Fetal Hemodynamics, Early Survival, and Neurodevelopment in Patients With Cyanotic Congenital Heart Disease.

Background: Fetuses with cyanotic congenital heart disease (CHD) exhibit profound fetal circulatory disturbances that may affect early outcomes.

Objectives: This study sought to investigate the relationship between fetal hemodynamics and early survival and neurodevelopmental (ND) outcomes in patients with cyanotic CHD.

Methods: In this longitudinal observational study, fetuses with cyanotic CHD underwent late gestational fetal cardiovascular magnetic resonance (CMR) to measure vessel blood flow and oxygen content.

An MRI approach to assess placental function in healthy humans and sheep.

Key Points: Human placental function is evaluated using non-invasive Doppler ultrasound of umbilical and uterine artery pulsatility indices as measures of resistance in placental vascular beds, while measurement of placental oxygen consumption ( ) is only possible during Caesarean delivery. This study shows the feasibility of using magnetic resonance imaging (MRI) in utero to measure blood flow and oxygen content in uterine and umbilical vessels to calculate oxygen delivery to and by the gravid uterus, uteroplacenta and fetus. Normal late gestational human uteroplacental by MRI was ∼4 ml min  kg fetal weight, which was similar to our MRI measurements in sheep and to those previously measured using invasive techniques.

Normal human and sheep fetal vessel oxygen saturations by T2 magnetic resonance imaging.

Key Points: Human fetal Doppler ultrasound and invasive blood gas measurements obtained by cordocentesis or at the time of delivery reveal similarities with sheep (an extensively used model for human fetal cardiovascular physiology). Oxygen saturation (SO ) measurements in human fetuses have been limited to the umbilical and scalp vessels, providing little information about normal regional SO differences in the fetus. Blood T2 MRI relaxometry presents a non-invasive measure of SO in the major fetal vessels.

Simulation of semilunar valve function: computer-aided design, 3D printing and flow assessment with MR.

Background: The structure of the valve leaflets and sinuses are crucial in supporting the proper function of the semilunar valve and ensuring leaflet durability. Therefore, an enhanced understanding of the structural characteristics of the semilunar valves is fundamental to the evaluation and staging of semilunar valve pathology, as well as the development of prosthetic or bioprosthetic valves. This paper illustrates the process of combining computer-aided design (CAD), 3D printing and flow assessment with 4-dimensional flow magnetic resonance imaging (MRI) to provide detailed assessment of the structural and hemodynamic characteristics of the normal semilunar valve.

The utility of MRI for measuring hematocrit in fetal anemia.

Background: Doppler ultrasound measurements of the peak systolic velocity of the middle cerebral artery can be used to noninvasively diagnose fetal anemia but are less precise following fetal blood transfusion and in late gestation. We have previously demonstrated the feasibility of estimating fetal hematocrit in vitro using magnetic resonance imaging relaxation times. Here we report the use of magnetic resonance imaging as a noninvasive tool to accurately detect fetal anemia in vivo.

Magnetic Resonance Imaging: A New Tool to Optimize the Prediction of Fetal Anemia?

Introduction: The false-positive rate in the prediction of fetal anemia is 10-15%. We investigated if a new, noninvasive MRI method used as a supplement to ultrasound could improve the prediction.

Methods: Fetuses suspected of anemia and controls were scanned in a 1.

New advances in fetal cardiovascular magnetic resonance imaging for quantifying the distribution of blood flow and oxygen transport: Potential applications in fetal cardiovascular disease diagnosis and therapy.

Until recently, our modern understanding of fetal circulatory physiology has been largely based on invasive measurements made in fetal sheep. However, new MRI technology developed by our group has provided equivalent information about the distribution of blood flow and oxygen transport noninvasively. The initial findings largely confirm prior estimates about the human fetal circulation extrapolated from fetal sheep data and human ultrasound data.

Human umbilical cord blood relaxation times and susceptibility at 3 T.

Purpose: To characterize the magnetic susceptibility and relaxation times (T and T ) of fetal blood at 3 T as a function of the hematocrit (Hct) and oxygen saturation (sO ).

Methods: Susceptibility and relaxometry measurements were performed on cord blood specimens (N = 90, derived from six caesarean deliveries) with a range of hematocrits and oxygen saturations (0.09 < Hct < 0.

Non-invasive evaluation of blood oxygen saturation and hematocrit from T and T relaxation times: In-vitro validation in fetal blood.

