Magnetic Resonance in Medical Sciences
Online ISSN : 1880-2206
Print ISSN : 1347-3182
ISSN-L : 1347-3182
Advance online publication
Showing 1-39 articles out of 39 articles from Advance online publication
  • Manabu Arai, Taiki Nozaki, Masaki Matsusako, Yukari Zenke, Satoru Arai ...
    Article ID: cr.2019-0051
    Published: 2019
    [Advance publication] Released: July 11, 2019
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    Few studies had been published regarding imaging findings of skin adnexal tumors. We experienced two giant cases of them with a characteristic mushroom-like growth pattern. MRI showed a circumscribed mushroom-like shaped mass extruding from the subcutaneous tissue with microcystic lesions. Although differentiation between benignancy and malignancy may be difficult by radiological examinations, MRI may be helpful to identify its origin and differentiate soft tissue tumors with skin adnexal tumors in having these imaging findings.

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  • Junko Ochi, Naoko Mori, Yu Mori, Shunji Mugikura, Shin Hitachi, Eiji I ...
    Article ID: mp.2019-0026
    Published: 2019
    [Advance publication] Released: July 09, 2019
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    Purpose: To evaluate the feasibility of an empirical mathematical model (EMM) to fit dynamic contrast-enhanced MRI (DCE-MRI) data of hand and wrist synovitis and whether parameters of EMM are significantly correlated with clinical disease activity in patients with rheumatoid arthritis (RA).

    Methods: Thirty-one consecutive patients with RA prospectively underwent Institutional Review Board (IRB)-approved DCE-MRI scans with temporal resolution of 20 s using a 1.5T system. ROIs were placed where the highest signal increase was observed and the kinetic curves were analyzed using an EMM: ΔS(t) = A(1 − eα t) eβt, where ΔS is relative enhancement, t is time from when the signal increase was first observed, starting from baseline (ΔS = 0), A is the upper limit of signal intensity, α (s−1) is the rate of signal increase, and β (s−1) is the rate of signal decrease during washout. The initial slope of the kinetic curve (), the initial area under the curve (AUC30), the time at which the kinetic curve reached its peak (Tpeak) and the signal enhancement ratio (SER) defined as the change in signal intensity between the initial and delayed time points (t = 60 and 300 s, respectively) were calculated. RA magnetic resonance imaging scores (RAMRIS) with and without contrast media were evaluated. These parameters or scores were compared with the Disease Activity Score (DAS) 28-erythrocyte sedimentation rate (ESR).

    Results: A showed a significant correlation with DAS28-ESR (r = 0.58; P = 0.0005). β, AUC30 and Tpeak were also significantly correlated with DAS28-ESR with a lesser degree (r = 0.49; P = 0.0051, r = 0.50; P = 0.0038 and r = −0.51; P = 0.0028, respectively), whereas α, , SER and RAMRIS were not.

    Conclusion: EMM could fit the DCE-MRI data of hand and wrist synovitis. AUC30 obtained from the uptake phase of the kinetic curve as well as A, β and Tpeak obtained throughout the kinetic curve might be effective to predict the clinical disease activity.

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  • Yutaka Kato, Kazushige Ichikawa, Kuniyasu Okudaira, Toshiaki Taoka, Hi ...
    Article ID: mp.2019-0016
    Published: 2019
    [Advance publication] Released: June 20, 2019
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    Purpose: This study aimed to evaluate comprehensively; accuracy, repeatability and reproducibility of T1 and T2 relaxation times measured by magnetic resonance fingerprinting using B1+-corrected fast imaging with steady-state precession (FISP–MRF).

    Methods: The International Society of Magnetic Resonance in Medicine/National Institute of Standards and Technology (ISMRM/NIST) phantom was scanned for 100 days, and six healthy volunteers for 5 days using a FISP–MRF prototype sequence. Accuracy was evaluated on the phantom by comparing relaxation times measured by FISP–MRF with the reference values provided by the phantom manufacturer. Daily repeatability was characterized as the coefficient of variation (CV) of the measurements over 100 days for the phantom and over 5 days for volunteers. In addition, the cross-scanner reproducibility was evaluated in volunteers.

    Results: In the phantom study, T1 and T2 values from FISP–MRF showed a strong linear correlation with the reference values of the phantom (R2 = 0.9963 for T1; R2 = 0.9966 for T2). CVs were <1.0% for T1 values larger than 300 ms, and <3.0% for T2 values across a wide range. In the volunteer study, CVs for both T1 and T2 values were <5.0%, except for one subject. In addition, all T2 values estimated by FISP–MRF in vivo were lower than those measured with conventional mapping sequences reported in previous studies. The cross-scanner variation of T1 and T2 showed good agreement between two different scanners in the volunteers.

    Conclusion: B1+-corrected FISP-MRF showed an acceptable accuracy, repeatability and reproducibility in the phantom and volunteer studies.

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  • Shinji Naganawa, Toshiki Nakane, Hisashi Kawai, Toshiaki Taoka, Hiroka ...
    Article ID: mp.2019-0048
    Published: 2019
    [Advance publication] Released: June 20, 2019
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    Purpose: It has been reported that leakage of intravenously administered gadolinium-based contrast agents (IV-GBCAs) into the cerebrospinal fluid (CSF) from the cortical veins even in healthy subjects can be detected using a highly sensitive pulse sequence such as heavily T2-weighted 3D fluid-attenuated inversion recovery and 3D-real inversion recovery (IR). The purpose of this study was to evaluate the feasibility of MR fingerprinting to detect GBCA leakage from the cortical veins after IV-GBCA.

    Materials: Fourteen patients with suspected endolymphatic hydrops (EH) who received a single dose of IV-GBCA (39–79 years old) were included. The real IR images as well as MR fingerprinting images were obtained at 4 h after IV-GBCA. T1 and T2 values were obtained using MR fingerprinting and analyzed in ROIs covering intense GBCA leakage, and non-leakage areas of the CSF as determined on real IR images. The scan time for real IR imaging was 10 min and that for MR fingerprinting was 41 s.

