Magnetic Resonance in Medical Sciences
Online ISSN : 1880-2206
Print ISSN : 1347-3182
Volume 16 , Issue 3
Showing 1-14 articles out of 14 articles from the selected issue
Clinical Image
Review
  • Yasuo Amano, Fumi Yanagisawa, Masaki Tachi, Kuniya Asai, Yasuyuki Suzu ...
    2017 Volume 16 Issue 3 Pages 183-189
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: February 16, 2017
    JOURNALS OPEN ACCESS

    Three-dimensional (3D) cardiac magnetic resonance (MR) imaging has several advantages, including the easy coverage of the entire heart without misregistration, reduction of breath-holding times, and availability for postprocessing reconstruction. These advantages are associated with some techniques such as breath-hold or navigator gating and parallel imaging. However, the image quality of 3D cardiac MR images is compromised by the use of a shorter repetition time and parallel imaging. Thus, a steady-state free precession sequence, contrast agent administration, and presaturation pulses are used to maintain the image quality. In this review, we introduce the MR imaging techniques used in 3D cardiac MR imaging and demonstrate the typical 3D cardiac MR images, followed by discussion about their advantages and disadvantages.

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Major Papers
  • Koung Mi Kang, Seung Hong Choi, Dong Eun Kim, Tae Jin Yun, Ji-hoon Kim ...
    2017 Volume 16 Issue 3 Pages 190-202
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: November 04, 2016
    JOURNALS OPEN ACCESS

    Purpose: To prospectively evaluate whether cardiac gating can improve the reproducibility of intravoxel incoherent motion (IVIM) parameters in the head and neck, we performed IVIM diffusion-weighted imaging (DWI) using 4 b values (4b), 4 b values with cardiac gating (4b gating) and 17 b values (17b).

    Methods: We performed IVIM DWI twice per person on nine healthy volunteers using 4b, 4b gating and 17b and five patients with head and neck masses using 4b gating and 17b. The ADC, perfusion fraction (f), diffusion coefficient (D) and perfusion-related diffusion coefficient (D*) were calculated in the brain, masticator muscle, parotid gland, submandibular gland, tonsil and masses. Intraclass coefficient (ICC), Bland-Altman analysis (BAA) and coefficient of variation (CV) were used to assess short-term test-retest reproducibility. Kruskal-Wallis test and Mann-Whitney test were used to investigate whether 4b, 4b gating or 17b had significant influences on the parameters.

    Results: For normal tissues and masses, ICC was excellent for all maps except the D* map. All parameters showed the lowest CV in the 4b gating. BAA also revealed the narrowest 95% limits of agreement using 4b gating for all parameters. In the subgroup analysis, almost all parameters in brain, muscle, parotid gland and submandibular gland showed the best reproducibility using 4b gating. In the muscle, parotid gland and submandibular gland, the values of ADC, f and D were not significantly different between among the three methods.

    Conclusion: 4b gating was more reproducible with respect to measurements of IVIM parameters in comparison with 4b or 17b.

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  • Shinya Fujii, Junichi Nagaishi, Naoko Mukuda, Sachi Kaneda, Chie Inoue ...
    2017 Volume 16 Issue 3 Pages 203-208
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: December 26, 2016
    JOURNALS OPEN ACCESS

    Purpose: The characteristics of fetal thyroid on magnetic resonance (MR) imaging, including normal thyroid and disorders other than goiter have not been fully evaluated. Our aim was to assess fetal thyroid using three dimensional (3D) gradient echo (GRE) T1-weighted MR imaging and to examine the usefulness of this modality.

    Materials and Methods: The study included 27 3D GRE T1-weighted images from 26 fetuses. The largest possible region of interest (ROI) within the thyroid at the slice level depicting the thyroid was manually defined and three circular ROIs on neck muscle were manually defined on the image slices showing the highest signal intensity (SI) of the thyroid. Maximum and mean thyroid-to-muscle SI ratios (SIRs) were then calculated as SIR = maximum or mean thyroid SI/muscle SI.

    Results: The thyroid could not be identified in two cases. Fetal thyroid function was normal in 17 cases, and there were 7 cases of hypothyroidism (6 transient and 1 thyroid dysgenesis). There was no linear relationship between mean and maximum SIR and gestational age. The mean and maximum SIR in the cases of normal fetal thyroid were 1.85 ± 0.20 and 2.61 ± 0.39, and the mean and maximum SIR in fetal hypothyroidism were 1.58 ± 0.20 and 2.13 ± 0.37. Mean (P = 0.0088) and maximum (P = 0.0221) SIR values were significantly different between euthyroid and hypothyroid fetuses.

