Department of Radiology, Coimbra University Hospital, Praceta Mota Pinto/Av. Bissaya Barreto, Coimbra, Portugal.
Radiographics. 2010 Jan;30(1):e38. doi: 10.1148/rg.e38. Epub 2009 Nov 9.
The vast majority of focal liver lesions are hyperintense on T2-weighted magnetic resonance (MR) images. Rarely, however, hepatic nodules may appear totally or partially hypointense on those images. Causes for this uncommon appearance include deposition of iron, calcium, or copper and are related to the presence of blood degradation products, macromolecules, coagulative necrosis, and other conditions. Although rare, low signal intensity relative to surrounding liver on T2-weighted images may be seen in a wide spectrum of lesions. Examples include cases of focal nodular hyperplasia, hepatocellular adenoma, hepatocellular carcinoma, metastases, leiomyoma, siderotic or dysplastic nodules, nodules in Wilson disease, granuloma, and hydatid cyst. On fat-suppressed T2-weighted images, nodules with a lipomatous component, such as lipoma, angiomyolipoma, hepatocellular adenoma, and hepatocellular carcinoma may also appear partially or totally hypointense. The conjunction of other MR imaging findings and their integration in the clinical setting may allow a correct diagnosis in a considerable proportion of cases. The cause for T2-weighted hypointensity may not be, however, always recognized, and only pathologic correlation may provide the answer. The aims of this work are to discuss the causes and mechanisms of hypointensity of liver lesions on T2-weighted images and proposing an algorithm for classification that may be useful as a quick reminder for the interested reader.
绝大多数局灶性肝病变在 T2 加权磁共振（MR）图像上呈高信号。然而，很少有肝结节在这些图像上表现为完全或部分低信号。这种不常见表现的原因包括铁、钙或铜的沉积，与血液降解产物、大分子、凝固性坏死和其他情况的存在有关。尽管罕见，但在 T2 加权图像上与周围肝脏相比，低信号强度可能出现在广泛的病变中。例如，局灶性结节性增生、肝细胞腺瘤、肝细胞癌、转移瘤、平滑肌瘤、铁质或发育不良结节、Wilson 病中的结节、肉芽肿和包虫囊肿。在脂肪抑制 T2 加权图像上，具有脂肪成分的结节，如脂肪瘤、血管平滑肌脂肪瘤、肝细胞腺瘤和肝细胞癌，也可能部分或完全呈低信号。其他磁共振成像表现的结合及其在临床环境中的整合，可能使相当一部分病例能够做出正确的诊断。然而，T2 加权低信号的原因并非总是能够识别，只有病理相关性才能提供答案。本研究的目的是讨论 T2 加权图像上肝病变低信号的原因和机制，并提出一种分类算法，该算法可作为有兴趣的读者的快速提示。
