Self-supervised learning for improved calibrationless radial MRI with NLINV-Net.

Purpose: To develop a neural network architecture for improved calibrationless reconstruction of radial data when no ground truth is available for training.

Methods: NLINV-Net is a model-based neural network architecture that directly estimates images and coil sensitivities from (radial) k-space data via nonlinear inversion (NLINV). Combined with a training strategy using self-supervision via data undersampling (SSDU), it can be used for imaging problems where no ground truth reconstructions are available.

Self-Supervised Learning for Improved Calibrationless Radial MRI with NLINV-Net.

Purpose: To develop a neural network architecture for improved calibrationless reconstruction of radial data when no ground truth is available for training.

Methods: NLINV-Net is a model-based neural network architecture that directly estimates images and coil sensitivities from (radial) k-space data via non-linear inversion (NLINV). Combined with a training strategy using self-supervision via data undersampling (SSDU), it can be used for imaging problems where no ground truth reconstructions are available.

Assessment of deep learning segmentation for real-time free-breathing cardiac magnetic resonance imaging at rest and under exercise stress.

In recent years, a variety of deep learning networks for cardiac MRI (CMR) segmentation have been developed and analyzed. However, nearly all of them are focused on cine CMR under breathold. In this work, accuracy of deep learning methods is assessed for volumetric analysis (via segmentation) of the left ventricle in real-time free-breathing CMR at rest and under exercise stress.

Evaluation of MR-safe bioptomes for MR-guided endomyocardial biopsy in minipigs: a potential radiation-free clinical approach.

Background: Diagnostic accuracy of endomyocardial biopsy could improve if clinically safe magnetic resonance (MR)-compatible bioptomes were available. We explored two novel MR-compatible cardiac bioptomes for performance, safety, and clinical viability, employing in vivo minipig trials and phase-contrast synchrotron radiation computed microtomography (SRµCT).

Methods: Analysis of ex vivo obtained pig endomyocardial biopsies was performed using phase-contrast SRµCT and conventional two-dimensional histology.

Comparison between cone-beam breast-CT and full-field digital mammography for microcalcification detection depending on breast density.

The purpose of this study was to evaluate the impact of breast density on the diagnostic performance of cone-beam breast-CT (CBBCT) in comparison to full-field digital mammography (FFDM) for the detection of microcalcifications. This retrospective IRB-approved study was conducted between December 2015 and March 2017 and enrolled 171 women with Breast Imaging Reporting and Data System category 4 or 5 lesions on FFDM and additional CBBCT; 56 of which were ineligible. The inclusion was restricted to 83 women (90 breasts, 90 lesions) with microcalcifications.

Free-Breathing Liver Fat, R₂* and B₀ Field Mapping Using Multi-Echo Radial FLASH and Regularized Model-Based Reconstruction.

This work introduced a stack-of-radial multi-echo asymmetric-echo MRI sequence for free-breathing liver volumetric acquisition. Regularized model-based reconstruction was implemented in Berkeley Advanced Reconstruction Toolbox (BART) to jointly estimate all physical parameter maps (water, fat, R , and B field inhomogeneity maps) and coil sensitivity maps from self-gated k -space data. Specifically, locally low rank and temporal total variation regularization were employed directly on physical parameter maps.

Magnetic resonance imaging of organ iron before and after correction of iron deficiency in patients with heart failure.

Aims: Intravenous iron therapy (IVIT) is known to improve functional status in chronic heart failure (CHF) patients. The exact mechanism is not completely understood. We correlated magnetic resonance imaging (MRI) patterns of T2* iron signal in various organs to systemic iron and exercise capacity (EC) in CHF before and after IVIT.

Free-breathing myocardial T mapping using inversion-recovery radial FLASH and motion-resolved model-based reconstruction.

Purpose: To develop a free-breathing myocardial mapping technique using inversion-recovery (IR) radial fast low-angle shot (FLASH) and calibrationless motion-resolved model-based reconstruction.

Methods: Free-running (free-breathing, retrospective cardiac gating) IR radial FLASH is used for data acquisition at 3T. First, to reduce the waiting time between inversions, an analytical formula is derived that takes the incomplete recovery into account for an accurate calculation.

Imaging of arrhythmia: Real-time cardiac magnetic resonance imaging in atrial fibrillation.

Objectives: Quantitative evaluations of function, volume and mass are fundamental in the diagnostic workup of different cardiovascular diseases and can be exactly determined by CMRI in sinus rhythm. This does not hold true in arrhythmia as CMR is hampered by reconstruction artifacts caused by inconsistent data from multiple heartbeats. Real-time (RT) MRI at high temporal resolution might reduce these problems.

