Cardiac Magnetic Resonance (CMR) protocols can be lengthy and complex, which has driven the research community to develop new technologies to make these protocols more efficient and patient-friendly. Two different approaches to improving CMR have been proposed, specifically "all-in-one" CMR, where several contrasts and/or motion states are acquired simultaneously, and "real-time" CMR, in which the examination is accelerated to avoid the need for breathholding and/or cardiac gating. The goal of this two-part manuscript is to describe these two different types of emerging rapid CMR protocols. To this end, the vision of all-in-one and real-time imaging are described, along with techniques which have been devised and tested along the pathway of clinical implementation. The pros and cons of the different methods are presented, and the remaining open needs of each are detailed. Part 1 tackles the "All-in-One" approaches, and Part 2 focuses on the "Real-Time" approaches along with an overall summary of these emerging methods. 

The Future of CMR: All-in-One vs. Real-Time CMR (Part 2).

Abstract Real-time MRI (rt-MRI) in children is a new imaging technique that combines the advantages of US — at frame rates of up to 50 images per second — with the quality and features of MRI. Although still subject of research, it has become a standard tool in the diagnostic portfolio of two pediatric radiology departments in Germany. Based on ultrashort acquisition times, any detrimental effects of macroscopic movements of the child and the physiological movements of the organs are negligible. Especially in pediatric brain imaging, rt-MRI has already proven its value. With suitable indications, rt-MRI can reduce anesthesia and sedation examinations in children below 6 years of age by 40% due to its very short examination time and its robustness to motion. There is a high level of acceptance among parents and referrers when diagnostic possibilities and limitations are communicated correctly. Conclusion : Completely new diagnostic possibilities arise in the imaging of the moving lung, the beating heart, joint movements, and speaking and swallowing, as demonstrated in this video-backed review. What is known: • MRI in moving children has been burdened with severe artifacts. • Gross motion usually has to be handled by sedation and periodic motion of the heart and lungs has to be compensated with time-consuming techniques until now. What is new: • Real-time MRI allows image acquisition with up to 50 frames per second similar to ultrasound frame rate. • Real-time MRI proofs to be very promising for imaging children, reducing examination time and sedation rate drastically. 

/pdf/real-time-mri-a-new-tool-of-radiologic-imaging-in-small-3h0mxa0x.pdf

Real-time MRI: a new tool of radiologic imaging in small children.

Abstract Background Congenital heart disease (CHD) is often associated with chronic right ventricular (RV) volume overload. Real-time magnetic resonance imaging (MRI) enables the analysis of cardiac function during free breathing. Objective To evaluate the influence of respiration in pediatric patients with CHD and chronic RV volume overload. Methods and materials RV volume overload patients ( n =6) and controls ( n =6) were recruited for cardiac real-time MRI at 1.5 tesla during free breathing. Breathing curves from regions of interest reflecting the position of the diaphragm served for binning images in four different tidal volume classes, each in inspiration and expiration. Tidal volumes were estimated from these curves by data previously obtained by magnetic resonance-compatible spirometry. Ventricular volumes indexed to body surface area and Frank-Starling relationships referenced to the typical tidal volume indexed to body height (TTVi) were compared. Results Indexed RV end-diastolic volume (RV-EDVi) and indexed RV stroke volume (RV-SVi) increased during inspiration (RV-EDVi/TTVi: RV load: + 16 ± 4%; controls: + 22 ± 13%; RV-SVi/TTVi: RV load: + 21 ± 6%; controls: + 35 ± 17%; non-significant for comparison). The increase in RV ejection fraction during inspiration was significantly lower in RV load patients (RV load: + 1.1 ± 2.2%; controls: + 6.1 ± 1.5%; P =0.01). The Frank-Starling relationship of the RV provided a significantly reduced slope estimate in RV load patients (inspiration: RV load: 0.75 ± 0.11; controls: 0.92 ± 0.02; P =0.02). Conclusion In pediatric patients with CHD and chronic RV volume overload, cardiac real-time MRI during free breathing in combination with respiratory-based binning indicates an impaired Frank-Starling relationship of the RV. Graphical Abstract 

First experience with real-time magnetic resonance imaging-based investigation of respiratory influence on cardiac function in pediatric congenital heart disease patients with chronic right ventricular volume overload.

