Self-Isolated Dual-Mode High-Pass Birdcage RF Coil for Proton and Sodium MR Imaging at 7 T MRI

This study presents the feasibility of a dual-mode high-pass birdcage RF coil to acquire MR images at both 1H and 23Na frequencies at ultra-high-field MR scanner, 7 T. A dual-mode circuit (DMC) in the dual-mode birdcage (DMBC) RF coil operates at two frequencies, addressing the limitations of sensitivity reduction and isolation between two frequencies as in traditional dual-tuned RF coil. Finite-difference time-domain (FDTD) based electromagnetic (EM) simulations were performed to verify the RF coil at each frequency on the three-dimensional human head model. The DMBC RF coil resonated at proton (1H) and sodium (23Na) frequencies, and also single-tuned high-pass birdcage RF coils were constructed for both 1H and 23Na frequencies. The bench test performance of the RF coils was evaluated using network analysis parameters, including the measurement of scattering parameters (S-parameters) and quality factors (Q-factors). Q-factor of the DMBC coil at 1H port was 10.2% lower than that of 1H single-tuned birdcage (STBC) coil, with a modest SNR reduction of 6.5%. Similarly, the Q-factor for the DMBC coil at 23Na port was 12.3% less than that of 23Na STBC coil, and the SNR showed a minimal reduction of 5.4%. Utilizing the DMBC coil, promising 1H and 23Na MR images were acquired compared to those by using STBC coils. In conclusion, deploying a DMBC 1H/23Na coil has been demonstrated to overcome traditional constraints associated with dual-tuned RF coils, achieving this with only nominal signal attenuation across both nuclei operational frequencies

Spectrum of movement disorders in GNAO1 encephalopathy: in-depth phenotyping and case-by-case analysis

Background GNAO1 encephalopathy is a rare neurodevelopmental disorder characterized by distinct movement presentations and early onset epileptic encephalopathy. Here, we report the in-depth phenotyping of genetically confirmed patients with GNAO1 encephalopathy, focusing on movement presentations. Results Six patients who participated in Korean Undiagnosed Disease Program were diagnosed to have pathogenic or likely pathogenic variants in GNAO1 using whole exome sequencing. All medical records and personal video clips were analyzed with a literature review. Three of the 6 patients were male. Median follow-up duration was 41 months (range 7–78 months) and age at last examination was 7.4 years (range 3.3–16.9 years). Initial complaints were hypotonia or developmental delay in 5 and right-hand clumsiness in 1 patient, which were noticed at median age of 3 months (range 0–75 months). All patients showed global developmental delay and 4 had severely retarded development. Five patients (5/6, 83.3%) had many different movement symptoms with various onset and progression. The symptoms included stereotyped hands movement, non-epileptic myoclonus, dyskinesia, dystonia and choreoathetosis. Whole exome sequencing identified 6 different variants in GNAO1. Three were novel de novo variants and atypical presentation was noted in a patient. One variant turned out to be inherited from patients mother who had mosaic variant. Distinct and characteristics movement phenotypes in patients with variant p.Glu246Lys and p.Arg209His were elucidated by in-depth phenotyping and literature review. Conclusions We reported 6 patients with GNAO1 encephalopathy showing an extremely diverse clinical spectrum on video. Some characteristic movement features identified by careful inspection may also provide important diagnostic insight and practice guidelines.This study was supported by a research program funded by the Korea Centers for Disease Control and Prevention (Grant No. 2018-ER6901-02)

Response of the primary auditory and non-auditory cortices to acoustic stimulation: A manganese-enhanced MRI study

Structural and functional features of various cerebral cortices have been extensively explored in neuroscience research. We used manganese-enhanced MRI, a non-invasive method for examining stimulus-dependent activity in the whole brain, to investigate the activity in the layers of primary cortices and sensory, such as auditory and olfactory, pathways under acoustic stimulation. Male Sprague-Dawley rats, either with or without exposure to auditory stimulation, were scanned before and 24-29 hour after systemic MnCl2 injection. Cortex linearization and layer-dependent signal extraction were subsequently performed for detecting layer-specific cortical activity. We found stimulus-dependent activity in the deep layers of the primary auditory cortex and the auditory pathways. The primary sensory and visual cortices also showed the enhanced activity, whereas the olfactory pathways did not. Further, we performed correlation analysis of the signal intensity ratios among different layers of each cortex, and compared the strength of correlations between with and without the auditory stimulation. In the primary auditory cortex, the correlation strength between left and right hemisphere showed a slight but not significant increase with the acoustic simulation, whereas, in the primary sensory and visual cortex, the correlation coefficients were significantly smaller. These results suggest the possibility that even though the primary auditory, sensory, and visual cortices showed enhanced activity to the auditory stimulation, these cortices had different associations for auditory processing in the brain network.open0

