Four-dimensional computed tomography scan analysis of liver tumor motion treated with abdominal compression during stereotactic treatment / 中华放射肿瘤学杂志

ABSTRACT

Objective:To explore the motion and influencing factors of implanted gold markers in guiding liver stereotactic body radiation therapy (SBRT) using abdominal compression.Methods:Twenty patients with oligometastatic colorectal cancer or primary hepatocellular carcinoma from January 2016 to December 2019 were included. All patients were treated with SBRT under abdominal compression, with 1-3 gold markers were implanted within 2 cm from the lesion before positioning. Four-dimensional computed tomography (4DCT) scan was used for treatment planning. The respiratory cycle was divided into 0-90% respiratory phase images based on the respiratory signal, which were reconstructed by the system (Pinnacle 3 version 9.1; Philips Medical System, Madison, WI, USA), and cone beam CT validation images before radiation exposure were obtained. The liver volume was divided into 3 parts within 2 cm from the main hepatic portal vein, 2-5 cm from the main hepatic portal vein, and>5 cm from the main hepatic portal vein. The motion of different tumor locations was evaluated. Results:The average intrafractional motion amplitude was (2.63±2.81) mm in the cranial-caudal (CC) direction, (1.35±1.23) mm in the anterior-posterior (AP) direction, and (0.76±0.88) mm in the left-right (LR) direction, respectively. The average interfractional motion amplitude was (3.45±3.06) mm, (2.64±2.60) mm, and (2.23±2.07) mm, respectively. Both the intra-or inter-fractional motion amplitudes in the CC direction were the highest, followed by those in the AP and LR direction (all P<0.001). The motion varied at different tumor locations. The longer distance from the main hepatic portal vein, the larger the intrafractional motion (all P<0.05). To cover the 95% population-based confidence interval, the internal target volume (ITV) was suggested to include the expansion of 3.9 mm, 5.2 mm and 7.9 mm in the LR, AP and CC direction. The expansion of 4.3 mm, 4.4 mm and 6.1 mm was delivered within 2 cm from the main hepatic portal vein, and 3.5 mm, 7.3 mm and 9.7 mm>5 cm from the main hepatic portal vein, respectively. The expansion varied significantly depending on the tumor location, whereas the motion in the CC direction was the largest regardless of the tumor location. The longer distance of the tumor from the main portal vein, the larger expansion in the CC direction. The expansion of tumor > 5 cm from the main portal vein in the AP direction was larger than that of inner parts. Conclusion:Liver tumors at different locations require individual external expansion of ITV.