Schmitz Bernd L, Grön Georg, Brausewetter Florian, Hoffmann Martin H K, Aschoff Andrik J
Department of Radiology, University Hospitals, Ulm, Germany.
AJNR Am J Neuroradiol. 2005 Sep;26(8):2000-4.
Compared with MR imaging at 1.5T T1-weighted spin-echo imaging at 3T shows up with reduced gray-to-white matter contrast. The purpose of the present study was to show the effects of alterations of different flip angles as an easily accessible parameter to increase gray-to-white matter contrast.
Spin-echo T1 sequences of 6 healthy volunteers were acquired in a 3T head scanner with 5 different flip angles. Observer-independent contrast-to-noise ratios for gray versus white matter from different flip angles, as well as subjective ratings of image quality from 2 blinded neuroradiologists, were compared statistically.
Gray-to-white matter contrast increased significantly with decreasing flip angle. No artifacts were introduced by decreasing flip angles, and T1 contrast characteristics were robust and stable at lowered flip angles. Also, specific absorption ratios significantly decreased with decreasing flip angles.
Using a flip angle of 50 degrees significantly increases gray-to-white matter contrast in T1 spin-echo brain scans at 3T B0 field strength.
与1.5T的磁共振成像相比，3T的T1加权自旋回波成像显示出灰质与白质对比度降低。本研究的目的是展示不同翻转角的改变作为一个易于获取的参数对增加灰质与白质对比度的影响。
在一台3T头部扫描仪中，对6名健康志愿者采用5种不同的翻转角采集自旋回波T1序列。对不同翻转角下灰质与白质的客观对比度噪声比以及2名盲法神经放射科医生对图像质量的主观评分进行统计学比较。
灰质与白质对比度随翻转角减小而显著增加。减小翻转角未引入伪影，且在较低翻转角下T1对比度特征稳健且稳定。此外，比吸收率随翻转角减小而显著降低。
在3T B0场强下，使用50度的翻转角可显著增加T1自旋回波脑扫描中的灰质与白质对比度。
