Magnetic Resonance in Medical Sciences
Online ISSN : 1880-2206
Print ISSN : 1347-3182
ISSN-L : 1347-3182
13 巻, 3 号
選択された号の論文の10件中1~10を表示しています
Major Papers
  • Ryutaro NAKAGAMI, Masayuki YAMAGUCHI, Kenji EZAWA, Sadaaki KIMURA, Shu ...
    2014 年 13 巻 3 号 p. 145-153
    発行日: 2014/09/01
    公開日: 2014/09/29
    [早期公開] 公開日: 2014/07/02
    ジャーナル オープンアクセス
    Purpose: We explored a recovery correction technique that can correct metabolite loss during perchloric acid (PCA) extraction and minimize inter-assay variance in quantitative 1H nuclear magnetic resonance (NMR) spectroscopy of the brain and evaluated its efficacy in 5-fluorouracil (5-FU)- and saline-administered rats.
    Methods: We measured the recovery of creatine and dl-valine-2,3-d2 from PCA extract containing both compounds (0.5 to 8 mM). We intravenously administered either 5-FU for 4 days (total, 100 mg/kg body weight) or saline into 2 groups of 11 rats each. We subsequently performed PCA extraction of the whole brain on Day 9, externally adding 7 µmol of dl-valine-2,3-d2. We estimated metabolite concentrations using an NMR spectrometer with recovery correction, correcting metabolite concentrations based on the recovery factor of dl-valine-2,3-d2. For each metabolite concentration, we calculated the coefficient of variation (CEV) and compared differences between the 2 groups using unpaired t-test.
    Results: Equivalent recoveries of dl-valine-2,3-d2 (89.4 ± 3.9%) and creatine (89.7 ± 3.9%) in the PCA extract of the mixed solution indicated the suitability of dl-valine-2,3-d2 as an internal reference. In the rat study, recovery of dl-valine-2,3-d2 was 90.6 ± 9.2%. Nine major metabolite concentrations adjusted by recovery of dl-valine-2,3-d2 in saline-administered rats were comparable to data in the literature. CEVs of these metabolites were reduced from 10 to 17% before to 7 to 16% after correction. The significance of differences in alanine and taurine between the 5-FU- and saline-administered groups was determined only after recovery correction (0.75 ± 0.12 versus 0.86 ± 0.07 for alanine; 5.17 ± 0.59 versus 5.66 ± 0.42 for taurine [µmol/g brain tissue]; P < 0.05).
    Conclusion: A new recovery correction technique corrected metabolite loss during PCA extraction, minimized inter-assay variance in quantitative 1H NMR spectroscopy of brain tissue, and effectively detected inter-group differences in concentrations of brain metabolites between 5-FU- and saline-administered rats.
  • Chen-Chiang LIN, Chih-Nan WANG, Yang-Kun OU, Jachih FU
    2014 年 13 巻 3 号 p. 155-166
    発行日: 2014/09/01
    公開日: 2014/09/29
    [早期公開] 公開日: 2014/07/02
    ジャーナル オープンアクセス
    Purpose: The diagnosis of most rotator cuff tears (RCTs) relies upon magnetic resonance (MR) imaging, but direct capture of MR images without enhanced image processing leads to poor image contrast and potential misdiagnosis. Therefore, we developed a 2-stage model for the detection and diagnosis of injury of the supraspinatus tendon.
    Methods: The first stage used coupled weighted histogram separation (WHS) to improve image enhancement, and the second stage extracted suspicious texture, features of both spatial and spectral domains, and sequential floating forward selection (SFFS) selected features conducive to classification of RCTs. We then tested injuries of the supraspinatus tendon using the classifier.
    Results: The extraction of features by SFFS can increase detection of supraspinatus injury by reducing the input vector by 57.78% from the enhanced input images. The receiver operating characteristic (ROC) curve indicated an azimuth (Az) value of 84.38% when SFFS selected 76 features to construct a support vector machine (SVM) classifier from the enhanced images, compared with 56.94% when all 180 features from the raw input images were used for the construction.
    Conclusions: The performance of the classifier constructed by SFFS-selected features is superior to that using all features. These findings can serve as references to improve diagnosis and treatment of supraspinatus injuries.
  • Bjoern P. SCHOENNAGEL, Chressen C. REMUS, Ulrike WEDEGAERTNER, Ina SAL ...
    2014 年 13 巻 3 号 p. 167-173
    発行日: 2014/09/01
    公開日: 2014/09/29
    [早期公開] 公開日: 2014/07/02
    ジャーナル オープンアクセス
    Purpose: We evaluated the feasibility of prenatal quantification of liver and spleen iron by magnetic resonance imaging (MRI) gradient recalled echo (GRE) measurements of transverse relaxation time (R2*) (MRI-GRE-R2*) in a fetal sheep model and applied the method to a human neonate with suspected neonatal hemochromatosis.
