on conventional autopsy. Volume and weight at autopsy correlated significantly, following the linear equation: autopsy volume = (0.9947 × autopsy weight) − 4.7556, where autopsy volume is in mm3 and weight is in mg ( r = 0.99, P < 0.001). Overall the mean relative error in the MRI estimation of organ weight was 68%. Multiple regression analysis showed that the relative error in the MRI estimation of organ weight was significantly associated with gestational age at TOP or delivery following IUFD and fetal maceration, but not with autopsy weight, fetal organ examined or IUFD. In the subgroup of non-macerated organs and for fetuses above 14 weeks' gestation, the mean relative error in the MRI estimation of organ weight was 34%. Conclusion In fetuses before 20 weeks' gestation, noninvasive estimation of organ weight is feasible using high-field MRI, but there is a mean overestimation. Limitations of the technique occur mainly in cases of small macerated fetuses before 14 weeks' gestation. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]