Magnetic Resonance in Medical Sciences
Online ISSN : 1880-2206
Print ISSN : 1347-3182
ISSN-L : 1347-3182
Volume 12, Issue 2
Displaying 1-10 of 10 articles from this issue
Major Papers
  • Hiroyuki MORISAKA, Utaroh MOTOSUGI, Tomoaki ICHIKAWA, Katsuhiro SANO, ...
    2013 Volume 12 Issue 2 Pages 77-86
    Published: 2013
    Released on J-STAGE: June 25, 2013
    Advance online publication: May 10, 2013
    JOURNAL OPEN ACCESS
    Objectives: We evaluated flow parameters measured by phase-contrast magnetic resonance (MR) imaging (PC-MRI) of the portal venous system and liver stiffness measured by MR elastography (MRE) to determine the usefulness of these methods in predicting gastroesophageal varices (GEV) in patients with chronic liver disease (CLD).
    Methods: In patients with CLD and controls, we performed PC-MRI on the portal (PV) and superior mesenteric veins; calculated mean velocity (V, cm/s), cross-sectional area (S, mm2), and flow volume (Q, mL/min); and determined markers of liver fibrosis (liver stiffness [kPa]) and aspartate aminotransferase (AST) platelet ratio index [APRI]). We visually assessed GEV and development of collateral pathways of the PV on routine contrast-enhanced dynamic MR imaging and compared patient characteristics, flow parameters, liver stiffness markers, and visual analysis among 3GEV groups, those with mild, severe, or no GEV with reference to endoscopic findings.
    Results: Child-Pugh grade, VPV, SPV, liver stiffness, APRI, and visually identified GEV (visible GEV) differed significantly among the 3 groups (P<0.05). We investigated VPV, SPV, liver stiffness, and visible GEV as independent markers to distinguish patients with and without GEV and examined VPV and visible GEV to predict severe GEV. Visible GEV showed low sensitivity (14 to 30%) and high specificity (98%) for predicting GEV in patients with CLD. A subgroup analysis that excluded cases with collateral pathway demonstrated slightly improved diagnostic performance of VPV and liver stiffness.
    Conclusions: Portal vein flow parameters and liver stiffness can be useful markers for predicting GEV in patients with CLD.
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  • Kazuhiro TSUCHIYA, Shigeki AOKI, Keigo SHIMOJI, Harushi MORI, Akira KU ...
    2013 Volume 12 Issue 2 Pages 87-93
    Published: 2013
    Released on J-STAGE: June 25, 2013
    Advance online publication: May 10, 2013
    JOURNAL OPEN ACCESS
    Purpose: Time-resolved contrast-enhanced magnetic resonance (MR) angiography (TCMRA) and perfusion MR imaging (PWI) have been used to assess the hemodynamics of brain tumors. We assessed the feasibility and value of consecutive performance of these techniques to evaluate suspected brain metastasis following supplementary injection of gadolinium-based contrast medium.
    Methods: In 69 patients with suspected brain metastasis, we obtained precontrast MR images followed by TCMRA and postcontrast T1-weighted images after administration of 0.1 mmol/kg gadoteridol. When findings were negative or equivocal, we injected an additional 0.1-mmol/kg dose of gadoteridol and obtained PWI and second postcontrast T1-weighted images. We used a 3-point scale to grade perfusion maps and TCMRA and assessed whether these techniques added information to conventional MR imaging in the differential diagnosis. We also evaluated whether the second contrast injection improved the conspicuity and/or number of enhancing lesions and used a 4-point scoring system to quantitatively analyze diagnostic yield of TCMRA and PWI.
    Results: We could assess tumor hemodynamics on PWI maps and TCMRA images in all 69 patients. In 14 cases (20%), PWI and/or TCMRA added information to conventional MR findings. After second injection of contrast medium, lesion conspicuity improved in 58 of the 69 cases (84%), and the number of detected lesions increased in 11 of 31 cases diagnosed with metastatic disease (36%). Quantitative analysis revealed TCMRA and PWI provided significant additional diagnostic information (Kruskal-Wallis test, P<0.0001).
    Conclusion: Consecutive acquisition of TCMRA and PWI using supplementary contrast injection can facilitate differential diagnosis of suspected brain metastasis and improve the number and conspicuity of detected lesions.
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  • Minoru MITSUDA, Masayuki YAMAGUCHI, Ryutaro NAKAGAMI, Toshihiro FURUTA ...
