Department of Medical Imaging, From the University of Ottawa, Ottawa Hospital, Ottawa, Ontario, Canada.
Department of Radiology, Michigan University, Ann Arbor, Michigan, USA.
J Magn Reson Imaging. 2019 Apr;49(4):917-926. doi: 10.1002/jmri.26542. Epub 2019 Jan 28.
This article proposes a consensus nomenclature for fat-containing renal and adrenal masses at MRI to reduce variability, improve understanding, and enhance communication when describing imaging findings. The MRI appearance of "macroscopic fat" occurs due to a sufficient number of aggregated adipocytes and results in one or more of: 1) intratumoral signal intensity (SI) loss using fat-suppression techniques, or 2) chemical shift artifact of the second kind causing linear or curvilinear India-ink (etching) artifact within or at the periphery of a mass at macroscopic fat-water interfaces. "Macroscopic fat" is most commonly observed in adrenal myelolipoma and renal angiomyolipoma (AML) and only rarely encountered in other adrenal cortical tumors and renal cell carcinomas (RCC). Nonlinear noncurvilinear signal intensity loss on opposed-phase (OP) compared with in-phase (IP) chemical shift MRI (CSI) may be referred to as "microscopic fat" and is due to: a) an insufficient amount of adipocytes, or b) the presence of fat within tumor cells. Determining whether the signal intensity loss observed on CSI is due to insufficient adipocytes or fat within tumor cells cannot be accomplished using CSI alone; however, it can be inferred when other imaging features strongly suggest a particular diagnosis. Fat-poor AML are homogeneously hypointense on T -weighted (T W) imaging and avidly enhancing; signal intensity loss at OP CSI is uncommon, but when present is usually focal and is caused by an insufficient number of adipocytes within adjacent voxels. Conversely, clear-cell RCC are heterogeneously hyperintense on T W imaging and avidly enhancing, with the signal intensity loss observed on OP CSI being typically diffuse and due to fat within tumor cells. Adrenal adenomas, adrenal cortical carcinoma, and adrenal metastases from fat-containing primary malignancies also show signal intensity loss on OP CSI due to fat within tumor cells and not from intratumoral adipocytes. Level of Evidence: 5 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2019;49:917-926.
这篇文章提出了一个磁共振成像中含脂性肾和肾上腺肿块的共识命名法，以减少变异性，提高理解，并在描述成像结果时增强沟通。“宏观脂肪”的 MRI 表现是由于聚集的脂肪细胞数量足够多，导致：1）使用脂肪抑制技术的肿瘤内信号强度（SI）损失，或 2）第二类化学位移伪影导致在宏观脂肪-水界面内或周围的肿块中出现线性或曲线状印度墨水（蚀刻）伪影。“宏观脂肪”最常见于肾上腺髓样脂肪瘤和肾血管平滑肌脂肪瘤（AML），仅在其他肾上腺皮质肿瘤和肾细胞癌（RCC）中很少见。反相位（OP）与同相位（IP）化学位移磁共振成像（CSI）相比，非线性非曲线信号强度损失可称为“微观脂肪”，这是由于：a）脂肪细胞数量不足，或 b）肿瘤细胞内存在脂肪。仅使用 CSI 无法确定在 CSI 上观察到的信号强度损失是由于脂肪细胞内的脂肪细胞不足还是脂肪细胞不足，但当其他成像特征强烈提示特定诊断时，可以推断出来。脂肪贫乏的 AML 在 T 加权（T W）成像上呈均匀低信号，并且强烈增强；OP CSI 上的信号强度损失不常见，但当存在时，通常是局灶性的，并且是由于相邻体素中脂肪细胞数量不足引起的。相反，透明细胞 RCC 在 T W 成像上呈异质性高信号，并且强烈增强，OP CSI 上观察到的信号强度损失通常是弥漫性的，并且是由于肿瘤细胞内的脂肪引起的。含脂肪的原发性恶性肿瘤的肾上腺腺瘤、肾上腺皮质癌和肾上腺转移瘤也由于肿瘤细胞内的脂肪而不是肿瘤内的脂肪细胞在 OP CSI 上显示信号强度损失。证据水平：5 技术功效阶段：3 J. Magn. Reson. Imaging 2019;49:917-926。
