Multi-centre Investigation of Cardiac Diffusion Tensor Imaging in Healthy Volunteers by SCMR Cardiac Diffusion Special Interest Group NETwork (SIGNET).

Background: Cardiac diffusion tensor imaging (cDTI) is an emerging technique for microstructural characterization of the heart and has shown clinical potential in a range of cardiomyopathies. However, there is substantial variation reported for in vivo cDTI results across the literature, and sensitivity of cDTI to differences in imaging sites, scanners, acquisition protocols and post-processing methods remains incompletely understood.

Methods: SIGNET is a prospective multi-centre, observational study in travelling and non-travelling healthy volunteers.

Is regional atrial strain a useful surrogate of regional atrial fibrosis in atrial cardiomyopathy?

Aims: To determine whether atrial biomechanics measured using 3D regional strain, left atrial volume (LAV), and left atrial emptying fraction (LAEF) are associated with atrial fibrosis in patients with suspected atrial cardiomyopathy.

Methods And Results: Cardiovascular magnetic resonance (CMR) was performed in atrial fibrillation (AF) patients ( = 47). Healthy volunteer ( = 41) and familial dilated cardiomyopathy (DCM) ( = 31) cohorts were acquired for normalization and validation, respectively.

Multi-Shot Diffusion Imaging Using Motion Compensation Diffusion Encoding Waveforms and EPI With Keyhole.

Motion-induced shot-to-shot phase variation and strong image aliasing artifacts are common in diffusion weighted imaging (DWI) multi-shot EPI (MS-EPI). Herein, motion-compensated diffusion encoding waveforms were used to minimize shot-to-shot phase variation, and an MS-EPI with Keyhole (MS-EPIK) trajectory was evaluated to mitigate image aliasing. MS-EPI and MS-EPIK with non-motion compensated (M), first order (MM), and first & second order (MMM) motion-compensated diffusion encoding waveforms and a reference single-shot (SS-EPI) acquisition with M diffusion encoding were acquired in vivo at 3T in five volunteers in the brain, liver, and heart.

Experiments and Simulations to Assess Exercise-Induced Pressure Drop Across Aortic Coarctations.

Blood pressure gradient (ΔP) across an aortic coarctation (CoA) is an important measurement to diagnose CoA severity and guide treatment. While invasive cardiac catheterization is the clinical gold-standard for measuring ΔP, it requires anesthesia and does not capture the effects of daily activity or exercise, potentially underestimating the disease's functional burden. This study aimed to identify patients with functionally significant CoA by evaluating exercise-induced ΔP using a hybrid mock circulatory loop (HMCL).

Comprehensive Analysis of Relative Pressure Estimation Methods Utilizing 4D-Flow MRI.

Magnetic resonance imaging (MRI) can estimate three-dimensional (3D) time-resolved relative pressure fields using 4D-flow MRI, thereby providing rich pressure field information. Clinical alternatives include catheterization and Doppler echocardiography, which only provide one-dimensional pressure drops. The accuracy of one-dimensional pressure drops derived from 4D-flow has been explored previously, but additional work is needed to evaluate the accuracy of 3D relative pressure field estimates.

DENSE-SIM: A modular pipeline for the evaluation of cine displacement encoding with stimulated echoes images with sub-voxel ground-truth strain.

Background: Myocardial strain is a valuable biomarker for diagnosing and predicting cardiac conditions, offering additional prognostic information to traditional metrics such as ejection fraction. While cardiovascular magnetic resonance (CMR) methods, particularly cine displacement encoding with stimulated echoes (DENSE), are the gold standard for strain estimation, evaluation of regional strain estimation requires precise ground truth. This study introduces DENSE-SIM, an open-source simulation pipeline for generating realistic cine DENSE images with high-resolution known ground-truth strain, enabling evaluation of accuracy and precision in strain analysis pipelines.

Characterizing variability in passive myocardial stiffness in healthy human left ventricles using personalized MRI and finite element modeling.

Abnormal passive stiffness of the heart muscle (myocardium) is evident in the pathophysiology of several cardiovascular diseases, making it an important indicator of heart health. Recent advancements in cardiac imaging and biophysical modeling now enable more effective evaluation of this biomarker. Estimating passive myocardial stiffness can be accomplished through an MRI-based approach that requires comprehensive subject-specific input data.

