[en] The purpose of this study was to determine the effect of the magic-angle effect on the MR signal in the posterosuperior portion of the glenoid labrum. MR imaging of 15 arthroscopically evaluated shoulders, five with posterosuperior labrum injury and ten intact, was retrospectively reviewed. In the first part of the study, the signal intensity of the posterosuperior labrum on gradient-recalled echo (GRE) T₂-weighted axial images was correlated with the arthroscopy findings. The second part of the study was designed to illustrate the orientation-dependent signal that occurs in the posterosuperior labrum of three asymptomatic volunteers when imaged in the conventional supine position and in a position similar to Trendelenburg's. Another three volunteers were examined with GRE T₂-weighted axial images to assess the echo-time (TE)-dependent signal in the labrum. The signal increase in the posterosuperior labrum was identified not only in the injured labra but also in nine of 10 intact labra. In the volunteers' studies, the signal in the posterosuperior labrum changed according to the examinees' positions (conventional supine or similar to Trendelenburg's) and according to TE. Increased signal intensity due to the magic-angle effect may be misdiagnosed as a labrum injury. Awareness of this pitfall is particularly important in MR imaging of throwing athletes whose posterosuperior labra are frequently injured by posterosuperior glenoid impingement. (author)

[en] We evaluated whether a perfusion study with Resovist is useful to assess blood flow in tumors in patients with hypervascular hepatocellular carcinoma (HCC). The subjects were 28 patients; the lesions consisted of 68 hypervascular HCC, 14 post-treatment nodules, and 7 hepatocellular hypovascular nodules. After rapid intravenous injection of Resovist, 7-phase imaging was performed using the single-shot echo-planar method. Diagnostic accuracy and tumor vascularity were evaluated by 3 radiologists using the alternative free response receiver operating characteristic method. Sensitivity, Az values, and positive predictive values were calculated. To assess interobserver variability, we evaluated the kappa static to measure the degree of agreement. The 3 observers indicated no significant difference in Az value related to the presence or absence of a perfusion study, and only one remarked a significant difference in sensitivity. However, kappa values were better in the presence than in the absence of a perfusion study. Blood flow assessment was poor in less than 1 cm. The 3 observers showed a positive predictive value of 90% or more. A perfusion study may facilitate the diagnosis of hypervascular HCC, improving the diagnostic accuracy. (author)

[en] We examined the temperature dependence of relaxation times in proton components of fatty acids in various samples in vitro at 11 tesla as a standard calibration data for quantitative temperature imaging of fat. The spin-lattice relaxation time, T₁, of both the methylene (CH₂) chain and terminal methyl (CH₃) was linearly related to temperature (r>0.98, P<0.001) in samples of animal fat. The temperature coefficients for the 2 primary proton components differed significantly; in 5 bovine fat samples, the coefficient at 30 deg C was 1.79±0.07 (%/deg C) for methylene and 2.98±0.38 (%/deg C) for methyl. Numerical simulations based on such a difference demonstrated the possibility of considerable error from inconsistent ratios in fatty acid components when calibrating and estimating temperature. The error reached 3.3 deg C per 15 deg C in temperature elevation when we used a pure CH₂ signal for calibration and observed the signal with 18% of CH₃ to estimate temperature. These findings suggested that separating the fatty acid components would significantly improve accuracy in quantitative thermometry for fat. Use of the T₁ of CH₂ seems promising in terms of reliability and reproducibility in measuring temperature of fat. (author)

[en] We investigated whether a rice pad could be used to reduce the geometric distortion in echo-planar diffusion-weighted images of the cervical spinal cord. In 10 healthy volunteers, we obtained sagittal plane images using the same imaging parameters with and without a rice pad. Two reviewers classified geometric distortion and visually assessed images. Use of a rice pad significantly reduced geometric distortion in the cervical spinal cord. (author)

[en] Because it is noninvasive, magnetic resonance microimaging (MRMI) can be used for 3-dimensional measurement of living tissues for cell engineering. Thermal noise in the resonance circuit of the radiofrequency (RF) system of the MRMI cannot become ignored as the signal diminishes in accordance with decreasing sample size, and cooling the RF coil of the receiver circuit can effectively reduce thermal noise. We used a low temperature normal conductor circuit to reduce noise and confirmed improved signal-to-noise ratio for a conventional microimaging system at low B₀ field (0.3T) with low cost. (author)

[en] Using 4 and 8-channel super-parallel magnetic resonance (MR) microscopes with a horizontal bore 2.34T superconducting magnet developed for 3-dimensional MR microscopy of the large Kyoto Collection of Human Embryos, we acquired T₁-weighted 3D images of 1204 embryos at a spatial resolution of (40 μm)³ to (150 μm)³ in about 2 years. Similarity of image contrast between the T₁-weighted images and stained anatomical sections indicated that T₁-weighted 3D images could be used for an anatomical 3D image database for human embryology. (author)

