Optimum Refocus Flip Angle of Non-contrast Magnetic Resonance Angiography Using ECG-gated 3D-TSE

Abstract

In triggered acquisition noncontrast enhancement magnetic resonance angiography using ECG-gated with short-term inversion recovery (STIR-TRANCE), signal intensity and contrast fluctuate according to the value of refocus flip angle (RFA). We believe that we can visualize the pulmonary vascular excellently by optimized RFA which improves the signal intensity of pulmonary vascular and the contrast between pulmonary vascular and lung parenchyma. The purpose of this study is to optimize RFA in pulmonary vascular magnetic resonance angiography (MRA) imaging using STIR-TRANCE. Pulmonary vascular MRA was performed in five normal volunteers. The department's ethics committee approved the study, and informed consent was obtained from all subjects. Before the STIR-TRANCE study, an ECG-gated single shot TSE (SS TSE) scan was performed to determine the timing of diastole. Later, the diastolic STIR-TRANCE imaging using both ECG and respiratory gating was performed with three different RFA (140 degree, 160 degree, and 180 degree). For physical evaluation, we used the signal to noise ratio (SNR) and contrast and for visual evaluation, so we used the Scheffe's method. SNR increases with increasing RFA. The contrast of 160 degree was significantly higher than the contrast of 180 degree. There was no significant difference in visual evaluation. From the perspective of specific absorption rate (SAR) reduction, we concluded that the optimal RFA for pulmonary vascular MRA in this study was 160 degree.