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Chemical exchange saturation transfer (CEST) imaging is a novel contrast mechanism, relying on the exchange between mobile protons in amide (-NH), amine (-NH 2 ) and hydroxyl (-OH) groups and bulk water. Due to the targeted protons present in endogenous molecules or exogenous compounds applied externally, CEST imaging can respectively, generate endogenous or exogenous contrast. Nowadays, CEST imaging for endogenous contrast has been explored in pre-clinical and clinical studies. Amide CEST, also called amide proton transfer weighted (APT) imaging, generates CEST effect at 3.5 ppm away from the water signal and has been widely investigated. Given the sensitivity to amide proton concentration and pH level, APT imaging has shown robust performance in the assessment of ischemia, brain tumors, breast and prostate cancer as well as neurodegenerative diseases. With advanced methods proposed, pure APT and Nuclear Overhauser Effect (NOE) mediated CEST effects were separately fitted from original APT signal. Using both effects, early but promising results were obtained for glioma patients in the evaluation of tumor response to therapy and patient survival. Compared to amide CEST, amine CEST is also mobile proton concentration and pH dependent, but has a faster exchange rate between amine protons and water.The resultant CEST effect is usually introduced at 1.8-3 ppm. Glutamate and creatine, as two main metabolites with amine groups for CEST imaging, have been applied to quantitatively assess diseases in the central nervous system and muscle system, respectively. Glycosaminoglycan (Gag) as a representative metabolite with hydroxyl groups has also been measured to evaluate the cartilage of knee or intervertebral discs in CEST MRI. Due to limited frequency difference between hydroxyl protons and water, 7T for better spectral separation is preferred over 3T for GagCEST measurement. The applications of CEST MRI with exogenous contrast agents are still quite limited in clinic. While certain diamagnetic CEST agents, such as dynamic-glucose, have been tried in human for brain tumor or neck cancer assessment, most exogenous agents, i.e., paramagnetic CEST agents, are still tested in the pre-clinical stage, mainly due to potential toxicity. Engineered tissues for tissue regeneration and drug delivery have also shown a great potential in CEST imaging, as many of them, such as hydrogel and polyamide materials, contain mobile protons or can be incorporated with CEST specific chemical compounds. These engineered tissues can thus generate CEST effect in vivo, allowing a possibility to understand the fate of them in vivo longitudinally. Although the CEST MRI with engineered tissues has only been established in early stage, the obtained first evidence is crucial for further optimizing these biomaterials and finally accomplishing the translation into clinical use. 1748 Dou et al. CEST imaging and its pre-clinical and clinical applications

In order to examine the difference in brain structure between obese and normal weight individuals, and to explore the relationship between the neuroanatomical changes and impulsivity traits, this study used a voxel-based morphometry method to examine gray matter (GM) volume alterations related to impulsive personality traits in obese individuals relative to normal weight. Eighty adults that completed the UPPS-P Impulsive Behavior Scale were analyzed. Possible GM volume alterations were first analyzed at the whole brain level, and then the relationship between regional GM volume differences and UPPS-P scores were examined in selected regions of interest. Reduced GM volumes were found in the frontal and limbic regions in the obese group compared to normal weight individuals. In the normal weight group, lack of perseverance was negatively correlated with GM volume in the anterior cingulate cortex, and negative urgency was negatively correlated with GM volume in the insula. In the obese group, sensation seeking was negatively correlated with GM volume in the left amygdala and right pallidum. These findings might improve our understanding of the relationship between lack of perseverance, negative urgency, and sensation seeking and body weight fluctuations.

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Background 4D flow MRI shows great potential in neurovascular disorders such as stenosis, atherosclerotic disease, aneurysms, and vascular malformations. Its widespread application in the neurovascular system requires evidence of good test–retest multicenter reproducibility. Purpose To assess the multicenter reproducibility, test–retest reliability and interobserver dependence of 4D flow MRI in measurements of cerebral blood flow/velocity in main intracranial vessels. Study Type Prospective study. Subjects Ten healthy subjects underwent 4D flow scans at three different centers. All subjects were scanned twice at 2 different days at each center. Field Strength/Sequence 3.0 T; 4D flow sequence. Assessment Multicenter reproducibility, test–retest reliability and interobserver agreement for measurements of the blood flow and peak velocity from five regions of interest were assessed (bilateral internal carotid arteries, bilateral medial cerebral arteries, and sagittal sinus). Statistical Test A Shapiro–Wilks test was conducted to assess normality of measurements in each scan. Coefficient of variances (CVs) was computed to evaluate intra‐ and intersite variances of all measurements. The multicenter reproducibility was assessed by two‐way mixed intraclass correlation coefficient (ICC). A Bland–Altman plot and Pearson correlation were used to evaluate test–retest reliability. ICC was calculated to assess interobserver agreements. Results All P‐values for Shapiro–Wilks tests were greater than 0.05, which indicated the normality of all measurements. Both intra‐ and intersite CVs were lower than 12%. There was good test–retest reliability for both blood flow and peak velocity of all ROIs (r = 0.75–0.94). In addition, high multicenter reproducibility was detected (ICC = 0.77–0.96, all P < 0.001). The results of these measurements also showed great interobserver agreement (all ICC > 0.9 and all P < 0.001). Data Conclusion High multicenter reproducibility and test–retest reliability was shown for 4D flow in the measurements of blood flow and peak velocity of intracranial vessels. In addition, these measurements showed great interobserver agreement. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:1543–1552.