Low Mr Research Articles

Visual and Contextual Modeling for the Detection of Repeated Mild Traumatic Brain Injury

Currently, there is a lack of computational methods for the evaluation of mild traumatic brain injury (mTBI) from magnetic resonance imaging (MRI). Further, the development of automated analyses has been hindered by the subtle nature of mTBI abnormalities, which appear as low contrast MR regions. This paper proposes an approach that is able to detect mTBI lesions by combining both the high-level context and low-level visual information. The contextual model estimates the progression of the disease using subject information, such as the time since injury and the knowledge about the location of mTBI. The visual model utilizes texture features in MRI along with a probabilistic support vector machine to maximize the discrimination in unimodal MR images. These two models are fused to obtain a final estimate of the locations of the mTBI lesion. The models are tested using a novel rodent model of repeated mTBI dataset. The experimental results demonstrate that the fusion of both contextual and visual textural features outperforms other state-of-the-art approaches. Clinically, our approach has the potential to benefit both clinicians by speeding diagnosis and patients by improving clinical care.

AB1139 Chronic recurrent ostemomyelitis in three siblings

BackgroundChronic recurrent osteomyelitis(CRMO) is an autoinflammatory disease.The disease is mostly benign,but there is a few case reports with sequela, growth retardation and bone deformities.The disease is characterised by osteolytic and...

THU0414 Determination and quantification of synovial inflammation by magnetic resonance imaging in systemic sclerosis

BackgroundMagnetic resonance imaging (MRI) is useful method for detection and quantification of subclinical synovial inflammation and joint damage with better precision than radiography in systemic sclerosis (SSc). Early aggressive treatment...

Measures to reduce the residual field and field gradient inside a magnetically shielded room by a factor of more than 10

Abstract Very low residual magnetic field and field gradients are essential for a number of high resolution fundamental physical experiments and for further improvement of very sensitive magnetic measurement devices. The scope ranges from spin precession experiments, e.g. with 3He or neutrons, to biomagnetic measurements, like magnetoencephalograms, and to low field MR spectroscopy. One method of reducing environmental magnetic noise is to use a magnetically shielded room (MSR). Here, measures are demonstrated to improve residual field and field gradient inside a common MSR by a factor of more than 10 by a specific degaussing procedure, material selection of prefabricated parts and active shielding. The process is independent of the shielding factor and works also properly for heavily shielded rooms.

Effect of scanner acoustic background noise on strict resting-state fMRI

Functional MRI (fMRI) resting-state experiments are aimed at identifying brain networks that support basal brain function. Although most investigators consider a ‘resting-state’ fMRI experiment with no specific external stimulation, subjects are unavoidably under heavy acoustic noise produced by the equipment. In the present study, we evaluated the influence of auditory input on the resting-state networks (RSNs). Twenty-two healthy subjects were scanned using two similar echo-planar imaging sequences in the same 3T MRI scanner: a default pulse sequence and a reduced “silent” pulse sequence. Experimental sessions consisted of two consecutive 7-min runs with noise conditions (default or silent) counterbalanced across subjects. A self-organizing group independent component analysis was applied to fMRI data in order to recognize the RSNs. The insula, left middle frontal gyrus and right precentral and left inferior parietal lobules showed significant differences in the voxel-wise comparison between RSNs depending on noise condition. In the presence of low-level noise, these areas Granger-cause oscillations in RSNs with cognitive implications (dorsal attention and entorhinal), while during high noise acquisition, these connectivities are reduced or inverted. Applying low noise MR acquisitions in research may allow the detection of subtle differences of the RSNs, with implications in experimental planning for resting-state studies, data analysis, and ergonomic factors.

An Ultra Low-Power MR*1) Sensor for a Smart Water Meter or a Smart Gas Meter

A new ultra low power MR sensor comprising MR elements integrated with Bi-CMOS IC chip, which is optimal for the use in smart water meters and gas meters playing important role in global smart gridization, has been developed. MR elements are configured as a Wheatstone bridge circuit. MR element patterns are placed in the perpendicular configurations as resistive components of the circuit. Those detect the magnetic field applied to X and Y axis respectively, and then outputs either high or low-level electric signal. Optimization of the MR element pattern aspect ratio (ratio of the element length to the element width) and configuration of the two-row parallel MR patterns in a longitudinal direction enable the equivalent current flow in the direction. This provides mutual magnetostatic coupling and cancellation of each demagnetizing field, and led to achieve minimizing the hysteresis of the resistance change rate affected by up and down of the applied magnetic field. Furthermore, this led to the improvement of mutual symmetry for both S to N and N to S direction of the magnetic field. This resulted in enhanced magnetic sensitivity and successfully obtained magnetic sensitivity higher than 0.8kA/m. For the power supply of the MR sensor, external intermittent control was adopted. Furthermore, active (on) time of the MR element was considerably shortened by utilizing the internal circuit of the IC. As a result, the sampling time was shortened to 1μs and the drive current of MR sensor was reduced to 0.3 μA. *1)MR: Magneto-resistance

