Department of Radiation Oncology, Dana-Farber/Brigham & Women's Cancer Center, Boston, Massachusetts 02115, USA.
Med Phys. 2007 Jul;34(7):2704-7. doi: 10.1118/1.2747050.
There is increasing evidence that, for some patients, image-guided intensity-modulated radiation therapy (IMRT) for head-and-neck cancer patients may maintain target dose coverage and critical organ (e.g., parotids) dose closer to the planned doses than setup using lasers alone. We investigated inter- and intraobserver uncertainties in patient setup in head-and-neck cancer patients. Twenty-two sets of orthogonal digital portal images (from five patients) were selected from images used for daily localization of head-and-neck patients treated with IMRT. To evaluate interobserver variations, five radiation therapists compared the portal images with the plan digitally reconstructed radiographs and reported shifts for the isocenter (approximately C2) and for a supraclavicular reference point. One therapist repeated the procedure a month later to evaluate intraobserver variations. The procedure was then repeated with teams of two therapists. The frequencies for which agreement between the shift reported by the observer and the daily mean shift (average of all observers for a given image set) were less than 1.5 and 2.5 mm were calculated. Standard errors of measurement for the intra- and interobserver uncertainty (SEMintra and SEMinter) for the individual and teams were calculated. The data showed that there was very little difference between individual therapists and teams. At isocenter, 80%-90% of all reported shifts agreed with the daily average within 1.5 mm, showing consistency in the ways both individuals and teams interpret the images (SEMinter approximately 1 mm). This dropped to 65% for the supraclavicular point (SEMinter approximately 1.5 mm). Uncertainties increased for larger setup errors. In conclusion, image-guided patient positioning allows head-and-neck patients to be controlled within 3-4 mm. This is similar to the setup uncertainties found for most head-and-neck patients, but may provide some improvement for the subset of patients with larger setup uncertainties.
越来越多的证据表明，对于某些患者，头颈部癌症患者的图像引导强度调制放射治疗（IMRT）可能比单独使用激光进行设置更能保持目标剂量覆盖和关键器官（例如腮腺）剂量接近计划剂量。我们研究了头颈部癌症患者中患者设置的组内和组间不确定性。从接受 IMRT 治疗的头颈部患者的日常定位中选择了 22 组正交数字端口图像（来自 5 名患者）。为了评估观察者间的变化，5 名放射治疗师将门户图像与计划数字重建射线照片进行比较，并报告等中心点（大约 C2）和锁骨上参考点的移位。一名治疗师在一个月后重复该程序以评估观察者内的变化。然后，两名治疗师的团队重复了该过程。计算出观察者报告的移位与每日平均移位（给定图像集的所有观察者的平均值）之间的差异小于 1.5 和 2.5 毫米的频率。计算了个体和团队的内和观察者间不确定性（SEMintra 和 SEMinter）的测量标准误差。数据表明，个体治疗师和团队之间几乎没有差异。在等中心点，80%-90%的所有报告的移位与每日平均值相差 1.5 毫米以内，表明个体和团队解释图像的方式具有一致性（SEMinter 约为 1 毫米）。对于锁骨上点，这一比例降至 65%（SEMinter 约为 1.5 毫米）。较大的设置误差会增加不确定性。总之，图像引导的患者定位可以将头颈部患者的控制在 3-4 毫米以内。这与大多数头颈部患者的设置不确定性相似，但对于设置不确定性较大的患者亚组，可能会有所改善。
