[Usefulness of Respiratory Suppression for Abdominal Using EPI Sequences].

The upper abdomen was imaged with diffusion weighted images for free breathing and respiratory suppression using single shot-echo planar imaging (SS-EPI) and readout segmented-EPI (RS-EPI). We examined the usefulness of respiratory suppression imaging for the subject of healthy volunteers. Motion artifacts, apparent diffusion coefficient (ADC) values, and organs movement distances were evaluated. As a result, motion artifacts and organs movement distances were reduced in respiratory suppression than free breathing. The ADC values did not change. Respiratory suppression was simple and useful. In addition, it was found that RS-EPI imaging could be used for imaging the upper abdomen in the same way as SS-EPI by respiratory suppression.

Evaluation of Setup Errors at the Skin Surface Position for Whole Breast Radiotherapy of Breast Cancer Patients.

We used image-processing software to analyze the setup errors at the skin surface position of breast cancer patients (n=66) who underwent post-operative whole breast irradiation at our hospital in 2014-2015. The sixty-six digital reconstructed radiographs (DRR) were created at the treatment planning for each patient. The lineacgraphies (n=377) were taken after the patients' setup during radiotherapy. The lineacgraphies and DRR were superimposed at the skin surface position for each patient with the image-processing software. We measured the deviations of the isocenters for the nipple-lung (X) direction and craniocaudal (Y) direction and the deviation of the rotation angle of the XY axes between the lineacgraphy and DRR on the superimposed images. The systematic error (µ, Σ) and random error (σ) were calculated from the X and Y deviations and rotation angle deviation. The µ of X, Y, and rotation angle were 0.01 mm, -1.2 mm, and 0.05°, respectively. The Σ of X, Y, and rotation angle were 1.8 mm, 1.5 mm, and 0.9°, respectively. The σ of X, Y, and rotation angle were 2.0 mm, 1.5 mm, and 1.0°, respectively. Our analyses thus revealed that evaluations using image-processing software at the skin surface position in routine breast radiotherapy result in sufficiently small setup errors.

The Usefulness of Readout-Segmented Echo-Planar Imaging (RESOLVE) for Bio-phantom Imaging Using 3-Tesla Clinical MRI.

Readout-segmented echo-planar imaging (RESOLVE) is a multi-shot echo-planar imaging (EPI) modality with k-space segmented in the readout direction. We investigated whether RESOLVE decreases the distortion and artifact in the phase direction and increases the signal-to-noise ratio (SNR) in phantoms image taken with 3-tesla (3T) MRI versus conventional EPI. We used a physiological saline phantom and subtraction mapping and observed that RESOLVE's SNR was higher than EPI's. Using RESOLVE, the combination of a special-purpose coil and a large-loop coil had a higher SNR compared to using only a head/neck coil. RESOLVE's image distortioas less than EPI's. We used a 120 mM polyethylene glycol phantom to examine the phase direction artifact.vThe range where the artifact appeared in the apparent diffusion coefficient (ADC) image was shorter with RESOLVE compared to EPI. We used RESOLVE to take images of a Jurkat cell bio-phantom: the cell-region ADC was 856×10-6mm2/sec and the surrounding physiological saline-region ADC was 2,951×10-6mm2/sec. The combination of RESOLVE and the 3T clinical MRI device reduced image distortion and improved SNR and the identification of accurate ADC values due to the phase direction artifact reduction. This combination is useful for obtaining accurate ADC values of bio-phantoms.

[Measurement Accuracy of Fat and Iron Deposits in the Liver Using 1H-MRS (HISTO)].

1H-MRS, which is a method of measuring fat and iron deposits in the liver, has a single voxel spectroscopy imaging method called high-speed T2-corrected multiecho (HISTO) based on the STEAM method. If HISTO measurement accuracy is high, it will be one of the biomarkers, so the measurement accuracy was examined. We imaged a self-made phantom simulating a known amount of fat and iron deposition in the liver. A regression analysis of HISTO-measured values for hepatic fat phantom was performed. In addition, regression analysis was performed on the hepatic iron phantom for the R2 values obtained from the T2 values measurement and the actually measured value of the HISTO. From the regression analysis, the correlation coefficients were 0.999, 0.992 and 0.977, respectively. The measurement accuracy of HISTO is high, and the reliability of the obtained fat and iron deposit value is high.

[Evaluation of Image Quality of Readout Segmented EPI with Readout Partial Fourier Technique].

Readout segmented EPI (readout segmentation of long variable echo-trains: RESOLVE) segmented k-space in the readout direction. By using the partial Fourier method in the readout direction, the imaging time was shortened. However, the influence on image quality due to insufficient data sampling is concerned. The setting of the partial Fourier method in the readout direction in each segment was changed. Then, we examined signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and distortion ratio for changes in image quality due to differences in data sampling. As the number of sampling segments decreased, SNR and CNR showed a low value. In addition, the distortion ratio did not change. The image quality of minimum sampling segments is greatly different from full data sampling, and caution is required when using it.

[Examination of Reacquisition Mode in Readout-segmented EPI during the Body Motion].

Readout-segmented echo planar imaging has a reacquisition mode in case of body motion. The phantom was moved and imaged to characterize the reacquisition mode. The counts, angle, and terms of continuous body motion and the terms and counts of intermittent body motion were changed. Then, we investigated the effect on the image quality and the improvement effect of the reacquisition mode. We compared the signal intensity of each pixel in images without body motion and images with and without the reacquisition mode using Spearman's correlation coefficient. The correlation coefficient decreased with increasing counts of body motion. There was no difference by angle. The correlation coefficient was high for body motion immediately after the start of imaging and decreased thereafter. The correlation coefficient was high when the counts of body motion were decreased and even when the terms of body motion increased. In all cases, the correlation coefficient was improved by the reacquisition mode.