SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Spin echo

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BACKGROUND: The treatment planning of spine pathologies requires information on the rigidity and permeability of the intervertebral discs (IVDs). Magnetic resonance imaging (MRI) offers great potential as a sensitive and non-invasive technique for describing the mechanical properties of IVDs. However, the literature reported small correlation coefficients between mechanical properties and MRI parameters. Our hypothesis is that the compressive modulus and the permeability of the IVD can be predicted by a linear combination of MRI parameters. METHODS: Sixty IVDs were harvested from bovine tails, and randomly separated in four groups (in-situ, digested-6h, digested-18h, digested-24h). Multi-parametric MRI acquisitions were used to quantify the relaxation times T1 and T2, the magnetization transfer ratio MTR, the apparent diffusion coefficient ADC and the fractional anisotropy FA. Unconfined compression, confined compression and direct permeability measurements were performed to quantify the compressive moduli and the hydraulic permeabilities. Differences between groups were evaluated from a one way ANOVA. Multi linear regressions were performed between dependent mechanical properties and independent MRI parameters to verify our hypothesis. A principal component analysis was used to convert the set of possibly correlated variables into a set of linearly uncorrelated variables. Agglomerative Hierarchical Clustering was performed on the 3 principal components. RESULTS: Multilinear regressions showed that 45 to 80% of the Young’s modulus E, the aggregate modulus in absence of deformation HA0, the radial permeability kr and the axial permeability in absence of deformation k0 can be explained by the MRI parameters within both the nucleus pulposus and the annulus pulposus. The principal component analysis reduced our variables to two principal components with a cumulative variability of 52-65%, which increased to 70-82% when considering the third principal component. The dendograms showed a natural division into four clusters for the nucleus pulposus and into three or four clusters for the annulus fibrosus. CONCLUSIONS: The compressive moduli and the permeabilities of isolated IVDs can be assessed mostly by MT and diffusion sequences. However, the relationships have to be improved with the inclusion of MRI parameters more sensitive to IVD degeneration. Before the use of this technique to quantify the mechanical properties of IVDs in vivo on patients suffering from various diseases, the relationships have to be defined for each degeneration state of the tissue that mimics the pathology. Our MRI protocol associated to principal component analysis and agglomerative hierarchical clustering are promising tools to classify the degenerated intervertebral discs and further find biomarkers and predictive factors of the evolution of the pathologies.

Concepts: Nuclear magnetic resonance, Magnetic resonance imaging, Principal component analysis, Diffusion MRI, Pearson product-moment correlation coefficient, Spin echo, Young's modulus, Helium

137

Sodium (23Na) MRI proffers the possibility of novel information for neurological research but also particular challenges. Uncertainty can arise in in vivo23Na estimates from signal losses given the rapidity of T2* decay due to biexponential relaxation with both short (T2*short) and long (T2*long) components. We build on previous work by characterising the decay curve directly via multi-echo imaging at 7 T in 13 controls with the requisite number, distribution and range to assess the distribution of both in vivo T2*shortand T2*longand in variation between grey and white matter, and subregions. By modelling the relationship between signal and reference concentration and applying it to in vivo23Na-MRI signal,23Na concentrations and apparent transverse relaxation times of different brain regions were measured for the first time. Relaxation components and concentrations differed substantially between regions of differing tissue composition, suggesting sensitivity of multi-echo23Na-MRI toward features of tissue composition. As such, these results raise the prospect of multi-echo23Na-MRI as an adjunct source of information on biochemical mechanisms in both physiological and pathophysiological states.

Concepts: Central nervous system, Time, Brain, Chemistry, Nuclear magnetic resonance, Magnetic resonance imaging, Spin echo, Relaxation

