Four-Dimensional Computed Tomography Scan Analysis of Liver Tumor Motion Treated With Abdominal Compression During Stereotactic Treatment of Liver

Abstract

To explore the motion and influencing factors of implanted gold markers in guiding liver stereotactic body radiation therapy using abdominal compression.Twenty patients with oligometastatic colorectal cancer or primary hepatocellular carcinoma from January 2016 to December 2019 were included. All patients were treated with stereotactic body radiation therapy (SBRT) under abdominal compression, with 1-3 gold markers implanted within 2cm of the lesion before positioning, meanwhile four-dimensional computed tomography (4DCT) scan used for treatment planning. The respiratory cycle was divided into 0%-90% respiratory phase image based on the respiratory signal, which were reconstructed by the system as well as CBCT validation images before radiation exposure daily. The liver volume was divided into 3 parts: within 2 cm of the main hepatic portal vein, 2-5 cm of the main hepatic portal vein, and 5 cm outside of the main hepatic portal vein, for evaluating the motion of different tumor locations.The average intrafractional motion amplitude (mean ± standard deviation) was 2.63 ± 2.81 mm in the cranial-caudal (CC), 1.35 ± 1.23 mm in the anterior-posterior (AP), and 0.76 ± 0.88 mm in the left-right (LR) direction, respectively. Meanwhile the average interfractional motion amplitude was 3.45 ± 3.06 mm, 2.64 ± 2.60 mm, and 2.23 ± 2.07 mm, respectively. Whether intra- or interfraction, the motion amplitude showed CC > AP > LR direction (P < 0.001). The motion varied at different tumor location, the further away from the main hepatic portal vein, the larger of the intrafractional motion. To cover the 95% population-based confidence interval, internal target volume was suggested to include the expansion of 3.9 mm, 5.2 mm and 7.9 mm in the LR, AP, and CC direction, while 4.3 mm, 4.4 mm, and 6.1 mm within 2 cm of the main hepatic portal vein, 3.5 mm, 7.3 mm, and 9.7 mm outside 5 cm of the main hepatic portal vein, respectively. The expansion varied significantly depending on tumor location, but motion in CC direction showed the largest no matter where the tumor was. Among the 3 parts of liver volume, while the further of tumor away from the main portal vein, the larger expansion in CC direction, and tumor in 5 cm outside of the main portal vein moved more than other inner parts in AP direction.Different tumor locations of liver require external expansion of internal target volume individually.Y. Zhao: None. Y. Tang: None. W. Liu: None. N. Li: None. Y. Song: None. S. Wang: None. Y. Liu: None. H. Fang: None. N. Lu: None. Y. Tang: None. S. Qi: None. Y. Yang: None. B. Chen: None. Y. LI: None. J. Jin: None.