Keywords: Myocardium, Cardiovascular, Contrast Mechanism, ihMT

Motivation: Imaging the cardiac conduction system (CCS) remains a significant challenge, since no imaging modalitiy has so far provided good contrast between the cardiac muscle and the embedded fibers that regulate normal heartbeat.

Goal(s): We aim to address this challenge by employing inhomogeneous Magnetization Transfer Imaging (ihMT).

Approach: We hypothesise that the conductive fibers exhibit unique dipolar order properties, due to the collagen sheath that surrounds them, and could thus be selectively isolated by ihMT.

Results: As a first step towards enhancing muscle-to-fiber contrast, this work investigated the biophysical parameters that govern the ihMT signal in the macromolecular environment of the CCS.

Impact: The assessment of the macromolecular environment of the cardiac conduction system (CCS) allows for a better understanding of its morphological architecture, and will enable us to design an ihMT sequence specifically sensitive to the challenging morphology of the CCS.

Keywords: Arrhythmia, Precision & Accuracy, cardiac and respiratory self-gating

Motivation: ECG-gating for cardiac MR Imaging may fail, especially at high field, and the conventional self-gating method is insufficient to effectively extract the cardiac signal in 3D cardiac MR cine with high precision (previous precision 20-30ms).

Goal(s): Our goal was to achieved a reliable cardiac self-gating technique with the precision of 10ms level.

Approach: We proposed a two-step selective PCA self-gating method by first selecting the heart beating or respiration sensitive points and then performing PCA.

Results: The proposed method achieved a temporal precision of 11ms for 3D cardiac cine images.

Impact: The proposed selective PCA self-gating technique can be applied in poor ECG-gating MR scans, such as patients with hairy chests or obesity, as well as in high-field environments, with a high level of precision down to 11ms.

Keywords: Arrhythmia, Arrhythmia, Fibrosis

Motivation: The impact of vendors and threshold methods on quantification of LA fibrosis is not well studied.

Goal(s): To evaluate the inter-vendor and inter-threshold impact on LA fibrosis quantification.

Approach: Both packages of Medis and CVI⁴² ADAS were used to calculate LA fibrosis based on the image IIR 1.2-method and 2 SD above the mean blood pool signal intensity of LA.

Results: The both post-processing software packages of Medis and CVI⁴² ADAS have a good agreement and correlation to quantify LA fibrosis if an identical quantification method was used. However, LA fibrotic burden is influenced by used quantification methods.

Impact: LA fibrotic burden quantified with cardiac MRI is influenced by used quantification methods, but don’t dependent on vendors. The use of Utah stages by other centers needs further validation when different analysis methods applied.

Keywords: Arrhythmia, Magnetization transfer

Motivation: The architecture of the cardiac conduction system is implicated in cardiac arrhythmias such as ventricular fibrillation and characterizing this structure will help better understand and diagnose these arrhythmias.

Goal(s): Optimizing the inhomogeneous magnetization transfer technique for 3D imaging of conducting fibers.

Approach: A range of parameters for ihMTRARE sequence were explored for imaging samples from sheep’s left ventricles containing free-running Purkinje fibers and myocardium.

Results: Across samples, ihMTR signal was found consistently higher in fibers compared to the myocardium for the chosen saturation parameters. This finding holds promise for future 3D imaging of the cardiac conduction system.

Impact: The results of this study hold promise for future 3D imaging of larger samples of the left ventricle containing free-running and intramural Purkinje fibers using the optimized sequence which would allow the segmentation and characterization of these fibers.

Keywords: Arrhythmia, Arrhythmia

Motivation: Irregular cardiac motion can degrade image quality and preclude the use of conventional segmented cine MRI for quantitative evaluation of cardiac function. And it can be difficult for some patients to do multiple breath holds. 

Goal(s): To evaluate a cluster-based algorithm and reconstruction approach for cine MRI in patients with atrial fibrillation under free-breathing condition.

Approach: Ten atrial fibrillation patients were scanned under breath-held and free-breathing conditions. Image quality, SNR, CNR, and edge sharpness were assessed. 

Results: No significant difference in image quality scores, SNR, CNR, and edge sharpness were found for images obtained under breath-held and free-breathing conditions. 

Impact: Adaptive cluster-based motion binning with temporal total variation reconstruction is effective at handling irregular cardiac motion and enables high quality, free-breathing cine MRI in patients with atrial fibrillation.   

Keywords: Arrhythmia, Arterial spin labelling, Atrial Fibrillation

Motivation: Cerebral hypoperfusion may be a major link between atrial fibrillation (AF) and neuropathologic processes. Whether catheter ablation can effectively improve cerebral perfusion needs to be evaluated  by noninvasive methods.

Goal(s): To assess the effects of catheter ablation on overall and regional cerebral blood perfusion in AF patients using multi-delay ASL.

Approach: Multi-delay ASL was performed before and after catheter ablation to calculate arterial transit time and cerebral blood flow. Whole and regional cerebral perfusion parameters before and after ablation were characterized and compared in paroxysmal and non-paroxysmal groups.

