能谱CT成像在肾积水和单纯性肾囊肿鉴别中的应用价值

Value of spectral CT imaging on identifying hydronephrosis and simple renal cysts

目的初步探讨能谱CT扫描在肾积水与单纯性肾囊肿鉴别诊断中的应用价值。方法回顾性分析2015年6月至2016年5月在我院行能谱CT扫描的肾积水和单纯性肾囊肿患者60例(肾积水31例,单纯性肾囊肿28例,肾积水合并囊肿1例)。所有患者行能谱CT扫描,数据传入图像后处理工作站,获得两组病例的混合能量图像、40~140 ke V单能量图像、能谱衰减曲线图、钙-水基图、水-钙基图、有效原子序数图,对比两组病例混合能量及在不同ke V水平下单能量图像的CT值差异;获得钙-水浓度、水-钙浓度,有效原子序数及等能谱成像特征参数,并根据公式:斜率K=(HU40-HU100)/60计算出各感兴趣区的能谱曲线斜率,对比两组病例钙-水浓度、水-钙浓度、有效原子序数、能谱曲线斜率等参数的差异。所得数据均进行独立样本t检验,绘制ROC曲线,比较各参数鉴别肾积水和单纯性肾囊肿的敏感性和特异性。结果肾积水混合能量CT值(10.60±3.20)HU,略大于单纯性肾囊肿CT值(9.25±2.77)HU,但差异无统计学意义(t=1.751,P=0.085)。肾积水单能量图像CT值在低能量端(40~70ke V)大于肾囊肿,差别有统计学意义,在40 ke V时,单能量CT值差别最大。肾积水的能谱曲线斜率(0.65±0.25)明显大于单纯性肾囊肿(0.36±0.19),差异有统计学意义(t=5.102,P=0.000)。肾积水组水-钙浓度值(996.40±7.16)g/L低于单纯性肾囊肿(999.59±6.62)g/L,差异无统计学意义(t=-1.798,P=0.077)。肾积水组钙-水浓度值(7.28±2.64)g/L明显高于单纯性肾囊肿(4.95±2.41)g/L,差异有统计学意义(t=3.593,P=0.001)。肾积水组有效原子序数值(7.91±0.13)明显高于单纯性肾囊肿(7.61±0.27),差异有统计学意义(t=5.314,P=0.001)。ROC曲线结果显示:能谱曲线和有效原子序数的曲线下面积(AUC)分别为0.825和0.820,对鉴别肾积水和单纯性肾囊肿有一定准确性。结论肾积水与单纯性肾囊肿具有不同的能谱曲线和CT能谱特征参数,能谱CT为鉴别肾积水和单纯性肾囊肿提供了一种有价值的影像学检查方法。

Objective To investigate the diagnostic value of dual energy spectral CT imaging in differentiating hydronephrosis from simple renal cysts. Methods Sixty hydronephrosis and simple renal cysts patients were retrospectively analyzed, including 31 hydronephrosis patients,28 simple renal cysts patients and 1 patient with both two diseases. All the patients were confirmed pathologically and underwent plain CT with spectral imaging mode. Spectral CT related parameters for all the patients above were obtained： 140 kVp image, 40 ~ 140 keV monochromatic spectral image, spectral HU curve, calcium and water concentrations from the material decomposition images and effective-Z. The slope k of the curve was further calculated as K = （HU40- HU100）/60, and results from the two groups were analyzed with independent sam- ples t test. Receiver operating characteristic curves were generated to determine parameters for optimizing sensitivity, specificity and accuracy. Results The CT values on 140 kVp polychromatic images of hydronephrosis was （10. 60 ±3.20）HU, compared with （9. 25 ±2.77）HU of simple renal cysts （t = 1.751 ,P = 0. 085）. There was statistically significance between hydronephrosis and simple renal cysts at low energy （40 -70 keV） monochromatic spectral images, indicating CT values of hydronephrosis was much greater than that of simple renal cysts and the most significance showed at 40 keV. The slope k of the spectral HU curve for hydronephrosis （0. 65 ±0. 25） was statistically higher than that for simple renal cysts （0. 36±0. 19）, （t = 5. 102, P 〈 0. 000 ）. Water （calcium） of hydronephrosis （996. 40± 7. 16, g/L） was lower than that of simple renal cysts （999.59± 6. 62, g/L, t = - 1. 798, P = 0. 077） , and calcium （water） of hydronephrosis （7.28 ± 2.64, g/L） was statistically higher than that of simple renal cysts （4.95 ±2.41, g/L, t =3. 593, P =0. 001 ）. The effective-Z values of hydronephrosis and simple renal cysts were （7.91±0. 13） and （7.61±0.27）, respectively, with significant difference （ t = 5.314, P = 0. 001 ）. Conclusion Spectral CT provides additional parameters for effectively differentiating hydronephrosis from simple renal cysts, compared with conventional CT. Spectral CT could be used to better differentiate these two diseases for further clinical application.