| Part one The ability of dual-energy dual-phase CT for small (diameter≤3cm) clear cell renal cell carcinomaObjective To evaluate the ability of dual-energy dual-phase CT for small (diameter≤3cm) clear cell renal cell carcinoma qualitatively and quantitively.Materials and Methods This study was a retrospectively single-institutional study and was approved by our institutional review board and the informed consent requirement was waived. Pathologically confirmed27cases of small (diameter≤3cm) ccRCCs (19cases of male and6cases of female, mean age54, range from31to73, one patient with three lesions) underwent dual-energy biphase (early corticomedullary and delayed phase) scan preoperatively between Oct2010and March2012. The early corticomedullary and delayed phase was after the administration of contrast agent20s and240s, respectively. Image qualitative analyse was finished by two senior radiologists in consensus. The discovery of the lesion was defined as the enhancement in the early corticomedullary phase, the pseudocapsule displayed and appeared as a hypoattenuation lesion in the delayed phase. The clearness degree was marked as5points in the80KV,140KV and120KV images:1. Not visible2. Doubtful visible3. Not obvious, need to regulate the window width4. Visible5. Definitely visible.2or lower than2level mean no lesion was found and3or higher level mean the discovery of the lesion. All the images were evaluated in the350and40window width. Image quantitive analyse was finished by another two radiologists blinded to the pathologic results. The attenuation of the lesions and adjacent renal parenchyma, the SD value of the anterior abdomen fat and define it as the noise. The CNR, LKR and the Learly-Ldelay value were calculated and choose the best phase and sequence for the display of the small ccRCCs.Results1. Qualitative analyse:Among the pathologically confirmed27lesions of small (diameter≤3cm) ccRCCs (one patient with three lesions), there were15lesions located in the left kidney and12lesions located in the right kidney. The mean maximum transverse diameter was2.2cm (range from1.1cm to3cm). The definitely visible lesions displayed in80KV images were the most, there were20lesions in the early corticomedullary phase while26lesions in the delayed phase, both more than the120KV images. There were21lesions (77.8%) found in the early corticomedullary phase while27(100%) lesions found in the delayed phase, and there was difference between the two phases (x2=5.808, P=0.025).2. Quantitative analysea:The attenuation of the lesions and renal parenchyma was higher in the early corticomedullary phase than the delayed phase, and80KV images could acquired the highest CT value. The noise was highest in the80KV images and lowest in the120KV images. The CNR value of the lesions and renal parenchyma was higher in the80KV images than the120KV images. The LKR value was higher in the early corticomedullary phase than the delayed phase, and closer to1. The change between the early corticomedullary phase and the delayed phase in the80KV images was the most distinct.Conclusion1. The CT attenuation of lesion and the change between lesion and kidney were both higher in DECT80KV images than in the average weighted120KV images, which diagnostic value was similar to the single energy CT images.2. The early corticomedullary phase was better than the delayed phase in the determination of the ccRCC and the delayed phase was better than the early corticomedullary phase in the lesions detection, which was similar to the findings with single energy CT.Part two The differentiating significance for the subtypes of renal cell carcinoma with dual-energy dual-phase enhanced CTObjective The purpose of our study was to differentiate subtypes of renal cell carcinoma with dual-energy dual-phase enhanced CT.Materials and methods This was a retrospective single-institutional study and was approved by our institutional review board and the informed consent requirement was waived. Between October2009and June2011,92patients (one patient with three clear cell renal cell carcinoma and one patient with two papillary renal cell carcinoma) who underwent an early corticomedullary phase (ECM) and a delayed phase (EP) in dual-energy scan were retrospectively reviewed. The early corticomedullary and delayed phase was after the administration of contrast agent20s and240s, respectively. There were77lesions with clear cell renal cell carcinoma (ccRCCs),11lesions with papillary renal cell carcinoma (pRCCs) and7lesions with chromophobe renal cell carcinoma (chRCCs). We compared the morphologic and enhancement features of the tumors with dual-energy CT. The attenuation values (HU) were recorded for each mass on the early corticomedullary and delayed phases. Then calculate the ratio of attenuation on80KV and140KV (r80/140KV). We also measured the iodine concentration of the lesion and the aorta in the early corticomedullary phase (ECM) and delayed phase (EP), calculate the normalized iodine concentration (NIC). Meanwhile, we compared the morphologic and enhancement features of high and low grade ccRCC and the type1and type2pRCC.Results:The value of r80/140KV for clear cell subtype was higher than for chromophobe RCC (P=0.003) and for papillary RCC (P=0.000) in ECM, meanwhile the value of r80/140KV for chromophobe RCC was also higher than for papillary RCC (P=0.040). The change of enhancement in ECM and EP had the greatest value in80KV images. The change of ccRCCs was greater than chRCC (P<0.001) and pRCC (P<0.001), while the change of chRCC was also greater than pRCC (P=0.032) in80KV images. The CT attenuation and the value of NIC in ECM and EP were both higher in clear cell subtype than the non-clear cell subtype (P<0.05). There was no difference in the CT attenuation and the value of NIC between chRCC and pRCC. Heterogeneity in the ECM and EP was more common in the clear cell subtype than in the non-clear cell subtype (P<0.05), and the difference ECM was more significant (P<0.001).The size of the high grade ccRCC was larger than the low grade ccRCC (P=0.007), but there was no difference in heterogeneity, attenuation and the value of r80/140KV between the high and low grade ccRCC both the ECM and EP. The value of r80/140KV for type2pRCC was higher than for type1pRCC in EP (P=0.017), but there was no difference in size, heterogeneity and attenuation between type1pRCC and type2pRCC.Conclusion:1. DECT could differentiate the clear cell and non-clear cell renal cell carcinoma, which was similar to the findings with single energy CT.2. There was higher CT attenuation in DECT80KV images, which could magnify the enhancement change between the subtypes of renal cell carcinoma. Meanwhile, DECT could show the enhancement change in the lesion and provide clues for the cell differentiation.3. The tissue distinguishability of DECT was higher and could provide more information for the cell differentiation and the distinguish of renal cell carcinoma subtypes.4. DECT could differentiate the high and low grade clear cell renal cell carcinoma as well as the type1and type2papillary renal cell carcinoma preliminarily. |
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