Emerging Techniques in Cardiac Magnetic Resonance Imaging

Abstract

Cardiovascular disease is the leading cause of death and a significant contributor of health care costs. Noninvasive imaging plays an essential role in the management of patients with cardiovascular disease. Cardiac magnetic resonance (MR) can noninvasively assess heart and vascular abnormalities, including biventricular structure/function, blood hemodynamics, myocardial tissue composition, microstructure, perfusion, metabolism, coronary microvascular function, and aortic distensibility/stiffness. Its ability to characterize myocardial tissue composition is unique among alternative imaging modalities in cardiovascular disease. Significant growth in cardiac MR utilization, particularly in Europe in the last decade, has laid the necessary clinical groundwork to position cardiac MR as an important imaging modality in the workup of patients with cardiovascular disease. Although lack of availability, limited training, physician hesitation, and reimbursement issues have hampered widespread clinical adoption of cardiac MR in the United States, growing clinical evidence will ultimately overcome these challenges. Advances in cardiac MR techniques, particularly faster image acquisition, quantitative myocardial tissue characterization, and image analysis have been critical to its growth. In this review article, we discuss recent advances in established and emerging cardiac MR techniques that are expected to strengthen its capability in managing patients with cardiovascular disease. Level of Evidence: 5 Technical Efficacy: Stage 1

Coronary functional assessment in non-obstructive coronary artery disease: Present situation and future direction

“…CMR is one of the widely used technique to assess myocardial perfusion ( 103 ). It allows visualization of transmural myocardial flow and assessment of microvascular function in patients suspected with microvascular angina ( 104 ).…”

Introduction of a cascaded segmentation pipeline for parametric T1 mapping in cardiovascular magnetic resonance to improve segmentation performance

“…Cardiovascular magnetic resonance (CMR) is one of the most important non-invasive imaging modalities for risk stratification in cardiovascular diseases 1 , 2 . It enables the characterization of focal and diffuse changes in the myocardial tissue by quantitative techniques such as parametric mapping 3 , which is considered as one of the most meaningful innovations in recent CMR developments 4 , 5 .…”

“…For diagnostics, the post-processing involves the segmentation of the myocardium as tissue of interest in order to obtain quantitative values 7 . This is usually performed in a manual and often time consuming manner 1 , 7 – 10 . Furthermore, even experienced readers show intra-observer variability that results in considerable quantification uncertainty 11 .…”

“…Current developments attempt to overcome both, the time consumption and the reproducibility uncertainty by using convolutional neural networks (CNNs) to automatically segment the tissue of interest. One of the most prominent CNN models in medical segmentation tasks is the U-Net 1 introduced by Ronneberger et al 12 . While a standard U-Net already shows an average geometrical overlap above 70% with an expert segmentation 8 – 10 , 13 , which is conventionally assumed as a good result 8 , current development focuses on technical improvements for even better segmentation quality.…”

On Myocarditis and a New Era for Cardiac Magnetic Resonance Imaging

“…Progressively accelerated sequences can significantly reduce overall scan time, and tissue characterization has been improved with the advent of myocardial T1 and T2 mapping techniques as well as high-quality cardiac diffusion-weighted imaging. 2 Second, radiologists have utilized these new techniques to provide value to clinicians and patients in ways that they could not before. Cardiac MR exams initially were heavily focussed on cardiac masses, congenital heart disease and viability imaging, but in the last decade, MR has become an essential modality for evaluating the patient with a nonischemic cardiomyopathy or with suspected cardiac chest pain without evidence of coronary artery disease to explain it.…”