    2013 Volume 12 Issue 2 Pages 95-103
    Published: 2013
    Released on J-STAGE: June 25, 2013
    Advance online publication: May 10, 2013
    JOURNAL OPEN ACCESS
    Purpose: Simultaneous magnetic resonance (MR) imaging of multiple small animals in a single session increases throughput of preclinical imaging experiments. Such imaging using a 3-tesla clinical scanner with multi-array coil requires correction of intensity variation caused by the inhomogeneous sensitivity profile of the coil. We explored a method for correcting intensity that we customized for multi-animal MR imaging, especially abdominal imaging.
    Method: Our institutional committee for animal experimentation approved the protocol. We acquired high resolution T1-, T2-, and T2*-weighted images and low resolution proton density-weighted images (PDWIs) of 4 rat abdomens simultaneously using a 3T clinical scanner and custom-made multi-array coil. For comparison, we also acquired T1-, T2-, and T2*-weighted volume coil images in the same rats in 4 separate sessions. We used software created in-house to correct intensity variation. We applied thresholding to the PDWIs to produce binary images that displayed only a signal-producing area, calculated multi-array coil sensitivity maps by dividing low-pass filtered PDWIs by low-pass filtered binary images pixel by pixel, and divided uncorrected T1-, T2-, or T2*-weighted images by those maps to obtain intensity-corrected images. We compared tissue contrast among the liver, spinal canal, and muscle between intensity-corrected multi-array coil images and volume coil images.
    Results: Our intensity correction method performed well for all pulse sequences studied and corrected variation in original multi-array coil images without deteriorating the throughput of animal experiments. Tissue contrasts were comparable between intensity-corrected multi-array coil images and volume coil images.
    Conclusion: Our intensity correction method customized for multi-animal abdominal MR imaging using a 3T clinical scanner and dedicated multi-array coil could facilitate image interpretation.
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  • Reiko NAKAJIMA, Akira UCHINO, Naoko SAITO, Ryo NISHIKAWA
    2013 Volume 12 Issue 2 Pages 105-110
    Published: 2013
    Released on J-STAGE: June 25, 2013
    Advance online publication: May 10, 2013
    JOURNAL OPEN ACCESS
    Purpose: We evaluated the prevalence and imaging characteristics of ring-shaped lateral ventricular nodules (RSLVNs) detected by postcontrast brain magnetic resonance (MR) imaging.
    Materials and Methods: We retrospectively reviewed cranial MR images of 1,241 patients who underwent contrast-enhanced brain imaging between January 1, 2008 and March 31, 2011, excluded images of inadequate quality of 130 patients, and ultimately analyzed images of 1,111 patients (544 male, 567 female). We assessed location, shape, and signal intensity of RSLVNs on T1-weighted (T1WIs), T2-weighted (T2WIs), fluid-attenuated inversion recovery (FLAIR), and diffusion-weighted (DWIs) images and characteristics of contrast enhancement.
    Results: In 5 patients, we found 6 RSLVNs (0.45%), four in the frontal horn and two in the roof of the body. Three RSLVNs were round, two were oval, and one was lobular on axial images. All 6 RSLVNs were isointense with adjacent brain parenchyma on T1WI, T2WI, and DWI but slightly hyperintense on FLAIR images; none showed enhancement on postcontrast MR imaging. Five nodules serially examined (range, 8 to 24 months) showed no interval changes.
    Conclusions: Our MR imaging findings of a 0.45% prevalence of RSLVNs shows they are not so rare as previously reported. Except for configuration, all nodules had similar intensity, and none showed contrast enhancement. Absence of changes during the follow-up period seemed to indicate that the nodules have no clinical significance. However, their clear differentiation avoids unnecessary surgery.
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  • Masami YONEYAMA, Taro TAKAHARA, Thomas C. KWEE, Masanobu NAKAMURA, Tak ...
    2013 Volume 12 Issue 2 Pages 111-119
    Published: 2013
    Released on J-STAGE: June 25, 2013
    Advance online publication: May 10, 2013
    JOURNAL OPEN ACCESS
    Purpose: To introduce, optimize, and assess the feasibility of a new scheme to rapidly acquire high-resolution volumetric neurographic images using a three-dimensional turbo spin-echo sequence combined with a diffusion-weighted pre-pulse called improved motion-sensitized driven equilibrium (iMSDE): Diffusion-prepared MR Neurography (D-prep MRN).
    Methods: In order to optimize the signal suppression of blood vessels and muscle at D-prep MRN, coronal lumbosacral plexus images were acquired in five volunteers at 3T, and the following parameters were examined: iMSDE gradient-strength (b-value) of 0, 2 and 10 s/mm2 (with the aim to suppress blood vessels) and iMSDE preparation duration (iMSDEprep-time) of 18, 50 and 100 ms (with the aim to suppress muscle signal). Subsequently, the feasibility of the optimized D-prep MRN sequence in visualizing the brachial plexus, lumbosacral plexus, and cranial nerves was evaluated in 5 healthy volunteers.
