Keywords: Heart Failure, Myocardium, pulmonary hypertension; electromechanical discoordination;

Motivation: Non-invasive and accurate evaluation of right ventricular (RV) function in pulmonary arterial hypertension (PAH) is of urgent need in clinical practice.

Goal(s): To investigate the clinical implications of RV electromechanical dyssynchrony which were non-invasively derived from cardiac MRI.

Approach: Calculate systolic stretch fraction (SSF) and diastolic relaxation fraction (DRF) based on strain MRI and test their prognostic values in an observation prospective PAH cohort.

Results: SSF-RV-Longitudinal could independently predict the clinical worsening.

Impact: The present study first reported SSF-RV-Longitudinal as a novel parameter to evaluate RV function, which could predict the clinical worsening in PAH patients.

Keywords: Arrhythmia, Arrhythmia, atrial fibrillation, 3D LGE, fibrosis, signature

Motivation: Left atrial fibrosis assessment from 3D LGE-MRI is pivotal for predicting atrial myopathy and AF recurrence. However, current methods are clinically ineffective and sensitive to data uncertainties such as noise and inter-observer variability of thin LA wall segmentation

Goal(s): Hence, we propose a novel, robust, and standardized probabilistic 3D LGE fibrosis signature technique for quantifying fibrosis burden. 

Approach: Our threshold-free signature technique  probabilistically encodes multi-billion LGE intensity comparisons from the entire LA volume (not just LA wall).

Results: We evaluated feasibility of our threshold-free method in quantifying LA fibrosis burden, and its stability against Rician noise and interobserver variability of LA volume segmentation.

Impact: Our signature technique as an index of fibrosis burden is highly robust to inherent scan uncertainties including high power Rician noise and inter-observer LA segmentation variability. As a result, our method increases potential clinical utility of 3D LGE MRI 

Keywords: Myocardium, Heart

Motivation: Patients with repaired Tetralogy of Fallot (rTOF) have varied cardiac structures, yet there's a current lack of analysis on their cardiac kinetic energy.

Goal(s): We aim to assess myocardial kinetic energy (KE) differences between patients and normal groups.

Approach: We utilized tissue phase mapping images combined with MATLAB programs to calculate myocardial kinetic energy.

Results: The results revealed differences in myocardial kinetic energy values between patients and normal groups. Besides, significant variations were observed in the proportional values across three directions, along with notable differences in the KE systolic-to-diastolic ratio of the right ventricle.

Impact: Differential myocardial kinetic energy serves as a novel indicator for evaluating cardiac function in rTOF patients. It aids in early detection of cardiac abnormalities, potentially identifying the optimal timing for pulmonary valve replacement surgery.

Keywords: Myocardium, Heart, cardiac diffusion, Motion compensated gradients, Aliasing, geometric distortion, PROPELLER MRI

Motivation: We aimed to enhance in vivo cardiac diffusion tensor imaging (cDTI), a technique challenged by limitations, especially in high-BMI patients, causing notable aliasing and distortion issues.

Goal(s): Our primary goal was to introduce and validate Short-Axis-PROPELLER-M2-EPI (SAP-M2-EPI) for cDTI. The focus was on reducing aliasing and distortion artifacts while ensuring robust motion correction.

Approach: SAP-M2-EPI combines motion-compensated diffusion gradients with PROPELLER, effectively minimizing motion artifacts and suppressing aliasing and distortion.
 

Results: Our study shows that SAP-M2-EPI successfully mitigates motion artifacts and significantly reduces aliasing and distortion, particularly beneficial for high-BMI patients. This innovative approach holds great promise for enhancing cDTI diagnostic accuracy.

Impact: Impact: SAP-M2-EPI’s success offers clinicians a potent tool for enhancing cDTI diagnoses, especially in high-BMI patients. It opens doors to in-depth cardiac research, encourages further methodological innovations, and ultimately promises better patient care through more accurate imaging.

