SU‐E‐J‐154: Image Quality Assessment of Contrast‐Enhanced 4D‐CT for Pancreatic Adenocarcinoma in Radiotherapy Simulation

Abstract

Purpose:This study presents quantitative and qualitative assessment of the image qualities in contrast‐enhanced (CE) 3D‐CT, 4D‐CT and CE 4D‐CT to identify feasibility for replacing the clinical standard simulation with a single CE 4D‐CT for pancreatic adenocarcinoma (PDA) in radiotherapy simulation.Methods:Ten PDA patients were enrolled and underwent three CT scans: a clinical standard pair of CE 3D‐CT immediately followed by a 4D‐CT, and a CE 4D‐CT one week later. Physicians qualitatively evaluated the general image quality and regional vessel definitions and gave a score from 1 to 5. Next, physicians delineated the contours of the tumor (T) and the normal pancreatic parenchyma (P) on the three CTs (CE 3D‐CT, 50% phase for 4D‐CT and CE 4D‐CT), then high density areas were automatically removed by thresholding at 500 HU and morphological operations. The pancreatic tumor contrast‐to‐noise ratio (CNR), signal‐tonoise ratio (SNR) and conspicuity (C, absolute difference of mean enhancement levels in P and T) were computed to quantitatively assess image quality. The Wilcoxon rank sum test was used to compare these quantities.Results:In qualitative evaluations, CE 3D‐CT and CE 4D‐CT scored equivalently (4.4±0.4 and 4.3±0.4) and both were significantly better than 4D‐CT (3.1±0.6). In quantitative evaluations, the C values were higher in CE 4D‐CT (28±19 HU, p=0.19 and 0.17) than the clinical standard pair of CE 3D‐CT and 4D‐CT (17±12 and 16±17 HU, p=0.65). In CE 3D‐CT and CE 4D‐CT, mean CNR (1.8±1.4 and 1.8±1.7, p=0.94) and mean SNR (5.8±2.6 and 5.5±3.2, p=0.71) both were higher than 4D‐CT (CNR: 1.1±1.3, p<0.3; SNR: 3.3±2.1, p<0.1). The absolute enhancement levels for T and P were higher in CE 4D‐CT (87, 82 HU) than in CE 3D‐CT (60, 56) and 4DCT (53, 70).Conclusions:The individually optimized CE 4D‐CT is feasible and achieved comparable image qualities to the clinical standard simulation. This study was supported in part by Philips Healthcare.