Department of Therapeutic Radiology - Radiation Oncology, University of Minnesota Medical School, 420 Delaware Street SE, Mayo Mail Code 494, 55455, Minneapolis, MN, USA.
Strahlenther Onkol. 2012 Apr;188(4):346-52. doi: 10.1007/s00066-011-0066-z. Epub 2012 Mar 9.
Reduction of interfraction setup uncertainty is vital for assuring the accuracy of conformal radiotherapy. We report a systematic study of setup error to assess patients' three-dimensional (3D) localization at various treatment sites.
Tomotherapy megavoltage CT (MVCT) images were scanned daily in 259 patients from 2005-2008. We analyzed 6,465 MVCT images to measure setup error for head and neck (H&N), chest/thorax, abdomen, prostate, legs, and total marrow irradiation (TMI). Statistical comparisons of the absolute displacements across sites and time were performed in rotation (R), lateral (x), craniocaudal (y), and vertical (z) directions.
The global systematic errors were measured to be less than 3 mm in each direction with increasing order of errors for different sites: H&N, prostate, chest, pelvis, spine, legs, and TMI. The differences in displacements in the x, y, and z directions, and 3D average displacement between treatment sites were significant (p < 0.01). Overall improvement in patient localization with time (after 3-4 treatment fractions) was observed. Large displacement (> 5 mm) was observed in the 75(th) percentile of the patient groups for chest, pelvis, legs, and spine in the x and y direction in the second week of the treatment.
MVCT imaging is essential for determining 3D setup error and to reduce uncertainty in localization at all anatomical locations. Setup error evaluation should be performed daily for all treatment regions, preferably for all treatment fractions.
减少分次间摆位不确定性对于确保适形放疗的准确性至关重要。我们报告了一项系统的摆位误差研究，以评估不同治疗部位的患者三维（3D）定位。
2005-2008 年期间，我们对 259 例患者进行了每日 Tomotherapy 兆伏 CT（MVCT）扫描。我们分析了 6465 张 MVCT 图像，以测量头颈部（H&N）、胸部/胸廓、腹部、前列腺、腿部和全骨髓照射（TMI）的摆位误差。在旋转（R）、侧向（x）、颅尾（y）和垂直（z）方向上对各部位和时间的绝对位移进行了统计学比较。
在每个方向上，系统误差均小于 3mm，且不同部位的误差呈递增趋势：H&N、前列腺、胸部、骨盆、脊柱、腿部和 TMI。x、y 和 z 方向的位移差异以及治疗部位之间的 3D 平均位移均具有统计学意义（p < 0.01）。随着时间的推移（治疗 3-4 个疗程后），患者定位得到了整体改善。在治疗的第二周，在 x 和 y 方向上，胸部、骨盆、腿部和脊柱的患者群体中有 75%的患者存在大于 5mm 的大位移。
MVCT 成像对于确定 3D 摆位误差和降低所有解剖部位定位的不确定性至关重要。应每天对所有治疗区域进行摆位误差评估，最好对所有治疗分数都进行评估。
