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A higher selectivity to C2−C4 hydrocarbons and clean fuels without significant deactivation during CO hydrogenation by a typical Fischer‐Tropsch synthesis (FTS) was observed on the ordered mesoporous 5wt %Al‐modified Co3O4‐Fe2O3 bimetal oxides (m‐CoFe) at a Co/Fe molar ratio of ∼1, which was prepared by a hard templating and co‐infiltration method. The active sites were related with the partially oxidized Co nanoparticles as well as iron carbides. The structurally stable and strongly interacted ordered Co3O4‐Fe2O3 mesoporous structures were preferentially transformed to more brittle iron carbides with a simultaneous reduction of Co3O4 to metallic Co under a reductive FTS reaction condition. The m‐CoFe(1) itself without using any solid acid component revealed a higher C2−C4 selectivity of 21.1 % and C5+ selectivity of 67.9 % at CO conversion of 88.5 % with the corresponding rate of 2.77 mmol/(gcat⋅s) by enhancing its structural stability due to the partial formations of thermally stable spinel‐type CoFe2O4. The enhanced structural stability of the m‐CoFe(1) was attributed to the preferential formations of the strongly interacted and partially oxidized Co nanoparticles with the formation of active iron carbides as well. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study was to assess neuropsychological correlations with the T2* relaxation time (T2*‐RT) of hippocampal subregions in adolescents using ultra‐high‐field (UHF) 7.0‐T magnetic resonance imaging (MRI). Methods: We assessed the T2*‐RT of hippocampal subregions in 31 healthy 11th‐ or 12th‐grade high school students using an UHF 7.0‐T MRI system. T2*‐RT of the cornu ammonis (CA) 1, CA2, CA3, and CA4 subregions and the subiculum were calculated for both the left and right hippocampus. Seven subtests of the Cambridge Neuropsychological Test Automated Battery were administered to the subjects to assess visuospatial memory. Results: Poor performances in delayed recall in the pattern‐recognition test were significantly correlated with longer T2*‐RT in the bilateral subiculum (right, r = −0.480, P = 0.006; left, r = −0.648, P < 0.001) and the left CA2 (r = −0.480, P = 0.006). Conclusion: This study showed that longer T2*‐RT in the subiculum were associated with poorer performances in delayed recall in the visual memory tasks. This finding suggests that the subiculum might play a predominant role in delayed recall in adolescents. [ABSTRACT FROM AUTHOR]

Purpose To propose a new Extended Monopole antenna Array with individual Shields (EMAS) coil that improves the B1 field coverage and uniformity along the z-direction. Methods To increase the spatial coverage of Monopole antenna Array (MA) coil, each monopole antenna was shielded and extended in length. Performance of this new coil, which is referred to as EMAS coil, was compared with the original MA coil and an Extended Monopole antenna Array coil with no shield (EMA). For comparison, flip angle, signal-to-noise ratio (SNR), and receive sensitivity maps were measured at multiple regions of interest (ROIs) in the brain. Results The EMAS coil demonstrated substantially larger flip angle and receive sensitivity than the MA and EMA coils in the inferior aspect of the brain. In the brainstem ROI, for example, the flip angle in the EMAS coil was increased by 45.5% (or 60.0%) and the receive sensitivity was increased by 26.9% (or 14.9%), resulting in an SNR gain of 84.8% (or 76.3%) when compared with the MA coil (or EMA). Conclusion The EMAS coil provided 25.7% (or 24.4%) more uniform [ABSTRACT FROM AUTHOR]

