yamaguchi kojiro

In magnetic resonance imaging (MRI) , signal intensity is dependent on the substances in a voxel. The signal is decayed when Air gap is present. In addition to that, the presence of Air gap creates a local inhomogeneity in a magnetic field, causing artifact on MR images. <br>Consequently, it is said that the influence of Air gap is less in fast spin-echo (FSE) sequences than spinecho (SE) sequences. We analyzed the effect of air on slice profiles of both SE sequences and FSE sequences in numerical simulation with Bloch equations. As a result, we confirmed that slice profile is more distorted in FSE sequences compared to SE sequences.

Following the trend of the digitalization of the modalities used for diagnostic imaging, the devices for such imaging have increasingly included monitors. The present study was undertaken to evaluate the usefulness of soft-copy (liquid crystal display; LCD) images of phantoms of small adenocarcinomas using receiver operating characteristic (ROC) analysis of two different display systems: LCD and hard copy (film). A two-tailed paired t-test and the jackknife method (parametric methods) were performed, and no significant differences were found in the area under the ROC curve (AUC) for the pulmonary fields, lungs, ribs, or mediastinum between the film and LCD display systems, and the detectability did not differ between the film and LCD monitors. A Mann-Whitney U test, which is a non-parametric method that applies to the analysis of a small sample, also showed no significant differences in the AUC. The results of this study suggest that LCDs can replace hard-copy film as a display system if the signals.

The recent increase in the incidence of SAR and fever contracted during medical examinations has raised concerns about transmission from the WB coil used during magnetic resonance imaging(MRI)using SENSE. We measured changes in temperature at the body surface during MRI medical examinations using T₂ Fast Spin Echo(T₂FSE)and Hahn T₂ Fast Spin Echo(Hahn-T₂FSE). We initially calibrated the thermometer in an incubator and confirmed that it operated normally in a high magnetic field and that it was not damaged or influenced by heat generated by RF pulses. All experiments were performed using an Excel ART Pianissimo 1.0T(Toshiba Medical Systems)and Thermo clone SL type(KN Laboratories). The temperature at the body surface changed according to the measurement point. The temperature increase was lower when measured with Hahn-T₂FSE than with T₂FSE. One limitation of this study was that temperature was measured only during 1.0 T MRI.

In general, the sinc function is the standard RF pulse employed in MRI studies. In the present study, we experimentally produced &ldquo;the original function&rdquo; by extending the Fourier cosine transform to the sinc-Gaussian function. Theoretic slice profiles obtained using the original function showed a greater improvement in the rectangular shape compared with the sinc function. As to the physical evaluation performed with 1T-MRI clinical equipment, the suppressed decrease in Contrast to Noise Ratio was higher with the original function than the sinc function in the volunteer head image multi-slice evaluation. Thus, all the results from the simulation and the clinical equipment evaluation demonstrate that the original function can improve the quality of MRI images even with shorter Echo Time.

Interslice sensitivity variation in magnetic resonance imaging (MRI) is said to be attributable to crosstalk. Crosstalk is a phenomenon in which deterioration of the rectangular profile of the RF pulse frequency characteristics leads to poor slice profiles, resulting in interference between slices. In the present study, the ideal characteristics of multislice profiles were analyzed through numerical simulation with the Bloch equation using sinc symmetrical RF pulses. The effects of the slice excitation order on the slice profile were also examined, comparing interleaved acquisition and sequential acquisition. The results of the simulation showed that the order of image acquisition affects the slice profile.