Coil combination of multichannel MRSI data at 7 T: MUSICAL

The goal of this study was to evaluate a new method of combining multi-channel 1H MRSI data by direct use of a matching imaging scan as a reference, rather than computing sensitivity maps. Seven healthy volunteers were measured on a 7-T MR scanner using a head coil with a 32-channel array coil for receive-only and a volume coil for receive/transmit. The accuracy of prediction of the phase of the 1H MRSI data with a fast imaging pre-scan was investigated with the volume coil. The array coil 1H MRSI data were combined using matching imaging data as coil combination weights. The signal-to-noise ratio (SNR), spectral quality, metabolic map quality and Cramér–Rao lower bounds were then compared with the data obtained by two standard methods, i.e. using sensitivity maps and the first free induction decay (FID) data point. Additional noise decorrelation was performed to further optimize the SNR gain. The new combination method improved significantly the SNR (+29%), overall spectral quality and visual appearance of metabolic maps, and lowered the Cramér–Rao lower bounds (−34%), compared with the combination method based on the first FID data point. The results were similar to those obtained by the combination method using sensitivity maps, but the new method increased the SNR slightly (+1.7%), decreased the algorithm complexity, required no reference coil and pre-phased all spectra correctly prior to spectral processing. Noise decorrelation further increased the SNR by 13%. The proposed method is a fast, robust and simple way to improve the coil combination in 1H MRSI of the human brain at 7 T, and could be extended to other 1H MRSI techniques. © 2013 The Authors. NMR in Biomedicine published by John Wiley & Sons, Ltd

Key clinical benefits of neuroimaging at 7 T

The growing interest in ultra-high field MRI, with more than 35.000 MR examinations already performed at 7 T, is related to improved clinical results with regard to morphological as well as functional and metabolic capabilities. Since the signal-to-noise ratio increases with the field strength of the MR scanner, the most evident application at 7 T is to gain higher spatial resolution in the brain compared to 3 T. Of specific clinical interest for neuro applications is the cerebral cortex at 7 T, for the detection of changes in cortical structure, like the visualization of cortical microinfarcts and cortical plaques in Multiple Sclerosis. In imaging of the hippocampus, even subfields of the internal hippocampal anatomy and pathology may be visualized with excellent spatial resolution. Using Susceptibility Weighted Imaging, the plaque-vessel relationship and iron accumulations in Multiple Sclerosis can be visualized, which may provide a prognostic factor of disease. Vascular imaging is a highly promising field for 7 T which is dealt with in a separate dedicated article in this special issue. The static and dynamic blood oxygenation level-dependent contrast also increases with the field strength, which significantly improves the accuracy of pre-surgical evaluation of vital brain areas before tumor removal. Improvement in acquisition and hardware technology have also resulted in an increasing number of MR spectroscopic imaging studies in patients at 7 T. More recent parallel imaging and short-TR acquisition approaches have overcome the limitations of scan time and spatial resolution, thereby allowing imaging matrix sizes of up to 128×128. The benefits of these acquisition approaches for investigation of brain tumors and Multiple Sclerosis have been shown recently. Together, these possibilities demonstrate the feasibility and advantages of conducting routine diagnostic imaging and clinical research at 7 T

Advanced MR techniques for preoperative glioma characterization: Part 1

Preoperative clinical magnetic resonance imaging (MRI) protocols for gliomas, brain tumors with dismal outcomes due to their infiltrative properties, still rely on conventional structural MRI, which does not deliver information on tumor genotype and is limited in the delineation of diffuse gliomas. The GliMR COST action wants to raise awareness about the state of the art of advanced MRI techniques in gliomas and their possible clinical translation or lack thereof. This review describes current methods, limits, and applications of advanced MRI for the preoperative assessment of glioma, summarizing the level of clinical validation of different techniques. In this first part, we discuss dynamic susceptibility contrast and dynamic contrast-enhanced MRI, arterial spin labeling, diffusion-weighted MRI, vessel imaging, and magnetic resonance fingerprinting. The second part of this review addresses magnetic resonance spectroscopy, chemical exchange saturation transfer, susceptibility-weighted imaging, MRI-PET, MR elastography, and MR-based radiomics applications. Evidence Level: 3 Technical Efficacy: Stage 2

Ethical reasoning during a pandemic: results of a five country European study

Introduction: There has been no work that identifies the hidden or implicit normative assumptions on which participants base their views during the COVID-19 pandemic, and their reasoning and how they reach moral or ethical judgements. Our analysis focused on participants’ moral values, ethical reasoning and normative positions around the transmission of SARS-CoV-2.Methods: We analyzed data from 177 semi-structured interviews across five European countries (Germany, Ireland, Italy, Switzerland and the United Kingdom) conducted in April 2020.Results: Findings are structured in four themes: ethical contention in the context of normative uncertainty; patterns of ethical deliberation when contemplating restrictions and measures to reduce viral transmission; moral judgements regarding “good” and “bad” people; using existing structures of meaning for moral reasoning and ethical judgement.Discussion: Moral tools are an integral part of people’s reaction to and experience of a pandemic. ‘Moral preparedness’ for the next phases of this pandemic and for future pandemics will require an understanding of the moral values and normative concepts citizens use in their own decision-making. Three important elements of this preparedness are: conceptual clarity over what responsibility or respect mean in practice; better understanding of collective mindsets and how to encourage them; and a situated, rather than universalist, approach to the development of normative standards

