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Multipulse sodium magnetic resonance imaging for multicompartment quantification: Proof-of-concept

Gilles, Alina; Nagel, Armin M; Madelin, Guillaume
We present a feasibility study of sodium quantification in a multicompartment model of the brain using sodium (23Na) magnetic resonance imaging. The proposed method is based on a multipulse sequence acquisition and simulation at 7 T, which allows to differentiate the 23Na signals emanating from three compartments in human brain in vivo: intracellular (compartment 1), extracellular (compartment 2), and cerebrospinal fluid (compartment 3). The intracellular sodium concentration C 1 and the volume fractions α 1, α 2, and α 3 of all respective three brain compartments can be estimated. Simulations of the sodium spin 3/2 dynamics during a 15-pulse sequence were used to optimize the acquisition sequence by minimizing the correlation between the signal evolutions from the three compartments. The method was first tested on a three-compartment phantom as proof-of-concept. Average values of the 23Na quantifications in four healthy volunteer brains were α 1 = 0.54 ± 0.01, α 2 = 0.23 ± 0.01, α 3 = 1.03 ± 0.01, and C 1 = 23 ± 3 mM, which are comparable to the expected physiological values [Formula: see text] ∼ 0.6, [Formula: see text] ∼ 0.2, [Formula: see text] ∼ 1, and [Formula: see text] ∼ 10-30 mM. The proposed method may allow a quantitative assessment of the metabolic role of sodium ions in cellular processes and their malfunctions in brain in vivo.
PMID: 29234043
ISSN: 2045-2322
CID: 2844372

A flexible nested sodium and proton coil array with wideband matching for knee cartilage MRI at 3T

Brown, Ryan; Lakshmanan, Karthik; Madelin, Guillaume; Alon, Leeor; Chang, Gregory; Sodickson, Daniel K; Regatte, Ravinder R; Wiggins, Graham C
PURPOSE: We describe a 2 x 6 channel sodium/proton array for knee MRI at 3T. Multielement coil arrays are desirable because of well-known signal-to-noise ratio advantages over volume and single-element coils. However, low tissue-coil coupling that is characteristic of coils operating at low frequency can make the potential gains from a phased array difficult to realize. METHODS: The issue of low tissue-coil coupling in the developed six-channel sodium receive array was addressed by implementing 1) a mechanically flexible former to minimize the coil-to-tissue distance and reduce the overall diameter of the array and 2) a wideband matching scheme that counteracts preamplifier noise degradation caused by coil coupling and a high-quality factor. The sodium array was complemented with a nested proton array to enable standard MRI. RESULTS: The wideband matching scheme and tight-fitting mechanical design contributed to >30% central signal-to-noise ratio gain on the sodium module over a mononuclear sodium birdcage coil, and the performance of the proton module was sufficient for clinical imaging. CONCLUSION: We expect the strategies presented in this study to be generally relevant in high-density receive arrays, particularly in x-nuclei or small animal applications. Magn Reson Med, 2015. (c) 2015 Wiley Periodicals, Inc.
PMID: 26502310
ISSN: 1522-2594
CID: 1817442

A nested phosphorus and proton coil array for brain magnetic resonance imaging and spectroscopy

Brown, Ryan; Lakshmanan, Karthik; Madelin, Guillaume; Parasoglou, Prodromos
A dual-nuclei radiofrequency coil array was constructed for phosphorus and proton magnetic resonance imaging and spectroscopy of the human brain at 7T. An eight-channel transceive degenerate birdcage phosphorus module was implemented to provide whole-brain coverage and significant sensitivity improvement over a standard dual-tuned loop coil. A nested eight-channel proton module provided adequate sensitivity for anatomical localization without substantially sacrificing performance on the phosphorus module. The developed array enabled phosphorus spectroscopy, a saturation transfer technique to calculate the global creatine kinase forward reaction rate, and single-metabolite whole-brain imaging with 1.4cm nominal isotropic resolution in 15min (2.3cm actual resolution), while additionally enabling 1mm isotropic proton imaging. This study demonstrates that a multi-channel array can be utilized for phosphorus and proton applications with improved coverage and/or sensitivity over traditional single-channel coils. The efficient multi-channel coil array, time-efficient pulse sequences, and the enhanced signal strength available at ultra-high fields can be combined to allow volumetric assessment of the brain and could provide new insights into the underlying energy metabolism impairment in several neurodegenerative conditions, such as Alzheimer's and Parkinson's diseases, as well as mental disorders such as schizophrenia.
PMID: 26375209
ISSN: 1095-9572
CID: 1779282