    Results: The mean T1 value of the ROI in the area of GBCA leakage was 2422 ± 261 ms and that in the non-leakage area was 3851 ± 235 ms (P < 0.01). There was no overlap between the T1 values in the area of GBCA leakage and those in the non-leakage area.

    The mean T2 value in the area of GBCA leakage was 319 ± 90 ms and that in the non-leakage area was 670 ± 166 ms (P < 0.01). There was some overlap between the T2 values in the area of GBCA leakage and those in the non-leakage area.

    Conclusion: Leaked GBCA from the cortical veins into the surrounding CSF can be detected using MR fingerprinting obtained in <1 min.

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  • Ryoichi Kose, Katsumi Kose
    Article ID: tn.2018-0157
    Published: 2019
    [Advance publication] Released: June 20, 2019
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    This study proposes an accurate method for creating a dictionary for magnetic resonance fingerprinting (MRF) using a fast Bloch image simulator. An MRF sequence based on a fast imaging with steady precession sequence and a numerical phantom were used for dictionary generation. Cartesian and spiral readout gradients were used for the Bloch image simulation. The validity and usefulness of the method for accurate dictionary creation were demonstrated by MRF parameter maps obtained by pattern matching with the dictionaries generated by the proposed method.

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  • Genki Fukumoto, Mitsunori Kanagaki, Takeshi Ishimoto, Kazuya Kitazumi, ...
    Article ID: ci.2019-0033
    Published: 2019
    [Advance publication] Released: June 18, 2019
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  • Takayuki Sakai, Yasuchika Aoki, Atsuya Watanabe, Masami Yoneyama, Shig ...
    Article ID: tn.2019-0014
    Published: 2019
    [Advance publication] Released: June 13, 2019
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    We investigated the usefulness of diffusion tensor imaging using single-shot turbo spin-echo sequence (TSE–DTI) in detecting the responsible nerve root by multipoint measurements of fractional anisotropy (FA) values. Five patients with bilateral lumbar spinal stenosis showing unilateral neurological symptoms were examined using TSE–DTI. In the spinal canal, FA values in the symptomatic side were lower than those in the asymptomatic side. TSE–DTI using multipoint measurements of FA values can differentiate the responsible lumbar nerve root.

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  • Yohei Ikebe, Hideki Ishimaru, Hiroshi Imai, Kuniko Abe, Tsuyoshi Izumo ...
    Article ID: mp.2018-0077
    Published: 2019
    [Advance publication] Released: May 31, 2019
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    Purpose: Identifying plaque components such as intraplaque hemorrhage, lipid rich necrosis, and calcification is important to evaluate vulnerability of carotid atherosclerotic plaque; however, conventional vessel wall MR imaging may fail to discriminate plaque components. We aimed to evaluate the components of plaques using quantitative susceptibility mapping (QSM), a newly developed post-processing technique to provide voxel-based quantitative susceptibilities.

    Methods: Seven patients scheduled for carotid endarterectomy were enrolled. Magnitude and phase images of five-echo 3D fast low angle shot (FLASH) were obtained using a 3T MRI, and QSM was calculated from the phase images. Conventional carotid vessel wall images (black-blood T1-weighted images [T1WI], T2-weighted images [T2WI], proton-density weighted images [PDWI], and time-of-flight images [TOF]) were also obtained. Pathological findings including intraplaque hemorrhage, calcification, and lipid rich necrosis at the thickest plaque section were correlated with relative susceptibility values with respect to the sternocleidomastoid muscle on QSM. On conventional vessel wall images, the contrast–noise ratio (CNR) between the three components and sternocleidomastoid muscle was measured respectively. Wilcoxon signed-rank test analyses were performed to assess the relative susceptibility values and CNR.

    Results: Pathologically, lipid rich necrosis was proved in all of seven cases, and intraplaque hemorrhage in five of seven cases. Mean relative susceptibility value of hemorrhage was higher than lipid rich necrosis unexceptionally (P = 0.0313). There were no significant differences between CNR of hemorrhage and lipid rich necrosis on all sequences. In all six cases with plaque calcification, susceptibility value of calcification was significantly lower than lipid rich necrosis unexceptionally (P = 0.0156). There were significant differences between CNRs of lipid rich necrosis and calcification on T1WI, PDWI, TOF (P < 0.05).

    Conclusion: QSM of carotid plaque would provide a novel quantitative MRI contrast that enables reliable differentiation among intraplaque hemorrhage, lipid rich necrosis, and calcification, and be useful to identify vulnerable plaques.

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  • Yuji Iwadate, Atsushi Nozaki, Yoshinobu Nunokawa, Shigeo Okuda, Hiroyu ...
    Article ID: tn.2018-0168
    Published: 2019
    [Advance publication] Released: May 30, 2019
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    The silent navigator technique utilizes a non-selective excitation and an appropriate respiratory waveform generation method is necessary for an accurate motion detection. We compared three methods for silent navigator waveform generation. The profile generation method with coil selection (prof-selection) resulted in a high cross correlation with bellows signals and a large respiration amplitude. The prof-selection method should be used for silent navigator waveform generation.

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  • Gabriel E. Varela-Mattatall, Alexandra Koch, Rüdiger Stirnberg, Steren ...
    Article ID: mp.2019-0015
    Published: 2019
    [Advance publication] Released: May 10, 2019
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    Purpose: To compare different q-space reconstruction methods for undersampled diffusion spectrum imaging data.