    Results: A higher b-value of 10 s/mm2 was better in signal suppression of blood vessels, whereas an intermediate iMSDEprep-time of 50 ms provided the best compromise between suppression of muscle signal and minimization of signal loss of nerves. With these parameters, the normal nerve structures showed high signal intensity, while the blood vessels and muscles were effectively suppressed. The optimized D-prep MRN sequence clearly showed the three-dimensional trajectory of the brachial plexus, lumbosacral plexus, and cranial nerves.
    Conclusion: D-prep MRN was introduced and optimized, and clearly showed detailed anatomy of the brachial plexus, lumbosacral plexus, and cranial nerves. These results suggest that the D-prep MRN can be used for fast, high-resolution, volumetric imaging of the peripheral nervous system.
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  • Tomokazu MURASE, Masahiro UMEDA, Masaki FUKUNAGA, Chuzo TANAKA, Toshih ...
    2013 Volume 12 Issue 2 Pages 121-127
    Published: 2013
    Released on J-STAGE: June 25, 2013
    Advance online publication: May 10, 2013
    JOURNAL OPEN ACCESS
    We used deconvolution analysis to examine temporal changes in brain activity after acupuncture stimulation and assess brain responses without expected reference functions. We also examined temporal changes in brain activity after sham acupuncture (noninsertive) and scrubbing stimulation. We divided 26 healthy right-handed adults into a group of 13 who received real acupuncture with manual manipulation and a group of 13 who received both tactical stimulations. Functional magnetic resonance imaging (fMRI) sequences consisted of four 15-s stimulation blocks (ON) interspersed between one 30-s and four 45-s rest blocks (OFF) for a total scanning time of 270 s. We analyzed data by using Statistical Parametric Mapping 8 (SPM8), MarsBaR, and Analysis of Functional NeuroImages (AFNI) software. For statistical analysis, we used 3dDeconvolve, part of the AFNI package, to extract the impulse response functions (IRFs) of the fMRI signals on a voxel-wise basis, and we tested the time courses of the extracted IRFs for the stimulations. We found stimulus-specific impulse responses of blood oxygen level-dependent (BOLD) signals in various brain regions. We observed significantly delayed and long-sustained increases of BOLD signals in several brain regions following real acupuncture compared to sham acupuncture and palm scrubbing, which we attribute to peripheral nocireceptors, flare responses, and processing of the central nervous system. Acupuncture stimulation induced continued activity that was stronger than activity after the other stimulations.
    We used tent function deconvolution to process fMRI data for acupuncture stimulation and found delayed increasing and delayed decreasing changes in BOLD signal in the somatosensory areas and areas related to pain perception. Deconvolution analyses with tent functions are expected to be useful in extracting complicated and associated brain activity that is delayed and sustained for a long period after various stimulations.
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  • Itiro ANDO, Kazuhisa TAKEUCHI, Shiro OGUMA, Hiroshi SATO, Hiroshi SEKI ...
    2013 Volume 12 Issue 2 Pages 129-135
    Published: 2013
    Released on J-STAGE: June 25, 2013
    Advance online publication: May 10, 2013
    JOURNAL OPEN ACCESS
    We used 1H nuclear magnetic resonance (NMR) spectroscopy to assess metabolic responses in patients undergoing hemodialysis (HD). We collected 71 samples of plasma and dialysate from 10 patients before, during, and after HD. We used the dialysate as a possible substitute for blood plasma to quantify small metabolites by 1H NMR. We confirmed TSP (sodium 3-(trimethylsilyl) propionate 2, 2, 3, 3-d4) as a reference of NMR intensity in dialysate. We examined TSP sensitivities in various dialysate spectra and the correlation between signal intensities and added quantities of TSP. We used integrations of signal areas on 1H NMR spectra of plasma and dialysate to quantify concentrations of creatinine, lactate, alanine, and valine and calculate their ratios between plasma and dialysate. The ratios of metabolites in plasma to dialysate were 3.2±0.4 (creatinine), 3.6±0.5 (valine), 3.8±0.7 (alanine), and 4.0±0.8 (lactate) mM (mean±standard deviation [SD]). The broader distributions of ratios in levels of lactate and alanine suggested their de novo production during the HD session. Estimation of blood metabolite levels using dialysate is useful for quantitative analysis of metabolic status in blood during HD.
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