Keywords: Myocardium, Cardiovascular

Motivation: Prolonged scan times in high-resolution 3D late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) imaging hinders the full potential in clinical applications.  

Goal(s): The primary goal of this study was to develop and evaluate a 3D enhanced-resolution for 2D (k_y-k_z) accelerated 3D LGE imaging. 

Approach: A 3D generative adversarial network was implemented to enhance the spatial resolution of 2D-accelerated 3D LGE images.

Results: The proposed method at 6-fold acceleration (3-fold in k_y and 2-fold in k_z) maintained intricate scar details and improved image quality.

Impact: The improvement in acquisition speed by 2D acceleration may benefit patients presenting with heavy respiratory motion and may be less sensitive to contrast washout. 

Keywords: Myocardium, Magnets (B0)

Motivation: Diffusion tensor cardiovascular magnetic resonance (DT-CMR) studies described in the literature have almost uniquely been performed at 3T while 1.5T scanners are more widely available.

Goal(s): To compare the performance and microstructural parameters available from stimulated echo (STEAM) and motion compensated spin echo (MCSE) DT-CMR sequences at 1.5T and 3T.

Approach: DT-CMR was performed in 20 healthy volunteers using both sequences at both field strengths at peak systole and end diastole.

Results: MCSE and STEAM sequences are effective at both 1.5T and 3T. STEAM benefits from the increased SNR available at 3T.

Impact: DT-CMR studies should consider making use of 1.5T hardware where access to 3T scanners is more difficult particularly where MCSE sequences are to be used with systolic triggering.

Keywords: Myocardium, Heart

Motivation: Machine learning algorithms provide a means to uncover hidden patterns within complex and heterogeneous datasets.

Goal(s): We aimed to identify phenogroups among patients with β-thalassemia major (TM) using an unsupervised clustering approach based on demographic, clinical, and CMR data.

Approach: We considered 356 β-TM patients who underwent MR for the assessment of iron overload, biventricular function and atrial, and replacement myocardial fibrosis.

Results: We identified three mutually exclusive phenogroups characterized by different biventricular function parameters and frequency of replacement myocardial fibrosis and by a different prospective risk of cardiovascular complications.

Impact: In TM, unsupervised clustering integrating routinely measured CMR parameters conveys the potential to significantly impact patient care and improve cardiovascular outcomes by enabling early detection of cardiac remodeling and damage, as well as improved risk stratification.  

Keywords: Myocardium, Metabolism

Motivation: Metabolic alterations associated with a ketogenic diet (KD) include suppressed carbohydrate utilization in the myocardium, but how quickly they recover by reverting to a normal diet (ND) is under-investigated.

Goal(s): This study investigates recuperation dynamics of myocardial pyruvate oxidation by reverting a KD to a ND.

Approach: Cardiac metabolism of healthy rats was longitudinally assessed using hyperpolarized [1-¹³C]pyruvate at baseline, during a KD, and a subsequent ND after the 5-week KD.

Results: Cardiac [¹³C]bicarbonate disappeared with a KD. Reverting to ND gradually recovered the PDH flux over eight days. [1-¹³C]Lactate production in the KD group showed the opposite but similar dynamic patterns.

Impact: Compensating the metabolic shifts by a ketogenic diet is challenged for proper assessment of cardiac metabolism and is often attempted by temporarily reverting the diet. Understanding the recuperation dynamics is crucial in proper assessment of cardiac metabolism.

Keywords: Myocardium, Myocardium, motion compensation, gradient moment nulling

Motivation: Cardiac diffusion tensor imaging (cDTI) based on spin-echo employs up to 2^nd order (M2) motion compensated diffusion gradients. It is unclear whether higher order motion compensation would be beneficial.

Goal(s): To evaluate the impact of higher order motion compensation (i.e. velocity, acceleration, jerk, snap, crackle and pop) in cDTI.

Approach: Diffusion gradient waveforms with M1 to M6 motion compensation were designed and implemented in a prospective study of healthy volunteers. Mean diffusivity and fractional anisotropy maps were quantitatively evaluated.

