Ji Tianlong, Feng Ziwei, Sun Edward, Ng Sook Kien, Su Lin, Zhang Yin, Han Dong, Han-Oh Sarah, Iordachita Iulian, Lee Junghoon, Kazanzides Peter, Bell Muyinatu A Lediju, Wong John, Ding Kai
Department of Radiation Oncology, The First Hospital of China Medical University, Shenyang, China.
Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins School of Medicine, Baltimore, MD, United States.
Front Oncol. 2022 Sep 27;12:996537. doi: 10.3389/fonc.2022.996537. eCollection 2022.
In this study, we aim to further evaluate the accuracy of ultrasound tracking for intra-fraction pancreatic tumor motion during radiotherapy by a phantom-based study.
Twelve patients with pancreatic cancer who were treated with stereotactic body radiation therapy were enrolled in this study. The displacement points of the respiratory cycle were acquired from 4DCT and transferred to a motion platform to mimic realistic breathing movements in our phantom study. An ultrasound abdominal phantom was placed and fixed in the motion platform. The ground truth of phantom movement was recorded by tracking an optical tracker attached to this phantom. One tumor inside the phantom was the tracking target. In the evaluation of the results, the monitoring results from the ultrasound system were compared with the phantom motion results from the infrared camera. Differences between infrared monitoring motion and ultrasound tracking motion were analyzed by calculating the root-mean-square error.
The 82.2% ultrasound tracking motion was within a 0.5 mm difference value between ultrasound tracking displacement and infrared monitoring motion. 0.7% ultrasound tracking failed to track accurately (a difference value > 2.5 mm). These differences between ultrasound tracking motion and infrared monitored motion do not correlate with respiratory displacements, respiratory velocity, or respiratory acceleration by linear regression analysis.
The highly accurate monitoring results of this phantom study prove that the ultrasound tracking system may be a potential method for real-time monitoring targets, allowing more accurate delivery of radiation doses.
在本研究中，我们旨在通过基于体模的研究进一步评估放疗期间胰腺肿瘤分次内运动的超声跟踪准确性。
本研究纳入了12例接受立体定向体部放射治疗的胰腺癌患者。呼吸周期的位移点从4DCT获取，并转移到运动平台，以在我们的体模研究中模拟真实的呼吸运动。放置一个超声腹部体模并固定在运动平台上。通过跟踪附着在该体模上的光学跟踪器记录体模运动的真实情况。体模内的一个肿瘤作为跟踪目标。在结果评估中，将超声系统的监测结果与红外摄像机的体模运动结果进行比较。通过计算均方根误差分析红外监测运动与超声跟踪运动之间的差异。
82.2%的超声跟踪运动在超声跟踪位移与红外监测运动之间的差值0.5毫米范围内。0.7%的超声跟踪未能准确跟踪（差值>2.5毫米）。通过线性回归分析，超声跟踪运动与红外监测运动之间的这些差异与呼吸位移、呼吸速度或呼吸加速度无关。
该体模研究的高精度监测结果证明，超声跟踪系统可能是一种实时监测目标的潜在方法，可实现更精确的放射剂量递送。