Ethical Reasoning During a Pandemic:Results of a Five Country European Study

Introduction: There has been no work that identifies the hidden or implicit normative assumptions on which participants base their views during the COVID-19 pandemic, and their reasoning and how they reach moral or ethical judgements. Our analysis focused on participants’ moral values, ethical reasoning and normative positions around the transmission of SARS-CoV-2.Methods: We analyzed data from 177 semi-structured interviews across five European countries (Germany, Ireland, Italy, Switzerland and the United Kingdom) conducted in April 2020.Results: Findings are structured in four themes: ethical contention in the context of normative uncertainty; patterns of ethical deliberation when contemplating restrictions and measures to reduce viral transmission; moral judgements regarding “good” and “bad” people; using existing structures of meaning for moral reasoning and ethical judgement.Discussion: Moral tools are an integral part of people’s reaction to and experience of a pandemic. ‘Moral preparedness’ for the next phases of this pandemic and for future pandemics will require an understanding of the moral values and normative concepts citizens use in their own decision-making. Three important elements of this preparedness are: conceptual clarity over what responsibility or respect mean in practice; better understanding of collective mindsets and how to encourage them; and a situated, rather than universalist, approach to the development of normative standards

Magnetic Resonance in Medicine / (2+1)DCAIPIRINHA accelerated MR spectroscopic imaging of the brain at 7T

Purpose To compare a new parallel imaging (PI) method for multislice proton magnetic resonance spectroscopic imaging (1HMRSI), termed (2+1)DCAIPIRINHA, with two standard PI methods: 2DGRAPPA and 2DCAIPIRINHA at 7 Tesla (T). Methods (2+1)DCAIPIRINHA is a combination of 2DCAIPIRINHA and sliceCAIPIRINHA. Eight healthy volunteers were measured on a 7T MR scanner using a 32channel head coil. The best undersampling patterns were estimated for all three PI methods. The artifact powers, gfactors, CramérRao lower bounds (CRLB), and root mean square errors (RMSE) were compared quantitatively among the three PI methods. Metabolic maps and spectra were compared qualitatively. Results (2+1)DCAIPIRINHA allows acceleration in three spatial dimensions in contrast to 2DGRAPPA and 2DCAIPIRINHA. Thus, this sequence significantly decreased the RMSE of the metabolic maps by 12.1 and 6.9%, on average, for 4<R<11, compared with 2DGRAPPA and 2DCAIPIRINHA, respectively. The artifact power was 22.6 and 8.4% lower, and the CRLB were 3.4 and 0.6% lower, respectively. Conclusion (2+1)CAIPIRINHA can be implemented for multislice MRSI in the brain, enabling higher accelerations than possible with twodimensional (2D) parallel imaging methods. An eightfold acceleration was still feasible in vivo with negligible PI artifacts with lipid decontamination, thus decreasing the measurement time from 120 to 15min for a 64644 matrix. Magn Reson Med 78:429440, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.(VLID)483935

Ultrashort-TE stimulated echo acquisition mode (STEAM) improves the quantification of lipids and fatty acid chain unsaturation in the human liver at 7 T

Ultrahigh-field, whole-body MR systems increase the signal-to-noise ratio (SNR) and improve the spectral resolution. Sequences with a short TE allow fast signal acquisition with low signal loss as a result of spin–spin relaxation. This is of particular importance in the liver for the precise quantification of the hepatocellular content of lipids (HCL). In this study, we introduce a spoiler Gradient-switching Ultrashort STimulated Echo AcqUisition (GUSTEAU) sequence, which is a modified version of a stimulated echo acquisition mode (STEAM) sequence, with a minimum TE of 6 ms. With the high spectral resolution at 7 T, the efficient elimination of water sidebands and the post-processing suppression of the water signal, we estimated the composition of fatty acids (FAs) via the detection of the olefinic lipid resonance and calculated the unsaturation index (UI) of hepatic FAs. The performance of the GUSTEAU sequence for the assessment of UI was validated against oil samples and provided excellent results in agreement with the data reported in the literature. When measuring HCL with GUSTEAU in 10 healthy volunteers, there was a high correlation between the results obtained at 7 and 3 T (R2 = 0.961). The test–retest measurements yielded low coefficients of variation for HCL (4 ± 3) and UI (11 ± 8) when measured with the GUSTEAU sequence at 7 T. A negative correlation was found between UI and HCL (n = 10; p < 0.033). The ultrashort TE MRS sequence (GUSTEAU; TE = 6 ms) provided high repeatability for the assessment of HCL. The improved spectral resolution at 7 T with the elimination of water sidebands and the offline water subtraction also enabled an assessment of the unsaturation of FAs. This all highlights the potential use of this MRS acquisition scheme for studies of hepatic lipid composition in vivo