Norihide Maikusa

National Center of Neurology and Psychiatry, Edo, Tōkyō, Japan

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Publications (10)18.12 Total impact

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    ABSTRACT: BACKGROUND AND PURPOSEAmygdala enlargement (AE) has been reported as an epileptogenic focus in subtypes of temporal lobe epilepsy (TLE). The purpose of this study was to investigate the clinical, morphological, and pathological characteristics of AE. METHODS We retrospectively reviewed the clinical data and imaging findings of 23 TLE patients with ipsilateral AE. We performed morphological MR analyses using FreeSurfer and voxel-based morphometry (VBM) in 14 of the 23 patients and in 20 controls whose images were obtained by a 3.0-Tesla MRI. A pathological study was also performed in 2 patients who underwent operations. RESULTSAll patients became seizure free or shSowed dramatic improvement by medical therapy except for two. They received operations and their pathology revealed that both patients had cortical dysplasia in from the amygdala to the ipsilateral temporal pole. The FreeSurfer analysis showed a significant difference in the amygdala volumes between the affected and nonaffected sides. VBM revealed significant increases of gray matter volumes of the temporal pole on the side of AE in seven of the 14 patients with AE (50%). CONCLUSIONS Cortical dysplasia may be one of the pathological diagnoses in AE, and in some patients it may extend to the temporal pole.
    Journal of neuroimaging: official journal of the American Society of Neuroimaging 02/2014; · 3.36 Impact Factor
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    ABSTRACT: Arterial spin labeling (ASL) magnetic resonance imaging (MRI) is a novel noninvasive technique that can measure regional cerebral blood flow (rCBF). To our knowledge, few studies have examined rCBF in patients with schizophrenia by ASL-MRI. Here we used pseudo-continuous ASL (pCASL) to examine the structural and functional imaging data in schizophrenic patients, taking the regional cerebral gray matter volume into account. The subjects were 36 patients with schizophrenia and 42 healthy volunteers who underwent 3-tesla MRI, diffusion tensor imaging (DTI), and pCASL. We evaluated the gray matter volume imaging, DTI, and pCASL imaging data in a voxel-by-voxel statistical analysis. The schizophrenia patients showed reduced rCBF in the left prefrontal and bilateral occipital cortices compared to the healthy volunteers. There was a significant reduction of gray matter volume in the left inferior frontal cortex in the schizophrenia patients. With respect to the fractional anisotropy (FA) values in the DTI, there were significant FA reductions in the left superior temporal, left external capsule, and left inferior prefrontal regions in the patients compared to the controls. Conclusion Our pCASL study with partial volume effect correction together with volumetry and DTI data demonstrated hypoactivity in the left prefrontal area beyond structural abnormalities in schizophrenia patients. There were also hypofunction areas in bilateral occipital cortices, although structural abnormalities were not apparent.
    Schizophrenia Research 01/2014; · 4.59 Impact Factor
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    Dataset: JADNI
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    ABSTRACT: Purpose: Serial magnetic resonance imaging (MRI) images acquired from multisite and multivendor MRI scanners are widely used in measuring longitudinal structural changes in the brain. Precise and accurate measurements are important in understanding the natural progression of neurodegenerative disorders such as Alzheimer's disease. However, geometric distortions in MRI images decrease the accuracy and precision of volumetric or morphometric measurements. To solve this problem, the authors suggest a commercially available phantom-based distortion correction method that accommodates the variation in geometric distortion within MRI images obtained with multivendor MRI scanners.Methods: The authors' method is based on image warping using a polynomial function. The method detects fiducial points within a phantom image using phantom analysis software developed by the Mayo Clinic and calculates warping functions for distortion correction. To quantify the effectiveness of the authors' method, the authors corrected phantom images obtained from multivendor MRI scanners and calculated the root-mean-square (RMS) of fiducial errors and the circularity ratio as evaluation values. The authors also compared the performance of the authors' method with that of a distortion correction method based on a spherical harmonics description of the generic gradient design parameters. Moreover, the authors evaluated whether this correction improves the test-retest reproducibility of voxel-based morphometry in human studies.Results: A Wilcoxon signed-rank test with uncorrected and corrected images was performed. The root-mean-square errors and circularity ratios for all slices significantly improved (p < 0.0001) after the authors' distortion correction. Additionally, the authors' method was significantly better than a distortion correction method based on a description of spherical harmonics in improving the distortion of root-mean-square errors (p < 0.001 and 0.0337, respectively). Moreover, the authors' method reduced the RMS error arising from gradient nonlinearity more than gradwarp methods. In human studies, the coefficient of variation of voxel-based morphometry analysis of the whole brain improved significantly from 3.46% to 2.70% after distortion correction of the whole gray matter using the authors' method (Wilcoxon signed-rank test, p < 0.05).Conclusions: The authors proposed a phantom-based distortion correction method to improve reproducibility in longitudinal structural brain analysis using multivendor MRI. The authors evaluated the authors' method for phantom images in terms of two geometrical values and for human images in terms of test-retest reproducibility. The results showed that distortion was corrected significantly using the authors' method. In human studies, the reproducibility of voxel-based morphometry analysis for the whole gray matter significantly improved after distortion correction using the authors' method.
    Medical Physics 06/2013; 40(6):062303. · 2.91 Impact Factor