Purpose: We propose an analytical method for calculating blood hematocrit (Hct) and oxygen saturation (sO ) from measurements of its T and T relaxation times.

Theory: Through algebraic substitution, established two-compartment relationships describing R1=T1-1 and R2=T2-1 as a function of hematocrit and oxygen saturation were rearranged to solve for Hct and sO in terms of R and R . Resulting solutions for Hct and sO are the roots of cubic polynomials.

Functional and anatomical evidence of cerebral tissue hypoxia in young sickle cell anemia mice.

Cerebral ischemia is a significant source of morbidity in children with sickle cell anemia; however, the mechanism of injury is poorly understood. Increased cerebral blood flow and low hemoglobin levels in children with sickle cell anemia are associated with increased stroke risk, suggesting that anemia-induced tissue hypoxia may be an important factor contributing to subsequent morbidity. To better understand the pathophysiology of brain injury, brain physiology and morphology were characterized in a transgenic mouse model, the Townes sickle cell model.

Relaxation properties of human umbilical cord blood at 1.5 Tesla.

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

Methods: Relaxometry measurements were performed on cord blood specimens (N = 88, derived from six caesarean deliveries) spanning a broad range of hematocrits (Hct = 0.

The hemodynamics of late-onset intrauterine growth restriction by MRI.

Background: Late-onset intrauterine growth restriction (IUGR) results from a failure of the placenta to supply adequate nutrients and oxygen to the rapidly growing late-gestation fetus. Limitations in current monitoring methods present the need for additional techniques for more accurate diagnosis of IUGR in utero. New magnetic resonance imaging (MRI) technology now provides a noninvasive technique for fetal hemodynamic assessment, which could provide additional information over conventional Doppler methods.

Magnetic resonance microscopy of human and porcine neurons and cellular processes.

With its unparalleled ability to safely generate high-contrast images of soft tissues, magnetic resonance imaging (MRI) has remained at the forefront of diagnostic clinical medicine. Unfortunately due to resolution limitations, clinical scans are most useful for detecting macroscopic structural changes associated with a small number of pathologies. Moreover, due to a longstanding inability to directly observe magnetic resonance (MR) signal behavior at the cellular level, such information is poorly characterized and generally must be inferred.

An efficient interlaced multi-shell sampling scheme for reconstruction of diffusion propagators.

In this paper, we propose an interlaced multi-shell sampling scheme for the reconstruction of the diffusion propagator from diffusion weighted magnetic resonance imaging (DW-MRI). In standard multi-shell sampling schemes, sample points are uniformly distributed on several spherical shells in q-space. The distribution of sample points is the same for all shells, and is determined by the vertices of a selected polyhedron.

BOX SPLINE BASED 3D TOMOGRAPHIC RECONSTRUCTION OF DIFFUSION PROPAGATORS FROM MRI DATA.

This paper introduces a tomographic approach for reconstruction of diffusion propagators, ( ), in a box spline framework. Box splines are chosen as basis functions for high-order approximation of ( ) from the diffusion signal. Box splines are a generalization of B-splines to multivariate setting that are particularly useful in the context of tomographic reconstruction.

Comparative SNR for high-throughput mouse embryo MR microscopy.

MR microscopy is being explored as a useful imaging tool to phenotype mouse embryos due to its volume coverage with three-dimensional isotropic resolution. However, the main limitation for mouse embryo MR microscopy is the signal-to-noise ratio. Large numbers of embryos are needed for phenotypic screening, making high throughput essential.

Dimensions of the human sclera: Thickness measurement and regional changes with axial length.

Scleral thickness, especially near the region of the optic nerve head (ONH), is a potential factor of interest in the development of glaucomatous optic neuropathy. Our goal was to characterize the scleral thickness distribution and other geometric features of human eyes. Eleven enucleated human globes (7 normal and 4 ostensibly glaucomatous) were imaged using high-field microMRI, providing 80 microm isotropic resolution over the whole eye.

Modeling pulsed magnetization transfer.

Modeling the effects of clinical magnetization transfer (MT) scans, which generate contrast using short, shaped radiofrequency (RF) pulses (pulsed MT), is complex and time-consuming. As a result, several studies have proposed approximate methods for a simplified analysis of the experimental data. However, potential differences in the MT parameters estimated by each method may complicate the comparison of reported results.