Magnetic Susceptibility Differences Research Articles

Different iron distribution patterns in Parkinson's disease and its motor subtypes: a quantitative susceptibility mapping study.

This study utilized quantitative susceptibility mapping (QSM) to evaluate magnetic susceptibility of brain nuclei in Parkinson's disease (PD). To explore iron deposition patterns in PD and ascertain if these patterns can distinguish between motor subtypes. This study enrolled 30 healthy controls and 34 patients with PD categorized mainly into postural instability and gait disorder (PIGD) (n = 12) and tremor dominance (TD) (n = 16). A total of 18 regions of interest were delineated, and a comprehensive classification of nuclei was conducted, including the differentiation of globus pallidus (GP) into its external (GPe) and internal (GPi) segments. All participants underwent brain magnetic resonance imaging. Notable differences in magnetic susceptibility were identified in bilateral substantia nigra pars reticulate (SNr) and substantia nigra pars compacta (SNc) between PD and HC. Significant differences in QSM values of bilateral GPe, SNr, and SNc-R were found between TD and PIGD. The susceptibility values of bilateral putamen (PUT) were positively correlated with MDS-UPDRSIII score and Hoehn-Yahr scale in PD. QSM values of bilateral PUT and SNc-L showed associations with MDS-UPDRSIII score in TD. QSM values showed associations with MDS-UPDRSIII in bilateral PUT and Hoehn-Yahr scale in PUT-L and TH-L in PIGD. Pathologic iron deposition exhibits variability across nuclei of PD, with age also influencing this distribution. SN may be meaningful in identifying different subtypes of PD, such as differentiating PD from HC in the future.

Histology-guided MRI segmentation of brainstem nuclei critical to consciousness.

While substantial progress has been made in mapping the connectivity of cortical networks responsible for conscious awareness, neuroimaging analysis of subcortical arousal networks that modulate arousal (i.e., wakefulness) has been limited by a lack of a robust segmentation procedures for brainstem arousal nuclei. Automated segmentation of brainstem arousal nuclei is an essential step toward elucidating the physiology of arousal in human consciousness and the pathophysiology of disorders of consciousness. We created a probabilistic atlas of brainstem arousal nuclei built on diffusion MRI scans of five ex vivo human brain specimens scanned at 750 μm isotropic resolution. Labels of arousal nuclei used to generate the probabilistic atlas were manually annotated with reference to nucleus-specific immunostaining in two of the five brain specimens. We then developed a Bayesian segmentation algorithm that utilizes the probabilistic atlas as a generative model and automatically identifies brainstem arousal nuclei in a resolution- and contrast-agnostic manner. The segmentation method displayed high accuracy in both healthy and lesioned in vivo T1 MRI scans and high test-retest reliability across both T1 and T2 MRI contrasts. Finally, we show that the segmentation algorithm can detect volumetric changes and differences in magnetic susceptibility within brainstem arousal nuclei in Alzheimer's disease and traumatic coma, respectively. We release the probabilistic atlas and Bayesian segmentation tool in FreeSurfer to advance the study of human consciousness and its disorders.

Topographical metal burden correlates with brain atrophy and clinical severity in Wilson's disease

BackgroundQuantitative susceptibility mapping (QSM) is a post-processing technique that creates brain susceptibility maps reflecting metal burden through tissue magnetic susceptibility. We assessed topographic differences in magnetic susceptibility between participants with and without Wilson's disease (WD), correlating these findings with clinical severity, brain volume, and biofluid copper and iron indices. MethodsA total of 43 patients with WD and 20 unaffected controls, were recruited. QSM images were derived from a 3T MRI scanner. Clinical severity was defined using the minimal Unified Wilson's Disease Rating Scale (M-UWDRS) and Montreal Cognitive Assessment scoring. Differences in magnetic susceptibilities between groups were evaluated using general linear regression models, adjusting for age and sex. Correlations between the susceptibilities and clinical scores were analyzed using Spearman's method. ResultsIn age- and sex-adjusted analyses, magnetic susceptibility values were increased in WD patients compared with controls, including caudate nucleus, putamen, globus pallidus, and substantia nigra (all p < 0.01). Putaminal susceptibility was greater with an initial neuropsychiatric presentation (n = 25) than with initial hepatic dysfunction (n = 18; p = 0.04). Susceptibility changes correlated negatively with regional brain volume in almost all topographic regions. Serum ferritin, but not serum copper or ceruloplasmin, correlated positively with magnetic susceptibility level in the caudate nucleus (p = 0.04), putamen (p = 0.04) and the hippocampus (p = 0.03). The dominance of magnetic susceptibility in cortical over subcortical regions correlated with M-UWDRS scores (p < 0.01). ConclusionThe magnetic susceptibility changes could serve as a surrogate marker for patients with WD.

