Chemical Shift Effects Research Articles

Contrast-enhanced Susceptibility Weighted Imaging (CE-SWI) for the Characterization of Musculoskeletal Oncologic Pathology: A Pictorial Essay on the Initial Five-year Experience at a Cancer Institution

Susceptibility-weighted imaging (SWI) is based on a 3D high-spatial-resolution, velocity-corrected gradient-echo MRI sequence that uses magnitude and filtered-phase information to create images. It SWI uses tissue magnetic susceptibility differences to generate signal contrast that may arise from paramagnetic (hemosiderin), diamagnetic (minerals and calcifications) and ferromagnetic (metal) molecules. Distinguishing between calcification and blood products is possible through the filtered phase images, helping to visualize osteoblastic and osteolytic bone metastases or demonstrating calcifications and osteoid production in liposarcoma and osteosarcoma. When acquired in combination with the injection of an exogenous contrast agent, contrast-enhanced SWI (CE-SWI) can simultaneously detect the T2* susceptibility effect, T2 signal difference, contrast-induced T1 shortening, and out-of-phase fat and water chemical shift effect. Bone and soft tissue lesion SWI features have been described, including giant cell tumors in bone and synovial sarcomas in soft tissues. We expand on the appearance of benign soft-tissue lesions such as hemangioma, neurofibroma, pigmented villonodular synovitis, abscess, and hematoma. Most myxoid sarcomas demonstrate absent or just low-grade intra-tumoral hemorrhage at the baseline. CE-SWI shows superior differentiation between mature fibrotic T2* dark components and active enhancing T1 shortening components in desmoid fibromatosis. SWI has gained popularity in oncologic MSK imaging because of its sensitivity for displaying hemorrhage in soft tissue lesions, thereby helping to differentiate benign versus malignant soft tissue tumors. The ability to show the viable, enhancing portions of a soft tissue sarcoma separately from hemorrhagic/necrotic components also suggests its utility as a biomarker of tumor treatment response. It is essential to understand and appreciate the differences between spontaneous hemorrhage patterns in high-grade sarcomas and those occurring in the therapy-induced necrosis process in responding tumors. Ring-like hemosiderin SWI pattern is observed in successfully treated sarcomas. CE-SWI also demonstrates early promising results in separating the T2* blooming of healthy iron-loaded bone marrow from the T1-shortened enhancement in bone marrow that is displaced by the tumor. SWI and CE-SWI in MSK oncology learning objectives: SWI and CE-SWI can be used to identify calcifications on MRI. Certain SWI and CE-SWI patterns can correlate with tumor histologic type. CE-SWI can discriminate mature from immature components of desmoid tumors. CE-SWI patterns can help to assess treatment response in soft tissue sarcomas. Understanding CE-SWI patterns in post-surgical changes can also be useful in discriminating between residual and recurrent tumors with overlapping imaging features.

Composites of equiatomic Y, La, Ce, Nd, and Gd rare earth oxides: Chemical-shift effects and valence spectra

The core-electron and valence spectra of the composites of equiatomic rare earth oxides (equi-REO) were investigated using XPS. Equi-REOs fabricated by annealing at 1600 °C for 10 h after the synthesis by mechanical ball-milling and chemical sol-gel methods, exhibited the FCC bixbyite single phase. It was confirmed that Y and La sites had the higher oxidation state (Y > 3+ and La>3+) than Y2O3 (Y3+) and La2O3 (La3+), respectively, and both Gd and Nd sites had the lower oxidation state (Gd < 3+ and Nd<3+) than Gd2O3(Gd3+) and Nd2O3(Nd3+), one the other hand, in the Ce site, Ce3+ was increased compared to CeO2, and Ce3+ and Ce4+ were mixed. There were a significant changes in the electron DOS associated with O 2p – 4f hybridizations in the equi-REOs compared to the ideal mixture. Finally, we found that the chemical sol-gel process induces more changes of chemical and electronic states of the equi-REO than the mechanical ball milling process.

