Laaksomaa Marko, Kapanen Mika, Skyttä Tanja, Peltola Seppo, Hyödynmaa Simo, Kellokumpu-Lehtinen Pirkko-Liisa
Department of Oncology, Tampere University Hospital (Tays), PO Box 2000 (Teiskontie 35), FI-33521 Tampere, Finland.
Department of Oncology, Tampere University Hospital (Tays), PO Box 2000 (Teiskontie 35), FI-33521 Tampere, Finland ; Department of Medical Physics, Tampere University Hospital (Tays), PO Box 2000 (Teiskontie 35), FI-33521 Tampere, Finland.
Rep Pract Oncol Radiother. 2014 Jul 15;19(6):369-75. doi: 10.1016/j.rpor.2014.05.001. eCollection 2014 Nov.
The aim was to find an optimal setup image matching position and minimal setup margins to maximally spare the organs at risk in breast radiotherapy.
Radiotherapy of breast cancer is a routine task but has many challenges. We investigated residual position errors in whole breast radiotherapy when orthogonal setup images were matched to different bony landmarks.
A total of 1111 orthogonal setup image pairs and tangential field images were analyzed retrospectively for 50 consecutive patients. Residual errors in the treatment field images were determined by matching the orthogonal setup images to the vertebrae, sternum, ribs and their compromises. The most important region was the chest wall as it is crucial for the dose delivered to the heart and the ipsilateral lung. Inter-observer variation in online image matching was investigated.
The best general image matching position was the compromise of the vertebrae, ribs and sternum, while the worst position was the vertebrae alone (p ≤ 0.03). The setup margins required for the chest wall varied from 4.3 mm to 5.5 mm in the lung direction while in the superior-inferior (SI) direction the margins varied from 5.1 mm to 7.6 mm. The inter-observer variation increased the minimal margins by approximately 1 mm. The margin of the lymph node areas should be at least 4.8 mm.
Setup margins can be reduced by proper selection of a matching position for the orthogonal setup images. To retain the minimal margins sufficient, systematic error of the chest wall should not exceed 4 mm in the tangential field image.
本研究旨在寻找最佳的摆位图像匹配位置及最小摆位边界，以在乳腺癌放疗中最大程度地保护危及器官。
乳腺癌放疗是一项常规任务，但存在诸多挑战。我们研究了在全乳放疗中，将正交摆位图像与不同骨性标志匹配时的残余位置误差。
对连续50例患者的1111对正交摆位图像和切线野图像进行回顾性分析。通过将正交摆位图像与椎骨、胸骨、肋骨及其组合进行匹配，确定治疗野图像中的残余误差。最重要的区域是胸壁，因为它对于心脏和同侧肺所接受的剂量至关重要。研究了在线图像匹配中的观察者间差异。
最佳的总体图像匹配位置是椎骨、肋骨和胸骨的组合，而最差的位置是仅以椎骨为匹配（p≤0.03）。胸壁在肺方向所需的摆位边界为4.3毫米至5.5毫米，而在上下方向的边界为5.1毫米至7.6毫米。观察者间差异使最小边界增加了约1毫米。淋巴结区域的边界应至少为4.8毫米。
通过为正交摆位图像正确选择匹配位置，可以减小摆位边界。为保持足够小的边界，胸壁在切线野图像中的系统误差不应超过4毫米。
