Advanced MR Techniques for Preoperative Glioma Characterization: Part 2.

Preoperative clinical 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. 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 second part, we review magnetic resonance spectroscopy (MRS), chemical exchange saturation transfer (CEST), susceptibility-weighted imaging (SWI), MRI-PET, MR elastography (MRE), and MR-based radiomics applications. The first part of this review addresses dynamic susceptibility contrast (DSC) and dynamic contrast-enhanced (DCE) MRI, arterial spin labeling (ASL), diffusion-weighted MRI, vessel imaging, and magnetic resonance fingerprinting (MRF). EVIDENCE LEVEL: 3. TECHNICAL EFFICACY: Stage 2.

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.

Social jetlag and sleep deprivation are associated with altered activity in the reward-related brain areas: an exploratory resting-state fMRI study.

OBJECTIVE: The aim of this research was to assess the effect of social jetlag (SJL) and its interaction with partial sleep deprivation on resting-state brain activity using the fractional amplitude of low-frequency fluctuation (fALFF) during free-living conditions. METHODS: A total of 28 normal weight healthy subjects were enrolled in four study groups (with SJL [with sleep deprivation and without sleep deprivation] and without SJL [with sleep deprivation and without sleep deprivation]), matched 1:1:1:1 for age, gender, and body mass index (BMI). Resting-state functional magnetic resonance imaging (fMRI) scans were collected with SIEMENS 3T scanner while subjects were in a fasting state. RESULTS: Participants with SJL had significantly higher fALFF values in right lingual gyrus and right putamen and significantly lower fALFF values in left and right inferior parietal lobe in comparison with participants without SJL and without sleep deprivation. Subjects with sleep deprivation had significantly higher fALFF in the thalamus and left superior frontal gyrus. In those with both SJL and sleep deprivation, we observed higher fALFF values in right Brodmann Area (BA)18 and lower values in left and right parietal inferior lobe. Subjects with SJL alone had significantly lower fALFF values in left frontal mid gyrus (BA6) than those with sleep deprivation alone. CONCLUSIONS: SJL was associated with altered resting-state brain activity in regions that have been shown to be involved in hedonic feeding. The effect of SJL was independent of effects induced by short sleep duration. These alterations might represent the substrate for the increased risk of obesity observed in those with SJL.

Spatially resolved measurements of mean spin-spin relaxation time constants.

Magnetic Resonance measurements of the T2 distribution have become very common and they are a powerful way to probe microporous fluid bearing solids. While the structure of the T2 distribution, and changes in the structure, are often very informative, it is common to reduce the T2 distribution to a mean numeric quantity in order to provide a quantitative interpretation of the distribution. Magnetic Resonance Imaging measurements of the T2 distribution have recently been introduced, but they are time consuming, especially for 2 and 3 spatial dimensions. In this paper we explore a direct MRI measurement of the arithmetic mean of 1/T2, characterizing the distribution by using the initial slope of the spatially resolved T2 decay in a CPMG prepared Centric Scan SPRITE experiment. The methodology is explored with a test phantom sample and realistic petroleum reservoir core plug samples. The arithmetic mean of 1/T2 is related to the harmonic mean of T2. The mean obtained from the early decay is explored through measurements of uniform saturated core plug samples and by comparison to other means determined from the complete T2 distribution. Complementary data were obtained using SE-SPI T2 distribution MRI measurements. The utility of the arithmetic mean 1/T2 is explored through measurements of centrifuged core plug samples where the T2 distribution varies spatially. The harmonic mean T2 obtained from the early decay was employed to estimate the irreducible water saturation for core plug samples.