Limited available time of the MRI system, large numbers of needed animals, or instable models, often make shorter measurement times necessary.
Longer measurements times are often needed to achieve sufficient SNR when using lower field strengths. Using UHF, measurement times can be significantly shortened, since, for example, an increase in sensitivity by a factor of two allows to acquire images with the same resolution and similar quality in a quarter of the time [5]. Therefore, the number of data averages can be reduced, and the time saved can be invested into additional subjects or further studies.
An additional benefit of the SNR gain at UHF is that imaging of X-nuclei with low gyromagnetic ratios, quadruple moments, and low abundances can be significantly improved or even made feasible for the first time [5,6,7,8].
This opens up a multitude of different research applications, such as sodium (²³Na) imaging. Sodium MRI is currently used for a wide range of applications. On clinical systems, for example, sodium concentration measurements are used to study tissue viability [9]. Due to the high sensitivity, the use of UHF greatly facilitates sodium imaging [7]. Preclinical UHF focuses, among others, on using sodium concentrations and distributions as metrics to help cellular engineers improve human mesenchymal stem cell (hMSC) conditioning for treatment of ischemic stroke [10]. Furthermore, UHF MRI can potentially lead to a breakthrough for oxygen (17O) imaging which allows direct access to the cellular oxygen metabolism. Cellular oxygen metabolism is altered in several diseases such as Alzheimer’s and Parkinson’s as well as in cancer. Thus, 17O MRI has the potential to visualize local pathology changes in the brain, underling the importance of this imaging approach [8].
Another application of X-nuclei imaging of metabolism is found with deuterium imaging, which can be used to map glucose metabolism. In addition to the ability to map glucose metabolism as opposed to glucose uptake, deuterium metabolic imaging (DMI), has the additional advantage over positron emission tomography (PET), of using non-radioactive substrates [11]. The increased sensitivity of deuterium at UHF, makes DMI a viable alternative to PET.
[5] Nowogrodzki A. The world’s strongest MRI machines are pushing human imaging to new limits. Nature 563, 24-26 (2018), doi: 10.1038/d41586-018-07182-7
www.ncbi.nlm.nih.gov/pubmed/30382222
[6] Öz G, Tkáč I, Uğurbil K. Animal models and high field imaging and spectroscopy. Dialogues in Clinical Neuroscience. 2013;15(3):263-278.
www.ncbi.nlm.nih.gov/pmc/articles/PMC3811099/
[7] Deutsches Krebsforschungszentrum: www.dkfz.de/en/medphysrad/projectgroups/t7_x-nuclei/t7_x-nuclei_Na_MRI
[8] Deutsches Krebsforschungszentrum:
www.dkfz.de/en/medphysrad/projectgroups/t7_x-nuclei/t7_x-nuclei_O_MRK
[9] Thulborn KR, Lu A, Atkinson IC, Damen F, Villano J. Quantitative Sodium MR Imaging and Sodium Bioscales for the Management of Brain Tumors. Neuroimaging clinics of North America. 2009;19(4):615-624. doi:10.1016/j.nic.2009.09.001.
www.ncbi.nlm.nih.gov/pmc/articles/PMC3718497/
[10] Using High Fields to Combat Ischemic Stroke with Cell Therapy
Bruker: www.bruker.com/events/webinars/using-high-fields-to-combat-ischemic-stroke-with-cell-therapy.html
[11] De Feyter H, Behar K, Corbin Z, Fulbright R, Brown P, McIntyre S, Nixon T, Rothman D, de Graaf R. Deuterium metabolic imaging (DMI) for MRI-based 3D mapping of metabolism in vivo. Sci. Adv. 2018; 4. doi: 10.1126/sciadv.aat7314
https://advances.sciencemag.org/content/4/8/eaat7314