小(<4 cm)肾肿块：利用磁共振成像对无可见脂肪的血管平滑肌脂肪瘤与肾细胞癌进行鉴别。
Small (<4 cm) renal mass: differentiation of angiomyolipoma without visible fat from renal cell carcinoma utilizing MR imaging.
机构信息
Department of Radiology, Mayo Clinic, Rochester, MN 55905, USA.
出版信息
Radiology. 2012 Apr;263(1):160-8. doi: 10.1148/radiol.12111205. Epub 2012 Feb 17.
PURPOSE
To determine whether a combination of magnetic resonance (MR) parameters can help differentiate small angiomyolipomas (AMLs) without visible fat from renal cell carcinomas (RCCs).
MATERIALS AND METHODS
This HIPAA-compliant retrospective study received institutional review board approval; 69 men and 42 women (mean age, 59.7 years) with 15 AMLs without visible fat and 104 RCCs underwent MR. The development set consisted of 10 AMLs and 71 RCCs; the validation set consisted of five AMLs and 33 RCCs. T1-weighted fast spin-echo (SE), fat-suppressed T2-weighted fast SE, in- and opposed-phase gradient-echo (GRE), and fat-suppressed three-dimensional T1-weighted spoiled GRE sequences were performed before and after contrast material administration. Tumor signal intensity (SI) was measured. T1 and T2 SI ratio (ratio of tumor to renal cortex SI on T1- and T2-weighted images, respectively), SI index (SII) ([SI(in) 2 SI(opp)]/[SI(in)] × 100; SI(in) and SI(opp) are tumor SI on in- and opposed-phase images, respectively), and arterial-to-delayed enhancement ratio ([SI(art) 2 SI(pre)]/[SI(del) 2 SI(pre)]; SI(pre), SI(art), and SI(del) are tumor SI on unenhanced, arterial phase, and delayed phase three-dimensional T1-weighted spoiled GRE images, respectively) were compared. Combinations of MR parameter threshold levels were constructed from development set and validated with validation set. Sensitivity, specificity, and accuracy for differentiating between AML and RCC were calculated for combinations of MR parameter threshold levels.
RESULTS
AML had significantly higher T1 SI ratio (P = .04), lower T2 SI ratio (P = .001), higher SII (P = .02), and higher arterial-to-delayed enhancement ratio (P < .001) than RCC. Sensitivity, specificity, and accuracy for combination of T2 SI ratio less than 0.9 and ([SII greater than 20% and T1 SI ratio greater than 1.2] or arterial-to-delayed enhancement ratio greater than 1.5) were 73% (11 of 15), 99% (103 of 104), and 96% (114 of 119), respectively, for differentiating AML from RCC.
CONCLUSION
A combination of T2 SI ratio less than 0.9 and ([SII greater than 20% and T1 SI ratio greater than 1.2] or arterial-to-delayed enhancement ratio greater than 1.5) was accurate in differentiating AML from RCC.
目的
旨在确定磁共振（MR）参数组合是否有助于鉴别无可见脂肪的小血管平滑肌脂肪瘤（AML）与肾细胞癌（RCC）。
材料与方法
本 HIPAA 合规性回顾性研究获得了机构审查委员会的批准；共纳入 15 例无可见脂肪的 AML 和 104 例 RCC 患者，其中 69 例男性和 42 例女性，平均年龄为 59.7 岁。将研究对象分为开发集（包含 10 例 AML 和 71 例 RCC）和验证集（包含 5 例 AML 和 33 例 RCC）。所有患者均接受了 MR 平扫及钆对比剂增强检查，包括 T1 加权快速自旋回波（SE）、脂肪抑制 T2 加权快速 SE、同反相位梯度回波（GRE）以及脂肪抑制三维 T1 加权扰相 GRE 序列。测量肿瘤信号强度（SI）。分别测量 T1 和 T2 SI 比值（T1 和 T2 加权图像上肿瘤与肾皮质的 SI 比值）、SI 指数（SII）〔[SI(in)2 SI(opp)]/[SI(in)]×100；SI(in)和 SI(opp)分别为同反相位图像上的肿瘤 SI〕以及动脉期到延迟期强化比值〔[SI(art)2 SI(pre)]/[SI(del)2 SI(pre)]；SI(pre)、SI(art)和 SI(del)分别为未增强、动脉期和延迟期三维 T1 加权扰相 GRE 图像上的肿瘤 SI〕。采用开发集构建 MR 参数阈值水平组合，并使用验证集进行验证。计算用于鉴别 AML 和 RCC 的 MR 参数阈值水平组合的灵敏度、特异度和准确性。
结果
与 RCC 相比，AML 的 T1 SI 比值更高（P =.04），T2 SI 比值更低（P =.001），SII 更高（P =.02），动脉期到延迟期强化比值更高（P <.001）。用于鉴别 AML 和 RCC 的 T2 SI 比值＜0.9 联合〔SII＞20%且 T1 SI 比值＞1.2 或动脉期到延迟期强化比值＞1.5〕组合的灵敏度、特异度和准确性分别为 73%（15 例中的 11 例）、99%（104 例中的 103 例）和 96%（119 例中的 114 例）。
结论
T2 SI 比值＜0.9 联合〔SII＞20%且 T1 SI 比值＞1.2 或动脉期到延迟期强化比值＞1.5〕组合在鉴别 AML 和 RCC 方面具有较高的准确性。
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