Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA 91010, USA.
Radiother Oncol. 2012 Feb;102(2):309-14. doi: 10.1016/j.radonc.2011.07.027. Epub 2011 Aug 27.
To evaluate residual patient setup errors and daily dose variations of different less-than-daily image guidance (IG) strategies in the delivery of external beam radiotherapy for esophageal cancer.
Daily image-guided setup data for 25 consecutive esophageal cancer patients treated with helical tomotherapy were evaluated. Seven less-than-daily IG strategies with different imaging frequencies were simulated. For each IG strategy, the daily residual setup errors were calculated. Using TomoTherapy Planned Adaptive software, daily dose variations to the clinical target volume, heart, and lungs were evaluated in five representative patients.
With 0% (60%) IG frequency, the margins required for adequate coverage of the clinical target volume were 13 mm (10 mm), 14 mm (11 mm), and 5 mm (5 mm) in the left-right, superior-inferior, and anterior-posterior directions, respectively. Even with 60% IG frequency, 10% of the fractions had more than 10% decrease in the dose level covering 95% of the target, and 14% and 13% of the fractions had more than 10% increase in total lung volume receiving at least 0.8 Gy per fraction, and heart volume receiving at least 1.2 Gy per fraction, respectively.
Substantial residual setup errors would occur for treatment fractions without IG even if the most frequent less-than-daily IG strategy was to be used, which could lead to significant daily dose variations for the target volume and adjacent normal tissues. Daily image guidance is recommended throughout the course of treatment in conformal radiotherapy for esophageal cancer.
评估在食管癌外照射放疗中，不同非每日影像引导（IG）策略下的残余患者摆位误差和每日剂量变化。
评估了 25 例连续接受螺旋断层放疗的食管癌患者的每日图像引导摆位数据。模拟了七种不同成像频率的非每日 IG 策略。对于每种 IG 策略，计算了每日残余摆位误差。使用 TomoTherapy Planned Adaptive 软件，在五名代表性患者中评估了临床靶区、心脏和肺部的每日剂量变化。
在 0%（60%）IG 频率下，为充分覆盖临床靶区，左右、上下和前后方向所需的边缘分别为 13 毫米（10 毫米）、14 毫米（11 毫米）和 5 毫米（5 毫米）。即使采用 60%IG 频率，仍有 10%的分数剂量水平下降超过 10%，覆盖 95%的靶区，14%和 13%的分数肺总体积接受的剂量至少为 0.8Gy/分，心脏体积接受的剂量至少为 1.2Gy/分。
即使采用最频繁的非每日 IG 策略，对于没有 IG 的治疗分数也会出现大量残余摆位误差，这可能导致靶区和相邻正常组织的每日剂量变化显著。在食管癌适形放疗中，建议在整个治疗过程中进行每日图像引导。