Impaired Exercise Tolerance in Repaired Tetralogy of Fallot Is Associated With Impaired Biventricular Contractile Reserve: An Exercise-Stress Real-Time Cardiovascular Magnetic Resonance Study.

Background: Correction of tetralogy of Fallot (cTOF) often results in pulmonary valve pathology and right ventricular (RV) dysfunction. Reduced exercise capacity in cTOF patients cannot be explained by these findings alone. We aimed to explore why cTOF patients exhibit impaired exercise capacity with the aid of a comprehensive cardiopulmonary exercise testing (CPET) and real-time cardiovascular magnetic resonance exercise testing (CMR-ET) protocol.

Ex Vivo Study of Artifacts Caused by Breast Tissue Markers with Different 1.5 Tesla and 3 Tesla MRI Scanners - A Bicentric Study.

Rationale And Objectives: The purpose of our study was to evaluate magnetic resonance (MR) artifacts related to breast tissue markers in breast imaging procedures.

Materials And Methods: In this bicentric prospective ex vivo study 10 different commercially available markers were measured in self-made breast phantoms. Breast tissue markers varying in marker size, composition, and shape were evaluated.

Model-based myocardial T1 mapping with sparsity constraints using single-shot inversion-recovery radial FLASH cardiovascular magnetic resonance.

Background: This study develops a model-based myocardial T1 mapping technique with sparsity constraints which employs a single-shot inversion-recovery (IR) radial fast low angle shot (FLASH) cardiovascular magnetic resonance (CMR) acquisition. The method should offer high resolution, accuracy, precision and reproducibility.

Methods: The proposed reconstruction estimates myocardial parameter maps directly from undersampled k-space which is continuously measured by IR radial FLASH with a 4 s breathhold and retrospectively sorted based on a cardiac trigger signal.

Absence of DNA double-strand breaks in human peripheral blood mononuclear cells after 3 Tesla magnetic resonance imaging assessed by γH2AX flow cytometry.

Objectives: Magnetic resonance imaging (MRI) is regarded as a non-harming and non-invasive imaging modality with high tissue contrast and almost no side effects. Compared to other cross-sectional imaging modalities, MRI does not use ionising radiation. Recently, however, strong magnetic fields as applied in clinical MRI scanners have been suspected to induce DNA double-strand breaks in human lymphocytes.

Quantification of left atrial volume and phasic function using cardiovascular magnetic resonance imaging-comparison of biplane area-length method and Simpson's method.

Left atrial (LA) enlargement and dysfunction are markers of chronic diastolic dysfunction and an important predictor of adverse cardiovascular and cerebrovascular outcomes. Accordingly, accurate quantification of left atrial volume (LAV) and function is needed. In routine clinical cardiovascular magnetic resonance (CMR) imaging the biplane area-length method (Bi-ALM) is frequently applied due to time-saving image acquisition and analysis.

Targeted endomyocardial biopsy guided by real-time cardiovascular magnetic resonance.

Background: Endomyocardial biopsies (EMB) are an important diagnostic tool for myocarditis and other infiltrative cardiac diseases. Routinely, biopsies are obtained under fluoroscopic guidance with a substantial radiation burden. Despite procedural success, there is a large sampling error caused by missing the affected myocardium.

Artifacts Caused by Breast Tissue Markers in a Dedicated Cone-beam Breast CT in Comparison to Full-field Digital Mammography.

Rationale And Objectives: The purpose of this ex vivo study was to investigate artifacts in a cone-beam breast computed tomography (CBBCT) caused by breast tissue markers.

Materials And Methods: Breast phantoms with self-made tissue pork mincemeat were created. Twenty-nine different, commercially available markers with varying marker size, composition, and shape were evaluated.

Peak flow velocities in the ascending aorta-real-time phase-contrast magnetic resonance imaging vs. cine magnetic resonance imaging and echocardiography.

This prospective study of eight healthy volunteers evaluates peak flow velocities (PFV) in the ascending aorta using real-time phase-contrast magnetic resonance imaging (MRI) in comparison to cine phase-contrast MRI and echocardiography. Flow measurements by echocardiography and cine phase-contrast MRI with breath-holding were performed according to clinical standards. Real-time phase-contrast MRI at 40 ms temporal resolution and 1.

Non-invasive estimation of pulmonary outflow tract obstruction: A comparative study of cardiovascular phase contrast magnetic resonance and Doppler echocardiography versus cardiac catheterization.

