DECT对尿结石化学成分分析的实验和临床应用研究
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摘要
尿石症(Urolithiasis)是泌尿系统的常见病,且总的发病数仍在不断增加。由于结石的成分不同,其治疗方法的选择及治疗的效果也有很大不同：(1)尿酸结石、胱氨酸结石的首选治疗方法为药物溶石,若能在临床治疗前明确结石的成分,将对提高治疗效果、减少不必要的创伤；(2)感染性的磷酸镁钱结石则容易被冲击波击碎,但碎石后释放的细菌容易引起严重的全身感染,术前明确诊断有助于降低并发症的发生；(3)结石成分分析对于预防结石的复发也具有重要意义。
影像学检查是诊断泌尿系疾病的主要方法,DECT技术除了能准确检测结石外,除区别尿酸结石和非尿酸结石外,并可对其成分进一步分析。本文通过DECT对尿结石化学成分分析的实验和临床应用研究,以期评估DECT对尿石症的化学成分分析和临床鉴别诊断上的可靠性。
第一部分DECT尿结石体外成分分析的实验研究
研究目的评价DECT技术结石化学成分分析的可靠性及其准确性。
材料与方法
1.结石标本的采集：收集南方医院泌尿外科手术后结石89枚,所有结石均为经临床确诊为泌尿系结石的患者行微创经皮肾镜取石(mini-Percutaneousnephro--lithotomy)术后获得；
2.结石标本的包埋与处理：将收集到的结石标本编号,记录颜色、质地,然后将结石标本用蒸馏水洗净,放入烤箱内烘干；清晨在市场购买新鲜猪肾,将猪肾纵面剖开,把标本放入猪肾内,将埋有结石的猪肾置于水中,尽可能排出其中的空气；用保鲜袋捞起后,排出保鲜袋内的水。适当包裹后,供CT扫描使用。
3.CT扫描：使用保鲜袋将带有结石标本的猪肾包裹好,在放在扫描台上,将扫描中心线调整至样本的中心点；常规双肾120KV扫描完成后,进行140/80KV双能量扫描。
3.1设备西门子双源CT扫描机(dual-sourcecomputertomography, DSCT),型号为SOMATOM Definition-mmwpsp02,后处理工作站软件版本为Syngo multimodality AG2008。
3.2扫描条件采用0.6mm层厚无间距扫描；所得的数据经拆薄重建后传至随机工作站进行重建及双能量分析；扫描参数如下表。
3.3图像后处理两位放射科医生通过在随机默认的标准肾脏软组织窗宽、窗位分析结石影像；分别在结石最大横截面积测CT平均值,同一枚结石每位医生测量4次,取所测平均值；进入工作站的双能量分析(Dual Energy)界面选项,导入双能量140/80KV扫描数据,进行双能量结石分析；
4.结石化学成分分析：通过化学的方法对结石标本进行定性分析；将结石分为草酸钙结石、磷酸盐结石、胱氨酸结石、尿酸结石及混合结石(结石均为混合物,且90%以上的结石含有钙盐成分,某成分含量超过50%的结石被定义为某种性质的结石)。
4.1实验器材与试剂泌尿结石成份分析试剂盒及(购自中科院广州化学研究所广州百康生物科技有限公司),另配结石专用陶瓷研磨器(研钵+研磨棒)及试管、金属匙若干。其中试剂盒中化学试剂包括：尿酸试剂Ⅰ、尿酸试剂Ⅱ、铵试剂、磷酸试剂、盐酸试剂(2支)、草酸试剂(2支)、钙镁试剂、镁试剂、胱氨酸试剂Ⅰ,胱氨酸试剂Ⅱ,胱氨酸试剂Ⅲ。
4.2分析方法通过化学的方法对结石标本进行定性分析,可以知道结石含有钙、镁、铵、磷酸盐、尿酸或尿酸盐、草酸盐、胱氨酸等,该种方法虽比较粗糙,但又比较简单易行,基本可以满足临床和科研需要,是目前国内医疗、科研机构通用的结石化学成份鉴定方法。具体操作步骤如下：
1)标本准备：取少量结石(大米粒大小即可),用蒸馏水冲洗干净,放在相应编号的研钵中,自然晾干(一般放置1-2小时)。干燥后,用研磨棒把研钵内结石研成粉末备用；每份结石标本只能用一套研磨器(研钵+研磨棒)
2)分析步骤：用金属小匙取上述结石粉末各1匙,分别置于白板中的3个孔中,及3支试管内,然后依次进行下列步骤。
①尿酸：在有孔白板的第1孔,分别滴入尿酸试剂Ⅰ和尿酸试剂Ⅱ各2滴,呈蓝色为阳性。
②钱盐：在有孔白板的第2孔,滴加钱试剂3滴,如显黄色或者红棕色沉淀为阳性；由于试剂中会含有少量铵离子,会出现假阳性反应,所以实验时应进行空白对照；即在一个空白孔内同样滴加3滴铵试剂,与待测孔进行颜色对照。
③胱氨酸：在有孔白板的第3孔,分别滴入胱氨酸试剂I2滴、胱氨酸试剂Ⅱ1滴、胱氨酸试剂Ⅲ2滴；5分钟后观察,蓝色为阳性。注意：试剂加完后,不宜放置过久,否则会出现假阳性,故一定要在5分钟后观察结果。
④磷酸盐：取第1支试管,滴加磷酸试剂3-4滴,摇匀后静置3分钟,观察结果,溶液呈黄色,或管壁有黄色沉淀为阳性。注意：如果温度低,或显色不明显,可在酒精灯上稍微加热,如加热时有气泡产生,应放置片刻,待气泡消失后再观察结果。
⑤碳酸盐：取第2支试管,将结石粉末放置于小试管内,沿试管壁加入盐酸试剂(3 mol/L盐酸约0.5ml)2滴,振动后放置仔细观察有无气泡产生,有气泡为阳性。
⑥草酸盐：在步骤5)试管中,继续滴加草酸试剂5滴,摇匀。如果出现白色混浊,则为阳性。加试剂Ⅰ约2 ml,加试剂Ⅱ、Ⅲ各2滴渐生蓝色为阳性。
⑦钙盐：取第3支试管,将结石粉末放置于小试管内,滴入盐酸试剂Ⅰ1滴和钙镁试剂3滴,如有白色混浊,则为阳性。⑧镁盐：将步骤7)试管中,继续滴加镁试剂2滴,摇匀,如出现蓝色沉淀,则为阳性。
4.3结果判断
5.统计学分析：
1.所有数据分析采用SPSS 13.0统计软件完成。
2.不同结石的CT值差异进行重复测量数据的方差分析,如有差异,再进一步采用多重比较反复LSD法进行两两比较
3.将分析结果与化学分析法进行两相关样本的非参数检验；计算每种结石利用CT双能量技术进行鉴别诊断的敏感性和特异性。
结果
1.结石种类分布及构成比经化学分析,89枚结石中,其中草酸钙结石53枚(59.55%)、磷酸盐结石17枚(19.10%)、胱氨酸结石7枚(7.86%),尿酸结石4枚(4.49%)；另8枚结石不能通过化学分析法鉴别其种类；
2.结石CT扫描结果平扫及DECT扫描,包括尿酸结石在内的所有尿路结石均被检出；全都清晰显像,其中1例尿酸结石(X线阴性结石)由于体积较小,显示稍差,通过调节窗宽、窗位亦可以获得较好显示；草酸钙结石>磷酸盐结石>胱氨酸结石>尿酸结石,其中草酸钙结石与磷酸盐结石有较多重叠,CT值差异无统计学差异性；除尿酸结石外,非尿酸结石CT值均随着管电压的增高而减低。
3.双能量结石分析所有结石均被在双能量分析软件中被标记,其检出率为100%；其中尿酸结石分析值为负数,被标记为红色；非尿酸结石分析值为正数,被标记为蓝色,与结石化学分析结果完全吻合,尿酸结石的诊断敏感性和特异性均为100%；三种非尿酸结石双能量分析值比较均具有显著统计学差异性。双能量分析结合的CT值对3种非尿酸结石化学成分双能量与化学分析法用两相关样本的非参数检验；其中尿酸结石因在双能量结石分析中被标记为红色,且CT值明显低于其他类型结石,此处仅分析3种非尿酸结石；经化学分析法,鉴定为草酸钙结石有47例,磷酸盐结石有23例；胱氨酸结石有7例；但经双能量分析,认为草酸钙结石有50例,磷酸盐结石有19例,胱氨酸结石有8例。两种方法经比较无显著统计学差异(P=0.703>0.05)；且具有高度关联性。DECT分析法鉴别草酸钙结石的敏感性(sensitivity)为89.36%；特异性(specificity)为83.33%；诊断磷酸盐结石的敏感性为60.87%,特异性为90.74%；诊断胱氨酸结石的敏感性为71.43%,特异性为95.71%。
结论：
1.DECT尿结石分析技术能够进行尿结石的化学成分分析；其中尿酸结石被标记为红色,非尿酸结石标记为蓝色,鉴别尿酸与非尿酸结石的准确率为100%；140/80Kv双能量扫描时,使用CT差值和DEI作为指标,无论是尿酸结石、胱氨酸结石、草酸钙结石、磷酸盐结石,其差异均有显著统计学意义,可以作为鉴别结石化学成分的有效指标,并能够进一步鉴别非尿酸结石。
2.DECT分析法鉴别草酸钙结石的敏感性(sensitivity)为89.36%；特异性(specificity)为83.33%；诊断磷酸盐结石的敏感性为60.87%,特异性为90.74%；诊断胱氨酸结石的敏感性为71.43%,特异性为95.71%；是一种无创的结石成分分析方法。