    Materials and Methods: We compared the quality of three methods: Mean Apparent Propagator (MAP); Compressed Sensing using Identity (CSI) and Compressed Sensing using Dictionary (CSD) with simulated data and in vivo acquisitions. We used retrospective undersampling so that the fully sampled reconstruction could be used as ground truth. We used the normalized mean squared error (NMSE) and the Pearson’s correlation coefficient as reconstruction quality indices. Additionally, we evaluated two propagator-based diffusion indices: mean squared displacement and return to zero probability. We also did a visual analysis around the centrum semiovale.

    Results: All methods had reconstruction errors below 5% with low undersampling factors and with a wide range of noise levels. However, the CSD method had at least 1–2% lower NMSE than the other reconstruction methods at higher noise levels. MAP was the second-best method when using a sufficiently high number of q-space samples. MAP reconstruction showed better propagator-based diffusion indices for in vivo acquisitions. With undersampling factors greater than 4, MAP and CSI have noticeably more reconstruction error than CSD.

    Conclusion: Undersampled data were best reconstructed by means of CSD in simulations and in vivo. MAP was more accurate in the extraction of propagator-based indices, particularly for in vivo data.

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  • Yasuhiko Tachibana, Takayuki Obata, Jeff Kershaw, Hironao Sakaki, Taku ...
    Article ID: mp.2019-0021
    Published: 2019
    [Advance publication] Released: May 10, 2019
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    Purpose: A general problem of machine-learning algorithms based on the convolutional neural network (CNN) technique is that the reason for the output judgement is unclear. The purpose of this study was to introduce a strategy that may facilitate better understanding of how and why a specific judgement was made by the algorithm. The strategy is to preprocess the input image data in different ways to highlight the most important aspects of the images for reaching the output judgement.

    Materials and Methods: T2-weighted brain image series falling into two age-ranges were used. Classifying each series into one of the two age-ranges was the given task for the CNN model. The images from each series were preprocessed in five different ways to generate five different image sets: (1) subimages from the inner area of the brain, (2) subimages from the periphery of the brain, (3–5) subimages of brain parenchyma, gray matter area, and white matter area, respectively, extracted from the subimages of (2). The CNN model was trained and tested in five different ways using one of these image sets. The network architecture and all the parameters for training and testing remained unchanged.

    Results: The judgement accuracy achieved by training was different when the image set used for training was different. Some of the differences was statistically significant. The judgement accuracy decreased significantly when either extra-parenchymal or gray matter area was removed from the periphery of the brain (P < 0.05).

    Conclusion: The proposed strategy may help visualize what features of the images were important for the algorithm to reach correct judgement, helping humans to understand how and why a particular judgement was made by a CNN.

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  • Hisayoshi Araki, Takeshi Yoshizako, Rika Yoshida, Mitsunari Maruyama, ...
    Article ID: ici.2019-0028
    Published: 2019
    [Advance publication] Released: May 07, 2019
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  • Akitoshi Inoue, Norihisa Nitta, Shinichi Ota, Kai Takaki, Yugo Imai, S ...
    Article ID: mp.2019-0010
    Published: 2019
    [Advance publication] Released: May 07, 2019
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    Purpose: This study assessed the MRI findings of strangulated small bowel obstruction (SBO) and mesenteric venous occlusion (MVO) in a rabbit model using 3T MRI.

    Materials and Methods: Twenty rabbits were included in this study. The strangulated SBO and MVO models were generated via surgical procedures in nine rabbits, and sham surgery was performed in two rabbits. The success of generating the models was confirmed via angiographic, macroscopic, and microscopic findings after the surgical procedure. MRI was performed before and 30 min after inducing mesenteric ischemia. T1-weighted images (T1WIs), T2-weighted images (T2WIs), and fat-suppressed T2WIs (FS-T2WIs) were obtained using the BLADE technique, and fat-suppressed T1WIs (FS-T1WIs) were obtained. The signal intensities of the affected bowel before and after the surgical procedures were visually categorized as high, iso, and low intense compared with the findings for the normal bowel wall on all sequences. Bowel wall thickness was measured, and the signal intensity ratio (SI ratio) was calculated using the signal intensities of the bowel wall and psoas muscle.

    Results: Angiographic, macroscopic, and microscopic findings confirmed that all surgical procedures were successful. The ischemic bowel wall was thicker than the normal bowel. The bowel wall was thicker in the MVO model (3.17 ± 0.55 mm) than in the strangulated SBO model (2.26 ± 0.46 mm). The signal intensity and SI ratio of the bowel wall were significantly higher after the procedure than before the procedure on all sequences in both models. The mesentery adjacent to the ischemic bowel loop exhibited a high signal intensity in all animals on FS-T2WIs.

    Conclusion: Non-contrast MRI can be used to evaluate mesenteric ischemia caused by strangulated SBO and MVO. FS-T2WIs represented the best modality for depicting the high signal intensity in the bowel wall and mesentery caused by ischemia.

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  • Toshio Ohashi, Shinji Naganawa, Ai Takeuchi, Toshio Katagiri, Kayao Ku ...
    Article ID: mp.2019-0013
    Published: 2019
    [Advance publication] Released: May 07, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Purpose: Recently, the use of 3D real inversion recovery (3D-real IR) imaging has been proposed for the evaluation of endolymphatic hydrops (EH). This method shows similar contrast between the endolymphatic and perilymphatic spaces and surrounding bone compared with the hybrid of reversed image of positive endolymph signal and native image of perilymph signal multiplied with heavily T2-weighted MR cisternography (HYDROPS-Mi2) image. We measured the volume of the endolymphatic space using 3D-real IR and HYDROPS-Mi2 images, and compared the measurements obtained with both techniques.

    Methods: HYDROPS-Mi2 and 3D-real IR images were obtained for 30 ears from 15 patients with clinical suspicion of EH; imaging was performed 4 h after intravenous administration of a single dose of gadolinium-based contrast agent. We measured the volume of the endolymphatic space in the cochlea and vestibule by manually drawing the regions of interest. The correlation between endolymphatic volume determined from HYDROPS-Mi2 images and 3D-real IR images was calculated.

