国产低场强磁共振设备脂肪抑制技术的应用研究

Study of fat suppression technique using domestic low field strength MR equipment

目的寻找国产低场磁共振设备（ＡＳＭ０．１６Ｔ）脂肪抑制的成像参数，并了解其在临床上的应用效果。方法应用动物组织样本１０块及２０例健康志愿者的头颅和上腹部各进行２次独立的ＳＥ序列扫描，然后行对应区域的脂肪组织信号强度（Ｓ）测量，最后代入Ｔ１值计算公式：Ｓ′／Ｓ″＝（１－ｅＴＲ′／Ｔ１）／（１－ｅＴＲ″／Ｔ１），分别求得标本及志愿者的脂肪组织Ｔ１值为１１３±８毫秒和１３５±１１毫秒。我们以ＴＩ（反转时间）等于６９％Ｔ１作为中心零点时间行短ＴＩ反转恢复序列（ｓｈｏｒｔＴＩｉｎｖｅｒｓｉｏｎｒｅｃｏｖｅｒｙ，ＳＴＩＲ）扫描，同时行ＳＥ序列Ｔ１ＷＩ及Ｔ２ＷＩ。然后通过脂肪信号强度差异及线形灰度曲线进行检测脂肪抑制效果。结果ＳＥＴ１ＷＩ、Ｔ２ＷＩ和ＳＴＩＲ（ＴＩ９０毫秒时）志愿者的脂肪信号强度分别为：３４０８±１６５、２８９９±１８８和３０５±１０６，并且，ＳＴＩＲ（ＴＩ９０毫秒时）的脾／肝和脑灰／白质对比度噪声比较常规ＳＥ序列明显增高（除ＳＥＴ２ＷＩ脾／肝Ｐ＜０．０５外，余Ｐ＜０．０１）。结论ＳＴＩＲ（ＴＩ９０毫秒时）在检测中综合指标最优，从而认定０．１６Ｔ场强下的脂肪抑制零点时间为９０毫秒。

Purpose To find out the imaging parameter of fat suppression for domestic low field MR equipment (ASM 0.16T) and study its clinical effect. Methods Ten slab samples with skin and subcutaneous fat from pigs and the head and upper abdomen of 20 volunteers were scanned twice using SE sequence respectively, and then the signal intensity(S) of fat tissue in the corresponding areas were measured and put into the T 1 calculation formula: S′/S″=(1-e -TR′/T 1 )/(1-e -TR″/T 1 ). The calculated T 1 values of fat tissues of the sample and the volunteers were 113±8ms and 135±11ms respectively. STIR(short TI inversion recovery) sequence scan was done using the parameter TI=69% T 1 as the central zero time, at the same time T 1WI and T 2WI of SE sequence also were performed. Results On T 1WI, T 2WI and STIR(TI 90ms) imaging, the signal intensity of fat tissue of the volunteers were 3 408±165, 2 899±188 and 305±106 respectively. Furthermore, on STIR(TI 90ms) imaging the contrast to noise ratio of spleen/liver and gray matter/white matter were much higher than those on SE imaging( P <0.01,except on SE T 2WI P <0.05). Conclusion The comprehensive indices of STIR(TI 90ms) were the best in the test, so it was confirmed that the zero time of fat suppression was 90ms on 0.16T magnetic field.