第二部分DECT在泌尿结石疾病鉴别中的临床应用
研究目的：探讨双肾DECT扫描在诊断结石病方面的诊断价值,从图像质量、信噪比、病变检出及鉴别上的差异,评价其在临床应用的可靠性。
材料与方法：
1.1临床资料：收集我院临床拟诊为的泌尿系结石症患者53例,其中男37例,女16例,年龄18-54岁,平均(34±12)岁；进行增强扫描的患者要求无碘对比剂过敏史、无严重心、肺、肾功能不全、非孕产妇,且所有患者均签署知情同意书；
1.2检查方法：采用Siemens Somatom Definition DSCT进行检查,常规120kv平扫后,进行非增强双能量扫描,参数为：A球管电压140kV,有效电流96mA s,B球管电压80 kV,有效电流404 mAs；平扫结束后采用双筒高压注射器经右侧肘前静脉以3-4.5ml/s流率注射浓度为300 mg/ml的优维显80ml,注射完毕后再以相同流率注射40ml生理盐水,延时25s行动脉期扫描,120s行双能量延迟扫描；所有扫描经自动拆薄重建为层厚0.75 mm的图像传至后处理工作站；
1.3工作站后处理：①取DE composition=0.3,按照140 kV数据70%,与80 kV数据30%的比率,通过特殊计算后融合成120 kV的图像；②将双能延迟扫描数据调入Dual- Energy软件内,启用应用程序内的Liver VNC处理,通过调整CT与碘造影剂的融合比率,将CT的融合比率调节到100%,碘对比剂的融合比率调整到0%,得到VNC数据,再进行MPR等重建；③将非增强双能量扫描数据拆薄重建数据(80kV与140 kV)分别调入工作站Dual Energy软件内,启动应用程序内的Kidneystone处理,进行尿结石双能量分析,其中尿酸结石被标记为红色,非尿酸结石被标记为蓝色；将分析结果与平扫检出结石进行比较,对结石分析的结果进行敏感性和可靠性评估；④由两位影像科医师独立测量常规平扫、双能量扫描、双能量融合120kv图像以及VNC图像兴趣区(ROI)的CT值,尽可能保证ROI大小和位置相同；选择测量的区域为肾皮质区,距离肾脏边缘及肾门保持一定距离,尽量避开明确的病变区每个图像测量4次,取平均值；计算信噪比及进行图像质量评价。
2.术后结石化学分析：其中13例患者取到手术后结石样本,进行化学成分分析法进行结石化学成份检测；
3.统计学处理
1.应用SPSS13.0软件对普通平扫与融合120kv图像、VNC图像ROI所测的平均CT值进行重复测量数据的方差分析,如有差异,再进一步采用多重比较反复LSD法进行两两比较。
2.VNC图像质量评价进行等级资料两样本的Wilcoxon秩和检验。
结果：
1.普通120kv平扫感兴趣区CT值均数为31.03±6.43HU,融合120kv图像CT值为30.09±5.82,VNC融合图像CT值为28.85±2.35HU；其中普通120kv平扫与融合120kv图像CT值比较P=0.057>0.05,即普通120kv平扫与融合120kv图像CT值无显著统计学差异；普通120kv平扫CT值与VNC图像的差异有统计学意义(P=0.000<0.005),且VNC图像CT值低于普通平扫,即VNC(虚拟平扫)图像不能真实反应肾脏CT值；
2.三组图像比较信噪比无显著差异性；VNC图像质量明显低于普通平扫,但是评分均在3分以上,基本可以满足临床影像诊断需要；其中有一病例临床高度怀疑为双肾结石,经虚拟平扫重建和结石分析,排除了结石可能。
3.双能量结石分析中,53例患者中普通平扫检出结石128枚,DECT亦检出128枚,在检出数量上与普通平扫无差异；其中13例患者经双能量CT检查的患者经随访,取到手术后结石样本；所有结石经化学定性分析法检验均为非尿酸结石,其中草酸钙结石7枚,磷酸盐结石5枚,胱氨酸结石1枚；CT双能量分析将2枚磷酸盐结石误诊为草酸钙结石,其余结果与化学分析完全吻合。
结论：
1.双能量结石分析在能够进行尿结石化学成分分析,但其准确性还待进一步提高；
2.双能量融合图像和VNC图像质量要明显低于普通平扫图像；且VNC图像中肾脏的CT值低于普通平扫,VNC技术还无法完全替代普通平扫；
3.双能量分析VNC和尿结石分析技术综合应用,有对鉴别碘造影剂残留、出血、结石有一定的帮助,对结石的诊断有非常有益的潜在应用价值。
总结
1. DECT结石分析能进行尿结石化学成分分析,不仅能够区分尿酸结石和非尿酸结石,其准确率为100%；并能够进一步区分非尿酸结石；
2. VNC所得虚拟平扫图像不能反映真实的双肾在普通平扫时的CT值,且图像质量明显减低,故不能完全替代普通平扫；
3.双能量分析VNC和尿结石分析技术综合应用,有对鉴别碘造影剂残留、出血、结石有一定的帮助,对结石的诊断有非常有益的临床应用价值。
Urolithiasis is a common and increasing problem in daily urological practice. Urinary stones have affected mankind since time immemorial, It would be fascinating to know that the first evidence of urinary stones dates back to 4800 B.C., The majority of stones occur in the kidneys or ureters in human beings. calcium oxalate is the most common mineral occurring in stones in human beings, Treatment for urolithiasis in human beings includes lithotripsy (shattering stones into smaller fragments) or surgery. Shock wave lithotripsy is considered to be the reference treatment for most kinds of calculi. On the other hand, shock wave lithotripsy may not be the technique of choice, nor a cost-effective option when alternative medical treatment options are suitable and potentially harmful shock waves for the renal parenchyma can be avoided. Regarding UA-containing urinary stones,medical dissolution by urinary alkalization demonstrates the reference management technique before other treatment options are considered. These diferent therapy approaches are the driving force behind the efforts to determine the UA-component of urinary stones prior to treatment. Concerning non-UA-containing stones, the differentiation seems to be of a lower value because the knowledge of the major stone component does not allow for the adequate prediction of its fragility in lithotripsy treatment.
