Boland G W, Lee M J
Department of Radiology, Massachusetts General Hospital, Boston 02114, USA.
Crit Rev Diagn Imaging. 1995;36(2):115-74.
The authors review their experience with magnetic resonance imaging (MRI) of the adrenal gland and discuss the appearance of adrenal diseases where MRI is clinically useful. A basic description of some of the newer pulse sequences is provided. Fat-suppressed MRI is advantageous because of reduction of cardiac and respiratory motion induced artifacts, accentuation of small differences in tissue contrast, and elimination of chemical shift artifacts. These advantages far outweigh the disadvantages of inhomogeneity of fat suppression and the fewer slices obtained per acquisition. Chemical shift imaging is used to differentiate benign from malignant adrenal diseases based on a gradient echo phase cycling technique. Detailed descriptions of MRI findings in adrenal pheochromocytomas, hemorrhage, cysts, adenomas, myelolipomas, and metastases are provided. Most pheochromocytomas appear markedly hyperintense to the liver on T2-weighted images. However, this appearance is not specific as adrenal metastases and adrenal adenomas may occasionally produce a similar appearance. In addition, pheochromocytomas may occasionally be isointense or hypointense to the liver on T2-weighted images. Differentiation of adrenal metastases from adrenal adenomas with MRI is problematic using signal intensity ratios (33% overlap) or T2 calculations. The future of discriminating between adrenal metastases and adenomas may rest with chemical shift MRI, which uses in- and out-of-phase gradient echo pulse sequences for differentiation. This approach relies on the fact that adrenal adenomas contain fat, while adrenal metastases do not. The reported accuracy of chemical shift imaging in differentiating between adrenal adenomas and adrenal metastases ranges from 96 to 100%. An algorithmic approach to differentiating benign from malignant adrenal diseases is presented that relies on an initial noncontrast CT with CT attenuation values obtained from the adrenal mass. If CT attenuation values are less than zero, the mass is characterized as benign. If the mass remains indeterminate after CT, chemical shift MR is performed. If the mass remains indeterminate after MR, biopsy is required.
作者回顾了他们在肾上腺磁共振成像（MRI）方面的经验，并讨论了MRI在临床上有用的肾上腺疾病的表现。提供了一些更新的脉冲序列的基本描述。脂肪抑制MRI具有优势，因为它可以减少心脏和呼吸运动引起的伪影，增强组织对比度的微小差异，并消除化学位移伪影。这些优点远远超过了脂肪抑制不均匀性和每次采集获得的切片较少的缺点。化学位移成像用于基于梯度回波相位循环技术区分良性和恶性肾上腺疾病。文中详细描述了肾上腺嗜铬细胞瘤、出血、囊肿、腺瘤、髓样脂肪瘤和转移瘤的MRI表现。大多数嗜铬细胞瘤在T2加权图像上相对于肝脏呈明显高信号。然而，这种表现并不具有特异性，因为肾上腺转移瘤和肾上腺腺瘤偶尔也可能产生类似的表现。此外，嗜铬细胞瘤在T2加权图像上偶尔相对于肝脏可能呈等信号或低信号。使用信号强度比（33%重叠）或T2计算通过MRI区分肾上腺转移瘤和肾上腺腺瘤存在问题。区分肾上腺转移瘤和腺瘤的未来可能在于化学位移MRI，它使用同相位和反相位梯度回波脉冲序列进行区分。这种方法基于肾上腺腺瘤含有脂肪而肾上腺转移瘤不含脂肪这一事实。据报道，化学位移成像区分肾上腺腺瘤和肾上腺转移瘤的准确率在96%至100%之间。本文提出了一种区分良性和恶性肾上腺疾病肾上腺疾病的算法方法，该方法依赖于最初的非增强CT，并从肾上腺肿块获得CT衰减值。如果CT衰减值小于零，则该肿块被判定为良性。如果在CT检查后肿块仍不明确，则进行化学位移MR检查。如果在MR检查后肿块仍不明确，则需要进行活检。
