Hemodialysis Patients with Cardiovascular Disease Reveal Increased Tissue Na+ Deposition

Background: The relationship between Na+ balance and cardiovascular disease (CVD) in hemodialysis (HD) patients is not yet fully understood. We hypothesized that HD patients co-diagnosed with CVD show increased tissue Na+ accumulation compared to HD patients without CVD. Methods: In our observational study 52 HD patients were divided into a group with (23 subjects) or without (29 subjects) a positive history of cardiovascular events. We used 23Na-Magnetic Resonance Imaging (23Na-MRI) at 3.0 Tesla to quantify Na+ content in skin and muscle of both groups directly before and after HD. Additionally, total body fluid distribution was determined by Bioimpedance Spectroscopy (BIS) and laboratory parameters were assessed. Results: Compared to HD patients without CVD, 23Na-MRI detected an increased Na+ content in skin (21.7 ± 7.3 vs. 30.2 ± 9.8 arbitrary units, a.u., p < 0.01) and muscle tissue (21.5 ± 3.6 vs 24.7 ± 6.0 a.u., p < 0.05) in patients with previous CVD events. Simultaneously measured fluid amount by BIS, including excess extracellular water (1.8 ± 1.7 vs. 2.2 ± 1.7 L, p = 0.44), was not significantly different between both groups. Tissue Na+ accumulation in HD-CVD patients was paralleled by a higher plasma concentration of the inflammation marker Interleukin-6 (5.1, IQR 5.8 vs. 8.5, IQR 7.9 pg/ml, p < 0.05). Conclusion: In our cohort, HD patients with CVD showed higher tissue Na+ content than HD patients without CVD, while no difference in body water distribution could be detected between both groups. Our findings provide evidence that the history of a cardiovascular event is associated with disturbances in tissue Na+ content in HD patients.

7 Tesla Chlorine (35Cl) and Sodium (23Na) MR Imaging of an Enchondroma

We demonstrated the feasibility of 7 Tesla sodium (23Na) and chlorine (35Cl) MRI of a solitary enchondroma. For this, we established dedicated sequences on a 7-Tesla whole-body system with the following key parameters for 35Cl MRI: TE/TR = 0.35/60 ms, TRO = 5 ms, α = 90°, Δx3 = (6 mm)3, 3 averages, Tacq = 30 min and for 23Na MRI: TE/TR = 0.4/101 ms, TRO = 10ms; α = 90°; Δx3 = (1.9 mm)3, 3 averages, Tacq = 30 min 18 s. The measured apparent Na+ concentration was 255 mmol/l and was approximately 7-fold higher than the apparent Cl– concentration with about 36 mmol/l. Additionally, repeated proton MRI examinations demonstrated constant but subtle growth (≈ 0.65 ml/year) over 14 years. In conclusion, enchondromas obviously have a high contrast-to-noise ratio when compared with the normal bone marrow in 23Na and 35Cl MRI, which may contribute to detection and differentiation in unclear or subtle cases. Key Points: Citation Format

EPCT-20. TECHNICAL FEASIBILITY SODIUM (23NA) MRI OF PEDIATRIC GLIOMAS

Pediatric glioma response to novel targeted therapy can be heterogeneous on conventional proton (1H) MRI. Sodium concentration, as measured with 23Na MRI in adult brain tumors can provide complementary assessment of tumor proliferation to conventional MRI. However, 23Na MRI pediatric brain tumor studies are lacking. Determine the technical feasibility of performing sodium23Na MRI on pediatric glioma patients. Prospective study of an immunotherapy trial for newly diagnosed and recurrent gliomas (high-grade gliomas, low-grade gliomas, brainstem gliomas) in which participants were imaged with 23Na MRI at 3.0 Tesla. The participants (n=26, 14 males) with median age of 11 years (range = 4–23 years of age) were prospectively evaluated with sodium. 23Na MRI is technically feasible in the pediatric population and can distinguish different types of pediatric gliomas at baseline.

Tissue Sodium Concentration within White Matter Correlates with the Extent of Small Vessel Disease