    Methods: We subjected 13 fetal sheep to MRI at 1.5 Tesla using a breath-triggered (ewe) multi-echo sequence to determine the transverse relaxation rate (R2*) of the liver and spleen. In the human neonate, we measured the R2* of the liver, spleen, and pancreas on the 30th postgestational day.
    Results: The median R2* of the fetal sheep liver was 25.6 s−1 (range 20 to 114 s−1) and of the spleen, 40.2 s−1 (range 20 to 70 s−1), and the corresponding median iron concentration in the liver was 0.85 mg/gdry weight (d.w.) and in the spleen, 1.22 mg/gd.w.. R2* rates in the human neonate liver were elevated between 67 s−1 (average), which corresponded with an iron concentration of 1.9 mg Fe/gd.w., and 126 s−1 (regional maximum), which corresponded with 3.4 mg Fe/gd.w.. The average pancreatic R2* (72.4 s−1) was significantly above normal values, which indicated iron overload.
    Conclusion: We demonstrated the feasibility of prenatal quantification of tissue iron by fetal MRI in this sheep model and successfully quantified iron, including that in the pancreas, in a human neonate to confirm the diagnosis of neonatal hemochromatosis. Transferring the successful approach of quantifying iron in intrauterine tissue in fetal sheep to human pregnancies with suspected fetal siderosis could aid early diagnosis.
  • Yoshimitsu OHGIYA, Jumpei SUYAMA, Shoei SAI, Masaaki KAWAHARA, Nobuyuk ...
    2014 年 13 巻 3 号 p. 175-181
    発行日: 2014/09/01
    公開日: 2014/09/29
    [早期公開] 公開日: 2014/07/02
    ジャーナル オープンアクセス
    Purpose: We evaluated the ability of diffusion-weighted imaging (DWI) at 3 tesla for diagnosing T stage and detecting stalks in bladder cancer.
    Methods: In total, 39 consecutive patients with bladder tumors underwent magnetic resonance (MR) imaging that included T2-weighted imaging (T2WI) and DWI using a 3T MR scanner. Two radiologists interpreted T2WI plus DWI and T2WI for diagnosis of T stage and for detection of stalks. We used McNemar’s test to examine differences in diagnostic performance and Fisher’s exact test to evaluate differences in stalk detection frequency.
    Results: Specificity and accuracy in differentiating T1 tumors from T2 to T4 tumors were significantly better with T2WI plus DWI (83% [20/24] and 85% [33/39]) than T2WI (50% [12/24] and 67% [26/39]; P = 0.02), and accuracy for diagnosing tumor stage was significantly better with T2WI plus DWI (82% [32/39]) than T2WI alone (59% [23/39]; P = 0.03). The observers identified stalks in 11 tumors by T2WI (48% [11/23]) and 17 by DWI (74% [17/23]) (P < 0.03).
    Conclusion: DWI at 3T was superior to T2WI for evaluating the T stage of bladder cancer, particularly in differentiating T1 tumors from those T2 or higher, and in detecting stalks of papillary bladder tumors.
  • Tomoyuki HIDA, Akihiro NISHIE, Yoshiki ASAYAMA, Kousei ISHIGAMI, Yasuh ...
    2014 年 13 巻 3 号 p. 183-189
    発行日: 2014/09/01
    公開日: 2014/09/29
    [早期公開] 公開日: 2014/07/02
    ジャーナル オープンアクセス
    Purpose: Using pathologically proven tumors and 3 methods of apparent diffusion coefficient (ADC) measurement, we examined the potential of diffusion-weighted imaging (DWI) to differentiate adrenal tumors.
    Methods: We evaluated adrenal tumors of 52 patients who underwent magnetic resonance (MR) examination including DWI and adrenal resection or biopsy between July 2006 and August 2011. Tumors included 25 cortical adenomas, 14 pheochromocytomas, 6 adrenal metastases, and seven others. We defined the tumor’s “solid” region as an enhancing area on contrast-enhanced MR or computed tomography (CT) and measured the ADC of the tumor’s “entire” and “solid” regions within a region of interest (ROI) placed on an ADC map (“entire” and “solid” ADCs). We obtained a “minimum” ADC by placing an ROI in an area showing the lowest ADC within the “solid” region. We also calculated the ratio of “non-solid” area to “entire” tumor and compared the average “entire,” “solid,” and “minimum” ADCs and the ratio of “non-solid” area to “entire” tumor between benign and malignant groups.
    Results: The average “entire” ADC was significantly higher for the benign (1.35 ± 0.38 × 10−3 mm2/s) than malignant group (1.01 ± 0.17 × 10−3 mm2/s), and the average “solid” and “minimum” ADC and the ratio of “non-solid” area to “entire” tumor did not differ significantly between the benign and malignant groups.
    Conclusion: The higher “entire” ADC value of the benign group, which might be obtained incidentally, can be considered dependent on the condition of necrosis, hemorrhage, and degeneration. ADC measurement of a tumor’s “solid” region was not useful for differentiating pathologically proven adrenal tumors.
