Comprehensive Kidney Stone Center, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
J Urol. 2010 Dec;184(6):2354-9. doi: 10.1016/j.juro.2010.08.011. Epub 2010 Oct 16.
We assessed whether dual energy computerized tomography with advanced post-image processing can accurately differentiate urinary calculi composition in vivo.
A total of 25 patients scheduled to undergo ureteroscopic/percutaneous nephrolithotomy were prospectively identified. Dual energy computerized tomography was performed using 64-slice multidetector computerized tomography. Novel post-processing (DECTSlope) used pixel by pixel analyses to generate data sets grayscale encoding ratios of relative differences in attenuation of low (DECT80 kVp) and high energy (DECT140 kVp) series. Surgical extraction and Fourier spectroscopy resulted in 82 calculi. Of these stones 51 showed minor admixtures (uric acid, ammonium urate, struvite, calcium oxalate monohydrate and brushite) and 31 were polycrystalline (mixtures of calcium oxalate monohydrate/dihydrate and calcium phosphate). Analyses identified stone clusters of equal composition and distinct attenuation descriptors on DECT140 kVp, DECT80 kVp and DECTSlope. Iterative cross-validation of the 3 dual energy computerized tomography data sets was used to identify characteristic attenuation limits for each stone type.
Attenuatio profiles showed substantial overlap among various stones on DECT140 kVp (uric acid 427.3±168.1 HU, ammonium urate 429.9±99.7 HU, struvite 480.2±123.5 HU, calcium oxalate monohydrate 852.4±301.4 HU, brushite 863.7±180.1 HU and polycrystalline 858.1±210.5 HU) and on DECT80 kVp (uric acid 493.6±182.8 HU, ammonium urate 591.5±157.9 HU, struvite 712.4±173.9 HU, calcium oxalate monohydrate 1,240.5±494.7 HU, brushite 1,532.1±273.1 HU and polycrystalline 1,358.7±316.8 HU). Statistically spectral separation was not sufficient to characterize stones unambiguously based on DECT140 kVp/DECT80 kVp attenuation. Analysis of attenuation showed sufficient spectral separation on DECTSlope (uric acid 14.9±10.9 U, ammonium urate 56.1±1.8 U, struvite 42.7±1.4 U, calcium oxalate monohydrate 62.8±1.8 U and brushite 113.2±5.3 U). Polycrystalline stones (51.8±3.7 U) overlapped with struvite and ammonium urate stones. This overlap was resolved as all struvite/ammonium urate stones measured 900 HU or less and all polycrystalline stones measured more than 900 HU on DECT80 kVp.
Dual energy computerized tomography with novel post-processing allows accurate discrimination among main subtypes of urinary calculi in vivo and, thus, may have implications in determining the optimum clinical treatment of urinary calculi from a noninvasive, preoperative radiological assessment.
我们评估了先进的后图像处理的双能计算机断层扫描是否能准确区分体内尿结石成分。
前瞻性地确定了 25 例计划行输尿管镜/经皮肾镜取石术的患者。使用 64 层多层计算机断层扫描进行双能计算机断层扫描。新的后处理（DECTSlope）使用逐像素分析生成数据，灰度编码比值表示低能（DECT80 kVp）和高能（DECT140 kVp）系列衰减的相对差异。手术提取和傅立叶光谱分析得出 82 个结石。其中 51 个结石有少量混合（尿酸、尿酸铵、磷酸镁铵、一水合草酸钙和二水合磷酸氢钙），31 个结石为多晶型（一水合草酸钙/二水合草酸钙和磷酸钙的混合物）。分析确定了在 DECT140 kVp、DECT80 kVp 和 DECTSlope 上具有相同组成和不同衰减特征的结石簇。对 3 个双能计算机断层扫描数据集进行迭代交叉验证，以确定每种结石类型的特征衰减极限。
在 DECT140 kVp（尿酸 427.3±168.1 HU、尿酸铵 429.9±99.7 HU、磷酸镁铵 480.2±123.5 HU、一水合草酸钙 852.4±301.4 HU、二水合磷酸氢钙 863.7±180.1 HU 和多晶型 858.1±210.5 HU）和 DECT80 kVp（尿酸 493.6±182.8 HU、尿酸铵 591.5±157.9 HU、磷酸镁铵 712.4±173.9 HU、一水合草酸钙 1,240.5±494.7 HU、二水合磷酸氢钙 1,532.1±273.1 HU 和多晶型 1,358.7±316.8 HU）上，衰减谱显示出各种结石之间有很大的重叠。基于 DECT140 kVp/DECT80 kVp 衰减，光谱分离不足以明确地对结石进行特征描述。分析衰减表明，在 DECTSlope 上有足够的光谱分离（尿酸 14.9±10.9 U、尿酸铵 56.1±1.8 U、磷酸镁铵 42.7±1.4 U、一水合草酸钙 62.8±1.8 U 和二水合磷酸氢钙 113.2±5.3 U）。多晶型结石（51.8±3.7 U）与磷酸镁铵结石和尿酸铵结石重叠。这种重叠是通过所有磷酸镁铵/尿酸铵结石的 DECT80 kVp 测量值都在 900 HU 或以下，以及所有多晶型结石的测量值都超过 900 HU 来解决的。
具有新型后处理功能的双能计算机断层扫描可以准确地区分体内主要类型的尿结石，因此，可能会影响到通过非侵入性、术前影像学评估来确定尿结石的最佳临床治疗方案。