Aim: To compare estimated pressure gradients from routine follow-up cardiovascular phase-contrast magnetic resonance (PC-MR) with those from Doppler echocardiography and invasive catheterization in patients with congenital heart disease (CHD) and pulmonary outflow tract obstruction.

Methods: In 75 patients with pulmonary outflow tract obstruction maximal and mean PC-MR gradients were compared to maximal and mean Doppler gradients. Additionally, in a subgroup of 31 patients maximal and mean PC-MR and Doppler pressure gradients were compared to catheter peak-to-peak pressure gradients (PPG).

Right Atrial Volume is Increased in Corrected Tetralogy of Fallot and Correlates with the Incidence of Supraventricular Arrhythmia: A CMR Study.

The aim of this study was to evaluate right atrial (RA) volume in corrected Tetralogy of Fallot (cTOF) and assess its correlation with the occurrence of supraventricular (SV) arrhythmia. Cardiac magnetic resonance imaging (CMR) and 24-h Holter were performed in n = 67 consecutive cTOF patients (age 30 ± 11.3 years).

BNP and haematological parameters are markers of severity of Ebstein's anomaly: correlation with CMR and cardiopulmonary exercise testing.

Aims: Ebstein's anomaly (EA) involves a displaced and dysplastic tricuspid valve resulting in an atrialized portion of the right ventricle and an enlargement of the functional right ventricle and right atrium. Biomarkers targeting heart failure such as brain natriuretic peptide (BNP) or haematological parameters [haemoglobin (Hb) and haematocrit (Hct)] are upregulated in states of pulmonary hypoperfusion. We hypothesized that decreased pulmonary perfusion dependent on the stage of right heart failure is a possible mechanism in EA, and that it can be correlated with cardiac magnetic resonance (CMR) parameters.

Real-time magnetic resonance imaging of cardiac function and flow-recent progress.

Cardiac structure, function and flow are most commonly studied by ultrasound, X-ray and magnetic resonance imaging (MRI) techniques. However, cardiovascular MRI is hitherto limited to electrocardiogram (ECG)-synchronized acquisitions and therefore often results in compromised quality for patients with arrhythmias or inabilities to comply with requested protocols-especially with breath-holding. Recent advances in the development of novel real-time MRI techniques now offer dynamic imaging of the heart and major vessels with high spatial and temporal resolution, so that examinations may be performed without the need for ECG synchronization and during free breathing.

Situs inversus totalis with congenitally corrected transposition of the great arteries: insights from cardiac MRI.

Introduction: Situs inversus totalis with congenitally corrected transposition of the great arteries represents a relatively rare congenital condition.

Case Description: The current report describes the case of a 56 year old patient with an atrio-ventricular and ventricular-arterial discordance of the heart chambers without surgical correction, incidentally detected during hepatocellular carcinoma evaluation. The systemic venous blood arrived via the right atrium and a mitral valve in the morphologically left but pulmonary arterial ventricle that gave rise to a pulmonary trunk.

Quantification of left ventricular torsion and diastolic recoil using cardiovascular magnetic resonance myocardial feature tracking.

Objectives: Cardiovascular magnetic resonance feature tracking (CMR-FT) offers quantification of myocardial deformation from routine cine images. However, data using CMR-FT to quantify left ventricular (LV) torsion and diastolic recoil are not yet available. We therefore sought to evaluate the feasibility and reproducibility of CMR-FT to quantify LV torsion and peak recoil rate using an optimal anatomical approach.

Comparison of end-diastolic versus end-systolic cardiac-computed tomography reconstruction interval in patient's prior to pulmonary vein isolation.

Purpose: Aim of the study was to investigate diagnostic accuracy of cardiac computed tomography angiography (CCTA) between left ventricular end-systolic (LVES) and left ventricular end-diastolic (LVED) cardiac phase for thrombus detection in patient's prior to pulmonary vein isolation (PVI).

Materials And Methods: 182 consecutive Patients with drug refractory AF scheduled for PVI (62.6% male, mean age 64.

Quantification of left atrial strain and strain rate using Cardiovascular Magnetic Resonance myocardial feature tracking: a feasibility study.

Background: Cardiovascular Magnetic Resonance myocardial feature tracking (CMR-FT) is a quantitative technique tracking tissue voxel motion on standard steady-state free precession (SSFP) cine images to assess ventricular myocardial deformation. The importance of left atrial (LA) deformation assessment is increasingly recognized and can be assessed with echocardiographic speckle tracking. However atrial deformation quantification has never previously been demonstrated with CMR.