Modified PSYCHE NMR - The possibility for the direct semi-quantitation of components in mixtures

A series of commonly occurring biologically relevant compounds were analysed using internally referenced PSYCHE NMR and the accuracy/precision compared with that achieved using conventional qNMR. The effect of chemical shift, coupling constants, swept frequency pulse angle, excitation sculpting and the impact of signal overlap in mixtures was evaluated in terms of statistically significant variation between the two techniques. It is shown that suitably optimised PSYCHE NMR represents a potentially reliable method for the semi-quantitation of mixtures of compounds, whose spectroscopic signals overlap in conventional qNMR analysis and hence cannot be accurately quantified with that technique. This is of particular relevance for complex mixtures of natural products. Of particular note is the effect of the excitation sculpting block introduced to supress baseline artefacts.

Efficient polarization redistribution in hyperpolarized 1-D-propane produced via pairwise parahydrogen addition

Parahydrogen-Induced Polarization (PHIP) is NMR hyperpolarization technique that has matured from fundamental science to a biomedical tool for production of hyperpolarized MRI contrast agents. The spin order of nascent parahydrogen-derived protons can be employed directly for enhancement of their NMR signals or for polarization transfer to other nuclei in the hydrogenation product. In this work, we study the process of pairwise parahydrogen addition to propylene, which results in symmetric propane molecule with substantially enhanced methyl and methylene NMR signals. Specifically, we have synthesized site-selectively isotopically labeled 3-d-propylene molecule to study polarization dynamics in the resulting monodeuterated propane after pairwise parahydrogen addition. The deuterium presence in the hyperpolarized propane product results in a minute isotope chemical shift effect allowing to distinguish the proton resonances of CH3 and CH2D groups at 600 MHz. Pairwise parahydrogen 1,2-addition to 3-d-propylene was first confirmed by performing the reaction inside a 600 MHz NMR spectrometer, i.e., in the weakly-coupled regime at 14 T, where proton polarization dynamics is restricted to the molecular sites of parahydrogen addition. However, when the pairwise parahydrogen addition is performed in the strongly-coupled regime, i.e., at the Earth's magnetic field, efficient polarization transfer to CH2D protons is readily observed, leading to polarization redistribution between the three inequivalent sites. This finding is important as it sheds light on polarization dynamics in the strongly coupled symmetric spin systems such as propane studied here—the presented results are expected to be applicable to other spin systems such as butane.

Reducing the ambiguity of field inhomogeneity and chemical shift effect for fat-water separation by field factor.

To reduce the ambiguity between chemical shift and field inhomogeneity with flexible TE combinations by introducing a variable (field factor). The ambiguity between chemical shift and field inhomogeneity can be eliminated directly from the multiple in-phase images acquired at different TEs; however, it is only applicable to few echo combinations. In this study, we accommodated such an implementation in flexible TE combinations by introducing a new variable (field factor). The effects of the chemical shift were removed from the field inhomogeneity in the candidate solutions, thus reducing the ambiguity problem. To validate this concept, multi-echo MRI data acquired from various anatomies with different imaging parameters were tested. The derived fat and water images were compared with those of the state-of-the-art fat-water separation algorithms. Robust fat-water separation was achieved with the accurate solution of field inhomogeneity, and no apparent fat-water swap was observed. In addition to the good performance, the proposed method is applicable to various fat-water separation applications, including different sequence types and flexible TE choices. We propose an algorithm to reduce the ambiguity of chemical shift and field inhomogeneity and achieved robust fat-water separation in various applications.

QSM Throughout the Body.

Magnetic materials in tissue, such as iron, calcium, or collagen, can be studied using quantitative susceptibility mapping (QSM). To date, QSM has been overwhelmingly applied in the brain, but is increasingly utilized outside the brain. QSM relies on the effect of tissue magnetic susceptibility sources on the MR signal phase obtained with gradient echo sequence. However, in the body, the chemical shift of fat present within the region of interest contributes to the MR signal phase as well. Therefore, correcting for the chemical shift effect by means of water-fat separation is essential for body QSM. By employing techniques to compensate for cardiac and respiratory motion artifacts, body QSM has been applied to study liver iron and fibrosis, heart chamber blood and placenta oxygenation, myocardial hemorrhage, atherosclerotic plaque, cartilage, bone, prostate, breast calcification, and kidney stone.

