From the Department of Radiology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, 676 N Saint Clair St, Suite 800, Chicago, IL 60611.
Radiographics. 2016 Mar-Apr;36(2):414-32. doi: 10.1148/rg.2016150139. Epub 2016 Feb 5.
Adrenal lesions are a common imaging finding. The vast majority of adrenal lesions are adenomas, which contain intracytoplasmic (microscopic) fat. It is important to distinguish between adenomas and malignant tumors, and chemical shift magnetic resonance (MR) imaging can be used to accomplish this distinction by depicting the fat in adenomas. Chemical shift imaging is based on the difference in precession frequencies of water and fat molecules, which causes them to be in different relative phases during the acquisition sequence and allows in-phase and opposed-phase images to be obtained. It is important to acquire these images by using the earliest possible echo times, with the opposed-phase echo before the in-phase echo, and by using a single breath hold to preserve diagnostic accuracy. Intracytoplasmic fat is depicted as signal drop on opposed-phase images when compared with in-phase images. Both qualitative and quantitative methods for assessing signal drop are detailed. The appearances of adrenal adenomas and other adrenal tumors on chemical shift MR images are described, and discriminatory ability at chemical shift MR imaging compared with that at adrenal computed tomography (CT) is explained. Other adrenal-related conditions in which chemical shift MR imaging is helpful are also discussed. Chemical shift MR imaging is a robust tool for evaluating adrenal lesions that are indeterminate at nonenhanced CT. However, it is important to know the advantages and disadvantages, including several potential imaging pitfalls. The characterization of adrenal lesions by using chemical shift MR imaging and adrenal CT should always occur in the appropriate clinical setting.
肾上腺病变是一种常见的影像学表现。绝大多数肾上腺病变为含有细胞内（镜下）脂肪的腺瘤。重要的是要区分腺瘤和恶性肿瘤，化学位移磁共振（MR）成像可以通过描绘腺瘤中的脂肪来实现这种区分。化学位移成像是基于水分子和脂肪分子进动频率的差异，这导致它们在采集序列中处于不同的相对相位，并允许获得同相和反相图像。重要的是要通过使用最早可能的回波时间来获取这些图像，反相回波应在同相回波之前，并使用单次屏气以保持诊断准确性。与同相图像相比，细胞内脂肪在反相图像上显示为信号下降。详细描述了评估信号下降的定性和定量方法。描述了化学位移 MR 图像上肾上腺腺瘤和其他肾上腺肿瘤的表现，并解释了化学位移 MR 成像与肾上腺 CT 相比的鉴别能力。还讨论了在其他与肾上腺相关的情况下化学位移 MR 成像有帮助的情况。化学位移 MR 成像 是评估非增强 CT 不确定的肾上腺病变的强大工具。然而，了解其优缺点非常重要，包括几个潜在的成像陷阱。应始终在适当的临床环境中通过化学位移 MR 成像和肾上腺 CT 对肾上腺病变进行特征描述。