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.

Whole brain pattern of iron accumulation in REM sleep behavior disorder.

Isolated REM sleep behavior disorder (iRBD) is an early stage of synucleinopathy with most patients progressing to Parkinson's disease (PD) or related conditions. Quantitative susceptibility mapping (QSM) in PD has identified pathological iron accumulation in the substantia nigra (SN) and variably also in basal ganglia and cortex. Analyzing whole-brain QSM across iRBD, PD, and healthy controls (HC) may help to ascertain the extent of neurodegeneration in prodromal synucleinopathy. 70 de novo PD patients, 70 iRBD patients, and 60 HCs underwent 3 T MRI. T1 and susceptibility-weighted images were acquired and processed to space standardized QSM. Voxel-based analyses of grey matter magnetic susceptibility differences comparing all groups were performed on the whole brain and upper brainstem levels with the statistical threshold set at family-wise error-corrected p-values <.05. Whole-brain analysis showed increased susceptibility in the bilateral fronto-parietal cortex of iRBD patients compared to both PD and HC. This was not associated with cortical thinning according to the cortical thickness analysis. Compared to iRBD, PD patients had increased susceptibility in the left amygdala and hippocampal region. Upper brainstem analysis revealed increased susceptibility within the bilateral SN for both PD and iRBD compared to HC; changes were located predominantly in nigrosome 1 in the former and nigrosome 2 in the latter group. In the iRBD group, abnormal dopamine transporter SPECT was associated with increased susceptibility in nigrosome 1. iRBD patients display greater fronto-parietal cortex involvement than incidental early-stage PD cohort indicating more widespread subclinical neuropathology. Dopaminergic degeneration in the substantia nigra is paralleled by susceptibility increase, mainly in nigrosome 1.

Study on magnetic properties of two dysprosium(III)-substituted antimonotungstates with different substitution modes

Two Polyoxometalates have been constructed by simple hydrothermal synthesis using rare-earth (RE) and antimonotungstates (ATs) {B-α-SbW9O33} as raw materials with the molecular formulas of H4.5Na1.5(H2O)6(C3H5N2)3{Na(Sb3O)2[B-β-SbW8O31Dy(H2O)2]3}·12H2O (1) and H9(C3H5N2)5{[Sb6IIISbVDy2WO10(H2O)5][(B-β-SbW9O33)2(B-α-SbW9O33)]}·16H2O (2). X-ray Single crystal diffractometer analysis shows that both 1 and 2 possess trimer configurations. Polyoxoanion 1 is assembled from three trilacunary {B-β-SbW8O31Dy(H2O)2}p units linked via {Na(Sb3O)2} cluster, where the trilacunary {B-β-SbW8O31Dy(H2O)2} unit is formed by the tetralacunary {B-β-SbW8O31} unit captures one Dy(H2O)23+ cation. Polyoxoanion 2 is composed of a novel 5p−4f heterometallic cluster {Sb6IIISbVDy2WO12(H2O)5} simultaneously stabilized by two {B-β-SbW9O33} units and one {B-α-SbW9O33} unit. In addition, two-dimensional correlation infrared spectroscopy (2D COS-IR) under magnetic disturbance was measured to investigate the difference of the variable temperature magnetic susceptibility between two compounds to explore the source of magnetic properties, and further magnetic property tests indicate that 1 and 2 may exhibit single-molecule-magnet behavior with distinct frequency dependence. This work deepens the theory of 2D COS-IR and also enriches the theoretical and experimental data of magnetism.

Towards clinical translation of 7 Tesla MRI in the human brain

Clinical translation of 7 tesla (T) MRI of the brain promises high image quality and potentially improved clinical diagnosis for patients compared to current standard lower field-strength MRI at 1.5 and 3T.Here we describe how physics principles underlying ultra-high field (UHF) strength MRI affect 7T image quality, and how these can be exploited to translate 7T brain imaging into clinical practice. UHF MRI profits from higher inherent signal-to-noise ratio (SNR) and a resultant increase in achievable spatial resolution or acceleration factors; increase in sensitivity to magnetic susceptibility differences and a higher amplitude of the Blood Oxygen Level Dependent (BOLD) signal; increase in longitudinal relaxation time; and increased frequency dispersion and spectral resolution in MR spectroscopy.Examples are presented of different brain pathologies, which are better illustrated on 7T compared to lower field strength by applying sequences and imaging techniques that exploit these intrinsic strengths of 7T MRI. This includes imaging of various vascular pathologies, epilepsy and brain tumours.