Results: Significant reductions in MD and MD heterogeneity were observed in the M6 relative to M2 compensated data.

Impact: We demonstrate the potential importance of compensating for higher orders of motion (>M2) in cardiac diffusion MRI. This work may inform gradient waveform design for more accurate and robust cardiac diffusion MRI.

Keywords: Myocardium, Heart, Cardiac CINE, free-running, water-fat separation, phase sensitive, fat suppression

Motivation: Water-fat separated (WFS) imaging can improve detection and characterization of various cardiovascular pathologies. We hypothesize that the signal phase at half the repetition time of balanced steady-state free precession (bSSFP) may be used for efficient WFS cine imaging.

Goal(s): To study the feasibility of WFS free-running 3D cardiac cine imaging using the phase-sensitive approach.

Approach: After reconstruction of 5D whole heart images, the global slowly varying phase was estimated and removed. Water and fat voxels were then identified according to the phase.

Results: Water and fat were sufficiently separated around the heart. A field map of off-resonance can partially mitigate peripheral water/fat swaps.

Impact: A phase sensitive approach for WFS only requires negligible computational cost and minor adjustment of repetition time. It might be implemented with a wide range of bSSFP cine imaging techniques for fat suppression or to provide complementary water/fat information. 

Keywords: Heart Failure, Heart, Cardiovascular; Acquisition Methods; Analysis/Processing

Motivation: Routine cardiac function assessment uses breath-held 2D cine imaging. Self-gated free-running sequences have recently been proposed to simplify the workflow. However, at 3T, GRE-based sequences require contrast agents to achieve blood-myocardium contrast.

Goal(s): This study introduced a contrast-agent-free acquisition for assessing cardiac anatomy and function at 3T.

Approach: Based on an interrupted free-running sequence, the proposed approach integrates T₂ preparation and recovery modules to optimize blood-to-myocardium-contrast. A compressed-sensing-based reconstruction was used to generate 5D images of the whole heart.

Results: The framework was validated in 11 healthy volunteers, where it demonstrated slightly lower contrast but enabled effective left-ventricle segmentation and exhibited high reproducibility. 

Impact: The proposed study introduces a contrast-agent-free method for a comprehensive 5D assessment of cardiac anatomy and function at 3T in a 5-minute acquisition. Demonstrating high agreement with the routine method, this approach holds promise for enhancing the overall patient management.

Keywords: Myocardium, Cardiovascular, ischemia, deep-learning, strains, remodelling, function

Motivation: To perform a retrospective analysis of the anatomical and functional remodelling of left ventricles 4 and 12 months after the ischemic event. 

Goal(s): To assess differences in remodelling between patients with recovered function and those without.

Approach: A deep-learning framework was developed to fit a statistical shape model to all cardiac phases of each patient and compute strains, valve motion and morphological descriptors.

Results: Peak strain values and valve displacements at 4 and 12 months show different trends between patients with recovered function and those without. Peak-systolic shapes of patients with positive remodelling show a lower sphericity with respect to the others. 
 

Impact: A deep learning framework reveals that relative changes in peak systolic anatomical shapes, radial and circumferential strains and valve motion after 4 months could provide a discriminator for predicting positive remodelling and restoration of functionality in patient with heart failure.

Keywords: Myocardium, Electromagnetic Tissue Properties, electrical properties, conductivity, parametric mapping, cardiac, EPT

Motivation: While electrical property tomography is gaining popularity, cardiac applications are limited due to inadequate cardiac B₁⁺ mapping. Thus, conductivity mapping in the heart using complex B₁⁺ maps is yet unexplored.

Goal(s): To measure myocardial conductivity from the complex B₁⁺ distribution in the heart at 3T.

Approach: A novel |B₁⁺| mapping method was adapted for free-breathing B₁⁺ maps, followed by conductivity reconstruction via 1D polynomial fitting in saline phantoms and four healthy subjects.

