Cardiac functional magnetic resonance imaging at 7T: Image quality optimization and ultra-high field capabilities

Abstract

BACKGROUND 7T cardiac magnetic resonance imaging (MRI) introduces several advantages, as well as some limitations, compared to lower-field imaging. The capabilities of ultra-high field (UHF) MRI have not been fully exploited in cardiac functional imaging. AIM To optimize 7T cardiac MRI functional imaging without the need for conducting B1 shimming or subject-specific tuning, which improves scan efficiency. In this study, we provide results from phantom and in vivo scans using a multi-channel transceiver modular coil. METHODS We investigated the effects of adding a dielectric pad at different locations next to the imaged region of interest on improving image quality in subjects with different body habitus. We also investigated the effects of adjusting the imaging flip angle in cine and tagging sequences on improving image quality, B1 field homogeneity, signal-to-noise ratio (SNR), blood-myocardium contrast-to-noise ratio (CNR), and tagging persistence throughout the cardiac cycle. RESULTS The results showed the capability of achieving improved image quality with high spatial resolution (0.75 mm × 0.75 mm × 2 mm), high temporal resolution (20 ms), and increased tagging persistence (for up to 1200 ms cardiac cycle duration) at 7T cardiac MRI after adjusting scan set-up and imaging parameters. Adjusting the imaging flip angle was essential for achieving optimal SNR and myocardium-to-blood CNR. Placing a dielectric pad at the anterior left position of the chest resulted in improved B1 homogeneity compared to other positions, especially in subjects with small chest size. CONCLUSION Improved regional and global cardiac functional imaging can be achieved at 7T MRI through simple scan set-up adjustment and imaging parameter optimization, which would allow for more streamlined and efficient UHF cardiac MRI.

Ultra-high field cardiac MRI in large animals and humans for translational cardiovascular research

“…Moreover, safety procedures are not widely established, and no globally applicable guidelines exist. Alternatively, such as the MRI system used here a new generation of UHF-MRI systems has become available which are more suited to the high demands of a cardiovascular examination, and which also provide better image quality ( 23 , 49 , 119 ) although both vendors currently do not provide FDA or CE clearance for routine cardiac patient use. For human use, only MRI systems with a field strength of 3 T and less have been approved for cardiac applications by the FDA or the European Commission (CE).…”

Feasibility of cardiovascular magnetic resonance imaging at 5T in comparison to 3T

“…It was attributable to the ndings that prolonged T1 relaxation of blood and myocardium at UHF may minimize the effects of in ow-dependent blood pool signal intensity and preserve a good blood-myocardial contrast in FGRE sequences, which was observed in studies at 7T as well 4 . Nevertheless, further improvements including B1 shimming optimization and dielectric pads application 24 are still in need, as mild degraded signal in posterior wall of RV could be occasionally detected and might affect the assessment of cardiomyopathies involving RV.…”

Ressonância Magnética Cardíaca em Campo Magnético de 7 Tesla: Experiência Inicial com os Núcleos de Hidrogênio e do Sódio

“… 1 A ressonância magnética cardíaca (RMC) é considerada o método padrão-ouro na análise funcional do coração e desempenha um papel essencial no diagnóstico de várias cardiomiopatias, incluindo infarto do miocárdio. 2 Quando há uma falha no suprimento energético das células cardíacas, ocorre uma diminuição do fluxo sanguíneo em determinadas regiões, o que pode levar à morte celular. A ressonância magnética é capaz de avaliar a viabilidade do tecido cardíaco por meio da interação com os prótons presentes nesse tecido, sendo o núcleo de hidrogênio o mais comum para esse propósito.…”