Super-resolved reconstruction method for spatiotemporally encoded magnetic resonance imaging based on deep neural network

Single-shot spatiotemporally-encoded magnetic resonance imaging (SPEN MRI) is a novel ultrafast MRI technology. The SPEN MRI possesses great resistance to inhomogeneous &lt;i&gt;B&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt; magnetic field and chemical shift effect. However, it has inherently low spatial resolution, and the super-resolved reconstruction is required to improve the spatial resolution of SPEN MRI image without additional signal acquisition. Several super-resolved reconstruction methods have been proposed, but they all suffer the problems of long iterative solution time and/or aliasing artifacts residue in the reconstructed results. In this paper, a super-resolved reconstruction method is proposed for single-shot SPEN MRI based on deep neural network. In this method the simulation samples are used to train the deep neural network, and then the trained network model is adopted to reconstruct the real sampled signals. Experimental results of numerical simulation, water phantom and in vivo rat brain show that this method can quickly reconstruct a super-resolved SPEN image with no residual aliasing artifacts, and clear texture information. An appropriate number of training samples and an appropriate random noise level for training samples contribute to improving the reconstruction results.

Phosphate uptake by calcite: Constraints of concentration and pH on the formation of calcium phosphate precipitates

The uptake of phosphate by carbonates plays an important role in controlling the fate and transport of phosphorus in soil, but the mechanisms are not fully understood. In this study, 31P solid-state NMR was used to investigate the mechanisms of phosphate uptake by calcite over wide pH (6–10) and concentration (5 μM – 10 mM) ranges. It was found that calcium phosphate precipitates formed at very low phosphate concentrations (~ 50 μM, pH 8). Because of their low yield and poor crystallinity, the precipitates were not directly detected by powder X-ray diffraction (XRD) but were unequivocally identified by a single NMR peak at δP-31 = ~2.9 ppm. This peak was assigned to carbonated hydroxyapatite (CHap) based on further characterization with 2-D 31P{1H} heterogeneous correlation (HetCor) experiments and high-resolution transmission electron microscopy (HRTEM). When [PO43−] was below 30 μM at pH 8, a broad peak at δP-31 = ~4.0 ppm was observed with an FWHM of ~5 ppm; this was assigned to surface adsorbed phosphate on calcite owing to its distinct chemical shift and insignificant 31P-1H cross-polarization (CP) effect. Additionally, we found that the presence of a small amount of dissolved fluoride facilitated the formation of carbonate fluorapatite (CFap), implying that calcite dissolution plays an important role in phosphate sequestration. This study indicated that calcite may be effective for mobilization dissolved phosphate and lowering its bioavailability in aquatic and soil systems.

A magnetic resonance imaging (MRI)-based nomogram for predicting lymph node metastasis in rectal cancer: a node-for-node comparative study of MRI and histopathology.