  • Koichi OSHIO, Hiroshi SHINMOTO, Robert V. MULKERN
    2014 年 13 巻 3 号 p. 191-195
    発行日: 2014/03/01
    公開日: 2014/09/29
    [早期公開] 公開日: 2014/08/27
    ジャーナル オープンアクセス
    Purpose: Although many models have been proposed to interpret non-Gaussian diffusion MRI data in biological tissues, it is often difficult to see the correlation between the MRI data and the histological changes in the tissue. Among these models, so called statistical models, which assume the diffusion coefficient D is distributed continuously within a voxel, are more suitable for interpreting the data in a histological context than others. In this work, we examined a statistical model based on the gamma distribution.
    Methods: First, the proposed gamma model, the bi-exponential model, and the truncated Gaussian model were compared for goodness of fit. To evaluate diagnostic capability, area fractions of certain D ranges were evaluated. The area fraction for D < 1.0 mm2/s (frac < 1) was attributed to small cancer cells with restricted diffusion, and the area fraction for D > 3.0 mm2/s (frac > 3) was considered to reflect perfusion component. A clinical data set of histologically proven prostate cancer cases from previous study was used.
    Results: For the cancer tissue, the gamma model was better fit than the truncated Gaussian model, and there was no significant difference between the gamma model and the bi-exponential model. For the normal peripheral zone tissue, there was no significant differences among all models. In the 2D scatter plot of frac < 1 vs. frac > 3, Cancer and non-cancer tissues were clearly separated.
    Conclusion: Using the proposed model, the diffusion MR data was well fit, and histological interpretation of the data appears possible.
Brief Communication
Technical Notes
  • Yosuke OTAKE, Yoshihisa SOUTOME, Koji HIRATA, Hisaaki OCHI, Yoshitaka ...
    2014 年 13 巻 3 号 p. 199-205
    発行日: 2014/09/01
    公開日: 2014/09/29
    [早期公開] 公開日: 2014/07/02
    ジャーナル オープンアクセス
    We developed a double-tuned radiofrequency (RF) coil using a novel circuit method to double tune for fluorine-19 (19F) and 1H magnetic resonance imaging, whose frequencies are very close to each other. The RF coil consists of 3 parallel-connected series inductor capacitor circuits. A computer simulation for our double-tuned RF coil with a phantom demonstrated that the coil has tuned resonant frequency and high sensitivity for both 19F and 1H. Drug distribution was visualized at 7 tesla using this RF coil and a rat administered perfluoro 15-crown-5-ether emulsion. The double-tune RF coil we developed may be a powerful tool for 19F and 1H imaging.
  • Kagayaki KURODA, Naoki SHIRAKAWA, Yoshiyuki YOSHIDA, Kazuya TAWARA, Ak ...
    2014 年 13 巻 3 号 p. 207-214
    発行日: 2014/09/01
    公開日: 2014/09/29
    [早期公開] 公開日: 2014/07/02
    ジャーナル オープンアクセス
    We evaluated the magnetization of 21 cosmetic contact lens samples that included various coloring materials with a superconducting quantum interference device with regard to magnetic resonance (MR) safety. We found 7 samples were ferromagnetic; two had both ferromagnetic and diamagnetic properties; and the rest were diamagnetic. The saturated magnetization of the most ferromagnetic sample was 15.0 µJ/T, which yielded a magnetically induced displacement force of 90.0 µN when the spatial gradient of the static magnetic field was 6.0 T/m. The force was less than one-third of the gravitational force.
  • Yasuhiko TERADA, Saki KONO, Tomomi UCHIUMI, Katsumi KOSE, Ryo MIYAGI, ...
    2014 年 13 巻 3 号 p. 215-219
    発行日: 2014/09/01
    公開日: 2014/09/29
    [早期公開] 公開日: 2014/07/02
    ジャーナル オープンアクセス
    The purpose of this study was to improve the reliability and validity of skeletal age assessment using an open and compact pediatric hand magnetic resonance (MR) imaging scanner. We used such a scanner with 0.3-tesla permanent magnet to image the left hands of 88 healthy children (aged 3.4 to 15.7 years, mean 8.8 years), and 3 raters (2 orthopedic specialists and a radiologist) assessed skeletal age using those images. We measured the strength of agreement in ratings by values of weighted Cohen’s κ and the proportion of cases excluded from rating because of motion artifact and inappropriate positioning. We compared the current results with those of a previous study in which 93 healthy children (aged 4.1 to 16.4 years, mean 9.7 years) were examined with an adult hand scanner. The κ values between raters exceeded 0.80, which indicates almost perfect agreement, and most were higher than those of the previous study. The proportion of cases excluded from rating because of motion artifact or inappropriate positioning was also reduced. The results indicate that use of the compact pediatric hand scanner improved the reliability and validity of skeletal age assessments.
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