    Results: There was a strong positive linear correlation between the cochlear and vestibular endolymphatic volume determined from HYDROPS-Mi2 and 3D-real IR images. The Spearman’s rank correlation coefficient (ρ) between the measurements obtained with both images was 0.805 (P < 0.001) for the cochlea and 0.826 (P < 0.001) for the vestibule.

    Conclusion: The endolymphatic volume measured using 3D-real IR images strongly correlated with that measured using HYDROPS-Mi2 images. Thus, 3D-real IR imaging might be a suitable method for the measurement of endolymphatic volume.

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  • Shintaro Ichikawa, Utaroh Motosugi, Marie-Luise Kromrey, Daiki Tamada, ...
    Article ID: mp.2019-0030
    Published: 2019
    [Advance publication] Released: May 07, 2019
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    Purpose: Post-contrast liver magnetic resonance imaging is typically performed with breath-hold 3D gradient echo sequences. However, breath-holding for >10 s is difficult for some patients. In this study, we compared the quality of hepatobiliary phase (HBP) imaging without breath-holding using the prototype pulse sequences stack-of-stars liver acquisition with volume acceleration (LAVA) (LAVA Star) with or without navigator echoes (LAVA Starnavi+ and LAVA Starnavi−) and Cartesian LAVA with navigator echoes (Cartesian LAVAnavi+).

    Methods: Seventy-two patients were included in this single-center, retrospective, cross-sectional study. HBP imaging using the three LAVA sequences (Cartesian LAVAnavi+, LAVA Starnavi−, and LAVA Starnavi+) without breath-holding was performed for all patients using a 3T magnetic resonance system. Two independent radiologists qualitatively analyzed (overall image quality, liver edge sharpness, hepatic vein clarity, streak artifacts, and respiratory motion/pulsation artifacts) HBP images taken by the three sequences using a five-point scale. Quantitative evaluations were also performed by calculating the liver-to-spleen, -lesion, and -portal vein (PV) signal intensity ratios. The results were compared between the three sequences using the Friedman test.

    Results: LAVA Starnavi+ showed the best image quality and hepatic vein clarity (P < 0.0001). LAVA Starnavi− showed the lowest image quality (P < 0.0001–0.0106). LAVA Starnavi+ images showed fewer streak artifacts than LAVA Starnavi− images (P < 0.0001), while Cartesian LAVAnavi+ images showed no streak artifacts. Cartesian LAVAnavi+ images showed stronger respiratory motion/pulsation artifacts than the others (P < 0.0001). LAVA Starnavi− images showed the highest liver-to-spleen ratios (P < 0.0001–0.0005). Cartesian LAVAnavi+ images showed the lowest liver-to-lesion and -PV ratios (P < 0.0001–0.0108).

    Conclusion: In terms of image quality, the combination of stack-of-stars acquisition and navigator echoes is the best for HBP imaging without breath-holding.

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  • Daiki Tamada, Marie-Luise Kromrey, Shintaro Ichikawa, Hiroshi Onishi, ...
    Article ID: mp.2018-0156
    Published: 2019
    [Advance publication] Released: April 26, 2019
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    Purpose: To improve the quality of images obtained via dynamic contrast enhanced MRI (DCE-MRI), which contain motion artifacts and blurring using a deep learning approach.

    Materials and Methods: A multi-channel convolutional neural network-based method is proposed for reducing the motion artifacts and blurring caused by respiratory motion in images obtained via DCE-MRI of the liver. The training datasets for the neural network included images with and without respiration-induced motion artifacts or blurring, and the distortions were generated by simulating the phase error in k-space. Patient studies were conducted using a multi-phase T1-weighted spoiled gradient echo sequence for the liver, which contained breath-hold failures occurring during data acquisition. The trained network was applied to the acquired images to analyze the filtering performance, and the intensities and contrast ratios before and after denoising were compared via Bland–Altman plots.

    Results: The proposed network was found to be significantly reducing the magnitude of the artifacts and blurring induced by respiratory motion, and the contrast ratios of the images after processing via the network were consistent with those of the unprocessed images.

    Conclusion: A deep learning-based method for removing motion artifacts in images obtained via DCE-MRI of the liver was demonstrated and validated.

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  • Song Duan, Yurong Zhu, Feng Liu, Sherman Xuegang Xin
    Article ID: mp.2018-0167
    Published: 2019
    [Advance publication] Released: April 24, 2019
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    Purpose: Magnetic resonance electrical property tomography (MR EPT) is a technique for non-invasively obtaining the electric property (EP) distribution of biological tissues, with a promising potential for application in the early detection of tumors. However, the contrast capability (CC) of this technique has not been fully studied. This work aims to theoretically explore the CC for detecting the variation of EP values and the size of the imaging region.

    Methods: A simulation scheme was specifically designed to evaluate the CC of MR EPT. The simulation study has the advantage that the magnetic field can be accurately obtained. EP maps of the designed phantom embedded with target regions of designated various sizes and EPs were reconstructed using the homogeneous Helmholtz equation based on B1+ with different signal-to-noise ratios (SNRs). The CC was estimated by determining the smallest detectable EP contrast when the target region size was as large as the Laplacian kernel and the smallest detectable target region size when the EP contrast was the same as the difference between healthy and malignant tissues in the brain, based on the reconstructed EP maps.

    Results: Using noise free B1+, the smallest detectable contrastσ and contrastεr were 1% and 3%, respectively, and the smallest detectable target region size was 1 mesh unit (the base unit size used in the simulation) for conductivity and relative permittivity. The smallest detectable EP contrast and target region size were decreased as the B1+ SNR increased.

    Conclusion: The CC of MR EPT was related with the SNR of the magnetic field. A small EP contrast and size were necessary for detection at a high-SNR magnetic field. Obtaining a high-SNR magnetic field is important for improving the CC of MR EPT.

