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 â‰¦ Normal < Fast in the different gradient modes. The image distortion increased in the following order: Without â‰¦ Weak < Strong in the different asymmetric echo modes. The image distortion increased in the following order: 300 Hz/pixel > 670 Hz/pixel â‰§ 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 Inversion Time of Fat Suppression Methods on Measurement of Apparent Diffusion Coefficient].

Recently, tumor differentiation in various tissues has been performed by using the apparent diffusion coefficient (ADC) value. However, the influence of ADC value due to the different inversion time (TI) of fat suppression methods has not been reported yet. Therefore, the purpose of our study was to verify the influence of the different TI of fat suppression methods on the ADC value. ADC values were compared for diffusion-weighted imaging (DWI), using the short-TI inversion recovery (STIR) method and the spectral attenuated inversion recovery (SPAIR) method. For the STIR method, when TI was closed to the null point of each phantom, signal intensity decreased, and the ADC value thereby decreased. However, by the SPAIR method, signal intensity and ADC value were not affected by the inversion time. When using the STIR method, signal intensity decreased when the null point for each phantom was approached, which was thought to decrease the ADC value. In conclusion, when using STIR-DWI after contrast agent administration, the ADC value might have been affected by the TI.

[Comparison of Kinetic Curve between Gadodiamide Hydrate and Gadobutrol on Breast Dynamic Contrast-enhanced Magnetic Resonance Imaging in Invasive Ductal Carcinoma].

The shape of the kinetic curve for gadobutrol is reportedly different compared with that for other conventional contrast agents. We speculate that the shape of gadobutrol kinetic curve may be influenced by different magnetic resonance imaging (MRI) protocols and evaluation methods. The purpose of our study was to assess the influence between gadobutrol and other conventional contrast agent (gadodiamide hydrate) on the kinetic curve in invasive ductal carcinoma (IDC). We assessed 139 women of IDC in this study. Gadodiamide hydrate (2 ml/s) was administered to 69 women, and gadobutrol (1 ml/s) was administrated to 70 women, both contrast agents at 0.1 mmol/kg BW. When the kinetic curves of contrast agents were evaluated between by Breast Imaging Reporting and Data System (BI-RADS) 4th edition and BI-RADS 5th edition, suggested that the analysis method of BI-RADS may affect. Patient group who were administered gadobutrol demonstrated a lower washout rate when compared with patient group who were administered gadodiamide hydrate administration (P<0.01). These results suggest that the kinetic curve characteristics of gadobutrol are an important consideration in diagnosis. Therefore, it is necessary to perform image diagnosis by considering the influence of the contrast agent and the analysis method, when image diagnostic doctor perform image diagnosis.

Carotid and aortic plaque imaging using 3D gradient-echo imaging and the three-point Dixon method with improved motion-sensitized driven-equilibrium (iMSDE).

BACKGROUND: We devised a method that combines the 3D-Dixon-gradientecho (GRE) method with an improved motion-sensitized driven-equilibrium (iMSDE) to suppress blood flow signals. PURPOSE: The purpose of this study was to evaluate the effectiveness of the new method we developed plaque imaging method (3D-Dixon-GRE with the iMSDE method). STUDY TYPE: Retrospective cohort. POPULATION: Thirty-nine patients who underwent cervical plaque imaging. FIELD STRENGTH/SEQUENCE: 3.0 T/3D-GRE. ASSESSMENT: Signal intensities of the common carotid artery, aorta, plaque, muscle, and subcutaneous fat were measured through the VISTA and the 3D-Dixon-GRE with iMSDE methods, and each contrast was calculated. STATISTICAL TEST: Used the Mann Whitney U test. P-values below 0.05 were considered statistically significant. RESULTS: Plaque and muscle contrast estimated through the VISTA method and 3D-Dixon-GRE with iMSDE method was 1.60 ± 0.96 and 2.04 ± 1.06, respectively, (P < 0.05). The contrast between the flow (common carotid artery and Aorta) and muscle according to the VISTA method and 3D-Dixon-GRE with iMSDE method was 0.24 ± 0.11 and 0.40 ± 0.12, respectively (P < 0.001). Finally, the mean contrast for subcutaneous fat and muscle at six locations was 3.05 ± 1.25 and 0.81 ± 0.23 for the VISTA method and 3D-Dixon-GRE with the iMSDE method, respectively (P < 0.001). DATA CONCLUSION: Compared to the conventional method (VISTA), the 3D-Dixon-GRE with iMSDE method is preferable in relation to the fat suppression effect, but it is disadvantageous regarding blood flow signal suppression. Therefore, the 3D-Dixon-GRE with the iMSDE method could be considered useful for plaque imaging.

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.