Clinical MR Biomarkers

7 Tesla and Beyond: Advanced Methods and Clinical Applications in Magnetic Resonance Imaging

ABSTRACT

Ultrahigh magnetic fields offer significantly higher signal-to-noise ratio, and several magnetic resonance applications additionally benefit from a higher contrast-to-noise ratio, with static magnetic field strengths of B0 ≥ 7 T currently being referred to as ultrahigh fields (UHFs). The advantages of UHF can be used to resolve structures more precisely or to visualize physiological/pathophysiological effects that would be difficult or even impossible to detect at lower field strengths. However, with these advantages also come challenges, such as inhomogeneities applying standard radiofrequency excitation techniques, higher energy deposition in the human body, and enhanced B0 field inhomogeneities. The advantages but also the challenges of UHF as well as promising advanced methodological developments and clinical applications that particularly benefit from UHF are discussed in this review article.

[Chemical exchange saturation transfer (CEST) : Magnetic resonance imaging in diagnostic oncology]

BACKGROUND

Contrast generation by chemical exchange saturation transfer (CEST) is a recently emerging magnetic resonance imaging (MRI) research field with high clinical potential.

METHODS

This review covers the methodological principles and summarizes the clinical experience of CEST imaging studies in diagnostic oncology performed to date.

RESULTS AND CONCLUSION

CEST enables the detection of lowly concentrated metabolites, such as peptides and glucose, through selective saturation of metabolite-bound protons and subsequent magnetization transfer to free water. This technology yields additional information about metabolic activity and the tissue microenvironment without the need for conventional contrast agents or radioactive tracers. Various studies, mainly conducted in patients with neuro-oncolgic diseases, suggest that this technology may aid to assess tumor malignancy as well as therapeutic response prior to and in the first follow-up after intervention.

KEY POINTS

CEST-MRI enables the indirect detection of metabolites without radioactive tracers or contrast agents. Clinical experience exists especially in the setting of neuro-oncologic imaging. In oncologic imaging, CEST-MRI may improve assessment of prognosis and therapy response.