Results: Phantom results show excellent correlation with expected values (R²=0.95). In-vivo, conductivity is largely homogenous with 0.69±0.13S/m average in-plane conductivity across all subjects, in line with the literature.

Impact: Electrical properties are a valuable biomarker, however, the translation to cardiac imaging remains limited. In this work, complex B₁⁺ field-based conductivity is reported in the human myocardium at 3T, using a novel Bloch-Siegert shift-prepared cardiac B₁⁺ mapping technique.

Keywords: Myocardium, Heart

Motivation: Cardiac MRI has become the gold standard for non-invasive characterization of myocardial tissue. However, current MRI techniques only indirectly represent cardiac inflammation.

Goal(s): To assess if interventional molecular MRI allows for visualization of the cellular processes during the inflammatory response after myocardial infarction.

Approach: Iron-labeled P-selectin contrast agent was injected in pigs after 40 minutes of myocardial ischemia. To increase sensitivity, the contrast agent was injected into the coronary artery via an MR-guided intervention.

Results: Infarcted myocardial segments could be visualized using the iron-labeled contrast agent by increased R2* values both in vivo and ex vivo.

Impact: The intracoronary injection of molecular contrast agents using interventional MRI can add valuable information for preclinical studies of the early cellular processes after myocardial ischemia.

Keywords: Heart Failure, Cardiovascular

Motivation: Whether obese subjects with no clinical signs or comorbidities have diastolic dysfunction is unclear.

Goal(s): We non-invasively assess diastolic function in adults with uncomplicated obesity and evaluate its association with fat distribution. 

Approach: Left atrial (LA) and left ventricular (LV) strain and volume-time curve using cardiac magnetic resonance were compared.

Results: The obese patients had impaired diastolic function, manifested as lower LV diastolic strain rates and peak filling rate index and declined LA reservoir and conduit function compared with controls. Central fat has a negative association while peripheral fat has a positive association on diastolic function. 

Impact: CMR-derived feature tracking and volume-time curve non-invasively detected subclinical diastolic dysfunction in early adult obesity with preserved LVEF. This study also suggests that recognizing the role of different areas of fat on the heart may be beneficial for obese patients. 

Keywords: Myocardium, Quantitative Imaging, Kawasaki disease

Motivation: Kawasaki Disease (KD) is recognized for cardiac and coronary arterial impact, however its influence on the liver remains underexplored, especially in pediatric patients.

Goal(s): Use T1 mapping to quantitatively evaluate cardiac-hepatic involvement and myocardial fibrosis in KD patients.

Approach: Using a 3T MR scanner, T1 mapping was conducted on the heart and liver of 115 KD patients and 40 controls, with myocardial fibrosis being diagnosed through LGE.

Results: KD patients displayed elevated cardiac and hepatic T1 values in both acute and chronic phases compared to controls. These values, in combined with sodium levels, were effective in identifying myocardial fibrosis in KD patients.

Impact: This study demonstrated T1 mapping was a noninvasive tool for the comprehensive assessment of cardiac-hepatic involvement and myocardial fibrosis in KD patients. 

Keywords: Myocardium, Fat

Motivation: Combined bright- and black-blood late gadolinium enhancement has shown potential for scar detection.However, accurate differentiation between scar and fat tissue in these images can pose a challenge.

Goal(s): To assess the SPOT-Dixon sequence, a joint bright- and black- blood methodology in combination with a two-point Dixon approach to improve myocardial scar detection and delineation.

Approach: The proposed sequence was tested in 13 patients with suspected cardiovascular diseases and the results were compared to those from reference sequences.

Results: The SPOT-Dixon sequence was able to reliably delineate scar tissue within the myocardium and differentiate it from fat in its proximity.

Impact: The proposed sequence combining the SPOT sequence and a two-point Dixon method gives reliable images of the myocardial scar and the fat tissue surrounding it, providing a valuable diagnostic advantage and potentially improving the accuracy of cardiovascular assessments.