眼眶病变的SPIR磁共振成像

SPIR MR Imaging of Orbital Lesions

目的：评价ＳＰＩＲ（用于化学位移脂肪抑制的频谱预饱和反转复位技术）与造影增强联合应用在眼眶病变判断中的作用。材料和方法：２０例眼眶病变患者在Ｇｄ－ＤＴＰＡ增强前后，分别采用Ｔ１加权ＳＰＩＲ技术（飞利浦ＡＣＳＧｙ－ｒｏｓｃａｎ），以四级评分系统与常规Ｔ１加权和Ｔ２加权图像作比较。５例无眼眶病变者用来研究正常眼眶解剖。结果：由于高信号脂肪和正常结构的平均容积加上化学性位移伪影在常规ＭＲＩ图像上难以清楚地勾画出眼眶解剖结构。ＳＰＩＲ图像能清晰显示不能增强的视神经和能显著强化的眼直肌群和泪腺。ＳＰＩＲ技术在眼眶病变的判断中较常规ＭＲＩ图像为优。结论：ＳＰＩＲ技术与Ｇｄ－ＤＴＰＡ注射联合应用，在显示眼眶解剖上要优于常规ＭＲＩ。它增强了强化病变的显著性，应常规应用于眼眶病变检查。因此，增强后的ＳＮＲ能替代增强后的Ｔ１加权图像。ＳＰＩＲ的不利是由于气－骨界面信号衰减伪影的出现。

Purpose: To evaluate the role of SPIR (a chemical shift fat suppression technique) in the evaluation of orbital lesions, especially when used in conjunction with contrast enhancement.Materials and Methods: Twenty patients with orbital pathology were studied with TI weighted SPIR technique prior to and following the injection of gadolinium using the Philips ACS Gyroscan.Comparison is made with conventional T1-weighted and T2-weighted images using a four point grading system. Five patients without orbital pathology were also studied to define normal anatomy. Results: Due to volume averaging of high signal fat and normal structures in addition to chemical shift artifact, it is difficult to sharply define the normal orbital anatomy on conventional MR images. SPIR images clearly show the optic nerve, which does not enhance, and rectus muscles and lacrimal glands, which enhance intensely. SPIR technique is superior to conventional MR images in the evaluation of orbital lesions. Conclusion: SPIR technique, in conjunction with gadolinium injection, is superior to conventional MR in defining normal anatomy of the orbit. SPIR increases the conspicuity of enhancing lesions and should be used routinely in evaluating orbital lesings. Accordingly, postcontrast SPIR more than amply replaces postcontrast TI weighted images. A disadvantage is the presence of artifact due to signal loss at air bone interfaces.