Left Ventricular Twist and Circumferential Strain from MRI Tagging Predict Early Cardiovascular Disease in Duchenne Muscular Dystrophy.

Duchenne Muscular Dystrophy (DMD) is a prevalent fatal genetic disorder, and heart failure is the leading cause of mortality. Peak left ventricular (LV) circumferential strain (E), twist, and circumferential-longitudinal shear angle (θ) are promising biomarkers for the improved and early diagnosis of incipient heart failure. Our goals were as follows: 1) to characterize a spectrum of functional and rotational LV biomarkers in boys with DMD compared with healthy age-matched controls; and 2) to identify LV biomarkers of early cardiomyopathy in the absence of abnormal LVEF or LGE.

An axis-specific mitral annuloplasty ring eliminates mitral regurgitation allowing mitral annular motion in an ovine model.

Introduction: Current mitral annuloplasty rings fail to restrict the anteroposterior distance while allowing dynamic mitral annular changes. We designed and manufactured a mitral annuloplasty ring that demonstrated axis-specific, selective flexibility to meet this clinical need. The objectives were to evaluate ex vivo biomechanics of this ring and to validate the annular dynamics and safety after ring implantation in vivo.

Motion-Compensated Multishot Pancreatic Diffusion-Weighted Imaging With Deep Learning-Based Denoising.

Objectives: Pancreatic diffusion-weighted imaging (DWI) has numerous clinical applications, but conventional single-shot methods suffer from off resonance-induced artifacts like distortion and blurring while cardiovascular motion-induced phase inconsistency leads to quantitative errors and signal loss, limiting its utility. Multishot DWI (msDWI) offers reduced image distortion and blurring relative to single-shot methods but increases sensitivity to motion artifacts. Motion-compensated diffusion-encoding gradients (MCGs) reduce motion artifacts and could improve motion robustness of msDWI but come with the cost of extended echo time, further reducing signal.

MRI-Based Circumferential Strain in Boys with Early Duchenne Muscular Dystrophy Cardiomyopathy.

In boys with Duchenne muscular dystrophy (DMD), cardiomyopathy has become the primary cause of death. Although both positive late gadolinium enhancement (LGE) and reduced left ventricular ejection fraction (LVEF) are late findings in a DMD cohort, LV end-systolic circumferential strain at middle wall (E) serves as a biomarker for detecting early impairment in cardiac function associated with DMD. However, E derived from cine Displacement Encoding with Stimulated Echoes (DENSE) has not been quantified in boys with DMD.

Assessing the Impact of Cardiac Output and Valve Orientation on Bioprosthetic Pulmonary Valve Hemodynamics Using In Vitro 4D-Flow MRI and High-Speed Imaging.

Purpose: Pulmonary valve replacement (PVR) using bioprosthetic valves is a common procedure performed in patients with repaired Tetralogy of Fallot and other conditions, but these valves frequently become dysfunctional within 15 years of implantation. The causes for early valve failure are not clearly understood. The purpose of this study was to explore the impact of changing cardiac output (CO) and valve orientation on local hemodynamics and valve performance.

Cardiac diffusion-weighted and tensor imaging: A consensus statement from the special interest group of the Society for Cardiovascular Magnetic Resonance.

Thanks to recent developments in cardiovascular magnetic resonance (CMR), cardiac diffusion-weighted magnetic resonance is fast emerging in a range of clinical applications. Cardiac diffusion-weighted imaging (cDWI) and diffusion tensor imaging (cDTI) now enable investigators and clinicians to assess and quantify the tridimensional microstructure of the heart. Free-contrast DWI is uniquely sensitized to the presence and displacement of water molecules within the myocardial tissue, including the intracellular, extracellular, and intravascular spaces.

Phase contrast MRI with minimized background phase errors.

Purpose: Phase contrast MRI (PC-MRI) is used clinically to measure velocities in the body, but systematic background phase errors caused by magnetic field imperfections corrupt the velocity measurements with offsets that limit clinical utility. This work aims to minimize systematic background phase errors in PC-MRI, thereby maximizing the accuracy of velocity measurements.

Methods: The MRI scanner's background phase errors from eddy currents and mechanical oscillations were modeled using the gradient impulse response function (GIRF).

