Acharya Sudeep, Goyal Ankur, Bhalla Ashu Seith, Sharma Raju, Seth Amlesh, Gupta Arun Kumar
Department of Radiodiagnosis, All India Institute of Medical Sciences (AIIMS), New Delhi, India.
Department of Radiodiagnosis, All India Institute of Medical Sciences (AIIMS), New Delhi, India
Acta Radiol. 2015 Jul;56(7):881-9. doi: 10.1177/0284185114538251. Epub 2014 Jun 17.
The role of dual-energy computed tomography (DECT) in characterization of urinary calculi is evolving and literature regarding differentiation of calcium calculi is sparse and confounding.
To evaluate the capability of DECT in assessing the urinary calculi composition in vivo, especially in differentiating various types of calcium calculi.
One hundred and twenty patients underwent DECT for characterization of urinary calculi. Seventy patients with 114 calculi, including 93 calcium stones, were retrospectively analyzed. DE ratios and attenuation differences were compared using ANOVA and receiver-operating-characteristic (ROC) analysis was done to predict cut-off values, in particular for detecting calcium-oxalate-monohydrate (COM) stones.
DE ratio ≤1.14 accurately detected uric acid calculi, ≥1.29 was definitive for calcium and intermediate values were characteristic of cystine stones. DE ratios were significantly different between group 1 (COM [n = 32]; mean 1.376 ± 0.041), group 2 ([calcium oxalate dihydrate (COD) + COM] [n = 51]; 1.416 ± 0.048), and group 3 ([carbonate apatite (CaP) + COD + COM] [n = 10]; 1.468 ± 0.038) (group 1 vs. 2, P = 0.001; 1 vs. 3, P = 0.000; 2 vs. 3, P = 0.004). More importantly, pure COM calculi (group 1) had significantly lower DE ratio compared with mixed calcium calculi (groups 2 and 3) (P = 0.000). Attenuation differences (between low and high kV images) could not distinguish between COM and mixed calculi. ROC analysis for detection of COM calculi yielded AUC of 0.770 with cut-off DE ratio 1.385 (sensitivity 65.6%, specificity 82%) and value <1.335 was seen only with COM calculi (100% specificity).
DECT can be employed for in vivo differentiation of various types of calculi and for detection of relatively lithotripsy-resistant COM calculi.
双能计算机断层扫描（DECT）在尿路结石特征分析中的作用不断发展，而关于钙结石鉴别诊断的文献稀少且存在混淆。
评估DECT在体内评估尿路结石成分的能力，尤其是区分各种类型的钙结石。
120例患者接受DECT以分析尿路结石特征。对70例患者的114枚结石（包括93枚钙结石）进行回顾性分析。采用方差分析比较双能比（DE ratio）和衰减差异，并进行受试者操作特征（ROC）分析以预测临界值，特别是用于检测一水草酸钙（COM）结石。
DE比≤1.14可准确检测尿酸结石，≥1.29可确诊为钙结石，中间值为胱氨酸结石特征。第1组（COM[n = 32]；平均值1.376±0.041）、第2组（[二水草酸钙（COD）+COM][n = 51]；1.416±0.048）和第3组（[碳酸磷灰石（CaP）+COD+COM][n = 10]；1.468±0.038）之间的DE比有显著差异（第1组与第2组，P = 0.001；第1组与第3组，P = 0.000；第2组与第3组，P = 0.004）。更重要的是，纯COM结石（第1组）的DE比显著低于混合钙结石（第2组和第3组）（P = 0.000）。低千伏和高千伏图像之间的衰减差异无法区分COM结石和混合结石。检测COM结石的ROC分析得出曲线下面积（AUC）为0.770，临界DE比为1.385（灵敏度65.6%，特异性82%），仅COM结石出现值<1.335（特异性100%）。
DECT可用于体内区分各种类型的结石，并检测相对抗碎石的COM结石。
