Conventional high-field MRI scanners make it challenging to examine body regions containing metallic implants. The large difference in magnetic susceptibility between metal and the surrounding tissue causes significant local magnetic field distortion, leading to the familiar image artifacts around implants. Even with advanced techniques such as WARP and SEMAC, image quality on conventional 1.5T and 3T MRI systems remains limited, making accurate diagnosis difficult. At a lower field strength of 0.55T, the systems of the MAGNETOM Free. Platform have the advantage of producing significantly fewer susceptibility artifacts than high-field systems. With far fewer distortions and artifacts near implants, these lower-field scanners enable better visualization of pathologies, despite the lower resolution and signal-to-noise ratio. As in high-field imaging, these examinations use turbo spin echo (TSE) sequences with optimized acquisition parameters that are activated via the WARP option. Increased excitation and readout bandwidths are crucial here, especially in combination with STIR technology as a robust alternative to conventional spectral fat saturation for fat suppression. In addition to established advanced acceleration techniques (parallel imaging and Simultaneous Multi-Slice acquisition), deep-learning-based image reconstruction methods offer enormous potential also at lower field strengths. Enabling high-quality diagnostic MR images in very acceptable acquisition times on 0.55T systems.

Examining Musculoskeletal #Implants with Lower-Field #MRI by Markus Lentschig, MD; et al. (ZEMODI, Bremen Germany).

Learn more and download the protocols (.exar1 & PDF) for knee and hip imaging on MAGNETOM Free.Max:
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#RadSky #MSK #Below1T

Advanced imaging techniques may be hampered by geometric distortion artifacts arising at air–tissue interfaces. This is made worse by the need to run highly efficient EPI-based read-outs for diffusion MRI, functional MRI, and multi-echo gradient echo sequences for T2* relaxometry, which leads to an increasing need for specialist image-based shimming techniques. Further challenges include B1 inhomogeneity-related artifacts enhanced by the presence of amniotic fluid, and SAR limitations resulting in inefficiencies in the sequences. Both B0 and B1 inhomogeneities increase with higher field strengths. Therefore, lower field strengths reduce both the impact of the aforementioned artifacts and the need for specialist correction tools. While comfort and space are paramount for any patient undergoing an MRI scan, pregnant women in the later weeks of pregnancy present a population where space and comfort is both particularly important and challenging to achieve in a standard-sized MRI bore. In addition, the number of obese pregnant women is rising – with 24% of all pregnant women in the UK and U.S. considered obese as of 2020. This presents a currently underserved population that could benefit from fetal MRI, as these women often do not receive adequate prenatal imaging due in part to the detrimental effect of increased abdominal fat on ultrasound imaging. Finally, a field strength-independent challenge concerns unpredictable and uncontrollable fetal motion, especially in early-to-mid gestation when fetuses have enough space for large displacements. This can be particularly problematic for fetal functional MRI modalities, which rely on the acquisition of the same slice location multiple times in a time-series format, to then be combined for spatiotemporal analysis. Both post-processing base techniques such as slice-to-volume registration (SVR) and prospective motion-correction techniques based on localization and tracking may be employed at low field strengths.

On today’s #WorldBirthDefectsDay, I'd like to highlight Fetal Low Field #MRI by Jana Hutter, PhD; @shaihanmalik.bsky.social; et al. (@kingscollegelondon.bsky.social)
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#MagnetomWorld #FetalMRI #AccessToCare #Below1T @banksgaia.bsky.social

SWI is a useful MRI technique for the detection and characterization of microhemorrhages and small venous structures. In general, SWI profits from high magnetic field strength with respect to susceptibility contrast and spatial resolution. However, methods based on 3D EPI have been implemented at 0.55T and result in similar detection rates of microbleeds compared to 1.5T. Recently, a deep learning (DL)-based reconstruction has been added to this 3D-segmented EPI sequence, enabling susceptibility-weighted images with higher spatial resolution and increased sharpness. Learn more about this research sequence that offers great advantages for diagnostic neuroimaging at lower field strengths, and enabled the authors to visualize a larger volume of the brain parenchyma more accurately, and to avoid common pitfalls and mimics.

Susceptibility-Weighted Imaging at Lower Field Strength with Deep Learning Image Reconstruction by Johanna M Lieb, M.D.; et al. (University Hospital Basel, Switzerland).
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#MagnetomWorld #MRI #Below1T #DeepResolve