Study Of Value Of Energy Spectral CT For Evaluating Pathologic Grading Of Clear Cell Renal Cell Carcinoma Preoperatively

Objective:To investigate the value of spectral CT imaging for diagnosing pathologic grading of clear cell renal cell carcinoma(CCRCC) preoperatively and to assess the value of virtual non-contrast with spectral CT in clear cell renal carcinoma of triple-phase.Materials and methods:64 cases of CCRCC,which were confirmed surgically and pathologically,were analyzed retrospectively.All cases underwent TNCT and dual-phase contrast enhanced CT with GSI mode.Then they were divided into three groups:group A (CCRCC, Ⅰ grade),group B(CCRCC, Ⅱ grade) and group C(CCRCC, Ⅲ&Ⅳgrade). Spectral characteristic quantitative parameters and morphological qualitative parameters among different grades of CCRCC were compared. Analysis of variance and chi-square test were used for statistical analysis.The virtual non-contrast CT(VNCT) images of 64 cases were derived from the data of cortex phase using a dedicated software named material suppressed iodine(MSI).Between true non-contrast CT(TNCT) and VNCT imagings, the noise, the CT values of mass, and the total dose length product (DLP) were compared with paired t-test and the diagnostic sensitivity was compared with x2 test. The diagnostic accuracy of clear cell renal carcinoma between conventional renal triple-phase and VNCT combined with dual-phase contrast enhancement CT was compared with x2 test. Sensitivity and specificity were analyzed of high differentiation CCRCC from low differentiation CCRCC.Results:1. Spectral characteristic quantitative parameters of different grades CCRCC① In cortex phase, at the level of 40-70keV, single energy CT value of CCRCC of grade Ⅰ, Ⅱ, Ⅲ&Ⅳ had significant difference, Ⅱ> Ⅰ>Ⅲ&Ⅳ,P<0.05; at the level of 80～140keV,Ⅱ> Ⅰ,Ⅱ> Ⅲ & Ⅳ,P<0.05.There had no significant difference between Ⅰ and Ⅲ & Ⅳ. In parenchyma phase, at the level of 40～ 100keV, Ⅱ> Ⅰ, Ⅱ> Ⅲ & Ⅳ, P<0.05; at the level of 110～140keV,P<0.05.② Spectrum curve slope of CCRCC of grade Ⅰ, Ⅱ, Ⅲ & Ⅳ were 5.03±1.34,6.89±1.54,3.71±0.85,F=25.173,P<0.05 in cortex phase and 3.18±0.83, 3.84±0.86,2.57±0.59,F=14.871, P<0.05 in parenchyma phase.③ In cortex phase, iodine concentration,normalized iodine concentrations (NIC), calcium concentration ratio among three groups had significant difference Ⅱ> Ⅰ>Ⅲ & Ⅳ, P<0.05. In parenchyma phase, NIC and concentration ratio had statistical difference between different groups, Ⅰ>Ⅲ & Ⅳ,Ⅱ>Ⅲ & Ⅳ, P<0.05. The water concentration ratio of CCRCC of grade Ⅰ, Ⅱ,Ⅲ & Ⅳ in cortex and parenchyma phase had no statistically significant, P>0.05.2. Morphological qualitative parametersThe diameter, shape, pseudocapsule, liquefaction and necrosis of tumor had statistically significant between different groups. The CT value, calcification, and mode of enhancement of tumor had no significant difference.3. The analysis of receiver operating characteristic (ROC) curves of the single energy CT value and basic material concentration.In cortex phase,the area under the curve of iodine concentration,NIC,calcium concentration ratio were 0.889,0.771,0.768,0.885 respectively and the level of 40 ～ 70keV single energy were 0.857-0.873.The value of these parameters in cortex phase were higher than that in parenchyma phase.The diagnostic sensitivity and specificity were 90.3% and 87.5% when the thresholds of 40 keV monochromatic images was set at 423.03HU;the diagnostic sensitivity and specificity of iodine concentration were 90.3%,81.2% in cortex phase.4. VNCT of spectral CTVNCT had higher image noise than TNCT (t=-4.25, P<0.05). The mean CT values of tumors on VNCT images were similar with that of TNCT images (t=-1.723, P>0.05. Diagnostic sensitivity of VNCT was compatible with that of TNCT(92.7%, 90.9%, x 2=0.087, P>0.05). The total radiation dose of DLP in dual-phase contrast enhancement CT was lower than that of conventional renal triple-phase (t=7.07, P<0.05). Diagnostic accuracy of clear cell renal carcinoma between conventional renal triple-phase and VNCT combined dual-phase contrast enhancement CT had no significant difference (90.9%,89.1%,x2=0.101, P>0.05).Conclusions:1.The single energy CT value,basic material concentration and spectrum curve slope contribute to diagnosis the pathologic grading of CCRCC.2. The morphological characteristics of monochromatic energy imaging contribute to diagnosis the grading of CCRCC.3.The diagnostic efficiency are best at monochromatic energy level of 40 keV and iodine concentration in arterial phase. 4.GSI dual-phase imaging in renal will be a good substitute since the radiation dose can be greatly reduced compared with traditional triple-phase imaging and the degree of enhancement is helpful to diagnosis the pathologic grading of CCRCC.