Introduction: Sodium MRI (23Na MRI) derived biomarkers such as tissue sodium concentration (TSC) provide valuable information on cell function and brain tissue viability and has become a reliable tool for the assessment of brain tumors and ischemic stroke beyond pathoanatomical morphology. Patients with major stroke often suffer from different degrees of underlying white matter lesions (WMLs) attributed to chronic small vessel disease. This study aimed to evaluate the WM TSC in patients with an acute ischemic stroke and to correlate the TSC with the extent of small vessel disease. Furthermore, the reliability of relative TSC (rTSC) compared to absolute TSC in these patients was analyzed. Methodology: We prospectively examined 62 patients with acute ischemic stroke (73 ± 13 years) between November 2016 and August 2019 from which 18 patients were excluded and thus 44 patients were evaluated. A 3D 23Na MRI was acquired in addition to a T2-TIRM and a diffusion-weighted image. Coregistration and segmentation were performed with SPM 12 based on the T2-TIRM image. The extension of WM T2 hyperintense lesions in each patient was classified using the Fazekas scale of WMLs. The absolute TSC in the WM region was correlated to the Fazekas grades. The stroke region was manually segmented on the coregistered absolute diffusion coefficient image and absolute, and rTSC was calculated in the stroke region and compared to nonischemic WM region. Statistical significance was evaluated using the Student t-test. Results: For patients with Fazekas grade I (n = 25, age: 68.5 ± 15.1 years), mean TSC in WM was 55.57 ± 7.43 mM, and it was not statistically significant different from patients with Fazekas grade II (n = 7, age: 77.9 ± 6.4 years) with a mean TSC in WM of 53.9 ± 6.4 mM, p = 0.58. For patients with Fazekas grade III (n = 9, age: 81.4 ± 7.9 years), mean TSC in WM was 68.7 ± 10.5 mM, which is statistically significantly higher than the TSC in patients with Fazekas grade I and II (p < 0.001 and p = 0.05, respectively). There was a positive correlation between the TSC in WM and the Fazekas grade with r = 0.48 p < 0.001. The rTSC in the stroke region was statistically significant difference between low (0 and I) and high (2 and 3) Fazekas grades (p = 0.0353) whereas there was no statistically significant difference in absolute TSC in the stroke region between low (0 and I) and high (2 and 3) Fazekas grades. Conclusion: The significant difference in absolute TSC in WM in patients with severe small vessel disease; Fazekas grade 3 can lead to inaccuracies using rTSC quantification for evaluation of acute ischemic stroke using 23 Na MRI. The study, therefore, emphasizes the importance of absolute tissue sodium quantification.

Sodium (23Na) MRI of the Kidney: Basic Concept

The handling of sodium by the renal system is a key indicator of renal function. Alterations in the corticomedullary distribution of sodium are considered important indicators of pathology in renal diseases. The derangement of sodium handling can be noninvasively imaged using sodium magnetic resonance imaging (23Na MRI), with data analysis allowing for the assessment of the corticomedullary sodium gradient. Here we introduce sodium imaging, describe the existing methods, and give an overview of preclinical sodium imaging applications to illustrate the utility and applicability of this technique for measuring renal sodium handling.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.

23Na MRI on 0,5T clinical scanner

Object. The purpose of this work is to reveal the possibilities of low-field 23Na MRI. It was supposed to obtain images of various human organs using the 3D-scanning method, and to do this with minimal hardware modifications of a typical clinical 0,5T scanner. Materials and methods. The proprietary receiving coils, originally intended for registering proton signals (21,1 MHz), were transformed to transceiver ones and tuned to the sodium Larmor frequency of 5,6 MHz. The scanning was carried out by the 3D-gradient echo method with the parameters: TR/TE=44,7/12 ms, FA=45° and isotropic resolution of 6 mm. To increase SNR, apodization in k-space was applied during data processing. Results. 23Na MRI (including volumetric reconstructions) of several human organs – head, breast, heart, joints were obtained with SNR up to 15. Discussion. When developing low-field 23Na MRI, it is advisable to focus on recording only the T2long component (>15 ms). In this case, it is possible to narrow the receiver bandwidth as much as possible and thereby minimize noise. In addition, the requirements for the transmission path are reduced. As a result, for debugging MRI methods, the equipment of a typical clinical scanner, which is supplemented by coils tuned to the sodium NMR frequency only, can be used.

Sodium (23Na) MRI of the Kidney: Experimental Protocol

Sodium handling is a key physiological hallmark of renal function. Alterations are generally considered a pathophysiologic event associated with kidney injury, with disturbances in the corticomedullary sodium gradient being indicative of a number of conditions. This experimental protocol review describes the individual steps needed to perform 23Na MRI; allowing accurate monitoring of the renal sodium distribution in a step-by-step experimental protocol for rodents.This chapter is based upon work from the PARENCHIMA COST Action, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis.

Registration of weak MRI signals when exposed to radio frequency interference

The problems of registration of weak magnetic resonance (MR) signals in conditions of technogenic interference are considered. Their intensity and temporal activity are analyzed by MRI tomography. To reduce their influence on the result of long-term signal accumulation, it is proposed to save its individual realizations during registration. Then, at the end of registration, it is possible analyze them, identify noisy implementations, edit them, and submit edited copies for summing up instead of noisy ones. An approach that is similar in concept is considered for practical application in MRI – instead of increasing the number of accumulations, it is proposed to increase the number of phase encoding steps. Examples of analysis of interference activity during 23Na MRI scanning of various human organs using various coils are given. The possibility of increasing the information content of MRI data by using apodization for kspace data is shown, and this technique is most effective if the effect of noise occurs when only the peripheral part of this space is filled.