[en] The purpose of this study was to investigate the utility of diffusion-weighted imaging (DWI) and the apparent diffusion coefficient (ADC) value in differentiating benign and malignant breast lesions and evaluating the detection accuracy of the cancer extension. We used DWI to obtain images of 191 benign and malignant lesions (24 benign, 167 malignant) before surgical excision. The ADC values of the benign and malignant lesions were compared, as were the values of noninvasive ductal carcinoma (NIDC) and invasive ductal carcinoma (IDC). We also evaluated the ADC map, which represents the distribution of ADC values, and compared it with the cancer extension. The mean ADC value of each type of lesion was as follows: malignant lesions, 1.22±0.31 x 10^-3 mm²/s; benign lesions, 1.67±0.54 x 10^-3 mm²/s; normal tissues, 2.09±0.27 x 10^-3 mm²/s. The mean ADC value of the malignant lesions was statistically lower than that of the benign lesions and normal breast tissues. The ADC value of IDC was statistically lower than that of NIDC. The sensitivity of the ADC value for malignant lesions with a threshold of less than 1.6 x 10^-3 mm²/s was 95% and the specificity was 46%. A full 75% of all malignant cases exhibited a near precise distribution of low ADC values on ADC maps to describe malignant lesions. The main causes of false negative and underestimation of cancer spread were susceptibility artifact because of bleeding and tumor structure. Major histologic types of false-positive lesions were intraductal papilloma and fibrocystic diseases. Fibrocystic diseases also resulted in overestimation of cancer extension. DWI has the potential in clinical appreciation to detect malignant breast tumors and support the evaluation of tumor extension. However, the benign proliferative change remains to be studied as it mimics the malignant phenomenon on the ADC map. (author)

[en] MRI (magnetic resonance imaging) with ¹²⁹Xe has gained much attention as a diagnostic methodology because of its affinity for lipids and possible polarization. The quantitative estimation of net detectability and stability of hyperpolarized ¹²⁹Xe in the dissolved phase in vivo is valuable to the development of clinical applications. The goal of this study was to develop a stable hyperpolarized ¹²⁹Xe experimental 3T system to statistically analyze the dissolved-phase ¹²⁹Xe signal in the rat lungs. The polarization of ¹²⁹Xe with buffer gases at the optical pumping cell was measured under adiabatic fast passage against the temperature of an oven and laser absorption at the cell. The gases were insuffiated into the lungs of Sprague-Dawley rats (n=15, 400-550 g) through an endotracheal tube under spontaneous respiration. Frequency-selective spectroscopy was performed for the gas phase and dissolved phase. We analyzed the ¹²⁹Xe signal in the dissolved phase to measure the chemical shift, T₂^*, delay and its ratio in a rat lungs on 3T. The polarizer was able to produce polarized gas (1.1±0.47%, 120 cm³) hundreds of times with the laser absorption ratio (25%) kept constant at the cell. The optimal buffer gas ratio of 25-50% rendered the maximum signal in the dissolved phase. Two dominant peaks of 211.8±0.9 and 201.1±0.6 ppm were observed with a delay of 0.4±0.9 and 0.9±1.0 s from the gas phase spectra. The ratios of their average signal to that of the gas phase were 5.6±5.2% and 4.4±4.7%, respectively. The T₂^* of the air space in the lungs was 2.5±0.5 ms, which was 3.8 times shorter than that in a syringe. We developed a hyperpolarized ¹²⁹Xe experimental system using a 3T MRI scanner that yields sufficient volume and polarization and quantitatively analyzed the dissolved-phase ¹²⁹Xe signal in the rat lungs. (author)

[en] In radiofrequency (RF) coil design for ultra-high-field magnetic resonance (MR) imaging, short RF wavelengths present various challenges to creating a big volume coil. When imaging a human body using an ultra-high magnetic field MR imaging system (magnetic flux density of 7 Tesla or more), short wavelength may induce artifacts from dielectric effect and other factors. To overcome these problems, we developed a patch antenna array coil (PAAC), which is a coil configured as a combination of patch antennas. We prototyped this type of coil for 7T proton MR imaging, imaged a monkey brain, and confirmed the coil's utility as an RF coil for ultra-high-field MR imaging. (author)

[en] The author reviewed brain-imaging studies on human handedness reported in major academic journals for the last 12 years, classified them as having anatomical or functional interest, and attempted to determine consensus on findings and limitations among the studies. Present reviews suggest that there have been fewer functional than anatomical examinations into handedness and that findings from those studies have not been necessarily consistent, that participants' degree of handedness has not been consistent between left-handed and right-handed people, and that much more brain-imaging study is anticipated to examine functional and anatomical differences of handedness based on genetic and environmental models. (author)