Gaining Additional Insights via MR Imaging of Further Nuclei besides Hydrogen
Besides conventional magnetic resonance imaging (MRI), where the magnetization of 1H nuclei is measured, other atomic nuclei with spin I > 0 can be used for signal detection. These nuclei are called X-nuclei. In our department we are developing hardware as well as acquisition, reconstruction and post-processing methods to acquire in-vivo MR signals of sodium (23Na), potassium (39K), chloride (35Cl), oxygen (17O), magnesium (25Mg), phosphorus (31P) and carbon (13C). Investigations of these nuclei are of special interest in clinical research because of their crucial role in many cellular processes. For instance, 23Na, 39K, and 35Cl concentrations strongly depend on the physiologic condition of a cell. And 17O MRI can be used to directly access the oxygen consumption non-invasively.
X-nuclei are physiologically relevant nuclei with a nuclear spin I > 0, which can thus be used for signal detection in addition to hydrogen. The requirements for X-nuclei imaging are strongly associated with their atomic properties. Due to the nucleus-specific gyromagnetic ratio the different nuclei have differing resonance frequencies at 7 Tesla (1H: ca. 297 MHz, 23Na: ca. 79 MHz, 35Cl: ca. 29 MHz, 39K: ca. 14 MHz). As a result, the MR scanner must support these frequencies in addition to the proton frequency and special coils are required for the respective nuclei (e.g. 23Na head coil, 23Na body coil). In collaboration with the research groups '7 Tesla MR: RF Systems and Concepts' and 'Electromagnetic Simulations and RF Safety' we are developing and building MR coils for X-nuclei imaging in-house such as a sodium body coil (Platt et al., Magn Reson Med, 2018).
Furthermore, 17O, 23Na, 39K, and 35Cl have a nuclear spin greater than 1/2 and thus exhibit very short relaxation times. This necessitates the use of dedicated pulse sequences such as a density-adapted radial sequence (Nagel et al., Magn Reson Med, 2009). Furthermore, the in vivo concentration of X-nuclei is orders of magnitude lower compared to the concentration of 1H. X-nuclei imaging therefore greatly benefits from ultrahigh static magnetic fields such as 7 Tesla and X-nuclei MR investigations can be further improved via advanced image reconstruction and post-processing techniques.
References:
- Gast LV, Platt T, Nagel AM, Gerhalter T: Recent technical developments and clinical research applications of sodium (23Na) MRI. Progress in Nuclear Magnetic Resonance Spectroscopy. 2023.
- Platt T, Ladd ME, Paech D: 7 Tesla and beyond: advanced methods and clinical applications in magnetic resonance imaging. Investigative radiology. 2021; 56:705-725.
- Kratzer FJ, Flassbeck S, Schmitter S, Wilferth T, Magill AW, Knowles BR, ... & Nagel AM. 3D sodium (23Na) magnetic resonance fingerprinting for time‐efficient relaxometric mapping. Magnetic Resonance in Medicine. 2021; 86(5):2412-2425.
- Kratzer FJ, Flassbeck S, Nagel AM, Behl NGR, Knowles BR, Bachert P, ... & Schmitter S. Sodium relaxometry using 23Na MR fingerprinting: A proof of concept. Magnetic Resonance in Medicine. 2020; 84(5):2577-2591.
- Lott J, Platt T, Niesporek SC, Paech D, Behl NGR, Niendorf T, ... & Nagel AM. Corrections of myocardial tissue sodium concentration measurements in human cardiac 23Na MRI at 7 Tesla. Magnetic resonance in medicine. 2019; 82(1): 159-173.
- Niesporek SC, Nagel AM, & Platt T. Multinuclear MRI at ultrahigh fields. Topics in Magnetic Resonance Imaging. 2019; 28(3):173-188.
- Platt T, Umathum R, Fiedler TM, Nagel AM, Bitz AK, Maier F, Bachert P, Ladd ME, Wielpütz MO, Kauczor HU, Behl NGR: In vivo self-gated 23Na MRI at 7 T using an oval-shaped body resonator. Magnetic Resonance in Medicine. 2018; 80:1005-1019.
- Nagel AM, Laun FB, Weber MA, Matthies C, Semmler W, Schad LR. Sodium MRI using a density-adapted 3D radial acquisition technique. Magn Reson Med 2009; 62(6):1565-1573.
Contact
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Dr. Tanja Platt
Project group leader
