Purpose To develop a framework for 3D sodium (23Na) MR fingerprinting (MRF), based on irreducible spherical tensor operators with tailored flip angle (FA) pattern and time‐efficient data acquisition for simultaneous quantification of T1, T2normall∗, T2normals∗, and T2∗ in addition to ΔB0. Methods 23Na‐MRF was implemented in a 3D sequence and irreducible spherical tensor operators were exploited in the simulations. Furthermore, the Cramér Rao lower bound was used to optimize the flip angle pattern. A combination of single and double echo readouts was implemented to increase the readout efficiency. A study was conducted to compare results in a multicompartment phantom acquired with MRF and reference methods. Finally, the relaxation times in the human brain were measured in four healthy volunteers. Results Phantom experiments revealed a mean difference of 1.0% between relaxation times acquired with MRF and results determined with the reference methods. Simultaneous quantification of the longitudinal and transverse relaxation times in the human brain was possible within 32 min using 3D 23Na‐MRF with a nominal resolution of (5 mm)3. In vivo measurements in four volunteers yielded average relaxation times of: T1,brain = (35.0 ± 3.2) ms, T2normall,brain∗ = (29.3 ± 3.8) ms and T2normals,brain∗ = (5.5 ± 1.3) ms in brain tissue, whereas T1,CSF = (61.9 ± 2.8) ms and T2,CSF∗ = (46.3 ± 4.5) ms was found in cerebrospinal fluid. Conclusion The feasibility of in vivo 3D relaxometric sodium mapping within roughly ½ h is demonstrated using MRF in the human brain, moving sodium relaxometric mapping toward clinically relevant measurement times.

The presented body coil enables full body width Na MRI with long z-axis coverage at 7 T for the first time. Additionally, the retrospective respiratory self-gating performance is demonstrated for free-breathing lung and abdominal Na MRI in 3 subjects.

C ancer cells predominantly gain energy through a high rate of glycolysis followed by lactic acid fermentation even in the presence of abundant oxygen (known as the Warburg effect). Consequently, both the higher glucose uptake rate and the reduced cerebral metabolic rate of oxygen (CMRO 2 ) consumption pose possible targets for imaging metabolic tumor activity.Conventional MRI sequences do not provide information on tissue metabolic activity. MR spectroscopy allows for the detection of metabolic products in vivo (eg, lactate) (1), but has limited routine applicability because of technical complexity, low spatial resolution, and clinical time constraints (2). Further, chemical exchange saturation transfer MRI has recently gained considerable attention as an imaging technique sensitive to tissue pH by amide proton transfer (3). However, recent studies (4) suggest that the endogenous amide contrast in tumors is dominated by histologic and genetic features through altered protein concentrations.Blood oxygen level2dependent imaging, most commonly applied to functional MRI, can be used to quantitatively measure CMRO 2 (5-7). However, these techniques provide only indirect measures and rely on complex physiologic assumptions in data interpretation and calibration processes (8), which impair robustness and specificity. Alternative approaches to assess tumor hypoxia are on the basis of PET or single photon emission CT, available with fluorine 18 fluoromisonidazole or other radioligands (9). Direct CMRO 2 assessment is possible by using the short-lived (~122 seconds) radioisotope oxygen 15 ( 15 O)