The insulin-mimetic effect of Morin: A promising molecule in diabetes treatment

BackgroundType-2 diabetes is a worldwidely diffuse disease characterized by insulin resistance that arises from alterations of receptor and/or post-receptor events of insulin signalling. Studies performed with PTP1B-deficent mice demonstrated that PTP1B is the main negative regulator of insulin signalling. Inhibition or down regulation of this enzyme causes enhanced insulin sensitivity. Hence this enzyme represents the most attractive target for development of innovative anti-diabetic drugs. MethodsSelection of new PTP1B inhibitors among an in house library of polyphenolic compounds was carried out screening their activity. The inhibition mechanism of Morin was determined by kinetic analyses. The cellular action of Morin was assayed on HepG2 cells. Analyses of the insulin signalling pathways was carried out by Western blot methods, glycogen synthesis was estimated by measuring the incorporation of [3H]-glucose, gluconeogenesis rate was assayed by measuring the glucose release in the cell medium. Cell growth was estimated by cell count. Docking analysis was conducted with SwissDock program. ResultsWe demonstrated that Morin: i) is a non-competitive inhibitor of PTP1B displaying a Ki in the μM range; ii) increases the phosphorylation of the insulin receptor and Akt; iii) inhibits gluconeogenesis and enhances glycogen synthesis. Morin does not enhance cell growth. ConclusionsWe have identified Morin as a new small molecular non-competitive inhibitor of PTP1B, which behaves as an activator and sensitizer of the insulin receptor stimulating the metabolic pathways only. General significanceOur study suggests that Morin is a useful lead for development of new low Mr compounds potentially active as antidiabetic drugs.

Assessment of bilateral filter on low NEX open MRI views

Purpose: A bilateral filter (BF) has the property of de-noising digital images while preserving edges. This paper investigates the impact of selecting the BF variables in order to diminish the deterioration of SNR due to reducing the number of excitations (NEX) per image in magnetic resonance imaging (MRI) technique. The paper studies the behavior of the BF on the axial, sagittal, and coronal MRI orientations acquired by spin echo (SE), turbo spin echo (TSE), and the fluid attenuated inversion recovery (FLAIR) pulse sequences from an open MRI device. Method: a set of MRI head images where acquired at different NEXs. The BF was applied at various values of window sizes, filter domains, and filter ranges. The comparison between the high NEX and the BF low NEX MR images was calculated using the peak signal-to-noise ratio (PSNR), the mean-square error (MSE), and the normalized absolute error (NAE). Results: Numerically, the BF is able to achieve up to 29, 44, and 59 % noise suppression from the T2 axial, T1 sagittal, and coronal MR views, respectively. Conclusions: The BF can successfully compensate a part of the SNR decrease due to reduce NEX. The behavior of the BF varies with the type of MR view and the type of pulse sequence. The BF is a successful tool to enhance the appearance of low NEX MR images acquired from open MR devices. This means that BF can contribute in shortening the MRI scan time.

Ischaemic mitral regurgitation: The effects of ring annuloplasty and suture annuloplasty repair techniques on left ventricular re-remodeling.

Objective: To examine the mid-term results of patients on whom a coronary revascularization as well as a mitral ring and suture annuloplasty have been performed due to coronary artery disease (CAD) and ischaemic mitral regurgitation (IMR). Methodology: Totally 73 patients on whom a revascularization and a mitral valve repair due to CAD and IMR had been performed in our clinic between 2000-2008 were included in the study. Patients were divided into two groups one of which included 38 patients (52.05%) on whom a coronary artery bypass graft (CABG) and a ring annuloplasty on the mitral valve had been performed (Group 1) and the other one 35 patients (47.95%) on whom only suture annuloplasty as well as a CABG had been performed (Group 2). The study was planned retrospectively and study data have been obtained by screening the hospital registries retrospectively. In the mid-term, patients were invited for a check and their intragroup and intergroup echocardiographic parameters and functional capacities were assessed statistically. Results: In pre-operational and post-operational intragroup assessment in terms of echocardiographic findings; although LVEDD, LVESD, EDV, PAP and the degree of recurrent MR have been decreased in both groups, the decrease in LVESD and PAP and the low degree of recurrent MR were statistically significant in Group 1 patients (p=0.047, p=0.023, p=0.01, respectively). When the mid-term intergroup echocardiograpic findings were assessed; PAP and recurrent MR have been determined statistically lower in Group 1 patients (p=0.005, p=0.08, respectively). The length of intensive care unit stay, length of hospitalization and length of detachment from respiratory support were statistically significantly longer in ring annuloplasty performed group (p=0.012, p=0.033, p=0.029, respectively). Conclusions: In moderate to severe IMR patients, a positive contribution can be provided to ventricular remodeling by a ring annuloplasty through a significant decrease in left ventricular diameter and a low recurrent MR and PAP.

