Relaxometry and quantification in sodium MRI of cerebral gliomas: A FET‐PET and MRI small‐scale study

Abstract

Sodium MRI is a promising method for assessing the metabolic properties of brain tumours. In a recent study, a strong relationship between semi‐quantitative abnormalities in sodium MRI and the mutational status of the isocitrate dehydrogenase enzyme (IDH) with untreated cerebral gliomas was observed. Here, sodium relaxometry in brain tumour tissue was investigated in relation to molecular markers in order to reveal quantitative sodium tissue parameters and the differences between healthy tissue and brain tumour. The previous semi‐quantitative approach is extended by use of suitable relaxometry methods accompanied by numerical simulation to achieve detailed quantitative analysis of intra‐ and extracellular sodium concentration using an enhanced SISTINA sequence at 4 T. Using optimised techniques, biexponential sodium relaxation times in tumour (T*2f, T*2s) and in healthy contralateral brain tissue (T*2f,CL, T*2s,CL) were estimated in 10 patients, along with intracellular sodium molar fractions (χ, χCL), volume fractions (η, ηCL) and concentrations (ρin, ρin,CL). The total sodium tissue concentrations (ρT, ρT,CL) were also estimated. The ratios T*2f/T*2f,CL (P = .05), η/ηCL (P = .02) and χ/χCL (P = .02) were significantly lower in IDH mutated than in IDH wildtype gliomas (n = 4 and n = 5 patients, respectively). The Wilcoxon rank‐sum test was used to compare sodium MRI parameters in patients with and without IDH mutation. Thus, quantitative analysis of relaxation rates, intra‐ and extracellular sodium concentrations, intracellular molar and volume fractions based on enhanced SISTINA confirmed a relationship between abnormalities in sodium parameters and the IDH mutational status in cerebral gliomas, hence catering for the potential to provide further insights into the status of the disease.

Compressed Sensing in Sodium Magnetic Resonance Imaging: Techniques, Applications, and Future Prospects

“…Several approaches have been proposed for intracellular sodium weighted acquisitions in human biology, such as inversion‐recovery techniques for suppression of the sodium signal from an aqueous environment, 122–124 and multiple‐quantum filtering 125–129 based on the assumption that triple‐quantum‐coherence sodium NMR signal mostly originates from a restricted (mainly intracellular) environment 19,20 . Figure 9 presents the single‐ and triple‐quantum‐filtered sodium images on a brain tumor patient by applying an enhanced SISTINA technique 9,10,44 . The brain tumor shows increased signal in the single‐quantum‐filtered image and yet a decrease in the triple‐quantum‐filtered image, indicating that multiple‐quantum filtering might have the potential to provide complementary information for diagnosis or medical treatment of some diseases.…”

“…19,20 Figure 9 presents the single-and triple-quantum-filtered sodium images on a brain tumor patient by applying an enhanced SISTINA technique. 9,10,44 The brain tumor shows increased signal in the single-quantum-filtered image and yet a decrease in the triplequantum-filtered image, indicating that multiple-quantum filtering might have the potential to provide complementary information for diagnosis or medical treatment of some diseases. However, these techniques suffer from even longer acquisition times than conventional single-pulse sodium MRI due to their generally large specific absorption rate requirements, thus arousing interest in the acceleration of intracellular sodium mapping while maintaining image quality by using CS-based methods.…”

“…Initial demonstrations of the feasibility of sodium MRI in the human body date back to the early 1980s 7,8 . With the availability of stronger magnetic fields (≥3 T) as well as advancements in acquisition strategies and hardware, the potential of sodium MRI has been investigated in many recent studies across a variety of diseases, ranging from brain tumors, 9,10 multiple sclerosis, 11,12 stroke, 13 osteoarthritis, 14 and breast cancer, 15,16 to nephropathy, 17 and others 4,5 …”

“…36 Recent efforts have been made to further advance CS sodium MRI by incorporating methods such as dictionary-based learning, 36,37 prior hydrogen anatomical constraint, 32 parallel imaging, 38 or deep learning. 39 As an emerging technique, CS has great potential in further facilitating the clinical applicability of sodium MRI by, for example, applying advanced incoherent undersampling methods, 27,40,41 or by accelerating intracellular sodium mapping, 42,43 quantitative relaxometry, 9,10,44 and dynamic sodium MRI. 45,46 Sodium MRI methods and applications have been extensively reviewed elsewhere, 4,5,47,48 and there are multiple reviews on the CS techniques and applications in hydrogen MRI.…”

23Na MRI in ischemic stroke: Acquisition time reduction using postprocessing with convolutional neural networks

“…Sodium magnetic resonance imaging ( 23 Na MRI) provides information about physiological and biochemical processes related to cell vitality and viability that cannot be achieved by 1 H MRI alone. 1 23 Na MRI can enable the quantification of the tissue sodium concentration (TSC) [2][3][4] of the human brain and has been proposed previously for the diagnosis of pathologies defined by a change in cell behavior, vitality or density in pathologies, such as stroke, [5][6][7] malignant tumors [8][9][10][11] or multiple sclerosis. [12][13][14] Furthermore, additional applications of 23 Na MRI have emerged, for example, quantitative relaxometry and distinguishing between intracellular and extracellular space.…”