Unenhanced computed tomography (CT) of the urinarytract is widely recognized as the most accurate technique for the detection of urinary stones, with a reported sensitivity of 95% to 100%.It is accompanied by the advantage of prompt availability of diagnosis and the identification of alternative diagnoses.Non-enhanced CT of the urinary tract is recognized as the most accurate technique for the detection of urinary stones..the Dual Source CT scanner is composed of two x-ray tubes and two detector units arranged on the rotating gantry with an angular off set of 90°.When running both tubes at the same voltage, a high temporal resolution is achieved that is used primarily for the evaluation of coronary arteries.When operating the x-ray tubes at different tube voltages, two different x-ray spectra are simultaneously obtained that improve the characterization and differentiation of various tissues. Advantages of CT are the high sensitivity and specificity of the diagnosis and the simultaneous recognition of other associated pathologies.
The purpose of this study was to assess the potential of virtual unenhanced DSCT scans from dual-energy data for the detection of urinary stone disease. Although MDCT can identify patients who suffer from urinary stone disease, it cannot reproducibly predict stone composition. Dual Energy CT has the potential to differentiate urinary stone compositions. This could be of high clinical relevance for proper medical management, keeping in mind that urinary alkalinisation is the therapy of choice in patients with uric acid stones, and shock waves can be avoided that potentially may harm the renal parenchyma.
We assessed the potential of dual-energy computed tomography (CT) for the differentiation between uric acid (UA)-containing and non-UA-containing urinary stones. Further prospective studies are warranted in order to prove the feasibility of the chemical decomposition in an in-vivo setting and to assess the clinical value of the new technology.
Part I Dual-energy CT for the differential diagnosis of urinary calculi in vitro
Objectives:We assessed the potential of dual-energy computed tomography (CT) for the diferentiation between uric acid (UA)-containing and non-UA-containing urinary stones;It is also expected to further distinguish between different types of non-uric acid stones. the reliability of Chemical composition analysis by Dual-energy CT analysis and its accuracy were evaluated.
Materials and methods:
1.89 stones collected during surgical and percutaneous nephrolithotomy lithotomy were included in this study. A Chemical Compositive analysis of the stones was performed after CT examination. All stones are a mixture of different crystal, a certain chemical components accounting for more than 50% is defined as a pure urinary stone.81 stones have been identified as pure stonea by chemical rough qualitative analysis,47 calcium oxalate, phosphate stones in 23 (including hydroxy-apatite, calcium hydrogen phosphate, and magnesium ammonium phosphate stone), cystine stones 7 and uric acid 4,8 mixed urinary calculi.
2. All stones were examined in an ex vivo work bench model placed on the dual-source CT scanner table. Stones were embedded in random order in Swine kidney was purchased from the market early morning. After scanning, the stones were sent to the laboratory for chemical analysis.
3. The examinations of the model were performed on a dual-source CT scanner (Deffnition, Siemens Medical Solutions, Germany) in the dual-energy mode. After positioning of conventional scanned, Conventional non-enhanced CT scan was executed, Scanning parameters:120kv/130mAs, slice collimation 0.6 mm and pitch 0.60. next, enter the dual-energy CT scan mode, The tube voltages were set at 80 and 140 kV, and the tube current time products at 404 and 95 mAs/rotation. Slice thickness and pitch the same as with conventional CT scanning that has been completed;Scan data will be transmitted to the workstation.
4. The images from the 140/80kv scan were reconstructed on the regular image reconstruction system of the CT scanner.Additional reconstructions from the raw spiral projection data of both tubes were performed on an external prototype workstation (Multi Modality Workplace, Syngo multimodality AG2008 Software, Siemens). The dual-energy data reconstruction was per-formed with a speciffcally designed soft tissue convolution kernel (D30f) in order to avoid changes of voxel informa-tion at objects'edges. CT value of each urinary calculi at different scanning conditions were measured.
5. urinary calculi were analysised byDual-energy CT-processing software(Siemens Medical Solutions, Forchheim, Germany). This software automati-cally calculates differences of attenuation between the 80 and 140 kV data sets and displays the results in a colour-coded fashion on fused multi-planar reformations. But also, the software displays calcified structures like cortical bone and calcified stones in blue, and UA stones in red color. Stone differentiation based on color coding only was then compared with differentiation byDEI.
6. Statistical analysis:The data obtained earlier were analysised by using of SPSS statistical software, The results were expressed as absolute numbers, frequen-cies, and means±SDs. The non-parametric Wilcoxon Signed Rank Test was performed to evaluate signiffcant differences between the 80 and 140-kV series attenuation measurements, between scans, and between readers. Differences in attenuation at 80 and 140 kV were assessed using the t test between different types of urinary stones. A P level of<0.05 was con-sidered statistically signiffcant. The sensitivity, speciffcity, positive predictive value, and negative predictive value were calculated from Chi-Square tests of contingency. all statistical analysis was conducted using SPSS software.
Results:
1. All 89 stones were clearly visible at 80,120, and 140kVp and on the dual energy images scanned at 80 and 140 kVp.The CT values of urinary stones gradually decreased as the tube voltage increased except for Uric acid stones. uric acid stones and non-uric acid stones can be distinguished by Non-enhanced CT scanning. the difference of CT values in calcium oxalate and calcium phosphate is no significant statistical difference. there is no overlap between the dual energy indices of UA and other types of calculi, and there is very little overlap between mixed UA and calcified stones.
2. the major advantage of DECT scanning for evaluation of urinary calculi is that the UA,cystine, struvite, and calcifications, which are the most clinically important components of renal calculi, can be differentiated by DEI, The information from the dual energy scan, namely the DEI, is needed to reliably differentiate between different stone materials.
Conclusion:With dual energy CT techniques,the UA,cystine,struvite, and mixed renal calculi can be differentiated from other types of stones ex vitro. Our study has confirmed that a differentiation of renal calculi is feasible in vitro and in vivo and can be combined in DECT with stone detection in a single fast acquisition. DECT is an accurate, noninvasive test in patients with suspected or known urinary calculi. As opposed to intravenous urography,it does not require an intravenous contrast agent injection. Previous studies had shown the feasibility of a differentiation of calculi in vitro and to some extent in vivo. The information from the dual energy scan, namely the DEI, is needed to reliably differentiate between different stone materials. According to our results, the major advantage of DECT scanning for evaluation of urinary calculi is that the UA,cystine, struvite, and calcifications, which are the most clinically important components of renal calculi, can be differentiated by DEI. the DEI is useful to reflect the spectral behavior of a substance in a single unit.