ABSTRACT 7 T arterial spin labeling (ASL) faces major challenges including the increased specific absorption rate (SAR) and increased B0 and B1 inhomogeneity. This work describes the design and implementation of a dual-coil system that allows for continuous ASL (CASL) at 7 T. This system consisted of an actively detunable eight-channel transceiver head coil, and a three-channel transceiver labeling coil. Four experiments were performed in 5 healthy subjects: (i) to demonstrate that active detuning during ASL labeling reduces magnetization transfer; (ii) to measure the B1 profile at the labeling plane; (iii) to quantify B0 off-resonance at the labeling plane; and (iv) to collect in vivo CASL data. The magnetization transfer ratio in the head coil was reduced to 0.0 ± 0.2% by active detuning during labeling. The measured B1 profiles in all 5 subjects were sufficient to satisfy the flow-driven adiabatic inversion necessary for CASL, however the actual labeling efficiency was significantly impacted by B0 off-resonance at the labeling plane. The measured CASL percent signal change in gray matter (0.94% ± 0.10%) corresponds with the low labeling efficiency predicted by the B0 off-resonance. This work demonstrates progress in the technical implementation of 7 T CASL, and reinforces the need for improved B0 homogeneity at the labeling plane. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to measure the velocity and direction of blood flow in microvessels, such as lenticulostriate arteries (LSAs), using PC MRA. Methods: Eleven healthy subjects were scanned with 7 Tesla (T) MRI. Three velocity encoding (VENC) values of 15, 50, and 100 cm/s were tested for detecting the flow velocity in LSAs. The flow directions in Circle of Willis (CoW) were also examined with images obtained by the proposed method. Three subjects were also scanned with 3T MRI to determine the possibility of velocity measurement in LSAs. Difference between 3T and 7T was quantitatively analyzed in terms of signal-tonoise ratio and velocities in vessels and static tissues. Results: In 7T MRI, use of VENC=15 cm/s provided great visualization and velocity measurements in small and slow flowing vessels, such as the LSAs. The mean of peak velocities in LSAs was 9.6161.78 cm/s. The results obtained with low VENC also clearly depicted the directions of flow in CoW, especially in posterior communicating arteries. However, 3T MRI could not detect the velocity of blood flow in LSAs. Conclusion: This study demonstrated the potential for measuring the velocity and direction of blood flow in the targeted microvessels using an appropriate VENC and 7T MRI. [ABSTRACT FROM AUTHOR]

ABSTRACT Surgical or endovascular approaches have proved effective for large-vessel diseases over the past decade. However, approaches for small vessel diseases are unlikely to be accomplished by those for large vessels and only few have been applied, because it is hard to access to those small vessels and one could not directly delineate the affected small vessels due to a lack of detection modalities. This study is to examine patients with vascular diseases using ultra-high field 7T MRI with conventional time-of-flight (TOF) sequence, 3D fast low-angle shot (FLASH) gradient-echo. We have evaluated several radio-frequency (RF) coils to find the optimal one for 7T magnetic resonance angiography (MRA), especially for micro-vascular imaging. We have conducted several comparison studies with vascular disease patients. The results showed that micro-vessels such as lenticulostriate arteries in the subjects with risk factors like hypertension or stroke patients were significantly less than in the healthy subjects. 7T MRA images in steno-occlusive patients also showed clearly numerous collateral vessels not visible by 1.5T or 3T MRA. Furthermore, 7T MRA images were comparable to those obtained by digital subtraction angiography (DSA), particularly for micro-vascular imaging. In this article, we would like to share the clinical experiences on 7T MRA that vascular images of 7T MRA were superior to conventional angiography images including 1.5T and 3T MRA, and even comparable to DSA. We also expect that further technical development and clinical applications of 7T MRA would be a clinically important diagnostic tool, in terms of an early detection of the stroke in a totally non-invasive manner. © 2014 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 24, 121-128, 2014 [ABSTRACT FROM AUTHOR]