Quantitative in-vivo imaging of tumor microenvironments

Tumor hypoxia, which develops heterogeneously in locally advanced tumors is known to affect radiation sensitivity and development to metastases. In vivo knowledge of hypoxia distribution in solid tumors provides prognostic information and can be potentially used for input for dose escalation in radiation therapy. Tumor hypoxia results from a mismatch between supply and consumption of oxygen in a tumor. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is well known to provide permeability/perfusion information of solid tumors and may provide surrogate information regarding tumor hypoxia. In this study, (1) DCE-MRI data with the injection of Gd-DTPA was analyzed with Gaussian mixture model (GMM) based classification to verify regions of perfused, hypoxic, necrotic areas in a prostate rat tumor model. The results of pattern recognition on the DCE-MRI show the feasibility on delineation of tumor microenvironments. (2) To increase the spatial/temporal accuracy of such classification, a compressed sensing algorithm is used to enhance the quality of DCE-MRI uptake curves

A Quick Method to Measure Hydroxyl Ion Contents in Bone Mineral Crystals Using Solid State NMR

A 31P CP MAS technique with a pre-saturation pulse was developed to measure OH- contents of bone quickly. This technique could save experimental time at least 128 times compared with a 2D 1H-31P HetCor technique. It also yielded higher signal to noise ratio (SNR), which decreased measurement error. The OH- content in bovine bone was 66.1 mol%

Actuation and locomotion driven by moisture in paper made with natural pollen

Here we describe the development of a humidity-responsive sheet of paper that is derived solely from natural pollen. Adaptive soft material components of the paper exhibit diverse and well-integrated responses to humidity that promote shape reconfiguration, actuation, and locomotion. This mechanically versatile and nonallergenic paper can generate a cyclically high contractile stress upon water absorption and desorption, and the rapid exchange of water drives locomotion due to hydrodynamic effects. Such dynamic behavior can be finely tuned by adjusting the structure and properties of the paper, including thickness, surface roughness, and processing conditions, analogous to those of classical soapmaking. We demonstrate that humidity-responsive paper-like actuators can mimic the blooming of the Michelia flower and perform self-propelled motion. Harnessing the material properties of bioinspired systems such as pollen paper opens the door to a wide range of sustainable, eco-friendly, and biocompatible material innovation platforms for applications in sensing, actuation, and locomotion.Agency for Science, Technology and Research (A*STAR)National Research Foundation (NRF)Published versionThis work was supported by the National Research Foundation of Singapore through a Competitive Research Program grant (NRF-CRP10-2012-07) and by Agency for Science, Technology and Research (A*STAR) through the A*STAR Advanced Manufacturing and Engineering Individual Research Grants (AME IRG) (A1983c0031). S.S. acknowledges support from Nanyang Technological University, Singapore, through a Distinguished University Professorship

Evaluation of MRI resolution affecting trabecular bone parameters: Determination of acceptable resolution

The objective of this study is to evaluate the effect of MR image resolution on trabecular bone parameters and to determine the acceptable resolution that can be accurately analyzed to assess structural parameters. Ten distal femoral condyle specimens of 1 x 1 x 1 cm3 were scanned with a 4.7-T Bruker BioSpec MRI scanner using a three-dimensional fast large-angle spin-echo sequence with various iso-cubic voxels sizes (65, 130, 160, 196, 230, and 260 mu m). Otsu thresholding was applied to identify voxels containing bone. Conventional bone parameters, structural bone parameters, and skeleton-based local trabecular thickness (slTB.Th) were evaluated. The BlandAltman method and correlation indicated that the conventional and structural bone parameters were preserved with an iso-cubic voxel size up to 230 mu m (r > 0.932 and r > 0.843, respectively). In addition, slTB.Th derived from the highest resolution images (65 mu m iso-cubic voxel size), correlated well (r > 0.833) with the values computed from lower resolution images, up to 230 mu m, which is twice typical human trabecular thickness range (100150 mu m). The outcome of this study suggests that the various bone parameters were well preserved up to 230 mu m images. Magn Reson Med, 2011. (C)2011 Wiley-Liss, Inc.OAIID:oai:osos.snu.ac.kr:snu2012-01/102/0000004226/1SEQ:1PERF_CD:SNU2012-01EVAL_ITEM_CD:102USER_ID:0000004226ADJUST_YN:YEMP_ID:A076317DEPT_CD:801CITE_RATE:2.964FILENAME:E037T_Magn Reson Med-2012_Kim_Evaluation of MRI resolution affecting trabecular bone parameters.pdfDEPT_NM:의학과SCOPUS_YN:YCONFIRM:

