Meng Yuan Zhu

Relaxation properties of human umbilical cord blood at 1.5 Tesla

To characterize the MRI relaxation properties of human umbilical cord blood at 1.5 Tesla.

Fetal haemodynamic assessment in a case of late-onset intrauterine growth restriction by phase contrast MRI and T2 mapping

Background Late-onset intrauterine growth restriction (IUGR) results from the failure of placenta to supply enough nutrients and oxygen to the rapidly growing late gestation fetus [1]. Inaccuracies in ultrasound based late gestational fetal weight estimation and the absence of typical Doppler changes make late-onset IUGR difficult to detect [2]. We were interested in whether new MRI technology incorporating fetal vessel blood flow and oximetry measurement could improve the sensitivity of conventional fetal monitoring.

Reduced combined ventricular output and increased oxygen extraction fraction in a fetus with complete heart block demonstrated by MRI

Meng Yuan Zhu, MS, Edgar Jaeggi, MD, Christopher W. Roy, MSc, Christopher K. Macgowan, PhD, Mike Seed, MBBS From the Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada, Division of Cardiology, Hospital for Sick Children, Toronto, Ontario, Canada, and Department of Physiology and Experimental Medicine, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.

Feasibility of phase-contrast cine magnetic resonance imaging for measuring blood flow in the sheep fetus

Phase-contrast cine MRI (PC-MRI) is the gold-standard non-invasive technique for measuring vessel blood flow and has previously been applied in the human fetal circulation. We aimed to assess the feasibility of using PC-MRI to define the distribution of the fetal circulation in sheep. Fetuses were catheterized at 119-120 days gestation (term, 150 days) and underwent MRI at 123 days gestation under isoflurane anesthesia, ventilated at a FiO2 of 1.0. PC-MRI was performed using a fetal arterial blood pressure catheter signal for cardiac triggering. Blood flows were measured in the major fetal vessels, including the main pulmonary artery, ascending and descending aorta, superior vena cava, ductus arteriosus, left and right pulmonary arteries, umbilical vein, ductus venosus, and common carotid artery; and were indexed to estimated fetal weight. The combined ventricular output, pulmonary blood flow and flow across the foramen ovale were calculated from vessel flows. Intra-observer, inter-observer agreement and reproducibility were assessed. Blood flow measurements were successfully obtained in 61 out of 74 vessels (82.4%) interrogated in 9 fetuses. There was good intra-observer (R=0.998, P<0.0001; ICC=0.997) and inter-observer agreement (R=0.996, P<0.0001; ICC=0.996). Repeated MRI measurements showed good reproducibility (R=0.989, P=0.0002; ICC=0.990). We conclude that PC-MRI using fetal catheters for gating triggers is feasible in the major vessels of late gestation fetal sheep. This approach may provide a useful new tool for assessing the circulatory characteristics of fetal sheep models of human disease, including fetal growth restriction and congenital heart disease.

EP15.17: Fetal brain to liver volume ratio measured by MRI is a useful indicator of IUGR in vivo in late gestation.

Objectives: To assess whether the frequency of fetal facial expressions observed by 4D ultrasound and HDlive can be used as an auxiliary diagnostic measure for prenatal evaluation of fetal brain and central nervous system. Methods: Women who were at 26 weeks or later of gestation and were scheduled to be admitted to or take regular prenatal visits at our hospital were asked to participate in 15-minute observations of fetal facial expressions by 4D HDlive ultrasound on Voluson E10. Normally developing singleton pregnancies and fetal growth restriction (FGR) counterparts were scanned. Each of the examinations was saved on local archive. After examinations, the quantity of seven types of fetal facial expressions such as blinking, mouthing, yawning, tongue expulsion, sucking, smiling and scowling was assessed. Kruskal-Wallis one-way analysis of variance by ranks test was used for comparison of facial expression frequencies of each group. The non-parametric Wilcoxon rank-sum test was applied if statistically significant differences could be shown in facial expression frequencies between two groups. Results: Eight fetuses (normal: 6, FGR: 2) were enrolled in the study to compare the frequencies of facial expressions. No statistically significant difference was seen in facial expression frequencies between two groups, though we noted a tendency for FGR fetuses to have less facial expressions than normal fetuses especially such as mouthing and smiling. In normal group, the commonest facial expression was mouthing and was significantly more frequent than blinking and sucking. Conclusions: FGR fetuses may seem to have less facial expressions than normal fetuses in our experience, although there was no statistically significant difference. We continue this study and the promising results could encourage the use of 4D HDlive ultrasound for neurobehavioral evaluation as detailed examination of the neurological condition in FGR fetuses.

