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Delay Time for Optimal Contrast-Enhanced CT Scans of Liver and Pancreas Tumors

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Y Suh

Y Suh1*, P Park1 , G Sawakuchi1 , S Beddar1 , E Koay2 , S Krishnan2 , B Minsky2 , C Taniguchi2 , E Holliday2 , J Herman2 , P Das2 , (1) Department of Radiation Physics, UT MD Anderson Cancer Center, Houston, TX, (2) Department of Radiation Oncology, UT MD Anderson Cancer Center, Houston, TX


SU-E-FS4-6 (Sunday, July 30, 2017) 1:00 PM - 1:55 PM Room: Four Seasons 4

Purpose: To present optimal delay time for intravenous contrast-enhanced CT simulation for liver and pancreas tumor visibility and delineation.

Methods: Seventy-eight patients who underwent multi-phase contrast-enhanced CT simulation of liver or pancreas between 2013 and 2015 were included in this study. Each simulation consisted of three to five breath-hold CT scans acquired one after another throughout the late arterial to portal venous to washout phases. Delay time, the time between the initiation of iodine-based contrast agent injection (150 ml at the rate of 5 ml/sec) and the start of CT image acquisition, was typically 30-45 sec (68 patients). but ranged from 25 to 75 sec. On a total of 387 CT datasets, points were placed in the regions of interest (ROIs) of liver parenchyma (924 points), liver tumor (172 for liver metastases and 129 for cholangiocarcinoma), pancreas parenchyma (343), pancreatic tumor (26), and aorta (310). CT numbers for these points were measured in HUs. Contrast enhancement of each ROI vs. time was evaluated and contrast differential between the tumor and surrounding parenchyma over time was assessed.

Results: Liver enhanced most 90 sec after the initiation of contrast injection by 60 HU. Liver metastases and cholangiocarcinoma enhanced most at 70-140 and 50-90 sec by 40 and 55 HU, respectively. Pancreas and pancreatic tumor enhanced most at 60 and 70 sec by 80 and 90 HU, respectively. Aorta enhanced most at 50 sec by 200 HU. From the comparison of the contrast enhancement of tumor and surrounding parenchyma over time, the delay time that maximizes the contrast differential between the two that objectively improves tumor visibility and delineation accuracy was determined.

Conclusion: Our results show that the optimal delay time for imaging liver metastases and cholangiocarcinoma is 70-90 and 130-165 sec, respectively, and that for pancreatic tumor is 80 sec or more.

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