Relationship between imaging parameters and distortion in magnetic resonance images for gamma knife treatment planning

In magnetic resonance imaging (MRI), it is necessary to reduce image distortion as much as possible because it suppresses the increase in the planning target volume. This study investigated the relationship between imaging parameters and image distortion when using G-frames. The images were obtained using a 1.5-T MRI system with a 09-101 Pro-MRI phantom. Image distortion was measured by changing the RF pulse mode, gradient mode, asymmetric echo, and bandwidth (BW). The image distortion was increased in the high RF mode than in the Normal mode. The image distortion increased in the following order: Whisper ≦ Normal < Fast in the different gradient modes. The image distortion increased in the following order: Without ≦ Weak < Strong in the different asymmetric echo modes. The image distortion increased in the following order: 300 Hz/pixel > 670 Hz/pixel ≧ REF (150 Hz/pixel) in the different Bw. The relationship between parameters and image distortion was clarified in this study when G-frames were used for gamma knife therapy. There is had relationship between the parameters causing variation in the gradient magnetic field and image distortion. Therefore, these parameters should be adjusted to minimize distortion.

Influence of half Fourier and elliptical scanning (radial scan) on magnetic resonance images

This study aimed to investigate the effect of using slice partial Fourier (SPF), phase partial Fourier (PPF), and radial scan (Elliptical scanning) methods on image quality. Changes in signal-to-noise ratio (SNR), effective slice thickness, and in-plane resolution were measured in 3D-gradient echo when SPF, PPF, and radial scan were used. Effective slice thickness increased and SNR increased when SPF was used; in-plane resolution decreased and SNR decreased when PPF was used; effective slice thickness did not change, in-plane resolution decreased, and SNR increased when the radial scan method was used. The radial scan method reduces image quality and imaging time compared to those in the SPF and PPF methods.

[Effectiveness of Radiological Technologists in Reporting Computed Tomography Findings in After-hour Emergencies]

PURPOSE

This study investigated the effectiveness of assistive work of radiological technologists (RTs) in conducting computed tomography (CT)/magnetic resonance imaging (MRI) during emergencies.

METHODS

In total, 2681 examinations in 2294 patients who underwent CT or MRI during our after-hours clinic hours were conducted. The emergency of the diseases was classified into three categories: emergency diseases, semi-emergency diseases, and non-emergency diseases. The reading report of the RTs group, resident physicians (RPs) group, and senior physicians (SPs) group were used to calculate the sensitivity, specificity, and accuracy.

RESULTS

The RTs group had an accuracy of 87.0% for emergency and semi-emergency diseases. The sensitivity of the combined RTs/RPs/SPs group was higher than that of the RPs and SPs group alone.

CONCLUSION

After-hours help from RTs for emergency and semi-emergency diseases enhanced sensitivity and thus demonstrated the effectiveness in emergency care.