In conclusion, DECT can provide a fast and noninvasive detection and differentiation of renal calculi. The DEI characterizes the dual energy behavior of substances and makes an immediate stone differentiation feasible.Stone differentiation is of importance for treatment planning and may render invasive stone removal dispensable in some patients.
PartⅡClinical Imaging of Dual-energy CT for the urolithiasis
Objectives:Ex-vivo studies have demonstrated that Dual Source, Dual Energy CT has the potential to differentiate urinary stone compositions. the purpose of this study is to explore the clinical value of the dual-energy CT in the differential diagnosis of urinary calculi.
Materials and methods:
1.53 patients suspected of urinary tract stone disease were included in this study, Patients receiving enhanced scan must have the following conditions:non-iodine contrast agent allergy history, no serious heart, lung, renal insufficiency; non-maternity; In addition, all patients had signed informed consent agreement.
2. the patients included in the study were referred to perform abdom inal CT scan. Conventional (VNCT), portal phase enhanced scanning were performed with dual-energy mode (80kV/400mA and 140kV/96mA). The dedicated software of L iver VNC was used to reformat virtual nonen-hanced CT at the arterial and portal phase.Image quality, the average CT value, image quality, signal to noise ratio, and lesion detectability were compared by the SPPS statistical software. the data obtained from dual-energy stone analysis and chemical analysis were compared.
Results:
1. the Stone detection was no statistical difference between the general non-enhanced scanning and Dual-energy scanning, all urinary stones were detected.
2. The average CT value of the kidney measured was no statistical difference between the general non-enhanced scanning and Dual-energy CT fusion images; Statistically significant difference among conventional nonenhanced CT and virtual nonenhanced CT at the portal phase (P<0.05).CT value of VNC was significantly lower than that of general CT scan.SNR of VNCT was much higher than that of conventional nonenhanced CT (P=0.00). Image quality of the VNCT was decreased compared with conventional nonenhanced CT (P=0. 00<0.05), but it had at least moderate image quality to meet imaging diagnosis.
3. Dual-energy stone analysis:128 urinary stones were found from the inspection of the 53 patients; 13 stone samples were taken to surgery, all the stones through a chemical analysis, Statistical analysis was not carried out due to a small number of samples.of which calcium oxalate stones in 7, phosphate stones 5, cystine stones 1; In which two phosphate stones were mistaken for calcium oxalate stone by CT dual-energy analysis, the rest of the results coincide completely with the chemical analysis.
Conclusion
1. the stone detection rate of dual-energy CT scan is basically the same as the conventional CT scan, Dual-energy CT analysis is a reliable means of imaging for urolithiasis.
2. CT value of VNC was significantly lower than that of general CT scan, in addition, Its image quality decreased significantly Just to meet the needs of clinical diagnosis; therefore, VNC can not entirely replace the non-enhanced scanning to minimize radiation exposure, VNC can help radiologists identify urinary stones from iodine contrast agent residue.
3. Dual-energy chemical composition of urinary stones was a reliability technologies, but its accuracy needs to be improved..
Summary
DECT is an accurate, noninvasive test in patients with suspected or known urinary calculi, our results show that identification of UA components in uroliths is feasible. We did not experience any mischaracterization of stones containing UA, Therefore, we have ample reason to believe that the reliability of dual-energy analysis techniques is 100% to different uric acid stones from non-uric acid stones. As opposed to intravenous urography,it does not require an intravenous contrast agent injection. With dual energy CT techniques, the UA, cystine,struvite, and mixed renal calculi can be differentiated from other types of stones in vitro and in vivo. This is of clinical relevance as UA uroliths may be treated pharmacologically rather than with surgical extraction or extracorporal shockwave lithotripsy. VNC is the useful technology to help radiologists identify urinary stones from iodine contrast agent. VNC can not entirely replace the non-enhanced scanning to minimize radiation exposure owing to its poor image quality and unreliable CT value.There are some limitations to our study that have to be acknowledged. One is the small sample sizes of stones in the in vitro experiments and the limited number of patients. Further studies with external validation encompassing more patients will be required to eventually establish stone differentiation in DECT as a valid method.
