Park Sung Hee, Kim Myeong-Jin, Kim Joo Hee, Lim Joon Seok, Kim Ki Whang
Department of Diagnostic Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, 134 Shinchondong, Seodaemungu, Seoul 120-752, Korea.
Korean J Radiol. 2007 Jul-Aug;8(4):328-35. doi: 10.3348/kjr.2007.8.4.328.
To determine the optimal threshold for the attenuation values in unenhanced computed tomography (CT) and assess the value of the size criteria for differentiating between an adrenal adenoma and a nonadenoma.
The unenhanced CT images of 45 patients at our institution, who underwent a surgical resection of an adrenal masses between January 2001 and July 2005, were retrospectively reviewed. Forty-five adrenal masses included 25 cortical adenomas, 12 pheochromocytomas, three lymphomas, and five metastases confirmed by pathology were examined. The CT images were obtained at a slice thickness of 2 mm to 3 mm. The mAs were varied from 100 to 160 and 200 to 280, while the 120 KVp was maintained in all cases. The mean attenuation values of an adrenal adenoma and nonadenoma were compared using an unpaired t test. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy at thresholds of 10 HU, 20 HU, and 25 HU were compared. The diagnostic accuracy according to the size criteria from 2 cm to 6 cm was also compared.
The twenty-five adenomas showed significantly lower (p < 0.05) attenuation values (mean+/-SD; 16.3+/-14.9) than the nonadenomas (38.1+/-6.8). Nineteen (90%) of the 20 nonadenomas had attenuation values ranging from 30 to 50 HU. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for diagnosing adenomas were 36%, 100%, 100%, 56%, and 64%, respectively, at a threshold of 10 HU; 60%, 100%, 100%, 67%, and 78%, respectively, at a threshold of 20 HU; and 72%, 95%, 95%, 73%, and 82%, respectively, at a threshold of 25 HU. The adenomas had a significantly (p < 0.05) smaller diameter (2.44+/-1.24 cm) than the nonadenomas (5.09+/-2.37 cm). The size criteria using a diameter of 4-6 cm showed a sensitivity > 90% but a specificity < 70%. Size criteria of 2 or 3 cm had a high specificity of 100% and 80% but a low sensitivity of 20% and 60%.
The threshold attenuation values of 20 or 25 HU in the unenhanced CT appear optimal for discriminating an adrenal adenoma from a nonadenoma. The size criteria are of little value in differentiating adrenal masses because of their low specificity or low sensitivity.
确定平扫计算机断层扫描（CT）中衰减值的最佳阈值，并评估大小标准在鉴别肾上腺腺瘤与非腺瘤中的价值。
回顾性分析2001年1月至2005年7月在我院接受肾上腺肿块手术切除的45例患者的平扫CT图像。45个肾上腺肿块包括25个皮质腺瘤、12个嗜铬细胞瘤、3个淋巴瘤和5个经病理证实的转移瘤。CT图像层厚为2mm至3mm。管电流（mAs）在100至160以及200至280之间变化，所有病例管电压均保持在120kVp。采用成组t检验比较肾上腺腺瘤和非腺瘤的平均衰减值。比较10HU、20HU和25HU阈值时的敏感性、特异性、阳性预测值、阴性预测值和准确性。还比较了直径2cm至6cm大小标准的诊断准确性。
25个腺瘤的衰减值（均值±标准差；16.3±14.9）显著低于非腺瘤（38.1±6.8）（p<0.05）。20个非腺瘤中有19个（90%）的衰减值在30至50HU之间。在10HU阈值时，诊断腺瘤的敏感性、特异性、阳性预测值、阴性预测值和准确性分别为36%、100%、100%、56%和64%；在20HU阈值时，分别为60%、100%、100%、67%和78%；在25HU阈值时，分别为72%、95%、95%、73%和82%。腺瘤的直径（2.44±1.24cm）显著小于非腺瘤（5.09±2.37cm）（p<0.05）。直径4 - 6cm的大小标准敏感性>90%但特异性<70%。直径2cm或3cm的大小标准特异性分别为100%和80%，但敏感性较低，分别为20%和60%。
平扫CT中20或25HU的阈值衰减值似乎最适合鉴别肾上腺腺瘤与非腺瘤。由于大小标准特异性低或敏感性低，其在鉴别肾上腺肿块方面价值不大。
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