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  • Yang Qing, Wang Xiong, Huang Da-xiang, Zhu Juan, Wang Fei, Yu Yong-qia ...
    Article ID: mp.2018-0097
    Published: 2019
    [Advance publication] Released: April 05, 2019
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    Purpose: To investigate whether the genu of the corpus callosum is involved in patients with clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) type I.

    Methods: Twenty-three cases of clinically confirmed MERS I were analyzed retrospectively, and MRI features of the lesion were observed. The apparent diffusion coefficient (ADC) values of the same region of interests in lesions at the splenium and genu of the corpus callosum were measured before and after treatment (i.e., four groups), and the average ADC values were calculated. Paired t-tests were used to compare the ADC values of lesions in the splenium and genu before and after treatment. Independent sample t-tests were used to compare the values in the splenium and genu after treatment.

    Results: The mean ADC values of the splenium before and after treatment were 0.448 ± 0.124 and 0.790 ± 0.070 × 10−3 mm2/s, respectively, showing significant difference (P < 0.01). The mean ADC values in the genu before and after treatment were 0.783 ± 0.067 and 0.829 ± 0.070 × 10−3 mm2/s, respectively, also showing significant difference (P < 0.01). There was no significant difference in the ADC values between the splenium and genu after treatment (P > 0.05).

    Conclusion: The genu showed a slight restriction in diffusion in the acute stage of type I MERS. After treatment, this diffusion restriction diminished as it typically does in the splenium. Our results indicate that the pathology in MERS extends well beyond the visible lesions.

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  • Lydia Chougar, Akifumi Hagiwara, Nao Takano, Christina Andica, Julien ...
    Article ID: mp.2018-0144
    Published: 2019
    [Advance publication] Released: April 05, 2019
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    Purpose: Flowing blood sometimes appears bright on synthetic T1-weighted images, which could be misdiagnosed as a thrombus. This study aimed to investigate the frequency of hyperintensity within cerebral venous sinuses on synthetic MR images and to evaluate the influence of increasing flow rates on signal intensity using a flow phantom.

    Materials and Methods: Imaging data, including synthetic and conventional MRI scans, from 22 patients were retrospectively analyzed. Signal intensities at eight locations of cerebral venous sinuses on synthetic images were graded using the following three-point scale: 0, “dark vessel”; 1, “hyperintensity within the walls”; and 2, “hyperintensity within the lumen.” A phantom with gadolinium solution inside a U-shaped tube was acquired without flow and then with increasing flow rates (60, 100, 200, 300, 400 ml/min).

    Results: Considering all sinus locations, the venous signal intensity on synthetic T1-weighted images was graded as 2 in 79.8% of the patients. On synthetic T2-weighted images, all sinuses were graded as 0. On fluid-attenuated inversion recovery (FLAIR) images, sinuses were almost always graded as 0 (99.4%). In the phantom study, the signal initially became brighter on synthetic T1-weighted images as the flow rate increased. Above a certain flow rate, the signal started to decrease.

    Conclusion: High signal intensity within the cerebral venous sinuses is a frequent finding on synthetic T1-weighted images. This corresponds to the hyperintensity noted at certain flow rates in the phantom experiment.

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  • Hiroko Tomita, Shigeyoshi Soga, Yohsuke Suyama, Keiichi Ito, Tomohiko ...
    Article ID: mp.2018-0124
    Published: 2019
    [Advance publication] Released: March 26, 2019
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    Purpose: Prostate cancer management includes identification of clinically significant cancers that may require curative treatment. Statistical models based on gamma distribution can describe diffusion signal decay curves of prostate cancer. The purpose of this study was to evaluate the ability of parameters obtained with the gamma model in differentiating prostate cancers with different Gleason score values.

    Methods: This study included 155 patients with prostate cancer who underwent multiparametric magnetic resonance imaging prior to prostate biopsy (127 patients) or radical prostatectomy (28 patients) between January 2015 and June 2017; 159 foci of prostate cancer were included in our study. We compared cases scored as Gleason score (GS) 3 + 3 and GS ≥ 3 + 4, and analyzed cases scored as GS ≤ 3+ 4 and GS ≥ 4 + 3 based on the gamma model (Frac < 1.0, Frac < 0.8, Frac < 0.5, Frac < 0.3, and Frac > 3.0), and apparent diffusion coefficient (ADC).

    Results: Among 159 cancerous lesions in 155 patients, 13 (8.2%) were GS 3 + 3 prostate cancers, 51 (32.0%) were GS 3 + 4 prostate cancers, 30 (18.2%) were GS 4 + 3 cancers, and 65 (40.9%) were GS ≥ 4 + 4 cancers. Frac < 0.3, Frac < 0.5, Frac < 0.8, and Frac < 1.0 were significantly higher and ADC values were significantly lower in GS ≥ 4 + 3 cancers than in GS ≤ 3 + 4 cancers (P < 0.01, P < 0.01, P < 0.01, P = 0.01, and P < 0.01, respectively). With receiver operating characteristic (ROC) analysis, Frac < 0.3 and Frac < 0.5 had significantly greater area under the ROC curve for discriminating GS ≥ 4 + 3 cancers from GS ≤ 3 + 4 cancers than ADC (P = 0.03, P < 0.01, respectively).

    Conclusion: Frac < 0.3 and Frac < 0.5 showed higher diagnostic performance than ADC for differentiating GS ≥ 4 + 3 from GS ≤ 3 + 4 cancers. The gamma model may add additional value in discrimination of tumor grades.

