A method was devised for obtaining dynamic contrast-enhanced T1-weighted and relaxation rate (delta R2*) images simultaneously to evaluate regional hemodynamics of the brain tumors. On a 1.5-T MR system, dual dynamic contrast-enhanced images were obtained using a gradient echo (dual echo fast field echo) pulse sequence with the keyhole technique to improve temporal and spatial resolution during a rapid bolus injection of gadopentetate dimeglumine. The dynamic T1 contrast images were obtained from the first echo: moreover. integral delta R2*dt values were calculated from the first and the second echo images. The dynamic T1 contrast images provided information about characteristic enhancement pattern (vascularization and disruption of blood-brain barrier), and the integral delta R2*dt values provided a map of regional blood pool in tumor site, peritumoral edema, and other surrounding regions of the brain. The ability to obtain dynamic contrast-enhanced T1 contrast and delta R2* imaging at the same time allows optimization of the advantages of each and thereby more information about the microvascular circulation of the brain lesions.

Background To noninvasively obtain more detailed information on brain perfusion and diffusion using modified triexponential analysis. Methods On a 3.0 Tesla MRI, diffusion‐weighted imaging of the brain with multiple b‐values was performed in healthy volunteers (n = 12). We derived perfusion‐related, fast‐free, and slow‐restricted diffusion coefficients (Dp, Df, and Ds, respectively) and fractions (Fp, Ff, and Fs, respectively) in the frontal and occipital white matter, caudate nucleus, and putamen calculated from triexponential function by a two‐step approach. Ds was initially determined using monoexponential function in b‐values over 1000 s/mm2 and was applied to triexponential function. Additionally, the literature value of the diffusion coefficient of free water at 37 °C was assigned to Df. Finally, Dp and fractions were derived using all b‐values. Moreover, biexponential analysis was performed and compared with triexponential analysis. We also determined regional cerebral blood flow (rCBF) using arterial spin labeling and assessed its relation with each diffusion parameter. Results Significant positive correlations between Dp and rCBF were found in the caudate nucleus (R = 0.84; P = 0.01) and putamen (R = 0.86; P = 0.01), whereas no diffusion parameters were significantly correlated with rCBF on biexponential analysis (P > 0.05 for all). Conclusion Diffusion analysis with triexponential function enables noninvasive gathering of more detailed information on brain perfusion and diffusion. J. Magn. Reson. Imaging 2016;43:818–823

Our objective was to clarify intracranial cerebrospinal fluid (CSF) flow dynamics in normalpressure hydrocephalus (NPH). Frequency analyses of CSF flow measured with phase-contrast cine MRI were performed. The CSF flow spectra in the aqueduct were determined in patients (n=51) with NPH, brain atrophy or asymptomatic ventricular dilation (VD), and in healthy volunteers (control group; n=25). The changes in CSF flow spectra were also analyzed after intravenous injection of acetazolamide. Moreover, a phase transfer function (PTF) calculated from the spectra of the driving vascular pulsation and CSF flow in the aqueduct were assessed. These values were compared with the pressure volume response (PVR). The amplitude in the NPH group was significantly larger than that in the VD or control group because of a decrease in compliance. The phase in the NPH group was significantly different from that in either the VD or the control group, but no differ-ence was found between the VD and control groups. The amplitude increased in all groups after acetazolamide injection. The PTF in the NPH group was significantly larger than in the control group, and a positive correlation was noted between PTF and PVR. Frequency analyses of CSF flow measured by cine MRI make it possible to noninvasively obtain a more detailed picture of the pathophysiology of NPH.

The purpose of this study was to evaluate acoustic noise in echo planar imaging (EPI) at various magnetic resonance imaging (MRI) centers and to compare EPI acoustic noise with that in other fast pulse sequences. We measured A-weighted root-mean-square sound pressure levels and peak impulse sound pressure levels for EPI, under the same conditions, in eleven clinical super-conducting MRI systems. We also compared sound pressure levels for the EPI and six different pulse sequences and analyzed the acoustic noise spectra. Sound pressure levels during the use of the EPI differed greatly among institutions. Moreover, sound pressure levels of the EPI were not significantly different from those of other fast pulse sequences and were within permissible noise exposure levels. In comparison to other fast sequences, the EPI had significantly greater acoustic noise in the high-octave band frequency.