Sodium inversion recovery MRI on the knee joint at 7 T with an optimal control pulse

Lee, Jae-Seung; Xia, Ding; Madelin, Guillaume; Regatte, Ravinder R
In the field of sodium magnetic resonance imaging (MRI), inversion recovery (IR) is a convenient and popular method to select sodium in different environments. For the knee joint, IR has been used to suppress the signal from synovial fluids, which improves the correlation between the sodium signal and the concentration of glycosaminoglycans (GAGs) in cartilage tissues. For the better inversion of the magnetization vector under the spatial variations of the B0 and B1 fields, the IR sequence usually employ adiabatic pulses as the inversion pulse. On the other hand, it has been shown that RF shapes robust against the variations of the B0 and B1 fields can be generated by numerical optimization based on optimal control theory. In this work, we compare the performance of fluid-suppressed sodium MRI on the knee joint in vivo, between one implemented with an adiabatic pulse in the IR sequence and the other with the adiabatic pulse replaced by an optimal-control shaped pulse. While the optimal-control pulse reduces the RF power deposited to the body by 58%, the quality of fluid suppression and the signal level of sodium within cartilage are similar between two implementations.
PMID: 26705907
ISSN: 1096-0856
CID: 1884392

Classification of sodium MRI data of cartilage using machine learning

Madelin, Guillaume; Poidevin, Frederick; Makrymallis, Antonios; Regatte, Ravinder R
PURPOSE: To assess the possible utility of machine learning for classifying subjects with and subjects without osteoarthritis using sodium magnetic resonance imaging data. THEORY: support vector machine, k-nearest neighbors, naive Bayes, discriminant analysis, linear regression, logistic regression, neural networks, decision tree, and tree bagging were tested. METHODS: Sodium magnetic resonance imaging with and without fluid suppression by inversion recovery was acquired on the knee cartilage of 19 controls and 28 osteoarthritis patients. Sodium concentrations were measured in regions of interests in the knee for both acquisitions. Mean (MEAN) and standard deviation (STD) of these concentrations were measured in each regions of interest, and the minimum, maximum, and mean of these two measurements were calculated over all regions of interests for each subject. The resulting 12 variables per subject were used as predictors for classification. RESULTS: Either Min [STD] alone, or in combination with Mean [MEAN] or Min [MEAN], all from fluid suppressed data, were the best predictors with an accuracy >74%, mainly with linear logistic regression and linear support vector machine. Other good classifiers include discriminant analysis, linear regression, and naive Bayes. CONCLUSION: Machine learning is a promising technique for classifying osteoarthritis patients and controls from sodium magnetic resonance imaging data. Magn Reson Med 74:1435-1448, 2015. (c) 2014 Wiley Periodicals, Inc.
PMID: 25367844
ISSN: 1522-2594
CID: 1816182

7T MRI detects deterioration in subchondral bone microarchitecture in subjects with mild knee osteoarthritis as compared with healthy controls

Chang, Gregory; Xia, Ding; Chen, Cheng; Madelin, Guillaume; Abramson, Steven B; Babb, James S; Saha, Punam K; Regatte, Ravinder R
PURPOSE: To determine how subchondral bone microarchitecture is altered in patients with mild knee osteoarthritis. MATERIALS AND METHODS: This study had Institutional Review Board approval. We recruited 24 subjects with mild radiographic knee osteoarthritis and 16 healthy controls. The distal femur was scanned at 7T using a high-resolution 3D FLASH sequence. We applied digital topological analysis to assess bone volume fraction, markers of trabecular number (skeleton density), trabecular network osteoclastic resorption (erosion index), plate-like structure (surface), rod-like structure (curve), and plate-to-rod ratio (surface-curve ratio). We used two-tailed t-tests to compare differences between osteoarthritis subjects and controls. RESULTS: 7T magnetic resonance imaging (MRI) detected deterioration in subchondral bone microarchitecture in both medial and lateral femoral condyles in osteoarthritis subjects as compared with controls. This was manifested by lower bone volume fraction (-1.03% to -5.43%, P < 0.04), higher erosion index (+8.49 to +22.76%, P < 0.04), lower surface number (-2.31% to -9.63%, P < 0.007), higher curve number (+6.85% to +16.93%, P < 0.03), and lower plate-to-rod ratio (-7.92% to -21.71%, P < 0.05). CONCLUSION: The results provide further support for the concept that poor subchondral bone quality is associated with osteoarthritis and may serve as a potential therapeutic target for osteoarthritis interventions.J. Magn. Reson. Imaging 2014. (c) 2014 Wiley Periodicals, Inc.
PMID: 24979471
ISSN: 1053-1807
CID: 1065652

