Keywords: Cardiovascular, Heart

Motivation: Interventional cardiac MRI (iCMR) can be used to guide catheterizations, but image quality is limited by real-time imaging constraints (acquisition/reconstruction times).  

Goal(s): To evaluate the extent to which real-time multi-shot imaging (via adaptive radial k-space sampling, ARKS) improves iCMR image quality relative to single-shot imaging.  

 

Approach: Both ARKS and golden angle radial sampling were simulated using pediatric ECG recordings. Image quality was evaluated via mean squared error (MSE) and structural similarity index metric (SSIM). 

Results: ARKS increases the number of samples available for reconstruction, relative to single shot imaging with the same temporal footprint. This led to lower MSE and higher SSIM.

Impact: Multi-shot real-time imaging has the potential to significantly improve interventional imaging by increasing the amount of data available for image reconstruction. In this study, we demonstrate that combining multi-shot data can improve image quality. 

Keywords: Cardiovascular, Cardiovascular

Motivation: 4D Flow Assessment for Reconstruction Right Ventricular Outflow Tract in Congenital Heart Disease Patients: New Hemodynamic Insights for Handmade Three-Valve Goretex Conduit

Goal(s): 1) evaluate pulmonary valve regurgitation and the patency of the Goretex conduit using 4D flow CMR compare with controls. 2) assess the variation of advanced hemodynamic parameters of 2D axial WSS, 2D circumference WSS and EL in Gortex conduit.

Approach:   The CMR data was acquired from 12 healthy participants and 17 patients who were performed cine sequence in routine chamber view and 4D flow.

Results:  Hemodynamic changes were detected in patients with right ventricular outflow tract reconstruction.

Impact: Further long-term evaluation is necessary for the changes in segmental WSS in MPA.

Keywords: Cardiovascular, Pediatric, Multidimensional Flow Imaging

Motivation: In the absence of injected contrast agent, the quality of magnitude data from traditional 4D flow techniques can be poor, making structural visualization and blood vessel segmentation challenging.

Goal(s): Slice-to-volume 4D flow data has inherently high signal in blood vessels owing to in-flow effects. We apply slice-to-volume 4D flow in pediatric patients and evaluate its accuracy.

Approach: 7 pediatric patients were imaged with slice-to-volume 4D flow. Dynamic magnitude reconstructions and angiograms were assessed. The flow accuracy was evaluated using traditional 2D phase contrast MRI.

Results: Slice-to-volume 4D flow provided accurate flow quantification along with high quality anatomical and angiographic visualisations without contrast injection.

Impact: Volumetric flow imaging was performed using slice-to-volume 4D flow in pediatric patients. The technique provided accurate flow quantification along with high quality anatomical and angiographic visualisations without contrast injection.

Keywords: Cardiovascular, Data Acquisition, congenital heart disease, morphology, function

Motivation: 3D dual-phase whole-heart MRI has shown advantage for simultaneous morphological and functional cardiac imaging but is so far not available at 3.0T due to bSSFP susceptibility artifacts and specific absorption rate limitation at high field.

Goal(s): Our goal was to develop a new sequence to circumvent the problems and allow 3D dual-phase whole-heart MRI for high-field cardiac imaging.

Approach: We implemented an interleaved cardiac-triggered acquisition with non-balanced readout and applied it in patients with congenital heart disease at 3.0T.

Results: 3D dual-phase whole-heart MRI at 3.0T successfully depicted morphological and functional changes within one single scan in concordance with standard techniques.

Impact: 3D isotropic dual-phase whole-heart MRI with interleaved ECG-triggered acquisition and non-balanced readout now permits visualization and assessment of cardiac morphology and function with high resolutions within one single scan at 3.0T and promises wider clinical applications in congenital heart disease.

Keywords: Cardiovascular, Blood vessels

Motivation: Signal loss in non-contrast-enhanced thoracic MRI due to off-resonance artifacts precludes evaluation of pulmonary vessels, particularly in children with complex/turbulent flows at high field.

Goal(s): Our goal was to restore the signal and reduce artifacts for improved visualization of pulmonary vessels at 3.0T.

Approach: We introduced a T2prep pulse with 16 composite refocusing pulses “MLEV16” with shorter refocusing interval and applied it in patients with congenital heart disease at 3.0T, in comparison to standard T2prep pulse using MLEV4.

Results: Visualization of the pulmonary vessels was clearly improved using the MLEV16 pre-pulse compared to standard MLEV4 T2prep at 3.0T.

Impact: Non-contrast-enhanced thoracic MRI with MLEV16 pre-pulse for T2 preparation permits improved visualization of pulmonary vessels for clinical evaluation, a primary need in areas where pediatric congenital heart disease is common and high-field MRI at 3.0T becomes more accessible.

