Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark.
Acta Oncol. 2010 Oct;49(7):1177-83. doi: 10.3109/0284186X.2010.498435.
Localisation errors in cone-beam CT (CBCT) guided stereotactic body radiation therapy (SBRT) were evaluated and compared to positioning using the external coordinates of a stereotactic body frame (SBF) alone. Possible correlations to patient- or treatment-specific factors such as body mass index (BMI), planning time, treatment delivery time, and distance between tumour and spinal cord were explored to determine whether they influenced on the benefit of image-guidance.
A total of 34 patients received SBRT (3 fractions) for tumours in the liver (15 patients) or the lung (19 patients). Immobilisation and positioning was obtained with a SBF. Pre- and post-treatment CBCT scans were registered with the bony anatomy of the planning CT to find inter- and intrafractional patient positioning errors (PPE). For lung tumour patients, matching was also performed on the tumours to find the tumour positioning errors (TPE) and baseline shifts relative to bony anatomy.
The mean inter- and intrafractional 3D vector PPE was 4.5 ± 2.7 mm (average ± SD) and 1.5 ± 0.6 mm, respectively, for the combined group of patients. For lung tumours, the interfractional misalignment was 5.6 ± 1.8 mm. The baseline shift was 3.9 ± 2.0 mm. Intrafractional TPE and baseline shifts were 2.1 ± 0.7 mm and 1.9 ± 0.6 mm, respectively. The magnitude of interfractional baseline shift was closely correlated with the distance between the tumour and the spinal cord. Intrafractional errors were independent of patient BMI, age or gender.
Image-guidance reduced setup errors considerably. The study demonstrated the benefit of CBCT-guidance regardless of patient specific factors such as BMI, age or gender. Protection of the spinal cord was facilitated by the correlation between the tumour position relative to the spinal cord and the magnitude of baseline shift.
评估了锥形束 CT（CBCT）引导立体定向体部放射治疗（SBRT）中的定位误差，并与单独使用立体定向体架（SBF）的外部坐标定位进行了比较。探讨了与患者或治疗相关因素（如体重指数（BMI）、计划时间、治疗时间和肿瘤与脊髓之间的距离）的可能相关性，以确定它们是否影响图像引导的获益。
共 34 例患者因肝（15 例）或肺（19 例）肿瘤接受 SBRT（3 个分次）治疗。使用 SBF 进行固定和定位。对治疗前和治疗后的 CBCT 扫描与计划 CT 的骨性解剖结构进行配准，以找到分次内和分次间的患者定位误差（PPE）。对于肺肿瘤患者，还在肿瘤上进行匹配，以找到肿瘤定位误差（TPE）和相对于骨性解剖结构的基线偏移。
在联合患者组中，平均分次内和分次间的 3D 向量 PPE 分别为 4.5 ± 2.7mm（平均值±标准差）和 1.5 ± 0.6mm。对于肺肿瘤，分次间的不匹配为 5.6 ± 1.8mm。基线偏移为 3.9 ± 2.0mm。分次内 TPE 和基线偏移分别为 2.1 ± 0.7mm 和 1.9 ± 0.6mm。分次间基线偏移的幅度与肿瘤和脊髓之间的距离密切相关。分次内误差与患者 BMI、年龄或性别无关。
图像引导显著减少了摆位误差。该研究证明了 CBCT 引导的获益，与患者特定因素（如 BMI、年龄或性别）无关。肿瘤相对于脊髓的位置与基线偏移幅度之间的相关性促进了脊髓的保护。
