| Objective: To investigate the feasibility of adrenal Revolution CT perfusion imaging and evaluate the value of perfusion parameters in the differential diagnosis for different pathologic types of adrenal tumors.Materials and Methods: Between April 2016 and January 2018,all patients who underwent adrenal Revolution CT perfusion imaging before adrenalectomy in our hospital were retrospectively analyzed.A total of 48 patients were included in the study.Among these patients,37 cases were pathological confirmed as adrenocortical adenoma(12 functional adenomas and 25 non-functional adenomas),7 pathological confirmed pheochromocytomas and 4 patients having 6 metastases were confirmed by follow-up imaging.The adenoma group were divided into 15 lipid-poor adenomas with an unenhanced CT value greater than 10 HU and 22 lipid-rich adenomas with an unenhanced CT value less than 10 HU.The adrenal unenhanced CT scan was performed initially to determine whether adrenal lesions exit or not.CT perfusion scan was then performed with 16 cm detector,using z-axis coverage mode.The tube voltage and tube current was set according to the patients’ BMI.The CTP scanning was initiated 6 s after the injection of contrast,continuous scannnig was performed for the anterior 28 s,the data were then collected at 39 s,43 s,47 s,51 s,63 s,83 s,113 s,153 s,213 s,353 s and 593 s,respectively.The arterial,venous and delayed phase enhanced images were obtained at the time of 22 s,51 s and 153 s.Twenty-six consecutive volume acquisitions were contained and the total perfusion scanning time was 593 s.The location,size,unenhanced and enhanced CT attenuation numbers of tumors were recorded.The medical image registration technique(MATLAB perf 4d)was used to correct the displacement of perfusion images.The data was transmitted to GE AW4.6 workstation,and the perfusion images were analyzed using CT perfusion 4D body software.The abdominal aorta was selected as the input artery.When the ROI was placed,the perfusion software automatically generated the time density curve(TDC)of the abdominal aorta,and the pseudo-color pictures of the perfusion parameters were obtained including blood flow(BF),blood volume(BV),mean transit time(MTT),time to peak(TP)and permeability of surface(PS).The perfusion parameter measurements were completed by the two physicians.The consistency of the two observers’ measurements were evaluated.Comparison between lipid-poor and lipid-rich adenoma,functional and non-functional adenoma,lipid-poor adenoma and pheochromocytoma,lipid-poor adenoma and metastasis were tested using the independent sample t test or Mann-Whitney U test.The ROC curve was employed to analyze diagnostic efficiency of CT perfusion parameters for identifing different pathological adrenal tumors.The radiation dose indexes of unenhanced CT scan,enhanced CT scan and CTP were recorded and calculated.Results: There was not statistical difference of length and minimum width between lipid-poor adenoma and lipid-rich adenoma(P all > 0.05).The unenhanced CT value and enhanced CT values of lipid-poor adenoma were statistically higher than those of lipid-rich adenoma(P all < 0.05).The length and minimum width of non-functional adenoma were statistically higher than those of functional adenoma(P all < 0.05),while there was not statistical difference of unenhanced CT value and enhanced CT values between the two tumors(P all > 0.05).The length,minimum width,unenhanced CT value,arterial phase and delayed phase CT values of lipid-poor adenoma were statistically lower than those of pheochromocytoma(P all < 0.05),while there was not statistically different of the venous phase CT value bewteen the two tumors(P = 0.078). There was not statistical difference of length,minimum width,unenhanced CT value and enhanced CT values between lipid-poor adenoma and metastasis(P all > 0.05).Inter-observer agreement for all perfusion parameters was good(ICC or Spearman’s r values all > 0.85).There was not statistical difference of all perfusion parameters between lipid-poor adenoma and lipid-rich adenoma(P all > 0.05).PS value of functional adenoma was statistically lower than that of non-functional adenoma(2.83±5.27 vs.9.00±13.15 ml/(100g·min),P = 0.003),while there was not statistically different bewteen the two types of adenomas for BF,BV,MTT and TP measurements(P all > 0.05).MTT and TP values of lipid-poor adenoma were statistically higher than those of pheochromocytoma(19.18±5.65 vs.13.64±4.66 s,28.76±21.19 vs.23.15±5.81 s,P = 0.047 and 0.021,respectively),while there was not statistical difference of BF,BV and PS values bewteen the two tumors(P all > 0.05).BF and BV values of lipid-poor adenoma were statistically higher than those of metastasis(66.32±43.79 vs.36.02±43.91 ml/(100g·min),18.33±5.95 vs.8.04±6.28 ml/100 g,P = 0.014 and 0.003,respectively),while there was not statistical difference of MTT,TP and PS values bewteen the two tumors(P all > 0.05).The area under the ROC curve of PS value was0.793,and there were a sensitivity of 75%,a specificity of 84% and the threshold of3.21 ml/(100g·min)for differentiating functional adenoma from non-functional adenoma.The area under the ROC curve of MTT and TP values for differentiating lipid-poor adenoma and pheochromocytoma were 0.771 and 0.810,respectively.When the MTT value was 17.77 s,the sensitivity and specificity were higher for differentiating the two tumors with 80% and 85.7%.The area under the ROC curve of BF and BV values were 0.844 and 0.900,and there were a sensitivity of 93.3% and66.7%,and a specificity of 80% and 100% for differentiating lipid-poor adenoma from metastasis.The effective radiation dose of adrenal CT plain scan,simple CTP,enhanced CT scan and CTP(including enhanced CT scan)were(3.53 ± 0.76)m Sv,(14.00 ± 1.02)m Sv,(6.39 ± 0.74)m Sv and(20.40 ± 1.41)m Sv,respectively.Conclusion: Twenty-six phase consecutive CT perfusion scanning protocol can provide high-quality conventional three-phase enhanced images and effective quantitative perfusion data at lower radiation dose.CT perfusion imaging is valuable for differentiating different pathologic types of adrenal tumors,especially for lipid-poor adenoma and metastasis which is difficult to be identified by routine CT examination.BF and BV values can be used to identify both of them for higher diagnostic efficacy. |
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