## 6 General Recommendations
### Field Strength Dependency  
Higher field strengths in MRI can offer improved signal-to-noise ratios and spatial resolution, albeit at the cost of increased susceptibility to artefacts. The FRF has been extensively evaluated at both 1.5 T and 3 T, demonstrating its flexibility at both clinically established field strengths. Although 3 T indeed brings additional signal-to-noise that can be exchanged for improved spatial or temporal resolution, imaging is more prone to artefacts. Most notable is the potential occurrence of banding artefacts when increased repetition times are used for bSSFP to incorporate, for example, bipolar gradients to enable flow imaging. Although GRE instead of bSSFP has been used to overcome these artefacts, GRE has reduced signal and blood-myocardium contrast compared to bSSFP and may partly diminish the obtained increase in SNR from moving to a higher field strength. Apart from the clinically established field strengths of 1.5 T and 3 T, field strengths <1 T have recently gained considerable attention and are intensively being explored for cardiac imaging [70]. Staggering progress in hardware, software, and methodology has helped advance the hypothesis that this progress may revert the trend for ever-increasing field strength and be directed instead to making low-field systems more powerful, more cost-effective, and more widely accessible. Their reduced costs of purchase, installation, and maintenance, and advantages in system sitting will facilitate the more global dissemination of MRI to the benefit of a larger patient pool and reach geographical regions that have not traditionally had easy access to MRI. This dissemination is further strengthened by the FRF as discussed in this review, which no longer requires highly trained MR operators and a relatively complex patient setup. The combination of low-field MRI and FRF technology therefore has an unprecedented potential. Although unpublished yet, several preliminary studies have already demonstrated the feasibility of the FRF for anatomical, cine, and flow imaging at 0.55 T (Figure 11). The altered physics of low-field MRI are favourable for bSSFP imaging and are therefore  
Figure 10: Panel (**A**) Comparison of anatomical images acquired by the 5D free-running framework using a standard balanced steady-state free-precession (bSSFP) and fast-interrupted steady-state (FISS) acquisition at 3 T. The 5D datasets were multiplanar reformatted to a sagittal view, and images are shown in systole and diastole at both end-expiration and end-inspiration. The yellow lines help to indicate respiratory motion. The red arrows indicate the decrease in streaking artefacts in FISS compared to bSSFP. Panel (**B**) Comparison of coronary reformats obtained using both bSSFP and FISS, at both 1.5 T and 3 T. The water–fat cancellation artefacts at the coronary vessel borders can be observed in the bSSFP images, while these are absent in the FISS images. Panel (**C**) Comparison of anatomical images using a bSSFP and FISS acquisition at 1.5 T. Both 5D image data were binned into 16 cardiac phases and four respiratory motion states, of which eight cardiac phases in the end-expiratory motion state are shown in coronal view for each method. The red arrows indicate cardiac regions containing fat that is suppressed using FISS but not using bSSFP. Panel (**D**) Comparison of anatomical images using a bSSFP and FISS acquisition at 3 T. Both 5D image data were binned into 26 cardiac phases and four respiratory motion states, of which eight cardiac phases in the end-expiratory motion state are shown in coronal view for each method. The red arrows indicate cardiac regions containing fat that is suppressed using FISS but not using bSSFP. Figure created using the original source images by [PERSON] et al. (2019) with author permission. directly advantageous for the FRF.