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    ABSTRACT: Arterial spin labeling (ASL) is a noninvasive technique that can measure cerebral blood flow (CBF). To our knowledge, there is no study that examined regional CBF of multiple sclerosis (MS) patients by using this technique. The present study assessed the relationship between clinical presentations and functional imaging data in MS using pseudocontinuous arterial spin labeling (pCASL). Twenty-seven patients with MS and 24 healthy volunteers underwent magnetic resonance imaging and pCASL to assess CBF. Differences in CBF between the two groups and the relationships of CBF values with the T2-hyperintense volume were evaluated. Compared to the healthy volunteers, reduced CBF was found in the bilateral thalami and right frontal region of the MS patients. The volume of the T2-hyperintense lesion was negatively correlated with regional CBF in some areas, such as both thalami. Our results suggest that demyelinated lesions in MS mainly have a remote effect on the thalamus and that the measurement of CBF using ASL could be an objective marker for monitoring disease activity in MS.
    Magnetic Resonance Imaging 04/2013; · 2.06 Impact Factor
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    ABSTRACT: In multiple system atrophy with predominant parkinsonism (MSA-P), several voxel-based morphometry (VBM) studies have revealed gray matter loss; however, the white matter volume changes have been rarely reported. We investigated the volume changes of white matter as well as gray matter by VBM. A retrospective MRI study was performed in 20 patients with MSA-P and 30 age-matched healthy controls. We applied VBM with statistical parametric mapping (SPM8) plus diffeomorphic anatomical registration through exponentiated Lie algebra (DARTEL) to explore the regional atrophy of gray and white matter in all of the MSA-P patients, 14 patients with left-side dominant and 6 patients with right-side dominant onset as compared to controls. In all of the MSA-P patients, VBM revealed a significant volume reduction of gray matter in the bilateral putamina, cerebellums and dorsal midbrain. White matter loss was located in bilateral globus pallidi, external capsules extending to the midbrain, right subcortical to precentral area through internal capsule, the pons, bilateral middle cerebellar peduncles and left cerebellum. In left-side dominant MSA-P patients, the gray and white matter volume loss was detected predominantly on the right side and vice versa in right-side dominant MSA-P patients. A correlation with disease duration and severity was not detected. VBM using SPM8 plus DARTEL detected significant volume loss not only in the gray but also in the white matter of the area affected by MSA-P.
    NeuroImage : clinical. 01/2013; 2:491-6.
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    ABSTRACT: We demonstrated a depth-resolved 3D imaging technique based on absorption contrast using tomosynthesis. Tomosynthesis is similar to computed tomography except that the number of projections is much smaller. We constructed a tomosynthesis imaging system, which detects a transmitted continuous THz wave. We applied a backprojection method that was suitable for the constructed detection configuration, to reconstruct an image. Using this system, we imaged a test sample made from paper and reproduced characters written by pencil.
    Optics Express 07/2009; 17(12):9558-70. · 3.55 Impact Factor
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    ABSTRACT: The second harmonic and subharmonic components, the frequencies of which are twice and one half the fundamental frequency, are included in echoes from contrast agents. An imaging method, which employs a second harmonic (second harmonic imaging), is widely used in medical diagnoses. On the other hand, subharmonic is expected to provide a higher contrast between biological tissues and blood flow because echo signals are generated only from blood containing the contrast agents. However, the subharmonic component echo signal power from contrast agents is relatively low. This has resulted in little progress in the field of subharmonic imaging. In this study, a new imaging method is proposed using amplitude-modulated waves as transmitted waves combined with the pulse inversion method to enhance subharmonic echo signals. Two optimal frequencies are set, including the modulated waves, F(1) and F(2), so that the subharmonic frequency of F(1) and the second harmonic frequency of F(2) may result in the same value. This allows a more powerful signal at the frequency band because the second harmonic and subharmonic components are integrated. Furthermore, a B-mode ultrasound image of an agar phantom that imitated biological tissue and showed the effectiveness of our method was reconstructed. As a result, the echo power of the subharmonic component was enhanced by approximately 11.8 dB more than the conventional method and the signal to noise ratio showed an improvement of 7.6 dB.
    The Journal of the Acoustical Society of America 08/2007; 122(1):672-6. · 1.65 Impact Factor
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    ABSTRACT: It is known that the second harmonic and subharmonic components, the frequencies of which are twice and one half the fundamental frequency, are included in echoes from contrast agents. An imaging method, which employs a second harmonic is widely used in medical diagnosis. On the other hand, subharmonic are expected to provide a higher contrast between biological tissues and blood flow because echo signals are generated only from blood containing the contrast agents. However, the subharmonic component echo signal power from contrast agents is relatively low. This has resulted in little progress in the field of subharmonic imaging. In this study, we proposed a new imaging method using amplitude-modulated waves as transmitted waves combined with the pulse inversion method to enhance subharmonic echo signals. Furthermore, we reconstructed a B-mode ultrasound image of agar phantom imitated biological tissue and showed the effectiveness of our method. As a result, the proposed method was found to improve the subharmonic echo power compared with the conventional imaging method
    Proceedings of the IEEE Ultrasonics Symposium 01/2006;
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    ABSTRACT: Harmonic imaging is a prosperous technique to obtain a high quality ultrasonic image using harmonics in echoes from microbubbles, i.e., the collapse of microbubbles and subsequent harmonic emission are used for some imaging techniques, such as flash echo imaging. The mechanism of subharmonic generation is not figured out enough however it is considered that there are some relationships between the resonance and collapse of microbubble. On the other hand, subharmonic in echoes from microbubbles is expected to obtain higher contrast between tissue and blood flow than conventional harmonic imaging because it can be hardly detected from tissue. We observed echo signals and images of microbubbles through a microscope simultaneously and investigated the relationship between time-variation of each harmonics component and bubble's behavior. Our results showed clear inverse correlation between decrease of number of bubbles and subharmonic generation.
    IEEJ Transactions on Electronics Information and Systems 01/2005; 125(11):1699-1706.