Repeatability of quantitative sodium magnetic resonance imaging for estimating pseudo-intracellular sodium concentration and pseudo-extracellular volume fraction in brain at 3 T

Madelin, Guillaume; Babb, James; Xia, Ding; Regatte, Ravinder R
The purpose of this study is to assess the repeatability of the quantification of pseudo-intracellular sodium concentration (C1) and pseudo-extracellular volume fraction (alpha) estimated in brain in vivo using sodium magnetic resonance (MRI) at 3 T. Eleven healthy subjects were scanned twice, with two sodium MRI acquisitions (with and without fluid suppression by inversion recovery), and two double inversion recovery (DIR) proton MRI. DIR MRIs were used to create masks of gray and white matter (GM, WM), that were subsequently applied to the C1 and alpha maps calculated from sodium MRI and a tissue three-compartment model, in order to measure the distributions of these two parameters in GM, WM or full brain (GM+WM) separately. The mean, median, mode, standard deviation (std), skewness and kurtosis of the C1 and alpha distributions in whole GM, WM and full brain were calculated for each subject, averaged over all data, and used as parameters for the repeatability assessment. The coefficient of variation (CV) was calculated as a measure of reliability for the detection of intra-subject changes in C1 and alphafor each parameter, while intraclass correlation (ICC) was used as a measure of repeatability. It was found that the CV of most of the parameters was around 10-20% (except for C1 kurtosis which is about 40%) for C1 and alpha measurements, and that ICC was moderate to very good (0.4 to 0.9) for C1 parameters and for some of the alpha parameters (mainly skewness and kurtosis). In conclusion, the proposed method could allow to reliably detect changes of 50% and above of the different measurement parameters of C1 and alphain neuropathologies (multiple sclerosis, tumor, stroke, Alzheimer's disease) compared to healthy subjects, and that skewness and kurtosis of the distributions of C1 and alphaseem to be the more sensitive parameters to these changes.
PMID: 25751272
ISSN: 1932-6203
CID: 1495812

Sodium MRI: methods and applications

Madelin, Guillaume; Lee, Jae-Seung; Regatte, Ravinder R; Jerschow, Alexej
Sodium NMR spectroscopy and MRI have become popular in recent years through the increased availability of high-field MRI scanners, advanced scanner hardware and improved methodology. Sodium MRI is being evaluated for stroke and tumor detection, for breast cancer studies, and for the assessment of osteoarthritis and muscle and kidney functions, to name just a few. In this article, we aim to present an up-to-date review of the theoretical background, the methodology, the challenges, limitations, and current and potential new applications of sodium MRI.
PMID: 24815363
ISSN: 0079-6565
CID: 1042162

A method for estimating intracellular sodium concentration and extracellular volume fraction in brain in vivo using sodium magnetic resonance imaging

Madelin, Guillaume; Kline, Richard; Walvick, Ronn; Regatte, Ravinder R
In this feasibility study we propose a method based on sodium magnetic resonance imaging (MRI) for estimating simultaneously the intracellular sodium concentration (C1, in mM) and the extracellular volume fraction (alpha) in grey and white matters (GM, WM) in brain in vivo. Mean C1 over five healthy volunteers was measured ~11 mM in both GM and WM, mean alpha was measured ~0.22 in GM and ~0.18 in WM, which are in close agreement with standard values for healthy brain tissue (C1 ~ 10-15 mM, alpha ~ 0.2). Simulation of 'fluid' and 'solid' inclusions were accurately detected on both the C1 and alpha 3D maps and in the C1 and alpha distributions over whole GM and WM. This non-invasive and quantitative method could provide new biochemical information for assessing ion homeostasis and cell integrity in brain and help the diagnosis of early signs of neuropathologies such as multiple sclerosis, Alzheimer's disease, brain tumors or stroke.
PMID: 24755879
ISSN: 2045-2322
CID: 917982


Chapter by: Madelin, Guillaume; Chang, Gregory; Regatte, Ravinder R
pp. 273-303
CID: 2544682