BACKGROUND
The modified Look-Locker inversion recovery (MOLLI) sequence is commonly used for myocardial T1 mapping. However, it acquires images with different inversion times, which causes difficulty in motion correction for respiratory-induced misregistration to a given target image.


HYPOTHESIS
Using a generative adversarial network (GAN) to produce virtual MOLLI images with consistent heart positions can reduce respiratory-induced misregistration of MOLLI datasets.


STUDY TYPE
Retrospective.


POPULATION
1071 MOLLI datasets from 392 human participants.


FIELD STRENGTH/SEQUENCE
Modified Look-Locker inversion recovery sequence at 3 T.


ASSESSMENT
A GAN model with a single inversion time image as input was trained to generate virtual MOLLI target (VMT) images at different inversion times which were subsequently used in an image registration algorithm. Four VMT models were investigated and the best performing model compared with the standard vendor-provided motion correction (MOCO) technique.


STATISTICAL TESTS
The effectiveness of the motion correction technique was assessed using the fitting quality index (FQI), mutual information (MI), and Dice coefficients of motion-corrected images, plus subjective quality evaluation of T1 maps by three independent readers using Likert score. Wilcoxon signed-rank test with Bonferroni correction for multiple comparison. Significance levels were defined as P < 0.01 for highly significant differences and P < 0.05 for significant differences.


RESULTS
The best performing VMT model with iterative registration demonstrated significantly better performance (FQI 0.88 ± 0.03, MI 1.78 ± 0.20, Dice 0.84 ± 0.23, quality score 2.26 ± 0.95) compared to other approaches, including the vendor-provided MOCO method (FQI 0.86 ± 0.04, MI 1.69 ± 0.25, Dice 0.80 ± 0.27, quality score 2.16 ± 1.01).


DATA CONCLUSION
Our GAN model generating VMT images improved motion correction, which may assist reliable T1 mapping in the presence of respiratory motion. Its robust performance, even with considerable respiratory-induced heart displacements, may be beneficial for patients with difficulties in breath-holding.


LEVEL OF EVIDENCE
3 TECHNICAL EFFICACY: Stage 1.

Virtual MOLLI Target: Generative Adversarial Networks Toward Improved Motion Correction in MRI Myocardial T1 Mapping.

Introduction. A deep breath causes a whole range of physiological effects that are reflected in the electrocardiogram. The purpose of the study is to assess the position of the electrical axis of the heart during deep inspiration compared to quiet breathing in patients with precapillary pulmonary hypertension and compare these data with echocardiographic characteristics of the structural and functional state of the heart. Materials and methods. The study included 40 patients with idiopathic pulmonary hypertension and 40 patients with chronic thromboembolic pulmonary hypertension. Echocardiography assessed the size of the heart chambers, systolic and diastolic function of the right and left ventricles, pulmonary artery pressure, pulmonary vascular resistance and indicators of cardiovascular coupling. Results. The values of the electrical axis of the heart during free breathing were 106° [84°; 123°], on inspiration – 89° [87°; 120°] (p = 0.68). In 50 (62.5 %) patients, during a deep inspiration, the electrical axis of the heart shifted to the left from the original one, and in 30 (37.5 %) patients – to the right. In patients with a displacement of the electrical axis of the heart to the left from the original, compared with the others, the end-diastolic size of the left ventricle, end-diastolic and end-systolic volumes of the left ventricle, stroke volume, cardiac output were statistically significantly lower, and the eccentricity index, pulmonary vascular resistance and effective aortic stiffness – significantly larger. Conclusion. In patients with precapillary pulmonary hypertension, two variants of changes of the heart electrical axis during deep inspiration were identified: a shift to the right from the original and to the left from the original. Patients with a displacement of the electrical axis to the left from the original were characterized by a significantly greater increase in pulmonary vascular resistance, a decrease in left ventricular volumes, stroke volume and cardiac output. 

pdf/relationship-between-changes-in-the-electrical-axis-of-the-4npb4bbfp5.pdf

Relationship between changes in the electrical axis of the heart during inspiration and the structural and functional state of the heart according to echocardiography in patients with precapillary pulmonary hypertension

