可変フリップ角を用いた3D-T2強調像(3D-SPACE)におけるコントラスト特性の検討

Purpose: Sampling perfection with application optimized contrasts using different flip angle evolution (3D-SPACE) sequence enables one to decrease specific absorption rate (SAR) by using variable flip angle refocusing pulse. Therefore, it is expected that the contrast obtained with 3D-SPACE sequences is different from that of spin echo (SE) images and turbo spin echo (TSE) images. The purpose of this study was to evaluate the characteristics of the signal intensity and central nervous system (CNS) image contrast in T2 weighted 3D-SPACE. Method: Using 3 different sequences (SE, 3D-TSE and 3D-SPACE) with TR/TE=3500/70, 90 and 115 ms, we obtained T2 weighted magnetic resonance (MR) images of inhouse phantom and five healthy volunteers’ brain. Signal intensity of the phantom which contains various T1 and T2 value was evaluated. Tissue contrasts of white/gray matter, cerebrospinal fluid (CSF)/subcutaneous fat and gray matter/subcutaneous fat were evaluated for a clinical image study. Results: The phantom study showed that signal intensity in 3D-SPACE significantly decreased under a T1 value of 250 ms. It was markedly decreased in comparison to other sequences, as effective echo time (TE) was extended. White/gray matter contrast of 3D-SPACE was the highest in all sequences. On the other hand, CSF/fat and gray matter/fat contrast of 3D-SPACE was higher than TSE but lower than SE. Conclusion: CNS image contrasts of 3D-SPACE were comparable to that of SE. Signal intensity had decreased in the range where T1 and T2 values were extremely short.