    Conclusion: Thyroid SIR measurement provided useful information regarding fetal thyroid function.

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  • Chisato Matsuo-Hagiyama, Yoshiyuki Watanabe, Hisashi Tanaka, Hiroto Ta ...
    2017 Volume 16 Issue 3 Pages 209-216
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: October 31, 2016
    JOURNALS OPEN ACCESS

    Purpose: Silent magnetic resonance imaging (MRI) scans produce reduced acoustic noise and are considered more gentle for sedated children. The aim of this study was to compare the validity of T1- (T1W) and T2-weighted (T2W) silent sequences for myelination assessment in children with conventional spin-echo sequences.

    Materials and Methods: A total of 30 children (21 boys, 9 girls; age range: 1–83 months, mean age: 35.5 months, median age: 28.5 months) were examined using both silent and spin-echo sequences. Acoustic noise levels were analyzed and compared. The degree of myelination was qualitatively assessed via consensus, and T1W and T2W signal intensities were quantitatively measured by percent contrast.

    Results: Acoustic noise levels were significantly lower during silent sequences than during conventional sequences (P < 0.0001 for both T1W and T2W). Inter-method comparison indicated overall good to excellent agreement (T1W and T2W images, κ = 0.76 and 0.80, respectively); however, agreement was poor for cerebellar myelination on T1W images (κ = 0.14). The percent contrast of silent and conventional MRI sequences had a strong correlation (T1W, correlation coefficient [CC] = 0.76; T1W excluding the middle cerebellar peduncle, CC = 0.82; T2W, CC = 0.91).

    Conclusions: For brain MRI, silent sequences significantly reduced acoustic noise and provided diagnostic image quality for myelination evaluations; however, the two methods differed with respect to cerebellar delineation on T1W sequences.

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  • Yoshihito Kadota, Toshinori Hirai, Hideo Nakamura, Keishi Makino, Shig ...
    2017 Volume 16 Issue 3 Pages 217-222
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: October 11, 2016
    JOURNALS OPEN ACCESS

    Purpose: We aimed to determine whether 3T diffusion-weighted imaging (DWI) has an additive value relative to contrast-enhanced MR imaging for the detection of disseminated lesions in patients with primary malignant brain tumors.

    Methods: We included consecutive 12 patients with nodular disseminated lesions of primary malignant brain tumors that were confirmed by surgery or follow-up MR imaging. All underwent conventional MR imaging, DWI at b = 1000 and 3000 s/mm2, post-contrast T1-weighted and 3D gradient-echo imaging at 3T. For the largest lesion per person, two radiologists independently evaluated the presence of additional information on DWI compared with postcontrast MR images using a 4-point scoring system. On DW images, one radiologist measured the lesion-to-brain contrast ratio (LBCR).

    Results: Compared with postcontrast studies, radiologists 1 and 2, respectively, assigned more apparent lesion conspicuity in 2 (17%) and 1 (8%) DWI at b = 1000 s/mm2 and 4 (33%) and 5 (42%) DWI at b = 3000 s/mm2 studies. For one of them, the mean score was significantly higher for b = 3000 s/mm2 than b = 1000 s/mm2 (P < 0.05). Interobserver agreement for DWI at b = 1000 s/mm2 and b = 3000 s/mm2 was very good (κ = 0.85; 95% CI, 0.63–1.00) and excellent (κ = 0.93; 95% CI, 0.78–1.00), respectively. The mean LBCR was significantly higher for DWI at b = 3000 s/mm2 than DWI at b = 1000 s/mm2 (P < 0.01).

    Conclusion: In the detection of disseminated lesions in patients with primary malignant brain tumors, 3T DWI has an additive value relative to contrast-enhanced MR imaging. DWI at b = 3000 s/mm2 may be more useful than DWI at b = 1000 s/mm2.

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  • Fumiaki Ueda, Hiroyuki Aburano, Yasuji Ryu, Yuichi Yoshie, Mitsutoshi ...
    2017 Volume 16 Issue 3 Pages 223-230
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: December 12, 2016
    JOURNALS OPEN ACCESS

    Purpose: The purpose of this study was to discriminate supratentorial intraventricular subependymoma (SIS) from central neurocytoma (CNC) using magnetic resonance spectroscopy (MRS).

    Methods: Single-voxel proton MRS using a 1.5T or 3T MR scanner from five SISs, five CNCs, and normal controls were evaluated. They were examined using a point-resolved spectroscopy. Automatically calculated ratios comparing choline (Cho), N-acetylaspartate (NAA), myoinositol (MI), and/or glycine (Gly) to creatine (Cr) were determined. Evaluation of Cr to unsuppressed water (USW) was also performed. Mann-Whitney U test was carried out to test the significance of differences in the metabolite ratios. Detectability of lactate (Lac) and alanine (Ala) was evaluated.

