Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA 19104, USA.
Int J Radiat Oncol Biol Phys. 2010 Mar 15;76(4):1092-9. doi: 10.1016/j.ijrobp.2009.03.036. Epub 2009 Jul 20.
To evaluate dosimetric consequences of daily isocenter correction during prostate cancer radiation therapy using the Calypso 4D localization system.
Data were analyzed from 28 patients with electromagnetic transponders implanted in their prostates for daily target localization and tracking. Treatment planning isocenters were recorded based on the values of the vertical, longitudinal, and lateral axes. Isocenter location obtained via alignment with skin tattoos was compared with that obtained via the electromagnetic localization system. Daily isocenter shifts, based on the isocenter location differences between the two alignment methods in each spatial axis, were calculated for each patient over their entire course. The mean isocenter shifts were used to determine dosimetric consequences of treatment based on skin tattoo alignments alone.
The mean SD of the percentages of treatment days with shifts beyond 0.5 cm for vertical, longitudinal and lateral shifts were 62% 28%, 35% 26%, and 38% 21%, respectively. If daily electromagnetic localization was not used, the excess in prescribed dose delivered to 70% of the rectum was 10 Gy and the deficit in prescribed dose delivered to 95% of the planning target volume was 10 Gy. The mean isocenter shift was not associated with the volumes of the prostate, rectum, or bladder, or with patient body mass index.
Daily isocenter localization can reduce the treatment dose to the rectum. Correcting for this variability could lead to improved dose delivery, reduced side effects, and potentially improved treatment outcomes.
使用 Calypso 4D 定位系统评估前列腺癌放射治疗中每天的等中心校正的剂量学后果。
对 28 例在前列腺中植入电磁转发器以进行每日靶区定位和跟踪的患者进行数据分析。基于垂直、纵向和横向轴的数值记录治疗计划等中心。通过与皮肤纹身对齐获得的等中心位置与通过电磁定位系统获得的等中心位置进行比较。在每个空间轴上，根据两种对齐方法之间的等中心位置差异，计算每个患者在整个治疗过程中的每日等中心偏移量。平均等中心偏移量用于根据皮肤纹身对齐确定单独进行治疗的剂量学后果。
垂直、纵向和横向偏移超过 0.5cm 的治疗天数百分比的平均值标准差分别为 62%28%、35%26%和 38%21%。如果不每天使用电磁定位，那么 70%的直肠接受的规定剂量会增加 10Gy，而 95%的计划靶区体积接受的规定剂量会减少 10Gy。平均等中心偏移量与前列腺、直肠或膀胱的体积或患者的体重指数无关。
每天的等中心定位可以降低直肠的治疗剂量。纠正这种变化可能会导致更好的剂量传递、减少副作用，并可能改善治疗结果。
