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.

在这项研究中，我们旨在通过基于体模的研究进一步评估超声跟踪在放射治疗期间胰腺肿瘤分割内运动的准确性。

本研究招募了 12 名接受立体定向放射治疗的胰腺癌患者。呼吸周期的位移点是从 4DCT 获取的，并转移到运动平台上，以在我们的体模研究中模拟真实的呼吸运动。将超声腹部体模放置并固定在运动平台上。通过跟踪连接到该幻影的光学跟踪器记录幻影运动的基本事实。幻影内的一个肿瘤是跟踪目标。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了比较。通过计算均方根误差，分析了红外监测运动与超声跟踪运动的差异。

82.2% 的超声跟踪运动在超声跟踪位移和红外监测运动之间的 0.5 mm 差异值内。0.7% 的超声跟踪未能准确跟踪（差值 > 2.5 mm）。通过线性回归分析，超声跟踪运动和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。

这项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潜在的实时监测目标的方法，可以更准确地传递辐射剂量。