Optimizing the Imaging Scheme of Small-Dose Contrast Agent in 4D-CT Localization Enhancement Scan for Radiotherapy of Liver Cancer

Abstract

The primary liver cancer radiation therapy 4D-CT-enhanced (CE-4DCT) scan can accurately reflect the state of the liver as it moves with respiration, and enables clear visualization of the tumor, providing a precise range for target area outlining. However, the CE-4DCT scan localization time of primary liver cancer is long, and the fixed delay time of diagnostic CT cannot obtain high-quality 4DCT images. To this end, we designed a randomized controlled study to investigate the ideal localization scan delay time parameters for primary liver cancer CE-4DCT. Patients with primary hepatocellular carcinoma who presented to our department for radiotherapy CT localization from January to December 2022 participated in this study. All subjects were randomly divided into two groups in a 1:1 ratio. CE-4DCT scans were performed using a high concentration of iodomepril (400 mg/ml) contrast agent with a contrast volume equal to the patient's body weight. The scanning parameters were set according to scheme A (flow rate 2.0 ml/s, delay time 30s) and B (2.0 ml/s, 35s) respectively. Before the CE-4D CT scan, CT plain scan was routinely performed, physicians measured the CT value (HU) of abdominal aorta, portal vein, left hepatic vein, middle hepatic vein, right hepatic vein, liver parenchyma and tumor lesion on CT40 time item and plain scan images respectively. The image quality was subjectively and qualitatively assessed. The image enhancement effect is divided into excellent, good, relatively poor and poor. A total of 18 patients were included in this study. Patient characteristics were well-balanced in both groups. There were statistical differences between the two groups (A vs B) in the abdominal aorta (226.66 ± 45.59 vs. 176.66 ± 32.84, p = 0.017), left hepatic vein (142.77 ± 24.41 vs. 164.88 ± 19.02, p = 0.048); in the portal vein, middle hepatic vein, right hepatic vein, liver parenchyma, and tumor lesions CT values were not statistically different. The comparison of all flat-scan images between the two groups was statistically significant. The comparison of all flat-scan images in both groups was statistically significant. The subjective qualitative assessment of the developing effect was excellent in 44.4% (33.3% vs. 11.1%), good in 16.7% (5.6% vs. 11.1%), and poor in 38.9% (16.7% vs. 22.2%) in both groups. image quality was slightly higher in group A than in group B, but did not reach statistical significance (χ2 = 1.088, p = 0.698). In patients with primary hepatocellular carcinoma with portal vein carcinoma thrombosis 83.33% subjectively evaluated poor results. Qualitatively acceptable enhanced images were obtained for primary hepatocellular carcinoma (CE-4DCT) localization scans with a delay time controlled at 30s when using the least amount of contrast agent and the same flow rate.