The aim of the present study was to investigate the potential risk factors for lymph node metastasis (LNM) in rectal cancer using magnetic resonance imaging (MRI), and to construct and validate a nomogram to predict its occurrence with node-for-node histopathological validation. Our prediction model was developed between March 2015 and August 2016 using a prospective primary cohort (32 patients, mean age: 57.3 years) that included 324 lymph nodes (LNs) from MR images with node-for-node histopathological validation. We evaluated multiple MRI variables, and a multivariable logistic regression analysis was used to develop the predictive nomogram. The performance of the nomogram was assessed with respect to its calibration, discrimination, and clinical usefulness. The performance of the nomogram in predicting LNM was validated in an independent clinical validation cohort comprising 182 consecutive patients. The predictors included in the individualized prediction nomogram were chemical shift effect (CSE), nodal border, short-axis diameter of nodes, and minimum distance to rectal cancer or rectal wall. The nomogram showed good discrimination (C-index: 0.947; 95% confidence interval: 0.920-0.974) and good calibration in the primary cohort. Decision curve analysis confirmed the clinical usefulness of the nomogram in predicting the status of each LN. For the prediction of LN status in the clinical validation cohort by readers 1 and 2, the areas under the curves using the nomogram were 0.890 and 0.841, and the areas under the curves of readers using their experience were 0.754 and 0.704, respectively. Diagnostic efficiency was significantly improved by using the nomogram (P<0.001). The nomogram, which incorporates CSE, nodal location, short-axis diameter, and minimum distance to rectal cancer or rectal wall, can be conveniently applied in clinical practice to facilitate the prediction of LNM in patients with rectal cancer.

Preoperative volumetric synthetic magnetic resonance imaging of the primary tumor for a more accurate prediction of lymph node metastasis in rectal cancer.

An accurate assessment of lymph node (LN) status in patients with rectal cancer is important for treatment planning and an essential factor for predicting local recurrence and overall survival. In this study, we explored the potential value of histogram parameters of synthetic magnetic resonance imaging (SyMRI) in predicting LN metastasis in rectal cancer and compared their predictive performance with traditional morphological characteristics and chemical shift effect (CSE). A total of 70 patients with pathologically proven rectal adenocarcinoma who received direct surgical resection were enrolled in this prospective study. Preoperative rectal MRI, including SyMRI, were performed, and morphological characteristics and CSE of LN were assessed. Histogram parameters were extracted on a T1 map, T2 map, and proton density (PD) map, including mean, variance, maximum, minimum, 10th percentile, median, 90th percentile, energy, kurtosis, entropy, and skewness. Receiver operating characteristic (ROC) curves were used to explore their predictive performance for assessing LN status. Significant differences in the energy of the T1, T2, and PD maps were observed between LN-negative and LN-positive groups [all P<0.001; the area under the ROC curve (AUC) was 0.838, 0.858, and 0.823, respectively]. The maximum and kurtosis of the T2 map, maximum, and variance of PD map could also predict LN metastasis with moderate diagnostic power (P=0.032, 0.045, 0.016, and 0.047, respectively). Energy of the T1 map [odds ratio (OR) =1.683, 95% confidence interval (CI): 1.207-2.346, P=0.002] and extramural venous invasion on MRI (mrEMVI) (OR =10.853, 95% CI: 2.339-50.364, P=0.002) were significant predictors of LN metastasis. Moreover, the T1 map energy significantly improved the predictive performance compared to morphological features and CSE (P=0.0002 and 0.0485). The histogram parameters derived from SyMRI of the primary tumor were associated with LN metastasis in rectal cancer and could significantly improve the predictive performance compared with morphological features and CSE.

Very low field 19F MRI of perfluoro-octylbromide: Minimizing chemical shift effects and signal loss due to scalar coupling

19F images have been obtained from perflurooctylbromide (PFOB) at very low magnetic field (50 mT). The small spectral dispersion (in Hz) means that all fluorine nuclei contribute to the signal without chemical shift artifacts or the need for specialized imaging sequences. Turbo spin echo trains with short interpulse intervals and full 180° refocussing pulses suppress scalar coupling, leading to long apparent T2 values and highly efficient data collection. Overall, the detection efficiency of PFOB is very similar that of water in tissue.

Anionic Tuning of Zeolite Crystallization

Zeolites are of great industrial relevance as catalysts, adsorbents, and ion-exchangers and typically synthesized under hydrothermal conditions. Rational regulation of their crystallization process...