Combined ventricular output and oxygen delivery are reduced while oxygen extraction fraction is increased in fetuses with Ebstein's Anomaly by MRI

Results We studied 30 normal and 8 EA fetuses at 36 weeks gestation. There were 2 deaths in the 4 patients that underwent surgery (all Starnes procedures). We found reduced flows in all measured vessels except ascending aorta (Table 1). There were also significant reduced T2s in ascending aorta and superior vena cava, but no difference in umbilical vein (UV) and descending aorta (Table 1). DO2 was lower, but increases in OEF maintained normal VO2 in EA fetuses (Table 2). Fetal weight and brain weight were lower in EA fetuses, while lung volume was not significantly different (Table 2). Within the EA group, UV flow (P = 0.04), VO2 (P < 0.0001) and lung volume (P = 0.03) were significantly higher in EA newborns not requiring surgery than EA newborn that received surgery.

Serial prenatal and post-natal brain MRI demonstrates impact of congenital heart disease and cardiac surgery on brain growth and maturity

Methods Post-natal brain MRI were performed without sedation in 24 infants with common CHD before and after the cardiac surgery on a Siemens Avanto 1.5T system (Erlangen) after hospital IRB approval. 18 of 24 subjects also had fetal MRI using previously described technique [5] and BV and fetal weight were calculated [3]. The normal brain weights were obtained from published autopsy data [6] and converted to BV [7]. T2 mapping and diffusion weighted imaging were performed to measure T2 and apparent diffusion coefficient (ADC), respectively [2]. The mean T2 and ADC were measured in postnatal brains using 12 regions of interest located bilaterally at frontal and posterior white matter (WM) at inferior basal ganglia level; superior frontal and parietal WM at level of horns of lateral ventricles; and frontal and posterior centrum semiovale level. Cerebral oxygen delivery (CDO2) was also measured [1]. The daily change in BV, T2, and ADC were calculated by dividing the difference in values by days between the scans. The correlation between BV, T2, and ADC was examined using Pearson’s Correlation. Results The cohort (n = 24) consisted of patients with transposition of the great arteries (TGA) with intact ventricular septum (IVS; n = 5); TGA with ventricular septal defect (VSD; n = 7), hypoplastic left heart syndrome (HLHS; n = 4); tricuspid atresia (TA; n = 5), pulmonary atresia (PA, n = 3). The TGA/IVS group had normal brain growth after birth and surgery (Figure 1A). However, in TGA/VSD patients, the brain growth plateaus or drops after birth and do not revert immediately after surgery (Figure 1B). TGA/VSD had lower daily brain growth compared to normals (Figure 1C). HLHS showed similar decline in BV after surgery (Figure 1D). The infants with TA and PA had normal BV growth. The mean T2 and ADC values had excellent correlation (r = 0.96, p < 0.0001; Figure 2A). T2 (r=-0.79, p < 0.0001) and ADC (r=-0.7, p < 0.0001) also correlated with BV. Children with TGA physiology showed opposite change in T2 and ADC to expected values (Figure 2B). The mean CDO2/ml of brain was relatively lower in TGA/VSD (4 ml O2/min/ml BV; n = 3) compared to TGA/IVS (6 ml O2/min/ml BV; n = 3).

The absolute and relative sizes of the brains and bodies of fetuses with different forms of congenital heart disease and intrauterine growth restriction

Background Congenital heart disease(CHD) is associated with in utero brain dysmaturation, abnormal cerebral vasculature and decreased brain size.(1,2) Intrauterine growth restriction is associated with increased relative brain size, smaller birth weight and neurological impairment later in life.(3) A large cohort of CHD and IUGR fetuses allows for more definitive study as to the extent these conditions effect the absolute and relative sizes of the brain and body.