Preliminary Study Of CT Spectral Imaging In The Diagnosis Of Renal Cell Carcinoma

ObjectiveTo evaluate the possibility and effectiveness for differentiating cysticrenal cell carcinoma (cRCC) and renal cyst, and to evaluate the correlationof pathologic grading of clear cell renal cell carcinoma (ccRCC) with CTspectral parameters, by using Gemstone Spectral Imaging (GSI), so as toprovide a novel and reliable imaging method for the diagnosis, differentialdiagnosis of renal cell carcinoma.Materials and methodsPart1: Value of spectral imaging in the differential diagnosisof cystic renal cell carcinoma and renal cystWe retrospectively analyzed the GSI scanning data of11cRCCs and20renal cysts. All the patients underwent a conventional pre-enhancementscan and an arterial-portal dual phases GSI scan(Discovery CT750HD，GE Healthcare，Milwaukee，USA), except for3cases of cRCC withoutportal venous phase scan. The original data and the reconstructed imageswere transmitted to the Advanced Workstation (AW4.4) for analysis andpost-treatment. ROI (Region Of Interest) was placed in the cystic areaavoiding the soft-tissue components. A file including monochromatic CTattenuation of the ROIs from40-140keV (with10keV intervals), iodine-water and calcium-water paired base materials concentration, effectiveatomic number (Effective-Z), was saved and the spectral curve (spectralHounsfield unit curve) was recorded. The slope of the curve was calculated ask=CT attenuation(70keV) CT attenuation(40keV)/30. Monochromatic CTvalues, slope of the spectral curve, paired materials concentration of iodine-water and calcium-water, and effective-Z were compared between thetwo groups by independent sample t-test with software SPSS21.0. Weused the ROC curve (Receiver Operating Characteristic curve) to producethe thresholds of the efficient parameters for the diagnosis of cRCC, andevaluated the ability for those parameters in the diagnosis by comparingthe AUC (Area Under roc Curve), and calculated the sensitivity, specificityof optimal thresholds.Part2: Study of the pathologic and CT spectral imagingcorrelation of ccRCCWe retrospectively analyzed clinical and CT scanning data of37patients with ccRCC (36cases were unilateral,1was bilateral, so a total of38lesions). Tumors were divided into2groups according to thepostoperative pathological grading (nuclear grade of Fuhrman), group Afor well-differentiated tumors (FuhrmanⅠ-Ⅱ), and group B forpoorly-differentiated tumors (FuhrmanⅢ-Ⅳ). All these patients underwenta conventional pre-enhancement scan and arterial-portal dual phasesGSI scan(Discovery CT750HD，GE Healthcare，Milwaukee，USA). Theoriginal data and the reconstructed images were transmitted to theAdvanced Workstation (AW4.4) for analysis and post-treatment. Thetumor location, size, shape, calcification, necrosis, enhancement mode,enhancement homogeneity and the CT attenuation of each phase onconventional CT images were recorded. ROI for spectral analysis wasplaced on the slice of the largest portion of tumor, and in thesolid-component avoiding the necrosis area as well as in the aorta of thesame slice. We recorded the monochromatic CT attenuation of the ROIsfrom40-140keV (with10keV intervals), iodine-water paired base materials concentration, and effective-Z according to research needs. NIC(Normalized iodine concentration) was Calculated with the formula NIC=IClesion/ICaorta. IClesion and ICaorta represent the iodine concentrationof lesion and aorta. Statistical analysis was made by using the software ofSPSS21.0. The gender, tumor location, symptom, shape, calcification,necrosis, enhancement, and homogeneity were compared by chi square test.The age, tumor size, CT attenuation on140kVp, monochromatic CTattenuation on each energy level, the slope of spectral curve, paired basematerials concentration (iodine-water), NIC, and effective-Z werecompared by independent sample t-test.ResultsPart1: Value of spectral imaging in the differential diagnosisof cystic renal cell carcinoma and renal cyst.1) Comparison of spectral specific parameters between cRCC and renalcyst.In this study, the monochromatic CT values of cRCC were higherthan those of the cyst in both arterial and portal phase, and the differenceswere statistically significant (P<0.05) except for that of140keV in portalphase. There is a significant difference for the shape of spectral curvesbetween these two groups, and the mean slope for cRCC was significantlylower than that of the renal cyst (P<0.05).In the aspect of paired base materials concentration and theeffective-Z, cRCC showed significantly higher iodine concentration,calcium concentration and effective-Z than renal cyst (P<0.05). However,there was no significant difference between these two groups for thewater-iodine or water-calcium concentration (P>0.05). 2) The performance of using spectral parameters to diagnose cRCC.The AUC of each spectral parameter was greater than0.91, and theAUC of40keV monochromatic CT attenuation were0.968and0.969inAP and PP. The CT value at40keV was the most accuracy parameteramong them. For diagnosing cRCC, the threshold of40keVmonochromatic CT attenuation was50HU, with sensitivity, specificity of91%,90%in arterial phase and90%to88%in portal phase.Part2: Study of the pathologic and CT spectral imagingcorrelation of ccRCC.The clinical information (gender, age, symptom and tumor location)has no difference between well-differentiated group andpoorly-differentiated group (P>0.05). In conventional CT manifestations,well-differentiated group had no statistical difference withpoorly-differentiated group in tumor size, shape, necrosis, calcification,enhancement pattern, enhancement homogeneity and CT attenuation(P>0.05).For the spectral CT parameters, the spectral curves of those twogroups of tumors showed almost the same shape, and monochromatic CTattenuation, as well as iodine-water paired base materials concentrationand effective-Z had no significant differences between the two groups(P>0.05).ConclusionOur study showed that:1) There was a significant difference of spectral CT characteristicsbetween cRCC and renal cyst for their cyst fluid. The monochromatic CT attenuation of40keV was useful for the diagnosis of cRCC. Using athreshold of50HU to diagnose cRCC showed a high accuracy, withsensitivity, specificity of91%,90%in arterial phase and90%,88%inportal phase. GSI scan mode can provide novel information for thedifferential diagnosis between cystic renal cell carcinoma and renalcyst.2) Well-differentiated ccRCC showed no significant difference in generalclinical information, conventional CT manifestations and spectral CTspecific parameters with poorly-differentiated ccRCC. CT spectralimaging cannot make an accurate prediction of tumor’s Fuhrman gradefor the moment.