影像学检查是诊断泌尿系疾病的主要方法,DECT技术除了能准确检测结石外,除区别尿酸结石和非尿酸结石外,并可对其成分进一步分析。本文通过DECT对尿结石化学成分分析的实验和临床应用研究,以期评估DECT对尿石症的化学成分分析和临床鉴别诊断上的可靠性。
第一部分DECT尿结石体外成分分析的实验研究
研究目的评价DECT技术结石化学成分分析的可靠性及其准确性。
材料与方法
1.结石标本的采集：收集南方医院泌尿外科手术后结石89枚,所有结石均为经临床确诊为泌尿系结石的患者行微创经皮肾镜取石(mini-Percutaneousnephro--lithotomy)术后获得；
2.结石标本的包埋与处理：将收集到的结石标本编号,记录颜色、质地,然后将结石标本用蒸馏水洗净,放入烤箱内烘干；清晨在市场购买新鲜猪肾,将猪肾纵面剖开,把标本放入猪肾内,将埋有结石的猪肾置于水中,尽可能排出其中的空气；用保鲜袋捞起后,排出保鲜袋内的水。适当包裹后,供CT扫描使用。
3.CT扫描：使用保鲜袋将带有结石标本的猪肾包裹好,在放在扫描台上,将扫描中心线调整至样本的中心点；常规双肾120KV扫描完成后,进行140/80KV双能量扫描。
3.1设备西门子双源CT扫描机(dual-sourcecomputertomography, DSCT),型号为SOMATOM Definition-mmwpsp02,后处理工作站软件版本为Syngo multimodality AG2008。
3.2扫描条件采用0.6mm层厚无间距扫描；所得的数据经拆薄重建后传至随机工作站进行重建及双能量分析；扫描参数如下表。
3.3图像后处理两位放射科医生通过在随机默认的标准肾脏软组织窗宽、窗位分析结石影像；分别在结石最大横截面积测CT平均值,同一枚结石每位医生测量4次,取所测平均值；进入工作站的双能量分析(Dual Energy)界面选项,导入双能量140/80KV扫描数据,进行双能量结石分析；
4.结石化学成分分析：通过化学的方法对结石标本进行定性分析；将结石分为草酸钙结石、磷酸盐结石、胱氨酸结石、尿酸结石及混合结石(结石均为混合物,且90%以上的结石含有钙盐成分,某成分含量超过50%的结石被定义为某种性质的结石)。
4.1实验器材与试剂泌尿结石成份分析试剂盒及(购自中科院广州化学研究所广州百康生物科技有限公司),另配结石专用陶瓷研磨器(研钵+研磨棒)及试管、金属匙若干。其中试剂盒中化学试剂包括：尿酸试剂Ⅰ、尿酸试剂Ⅱ、铵试剂、磷酸试剂、盐酸试剂(2支)、草酸试剂(2支)、钙镁试剂、镁试剂、胱氨酸试剂Ⅰ,胱氨酸试剂Ⅱ,胱氨酸试剂Ⅲ。
4.2分析方法通过化学的方法对结石标本进行定性分析,可以知道结石含有钙、镁、铵、磷酸盐、尿酸或尿酸盐、草酸盐、胱氨酸等,该种方法虽比较粗糙,但又比较简单易行,基本可以满足临床和科研需要,是目前国内医疗、科研机构通用的结石化学成份鉴定方法。具体操作步骤如下：
1)标本准备：取少量结石(大米粒大小即可),用蒸馏水冲洗干净,放在相应编号的研钵中,自然晾干(一般放置1-2小时)。干燥后,用研磨棒把研钵内结石研成粉末备用；每份结石标本只能用一套研磨器(研钵+研磨棒)
2)分析步骤：用金属小匙取上述结石粉末各1匙,分别置于白板中的3个孔中,及3支试管内,然后依次进行下列步骤。
①尿酸：在有孔白板的第1孔,分别滴入尿酸试剂Ⅰ和尿酸试剂Ⅱ各2滴,呈蓝色为阳性。
②钱盐：在有孔白板的第2孔,滴加钱试剂3滴,如显黄色或者红棕色沉淀为阳性；由于试剂中会含有少量铵离子,会出现假阳性反应,所以实验时应进行空白对照；即在一个空白孔内同样滴加3滴铵试剂,与待测孔进行颜色对照。
③胱氨酸：在有孔白板的第3孔,分别滴入胱氨酸试剂I2滴、胱氨酸试剂Ⅱ1滴、胱氨酸试剂Ⅲ2滴；5分钟后观察,蓝色为阳性。注意：试剂加完后,不宜放置过久,否则会出现假阳性,故一定要在5分钟后观察结果。
④磷酸盐：取第1支试管,滴加磷酸试剂3-4滴,摇匀后静置3分钟,观察结果,溶液呈黄色,或管壁有黄色沉淀为阳性。注意：如果温度低,或显色不明显,可在酒精灯上稍微加热,如加热时有气泡产生,应放置片刻,待气泡消失后再观察结果。
⑤碳酸盐：取第2支试管,将结石粉末放置于小试管内,沿试管壁加入盐酸试剂(3 mol/L盐酸约0.5ml)2滴,振动后放置仔细观察有无气泡产生,有气泡为阳性。
⑥草酸盐：在步骤5)试管中,继续滴加草酸试剂5滴,摇匀。如果出现白色混浊,则为阳性。加试剂Ⅰ约2 ml,加试剂Ⅱ、Ⅲ各2滴渐生蓝色为阳性。
⑦钙盐：取第3支试管,将结石粉末放置于小试管内,滴入盐酸试剂Ⅰ1滴和钙镁试剂3滴,如有白色混浊,则为阳性。⑧镁盐：将步骤7)试管中,继续滴加镁试剂2滴,摇匀,如出现蓝色沉淀,则为阳性。
4.3结果判断
5.统计学分析：
1.所有数据分析采用SPSS 13.0统计软件完成。
2.不同结石的CT值差异进行重复测量数据的方差分析,如有差异,再进一步采用多重比较反复LSD法进行两两比较
3.将分析结果与化学分析法进行两相关样本的非参数检验；计算每种结石利用CT双能量技术进行鉴别诊断的敏感性和特异性。
结果
1.结石种类分布及构成比经化学分析,89枚结石中,其中草酸钙结石53枚(59.55%)、磷酸盐结石17枚(19.10%)、胱氨酸结石7枚(7.86%),尿酸结石4枚(4.49%)；另8枚结石不能通过化学分析法鉴别其种类；
2.结石CT扫描结果平扫及DECT扫描,包括尿酸结石在内的所有尿路结石均被检出；全都清晰显像,其中1例尿酸结石(X线阴性结石)由于体积较小,显示稍差,通过调节窗宽、窗位亦可以获得较好显示；草酸钙结石>磷酸盐结石>胱氨酸结石>尿酸结石,其中草酸钙结石与磷酸盐结石有较多重叠,CT值差异无统计学差异性；除尿酸结石外,非尿酸结石CT值均随着管电压的增高而减低。
3.双能量结石分析所有结石均被在双能量分析软件中被标记,其检出率为100%；其中尿酸结石分析值为负数,被标记为红色；非尿酸结石分析值为正数,被标记为蓝色,与结石化学分析结果完全吻合,尿酸结石的诊断敏感性和特异性均为100%；三种非尿酸结石双能量分析值比较均具有显著统计学差异性。双能量分析结合的CT值对3种非尿酸结石化学成分双能量与化学分析法用两相关样本的非参数检验；其中尿酸结石因在双能量结石分析中被标记为红色,且CT值明显低于其他类型结石,此处仅分析3种非尿酸结石；经化学分析法,鉴定为草酸钙结石有47例,磷酸盐结石有23例；胱氨酸结石有7例；但经双能量分析,认为草酸钙结石有50例,磷酸盐结石有19例,胱氨酸结石有8例。两种方法经比较无显著统计学差异(P=0.703>0.05)；且具有高度关联性。DECT分析法鉴别草酸钙结石的敏感性(sensitivity)为89.36%；特异性(specificity)为83.33%；诊断磷酸盐结石的敏感性为60.87%,特异性为90.74%；诊断胱氨酸结石的敏感性为71.43%,特异性为95.71%。
结论：
1.DECT尿结石分析技术能够进行尿结石的化学成分分析；其中尿酸结石被标记为红色,非尿酸结石标记为蓝色,鉴别尿酸与非尿酸结石的准确率为100%；140/80Kv双能量扫描时,使用CT差值和DEI作为指标,无论是尿酸结石、胱氨酸结石、草酸钙结石、磷酸盐结石,其差异均有显著统计学意义,可以作为鉴别结石化学成分的有效指标,并能够进一步鉴别非尿酸结石。
2.DECT分析法鉴别草酸钙结石的敏感性(sensitivity)为89.36%；特异性(specificity)为83.33%；诊断磷酸盐结石的敏感性为60.87%,特异性为90.74%；诊断胱氨酸结石的敏感性为71.43%,特异性为95.71%；是一种无创的结石成分分析方法。
第二部分DECT在泌尿结石疾病鉴别中的临床应用
研究目的：探讨双肾DECT扫描在诊断结石病方面的诊断价值,从图像质量、信噪比、病变检出及鉴别上的差异,评价其在临床应用的可靠性。
材料与方法：
1.1临床资料：收集我院临床拟诊为的泌尿系结石症患者53例,其中男37例,女16例,年龄18-54岁,平均(34±12)岁；进行增强扫描的患者要求无碘对比剂过敏史、无严重心、肺、肾功能不全、非孕产妇,且所有患者均签署知情同意书；
1.2检查方法：采用Siemens Somatom Definition DSCT进行检查,常规120kv平扫后,进行非增强双能量扫描,参数为：A球管电压140kV,有效电流96mA s,B球管电压80 kV,有效电流404 mAs；平扫结束后采用双筒高压注射器经右侧肘前静脉以3-4.5ml/s流率注射浓度为300 mg/ml的优维显80ml,注射完毕后再以相同流率注射40ml生理盐水,延时25s行动脉期扫描,120s行双能量延迟扫描；所有扫描经自动拆薄重建为层厚0.75 mm的图像传至后处理工作站；
1.3工作站后处理：①取DE composition=0.3,按照140 kV数据70%,与80 kV数据30%的比率,通过特殊计算后融合成120 kV的图像；②将双能延迟扫描数据调入Dual- Energy软件内,启用应用程序内的Liver VNC处理,通过调整CT与碘造影剂的融合比率,将CT的融合比率调节到100%,碘对比剂的融合比率调整到0%,得到VNC数据,再进行MPR等重建；③将非增强双能量扫描数据拆薄重建数据(80kV与140 kV)分别调入工作站Dual Energy软件内,启动应用程序内的Kidneystone处理,进行尿结石双能量分析,其中尿酸结石被标记为红色,非尿酸结石被标记为蓝色；将分析结果与平扫检出结石进行比较,对结石分析的结果进行敏感性和可靠性评估；④由两位影像科医师独立测量常规平扫、双能量扫描、双能量融合120kv图像以及VNC图像兴趣区(ROI)的CT值,尽可能保证ROI大小和位置相同；选择测量的区域为肾皮质区,距离肾脏边缘及肾门保持一定距离,尽量避开明确的病变区每个图像测量4次,取平均值；计算信噪比及进行图像质量评价。
2.术后结石化学分析：其中13例患者取到手术后结石样本,进行化学成分分析法进行结石化学成份检测；
3.统计学处理
1.应用SPSS13.0软件对普通平扫与融合120kv图像、VNC图像ROI所测的平均CT值进行重复测量数据的方差分析,如有差异,再进一步采用多重比较反复LSD法进行两两比较。
2.VNC图像质量评价进行等级资料两样本的Wilcoxon秩和检验。
结果：
1.普通120kv平扫感兴趣区CT值均数为31.03±6.43HU,融合120kv图像CT值为30.09±5.82,VNC融合图像CT值为28.85±2.35HU；其中普通120kv平扫与融合120kv图像CT值比较P=0.057>0.05,即普通120kv平扫与融合120kv图像CT值无显著统计学差异；普通120kv平扫CT值与VNC图像的差异有统计学意义(P=0.000<0.005),且VNC图像CT值低于普通平扫,即VNC(虚拟平扫)图像不能真实反应肾脏CT值；
2.三组图像比较信噪比无显著差异性；VNC图像质量明显低于普通平扫,但是评分均在3分以上,基本可以满足临床影像诊断需要；其中有一病例临床高度怀疑为双肾结石,经虚拟平扫重建和结石分析,排除了结石可能。
3.双能量结石分析中,53例患者中普通平扫检出结石128枚,DECT亦检出128枚,在检出数量上与普通平扫无差异；其中13例患者经双能量CT检查的患者经随访,取到手术后结石样本；所有结石经化学定性分析法检验均为非尿酸结石,其中草酸钙结石7枚,磷酸盐结石5枚,胱氨酸结石1枚；CT双能量分析将2枚磷酸盐结石误诊为草酸钙结石,其余结果与化学分析完全吻合。