Development of a method for the Bloch image simulation of biological tissues

PurposeThe purpose of this study is to develop a method for the Bloch image simulation of biological tissues including various chemical components and T2* distribution. MethodsThe nuclear spins in the object material were modeled as a spectral intensity function Sr→ω defined by superposition of Lorentz functions with various central precession frequencies and the half width of 1/(πT2′), where 1/T2′ is a relaxation rate attributable to microscopic field inhomogeneity in a voxel. Four-dimensional numerical phantoms were created to simulate Sr→ω and used for MRI simulations of the phantoms containing water and fat protons. Single slice multiple (16) gradient-echo sequences (ΔTE = 2.2 and 1.384 ms) were used for experiments at 1.5 T and 3 T and MRI simulations to evaluate the validity of the approach. ResultsExperimentally measured image intensities of the multiple gradient-echo imaging sequences were well reproduced by the MRI simulations. The correlation coefficients between the experimentally measured image intensities and those numerically simulated were 0.9895 to 0.9992 for the 4-component phantom at 1.5 T and 0.9580 to 0.9996 for the 7-component phantom at 3 T. ConclusionT2* and chemical shift effects were successfully implemented in the MRI simulator (BlochSolver). Because this approach can be applied to other MRI simulators, the method developed in this study is useful for MRI simulation of biological tissues containing water and fat protons.

Simultaneous Multiple Resonance Frequency imaging (SMURF): Fat-water imaging using multi-band principles.

PurposeTo develop a fat‐water imaging method that allows reliable separation of the two tissues, uses established robust reconstruction methods, and requires only one single‐echo acquisition.Theory and MethodsThe proposed method uses spectrally selective dual‐band excitation in combination with CAIPIRINHA to generate separate images of fat and water simultaneously. Spatially selective excitation without cross‐contamination is made possible by the use of spatial‐spectral pulses. Fat and water images can either be visualized separately, or the fat images can be corrected for chemical shift displacement and, in gradient echo imaging, for chemical shift‐related phase discrepancy, and recombined with water images, generating fat‐water images free of chemical shift effects. Gradient echo and turbo spin echo sequences were developed based on this Simultaneous Multiple Resonance Frequency imaging (SMURF) approach and their performance was assessed at 3Tesla in imaging of the knee, breasts, and abdomen.ResultsThe proposed method generated well‐separated fat and water images with minimal unaliasing artefacts or cross‐excitation, evidenced by the near absence of water signal attributed to the fat image and vice versa. The separation achieved was similar to or better than that using separate acquisitions with water‐ and fat‐saturation or Dixon methods. The recombined fat‐water images provided similar image contrast to conventional images, but the chemical shift effects were eliminated.ConclusionSimultaneous Multiple Resonance Frequency imaging is a robust fat‐water imaging technique that offers a solution to imaging of body regions with significant amounts of fat.

Structure or Exchange? On the Feasibility of Chemical Exchange Detection with Balanced Steady-State Free Precession in Tissue - An In Vitro Study.

Balanced steady-state free precession imaging has recently been suggested for chemical exchange detection (bSSFPX). The objective of this work is to investigate the contributions of microstructural, chemical shift and chemical exchange effects to the asymmetry of the bSSFP profile at field strengths of 3 T and 9.4 T. To this end, in vitro bSSFPX experiments are performed for a range of repetition times and flip angles in glucose water solutions with different MnCl2 concentrations and tissue homogenates obtained from the brainstem of pig brains. The experimental results are compared to multi-pool Bloch-McConnell simulations. Additionally, the influence of white matter tract geometry is analyzed ex vivo in pig brain hemispheres measured at two different angles with respect to B0 . The detectable bSSFP profile asymmetry in glucose solutions with tissue-like relaxation times and white matter homogenates was consistent with Bloch-McConnell simulations but relatively small. In intact white matter tracts, the asymmetry was dominated by structural effects with a strong dependency on tract orientation relative to B0 . In tracts perpendicular to B0 , the asymmetry was ≈ 3-4 times higher than in the homogenates, thus barely affected by chemical exchange effects. In conclusion, chemical exchange-related bSSFP profile asymmetries are detectable in tissue homogenates, however, the observed asymmetry level is generally low and prone to confounding structural effects rendering in vivo chemical exchange detection with bSSFP challenging in the brain.