A method was developed for accurate measurement of the modulation transfer function (MTF) and signal-to-noise ratio in the spatial frequency domain (SNR(f)) of magnetic resonance images (MRI). The MTF was calculated from the complex images of a line object which were obtained by the subtraction of two separately acquired data sets of a specially designed phantom with a sliding sheet. Moreover, the SNR(f) was calculated from the MTF and Wiener spectrum, both of which were determined using the same phantom configuration. The MTFs and SNR(f)s in the conventional spin-echo (SE) and turbo SE, in which the effective echo time was set to the first echo, were evaluated by changing the T2 of the phantom and the echo train length. The MTFs in the positive and negative frequencies indicated the effect of the k-space trajectory for each pulse sequence. SNR(f)s gave spatial frequency information that was not obtained with conventional methods. In this method, the influence of image nonuniformity and unwanted artefacts (edge and ghost) could be eliminated. An analysis of the MTF and the SNR in the spatial frequency domain provides additional information for the assessment of image quality in MRI.

Objective:To compare the performance on the detection of the invisible veins between our modified prototype device and an existing device in elderly hospitalized patients.Methods:A prospective, cross-sectional, and observational study was performed in the invisible veins in elderly patients. The major variables, skin color near the invisible veins, and diameter and depth of the invisible veins were measured. The vein visualization rate was calculated as the ratio of the visualized veins to the invisible veins by the visualization device.Results:We analyzed 53 invisible veins in the cubital fossa and 56 invisible veins in the forearm in a total of 72 patients (median age, 73 years). The visualization rate for our prototype device was higher than that for an existing device in the cubital fossa and the forearm sites. The visualized veins of the prototype device had a higher intensity ratio than that of an existing device. No significant differences were observed in the body mass index, vein depth, and vein diameter of the visualized veins at the cubital fossa and forearm sites.Conclusion:The prototype surpassed the existing device in visualizing the invisible veins. However, the prototype was unable to visualize all the invisible veins. We need to look for ways to reduce noise and to visualize the invisible veins, and the visualization rate of devices needs to be investigated in further association with the percentage of success with actual intravenous access and locating time to vein.

Objective:Lymphoedema involves swelling, especially in the subcutaneous tissues. For lymphoedema management to be successful, it is necessary to remove the interstitial fluid. Subcutaneous echogenicity may be associated with interstitial fluid, but echogenicity is not an indicator for the evaluation of management because we do not directly compare echogenicity with the interstitial fluid. We aimed to identify an outcome indicator for the evaluation of interstitial fluid using ultrasonography. We assessed the correlation between echogenicity and transverse relaxation rate (R2) on magnetic resonance imaging.Methods:This was an observational study. Healthy adults with leg swelling after activity for >8 h were recruited. The legs of 13 women were evaluated using ultrasonography, magnetic resonance imaging and measurements of the limb circumference before and after an intervention to reduce the swelling.Results:Echogenicity in the oedema group was greater than that of the controls. Echogenicity decreased with reductions in oedema. The range of the strongest correlations with the changes in R2 occurred at echogenicity values of 48–144 (Pearson’s correlation coefficient: r = −0.63 and p < 0.01). Thus, it was possible to evaluate the interstitial fluid using echogenicity.Conclusion:The outcome indicators for the evaluation of interstitial fluid using ultrasonography were echogenicities in the range of 48–144, and these values were valid for assessing the interstitial fluid in the subcutaneous tissue.

[Purpose] This study aimed to clarify whether the morphological changes of the lower leg muscle occur equally in the longitudinal direction of the muscle according to changes in ankle joint position during sitting. [Participants and Methods] The participants were 15 healthy young females whose dominant lower legs were analyzed. The participants sat with the lower leg vertical to the floor with a neutral, dorsiflexed, or plantarflexed ankle position. Images were obtained from the fibular head from 290 mm distal using gravity magnetic resonance imaging. The muscle cross-sectional areas of the soleus, medial and lateral heads of the gastrocnemius, and anterior tibialis were measured. [Results] The muscle cross-sectional area of the soleus at the 1/4 proximal muscle belly in the plantarflexed position was greater than those in the other positions. The 1/4 distal part in the plantarflexed position was smaller than those in the other positions. The muscle cross-sectional area of the gastrocnemius at the 1/4 distal part in the plantarflexed position was smaller than that in the dorsiflexed position. In contrast, the muscle cross-sectional area of the tibialis anterior at the 1/4 proximal part in the dorsiflexed position was greater than those in the other positions, while that at the 1/4 distal part in the dorsiflexed position was smaller than that in the plantarflexed position. [Conclusion] In the sitting position, the morphological changes of the lower leg muscle according to changes in ankle joint position are not uniform in the longitudinal muscle direction.