Department of Radiation Oncology, The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
Int J Radiat Oncol Biol Phys. 2011 Apr 1;79(5):1557-64. doi: 10.1016/j.ijrobp.2010.07.032. Epub 2010 Oct 8.
The purpose of the present study was to quantify the robustness of the dose distributions from three whole-breast radiotherapy (RT) techniques involving different levels of intensity modulation against whole patient setup inaccuracies and breast shape changes.
For 19 patients (one computed tomography scan and five cone beam computed tomography scans each), three treatment plans were made (wedge, simple intensity-modulated RT [IMRT], and full IMRT). For each treatment plan, four dose distributions were calculated. The first dose distribution was the original plan. The other three included the effects of patient setup errors (rigid displacement of the bony anatomy) or breast errors (e.g., rotations and shape changes of the breast with respect to the bony anatomy), or both, and were obtained through deformable image registration and dose accumulation. Subsequently, the effects of the plan type and error sources on target volume coverage, mean lung dose, and excess dose were determined.
Systematic errors of 1-2 mm and random errors of 2-3 mm (standard deviation) were observed for both patient- and breast-related errors. Planning techniques involving glancing fields (wedge and simple IMRT) were primarily affected by patient errors (∼6% loss of coverage near the dorsal field edge and ∼2% near the skin). In contrast, plan deterioration due to breast errors was primarily observed in planning techniques without glancing fields (full IMRT, ∼2% loss of coverage near the dorsal field edge and ∼4% near the skin).
The influences of patient and breast errors on the dose distributions are comparable in magnitude for whole breast RT plans, including glancing open fields, rendering simple IMRT the preferred technique. Dose distributions from planning techniques without glancing open fields were more seriously affected by shape changes of the breast, demanding specific attention in partial breast planning techniques.
本研究的目的是量化三种全乳放射治疗（RT）技术的剂量分布对全患者摆位误差和乳房形状变化的稳健性，这些技术涉及不同程度的强度调制。
对 19 名患者（每个患者均有一个计算机断层扫描和 5 个锥形束 CT 扫描），制作了 3 种治疗计划（楔形，简单强度调制 RT [IMRT] 和完全 IMRT）。对于每个治疗计划，计算了 4 种剂量分布。第一种剂量分布是原始计划。另外三种包括患者摆位误差（骨骼解剖结构的刚性位移）或乳房误差（例如，乳房相对于骨骼解剖结构的旋转和形状变化）的影响，或者两者都通过变形图像配准和剂量积累获得。随后，确定了计划类型和误差源对靶区覆盖、平均肺剂量和过量剂量的影响。
对于患者和乳房相关的误差，观察到 1-2 毫米的系统误差和 2-3 毫米（标准差）的随机误差。涉及斜射野的规划技术（楔形和简单 IMRT）主要受患者误差的影响（近背部场边缘约 6％的覆盖损失和近皮肤约 2％）。相比之下，在没有斜射野的规划技术中（完全 IMRT），主要观察到由于乳房误差导致的计划恶化，在近背部场边缘约 2％和近皮肤约 4％的覆盖损失。
在包括斜射开放野的全乳 RT 计划中，患者和乳房误差对剂量分布的影响具有可比性，使得简单 IMRT 成为首选技术。没有斜射开放野的规划技术的剂量分布受乳房形状变化的影响更为严重，在部分乳房规划技术中需要特别注意。
