Background/Objectives: An on-board imager on a linear accelerator allows the acquisition of kV-2D images during irradiation. Overlaying specific structures on these images enables the visual verification of movement at regular frequencies. Our aim was to validate this tracking method for the stereotactic treatment of bone metastases. Methods: Shifts in three translational directions were simulated using an anthropomorphic phantom. For these simulated shifts, planar images were acquired at different angles of incidence, with overlaid volumes of interest. A blinded test was then administered to the 18 participants to evaluate their decisions regarding whether to stop treatment. The results considered the experience of the operators. Quantitative analyses were performed on the intra-fractional images of 29 patients. Results: Participants analyzed each image with an average (standard deviation) decision time of 3.0 s (2.3). For offsets of 0.0, 1.0, 1.5, and 2.0 mm, the results were 78%, 93%, 90%, and 100% for the expert group and 78%, 70%, 79%, and 88% for the less-experienced group. Clinical feedback confirmed this guidance technique and extended it to non-spinal bony metastases. Sudden movements exceeding the 2.0 mm threshold occurred in 3.3% of the analyzed fractions, with a detection rate of 97.8% for vertebral locations. For non-vertebral bone locations, movements exceeding a threshold of 3.0 mm occurred in 3.5% of cases and were detected in 96.5%. Conclusions: The clinical use of planar OBI and superimposed structures for visual-image guidance in bone stereotactic treatment was validated using an anthropomorphic phantom and clinical feedback.
背景/目的：直线加速器上的机载成像器可在照射期间采集千伏二维图像。将特定结构叠加于这些图像上，可实现以固定频率对运动进行视觉验证。本研究旨在验证该追踪方法在骨转移瘤立体定向治疗中的应用。方法：使用人体模型模拟三个平移方向的位移。针对这些模拟位移，在不同入射角度采集平面图像，并叠加感兴趣区域体积。随后对18名参与者进行盲法测试，评估其是否决定停止治疗。结果分析考虑了操作者的经验水平。对29例患者的分次内图像进行定量分析。结果：参与者分析每幅图像的平均（标准差）决策时间为3.0秒（2.3）。在0.0、1.0、1.5和2.0毫米偏移条件下，专家组的结果分别为78%、93%、90%和100%，经验较少组的结果分别为78%、70%、79%和88%。临床反馈证实了该引导技术，并将其扩展至非脊柱骨转移瘤治疗。在分析的分次中，3.3%出现超过2.0毫米阈值的突发运动，椎体部位的检出率为97.8%。对于非椎体骨部位，3.5%的病例出现超过3.0毫米阈值的运动，检出率为96.5%。结论：通过人体模型实验和临床反馈，验证了平面OBI及叠加结构在骨立体定向治疗中用于视觉图像引导的临床应用价值。
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