Purpose We have developed and evaluated a monopole antenna array that can increase sensitivity at the center of the brain for 7T MRI applications. Methods We have developed a monopole antenna array that has half the length of a conventional dipole antenna with eight channels for brain imaging with a 7T MRI. The eight-channel monopole antenna array and conventional eight-channel transceiver surface coil array were evaluated and compared in terms of transmit properties, specific absorption ratio (SAR), and sensitivity. The sensitivity maps were generated by dividing the SNR map by the flip angle distribution. Results A single surface coil provides asymmetric sensitivity resulting in reduced sensitivity at the center of the brain. In contrast, a single monopole antenna provides higher sensitivity at the center of the brain. Moreover, the monopole antenna array provides uniform sensitivity over the entire brain, and the sensitivity gain was 1.5 times higher at the center of the brain compared with the surface coil array. Conclusion The monopole antenna array is a promising candidate for MRI applications, especially for brain imaging in a 7T MRI because it provides increased sensitivity at the center of the brain. Magn Reson Med 71:1944-1952, 2014. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The thalamus is one of the most important brain structures, with strong connections between subcortical and cortical areas of the brain. Most of the incoming information to the cortex passes through the thalamus. Accurate identification of substructures of the thalamus is therefore of great importance for the understanding of human brain connectivity. Direct visualization of thalamic substructures, however, is not easily achieved with currently available magnetic resonance imaging (MRI), including ultra-high field MRI such as 7.0T, mainly due to the limited contrast between the relevant structures. Recently, improvements in ultra-high field 7.0T MRI have opened the possibility of observing thalamic substructures by well-adjusted high-resolution T1-weighted imaging. Moreover, the recently developed super-resolution track-density imaging (TDI) technique, based on results from whole-brain fiber-tracking, produces images with sub-millimeter resolution. These two methods enable us to show markedly improved anatomical detail of the substructures of the thalamus, including their detailed locations and directionality. In this study, we demonstrate the role of TDI for the visualization of the substructures of the thalamic nuclei, and relate these images to T1-weighted imaging at 7.0T MRI. Hum Brain Mapp 34:2538-2548, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Despite its wide use, echo-planar imaging (EPI) suffers from geometric distortions due to off-resonance effects, i.e., strong magnetic field inhomogeneity and susceptibility. This article reports a novel method for correcting the distortions observed in EPI acquired at ultra-high-field such as 7 T. Point spread function (PSF) mapping methods have been proposed for correcting the distortions in EPI. The PSF shift map can be derived either along the nondistorted or the distorted coordinates. Along the nondistorted coordinates more information about compressed areas is present but it is prone to PSF-ghosting artifacts induced by large k-space shift in PSF encoding direction. In contrast, shift maps along the distorted coordinates contain more information in stretched areas and are more robust against PSF-ghosting. In ultra-high-field MRI, an EPI contains both compressed and stretched regions depending on the B0 field inhomogeneity and local susceptibility. In this study, we present a new geometric distortion correction scheme, which selectively applies the shift map with more information content. We propose a PSF-ghost elimination method to generate an artifact-free pixel shift map along nondistorted coordinates. The proposed method can correct the effects of the local magnetic field inhomogeneity induced by the susceptibility effects along with the PSF-ghost artifact cancellation. We have experimentally demonstrated the advantages of the proposed method in EPI data acquisitions in phantom and human brain using 7-T MRI. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Microvascular functional MR angiography using ultra-high-field 7 T MRI was used to visualize specific arterial changes in response to stimulation, and the results were compared to conventional blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI). To demonstrate the potential of this new method, we conducted a visual experiment with 14 healthy subjects using optimized acquisition parameters and a dedicated radio frequency coil for 7 T MRI. The signal intensity change in the blood vessels supplying to the visual cortex, specifically the calcarine arteries, was clearly observed during stimulation. The signal changes were increased gradually up to as high as 12% as the vessel segments approach to the visual cortex where neuronal activity was believed to be occurred. The activation foci were not identical to those obtained by conventional fMRI, as expected, but they were closely related and confined to the visual cortical areas, when compared to fMRI responses. Therefore, fMRA technique using ultra-high-field 7 T MRI could provide the direct observation of microvascular changes in the arterial input vessels in relation to neuronal activity. © 2012 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 22, 18-22, 2012 [ABSTRACT FROM AUTHOR]

Objective: To investigate anatomical changes in the substantia nigra (SN) of Parkinson disease (PD) patients with age-matched controls by using ultra-high field magnetic resonance imaging (MRI). Methods: We performed 7T MRI in 10 PD and 10 age-matched control subjects. Magnetic resonance images of the SN were obtained from a 3-dimensional (3D) T2*-weighted gradient echo sequence. Region of interest-based 3D shape analysis was performed to quantitatively compare images from the 2 groups. Results: The boundary between the SN and crus cerebri was not smooth in PD subjects. Undulation in the lateral surface of the SN appeared more intense in the side contralateral to that with the more severe symptoms, and more prominent at the rostral level of the SN than at the intermediate or caudal levels. In addition to the lateral surface, there was a striking difference in the dorsomedial aspects of the SN between PD and control subjects. In control subjects, a brighter signal region was observed along the dorsomedial surface of the lateral portion of SN, whereas in PD subjects, this region was observed as a dark region containing a hypointense signal in T2*-weighted images. The measurement of SN volumes, normalized to the intracranial volumes, showed higher values in PD subjects than in control subjects. Interpretation: This study demonstrates that 3D 7T MRI can definitively visualize anatomical alterations occurring in the SN of PD subjects. Further pathological studies are required to elucidate the nature of these anatomical alterations. Ann Neurol 2012;71:267-277 [ABSTRACT FROM AUTHOR]

