Utility of Intermediate-Delay Washout CT Images for Differentiation of Malignant and Benign Adrenal Lesions: A Multivariate Analysis

Abstract

OBJECTIVE. The objective of this study was to identify features that impact the diagnostic performance of intermediate-delay washout CT for distinguishing malignant from benign adrenal lesions. MATERIALS AND METHODS. This retrospective study evaluated 127 pathologically proven adrenal lesions (82 malignant, 45 benign) in 126 patients who had undergone portal venous phase and intermediate-delay washout CT (1–3 minutes after portal venous phase) with or without unenhanced images. Unenhanced images were available for 103 lesions. Quantitatively, lesion CT attenuation on unenhanced (UA) and delayed (DL) images, absolute and relative percentage of enhancement washout (APEW and RPEW, respectively), descriptive CT features (lesion size, margin characteristics, heterogeneity or homogeneity, fat, calcification), patient demographics, and medical history were evaluated for association with lesion status using multiple logistic regression with stepwise model selection. Area under the ROC curve (Az) was calculated from both univariate and multivariate analyses. The predictive diagnostic performance of multivariate evaluations was ascertained through cross-validation. RESULTS. Az for DL, APEW, RPEW, and UA was 0.751, 0.795, 0.829, and 0.839, respectively. Multivariate analyses yielded the following significant CT quantitative features and associated Az when combined: RPEW and DL (Az = 0.861) when unenhanced images were not available and APEW and UA (Az = 0.889) when unenhanced images were available. Patient demographics and presence of a prior malignancy were additional significant factors, increasing Az to 0.903 and 0.927, respectively. The combined predictive classifier, without and with UA available, yielded 85.7% and 87.3% accuracies with cross-validation, respectively. CONCLUSION. When appropriately combined with other CT features, washout derived from intermediate-delay CT with or without additional clinical data has potential utility in differentiating malignant from benign adrenal lesions.

Relative Enhancement Ratio of Portal Venous Phase to Unenhanced CT in the Diagnosis of Lipid-poor Adrenal Adenomas

“…In our study, lipid-poor adenomas showed a lower unenhanced attenuation than nonadenomas (22 HU 6 6 vs 34 HU 6 7; P , .001), as in previous studies (5,(9)(10)(11)(12)(19)(20)(21)(22). Additionally, the absolute enhancement of adenomas was 1.5-fold higher than nonadenomas (P , .001), which is also corroborated by data from numerous studies wherein adenomas had higher (up to 2.2-fold) absolute enhancement compared with nonadenomas, mostly comprising metastases (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)14,16,22,29,30) (Table E4 [online]). We introduced a new imaging parameter of relative enhancement ratio by combining unenhanced attenuation and absolute enhancement, yielding a diagnostic performance almost comparable with the previously reported washout CT (sensitivity, 86% vs 82%-92%; specificity, 95% vs 87%-100%) for the discrimination of lipid-poor adenomas (5,9,10,21).…”

“…A total of 29 relevant articles from the literature were reviewed (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(14)(15)(16)19,20,(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). Sixteen studies provided data on both adenomas (n = 964) and nonadenomas mostly comprising metastases (n = 623), all of which showed higher absolute enhancement in adenomas than in nonadenomas (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)14,16,22,29,30) (Table E4 [online]).…”

“…A total of 29 relevant articles from the literature were reviewed (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(14)(15)(16)19,20,(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). Sixteen studies provided data on both adenomas (n = 964) and nonadenomas mostly comprising metastases (n = 623), all of which showed higher absolute enhancement in adenomas than in nonadenomas (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)14,16,22,29,30) (Table E4 [online]). Of the 13 articles providing data on both adenomas and hypervascular nonadenomas, 10 studies (759 adenomas vs 234 pheochromocytomas, 56 adrenocortical carcinomas, and 24 metastases from RCC or HCC) showed higher or equivalent absolute enhancement in adenomas than in hypervascular nonad- Note....…”

“…Despite the reported excellent performance, washout CT requires early postcontrast imaging plus a 15-minute delayed phase, which makes it a relatively clinically inefficient and high-radiation dose option. Although the feasibility of shorter (3-10-minute) delayed protocols has been examined (11)(12)(13)(14), some studies have highlighted limited diagnostic yields due to insufficient washout period (13)(14)(15). Furthermore, these shorter delay methods do not reduce radiation dose.…”

A Bayesian Nonparametric Model for Textural Pattern Heterogeneity

“…Flexible for actual applications, our modelling framework facilitates pattern identification with analyses of cohorts with heterogeneous lesion sizes. Our unsupervised Bayesian model is applied to identify textural patterns intrinsic to adrenal lesions with CT. Data were obtained in a retrospective study of patients who underwent concordant biopsy and imaging based on a dynamic sequence of CT scans with and without administration of contrast (Ng et al., 2018a,b,c). To elucidate whether textural subtypes identified exhibit pathological orientation, subtypes are evaluated for correspondence with each lesion’s diagnosed pathological status.…”