结论：
1.双能量结石分析在能够进行尿结石化学成分分析,但其准确性还待进一步提高；
2.双能量融合图像和VNC图像质量要明显低于普通平扫图像；且VNC图像中肾脏的CT值低于普通平扫,VNC技术还无法完全替代普通平扫；
3.双能量分析VNC和尿结石分析技术综合应用,有对鉴别碘造影剂残留、出血、结石有一定的帮助,对结石的诊断有非常有益的潜在应用价值。
总结
1. DECT结石分析能进行尿结石化学成分分析,不仅能够区分尿酸结石和非尿酸结石,其准确率为100%；并能够进一步区分非尿酸结石；
2. VNC所得虚拟平扫图像不能反映真实的双肾在普通平扫时的CT值,且图像质量明显减低,故不能完全替代普通平扫；
3.双能量分析VNC和尿结石分析技术综合应用,有对鉴别碘造影剂残留、出血、结石有一定的帮助,对结石的诊断有非常有益的临床应用价值。
Urolithiasis is a common and increasing problem in daily urological practice. Urinary stones have affected mankind since time immemorial, It would be fascinating to know that the first evidence of urinary stones dates back to 4800 B.C., The majority of stones occur in the kidneys or ureters in human beings. calcium oxalate is the most common mineral occurring in stones in human beings, Treatment for urolithiasis in human beings includes lithotripsy (shattering stones into smaller fragments) or surgery. Shock wave lithotripsy is considered to be the reference treatment for most kinds of calculi. On the other hand, shock wave lithotripsy may not be the technique of choice, nor a cost-effective option when alternative medical treatment options are suitable and potentially harmful shock waves for the renal parenchyma can be avoided. Regarding UA-containing urinary stones,medical dissolution by urinary alkalization demonstrates the reference management technique before other treatment options are considered. These diferent therapy approaches are the driving force behind the efforts to determine the UA-component of urinary stones prior to treatment. Concerning non-UA-containing stones, the differentiation seems to be of a lower value because the knowledge of the major stone component does not allow for the adequate prediction of its fragility in lithotripsy treatment.
Unenhanced computed tomography (CT) of the urinarytract is widely recognized as the most accurate technique for the detection of urinary stones, with a reported sensitivity of 95% to 100%.It is accompanied by the advantage of prompt availability of diagnosis and the identification of alternative diagnoses.Non-enhanced CT of the urinary tract is recognized as the most accurate technique for the detection of urinary stones..the Dual Source CT scanner is composed of two x-ray tubes and two detector units arranged on the rotating gantry with an angular off set of 90°.When running both tubes at the same voltage, a high temporal resolution is achieved that is used primarily for the evaluation of coronary arteries.When operating the x-ray tubes at different tube voltages, two different x-ray spectra are simultaneously obtained that improve the characterization and differentiation of various tissues. Advantages of CT are the high sensitivity and specificity of the diagnosis and the simultaneous recognition of other associated pathologies.
The purpose of this study was to assess the potential of virtual unenhanced DSCT scans from dual-energy data for the detection of urinary stone disease. Although MDCT can identify patients who suffer from urinary stone disease, it cannot reproducibly predict stone composition. Dual Energy CT has the potential to differentiate urinary stone compositions. This could be of high clinical relevance for proper medical management, keeping in mind that urinary alkalinisation is the therapy of choice in patients with uric acid stones, and shock waves can be avoided that potentially may harm the renal parenchyma.
We assessed the potential of dual-energy computed tomography (CT) for the differentiation between uric acid (UA)-containing and non-UA-containing urinary stones. Further prospective studies are warranted in order to prove the feasibility of the chemical decomposition in an in-vivo setting and to assess the clinical value of the new technology.
Part I Dual-energy CT for the differential diagnosis of urinary calculi in vitro
Objectives:We assessed the potential of dual-energy computed tomography (CT) for the diferentiation between uric acid (UA)-containing and non-UA-containing urinary stones;It is also expected to further distinguish between different types of non-uric acid stones. the reliability of Chemical composition analysis by Dual-energy CT analysis and its accuracy were evaluated.
Materials and methods:
1.89 stones collected during surgical and percutaneous nephrolithotomy lithotomy were included in this study. A Chemical Compositive analysis of the stones was performed after CT examination. All stones are a mixture of different crystal, a certain chemical components accounting for more than 50% is defined as a pure urinary stone.81 stones have been identified as pure stonea by chemical rough qualitative analysis,47 calcium oxalate, phosphate stones in 23 (including hydroxy-apatite, calcium hydrogen phosphate, and magnesium ammonium phosphate stone), cystine stones 7 and uric acid 4,8 mixed urinary calculi.