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AIM OF THE STUDY: The aim of this study was to describe an individual’s 3-dimensional buttocks response to sitting. Within that exploration, we specifically considered tissue (i.e., fat and muscle) deformations, including tissue displacements that have not been identified by research published to date. MATERIALS AND METHODS: The buttocks anatomy of an able-bodied female during sitting was collected in a FONAR Upright MRI. T1-weighted Fast Spin Echo scans were collected with the individual seated on a custom wheelchair cushion with a cutout beneath the pelvis (“unloaded”), and seated on a 3″ foam cushion (“loaded”). 2D slices of the MRI were analyzed, and bone and muscle were segmented to permit 3D rendering and analyses. RESULTS: MRIs indicated a marked decrease in muscle thickness under the ischial tuberosity during loaded sitting. This change in thickness resulted from a combination of muscle displacement and distortion. The gluteus and hamstrings overlapped beneath the pelvis in an unloaded condition, enveloping the ischial tuberosity. But the overlap was removed under load. The hamstrings moved anteriorly, while the gluteus moved posterior-laterally. Under load, neither muscle was directly beneath the apex of the ischial tuberosity. Furthermore, there was a change in muscle shape, particularly posterior to the peak of the ischial tuberosity. CONCLUSION: The complex deformation of buttocks tissue seen in this case study may help explain the inconsistent results reported in finite element models. 3D imaging of the seated buttocks provides a unique opportunity to study the actual buttocks response to sitting.

Concepts: Nuclear magnetic resonance, Magnetic resonance imaging, Pelvis, Spin echo, Thigh, 3D computer graphics, Tuberosity of the ischium, Sacrotuberous ligament

27

Hollow Mn-doped iron oxide nanocontainers, formed by a novel one-pot synthetic process, fulfill the dual requirements of delivering an effective dose of an anticancer drug to tumor tissue and enabling image-contrast monitoring of the nanocontainer fate through T2 -weighted magnetic resonance imaging, thereby determining the optimal balance between diagnostic and therapeutic moieties in an all-in-one theranostic nanoplatform.

Concepts: Pharmacology, Oncology, Spin, Brain tumor, Nuclear magnetic resonance, Magnetic resonance imaging, Spin echo, Magnetite

27

In the 12-month phase 3 TRANSFORMS study, fingolimod showed greater efficacy than intramuscular interferon beta (IFNβ)-1a in patients with relapsing-remitting multiple sclerosis (RRMS). This study analyzed fingolimod efficacy compared with IFNβ-1a in patient subgroups from TRANSFORMS. Patients were randomized to receive fingolimod or weekly IM IFNβ-1a for 12 months. Analyses of efficacy included annualized relapse rate (ARR), and magnetic resonance imaging (MRI) measures [gadolinium (Gd)-enhancing T1 lesions, new/newly enlarged (active) T2 lesions, brain volume change]. Subgroups were defined based on demographics, disease characteristics (baseline EDSS score, relapse rate, and MRI parameters), and response to previous therapy. Fingolimod 0.5 mg reduced ARR over 12 months by 32-59 % relative to IFNβ-1a in all subgroups defined by demographic factors or baseline disease characteristics. Fingolimod also reduced the number of new Gd-enhancing lesions, active T2 lesions, and the rate of brain volume loss, versus IFNβ-1a in most (95 %) subgroups. In patients with high disease activity despite IFNβ treatment in the year before study, fingolimod 0.5 mg reduced ARR by 61 % relative to IFNβ-1a. Reductions in lesion counts and brain volume loss also favored fingolimod in these patients. In conclusion, consistently better efficacy was observed for fingolimod compared with IFNβ-1a across different subgroups of patients with RRMS.

Concepts: Brain, Patient, Brain tumor, Nuclear magnetic resonance, Magnetic resonance imaging, Multiple sclerosis, Spin echo, Interferon beta-1a

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Photothermal therapy (PTT) is a non-invasive and convenient way to ablate tumor tissues. Integrating PTT with imaging technique could precisely identify the location and the size of tumor regions, thereby significantly improving the therapeutic efficacy. Magnetic resonance imaging (MRI) is widely used in clinical diagnosis due to its superb spatial resolution and real-time monitoring feature. In our work, we developed a theranostic nanoplatform based on manganese doped iron oxide (MnIO) nanoparticles modified with denatured bovine serum albumin (MnIO-dBSA). The in vitro experiment revealed that the MnIO nanoparticles exhibited T1-weighted MRI capability (r1 = 8.24 mM-1s-1, r2/r1 = 2.18) and good photothermal effect under near-infrared laser irradiation (808 nm). Using 4T1 tumor-bearing mice as an animal model, we further demonstrated that the MnIO-dBSA composites could significantly increase T1 MRI signal intensity at the tumor site (about two times) and effectively ablate tumor tissues with photoirradiation. Taking together, this work demonstrates the great potential of the MnIO nanoparticles as an ideal theranostic platform for efficient tumor MR imaging and photothermal therapy.

