PURPOSE: B1 field of birdcage RF (radiofrequency) coil that is used most for brain imaging in magnetic resonance imaging (MRI) decreases toward endring from the coil center. We investigated how much RF B1 homogeneity effect the endcap shield brings form the coil center as it towards to endcap region. MATERIALS AND METHODS: We compared RF B1 field distribution by each finite difference time domain (FDTD) simulations for lowpass, highpass and hybrid birdcage RF coils. We selected the highpass birdcage RF coil that was the highest RF B1 field condition as simulation result, and studied how much RF B1 homogeneity effect was occurred when endcap shield was applied to endring area. RESULTS: B1 field of the highpass birdcage RF coil was higher than other birdcage RF coil types as simulation result. However, the RF B1 homogeneity was lower than other coil types. RF B1 field of highpass birdcage RF coil with endcap shield is similar with RF B1 field of hybrid birdcage RF coil and the overall RF B1 homogeneity in sagittal direction was better. CONCLUSION: In this paper, proposed method can apply improving RF B1 homogeneity of RF coil in clinical examination.
Magnetic Resonance Imaging* ; Neuroimaging

No abstract available.
Magnetic Resonance Imaging*

Purpose: To compare the thickness of the repaired full-thickness rotator-cuff tear to that of normal rotator-cuff in young and old persons and evaluate the relationship between the tear size and the repaired thickness in the full-thickness tear using MRI. Materials and Methods: The thickness of the rotator-cuff of the repaired full thickness tear(age: 45~77, mean 63.3 years, 19 patients: group 1) were compared with those of old intact patients (age: 46~69, mean 57.9 years, 23 patients: group 2) and young intact patients (age: 18~30, mean 23.3 years, 22 patients: group 3). The tear length and width was measured in oblique coronal and oblique sagittal view of MRA, respectively, and the thickness was measured in coronal oblique view 15mm anterior to the posterolateral margin of the glenoid. Correlation between the preoperative tear size (the bigger one between the length and the width) and the postoperative thickness in group 1 was also evaluated statistically. Results: The postoperative rotator-cuff thickness in group 1 was 3.0 mm in average, which was inversely proportional to the preoperative tear size (P<0.001). The rotator-cuff thickness was 3.9mm in group 2 and 5.0mm in group 3, and there was statistically significant difference among the three groups(P<0.05). Conclusion: The rotator-cuff thickness decreases with age and the postoperative thickness in the full-thickness tear was inversely proportional to the tear size, smaller than that of the intact rotator-cuff.
Humans ; Magnetic Resonance Imaging*

No abstract available.
Magnetic Resonance Imaging* ; Osteosarcoma*

No Abstract available.
Magnetic Resonance Imaging*

No anstract available.
Magnetic Resonance Imaging* ; Spine*

No abstract available.
Dermatomyositis* ; Magnetic Resonance Imaging*

No abstract available.
Kidney* ; Magnetic Resonance Imaging*

No abstract available.
Magnetic Resonance Imaging*

No abstract available.
Hematoma* ; Magnetic Resonance Imaging*