Cardiac real-time magnetic resonance imaging (RT-MRI) provides high-quality images even during free-breathing. Difficulties in post-processing impede its use in clinical routine.To demonstrate the feasibility of quantitative analysis of cardiac free-breathing RT-MRI and to compare image quality and volumetry during free-breathing RT-MRI in pediatric patients to standard breath-hold cine MRI.Pediatric patients (n = 22) received cardiac RT-MRI volumetry during free breathing (1.5 T; short axis; 30 frames per s) in addition to standard breath-hold cine imaging in end-expiration. Real-time images were binned retrospectively based on electrocardiography and respiratory bellows. Image quality and volumetry were compared using the European Cardiovascular Magnetic Resonance registry score, structure visibility rating, linear regression and Bland-Altman analyses.Additional time for binning of real-time images was 2 min. For both techniques, image quality was rated good to excellent. RT-MRI was significantly more robust against artifacts (P < 0.01). Linear regression revealed good correlations for the ventricular volumes. Bland-Altman plots showed a good limit of agreement (LoA) for end-diastolic volume (left ventricle [LV]: LoA -0.1 ± 2.7 ml/m2, right ventricle [RV]: LoA -1.9 ± 3.4 ml/m2), end-systolic volume (LV: LoA 0.4 ± 1.9 ml/m2, RV: LoA 0.6 ± 2.0 ml/m2), stroke volume (LV: LoA -0.5 ± 2.3 ml/m2, RV: LoA -2.6 ± 3.3 ml/m2) and ejection fraction (LV: LoA -0.5 ± 1.6%, RV: LoA -2.1 ± 2.8%).Compared to standard cine MRI with breath hold, RT-MRI during free breathing with retrospective respiratory binning offers good image quality, reduced image artifacts enabling fast quantitative evaluations of ventricular volumes in clinical practice under physiological conditions. 

/pdf/comparison-of-cardiac-volumetry-using-real-time-mri-during-3eogo267.pdf

Comparison of cardiac volumetry using real-time MRI during free-breathing with standard cine MRI during breath-hold in children

Case Report: Hemodynamic consequences of severe supraventricular arrhythmia assessed by real-time magnetic resonance imaging in combination with electrocardiography

In medicine, especially in radiology, artificial intelligence has sparked a growing interest in automated systems, image analysis, and acquisition standardization. In the wake of this standardization, the research field of ‘‘radiomics’’ has gained importance. Using computer-aided analysis, image data and contours can be evaluated to determine numerical values for shape, size, and gray-scale texture, which can then be examined in a clinical context. Especially in cardiovascular imaging, data acquisition and analysis in different cardiac and respiratory phases are of great interest. However, most research studies use parameters that have been laboriously calculated by hand. ‘‘ShortCardiac’’ is a Python-based framework with a user-friendly GUI for the quantitative determination of cardiac MR parameters. This allows researchers to utilize quantitative MR research for their studies without programming knowledge, with just a few clicks. All calculated parameters can be displayed graphically. ‘‘shortCardiac’’ allows the visualization of segmentation contours, the angle-dependent length measurement, the center of gravity and much more, in addition, the background can be hidden, and the images can be cropped automatically. In addition, ‘‘shortCardiac’’ can also be called via python and due to the object-oriented design, it is possible to integrate new segmentation frameworks with little effort in the future as well as to determine additional parameters. However, ‘‘ShortCardiac’’ comes with certain limitations. It only assesses cardiac short-axis data and functions merely as a postprocessing framework for determining surrogate parameters based on segmentation and image information. Manual segmentations or usage of fully automated segmentations, such as Circle cvi42, require additional software tools. Regardless of these restrictions, ‘‘ShortCardiac’’ provides an efficient, user-friendly tool, enabling researchers to capitalize on the expanding domain of radiomics. © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

'Shortcardiac'- An Open-Source Framework for Fast and Standardized Assessment of Cardiac Function

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Comparison of cardiac volumetry using real-time MRI during free-breathing with standard cine MRI during breath-hold in children

First experience with real-time magnetic resonance imaging-based investigation of respiratory influence on cardiac function in pediatric congenital heart disease patients with chronic right ventricular volume overload.

Case Report: Hemodynamic consequences of severe supraventricular arrhythmia assessed by real-time magnetic resonance imaging in combination with electrocardiography

'Shortcardiac'- An Open-Source Framework for Fast and Standardized Assessment of Cardiac Function