Advancements in MR hardware systems and magnetic field control: B0 shimming, RF coils, and gradient techniques for enhancing magnetic resonance imaging and spectroscopy.

High magnetic field homogeneity is critical for magnetic resonance imaging (MRI), functional MRI, and magnetic resonance spectroscopy (MRS) applications. B0 inhomogeneity during MR scans is a long-standing problem resulting from magnet imperfections and site conditions, with the main issue being the inhomogeneity across the human body caused by differences in magnetic susceptibilities between tissues, resulting in signal loss, image distortion, and poor spectral resolution. Through a combination of passive and active shim techniques, as well as technological advances employing multi-coil techniques, optimal coil design, motion tracking, and real-time modifications, improved field homogeneity and image quality have been achieved in MRI/MRS. The integration of RF and shim coils brings a high shim efficiency due to the proximity of participants. This technique will potentially be applied to high-density RF coils with a high-density shim array for improved B0 homogeneity. Simultaneous shimming and image encoding can be achieved using multi-coil array, which also enables the development of novel encoding methods using advanced magnetic field control. Field monitoring enables the capture and real-time compensation for dynamic field perturbance beyond the static background inhomogeneity. These advancements have the potential to better use the scanner performance to enhance diagnostic capabilities and broaden applications of MRI/MRS in a variety of clinical and research settings. The purpose of this paper is to provide an overview of the latest advances in B0 magnetic field shimming and magnetic field control techniques as well as MR hardware, and to emphasize their significance and potential impact on improving the data quality of MRI/MRS.

Non-invasive assessment and visualization of Phytophthora cactorum infection in strawberry crowns using quantitative magnetic resonance imaging

Phytophthora cactorum is an oomycete species that causes enormous losses on horticultural crops, including strawberries. The purpose of this work was to investigate the alterations caused by P. cactorum inoculation in hydroponically grown strawberry plantlets (Fragaria × ananassa Duch.) using quantitative magnetic resonance imaging (qMRI). It was observed that with MRI, spatial and temporal progression of the infection could be observed in the crown using quantitative MR parameters, namely relaxation time maps. Relaxation times are numeric subject-specific properties that describe the MR signal behavior in an examined anatomical region. Elevated T2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{2}$$\\end{document} relaxation time values were observed inside the infected plant crowns with respect to the healthy references. The T2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{2}$$\\end{document} and T2∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{2}^{*}$$\\end{document} values of healthy plants were small in the crown region and further diminished during the development of the plant. Furthermore, elevated T1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{1}$$\\end{document} relaxation time values were seen in regions where P. cactorum progression was observed in corresponding plant dissection photographs. Quantitative susceptibility maps (QSM) were calculated to estimate the local magnetic field inhomogeneities. The QSM suggests magnetic susceptibility differences near the center of the pith. This study provides novel non-invasive information on the structure and development of strawberry plants and the effects caused by the P. cactorum infection.

Innovative technology for preparation of high-purity silica from vein quartz ore through S-HGMS coupling acid leaching process

In the present work, an S-HGMS coupling acid leaching technology was established to prepare high-purity silica using vein quartz ore. Firstly, the magnetic properties of different phases in vein quartz were investigated through density functional theory (DFT) calculations and arranged the phases in terms of magnetic susceptibility: FeP2 > Al2SiO5 > SiO2 > Ca(Al2Si2)O8 > AlPO4. Those differences in magnetic susceptibility resulted from the spin state of electrons in the ions. After treatment using the S-HGMS process, weakly magnetic particles are effectively separated from silica particles, and the obtained silica concentrate contained SiO2 of 99.690% purity. Subsequently, lattice impurity ions were removed through a fluorine-free and low-fluoric acid leaching process. Under optimal conditions, the SiO2 purity in high-purity silica reached 99.954% and 99.990% in the two processes. The lattice parameters and volume of ɑ-quartz in high-purity silica obtained with low-fluoric acid leaching were less than those obtained with fluorine-free acid leaching. This difference can be attributed to the reaction between HF molecules and lattice impurity ions, resulting in the generation of coordination compounds. Meanwhile, HF dissolved SiO2 and opened the lattice impurity ions channel, promoting lattice impurity ions depth removal. This study established a complete set of critical technologies for preparing high-purity silica from vein quartz through the S-HGMS coupling acid leaching process, providing theoretical and scientific bases for industrial applications.