Degradation of an Old Human Protein

Long-lived proteins exist in a number of tissues in the human body; however, little is known about the reactions involved in their degradation over time. Lens proteins, which do not turn over, provide a useful system to examine such processes. Using a combination of Western blotting and proteomic methodology, age-related changes to a major protein, γS-crystallin, were studied. By teenage years, insoluble intact γS-crystallin was detected, indicative of protein denaturation. This was not the only change, however, because blots revealed evidence of significant cross-linking as well as cleavage of γS-crystallin in all adult lenses. Cleavage at a serine residue near the C terminus was a major reaction that caused the release of a 12-residue peptide, SPAVQSFRRIVE, which bound tightly to lens cell membranes. Several other crystallin-derived peptides with double basic residues also lodged in the cell membrane fraction. Model studies showed that once cleaved from γS-crystallin, SPAVQSFRRIVE adopts a markedly different shape from that in the intact protein. Further, the acquired helical conformation may explain why the peptide seems to affect water permeability. This observation may help explain the changes to cell membranes known to be associated with aging in human lenses. Age-related cleavage of long-lived proteins may therefore yield peptides with untoward biological activity.

Simultaneous single‐quantum and triple‐quantum‐filtered MRI of 23Na (SISTINA)

The low MR sensitivity of the sodium nucleus and its low concentration in the human body constrain acquisition time. The use of both single-quantum and triple-quantum sodium imaging is, therefore, restricted. In this work, we present a novel MRI sequence that interleaves an ultra-short echo time radial projection readout into the three-pulse triple-quantum preparation. This allows for simultaneous acquisition of tissue sodium concentration weighted as well as triple-quantum filtered images. Performance of the sequence is shown on phantoms. The method is demonstrated on six healthy informed volunteers and is applied to three cases of brain tumors. A comparison with images from tumor specific O-(2-[18F]fluoroethyl)-L-tyrosine positron emission tomography and standard MR images is presented. The combined information of the triple-quantum-filtered images with single-quantum images may enable a better understanding of tissue viability. Future studies can benefit from the evaluation of both contrasts with shortened acquisition times.

A reverse complementary multimodal imaging system to visualize microRNA9-involved neurogenesis using peptide targeting transferrin receptor-conjugated magnetic fluorescence nanoparticles

Multimodal imaging systems may eliminate the disadvantages of individual imaging modality by providing complementary information about cellular and molecular activites. In this sutdy, we developed a reverse complementary multimodal imaging system to image microRNAs (miRNA, miR) during neurognesis using transferrin receptor (TfR) and a magnetic fluorescence (MF) nanoparticle-conjugated peptide targeting TfR (MF targeting TfR). Both in vitro and in vivo imaging demonstrated that, in the absence of miR9 during pre-differentiation of P19 cells, the MF targeting TfR nanoparticles greatly targeted TfR and were successfully internalized into P19 cells, resulting in high fluorescence and low MR signals. When the miR9 was highly expressed during neurogenesis of P19 cells, the MF targeting TfR nanoparticles were hardly targeted due to the miR9 function, which represses the expression and functional activity of TfR from the miRNA TfR reproter gene, resulting in low fluorescence and high MR signals. The reverse complementary multimodal miRNA imaging system may serve as a new imaging probe to montior miRNA-involved cellular developments and diseases.

Grain morphology and size disorder effect on the transport and magnetotransport in Sol–Gel grown nanostructured manganites

Nanostructured polycrystalline La0.7Ca0.3MnO3 (LCMO) and Nd0.7Sr0.3MnO3 (NSMO) manganites have been successfully synthesized at various temperatures ranging between 700 and 1100°C using Sol–Gel method. Crystalline nature and morphology of the samples have been studied using XRD (Rietveld analysis) and TEM measurements. SEM studies reveal nanostructured grain morphology of LCMO and NSMO samples. It is observed that, with increase in sintering temperature, crystallinity and grain morphology get improved resulting in better transport. A strong dependence of transport on size variance has been observed in the systems studied. The modified transport and better magnetotransport properties of the manganites have been observed due to the large surface to volume ratio (surface contribution) in the nanostructured manganites. The observation of large low temperature MR in both the manganite systems and the interplay between the intrinsic and extrinsic MR components has been explained in the light of spin polarized tunneling effect, grain morphology, grain boundary nature and size disorder effect.

