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 current clinical standard simulation with a single CE 4D-CT for pancreatic adenocarcinoma (PDA) in radiotherapy simulation as shown in Figure 1.

Materials/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-to-noise ratio (SNR) and  conspicuity  (C, absolute difference of mean enhancement levels in P and T) were computed in on the boundary of intersection region (Figure 2) to quantitatively assess image quality.

• The Wilcoxon rank sum test was used to compare these quantities.

Results

Image quality assessment of contrast-enhanced 4D-CT for

pancreatic adenocarcinoma in radiotherapy simulation

Wookjin Choi, Ming Xue, Min Kyu Kang, Kruti Patel, William Regine, Paul Klahr, Jiahui Wang, Warren D'Souza, Wei Lu.

Dept. of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USADept. of Radiation Oncology, Yeungnam University College of Medicine, Daegu, South Korea

Purpose

Supported in part by Philips Healthcare.*Contact: Wei Lu, Ph.D., wlu@umm.edu

Conclusion• An individually optimized CE 4D-CT replace the

current clinical standard simulation with a single CE 4D-CT for PDA in radiotherapy simulation based on the image quality assessment.

• CE 4D-CT achieved comparable image quality and contrast between tumor and normal pancreatic parenchyma to the clinical standard pair of CE 3D-CT and 4D-CT.

• In qualitative evaluations, CE 3DCT and CE 4DCT scored equivalently (4.4±0.4 and 4.3±0.4, p=0.55) and both were significantly better than 4DCT (3.1±0.6, p=0.0002 and 0.0004).

• In quantitative evaluations, the C values were higher in CE 4DCT (14±13 HU, p=0.13 and 0.03) than the clinical standard pair of CE 3DCT and 4DCT (6±7 and 3±2 HU, p=0.45).

• Figure 3 shows the qualitative evaluation and conspicuity on CE 3DCT, 4DCT and 4DCT.

• 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=0.11 and p=0.26; SNR: 3.3±2.1, p=0.03 and 0.10).

• The absolute enhancement levels for T and P were higher in CE 4D-CT (91, 97 HU, p=0.94) than in CE 3D-CT (61, 67, p=0.25) and 4D-CT (63, 64, p=0.76).

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Figure 3. Qualitative evaluation and Conspicuity on CE 3DCT, 4DCT and CE 4DCT.

Figure 1. CE 4D-CT replace the current clinical standard simulation with a single CE 4D-CT for PDA in radiotherapy simulation. Tumor (red) and pancreatic parenchyma (blue) contours on CE 3DCT, 4DCT, and CE 4DCT.

CE 3DCT 4DCT

Figure 2. Boundary of intersection region to calculate conspicuity of tumor (red) and pancreas (blue).

(a) (b) (c)

CE 4DCT

Clinical Standard

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