A Comparative Study of High-Resolution Chemical-Shift-Eliminated Magnetic Resonance Imaging of Finger Specimens with Microcomputed Tomography.

Objective:High-resolution images of finger joints with chemical-shift elimination can be obtained using an interleaved water-fat (IWF) sequence. This study assessed IWF imaging of finger joints in the delineation of bone structures by comparing images of cadaver fingers with those of microcomputed tomography (CT) that served as a standard reference.Materials and Methods:IWF images with spatial resolution of 176 µ × 176 µ × 300 µ were obtained from the distal and proximal interphalangeal joints of two cadaver finger specimens using a custom-built radiofrequency receive coil at 1.5T. Regular three-dimensional gradient-echo (GRE) images were also acquired with similar parameters and compared with the IWF images to evaluate the effects of chemical shift. Micro-CT scans were obtained and served as the standard reference. The image data were reviewed by two experienced musculoskeletal radiologists in consensus. The delineation of normal joint structures and abnormalities in the finger specimens as revealed by the magnetic resonance imaging (MRI) and micro-CT images were compared. The IWF and regular GRE images were assigned scores 0–3 for the depiction of apparent marginal bone defects, with zero being the same in appearance to the micro-CT image and three as having minimal resemblance to it. Statistical analysis of the scoring results was conducted to compare the two MRI techniques.Results:The high-resolution IWF images provided accurate delineation of bone and calcified structures as seen in micro-CT. The thickness of subchondral bone was depicted similarly on the IWF water + fat and the micro-CT images but not on the regular GRE images. The regular GRE sequence showed false marginal bone defects not observed with IWF and micro-CT. In addition, the IWF water-only images facilitated the identification of bone cyst by revealing its water content.Conclusion:High-resolution IWF imaging should be useful for the early diagnosis and treatment assessment of arthritis and should also benefit basic research in the pathophysiology of the disease.

Probing the Interactions and Dynamics in an Ionic Liquid – Organic Solvent Hybrid Electrolyte System for Potential Application in Li-S Batteries

The depletion of fossil fuel and strict environmental regulation on carbon footprints has prompted a greater reliability on sustainable energy sources. Batteries represent an important energy storage option due to their wide range of applicability and portability, however, for certain applications such as transportation, a higher energy density battery is required. Beyond the conventional Li-ion battery system, current research is focusing on next-generation cost effective devices. Amongst them, the Li-S battery technology is very promising due to its high theoretical capacity and energy density [1]. However, the chemistry involved in the Li-S battery is a complex process with multiple consecutive electrochemical reactions. Despite having many advantages, its application is still limited by several issues, e.g., the dissolution and diffusion of intermediate polysulphides, unstable plating and stripping of Li metal, both resulting in rapid capacity fading [2]. Previously, we reported the application of a novel electrolyte system composed of N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide, C3mpyrFSI, ionic liquid (IL) and 1,2 dimethoxyethane (DME) in the presence of varying saturated lithium bis(fluorosulfonyl)imide, LiFSI which predominantly suppressed the polysulphide dissolution and diffusion while showing improved lithium plating and stripping behavior [3]. In order to expand our understanding on the role of DME and the lithium salt concentration; in this work, we have considered a similar ionic liquid based electrolyte system but at a constant concentration of LiFSI salt. The ionic interactions among different species of the electrolyte system have been extensively studied by nuclear magnetic resonance (NMR) spectroscopy using 1D chemical shift, PFG-NMR and Heteronuclear Overhauser Effect SpectroscopY (HOESY) measurements. We found that, when increasing the DME concentration in the system, a strong association of Li+ cation with the DME occurs due to the electronegative oxygen atoms present in the DME molecules which leads to strong coordination. This leads to a change of the chemical shift of 7Li nuclei due to them being increasingly de-shielded. Interestingly, we found that the diffusivity of both Li+ and DME species are very similar, which also confirms that a Li-DME complex is present with FSI anion associated in the next coordination sphere to counterbalance the positively charged Li complex. MD simulations are underway to better elucidate the molecular shell structure of the system. We have also carried out electrochemical characterizations of these hybrid electrolytes to determine their potential applicability in a lithium sulphur battery. It was apparent using cyclic voltammogram (CV) performed in a three electrode set-up, that an increasing amount of DME increases the ionic conductivity but decreases the lithium plating-stripping efficiency. A coin-cell study of Li/Li symmetrical cycling showed an excellent plating-stripping behaviour for 70%IL-30%DME composition. We have carried out a full cell cycling against sulphur cathode and the optimised electrolyte composition obtained a promising first discharge capacity of 1100mAh/g. Additionally, we have investigated the sulphur speciation in the presence of this ionic liquid in a three-electrode system where platinum mesh has been used as working electrode coupled with in-situ UV-vis spectroscopy. Finally, a time dependent bulk electrolysis study revealed the plausible intermediates formed during the charge-discharge cycle of sulphur redox reaction. From these studies it appears that the composition of this novel hybrid electrolyte system can be tuned to provide a system with improved transport, electrochemical and sulphur speciation properties which lend themselves to a higher performance, next generation lithium sulphur battery technology.

