动态增强MRI对眼眶病变诊断及鉴别诊断的价值

目的运用动态增强MR技术，分析病变的强化特点，以提高对不同眼眶病变的认识，尤其是不同良性肿瘤及恶性肿瘤的强化特点，进而提高MRI的诊断价值。方法共41例，均为单发病灶，均行MR检查，术后均得到病理证实。其中良性肿瘤和类肿瘤病变3l例，恶性肿瘤病变10例。使用1．5T超导MR机，头颅线圈采集。MR平扫包括：横断面T1WI、T2WI及T1WI矢状和冠状面扫描。层厚4mm。增强检查为使用对比剂后立即连续动态扫描，以观察病变的动态变化状况。对所测得的平扫及动态增强信号强度值（前、后），计算其强化率（E％）并得到时间-密度曲线（TIC），并进行统计学分析。结果（1）良恶性肿瘤第1分钟内平均强化率（E1％）比较：恶性肿瘤的E1％〉60％，而良性肿瘤的E1％〈60％，二者差异有统计学意义（P〈0．05）；（2）27例良性肿瘤除脑膜瘤外，绝大多数（88．9％，24例）强化为线型；（3）10例恶性肿瘤和3例脑膜瘤为平台型强化。（4）3例炎性假瘤和1例肉芽肿病变，表现为流出型。（5）12例海绵状血管瘤有特殊的强化模式，表现为局部点状和小结节状强化，然后逐步向全肿瘤扩展。结论动态增强MR检查，对鉴别良恶性肿瘤有明显意义；对鉴别肿瘤和炎症也可提供重要的诊断依据；少数病种，如海绵状血管瘤有特殊的强化模式。

The diagnosis of orbital tumor with dynamic contrast-enhanced MRI

Objective To improve the diagnostic value of MRI on orbital diseases,especially on benign and malignant tumors,through analyzing the characteristics of orbital diseases with dynamic contrast-enhanced MRI.Methods Forty-one patients with solitary orbital masses, including 31 benign tumors and 10 malignant tumors,underwent MR examinations. All the cases were verified by pathology.1.5 T MR system and head coil were employed.Conventional scan was performed with axial,sagittal,and coronal T_1WI,as well as axial T_2WI and the slice thickness of 4 mm.After the injection of contrast agents,dynamic contrast-enhanced MRI was immediately performed so as to observe dynamic changes of lesions.Enhancement rates(E%) was calculated and time-intensity curve was portraited according to the signal intensity of conventional scan and dynamic-contrast enhanced scan.SPASS Ver10.0 was used to do the statistical analysis,while cartographies were completed with Powerpoint.Results(1)Comparision between benign and malignant tumors in average enhanced rates of the 1~(st) minute: it was higher than 60% in malignant tumors,while lower than 60% in benign ones(P<0.05).(2)Most of the 27 benign tumors(except meningiomas) demonstrated as Type 1 time-intensity curve(88.9%,n=24).(3) 10 malignant tumors as well as 3 meningiomas demonstrated as plateau type.(4) Wash-out type was detected in(3 inflammatory) pseudotumors and 1 granuloma.(5) 12 cavernous hemangiomas had special enhancing model,demonstrating as punctiform and tuberculous enhancement,which then expanded to the whole tumor.Conclusion Dynamic contrast-enhanced MRI is a valuable method in differentiating malignant and benign tumors.Dynamic contrast-enhanced MRI also plays an important role in the differential diagnosis of tumor and inflammation.Some kinds of diseases,for example cavernous hemangiomas,have special enhancing models.