Bilbey J H, McLoughlin R F, Kurkjian P S, Wilkins G E, Chan N H, Schmidt N, Singer J
Department of Radiology, St. Paul's Hospital, Vancouver, B.C., Canada.
AJR Am J Roentgenol. 1995 Mar;164(3):637-42. doi: 10.2214/ajr.164.3.7863885.
CT and conventional MR imaging are helpful in characterizing adrenal tumors, but a specific diagnosis is not achieved for a substantial number of lesions. Chemical-shift imaging relies on the different resonance frequencies of protons in water and triglyceride molecules and therefore may permit a more specific diagnosis of adrenal adenomas, which are known to contain abundant lipid. The purpose of this study was to evaluate the usefulness of chemical-shift MR imaging in the differentiation of adrenal adenomas from other adrenal masses.
Forty-one adrenal masses (17 nonhyperfunctioning adenomas, two aldosteronomas, six pheochromocytomas, one ganglioneuroma, five adrenal carcinomas, one lymphoma, seven metastases, one case of extramedullary hematopoiesis, and one leiomyosarcoma) suspected clinically or identified by sonography or CT in 38 patients were prospectively evaluated with MR imaging. Pathologic proof of diagnosis was obtained for 28 lesions, and stability on imaging follow-up (mean, 19 months) was accepted as proof of diagnosis of benign adenoma for 13 lesions. In-phase T1-weighted spin-echo sequences (500/20 [TR/TE]) and opposed-phase gradient-echo sequences (142/6.3, flip angle = 90 degrees) of the adrenal regions were applied. Quantitative analysis of signal intensity loss in the adrenal lesions relative to reference tissues (liver, muscle, and spleen) on in-phase and opposed-phase sequences was done to differentiate adenomas from nonadenomas. Region-of-interest signal intensity measurements were obtained in a standard fashion by selection of the largest possible representative sample.
Using liver as the reference standard, we found that mean signal intensity ratios were 0.47 (range, 0.23-0.97) for adrenal adenomas and 0.88 (range, 0.65-1.32) for nonadenomas; signal intensity ratios for two adenomas overlapped those of the nonadenomas. Using muscle as the reference standard, we found that mean signal intensity ratios were 0.44 (range, 0.22-0.66) for adrenal adenomas and 0.85 (range, 0.59-1.39) for nonadenomas; signal intensity ratios for two adenomas overlapped those of the nonadenomas. Using spleen as the reference standard, we found that mean signal intensity ratios were 0.45 (range, 0.27-0.73) for adrenal adenomas and 0.97 (range, 0.8-1.18) for nonadenomas, with no overlap. The mean signal intensity ratios were significantly different between adenomas and nonadenomas for all three reference tissues (p < .001).
Our results show that chemical-shift MR imaging is an important new technique that enables the differentiation of adrenal adenomas from other adrenal masses, reducing the need for biopsy and prolonged imaging follow-up in patients with adrenal tumors.
CT和传统MR成像有助于肾上腺肿瘤的特征性诊断，但对于相当数量的病变无法做出明确诊断。化学位移成像依赖于水和甘油三酯分子中质子的不同共振频率，因此可能有助于对已知含有丰富脂质的肾上腺腺瘤做出更明确的诊断。本研究的目的是评估化学位移MR成像在鉴别肾上腺腺瘤与其他肾上腺肿块中的作用。
对38例患者中临床怀疑或经超声或CT检查发现的41个肾上腺肿块（17个无功能腺瘤、2个醛固酮瘤、6个嗜铬细胞瘤、1个神经节神经瘤、5个肾上腺皮质癌、1个淋巴瘤、7个转移瘤、1例髓外造血和1个平滑肌肉瘤）进行前瞻性MR成像评估。28个病变获得了病理诊断依据，13个病变在影像学随访（平均19个月）中表现稳定，被视为良性腺瘤的诊断依据。采用肾上腺区域的同相位T1加权自旋回波序列（500/20 [TR/TE]）和反相位梯度回波序列（142/6.3，翻转角 = 90度）。对肾上腺病变相对于参考组织（肝脏、肌肉和脾脏）在同相位和反相位序列上的信号强度损失进行定量分析，以区分腺瘤与非腺瘤。通过选择尽可能大的代表性样本，以标准方式获得感兴趣区域的信号强度测量值。
以肝脏作为参考标准，我们发现肾上腺腺瘤的平均信号强度比为0.47（范围为0.23 - 0.97），非腺瘤的平均信号强度比为0.88（范围为0.65 - 1.32）；两个腺瘤的信号强度比与非腺瘤的信号强度比有重叠。以肌肉作为参考标准，我们发现肾上腺腺瘤的平均信号强度比为0.44（范围为0.22 - 0.66），非腺瘤的平均信号强度比为0.85（范围为0.59 - 1.39）；两个腺瘤的信号强度比与非腺瘤的信号强度比有重叠。以脾脏作为参考标准，我们发现肾上腺腺瘤的平均信号强度比为0.45（范围为0.27 - 0.73），非腺瘤的平均信号强度比为0.97（范围为0.8 - 1.18），无重叠。对于所有三种参考组织，腺瘤与非腺瘤的平均信号强度比差异均有统计学意义（p < .001）。
我们的结果表明，化学位移MR成像是一项重要的新技术，能够鉴别肾上腺腺瘤与其他肾上腺肿块，减少肾上腺肿瘤患者的活检需求和延长的影像学随访时间。