Carrier localization and out of plane anisotropic magnetoresistance in Nd0.55−xSmxSr0.45MnO3 thin films

The impact of carrier localization on the anisotropic magnetoresistance (AMR) has been investigated in Nd0.55−xSmxSr0.45MnO3 (x = 0.00–0.45) thin films. The substitution of smaller Sm3+ cations for larger Nd3+ reduces the average radius of the A-site of the perovskite lattice and enhances size disorder. This quenched disorder results in (1) enhanced Jahn-Teller (J-T) distortion as suggested by decrease in the out of plane lattice constant, (2) stronger carrier localization as evidenced by enhancement in the activation energy of small polaron hopping, (3) decrease in the ferromagnetic (FM) and insulator-metal transition (IMT) temperatures (TC/TIM), (4) sharpening of the IMT, (5) increase in the low field MR, and (6) large enhancement in the AMR. The AMR-T curves of all the films show a maximum just below TIM. The peak AMR measured at small magnetic field of 4.2 kOe increases from −5% for x = 0.00 to −60% for x = 0.45. The enhancement in AMR has been explained in terms of the unquenching of the orbital angular momentum of t2g3 and eg1 configuration and spin fluctuations due to stronger J-T distortion at higher values of x.

Effect of Aortic Stenosis on Coronary Perfusion Studied with Wave Intensity Analysis

BackgroundAn aortic stenosis (AS) can cause angina despite normal coronary arteries. We used wave intensity (WI) to elucidate mechanisms underlying adaptation of the coronary microcirculation to AS. WI distinguishes between contributions of left ventricular (forward, FW) and microcirculatory (backward, BW) origin and between compression waves during contraction (BCW and FCW resp.) and expansion waves (FEW and BEW resp.) during relaxation.MethodsDuring cardiac catheterization we simultaneously measured aortic pressure, coronary pressure (Pd) and flow velocity (U) at rest and at maximal hyperemia in 12 patients without and in 10 patients with severe AS. WI was calculated as (dPd/dt)(dU/dt) and the energy of separated BW and FW contributions was derived.ResultsU at rest was about 20 cm/s in both groups. Compared to no AS, Pd was 17% lower (p< 0.01) with AS, while microvascular resistance (MR=Pd/U) was 30% lower (p<0.05). Hyperemic Pd and MR did not differ, while U was 20% lower (p<0.05) in AS. Compression wave energy remained similar. However, FEW in AS was 43% lower at rest and 66% lower at hyperemia (p<0.05). The BEW in AS was 50% higher at rest (p<0.05), correlating with the lower MR (p<0.05, r=0.45), and not different at hyperemia.ConclusionAS primarily affects the expansion waves and hence hampers coronary perfusion during cardiac relaxation.Support: FP7‐ICT 2007224495 (euHeart)

The “CHAFT” Mnemonic for Musculoskeletal Lesions With Low T2 Signal Intensity

Editor's Note: Utilization by diagnostic radiologists of the “CHAFT” mnemonic for identification of musculoskeletal, brain and spine, and abdominal lesions with low T2 MR signal intensity on MRI will be presented in 3 sequential articles: Volume 35, Numbers 6, 7, and 8, respectively. Musculoskeletal lesions that present with low T2 MR signal intensity have a limited list of differential diagnoses. The objectives of this pictorial CME presentation are to review briefly the MR physics of low T2 signal, to introduce the “CHAFT” mnemonic to provide a framework for the differential diagnosis, and to demonstrate the importance of radiographic correlation in arriving at the correct diagnosis.

Correlation between microstructure and electromagnetic properties in magnetic tunnel junctions with naturally oxidized MgO barrier

We investigated the correlation between the microstructure and the electromagnetic properties of magnetic tunnel junctions (MTJs) with MgO barriers fabricated by direct sputtering and natural oxidation of the Mg layers. The MTJ with an oxidized Mg barrier contained amorphous phases in both the barrier and the CoFeB free layer and exhibited large interface fluctuations in both the CoFeB reference/MgO and MgO/CoFeB interfaces This had a significant influence on the low MR ratio and large switching current. Inserting a CoFe seed layer under the oxidized Mg barrier greatly improved the crystallization of the oxidized MgO which ultimately led to a higher MR ratio and lower switching current. In addition to the textured CoFeB/MgO/CoFeB structures, the sharp interface of the MgO barrier, low B content in the MgO barrier, and Fe-rich composition in the free layer are thought to be of key importance for ensuring high magneto-transport properties.