2. All stones were examined in an ex vivo work bench model placed on the dual-source CT scanner table. Stones were embedded in random order in Swine kidney was purchased from the market early morning. After scanning, the stones were sent to the laboratory for chemical analysis.
3. The examinations of the model were performed on a dual-source CT scanner (Deffnition, Siemens Medical Solutions, Germany) in the dual-energy mode. After positioning of conventional scanned, Conventional non-enhanced CT scan was executed, Scanning parameters:120kv/130mAs, slice collimation 0.6 mm and pitch 0.60. next, enter the dual-energy CT scan mode, The tube voltages were set at 80 and 140 kV, and the tube current time products at 404 and 95 mAs/rotation. Slice thickness and pitch the same as with conventional CT scanning that has been completed;Scan data will be transmitted to the workstation.
4. The images from the 140/80kv scan were reconstructed on the regular image reconstruction system of the CT scanner.Additional reconstructions from the raw spiral projection data of both tubes were performed on an external prototype workstation (Multi Modality Workplace, Syngo multimodality AG2008 Software, Siemens). The dual-energy data reconstruction was per-formed with a speciffcally designed soft tissue convolution kernel (D30f) in order to avoid changes of voxel informa-tion at objects'edges. CT value of each urinary calculi at different scanning conditions were measured.
5. urinary calculi were analysised byDual-energy CT-processing software(Siemens Medical Solutions, Forchheim, Germany). This software automati-cally calculates differences of attenuation between the 80 and 140 kV data sets and displays the results in a colour-coded fashion on fused multi-planar reformations. But also, the software displays calcified structures like cortical bone and calcified stones in blue, and UA stones in red color. Stone differentiation based on color coding only was then compared with differentiation byDEI.
6. Statistical analysis:The data obtained earlier were analysised by using of SPSS statistical software, The results were expressed as absolute numbers, frequen-cies, and means±SDs. The non-parametric Wilcoxon Signed Rank Test was performed to evaluate signiffcant differences between the 80 and 140-kV series attenuation measurements, between scans, and between readers. Differences in attenuation at 80 and 140 kV were assessed using the t test between different types of urinary stones. A P level of<0.05 was con-sidered statistically signiffcant. The sensitivity, speciffcity, positive predictive value, and negative predictive value were calculated from Chi-Square tests of contingency. all statistical analysis was conducted using SPSS software.
Results:
1. All 89 stones were clearly visible at 80,120, and 140kVp and on the dual energy images scanned at 80 and 140 kVp.The CT values of urinary stones gradually decreased as the tube voltage increased except for Uric acid stones. uric acid stones and non-uric acid stones can be distinguished by Non-enhanced CT scanning. the difference of CT values in calcium oxalate and calcium phosphate is no significant statistical difference. there is no overlap between the dual energy indices of UA and other types of calculi, and there is very little overlap between mixed UA and calcified stones.
2. the major advantage of DECT scanning for evaluation of urinary calculi is that the UA,cystine, struvite, and calcifications, which are the most clinically important components of renal calculi, can be differentiated by DEI, The information from the dual energy scan, namely the DEI, is needed to reliably differentiate between different stone materials.
Conclusion:With dual energy CT techniques,the UA,cystine,struvite, and mixed renal calculi can be differentiated from other types of stones ex vitro. Our study has confirmed that a differentiation of renal calculi is feasible in vitro and in vivo and can be combined in DECT with stone detection in a single fast acquisition. DECT is an accurate, noninvasive test in patients with suspected or known urinary calculi. As opposed to intravenous urography,it does not require an intravenous contrast agent injection. Previous studies had shown the feasibility of a differentiation of calculi in vitro and to some extent in vivo. The information from the dual energy scan, namely the DEI, is needed to reliably differentiate between different stone materials. According to our results, the major advantage of DECT scanning for evaluation of urinary calculi is that the UA,cystine, struvite, and calcifications, which are the most clinically important components of renal calculi, can be differentiated by DEI. the DEI is useful to reflect the spectral behavior of a substance in a single unit.
In conclusion, DECT can provide a fast and noninvasive detection and differentiation of renal calculi. The DEI characterizes the dual energy behavior of substances and makes an immediate stone differentiation feasible.Stone differentiation is of importance for treatment planning and may render invasive stone removal dispensable in some patients.
PartⅡClinical Imaging of Dual-energy CT for the urolithiasis
Objectives:Ex-vivo studies have demonstrated that Dual Source, Dual Energy CT has the potential to differentiate urinary stone compositions. the purpose of this study is to explore the clinical value of the dual-energy CT in the differential diagnosis of urinary calculi.
Materials and methods:
1.53 patients suspected of urinary tract stone disease were included in this study, Patients receiving enhanced scan must have the following conditions:non-iodine contrast agent allergy history, no serious heart, lung, renal insufficiency; non-maternity; In addition, all patients had signed informed consent agreement.
2. the patients included in the study were referred to perform abdom inal CT scan. Conventional (VNCT), portal phase enhanced scanning were performed with dual-energy mode (80kV/400mA and 140kV/96mA). The dedicated software of L iver VNC was used to reformat virtual nonen-hanced CT at the arterial and portal phase.Image quality, the average CT value, image quality, signal to noise ratio, and lesion detectability were compared by the SPPS statistical software. the data obtained from dual-energy stone analysis and chemical analysis were compared.
Results:
1. the Stone detection was no statistical difference between the general non-enhanced scanning and Dual-energy scanning, all urinary stones were detected.
2. The average CT value of the kidney measured was no statistical difference between the general non-enhanced scanning and Dual-energy CT fusion images; Statistically significant difference among conventional nonenhanced CT and virtual nonenhanced CT at the portal phase (P<0.05).CT value of VNC was significantly lower than that of general CT scan.SNR of VNCT was much higher than that of conventional nonenhanced CT (P=0.00). Image quality of the VNCT was decreased compared with conventional nonenhanced CT (P=0. 00<0.05), but it had at least moderate image quality to meet imaging diagnosis.
3. Dual-energy stone analysis:128 urinary stones were found from the inspection of the 53 patients; 13 stone samples were taken to surgery, all the stones through a chemical analysis, Statistical analysis was not carried out due to a small number of samples.of which calcium oxalate stones in 7, phosphate stones 5, cystine stones 1; In which two phosphate stones were mistaken for calcium oxalate stone by CT dual-energy analysis, the rest of the results coincide completely with the chemical analysis.
Conclusion
1. the stone detection rate of dual-energy CT scan is basically the same as the conventional CT scan, Dual-energy CT analysis is a reliable means of imaging for urolithiasis.
2. CT value of VNC was significantly lower than that of general CT scan, in addition, Its image quality decreased significantly Just to meet the needs of clinical diagnosis; therefore, VNC can not entirely replace the non-enhanced scanning to minimize radiation exposure, VNC can help radiologists identify urinary stones from iodine contrast agent residue.
3. Dual-energy chemical composition of urinary stones was a reliability technologies, but its accuracy needs to be improved..