    Results: Although a statistically significant difference (P < 0.0001) was observed in Cho/Cr among SIS, control spectra, and CNC, no statistical difference was noted between SIS and control spectra (P = 0.11). Statistically significant differences were observed in NAA/Cr between SIS and CNC (P = 0.04) or control spectra (P < 0.0001). A statistically significant difference was observed in MI and/or Gly to Cr between SIS and control spectra (P = 0.03), and CNC and control spectra (P < 0.0006). There were no statistical differences between SIS and CNC for MI and/or Gly to Cr (P = 0.32). Significant statistical differences were found between SIS and control spectra (P < 0.0053), control spectra and CNC (P < 0.0016), and SIS and CNC (P < 0.0083) for Cr to USW. Lac inverted doublets were confirmed in two SISs. Triplets of Lac and Ala were detected in four spectra of CNC.

    Conclusion: The present study showed that MRS can be useful in discriminating SIS from CNC.

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  • Fumiaki Ueda, Miho Okuda, Hiroyuki Aburano, Yuichi Yoshie, Osamu Matsu ...
    2017 Volume 16 Issue 3 Pages 231-237
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: December 22, 2016
    JOURNALS OPEN ACCESS

    Purpose: To evaluate the cranial pachymeningeal involvement of polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, skin changes (POEMS) syndrome using pre- and post-contrast fluid-attenuated inversion recovery (FLAIR) and T1-weighted imaging (T1WI).

    Methods: The appearance of pachymeningeal involvement in nine cases of POEMS syndrome was evaluated using pre- and post-contrast FLAIR and T1WI. The degree of pachymeningeal thickening was graded as normal or abnormal using pre-contrast FLAIR. The degrees of contrast enhancement effect were evaluated based on pre- and post-contrast images, and recorded in each of three separate anatomical areas, i.e., the falx cerebri, cerebral convexity, and tentorium cerebelli. The degrees of contrast enhancement of pachymeninges were graded as not detected (ND), positive, or prominent on post-contrast FLAIR, and normal range (NR), positive, and prominent on post-contrast T1WI.

    Results: Pre-contrast FLAIR demonstrated 41% of pachymeningeal anatomical regions as areas of thickening. Post-contrast FLAIR did not detect any contrast enhancement on 26% of the regions but showed positive enhancement on 30% and prominent enhancement on 44%. Post-contrast T1WI showed normal range enhancement on 48%, positive enhancement on 11%, and prominent enhancement on 41% of the regions. Post-contrast FLAIR showed the highest percentage for detection of pachymeningeal abnormalities (74%).

    Conclusion: Post-contrast FLAIR may contribute to objective judgment in the evaluation of pachymeningeal involvement in POEMS syndrome.

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  • Michito Adachi, Takamichi Sato
    2017 Volume 16 Issue 3 Pages 238-244
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: January 13, 2017
    JOURNALS OPEN ACCESS

    Purpose: In elderly patients, deep and subcortical white matter hyperintense lesions are frequently observed on MRI; however, the growth process of these lesions is unclear. The aims of this retrospective cohort study were to elucidate the growth characteristics of deep and subcortical white matter hyperintense lesions, and to insight their etiology.

    Materials and Methods: We enrolled 103 patients (1610 lesions) whose deep and subcortical white matter hyperintense lesions were monitored for 3 or more years by MRI examination. The area of each hyperintense lesion was measured using a tracing method in the first and last MRI examinations. The annual rate of increase in the area of each lesion was calculated, and using the Pearson product-moment correlation coefficient the correlation between the annual rate of increase in area and the interval between the first and last MRI examinations was determined.

    Results: The paired t-test showed a significant increase in the mean area of all the deep and subcortical white matter hyperintense lesions between the first and last MRI examinations (P < 0.001). However, hyperintense lesions had decreased in the area or disappeared in 227 (14.1%) lesions in the last MRI examination, particularly in patients with diabetes. The mean annual rate of increase in area of all hyperintense lesions was 0.013 ± 0.021 cm2 per year. The annual rate of increase in area and the interval between the first and last MRI examinations showed a weak negative correlation (r = −0.121; P < 0.01).

    Conclusion: Decrease in the area and the disappearance of the subcortical white matter hyperintense lesions, and a decline in the annual rate of increase in the lesion area with time suggest that the interstitial fluid accumulation associated with dysfunctional drainage around the vessels may be involved in the possible etiologies of deep and subcortical white matter hyperintense lesions.