Design and implementation of a cost-effective, open-source, and programmable pulsatile flow system.

The primary objective of this research was to design, implement, and validate a programmable open-source pulsatile flow system to cost-effectively simulate vascular flows. We employed an Arduino-compatible microcontroller combined with a motor driver to control a centrifugal direct current (DC) motor pump. The system was programmed to produce pulsatile flows with an arterial pulse waveform.

SDF4CHD: Generative modeling of cardiac anatomies with congenital heart defects.

Congenital heart disease (CHD) encompasses a spectrum of cardiovascular structural abnormalities, often requiring customized treatment plans for individual patients. Computational modeling and analysis of these unique cardiac anatomies can improve diagnosis and treatment planning and may ultimately lead to improved outcomes. Deep learning (DL) methods have demonstrated the potential to enable efficient treatment planning by automating cardiac segmentation and mesh construction for patients with normal cardiac anatomies.

Phase stabilization with motion compensated diffusion weighted imaging.

Purpose: Diffusion encoding gradient waveforms can impart intra-voxel and inter-voxel dephasing owing to bulk motion, limiting achievable signal-to-noise and complicating multishot acquisitions. In this study, we characterize improvements in phase consistency via gradient moment nulling of diffusion encoding waveforms.

Methods: Healthy volunteers received neuro ( ) and cardiac ( ) MRI.

A deep learning approach for fast muscle water T2 mapping with subject specific fat T2 calibration from multi-spin-echo acquisitions.

This work presents a deep learning approach for rapid and accurate muscle water T with subject-specific fat T calibration using multi-spin-echo acquisitions. This method addresses the computational limitations of conventional bi-component Extended Phase Graph fitting methods (nonlinear-least-squares and dictionary-based) by leveraging fully connected neural networks for fast processing with minimal computational resources. We validated the approach through in vivo experiments using two different MRI vendors.

Pre-excitation gradients for eddy current nulled convex optimized diffusion encoding (Pre-ENCODE).

Purpose: To evaluate the use of pre-excitation gradients for eddy current-nulled convex optimized diffusion encoding (Pre-ENCODE) to mitigate eddy current-induced image distortions in diffusion-weighted MRI (DWI).

Methods: DWI sequences using monopolar (MONO), ENCODE, and Pre-ENCODE were evaluated in terms of the minimum achievable echo time (TE ) and eddy current-induced image distortions using simulations, phantom experiments, and in vivo DWI in volunteers ( ).

Results: Pre-ENCODE provided a shorter TE than MONO (71.

Non-invasive Estimation of Pressure Drop Across Aortic Coarctations: Validation of 0D and 3D Computational Models with In Vivo Measurements.

Blood pressure gradient ( ) across an aortic coarctation (CoA) is an important measurement to diagnose CoA severity and gauge treatment efficacy. Invasive cardiac catheterization is currently the gold-standard method for measuring blood pressure. The objective of this study was to evaluate the accuracy of estimates derived non-invasively using patient-specific 0D and 3D deformable wall simulations.

Hemodynamic effects of entry and exit tear size in aortic dissection evaluated with in vitro magnetic resonance imaging and fluid-structure interaction simulation.

Understanding the complex interplay between morphologic and hemodynamic features in aortic dissection is critical for risk stratification and for the development of individualized therapy. This work evaluates the effects of entry and exit tear size on the hemodynamics in type B aortic dissection by comparing fluid-structure interaction (FSI) simulations with in vitro 4D-flow magnetic resonance imaging (MRI). A baseline patient-specific 3D-printed model and two variants with modified tear size (smaller entry tear, smaller exit tear) were embedded into a flow- and pressure-controlled setup to perform MRI as well as 12-point catheter-based pressure measurements.

SDF4CHD: Generative Modeling of Cardiac Anatomies with Congenital Heart Defects.

Congenital heart disease (CHD) encompasses a spectrum of cardiovascular structural abnormalities, often requiring customized treatment plans for individual patients. Computational modeling and analysis of these unique cardiac anatomies can improve diagnosis and treatment planning and may ultimately lead to improved outcomes. Deep learning (DL) methods have demonstrated the potential to enable efficient treatment planning by automating cardiac segmentation and mesh construction for patients with normal cardiac anatomies.