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  • Shinichiro Seki, Yasuko Fujisawa, Masao Yui, Yuji Kishida, Hisanobu Ko ...
    Article ID: mp.2018-0158
    Published: 2019
    [Advance publication] Released: March 18, 2019
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    Purpose: To directly compare the utility for therapeutic outcome prediction of dynamic first-pass contrast-enhanced (CE)-perfusion area-detector computed tomography (ADCT), MR imaging assessed with the same mathematical method and 2-[fluorine-18]-fluoro-2-deoxy-d-glucose–positron emission tomography combined with CT (PET/CT) for non-small cell lung cancer (NSCLC) patients treated with chemoradiotherapy.

    Materials and Methods: Forty-three consecutive stage IIIB NSCLC patients, consisting of 25 males (mean age ± standard deviation: 66.6 ± 8.7 years) and 18 females (66.4 ± 8.2 years) underwent PET/CT, dynamic CE-perfusion ADCT and MR imaging, chemoradiotherapy, and follow-up examination. In each patient, total, pulmonary arterial, and systemic arterial perfusions were calculated from both perfusion data and SUVmax on PET/CT, assessed for each targeted lesion, and averaged to determine final values. Receiver operating characteristics analyses were performed to compare the utility for distinguishing responders from non-responders using Response Evaluation Criteria in Solid Tumor (RECIST) 1.1 criteria. Overall survival (OS) assessed with each index were compared between two groups by means of the Kaplan–Meier method followed by the log-rank test.

    Results: Area under the curve (Az) for total perfusion on ADCT was significantly larger than that of pulmonary arterial perfusion (P < 0.05). Az of total perfusion on MR imaging was significantly larger than that of pulmonary arterial perfusion (P < 0.05). Mean OS of responder and non-responder groups were significantly different for total and systemic arterial (P < 0.05) perfusion.

    Conclusion: Dynamic first-pass CE-perfusion ADCT and MR imaging as well as PET/CT are useful for early prediction of treatment response by NSCLC patients treated with chemoradiotherapy.

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  • Yuko Nakamura, Toru Higaki, Takashi Nishihara, Kuniaki Harada, Masahir ...
    Article ID: mp.2018-0174
    Published: 2019
    [Advance publication] Released: March 18, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Purpose: Hepatobiliary-phase (HBP) MRI with gadoxetic acid facilitates the differentiation between lesions with and without functional hepatocytes. Thus, high-quality HBP images are required for the detection and evaluation of hepatic lesions. However, the long scan time may increase artifacts due to intestinal peristalsis, resulting in the loss of diagnostic information. Pseudo-random acquisition order disperses artifacts into the background. The aim of this study was to investigate the clinical applicability of pseudo-random trajectory scanning for the suppression of motion artifacts on T1-weighted images including HBP.

    Methods: Our investigation included computer simulation, phantom experiments, and a clinical study. For computer simulation and phantom experiments a region of interest (ROI) was placed on the area with motion artifact and the standard deviation inside the ROI was measured as image noise. For clinical study we subjected 62 patients to gadoxetic acid-enhanced hepatobiliary-phase imaging with a circular- and a pseudo-random trajectory (c-HBP and p-HBP); two radiologists graded the motion artifacts, sharpness of the liver edge, visibility of intrahepatic vessels, and overall image quality using a five-point scale where 1 = unacceptable and 5 = excellent. Differences in the qualitative scores were determined using the two-sided Wilcoxon signed-rank test.

    Results: The image noise was higher on the circular image compared with pseudo-random image (101.0 vs 60.9 on computer simulation image, 91.2 vs 67.7 on axial, 95.5 vs 86.9 on reformatted sagittal image for phantom experiments). For clinical study the score for motion artifacts was significantly higher with p-HBP than c-HBP imaging (left lobe: mean 3.4 vs 3.2, P < 0.01; right lobe: mean 3.6 vs 3.4, P < 0.01) as was the qualitative score for the overall image quality (mean 3.6 vs 3.3, P < 0.01).

    Conclusion: At gadoxetic acid-enhanced hepatobiliary-phase imaging, p-HBP scanning suppressed motion artifacts and yielded better image quality than c-HBP scanning.

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  • Kosuke Morita, Takeshi Nakaura, Natsuki Maruyama, Yuji Iyama, Seitaro ...
    Article ID: mp.2018-0132
    Published: 2019
    [Advance publication] Released: March 15, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Purpose: The hybrid compressed sensing (hybrid-CS) technique can shorten the acquisition time compared with the sensitivity encoding (SENSE) technique in lumbar MRI. To evaluate the feasibility of a hybrid-CS technique in comparison with 3D isotropic T2-weighted turbo spin-echo (3D volume isotropic turbo spin-echo acquisition [VISTA]) MRI of the lumbar spine.

    Materials and Methods: The Institutional Review Board approved this study and informed consent was obtained from participants prior to study entry. Sixteen healthy volunteers underwent lumbar spine 3D VISTA with conventional parallel imaging for SENSE and hybrid-CS at 3T. We recorded the image acquisition times of SENSE and hybrid-CS. We compared the signal-to-noise ratio (SNR) in spine, cerebrospinal fluid (CSF), lumbar disc, epidural fat, and erector spinae muscle, and the contrast of spine, CSF, and disc, and performed qualitative image analysis assessment, between the two image sequences.

    Results: The image acquisition time for hybrid-CS was 39.2% shorter than that of SENSE (218.4/358.8 s). The contrast of CSF and SNR of the spine was significantly higher with hybrid-CS than with SENSE (P < 0.05). The SNR of the disc and muscle was significantly higher with SENSE than with hybrid-CS (P < 0.05). There were no significant differences in the contrast of spine, disc, and fat, and SNR of CSF and fat between hybrid-CS and SENSE. There were no significant differences in the qualitative evaluation between hybrid-CS and SENSE.

    Conclusion: Compared with SENSE, hybrid-CS for 3D VISTA can shorten image acquisition time without sacrificing image quality.

