Differentiation of renal angiomyolipoma without visible fat from small clear cell renal cell carcinoma by using specific region of interest on contrast-enhanced CT: a new combination of quantitative tools

Abstract

Background To investigate the value of using specific region of interest (ROI) on contrast-enhanced CT for differentiating renal angiomyolipoma without visible fat (AML.wovf) from small clear cell renal cell carcinoma (ccRCC). Methods Four-phase (pre-contrast phase [PCP], corticomedullary phase [CMP], nephrographic phase [NP], and excretory phase [EP]) contrast-enhanced CT images of AML.wovf (n = 31) and ccRCC (n = 74) confirmed by histopathology were retrospectively analyzed. The CT attenuation value of tumor (AVT), net enhancement value (NEV), relative enhancement ratio (RER), heterogeneous degree of tumor (HDT) and standardized heterogeneous ratio (SHR) were obtained by using different ROIs [small: ROI (1), smaller: ROI (2), large: ROI (3)], and the differences of these quantitative data between AML.wovf and ccRCC were statistically analyzed. Multivariate regression was used to screen the main factors for differentiation in each scanning phase, and the prediction models were established and evaluated. Results Among the quantitative parameters determined by different ROIs, the degree of enhancement measured by ROI (2) and the enhanced heterogeneity measured by ROI (3) performed better than ROI (1) in distinguishing AML.wovf from ccRCC. The receiver operating characteristic (ROC) curves showed that the area under the curve (AUC) of RER_CMP (2), RER_NP (2) measured by ROI (2) and HDT_CMP and SHR_CMP measured by ROI (3) were higher (AUC = 0.876, 0.849, 0.837 and 0.800). Prediction models that incorporated demographic data, morphological features and quantitative data derived from the enhanced phase were superior to quantitative data derived from the pre-contrast phase in differentiating between AML.wovf and ccRCC. Among them, the model in CMP was the best prediction model with the highest AUC (AUC = 0.986). Conclusion The combination of quantitative data obtained by specific ROI in CMP can be used as a simple quantitative tool to distinguish AML.wovf from ccRCC, which has a high diagnostic value after combining demographic data and morphological features.

Fat-poor renal angiomyolipoma with prominent cystic degeneration: A case report and review of the literature

“…The early dark cortical band sign can be observed in up to 60% of clear cell RCC cases, facilitating the differential diagnosis from fat-poor AML with high specificity and PPV[ 17 ]. Some studies demonstrate that the combination of quantitative data obtained by specific region of interest in corticomedullary phase[ 18 ], convention-radiomics CT nomogram[ 19 , 20 ], and circularity index on CECT[ 21 ] help distinguish fat-poor AML from clear cell RCC. Magnetic resonance parameters may be of value in evaluating RCCs[ 5 , 22 ].…”

Use of specific contrast-enhanced CT regions of interest to differentiate renal oncocytomas from small clear cell and chromophobe renal cell carcinomas

“…First, an S-ROI (area: 10-20 mm 2 ) and an M-ROI (area: 50-100 mm 2 ) were placed in the tumor regions exhibiting the greatest degree of enhancement in CMP images ( Figure 2 ). These 2 ROIs were placed with the following considerations: (i) S-ROI and M-ROI placement in PCP and NP images should be based on the positioning and sizing used for CMP images; (ii) regions of intratumoral vasculature, cystic degeneration, central scarring, and calcification should be avoided, with care being taken to differentiate between blood vessels and tumor-rich blood supply lesions based on previously defined morphological characteristics 10 ( Figure 2 ); and (iii) each parameter should be measured 2 times, with the average value being recorded as the attenuation value of the tumor (AVT). An additional ROI should then be placed within the adjacent renal cortical region to measure the attenuation value of the cortex (AVC), allowing for the lesion-to-cortex attenuation (L/C) ratio to be measured as follows: (AVT/AVC) × 100%.…”

“… 7 - 8 Rosenkrantz et al 9 found the use of a small ROI (S-ROI) to be more accurate than a large ROI (L-ROI) when differentiating between RCCs and cysts, with this approach being most effective when comparing pRCCs and cysts. Wang et al 10 also reported that S-ROI-based enhancement degree and whole ROI (W-ROI)-based enhancement heterogeneity were superior to medium ROI (M-ROI) when differentiating between small ccRCC and fat-poor angiomyolipoma (AML).…”

Ultrasound-Guided Attenuation Parameter（UGAP）A Valuable Alternative in Differentiation between Renal Angiomyolipoma without Visible Fat and Clear Cell Renal Cell Carcinoma? A Pilot Study

“…The selection principles of the ROI were as follows [23], (Figure . 2). i) Contrast-enhanced CT was used to assess the edges and vessels of the mass for ROI measurements.…”