Abstract：
External beam accelerated partial breast irradiation (APBI) is an alternative treatment for patients with early-stage breast cancer. The efficacy of image-guided radiotherapy (IGRT) using fiducial markers, such as gold markers or surgical clips, has been demonstrated. However, the effects of respiratory motion during a single fraction have not been reported. This study aimed to evaluate the residual image registration error of fiducial marker-based IGRT by respiratory motion and propose a suitable treatment strategy. We developed an acrylic phantom embedded with surgical clips to verify the registration error under moving conditions. The frequency of the phase difference in the respiratory cycle due to sequential acquisition was verified in a preliminary study. Fiducial marker-based IGRT was then performed in ten scenarios. The residual registration error (RRE) was calculated on the basis of the differences in the coordinates of clips between the true position if not moved and the last position. The frequencies of the phase differences in 0.0-0.99, 1.0-1.99, 2.0-2.99, 3.0-3.99, and 4.0-5.0 mm were 23%, 24%, 22%, 20%, and 11%, respectively. When assuming a clinical case, the mean RREs for all directions were within 1.0 mm, even if respiratory motion of 5 mm existed in two axes. For APBI with fiducial marker-based IGRT, the introduction of an image registration strategy that employs stepwise couch correction using at least three orthogonal images should be considered.
摘要：
外部束加速部分乳腺照射（APBI）是早期乳腺癌患者的替代治疗方法。使用基准标记的图像引导放射治疗（IGRT）的功效，如金标记或手术夹，已经被证明了。然而,在单个部分期间呼吸运动的影响尚未报道。本研究旨在通过呼吸运动评估基于基准标记物的IGRT的残余图像配准误差，并提出合适的治疗策略。我们开发了一种嵌入手术夹的丙烯酸体模，以验证移动条件下的配准误差。在初步研究中验证了由于顺序采集导致的呼吸周期中相位差的频率。然后在十种情况下执行基于基准标记的IGRT。残余配准误差(RRE)是基于不移动的真实位置与最后位置之间的剪辑的坐标差异来计算的。0.0-0.99、1.0-1.99、2.0-2.99、3.0-3.99和4.0-5.0mm的相位差频率分别为23%,24%,22%,20%,11%,分别。假设临床病例时，所有方向的平均RRE都在1.0毫米以内，即使在两个轴上存在5毫米的呼吸运动。对于具有基于基准标记的IGRT的APBI，应考虑引入使用至少三幅正交图像进行逐步沙发校正的图像配准策略。
