腹部加压控制下肝脏病灶移动度分析

目的 探索腹部加压条件下金标引导的肝脏病灶立体定向放疗(SBRT)的移动度及相关影响因素。方法 纳入2016—2019年间结直肠癌肝脏寡转移及原发性肝癌患者 20例,均在腹部加压条件下行SBRT。定位前于病灶周围2cm内植入 1~3枚金标,所有患者均采用4DCT模拟定位,根据呼吸信号重建出 0%~90%呼吸周期CT图像,并获取每次放疗前锥形束CT验证图像。将肝脏分为3个部分:肝门静脉主干2cm内、肝门静脉主干 2~5cm、肝门静脉主干5cm外肝脏,评价不同部位病灶的移动度范围。结果 整体肝脏平均分次内移动度在头脚、腹背、左右方向分别为(2.63±2.81)、(1.35±1.23)、(0.76±0.88)mm,平均分次间移动度分别为(3.45±3.06)、(2.64±2.60)、(2.23±2.07)mm,不管是分次内或分次间移动度均表现为头脚方向>腹背方向>左右方向(均 P<0.001)。不同部位病灶移动度不同,距离门静脉越远分次内移动度越大,距离门静脉越近病灶移动度越小(均 P<0.05)。为覆盖95%整体人群置信区间,内靶区(ITV)边界范围需在左右、腹背、头脚方向分别外扩3.9、5.2、7.9mm;不同位置病灶外扩范围并不相同,距离门脉2cm内分别外扩4.3、4.4、6.1mm,距离门脉5cm外分别外扩3.5、7.3、9.7mm。所有位置病灶均以头脚方向动度最显著。同时病灶距离门静脉越远头脚方向外扩范围越大,门脉周围5cm外病灶在腹背方向外扩范围也大于5cm内病灶。结论 不同位置的肝脏病灶ITV外扩边界不同,需个体化外扩ITV边界范围。

Four-dimensional computed tomography scan analysis of liver tumor motion treated with abdominal compression during stereotactic treatment

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 2cm 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 (Pinnacle³ 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 2cm from the main hepatic portal vein, 2-5cm from the main hepatic portal vein, and>5cm 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 (allP<0.001). The motion varied at different tumor locations. The longer distance from the main hepatic portal vein, the larger the intrafractional motion (allP<0.05). To cover the 95% population-based confidence interval, the internal target volume (ITV) was suggested to include the expansion of 3.9mm, 5.2mm and 7.9mm in the LR, AP and CC direction. The expansion of 4.3mm, 4.4mm and 6.1mm was delivered within 2cm from the main hepatic portal vein, and 3.5mm,7.3mm and 9.7mm>5cm 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 > 5cm from the main portal vein in the AP direction was larger than that ofinner parts. Conclusion Liver tumors at different locations require individual external expansion of ITV.