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  • Ken Yamaguchi, Takahiko Nakazono, Ryoko Egashira, Yoshiaki Komori, Jun ...
    2017 Volume 16 Issue 3 Pages 245-252
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: November 16, 2016
    JOURNALS OPEN ACCESS

    Purpose: To assess the diagnostic performance of readout-segmented echo-planar diffusion tensor imaging (DTI based on rs-EPI) for breast cancer and to determine the correlation between the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values obtained from DTI based on rs-EPI with prognostic markers of invasive breast cancer.

    Materials and Methods: This retrospective study examined 80 pathologically proven breast lesions (22 benign and 58 malignant lesions) of 80 patients who underwent both diffusion-weighted imaging based on single-shot echo-planar imaging (DWI based on ss-EPI) and DTI based on rs-EPI with b-values of 0 and 1000. We identified and compared the diagnostic performances of the DWI based on ss-EPI and the DTI based on rs-EPI using ADCs by conducting a receiver-operating-characteristics (ROC) analysis. We determined the correlations between the ADCs and the prognostic markers and those of the FA values and the same markers.

    Results: The median ADCs of the benign and malignant lesions based on the ss-EPI were 1.57 and 1.2 × 10−3 mm2/sec, and those based on the rs-EPI were 1.53 and 1.09 × 10−3 mm2/sec, respectively. The area under the curve on the ROC analysis based on rs-EPI (0.924) was greater than that based on ss-EPI (0.897). There were no significant correlations between the ADCs and the prognostic markers, but there were significant correlations between the FA values and the estrogen receptor status, a proliferative marker, the nuclear grade and the intrinsic subtype.

    Conclusion: For breast cancer, DTI based on rs-EPI had superior diagnostic performance compared to DWI based on ss-EPI. Compared with the ADCs, the FA values were more closely correlated with prognostic markers of invasive breast cancer.

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Technical Notes
  • Kyoung-Nam Kim, Sang-Doc Han, Jeung-Hoon Seo, Phil Heo, Dongkyeom Yoo, ...
    2017 Volume 16 Issue 3 Pages 253-258
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: September 30, 2016
    JOURNALS OPEN ACCESS

    The birdcage (BC) coil is currently being utilized for uniform radiofrequency (RF) transmit/receive (Tx/Rx) or Tx-only configuration in many magnetic resonance (MR) imaging applications, but insufficient magnetic flux (|B1|) density and their non-uniform distribution still exists in high-field (HF) environments. We demonstrate that the asymmetric birdcage (ABC) transmit/receive (Tx/Rx) volume coil, which is a modified standard birdcage (SBC) coil with the end ring split into two halves, is suitable for improving the |B1| sensitivity in 7T small-animal MR imaging. Cylindrical SBC and ABC coils with 35 mm diameter were constructed and bench tested for mouse body MR imaging at 300 MHz using a 7T scanner. To assess the ABC coil performance, computational electromagnetic (EM) simulation and 7T MR experiment were performed by using a cylindrical phantom and in vivo mouse body and quantitatively compared with the SBC coil in terms of |B1| distribution, RF transmit (|B1+|) field, and signal-to-noise ratio (SNR). The bench measurements of the two BC coils are similar, yielding a quality value (Q-value) of 74.42 for the SBC coil and 77.06 for the ABC coil. The computational calculation results clearly show that the proposed ABC coil offers superior |B1| field and |B1+| field sensitivity in the central axial slice compared with the SBC coil. There was also high SNR and uniformly distributed flip angle (FA) under the loaded condition of mouse body in the 7T experiment. Although ABC geometry allows a further increase in the |B1| field and |B1+| field sensitivity in only the central axial slice, the geometrical modification of the SBC coil can make a high performance RF coil feasible in the central axial slice and also make target imaging possible in the diagonal direction.

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  • Tomoaki Sasaki, Koji Takahashi, Makoto Obara
    2017 Volume 16 Issue 3 Pages 259-261
    Published: 2017
    Released: July 10, 2017
    [Advance publication] Released: December 22, 2016
    JOURNALS OPEN ACCESS

    Purpose: To assess the viability of oxygen-enhanced ventilation images using ultra-short echo time magnetic resonance imaging (UTE-MRI).

    Methods: We evaluated the oxygen enhancement of the pulmonary T2*, and pulmonary signals in each TE (0.2, 0.8, 1.4, 2.0 ms) in 21 nonsmokers.

    Results: The oxygen enhancement of pulmonary signals was the most significant (32%) at the 0.2 ms TE, the second in the pulmonary T2* (−18%).

    Conclusions: Pulmonary images using UTE-MRI are useful for ventilation imaging.

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Case Reports
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