Department of Radiology, Massachusetts General Hospital, 55 Fruit St, Gray 273A, Boston, MA 02114, USA.
Radiology. 2010 Aug;256(2):554-64. doi: 10.1148/radiol.10091956.
To determine whether magnetic resonance (MR) imaging with diffusion-weighted (DW) imaging can help discriminate between radiologically indeterminate benign and malignant orbital masses and to identify optimal apparent diffusion coefficient (ADC) thresholds for such discrimination.
Informed consent was waived for this HIPAA-compliant institutional review board-approved retrospective study. Forty-seven orbital masses imaged with echo-planar DW imaging were identified in 47 patients (25 female patients, 22 male patients; average age, 35 years). A fellowship-trained orbital surgeon determined reference-standard diagnoses on the basis of chart review, and a neuroradiology fellow and senior neuroradiologist who were blinded to the diagnoses selected a region of interest for each lesion by consensus. ADC was calculated from signal intensity on DW images obtained with b = 1000 and b = 0 sec/mm(2). Lesion ADC was also compared with that of normal-appearing white matter (ADC ratio). The Student t test was used to compare groups. Receiver operating characteristic analysis was performed. Intraobserver agreement was assessed with a repeat data collection.
Malignant lesions had lower ADCs than benign lesions, irrespective of patient age (P < .02) and in adults specifically (P < .05). Lymphomas had lower ADCs than pseudotumors (P < .001). An ADC of less than 1.0 x 10(-3) mm(2)/sec and an ADC ratio of less than 1.2 were optimal for predicting malignancy (sensitivity, 63% for both; specificity, 84% and 90%, respectively; and accuracy, 77% and 81%, respectively). Lymphoma was differentiated from pseudotumor with 100% accuracy (in 16 of 16 cases) by using these values. Infiltrative lesions that were hypointense on T2-weighted images were better characterized with DW imaging than lesions that were hyperintense or well defined.
Echo-planar DW MR imaging can help characterize indeterminate orbital masses.
确定磁共振（MR）弥散加权（DW）成像是否有助于区分放射学不确定的良性和恶性眼眶肿块，并确定用于此类区分的最佳表观弥散系数（ADC）阈值。
本 HIPAA 合规的机构审查委员会批准的回顾性研究获得了豁免知情同意。在 47 例患者（25 例女性，22 例男性；平均年龄 35 岁）的眼眶肿块中识别出 47 个接受了 DW 成像的眼眶肿块。一名眼眶外科住院医师根据病历回顾确定了参考标准诊断，一名神经放射学住院医师和一名高级神经放射学医师在不知道诊断的情况下通过共识为每个病变选择了一个感兴趣区。根据 b = 1000 和 b = 0 sec/mm2 获得的 DW 图像上的信号强度计算 ADC。比较病变 ADC 与正常表现的白质（ADC 比）。使用 Student t 检验比较组间差异。进行受试者工作特征分析。通过重复数据采集评估观察者内一致性。
无论患者年龄（P <.02），特别是成年人（P <.05）如何，恶性病变的 ADC 均低于良性病变。淋巴瘤的 ADC 低于假性肿瘤（P <.001）。ADC 小于 1.0 x 10(-3) mm(2)/sec 和 ADC 比小于 1.2 是预测恶性肿瘤的最佳指标（敏感性均为 63%；特异性分别为 84%和 90%；准确性分别为 77%和 81%）。使用这些值，淋巴瘤与假性肿瘤的准确率为 100%（16 例中的 16 例）。在 T2 加权图像上呈低信号的浸润性病变比呈高信号或边界清楚的病变通过 DW 成像更好地得到特征描述。
平面回波 DW MR 成像有助于对不确定的眼眶肿块进行特征描述。