A Simulation Study on the Fat Caused Chemical Shift Effects on the Magnetic Susceptibility Measurement of IONPs With Ultra-Short TEs

To study how the fat affects the quantification of magnetic susceptibility of iron oxide nanoparticles (IONPs) according to the chemical shift effects, especially at ultra-short echo times, simulation experiments were carried out in this paper. Numerical phantom of IONPs solutions with six different concentrations was designed. Magnetic resonance imaging signals with different fat fractions (ffs) were generated according to a multi-peak chemical shift model. Quantitative susceptibility mapping (QSM) was calculated, and the relationship between the QSM value and ff, as well as echo selection, is evaluated. The results show that streaking artifacts become more and more severe when ff increases, which makes QSM value overestimated. Shortened echo spacing time can reduce streaking artifacts with the same ff. These findings will benefit future clinical evaluations for quantification of iron in vivo.

Accelerating multi-slice spatiotemporally encoded MRI with simultaneous echo refocusing

Single-shot spatiotemporally encoded (SPEN) ultrafast magnetic resonance imaging (MRI) is of great value to both scientific research and clinical application owing to its capability for delivering MR images with greater robustness to magnetic field inhomogeneity and chemical-shift displacement effects than conventional methods like EPI due to high effective phase-encoded bandwidth. Many SPEN MRI methods have been developed, among which multi-slice SPEN MRI arises as a promising supplement to ultrafast multi-slice sampling. In this work, we propose a new multi-slice SPEN MRI method, termed multi-echo segmented SPEN (ME-SeSPEN) method, which produces multiple images within a single train of echoes and successively samples widely separated slices. The resulting images were reconstructed using de-convolution super-resolved algorithm. The robustness and efficiency of the proposed method were demonstrated by phantom, lemon and in vivo experiments in comparison with spin-echo EPI, spin-echo simultaneous echo refocusing (SER), and segmented SPEN (SeSPEN) MRI. The results indicate that the new method effectively shortens the sampling time (20% reduction practically in comparison with SeSPEN when two slices are simultaneously sampled). ME-SeSPEN also reduces eddy current effects while maintaining the benefits of SPEN MRI, such as similar robustness to field inhomogeneity, spatial resolution and signal-to-noise ratio to SeSPEN MRI. The new method will promote the versatility of multi-slice MRI in practical applications.

Synthesis and characteristics of sugar-phosphoramidates: A spectroscopic study

Phosphoramidate-incorporated scaffolds are structurally important targets owing to their diverse applications, particularly in medicinal chemistry. Herein we report the synthesis of several sugar phosphoramidates in excellent yields. NMR analyses were undertaken to examine their intramolecular H-bonding, stability under acidic conditions, and chemical shift effects.