Keywords: Cardiovascular, Cardiomyopathy, Dilated cardiomyopathy; late gadolinium enhancement

Motivation: The prognostic value of late gadolinium enhancement (LGE) in adult dilated cardiomyopathy (DCM) has been confirmed, but its prognostic value in children with DCM remains unclear.

Goal(s): To evaluate the prognostic value of late LGE in children with DCM. 

Approach: This retrospective single-center study analyzed 76 children with DCM. The composite endpoint was all-cause mortality, heart transplant, and rehospitalization for heart failure. The risk factors for the composite endpoint were identified with multivariable Cox analysis.

Results: Multivariable Cox analysis showed that LGE present was associated with the composite endpoints (hazard ratio [HR], 2.59 [95% CI: 1.05, 6.37], p=0.039).

Impact:  Late gadolinium enhancement of CMR in children with DCM provides independently prognostic value of all-cause mortality, heart transplant, and rehospitalization for heart failure.

Keywords: Cardiovascular, Cardiomyopathy

Motivation: Duchenne muscular dystrophy (DMD) leads to pediatric cardiomyopathy. Pre-contrast T1 in DMD identifies myocardial remodeling, but it remains unclear if T1-Mapping biomarkers can detect longitudinal changes in DMD.

Goal(s): The objective was to characterize progressive myocardial pre-contrast T1 changes in DMD at 3T.

Approach: Boys with DMD and healthy controls underwent a 3T CMR exam that included standard functional and pre-contrast T1 mapping sequences. Boys with DMD were examined at two points (18 months apart). 

Results: Pre-contrast T1 was capable of detecting progressive changes in boys with DMD 18 months post baseline while functional metrics like LVEF did not.

Impact: T1 Mapping biomarkers can detect disease progression in DMD. T1 Mapping biomarkers, in combination with biomarkers of function have the potential to track patient-specific changes. 

Keywords: Flow, Surgery, Congenital heart disease

Motivation: The descending aorta (DAo) in patients with hypoplastic left heart syndrome (HLHS) after Norwood procedure is frequently enlarged although this region is not subject to surgical procedures.

Goal(s): The aim of this study is to investigate whether the aortic anatomy can cause abnormal flow patterns which are related to vascular alterations. 

Approach: Based on anatomic models and flow boundaries from 4D flow MRI, we studied fluid-dynamics using CFD simulations. 
 

Results: We found increased vorticity and wall-shear stress in the HLHS descending aorta. Increased wall shear stress has been associated with the development of dilation and may explain vascular alterations in the descending aorta.

Impact: This study gives motivation for further investigations and may ultimately lead to future Norwood procedure modifications.

Keywords: Flow, Vessels

Motivation: Aortic coarctation (COA) is a congenital heart disease that induces harmful structural cardiovascular changes. Operations to address COA have varying outcomes, leaving uncertainty as to whether maladaptive processes can be altered. Despite repair, patients have an increased risk of early cardiovascular morbidity and mortality.

Goal(s): To utilize 4D Flow MRI to monitor and study the vascular biomechanics of aortic coarctation in a porcine model

Approach: In this pilot study, a porcine model of aortic coarctation was developed and underwent serial 4D flow MRI scans.

Results: Treatment did not significantly alter quantitative metrics of aortic flow, velocity or collateralization

Impact: 4D Flow MRI provides a non-invasive method to evaluate a novel porcine model of aortic coarctation with resultant functional metrics that provide insight into the significant early remodeling and lack of early treatment efficacy in this patient population.

Keywords: Heart Failure, Cardiovascular

Motivation: The triad of pulmonary hypoplasia, pulmonary hypertension, and early cardiac dysfunction has been postulated to be responsible for poor postnatal outcomes in congenital diaphragmatic hernia repair (CDH). 

Goal(s): This study was aimed to investigate whether MRI markers of cardiac dysfunction are associated with clinical outcomes in neonates after CDH.

Approach: In this prospective study neonates after CDH repair underwent 3T cardiac MRI. Biventricular function/volumes, end-diastolic/end-systolic volumes, shunt fraction were assessed.  The study cohort was binarized based on median RVEF (cutoff >54%) to compare clinical variables and outcome data between two groups.

Results: MRI-derived parameters of RV-dysfunction were associated with short-term clinical outcomes. 

Impact: Cardiac MRI allows for objective and early assessment of cardiac dysfunction and, hence, might play an important role in risk stratification and clinical decision-making in neonates after CDH repair.

Keywords: Cardiovascular, Pediatric, Cardiac Implantable Electronic Devices, Real-Time Cine, Wideband, Pulse Sequence, Perfusion, LGE

Motivation: Cardiac MRI is rarely performed in children with cardiac implantable electronic devices (CIED) due to safety concerns and image artifacts.

Goal(s): To determine the clinical utility of wideband cardiac, real-time MRI methods in children with an implantable pulse generator (IPG). 