Quantitative susceptibility mapping shows lower brain iron content in children with childhood epilepsy with centrotemporal spikes.

The dysregulation of brain iron homeostasis is closely relevant to a multitude of chronic neurological disorders. This study employed quantitative susceptibility mapping (QSM) to detect and compare whole-brain iron content between childhood epilepsy with centrotemporal spikes (CECTS) children and typically developing children. 32 children with CECTS and 25 age- and gender-matched healthy children were enrolled. All participants were imaged with 3.0-T MRI to acquire the structural and susceptibility-weighted data. The susceptibility-weighted data were processed using STISuite toolbox to obtain QSM. The magnetic susceptibility difference between the two groups was compared using voxel-wise and region of interest methods. Multivariable linear regression, controlling for age, were employed to investigate the associations between the brain magnetic susceptibility and age at onset. Lower magnetic susceptibility was mainly observed in sensory- and motor-related brain regions in children with CECTS, including bilateral middle frontal gyrus, supplementary motor area, midcingulate cortex, paracentral lobule and precentral gyrus, the magnetic susceptibility of right paracentral lobule, right precuneus and left supplementary motor area were found to have positive correlation with the age at onset. This study suggests that the potential iron deficiency in certain brain regions is associated with CECTS, which might be helpful for further illumination of potential pathogenesis mechanism of CECTS.

A potential NMR-based wettability index using free induction decay for rocks

The wettability of reservoir rocks saturated with oil and water is one of the most important factors influencing petrophysics and oil recovery. Minerals with different wettability constitute the overall heterogeneous wettability in rocks. Variations in sample composition can be detected by nuclear magnetic resonance (NMR) measurements. In this paper, the method of using the magnetic susceptibility contrast between rock skeleton and saturated fluid to estimate wettability is proposed. The theoretical feasibility was firstly analyzed, and then the internal gradients caused by magnetic susceptibility contrasts were employed to interpret wettability alteration before and after ageing process in rocks. It was discovered that water and oil in the same pores experienced different internal gradients after ageing, which were associated with the differences in magnetic susceptibility contrasts. After that, the free induction decay measurement was performed to acquire magnetic susceptibility contrasts of artificial sandstone samples with the intermediate-wet condition. A refined NMR wettability index was presented and correlated with the Amott wettability tests. The experimental results demonstrate that the new method for determining wettability is feasible.

Quantitative Blood Oxygenation Level Dependent Magnetic Resonance Imaging for Estimating Intra-renal Oxygen Availability Demonstrates Kidneys Are Hypoxemic in Human CKD

Kidney blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI) has shown great promise in evaluating relative oxygen availability. This method is quite efficacious in evaluating acute responses to physiological and pharmacologic maneuvers. Its outcome parameter, R2∗ is defined as the apparent spin-spin relaxation rate measured in the presence of magnetic susceptibility differences and it is measured using gradient echo MRI. Although associations between R2∗ and renal function decline have been described, it remains uncertain to what extent R2∗ is a true reflection of tissue oxygenation. This is primarily because of not taking into account the confounding factors, especially fractional blood volume (fBV) in tissue. This case-control study included 7 healthy controls and 6 patients with diabetes and chronic kidney disease (CKD). Using data before and after administration of ferumoxytol, a blood pool MRI contrast media, the fBVs in kidney cortex and medulla were measured. This pilot study independently measured fBV in kidney cortex (0.23 ± 0.03 vs. 0.17 ± 0.03) and medulla (0.36 ± 0.08 vs. 0.25 ± 0.03) in a small number of healthy controls (n= 7) versus CKD (n= 6). These were then combined with BOLD MRI measurements to estimate oxygen saturation of hemoglobin (StO2) (0.87 ± 0.03 vs. 0.72 ± 0.10 in cortex; 0.82 ± 0.05 vs. 0.72 ± 0.06 in medulla) and partial pressure of oxygen in blood (bloodPO2) (55.4 ± 6.5 vs. 38.4 ± 7.6 mmHg in cortex; 48.4 ± 6.2 vs. 38.1 ± 4.5 mmHg in medulla) in control versus CKD. The results for the first time demonstrate that cortex is normoxemic in controls and moderately hypoxemic in CKD. In the medulla, it is mildly hypoxemic in controls and moderately hypoxemic in CKD. Whereas fBV, StO2, and bloodPO2 were strongly associated with estimated glomerular filtration rate (eGFR), R2∗ was not. Our results support the feasibility of quantitatively assessing oxygen availability using noninvasive quantitative BOLD MRI that could be translated to the clinic.

