Study On Imaging Characterization Of Adrenal Masses With Soft Tissue Density

Part Ⅰ Differential Diagnosis of Adrenal Lipid poor Adenomas and Non-adenomas on CTObjective To evaluate the clinical value of CT histogram analysis and shorter delayed contrast material-enhanced computed tomography(CT)in distinguishing varying degrees of lipid poor adrenal adenomas from non-adenomas,and compare the diagnostic values of enhanced CT at different delay times.Materials and Methods 1.The retrospective study included 190 adrenal soft tissue masses with unenhanced CT attenuation greater than 10HU(140 lipid poor adenomas and 50 non-adenomas)in 188 patients [73 men,113 women;age range 13-77 years,mean age 49.5(14.1)years] who were clinically diagnosed at the Tianjin Medical University General Hospital from January 2010 to June 2018.All patients underwent unenhanced CT scans,followed by delayed enhanced CT scans at 30-sec,60-s,3-min,5-min,and 7-min delay times before the surgery.2.Record and compute the size;mean unenhanced attenuation values;percent negative pixels;early enhancement peaks;wash-in attenuation(WI);delayed enhanced attenuation,wash-out attenuation(WO),absolute percentage washout(APW)and relative percentage washout(RPW)at 3-,5-and 7-min of the lesions.Lipid poor adenomas were divided into two subgroups based on the mean unenhanced attenuation values: moderate density of lipid poor adenomas group(n=82),>10HU to ≤30HU;high density of lipid poor adenomas group(n=58),>30HU.3.The efficacy of each parameter for the differentiation of varying degrees of lipid poor adenomas from non-adenomas was assessed by generating receiver operating characteristic(ROC)curve.To compare the area under the ROC curve(AUC)of CT histogram analysis and enhanced CT scan at 3-,5-,7-min delay times for the diagnosis of varying degrees of lipid poor adenomas,and determine the optimal diagnostic threshold of each parameter and the associated sensitivity and specificity.Results 1.Among all parameters,percent negative pixels(≥10%)yielded the highest diagnostic effciency(sensitivity 100%,specificity 74%,accuracy 90.15%),followed by RPW ≥35.48%(sensitivity 85.37%,specificity 90%,accuracy 87.12%)at 7-min delayed enhanced CT for the discrimination between moderate density of lipid poor adenomas and nonadenomas.2.Among all parameters,RPW(≥ 35.48%) at 7-min delayed enhanced CT(sensitivity 74.14%,specificity 90%,accuracy 81.48%)and RPW(≥ 29.29%)at 5-min delayed enhanced CT(sensitivity 79.31%,specificity 88%,accuracy 82.41%)had relatively high diagnostic effciency for the differention of high density of lipid poor adenomas from nonadenomas.3.Among all parameters,RPW(≥ 35.48%) at 7-min delayed enhanced CT(sensitivity 80.71%,specificity 90%,accuracy 83.16%)had the highest diagnostic value,followed by APW(≥ 48.36%)at 7-min delayed enhanced CT(sensitivity 85%,specificity 76%,accuracy 82.11%)for the discrimination between total lipid poor adenomas and nonadenomas.4.There were no significant differences between the percent negative pixels and the RPW at 3-min delayed enhanced CT in the area under the ROC curve(AUC)for the diagnosis of moderate density of lipid poor adenomas and total lipid poor adenomas;and statistical differences were obtained in AUC values of the delayed enhanced attenuation,APW,RPW with the exception of the WO between 3-min and 5-min delayed enhanced CT scan,and the values of the former were lower than that of the latter;whereas there were no significant differences between 5-min and 7-min delayed enhanced CT scan in AUC values of the WO,APW or RPW except for the delayed enhanced attenuation.5.There were significant differences between the percent negative pixels and the RPW at 3-min delayed enhanced CT in AUCs for the discrimination of high density of lipid poor adenomas from non-adenomas,,and the values of the former were lower than that of the latter;while no significant differences were observed in AUC values of WO,APW,and RPW between 3-min and 5-min or between 5-min and 7-min delayed enhanced CT scans.Conclusions 1.The diagnostic values of size,early