Parkinson's disease (PD) is a neurodegenerative disorder resulting from the progressive loss of dopaminergic (DA) neurons in the substantia nigra (SN). In our previous study, attempts were made to directly visualize the SN and quantify the differences in shapes and boundaries of the SN between PD subjects and comparison to the normal control subjects using two-dimensional T2*-weighted 7.0-T MRI images (Cho et al., Mov Disord, accepted for publication). However, a two-dimensional analysis does not represent the entire SN. Therefore, to overcome the limitation of 2D analysis, we acquire 3D image of the SN. For this study, we scanned nine PD patients, along with nine age-matched control subjects, using a research prototype 7.0-T MRI scanner in an attempt to visualize the 3D shape of the SN and quantify differences in the volume of the SN between PD subjects and normal control subjects. The shape change of the ventrolateral boundaries of the SN in PD cases was reconfirmed in this 3D study as well as in our previous 2D study (Cho et al., Mov Disord, accepted for publication). Another interesting finding of this study was that 3D MR imaging study demonstrated the potential of the 7.0-T MRI in the quantification of volume changes in the SN. The measured correlation analyses showed that there is age-dependent correlation and substantially stronger unified Parkinson's disease rating scale motor score-dependent correlation in PD patients. These results suggest that 7.0-T 3D T2*-weighted MR imaging could provide the quantitative estimation of volume changes in the SN in PD patients in vivo for comparison with normal controls in vivo. © 2011 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 21, 253-259, 2011; [ABSTRACT FROM AUTHOR]

Purpose: To visualize the perforating arteries originating from basilar artery (BA) by using ultra-high resolution 7T MR angiography (MRA) and optimizing MR parameters as well as radio frequency (RF) coils, which may provide important information for neurosurgery and understanding diseases of the pons, but was unable to clearly visualize with conventional MRA techniques. Materials and Methods: Seven healthy volunteers (five males and two females, age [mean ± SD] = 28.71 ± 7.54 years) were scanned using optimized MR parameters to obtain images of pontine arteries (PAs) originating from the main trunk of BA. Two different volume coils and a phased array coil were designed and compared for this study. The images obtained at 7T MRA were compared with those at 1.5T and 3T MRA. Results: The results showed that PA imaging at 7T MRI consistently provided clearly identifiable vessels, which were difficult to visualize in MR angiograms obtained at 1.5T and 3T MRIs. Volume RF coils had higher sensitivity for the center of the brain, which enhanced PA imaging compared to phased array coil. The average number of PA branches in all seven subjects observable by 7T MRA was 7.14 ± 2.79, and the visualized PA branches were found to mainly propagating on the surface of the pons. Conclusion: We have demonstrated that ultra-high resolution 7T MRA could delineate the PAs using optimized imaging parameters and volume RF coils compared to commercially available 1.5T and 3T MRIs. J. Magn. Reson. Imaging 2010;32:544-550. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The purpose of this study was to describe relevant canine brain structures as seen on T2-weighted images following magnetic resonance (MR) imaging at 7 T and to compare the results with imaging at 1.5 T. Imaging was performed on five healthy laboratory beagle dogs using 1.5 and 7 T clinical scanners. At 1.5 T, spin echo images were acquired, while gradient echo images were acquired at 3 T. Image quality and conspicuity of anatomic structures were evaluated qualitatively by direct comparison of the images obtained from the two different magnetic fields. The signal-to-nose ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared between 1.5 and 7 T. The T2-weighted images at 7 T provided good spatial and contrast resolution for the identification of clinically relevant brain anatomy; these images provided better delineation and conspicuity of the brain stem and cerebellar structures, which were difficult to unequivocally identify at 1.5 T. However, frontal and parietal lobe and the trigeminal nerve were difficult to identify at 7 T due to susceptibility artifact. The SNR and CNR of the images at 7 T were significantly increased up to 318% and 715% compared with the 1.5 T images. If some disadvantages of 7 T imaging, such as susceptibility artifacts, technical difficulties, and high cost, can be improved, 7 T clinical MR imaging could provide a good experimental and diagnostic tool for the evaluation of canine brain disorders. [ABSTRACT FROM AUTHOR]