Evaluation of a lung tumor autocontouring algorithm for intrafractional tumor tracking using low-field MRI: A phantom study

The first aim of this study is to investigate the feasibility of online autocontouring of tumor in low field MR images (0.2 and 0.5 T) by means of a phantom and simulation study for tumor-tracking in linac-MR systems. The second aim of this study is to develop an MR compatible, lung tumor motion phantom. An autocontouring algorithm was developed to determine both the position and shape of a lung tumor from each intra fractional MR image. To initiate the algorithm, an expert user contours the tumor and its maximum anticipated range of motion (herein termed the Background) using pretreatment scan data. During treatment, the algorithm processes each intrafractional MR image and automatically contours the tumor. To evaluate this algorithm, the authors built a phantom that replicates the low field contrast parameters (proton density, T(1), T(2)) of lung tumors and healthy lung parenchyma. This phantom allows simulation of MR images with the expected lung tumor CNR at 0.2 and 0.5 T by using a single 3 T scanner. Dynamic bSSFP images (approximately 4 images per second) are acquired while the phantom undergoes a series of preprogrammed motions based on patient lung tumor motion data. These images are autocontoured off-line using our algorithm. The fidelity of autocontouring is assessed by comparing autocontoured tumor shape and its centroid position to the actual tumor shape and its position. The algorithm successfully contoured the shape of a moving tumor model from dynamic MR images acquired every 275 ms. Dice's coefficients of > 0.96 and > 0.93 are achieved in 0.5 and 0.2 T equivalent images, respectively. Also, the algorithm tracked tumor position during dynamic studies, with root mean squared error (RMSE) values of < 0.55 and < 0.92 mm for 0.5 and 0.2 T equivalent images, respectively. Autocontouring speed is approximately 5 ms for each image. Dice's coefficients of > 0.96 and > 0.93 are achieved between autocontoured and real tumor shapes, and the position of a tumor can be tracked with RMSE values of < 0.55 and < 0.92 mm in 0.5 and 0.2 T equivalent images, respectively. These results demonstrate the feasibility of lung tumor autocontouring in low field MR images, and, by extension, intrafractional lung tumor tracking with our laboratory's linac-MR system.

Caldesmon Regulates Axon Extension through Interaction with Myosin II

To begin the process of forming neural circuits, new neurons first establish their polarity and extend their axon. Axon extension is guided and regulated by highly coordinated cytoskeletal dynamics. Here we demonstrate that in hippocampal neurons, the actin-binding protein caldesmon accumulates in distal axons, and its N-terminal interaction with myosin II enhances axon extension. In cortical neural progenitor cells, caldesmon knockdown suppresses axon extension and neuronal polarity. These results indicate that caldesmon is an important regulator of axon development.

Microtubule Affinity Regulating Kinase Activity in Living Neurons Was Examined by a Genetically Encoded Fluorescence Resonance Energy Transfer/Fluorescence Lifetime Imaging-based Biosensor

Protein kinases of the microtubule affinity regulating kinase (MARK)/Par-1 family play important roles in the establishment of cellular polarity, cell cycle control, and intracellular signal transduction. Disturbance of their function is linked to cancer and brain diseases, e.g. lissencephaly and Alzheimer disease. To understand the biological role of MARK family kinases, we searched for specific inhibitors and a biosensor for MARK activity. A screen of the ChemBioNet library containing ~18,000 substances yielded several compounds with inhibitory activity in the low micromolar range and capable of inhibiting MARK activity in cultured cells and primary neurons, as judged by MARK-dependent phosphorylation of microtubule-associated proteins and its consequences for microtubule integrity. Four of the compounds share a 9-oxo-9H-acridin-10-yl structure as a basis that will serve as a lead for optimization of inhibition efficiency. To test these inhibitors, we developed a cellular biosensor for MARK activity based on a MARK target sequence attached to the 14-3-3 scaffold protein and linked to enhanced cyan or teal and yellow fluorescent protein as FRET donor and acceptor pairs. Transfection of the teal/yellow fluorescent protein sensor into neurons and imaging by fluorescence lifetime imaging revealed that MARK was particularly active in the axons and growth cones of differentiating neurons.