Results: Cather ablation significantly increased overall and regional cerebral blood perfusion, especially in non-paroxysmal AF.

Impact: Catheter ablation can improve cerebral perfusion and maintain brain health, which should be considered even in asymptomatic patients. Multi-delay ASL can be used to evaluate and monitor cerebral perfusion in AF and help with patient screening and therapeutic strategy development.

Keywords: Arrhythmia, Arrhythmia, CMR,4D FLOW

Motivation: A novel imaging method was developed to diagnose children with premature ventricular contractions (PVCs), thereby preventing heart failure or cardiomyopathy.

Goal(s): To determine the changes in the blood flow composition of LV in children with PVCs, a free breathing 4D flow CMR was performed. The relationship of PVC load with LV function was explored.

Approach: The children with PVCs underwent 24-hour dynamic ECG and CMR examination within 3 days. Thus, we determined their cardiac function and hemodynamic parameters.

Results: Children with PVCs had reduced direct blood flow in LV, which showed a significant negative correlation with PVC load.

Impact: In this study, we analyzed the characteristics of the left ventricular blood flow in children with premature ventricular contractions (PVCs). Thereafter, we elucidated the pathophysiological mechanism of PVCs, which provided the basis for clinical treatment and prognostic evaluation.

Keywords: Arrhythmia, MR-Guided Interventions, Arrhythmia, Low-field MRI

Motivation: The 12-lead ECG is the standard diagnostic for monitoring rhythm and ischemia during stress. ECG distortion via magnetohydrodynamic effect is proportional to field strength and limits interpretation at 1.5T and 3T. Lower field (0.55T) offers potential improvement.

Goal(s): Compare variability in ECGs in at 0.55T, 1.5T and 3.0T and examine changes in ECG morphology at 0.55T in response to ischemia and exercise stress.

Approach: ECGs were recorded in: (1) swine at three fields, and at 0.55T during ischemia, and (2) normal human subjects a and during ergometer stress.

Results: At 0.55T ECGs remained interpretable at isocenter though some distortion due to MHD persisted.

Impact: Low field (0.55T) MRI can provide improved clinical interpretation of 12-Lead ECGs at isocenter due to reduction of magnetohydrodynamic distortion and reduced sensitivity to patient motion as demonstrated in swine with cardiac ischemia and humans undergoing exercise induced stress.

Keywords: Arrhythmia, Arrhythmia, Atrial fibrillation (AF); Cardiac magnetic resonance (CMR); Three-dimensional late gadolinium enhancement (3D-LGE); Left atrial fibrosis (LAF)

Motivation: Left atrial (LA) function and structural remodeling in atrial fibrillation (AF) remains uncertain in the context of LA-CMR.

Goal(s): To investigate the effectiveness of 3D-LGE CMR and LA-strain techniques for assessing LA fibrosis in paroxysmal or persistent AF (PaAF, PeAF) patients.

Approach: Preoperative CMR was used to analyze LA-strain parameters. Quantitative assessments of LA wall enhancement utilized the Infarct-to-Interstitial Ratio (IIR) as a reference.

Results: Contrasted with PaAF, those with PeAF exhibited increased LA volumes, reduced LA function, and lower strain values. In 3D-LGE sequences, PeAF patients demonstrated more extensive myocardial enhancement, scar tissue, and interstitial fibrosis in comparison to PaAF patients.

Impact: Our research provides a promising imaging tool for the management of AF patients, with potential translational applications focused on quantitatively and visually assessing LA function and structural remodeling, personalizing treatment, assisting intraoperative navigation, and enabling long-term monitoring. 

Keywords: Arrhythmia, Visualization

Motivation: Standard ECG-gated breath-held (BH) cine MRI often produces non-diagnostic image quality in CIED patients who have a high burden of arrhythmia. 

Goal(s): The goal of this study is to produce diagnostic images using a free-breathing real-time cine MRI for those patients.  

Approach: We proposed a new pulse sequence to meet our goal. 

Results: Our proposed pulse sequence produced clinically acceptable images and accurate bi-ventricular and functional parameters compared with standard BH cine in patients with a CIED.

Impact: Our proposed pulse sequence will be useful for a shorter overall scan time while maintaining a diagnostically acceptable images in all CIED patients. 

Keywords: Arrhythmia, Arrhythmia

Motivation: This study aimed to explore the feasibility and accuracy of Sonic DL cardiac magnetic resonance cine technology.

Goal(s): We aimed to assess the performance of Sonic DL cine MRI at 3T for left ventricular (LV) volume and mass measurement, especially patients with arrhythmia and/or difficulty in breath-holding.

Approach: 48 patients were consecutively enrolled.  EDV, ESV, SV, EF, and LV mass were measured. The agreement and correlation of the parameters were assessed. Image quality was evaluated  and structure visibility rating.

Results: Good agreements and correlations were found between the techniques for measuring left ventricular function.

Impact: Sonic DL cardiac cine MRI allowed the assessment of LV volume with high accuracy and showed a significantly better image quality.