Summary
DECT is an accurate, noninvasive test in patients with suspected or known urinary calculi, our results show that identification of UA components in uroliths is feasible. We did not experience any mischaracterization of stones containing UA, Therefore, we have ample reason to believe that the reliability of dual-energy analysis techniques is 100% to different uric acid stones from non-uric acid stones. As opposed to intravenous urography,it does not require an intravenous contrast agent injection. With dual energy CT techniques, the UA, cystine,struvite, and mixed renal calculi can be differentiated from other types of stones in vitro and in vivo. This is of clinical relevance as UA uroliths may be treated pharmacologically rather than with surgical extraction or extracorporal shockwave lithotripsy. VNC is the useful technology to help radiologists identify urinary stones from iodine contrast agent. VNC can not entirely replace the non-enhanced scanning to minimize radiation exposure owing to its poor image quality and unreliable CT value.There are some limitations to our study that have to be acknowledged. One is the small sample sizes of stones in the in vitro experiments and the limited number of patients. Further studies with external validation encompassing more patients will be required to eventually establish stone differentiation in DECT as a valid method.
引文
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1.140/80Kv双能量扫描时,使用CT差值和DEI作为指标,无论是尿酸结石、胱氨酸结石、草酸钙结石、磷酸盐结石,其差异均有显著统计学意义,可以作为鉴别结石化学成分的有效指标；
2. 双源CT双能量尿结石分析技术将尿酸结石标记为红色,非尿酸结石标记为蓝色；双能量CT扫描不仅能区分尿酸和非尿酸结石,而且能对草酸钙结石、磷酸盐结石、胱氨酸结石做进一步鉴别,提供了一种无创的结石化学成分分析方法。
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[5]NgCS, Streem SB.Contemporary management of cystinuria.J Endourol,1999, 13 (9):647-651
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[7]Gonzalez Enguita C, Calahorra Fernandez FJ, Cabrera Perez J, et al. Surgery of renoureteral lithiasis. Current indications [J]. Actas Urol Esp,2001,25:610-617.
[8]Zhu S, Cocks FH, Preminger GM, et al. The role of stress waves and cavitation in stone comminution in shock wave lithotripsy. Ultrasound Med Biol.2002 May;28(5):661-71.
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[12]Carmona P, Bellanato J,Escolar E. Biospect roscopy,1997,3:331.
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[14]NewhouseJH, Prien EL,Amis ES, Dretler SP, Pfister RC. Computed tomographic analysis of urinary calculi. AJR Am J Roentgenol.1984,142(3): 545-554
[15]Tublin ME, Murphy ME, Delong DM, et al. Conspicuity of renal calculi at unenhanced CT:effects of calculus composition and size and CT technique. Radiology,2002,225(1):91-96
[16]洪平,胡道予,万常华等,多层螺旋CT对显示泌尿系微小结石的实验研究,放射学实践,2004,19(9)：641-643
[17]Mitcheson HD, Zamenhof RQBankoff MS, et al. Determination of the chemical composition of urinary calculi by computerized tomography [J].J Urol,1983,130 (4):8142819.
[18]Mostafavi MR,Ernst RD,Saltzman B. Accurate determination of chemical composition of urinary calculi by spiral computerized tomography[J]. J Urol,1998,159(3):673-675.
[19]Hillman BJ, Drach GW, Tracey P, Gaines JA. Computed, tomographic analysis of renal calculi. AJR Am J Roentgenol 1984;142:549-52.
[20]Saw K, Mcateer J, FinebergN,et al.Calcium stone fragility is predicted by helical CT attenuation values [J].J Endourol,2000,14(6):471-474
[21]陈志强,周哲,叶章群等,螺旋CT判定尿结石成分的体外研究,临床泌尿外科杂志,2005,20(10)：614-616
[22]BellinMF, Renard-Penna R, Conort P, et al. Helical CT evaluation of the chemical composition of urinary tract calculi with a discriminant analysis of CT-attenuation values and density. Eur Radiol 2004; 14:2134-2140
[23]Deveci S, Coskun M, Tekin MI, et al.Spiral computed tomography:role in determination of chemical composition of pure and mixed urianry stones -an in vitro study [J]. J Urol,2004,64(2):237-340
[24]Mostafavi MR, Ernst RD, Saltzman B, et al. Accurated determination of chemical composition of urinary calculi by spiral computerized tomography [J]. J Urol,1998,159(3):673-675.
[25]Scheffel H,Stolzmann P,Frauenfelder T,et al. Dual-energy contrast-enhanced computed tomography for the.detection of urinary stone disease.Invest Radial, 2007,42:823-829.
[26]Stolzmann P, Schevel H, Rentsch K, et al. Dual energy computed tomography for the diferentiation of uric acid stones:exvivo perform ance evaluation. U rol Res,2008,36:133
[27]Graser A, Johnson TR, Chandarana H, et al. Dual energy CT:p reliminary observations and potential clinical app lications in the abdomen. Eur Radiol,2009,19:13
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[24]Mostafavi MR, Ernst RD, Saltzman B, et al. Accurated determination of chemical composition of urinary calculi by spiral computerized tomography [J].J Urol,1998,159(3):673-675.
[25]Scheffel H,Stolzmann P,Frauenfelder T,et al. Dual-energy contrast-enhanced computed tomography for the.detection of urinary stone disease.Invest Radial, 2007,42:823-829.
[26]Stolzmann P, Schevel H, Rentsch K, et al. Dual energy computed tomography for the diferentiation of uric acid stones:exvivo perform ance evaluation. U rol Res,2008,36:133
[27]Graser A, Johnson TR, Chandarana H, et al. Dual energy CT:p reliminary observations and potential clinical app lications in the abdomen. Eur Radiol, 2009,19:13
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[40]BellinMF, Renard-Penna R, Conort P, et al. Helical CT evaluation of the chemical composition of urinary tract calculi with a discriminant analysis of CT-attenuation values and density. Eur Radiol 2004; 14:2134-2140.
[41]Deveci S, Coskun M, Tekin MI, et al.Spiral computed tomography:role in determination of chemical composition of pure and mixed urianry stones -an in vitro study [J]. J Urol,2004,64(2):237-340
[42]Graser, Anno; Johnson, et al. Dual Energy CT Characterization of Urinary Calculi:Initial In Vitro and Clinical Experience. Investigative Radiology: 2008,43(2):112-119
1.140/80Kv双能量扫描时,使用CT差值和DEI作为指标,无论是尿酸结石、胱氨酸结石、草酸钙结石、磷酸盐结石,其差异均有显著统计学意义,可以作为鉴别结石化学成分的有效指标；
2. 双源CT双能量尿结石分析技术将尿酸结石标记为红色,非尿酸结石标记为蓝色；双能量CT扫描不仅能区分尿酸和非尿酸结石,而且能对草酸钙结石、磷酸盐结石、胱氨酸结石做进一步鉴别,提供了一种无创的结石化学成分分析方法。
[1]叶章群.泌尿系结石研究现况于展望.中华实验外科杂志.2005,22(3)：261-262
[2]叶章群,邓耀良,董诚主编.泌尿系结石.北京：人民卫生出版社,2003.3
[3]Ouyang J M, Deng S P, Li X P, et al. Science in China, Ser. B,2004, 47 (4):311.
[4]NgoTC, AssimosDGUrie Acidnephrolithiasis:recent progress and future directions.Rev Urol.2007,9(1):17-27.
[5]NgCS, Streem SB.Contemporary management of cystinuria.J Endourol,1999, 13 (9):647-651
[6]Dretler SP:Stone fragility, a new therapeutic distinc- tion. j Urol 139: 1124-1127,
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