眼眶MR成像IDEAL技术脂肪抑制效果和图像质量评价研究

Study of fat suppression effect and image quality of orbital MRI using IDEAL technique

目的:对比分析眼眶三点法非对称回波水脂分离成像(IDEAL)与短反转时间反转恢复序列(STIR)和化学饱和法的脂肪抑制效果和图像质量,探讨IDEAL在眼眶成像中的应用价值。方法:共260例患者进行眼眶MRI扫描,包括143例分别采用化学饱和法(41例)、STIR(52例)和IDEAL(50例)序列行冠状面T2WI,以及50例和67例分别采用化学饱和法和IDEAL序列行增强后冠状面T1WI扫描。对眼眶、鼻窦各解剖部位的图像质量和脂肪抑制效果进行主观评分,并且测量颞肌、内直肌和外直肌的信噪比,比较三种脂肪抑制技术的脂肪抑制效果和图像质量。结果:IDEAL组T2WI对外直肌、内直肌、视神经和海绵窦的图像质量评分高于化学饱和法T2WI(P<0.05),对眼眶及邻近骨骼的脂肪抑制效果评分高于化学饱和法T2WI(P<0.05),但对颞肌间隙脂肪抑制效果的评分低于化学饱和法T2WI(P=0.004)。IDEAL T2WI对眼外肌、视神经、海绵窦的图像质量评分高于STIR序列(P<0.05),对鼻甲、上颌窦内壁的图像质量评分低于STIR序列(P<0.05);对眼眶、蝶骨大翼和颧骨的脂肪抑制效果评分高于STIR序列(P<0.05),对颞肌间隙脂肪抑制效果评分低于STIR序列(P=0.000)。IDEAL T2WI上颞肌的信噪比高于化学饱和法T2WI(P=0.013),颞肌、内直肌和外直肌的信噪比高于STIR序列(P=0.000)。增强后IDEAL T1WI对内直肌、下直肌、上颌窦内壁的图像质量评分高于化学饱和法T1WI(P<0.05),对中鼻甲的图像质量评分低于化学饱和法(P<0.05);对颞肌间隙和翼腭窝的脂肪抑制效果评分高于化学饱和法(P<0.05),对肌锥外间隙脂肪抑制效果评分低于化学饱和法(P<0.05)。结论:IDEAL对眶内及眶周结构的显示效果优于化学饱和法和STIR序列,是目前眼眶MRI的最佳脂肪抑制技术。

Objective： To study the value of iterative Dixon water-fat separation with echo asymmetry and least- squares estimation （IDEAL） technique in orbital MRI by comparing its effect of fat suppression and image quality with short TI inversion recovery （STIR） sequence and frequency-selective fat saturation （FS） sequence. Methods： 143 patients were divided into three groups to undergo coronal orbital T2 WI using three fat-suppression techniques.. FS sequence in 41 cases,STIR sequence in 52 cases,IDEAL sequence in 50 cases;and then 67 cases were selected to be performed with con- trast enhanced IDEAl. T1WI,and 50 cases with contrast enhanced FS T1 WI. Subjective scores were applied to compare the image quality and fat suppression effect of these sequences. The signal intensity and signal-noise ratio （SNR） of temporalis muscle,medial rectus muscle and lateral rectus muscle in these sequences were measured and compared. Results： On IDEAL T2 WI, the image quality scores of lateral rectus, medial rectus, optic nerve, and cavernous sinus were higher than those on FS T2WI （P〈0.05） ,fat suppression effect of orbit and adjacent bones were better than that on FS T2WI （P〈0.05） ,and fat suppression effect of tempral space was lower than that on FS T2 WI （P= 0. 004）. Compared with STIR, IDEAL T2 WI showed higher image quality scores of extraocular muscles,optic nerve and cavernous sinus, and lower scores of turbinates and the media wall of maxillary sinus （P〈0.05）. The fat suppression effect score of orbit, greater wing of sphenoid bone and malar bone was higher, and the score of tempral space was lower on IDEAL T2WI than those on STIR T2WI （P〈0.05）. The SNR of temporalis on IDEAL T2WI was higher than that on FS TzWI （P=0. 013）. The SNR of temporalis,me- dial rectus and lateral rectus on IDEAL T2 WI was higher than that on STIR （P= 0. 000）. On postcontrast T, WI, compared with FS group,IDEAL group showed higher image quality scores in medial rectus,inferior rectus, and media wall of maxil lary sinus, lower image quality scores in middle terbinate, and higher fat suppression effect scores of temporal region and pterygopalatine fossa and lower suppression effect scores of extraconal space （P〈0.05）. Conclusion： The fat suppression effect and image quality of IDEAL technique are superior to those of FS and STIR sequence,IDEAL may be the optimal fat suppression method in orbital MRI.