GEOPHYSICAL INVESTIGATION OF IWO AND ILESHA, OSUN STATE USING HIGH RESOLUTION AEROMAGNETIC DATA

The study deals with the Geophysical investigation of Iwo and Ilesha, Osun State, using aeromagnetic data. Qualitative as well as quantitative interpretation of the aeromagnetic data were carried out to obtain more information about the thickness of sedimentary basins. Two methods were used in the interpretation; there are Euler deconvolution method and source parameter imaging (SPI). Oasis Montaj software was employed in the analysis, the Magnetic intensity ranges from a minimum value of -22.7 nT to a maximum value of 110.4 nT, this indicate that the area is characterised with low and high magnetic signature and could be as a result of difference in magnetic susceptibility, depth and the nature of the magnetic anomalous bodies present. The depth for magnetic source ranges from 187.6 to 1005.5 m using parameter imaging (SPI).Using Euler deconvolution method, the depth estimation for structural index (SI = 0.5, 1.0, 1.5) ranges from 300 m to 25481m, 262.9m to 1826.2m and 391.0m to 3243.6m respectively. The results obtained indicate shallow depths to magnetic anomalies which may not be suitable for hydrocarbon accumulation.

Detection of brown adipose tissue in rats with acute cold stimulation using quantitative susceptibility mapping.

Detection of brown adipose tissue in rats with acute cold stimulation using quantitative susceptibility mapping.

Quantitative analysis of diffusion regimes in iron ore with low field NMR

SUMMARY The use of nuclear magnetic resonance (NMR) techniques allows in situ characterization of geophysical properties such as moisture content, permeability and wettability. However, the accuracy and applicability of such measurements is limited by internal magnetic field gradients which are a consequence of magnetic susceptibility differences at solid–fluid interfaces. Such effects are particularly prominent in iron ore rock samples which contain ferrimagnetic and ferromagnetic mineralogy leading to high magnetic susceptibility. Multiple echo time Carr–Purcell–Meiboom–Gill (CPMG) NMR pulse sequences are commonly used to capture the influence of internal gradients, with the intention of deconvoluting diffusion in effective internal gradients (geff) from true transver relaxation (T2). The interpretation of such measurements is complicated by the presence of multiple diffusive regimes: the short-time (ST), motionally averaged and localization regimes respectively. We introduce a new model for diffusive NMR signal attenuation, called the multiregime model which is intended to better capture diffusive behaviour across the three regimes. The multiregime model is compared against previous methods for quantifying diffusive decay (the ST only and generalized inversion models). Multi-echo measurements of iron ore samples are fit with each model in order to quantify 2-D T2–geff distributions. The resulting distributions demonstrate how the multiregime model can provide insight into the relative influence of the different diffusive regimes in a given sample. This assists in understanding the influence of diffusive decay on measurement accuracy, for example the increased measurement error with increasing prevalence of the localization regime. The multiregime model provides a key step in accurately segregating surface relaxation and diffusive relaxation, which is crucial for accurately estimating pore size distributions, permeability and wettability in high magnetic susceptibility samples using NMR.

Slice-direction geometric distortion evaluation and correction with reversed slice-select gradient acquisitions

Accurate spatial alignment of MRI data acquired across multiple contrasts in the same subject is often crucial for data analysis and interpretation, but can be challenging in the presence of geometric distortions that differ between acquisitions. It is well known that single-shot echo-planar imaging (EPI) acquisitions suffer from distortion in the phase-encoding direction due to B0 field inhomogeneities arising from tissue magnetic susceptibility differences and other sources, however there can be distortion in other encoding directions as well in the presence of strong field inhomogeneities. High-resolution ultrahigh-field MRI typically uses low bandwidth in the slice-encoding direction to acquire thin slices and, when combined with the pronounced B0 inhomogeneities, is prone to an additional geometric distortion in the slice direction as well. Here we demonstrate the presence of this slice distortion in high-resolution 7T EPI acquired with a novel pulse sequence allowing for the reversal of the slice-encoding gradient polarity that enables the acquisition of pairs of images with equal magnitudes of distortion in the slice direction but with opposing polarities. We also show that the slice-direction distortion can be corrected using gradient reversal-based method applying the same software used for conventional corrections of phase-encoding direction distortion.