The purpose of this study was to analyze human lenticulostriate arteries (LSAs) obtained non-invasively by 7.0-T MRI. A three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA) technique was used with an investigational 7.0-T MRI scanner with a radio-frequency coil that was optimized and designed for angiographic purposes. We obtained images from 16 healthy volunteers (8 males and 8 females, mean age 21 ± 2.7 years). For direct comparison of LSA images with digital subtraction angiography (DSA), we also obtained 7.0-T MRA and DSA images from one patient, a 27-year-old woman with a posterior fossa arteriovenous malformation (AVM). We then analyzed the characteristics of LSAs using a custom data analysis method with MatLab for quantitative analysis. Analysis of LSA images included shape and number of branches and origins, findings that are essential and useful for quantification of LSA abnormalities in both healthy controls and patients. Ultra-high-field MRA provided clear anatomic delineation of the LSAs, thereby suggesting that 7.0-T MRA may be a promising technique for microvascular imaging of the LSAs. Magn Reson Med 61:136-144, 2009. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose To implement a method using a tailored radiofrequency (TRF) pulse with a quadratic phase profile to recover susceptibility-induced signal losses in gradient-recalled echo-planar images (EPI). Materials and Methods A functional magnetic resonance imaging (fMRI) experiment for compensation of susceptibility artifacts, known as the TRF pulse EPI sequence (TRF-EPI), was used. TRF pulse compensates the susceptibility effect with a reduced signal-to-noise ratio (SNR) to one-half when the maximum phase distribution is 2π. We demonstrate theoretically that the maximum phase distribution can also be reduced to π rather than 2π, improving the SNR accordingly. An analysis was conducted comparing this newly proposed strategy using a standard RF excitation with a linear phase distribution and a quadratic TRF excitation with a π phase distribution. Results Thorough experimental comparisons were also made between the TRF quadratic excitation with a π phase profile and conventional EPI with a standard excitation in human subjects during ventral brain activation. Conclusion With reduced maximum phase distribution in the TRF pulse, signals in the susceptibility-affected areas, such as the orbitofrontal and inferior temporal cortex, were increased, suggesting that the technique could be a useful adjunct to fMRI. J. Magn. Reson. Imaging 2009;29:221-228. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

A Yorkshire terrier and a Chihuahua were referred for acute onset, generalized tonic-clonic seizures and were suspected to have meningoencephalitis based on magnetic resonance (MR) imaging findings. Brain lesions appeared hyperintense with T2-weighted imaging and hypointense with T1-weighted imaging, and were characteristic of necrotizing meningoencephalitis. Both dogs were diagnosed with necrotizing meningoencephalitis based on pathologic findings. Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) was performed on both animals before euthanasia with the permission of the owner. In FDG-PET images, these lesions seen in MR images were characterized by multifocal or diffuse hypometabolism. Our FDG-PET results provided evidence of glucose hypometabolism in areas of necrosis and cavitation associated with necrotizing meningoencephalitis. FDG-PET has the potential to provide valuable diagnostic information in dogs with suspected necrotizing encephalitis. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the feasibility of MR angiography (MRA) at 7.0 Tesla (T) using optimized birdcage (BC) coils with simple end cap configurations. Shielded 16-rung high-pass BC coils were built with identical geometry and compared with different sizes and locations of end caps. To determine whether the end cap configuration was effective, the signal intensity profiles along the superior-inferior (S-I) direction were analyzed in phantom and in vivo human experiments. The effects were also investigated in two-dimensional (2D) and three-dimensional (3D) time-of-flight (TOF) MRA experiments. The signal intensity profiles showed that B1 homogeneity at the service end, that is, the end cap side, was improved as the diameter of the end caps increased and the end cap became closer to the coil end ring. The results of 2D and 3D TOF experiments showed the best improvement of vessel visibility at the BC coil with an 80% end cap, when compared with BC coils with other end cap sizes or without an end cap. In conclusion, the BC coil with an end cap was effective for improving S-I directional homogeneity and suitable for MRA applications, especially at ultrahigh field MRI, such as 7.0T. Magn Reson Med 60:330-338, 2008. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Background: Many reports have suggested possible relationships between brain-derived neurotrophic factor (BDNF) and alcohol dependence. A protective effect of BDNF against ethanol-induced cell damage has been suggested, and this effect may contribute to the development or maintenance of alcohol dependence. This study was carried out in order to verify the significance of BDNF in alcohol dependence., Methods: Peripheral BDNF levels were measured in alcohol-dependent patients and control subjects using an enzyme-linked immunosorbent assay. A physician's interview and standardized questionnaire were used to obtain information regarding each patient's history of alcohol consumption., Results: The mean BDNF level was lower in the alcohol dependence group (389.5 +/- 501.7 pg/ml) than in the normal controls (822.5 +/- 420.7 pg/ml) by analysis of covariance (ANCOVA) (F = 25.79, p < 0.01). The mean BDNF level was lower in the alcohol-dependent patients with a positive family history of alcohol dependence (247.6 +/- 289.2 pg/ml) than in those with a negative family history of alcohol dependence (583.9 +/- 652.8 pg/ml) by ANCOVA (F = 6.51, p = 0.01). The BDNF levels did not correlate significantly with any of the variables analyzed in this study, including Beck depression inventory, state and trait anxiety inventory (STAI-S and T), and various drinking behaviors., Conclusions: Changes in the levels of BDNF might play a role in the pathophysiology and inheritance of alcohol dependence.