Wash-out of hepatocellular carcinoma: Quantitative region of interest analysis on CT

Abstract

Introduction: This study aims to determine if the quantitative method of region-of-interest (ROI) analysis of lesion attenuation on CT may be a useful adjunct to the conventional approach of diagnosis by visual assessment in assessing tracer wash-out in hepatocellular carcinomas. Materials and Methods: From a surgical database of 289 patients from 2 institutions, all patients with complete surgical, pathological and preoperative multiphasic CT scans available for review were selected. For each phase of scanning, HU readings of lesion obtained (Lesion arterial' Lesion PV and Lesion equilibrium) were analysed using receiver operating curves (ROC) to determine the optimal method and cut-off value for quantitative assessment of tumour wash-out (Lesion arterial - equilibrium' Lesion PV - equilibrium or Lesion peak - equilibrium). Results: Ninety-four patients with one lesion each met the inclusion criteria. The area under the curve (AUC) values for Lesion arterial - equilibrium (0.941) was higher than the AUC for Lesion pv - equilibrium (0.484) and for Lesion peak - equilibrium (0.667). Based on ROC analysis, a cut-off of 10HU value for Lesion arterial - equilibrium would yield sensitivity and specifi city of 91.5% and 80.9%, respectively. ROI analysis detected 9/21 (42.9%) of lesions missed by visual analysis. Combined ROI and visual analysis yields a sensitivity of 82/94 (87.2%) compared to 73/94 (77.7%) for visual analysis alone. Conclusion: Using a cut-off of 10 HU attenuation difference between the arterial and equilibrium phases is a simple and objective method that can be included as an adjunct to visual assessment to improve sensitivity for determining lesion wash-out on CT.