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  • Kazuki Matsushita, Taro Shimono, Yukio Miki
    Article ID: ci.2018-0152
    Published: 2019
    [Advance publication] Released: March 04, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
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  • Tomoya Watanabe, Haruo Isoda, Atushi Fukuyama, Mamoru Takahashi, Tomoy ...
    Article ID: mp.2018-0063
    Published: 2019
    [Advance publication] Released: March 04, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Purpose: The accuracy of flow velocity and three-directional velocity components are important for the precise visualization of hemodynamics by 3D cine phase-contrast MRI (3D cine PC MRI, also referred to as 4D-flow). The aim of this study was to verify the accuracy of these measurements of prototype or commercially available 3D cine PC MRI obtained by three different manufactures’ MR scanners.

    Methods: The verification of the accuracy of flow velocity in 3D cine PC MRI was performed by circulating blood mimicking fluid through a straight-tube phantom in a slanting position, such that the three-directional velocity components were simultaneously measurable, using three 3T MR scanners from different manufacturers. The data obtained were processed by phase correction, and the velocity and three-directional velocity components in the center of the tube on the central cross section of a slab were calculated. The velocity profile in each three directions and the composite velocity profiles were compared with the calculated reference values, using the Hagen–Poiseuille equation. In addition, velocity profiles and the spatially time-averaged velocity perpendicular to the tube were compared with the theoretical values and measured values by a flowmeter, respectively.

    Results: An underestimation of the maximum velocity in the center of the tube and an overestimation of the velocity near the tube wall due to partial volume effects were observed in all three scanners. A roughening and flattening of profiles in the center of the tube were observed in one scanner, due, presumably, to the low signal-to-noise ratio. However, the spatially time-averaged velocities corresponded well with the measured values by the flowmeter in all three scanners.

    Conclusion: In this study, we have demonstrated that the accuracy of flow velocity and three-directional velocity components in 3D cine PC MRI was satisfactory in all three MR scanners.

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  • Hirohito Kan, Nobuyuki Arai, Masahiro Takizawa, Harumasa Kasai, Hirosh ...
    Article ID: tn.2018-0066
    Published: 2019
    [Advance publication] Released: February 25, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    To mitigate the susceptibility inhomogeneity induced by radio-frequency transmit phase error through the whole brain in quantitative susceptibility mapping (QSM) using single-echo gradient echo sequence, we developed a novel single-step QSM reconstruction algorithm and compared it with a previous algorithm in five healthy volunteers. The proposed algorithm had effectively suppressed the susceptibility inhomogeneity through the whole brain and achieved acceptable quality, similar to that of the susceptibility map calculated from a multi-echo gradient echo sequence.

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  • Shohei Fujita, Misaki Nakazawa, Akifumi Hagiwara, Ryo Ueda, Moeko Hori ...
    Article ID: mp.2018-0119
    Published: 2019
    [Advance publication] Released: February 19, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Purpose: Gadolinium-based contrast agents (GBCA) provide valuable information for assessing and differentiating lesions in the body. However, contrast enhancement evaluation on conventional MRI is qualitative because the signal intensity uses an arbitrary scale. An approach that allows more quantitative assessment of tissue enhancement that can be integrated into clinical use is desirable. This study aimed to provide a method that can estimate GBCA concentration in a clinically applicable scan-time.

    Methods: Gadolinium-based contrast agent concentrations were quantified in phantoms containing water and nine different concentrations of Gadoteridol (Gd-HP-DO3A), ranging from 0.02 to 1.00 mmol/L, using quantitative synthetic MRI. Simple linear regression analysis between the estimated GBCA concentration and the reference values were performed to assess the accuracy. We performed region of interest analysis on each phantom, and recorded the mean and standard deviation. We evaluated the precision of the GBCA map by calculating the coefficient of variation (CV) for each concentration. The GBCA concentration quantification method was applied for 10 patients with metastatic brain tumors to demonstrate the feasibility of this method.

    Results: For the phantom study, estimated GBCA concentrations were in a strong linear relationship (R2 = 0.998) with reference values, with a slope and intercept on simple linear regression analysis of 0.98 and 0.02, respectively. On precision assessment, the CV was <5%, with the exception of concentrations under 0.07 mmol/L. In the range of 0.07–0.99 mmol/L, the mean CV was 1.5 ± 1.2%. For application to brain metastases, the maximum estimated GBCA concentration in the metastases was 0.73 mmol/L, which was under the upper limit evaluated in the phantom study (i.e. −0.99 mmol/L).

    Conclusion: The concentration of Gd-HP-DO3A in the range of 0.07–0.99 mmol/L can be measured in a clinically applicable scan time using quantitative synthetic MRI, even though this study’s results are only preliminary due to several limitations.

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  • Yasuhiro Fujiwara, Hitoshi Fujioka, Maiko Sekiguchi, Haruna Tanaka, To ...
    Article ID: tn.2018-0100
    Published: 2019
    [Advance publication] Released: February 19, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    The purpose of this study was to develop a searchable system to confirm magnetic resonance (MR) safety information of implantable medical devices (IMDs) to safely perform magnetic resonance imaging examinations. We labeled MR safety information for IMDs based on package insert descriptions and then categorized allowed MR conditions for IMDs. Finally, a searchable system was developed to use the database via the internet. This system enables efficient and accurate confirmation of MR safety information for IMDs.

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  • Hiroki Kato, Kae Esaki, Takahiro Yamaguchi, Hidekazu Tanaka, Kimihiro ...
    Article ID: tn.2018-0138
    Published: 2019
    [Advance publication] Released: February 19, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    To assess if intravoxel incoherent motion (IVIM) imaging can be used to predict early response to chemoradiotherapy (CRT) in cervical cancer. IVIM imaging before and during CRT (at doses of 20 and 40 Gy) was performed in 17 patients with cervical squamous cell carcinoma. The percentage changes of IVIM parameters were significantly higher for complete remission (CR) than non-CR groups. IVIM may play a supplementary role for predicting early response to CRT in cervical cancer.