Task-residual effective connectivity of motor network in transient ischemic attack

Abstract Transient ischemic attack (TIA) is a temporary episode of neurological dysfunction that results from focal brain ischemia. Although TIA symptoms are quickly resolved, patients with TIA have a high risk of stroke and persistent impairments in multiple domains of cognitive and motor functions. In this study, using spectral dynamic causal modeling, we investigate the changes in task-residual effective connectivity of patients with TIA during fist-closing movements. 28 healthy participants and 15 age-matched patients with TIA undergo functional magnetic resonance imaging at 7T. Here we show that during visually cued motor movement, patients with TIA have significantly higher effective connectivity toward the ipsilateral primary motor cortex and lower connectivity to the supplementary motor area than healthy controls. Our results imply that TIA patients have aberrant connections among motor regions, and these changes may reflect the decreased efficiency of primary motor function and disrupted control of voluntary movement in patients with TIA

Temporal/spatial resolution improvement of in vivo DCE-MRI with compressed sensing-optimized FLASH

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) provides critical information regarding tumor perfusion and permeability by injecting a T-1 contrast agent, such as Gd-DTPA, and making a time-resolved measurement of signal increase. Both temporal and spatial resolutions are required to be high to achieve an accurate and reproducible estimation of tumor perfusion. However, the dynamic nature of the DCE experiment limits simultaneous improvement of temporal and spatial resolution by conventional methods. Compressed sensing (CS) has become an important tool for the acceleration of imaging times in MRI, which is achieved by enabling the reconstruction of subsampled data. Similarly, CS algorithms can be utilized to improve the temporal/spatial resolution of DCE-MRI, and several works describing retrospective simulations have demonstrated the feasibility of such improvements. In this study, the fast low angle shot sequence was modified to implement a Cartesian, CS-optimized, sub-Nyquist phase encoding acquisition/reconstruction with multiple two-dimensional slice selections and was tested on water phantoms and animal tumor models. The mean voxel-level concordance correlation coefficient for Ak(ep) values obtained from x4 and x8 accelerated and the fully sampled data was 0.87 +/- 0.11 and 0.83 +/- 0.11, respectively (n=6), with optimized CS parameters. In this case, the reduction of phase encoding steps made possible by CS reconstruction improved effectively the temporal/spatial resolution of DCE-MRI data using an in vivo animal tumor model (n=6) and may be useful for the investigation of accelerated acquisitions in preclinical and clinical DCE-MRI trials.close

Unraveling the distinct germination processes of sporopollenin-based pollen grains and spores through morphological analyses upon natural nano-architectonics process

The outermost exine capsules of many pollen and spore grains are composed of a chemically inert yet mechanically robust sporopollenin biopolymer. These dynamically expansible and foldable capsules have great potential as renewable functional biomaterials with industrial applications. However, the mechanical and morphological variations in the shape, size, robustness, and apertural strength of the exine capsules across taxa of angiosperms and cryptogamic plants remains poorly understood. Thus, in this study, we unraveled the abortive microgel transformation of spores inspired by their germination mechanism, being compared with eudicot-based pollen microgels. After chemical treatments, significant mechanical degradation of exine was clearly observed for the Camellia pollen, whereas crosslinking density and modulus of spore exine remained almost constant. The significant volume expansion of Camellia pollen was observed akin to sunflower pollen; in contrast, the spores ballooned showed limited volume changes under equal levels of turgor pressure. Furthermore, spore underwent marked changes in volume when their aperture sutures were softened and ruptured, which are prerequisites for spore germination. Therefore, this study disentangled mechanical and morphological origins of biochemical pathways of pollen and spore germination, and germination-like hydration and desiccation, which will give clues about selection of pollen and spore species for potential biomaterial applications.Agency for Science, Technology and Research (A*STAR)This research was supported by Advanced Manufacturing and Engineering Individual Research Grants (AME IRG) (A1983c0031) through the Agency for Science, Technology and Research (A∗STAR)