Concepts: Oncology, Medical imaging, Brain tumor, Nuclear magnetic resonance, Therapy, Magnetic resonance imaging, Serum albumin, Spin echo

24

Renal perfusion measurements using noninvasive arterial spin-labeled (ASL) magnetic resonance imaging techniques are gaining interest. Currently, focus has been on perfusion in the context of renal transplant. Our objectives were to explore the use of ASL in patients with renal cancer, and to evaluate three-dimensional (3D) fast spin echo (FSE) acquisition, a robust volumetric imaging method for abdominal applications. We evaluate 3D ASL perfusion magnetic resonance imaging in the kidneys compared to two-dimensional (2D) ASL in patients and healthy subjects.

Concepts: Chronic kidney disease, Kidney, Spin, Medical imaging, Nuclear magnetic resonance, Magnetic resonance imaging, Spin echo, 2D computer graphics

23

Gadolinium-based contrast agents (GBCA), widely used in Magnetic Resonance Imaging (MRI) for almost 30 years, were recently shown to be deposited in the brain and to induce persistent T1 shortening in deep gray matter structures in subjects with normal renal function. The aim of the present study is to summarize the evidence derived from the rapidly growing scientific literature on Gadolinium retention in the brain and in the rest of the body. To this end, the original articles that described imaging and pathology findings in humans and animals exposed to GBCA were reviewed. The main aspects that emerged were the different effects of linear and macrocyclic GBCA on brain MRI appearance, the evidence of Gadolinium tissue retention in multiple organs, and the debated issue of the possible clinical consequences. Although no adverse health effects have been documented so far, updated information about GBCA build-up in the body is necessary for health professionals, also in view of the increasing concern in the general population. To date, our knowledge about the mechanisms of Gadolinium tissue deposition and, above all, its long-term consequences is still largely incomplete. However, while official guidelines are eagerly awaited, some advices may already be given, to help our radiological daily practice.

Concepts: Brain, Medical imaging, Brain tumor, Nuclear magnetic resonance, Magnetic resonance imaging, Radiology, Spin echo, Contrast medium

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Manganese, an essential metal for normal growth and development, is neurotoxic on excessive exposure. Standard trace element-supplemented neonatal parenteral nutrition (PN) has a high manganese content and bypasses normal gastrointestinal absorptive control mechanisms, which places infants at risk of manganese neurotoxicity. Magnetic resonance (MR) relaxometry demonstrating short T1 relaxation time (T1R) in the basal ganglia reflects excessive brain manganese accumulation.

Concepts: Time, Brain, Nuclear magnetic resonance, Magnetic resonance imaging, Basal ganglia, Spin echo, Relaxation, Relaxometry

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Parametric mapping techniques provide a non-invasive tool for quantifying tissue alterations in myocardial disease in those eligible for cardiovascular magnetic resonance (CMR). Parametric mapping with CMR now permits the routine spatial visualization and quantification of changes in myocardial composition based on changes in T1, T2, and T2*(star) relaxation times and extracellular volume (ECV). These changes include specific disease pathways related to mainly intracellular disturbances of the cardiomyocyte (e.g., iron overload, or glycosphingolipid accumulation in Anderson-Fabry disease); extracellular disturbances in the myocardial interstitium (e.g., myocardial fibrosis or cardiac amyloidosis from accumulation of collagen or amyloid proteins, respectively); or both (myocardial edema with increased intracellular and/or extracellular water). Parametric mapping promises improvements in patient care through advances in quantitative diagnostics, inter- and intra-patient comparability, and relatedly improvements in treatment. There is a multitude of technical approaches and potential applications. This document provides a summary of the existing evidence for the clinical value of parametric mapping in the heart as of mid 2017, and gives recommendations for practical use in different clinical scenarios for scientists, clinicians, and CMR manufacturers.

Concepts: Blood, Heart, Cardiac muscle, Nuclear magnetic resonance, Magnetic resonance imaging, Circulatory system, Spin echo, Amyloidosis