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  • Tsutomu Tamada, Yoshiyuki Miyaji, Naoki Kanomata, Ayumu Kido, Akira Ya ...
    Article ID: bc.2018-0154
    Published: 2019
    [Advance publication] Released: February 08, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
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  • Yawara Haga, Junichi Hata, Akiko Uematsu, Fumiko Seki, Yuji Komaki, Ma ...
    Article ID: mp.2018-0086
    Published: 2019
    [Advance publication] Released: February 07, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Purpose: Ex vivo brains have different MRI properties than in vivo brains because of chemical changes caused by fixative solutions, which change the signal intensity and/or tissue contrast on MR images. In this study, we investigated and compared the MRI properties of in vivo and ex vivo brains.

    Methods: Using a Bruker 9.4T experimental scanner unit for animals (Biospin GmbH, Ettlingen, Germany), we performed this study on the common marmoset. We measured the relaxation and diffusion values in the white matter and cortex of common marmosets and compared these values between in vivo brains (n = 20) and ex vivo brains (n = 20). Additionally, we observed the relationship between the tissue fixation duration and MRI properties by imaging a brain that underwent long-term fixation in a preliminary examination (n = 1).

    Results: The T1 values of ex vivo brains were decreased compared with those of in vivo brains; however, there were no significant difference in the T2 and T2* values of in vivo and ex vivo brains. Axial, radial, and mean diffusivity values of ex vivo brains decreased to approximately 65% and 52% of those of in vivo brains in the cortex and white matter, respectively. Conversely, fractional anisotropy values were not significantly different between in vivo and ex vivo brains.

    Conclusion: The T1 values and diffusion coefficient values of the ex vivo brains were strikingly different than those of the in vivo brains. Conversely, there were no significant changes in the T2, T2* or fractional anisotropy values. Altogether, the dehydration caused by tissue fixation and the reduction in brain temperature were involved in changing the relaxation and diffusion coefficient values. Here, it was difficult to specify all factors causing these changes. Further detailed study is needed to examine changes in MRI properties.

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  • Ajaykumar C. Morani, Ahmad Iyad Mubarak, Hrishabh R. Bhosale, Nisha S. ...
    Article ID: ci.2018-0104
    Published: 2019
    [Advance publication] Released: January 31, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
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  • Barış Polat, Deniz Aydın, Ayşe Esin Polat, Tahsin Gürpınar, Ramadan Öz ...
    Article ID: mp.2018-0094
    Published: 2019
    [Advance publication] Released: January 31, 2019
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Purpose: The aim of this study is to determine the prevalence of pathologic findings in asymptomatic knees of Kangoo Jumpers by using a 3T MRI and to compare them with age and sex-matched controls who do not regularly participate in any impact sports.

    Methods: Both knees of 18 Kangoo Jumpers were examined by 3T MRIs in a total of 36 MRI scans. The control group was comprised of 20 volunteers from the same age group and with similar weights who did not participate in any competitive sports, in a total of 40 MRI scans. Two orthopedists and one radiologist independently assessed all images for the presence or absence of any abnormalities.

    Results: In 32 (88.9%) of the 36 Kangoo Jumpers’ knees, one or more abnormalities were observed. The most prevalent abnormality was bone marrow edema, which was detected in 32 knees (88.9%). The other significant findings were quadriceps tendinopathy (80.6%), patellar tendinopathy (63.9%), gastrocnemius tendinopathy (63.9%), infrapatellar fat pad edema (75%), suprapatellar fat pad edema (63.9%), meniscal signal change (72.2%) and cartilage damage in the patellofemoral joint (72.2%). There were no statistically significant differences in terms of joint effusion (8.3%), ganglion cysts (8.3%) or tibiofemoral joint cartilage injury (0%).

    Conclusion: This study reveals many types of knee MRI findings of asymptomatic Kangoo Jumpers compared to the control group. These MRI findings may be associated with acute knee injuries or chronic joint problems such as osteoarthritis, which may develop in long-term follow-up studies.

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  • Shoko Hara, Masaaki Hori, Motoki Inaji, Taketoshi Maehara, Shigeki Aok ...
    Article ID: ci.2018-0088
    Published: 2018
    [Advance publication] Released: December 06, 2018
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
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  • Ömer Kasalak, Albert J.H. Suurmeijer, Jacco J. De Haan, Hugo J.A. Adam ...
    Article ID: ci.2018-0122
    Published: 2018
    [Advance publication] Released: December 06, 2018
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
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  • Kumiko Nozawa, Tetsu Niwa, Noriko Aida
    Article ID: bc.2018-0080
    Published: 2018
    [Advance publication] Released: December 03, 2018
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
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  • Jun Haneda, Akifumi Hagiwara, Masaaki Hori, Akihiko Wada, Issei Fukuna ...
    Article ID: tn.2018-0095
    Published: 2018
    [Advance publication] Released: December 03, 2018
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    The purpose of this study was to show the efficacy of dynamic field correction (DFC), a technique provided by the scanner software, in comparison to the FMRIB Software Library (FSL) post-processing “eddy” tool. DFC requires minimal additional scan time for the correction of eddy-current and motion-induced geometrical image distortions in diffusion-weighted echo-planar images. The fractional anisotropy derived from images corrected with DFC were comparable to images corrected with the “eddy” tool and significantly higher than images without correction, which demonstrates the utility of DFC.

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  • Akitoshi Inoue, Hiroo Mizuta, Akihiko Ito, Tomoyuki Tsujikawa, Akira F ...
    Article ID: ci.2018-0060
    Published: 2018
    [Advance publication] Released: November 06, 2018
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
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  • Shinya Fujii, Masaki Tsuda, Naoko Mukuda, Kanae Nosaka, Shinya Sato, T ...
    Article ID: ci.2018-0017
    Published: 2018
    [Advance publication] Released: November 02, 2018
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
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