眼内异物MRI临床应用研究

Clinical application of MRI in intraocular foreign bodies 

ChengJingliang RenCuiping Zhangyan etal.*  Department of Radiology, the First Affiliated Hospital of Zhengzhou University,Zhengzhou  450052

     Abstract   Purpose: To evaluate MRI in intraocular foreign bodies as compared with CT as well as conventional X-ray films. Materials and methods: There were 55 intraocular foreign bodies in 42 patients, 33 males and 9 females age ranged from 5～45 years. Fifty-three of the 55 foreign bodies were non-magnetic, and the remaining 2 were ferromagnetic objects. Conventional X-ray films, CT and MRI examinations were accomplished within one month. Results: (1) The positive rate for showing 55 intraocular foreign bodies was similar on MRI (94％) and CT (91％) (P>0. 25), but much higher than conventional X-ray films (42％) (P<0.005); (2) MRI was superior to CT for the demonstration of eye complications related to the foreign bodies, but the contrary was true when they were located within the sclera; (3) T2WI and PDWI of SE sequence were the method of choice for the demonstration of these foreign bodies; (4) non-magnetic foreign bodies usually showed signal loss without artifact on MRI, while ferromagnetic substances produced remarkable artifact and might lead to accidental injury of the eye. Conclusion: MRI was an effective method for the evaluation of non- magnetic foreign bodies of the eye, especially for the non-metallic foreign bodies undetectable with CT or conventional X-ray film. It was not recommended for ferromagnetic foreign bodies.

 Key words  Intraocular foreign bodied   Magnetic resonance imaging    Tomography, X-ray computed

眼内异物是眼穿孔伤的常见合并症，应尽早取出。其准确定位是手术摘除成败的关键。X线平片、CT和超声是检出眼内异物的重要方法，但均有一定局限性^[1]。MRI为眼内异物检出提供了新方法。笔者对42例眼内异物MRI资料进行分析，并与X线平片和CT比较，旨在探讨MRI对眼内异物的诊断价值。

材料与方法

42例眼内异物累及48只眼，其中单眼异物36例，双眼异物6例。男33例，女9例。年龄5～45岁，平均27岁。伤后至MR检查为2天至15个月。手术前1个月内均作患眼X线平片、CT和MR检查，共检出异物55枚，全部手术取出。对可疑铁磁性异物者，MRI前在B超导引下行磁性试验^[2]，无异物移动时再行 MR检查。采用的统计学方法均为X2检验。

X线平片包括患眼标准正侧位片。用第三代CT进行扫描，均有横轴面图像，少数有冠状面扫描，层厚2-3mm。使用Siemens 1.0T超导MR系统。选用SE序列，分别用头线圈(31例)和眼表面线圈(11例)扫描，层厚2mm，矩阵256×256。均做横轴面、冠状面和矢状面扫描。横轴面以听眦线为基线，冠状面与角膜缘平面平行或与人体正中矢状面垂直，矢状面与角膜缘平面垂直。均有T1WI(TR 400～600毫秒，TE 15毫秒)、PDWI(质子密度加权成像) (TR 1800～2500毫秒，TE 15～20毫秒)和 T2WI(TR 1800—2500毫秒，TE 80～90毫秒)。

结    果

55枚眼内异物种类、数目、大小以及MRI、 CT和X线平片检出情况见表1。MRI和CT对55枚眼内异物检出率分别为94％(52／55)和91％(50／55)，统计学上无显著性差异(P> 0.25)，但均明显高于X线平片的检出率42％ (23／55)(P<0.005)。53枚非磁性异物的眼内分布、MRI和CT显示情况见表2。T1WI 2寸53枚非磁性异物的检出率(25％，13／53)明显低于 T2WI(94％，50／53)和PDWI(91％，48／53) (P<0P005)。T2WI、PDWI和CT(93％，49／53)对53枚非磁性眼内异物检出率相近(P> 0.05)。

MRI检出玻璃体出血10只眼，其中7只眼合并增殖性玻璃体视网膜病变。眼内炎5只眼，均伴有增殖性玻璃体视网膜病变。铜异物致眼内无菌性炎症4只眼。MRI显示19只眼眼内异物有合并症，CT仅显示7只眼有不同程度玻璃体混浊。MRI和CT对眼部合并症的显示率分别为40％(19／48)和15％(7／48)，具有显著性差异(P<0.025)。患眼萎缩8只，CT和 MRI均很好显示。

表1   眼内异物类别、数目、大小及MRI、CT和X线平片检出情况