Magnetic properties of chalcopyrite and arsenopyrite for high-gradient magnetic separation with Crystal-Field Theory

Separating chalcopyrite from arsenopyrite using flotation has been a big challenge due to their similar floatability. However, this challenging condition may be partially solved by employing their difference in magnetic susceptibility. As a matter of fact, pulsating high-gradient magnetic separation (PHGMS), as an environment-friendly and economic strategy, was recently attempted to remove arsenopyrite from chalcopyrite with considerable performance. In this study, the magnetic difference of chalcopyrite and arsenopyrite was confirmed using the Density Functional Theory (DFT) calculation and the Vibrating Sample Magnetometer (VSM) measurement. The results indicated that the two minerals possess significant magnetic property difference, and the chalcopyrite has a much larger magnetic susceptibility than that of arsenopyrite. The theoretical analysis based on the Crystal-Field Theory revealed that the difference was resulted from their spin state of d electrons in Fe ions. This has been further demonstrated by the separation performance of a cyclic PHGMS separator in separating a pure chlacopyrite-arsenopyrite mixture, which assays 15.69% Cu and 22.66% As. Under the optimized conditions, the separator produced a chalcopyrite concentrate assaying 20.25% Cu and 9.92% As, with 79.07% Cu and 26.82% As recovered respectively; in the non-magnetic product, the Cu grade was reduced to 8.48% and the As grade was improved to 42.83%. This investigation has demonstrated a potential perspective for the environmental-friendly and economic removal of arsenopyrite from chalcopyrite using PHGMS method.

Susceptibility-weighted imaging at high-performance 0.5T magnetic resonance imaging system: Protocol considerations and experimental results.

The high-performance low-field magnetic resonance imaging (MRI) system, equipped with modern hardware and contemporary imaging capabilities, has garnered interest within the MRI community in recent years. It has also been proven to have unique advantages over high-field MRI in both physical and cost aspects. However, for susceptibility weighted imaging (SWI), the low signal-to-noise ratio and the long echo time inherent at low field hinder the SWI from being applied to clinical applications. This work optimized the imaging protocol to select suitable parameters such as the values of time of echo (TE), repetition time (TR), and the flip angle (FA) of the RF pulse according to the signal simulations for low-field SWI. To improve the signal-to-noise ratio (SNR) performance, averaging multi-echo magnitude images and BM4D phase denoising were proposed. A comparison of the SWI in 0.5T and 1.5T was carried out, demonstrating the capability to identify magnetic susceptibility differences between variable tissues, especially, the blood veins. This would open the possibility to extend SWI applications in the high-performance low field MRI.

Body MRI: Imaging Protocols, Techniques, and Lessons Learned.

Body MRI has evolved from a niche subspecialty to a standard modality in the practice of abdominal radiology. However, the practicing radiologist may feel uncomfortable interpreting body MRI studies owing to a lack of case volume and inconsistent exposure. The authors highlight teaching points and subtleties central to better acquisition and interpretation of body MRI studies. Appropriate contrast agent selection and arterial phase acquisition timing provide greater diagnostic certainty in answering common clinical questions at liver MRI, such as assessing cirrhosis and evaluating focal liver lesions. Clinically relevant artifacts and physiologic phenomena, such as magnetic susceptibility and transient hepatic intensity difference, must be recognized and appropriately used when reading a study. Fat within organs and lesions is commonly encountered at body MRI. The authors discuss the nuances of common and uncommon entities, how to address fat suppression failure, assessment of bone marrow at body MRI, and an organized approach to fat-containing renal and adrenal masses. Motion artifacts are more commonly encountered at body MRI than at MRI of other anatomic regions, and understanding the various techniques, their benefits, and trade-offs will aid the body imager in protocol design and moving beyond "nondiagnostic" examinations. Challenging anatomic sites to evaluate at body MRI are reviewed. Finally, the authors offer tips for accurate interpretation of diffusion-weighted imaging, hepatobiliary phase imaging, and posttreatment imaging studies. By reviewing this article, the abdominal imager will be better prepared to perform and interpret body MRI studies confidently and accurately. An invited commentary by Kalb is available online. Online supplemental material is available for this article. ©RSNA, 2022.