enhancement peaks,WI and delayed enhanced attenuation of adrenal masses for distinguishing adrenal lipid poor adenomas from non-adenomas are limited;whereas the efficiencies of percent negative pixels,WO,APW and RPW are relatively high,especially the RPW is the best;in addition,a combination of some of these parameters can improve the specificity for the diagnosis.2.It is recommended to further measure the percentage of negative pixels by using CT histogram analysis for the adrenal masses with unenhanced attenuation between 10 HU and 30HU;while for the lesions with unenhanced attenuation greater than 30 HU,a conventional abdominal enhanced CT scan is recommended and absolute or relative percentage washout is computed.3.There were no significant differences between the 5-min and 7-min delayed enhanced CT scan in diagnostic values for adrenal lipid poor adenomas.Part Ⅱ Typical and Atypical Imaging Features of Adrenal PheochromocytomasObjective To summarize the typical and atypical CT and MRI appearances of adrenal pheochromocytoma and improve the accuracy of adrenal pheochromocytomas characterization.Materials and Methods 1.The clinical and imaging data of 114 tumors in 110 patients [49 males and 61 females;age range 15-83 years,mean age 49.1(14.5)years] with adrenal pheochromocytomas confirmed by surgery and pathology at the Tianjin Medical University General Hospital from January 2010 to November 2018 were retrospectively analyzed,and the CT and MRI features of the lesions were summarized.2.In each tumor the following imaging variables were recorded: location,morphology and size,imaging appearance(solid homogeneous,solid heterogeneous,predominantly cystic),CT attenuation on all phases,presence or absence of calcifications,enhancement relative to spleen on CT,relative percentage washout at 7-min delayed enhanced CT,T2-weighted signal intensities,presence or absence of intracellular lipid on chemical-shift T1-weighted images and presence or absence of hemorrhage.The data acquired above were stored and calculated by Microsoft Excel 2016 software.Only simple descriptive statistics(average,percentage,standard deviation)were used in the study.Results 1.There were 114 lesions in the group(4 patients had bilateral masses).54 lesions were found in the left adrenal gland and 60 in the right adrenal gland.The size of the lesions ranged from 1.44 cm to 13.4 cm,with an average of(4.91±2.12)cm.Among these lesions,more than half(58.77%)of the tumors had sizes less than 5 cm,only about 3.51% of the lesions had sizes more than 10 cm,and the remaining(37.72%)had sizes between 5 and 10 cm.The unenhanced CT attenuation of lesions ranged from 16.01 HU to 57.45 HU,with an average of(41.63±7.47)HU.2.Most of the lesions(87.72%)were circular or ovoid in morphology,while a few(12.28%)were irregularly lobulated.Most of the lesions(CT,90%;MRI,86.21%)were heterogeneous,while a few(CT,10%;MRI,13.79%)appeared solid and homogeneous.3.About 24.44% of the lesions were more enhancing than the spleen,17.78% showed similar enhancement to the spleen,57.78% enhanced less than the spleen.The relative percentage washout at 7-min delay time of approximately 26.67% of the lesions were 34% or more.In addition,about 5.94% of the lesions had calcifications.4.When assessing the T2 signal intensity of the lesions on MRI,approximately 51.72% of the lesions had signal intensity higher than that of the spleen,34.48% had signal intensity similar to that of the spleen,13.79% had signal intensity lower than that of the spleen.5.Approximately 44.83% of the lesions were hemorrhagic on MRI.Only about 3.45% of lesions exhibited intracellular fat on chemical-shift MR images.Conclusions Pheochromocytomas were characterized by heterogeneity,high T2 WI signal intensity,marked enhancement and slow washout.Atypical imaging appearances included mild to moderate enhancement,intratumoral hemorrhage,rapid washout,homogeneity,calcification and intracellular lipid;among them,mild to moderate enhancement,intratumoral hemorrhage,rapid washout were relatively common in pheochromocytomas.