Approach: We performed free-breathing real-time cine, wideband late gadolinium enhancement (LGE) and perfusion in 18 healthy children with IPG taped to below the left clavicle and abdomen to mimic endocardial and epicardial systems, respectively.

Results: Compared to the standard, wideband sequences effectively suppressed image artifacts, and produced relatively accurate quantification of bi-ventricular functional metrics.

Impact: Wideband cardiac, real-time pulse sequences are effective in reducing image artifacts induced by an IPG, thereby increasing the potential benefit of cardiac MRI in children with CIEDs.

Keywords: Fetal, Low-Field MRI, Fetal Cardiac MRI

Motivation: Low field MRI at 0.55T offers advantages such as increased field homogeneities for fetal cardiac MRI and early diagnosis of congenital heart diseases (CHDs) but required careful optimization specific to the properties of low field.

Goal(s): This study aimed to optimize the bSSFP sequence parameters at 0.55T to compensate for the reduced SNR and improve diagnostic capabilities in fetal cardiac MRI.

Approach: Phantom experiments and in-utero studies were conducted to evaluate the impact of optimized parameters of bSSFP sequences on SNR, image quality, and clinical applicability.

Results: The optimized bSSFP sequence parameters demonstrate increased SNR and good visualization of cardiac structures.

Impact: The optimized bSSFP sequence at 0.55T has the potential to be used at low field strengths to prenatally diagnose congenital heart disease, thereby increasing accessibility for patients.

Keywords: Fetal, Fetus

Motivation: To allow diagnosis of CHD at low field strengths in order to increase the accessibility of MRI.

Goal(s): To demonstrate that acquiring 2D phase contrast sequences in utero at 0.55T is possible. 

Approach: Acquire 2D Phase contrast sequences, optimize sequences parameters, and perform metric optimized gating and flow measurements

Results: Umbilical vein, descending aorta, and superior vena cava flow in utero measurements were calculated.

Impact: Fetal flow measurements provide additional information on the complex hemodynamics in complex CHD cases – potentially enhancing antenatal counselling and postnatal surgery planning.  Optimizing these for emerging low field MRI scanners widens their availability.

Keywords: Prenatal, Fetus

Motivation: A novel pipeline for the creation of 3D fetal whole-heart datasets has been devised by combining Doppler US-gating and slice-to-volume registration. 

Goal(s): Our goal was to perform initial validation of the resultant 3D+t datasets.

Approach: We assessed for internal consistency by deriving fetal stroke volume data from two methods in six subjects. Stroke volume data were obtained through volumetric analysis of the 3D+t volume alongside assessment of paired 2D+t phase-contrast flow data.

Results: There was correlation between volumetrically derived stroke-volume data with that derived from 2D+t phase contrast flow, however the volumetric method was biased toward lower readings.

Impact: Initial validation of a novel pipeline for the creation 3D fetal whole-heart datasets shows correlation between stroke volumes derived from volumetry and phase contrast flow data. Future work will explore the bias toward lower stroke volumes obtained by volumetry.

Keywords: Flow, Fetus, 4D flow

Motivation: Small blood vessel size relative to spatial resolution in fetal 4D flow MRI makes segmentation and flow quantification difficult. 

Goal(s): To quantify blood flow from fetal 4D flow using black blood imaging-based segmentation and to compare hemodynamic results to 4D flow-only approach. We hypothesize black blood will provide better flow delineation for complex anatomies. 

Approach: The great vessels were segmented from 4D flow and black blood for volunteers and coarctation cases; flow volumes were compared after alignment of segmentations.

Results: Black blood underestimated flow volume but captured vessel geometry and flow features 4D flow segmentation missed in several cases of coarctation.

Impact: While the combination of black blood imaging and fetal 4D flow did not offer flow quantification comparable to conventional 4D flow approach, its potential of capturing coarctation flow may assist prenatal diagnosis of coarctation, which is challenging solely with ultrasound. 

Keywords: Fetal, Fetus, 4D flow

Motivation: Fetal 4D flow provides useful information related to cardiovascular structure and function, but its reliability is not yet defined.

Goal(s): Here, we seek to define the accuracy, precision, internal consistency, and repeatability of fetal 4D flow.

Approach: Pregnant women in their third trimester with healthy developing fetuses (N=22) and fetuses with suspected cardiovascular anomalies (N=12) were scanned with 2D phase contrast and 4D flow sequences. Quantitative flow metrics were compared.

Results: 4D flow underestimated net flow in the great vessels relative to 2D-PC, but had reasonable precision, internal consistency, and repeatability. Fetal 4D flow can reliably measure percentage contributions from various vascular territories.

Impact: Fetal 4D flow allows for quantitative hemodynamic evaluation of the fetal cardiovascular system with good precision, internal consistency, and repeatability. Flow was underestimated relative to 2D-PC, therefore presently percent contribution from various vascular territories is the most appropriate clinical endpoint.