Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, UK.
Phys Med Biol. 2011 Apr 21;56(8):2445-57. doi: 10.1088/0031-9155/56/8/008. Epub 2011 Mar 22.
A phantom was designed and implemented for the delivery of treatment plans to cells in vitro. Single beam, 3D-conformal radiotherapy (3D-CRT) plans, inverse planned five-field intensity-modulated radiation therapy (IMRT), nine-field IMRT, single-arc volumetric modulated arc therapy (VMAT) and dual-arc VMAT plans were created on a CT scan of the phantom to deliver 3 Gy to the cell layer and verified using a Farmer chamber, 2D ionization chamber array and gafchromic film. Each plan was delivered to a 2D ionization chamber array to assess the temporal characteristics of the plan including delivery time and 'cell's eye view' for the central ionization chamber. The effective fraction time, defined as the percentage of the fraction time where any dose is delivered to each point examined, was also assessed across 120 ionization chambers. Each plan was delivered to human prostate cancer DU-145 cells and normal primary AGO-1522b fibroblast cells. Uniform beams were delivered to each cell line with the delivery time varying from 0.5 to 20.54 min. Effective fraction time was found to increase with a decreasing number of beams or arcs. For a uniform beam delivery, AGO-1552b cells exhibited a statistically significant trend towards increased survival with increased delivery time. This trend was not repeated when the different modulated clinical delivery methods were used. Less sensitive DU-145 cells did not exhibit a significant trend towards increased survival with increased delivery time for either the uniform or clinical deliveries. These results confirm that dose rate effects are most prevalent in more radiosensitive cells. Cell survival data generated from uniform beam deliveries over a range of dose rates and delivery times may not always be accurate in predicting response to more complex delivery techniques, such as IMRT and VMAT.
设计并实现了一个用于向体外细胞递送治疗计划的体模。在体模的 CT 扫描图像上，创建了单束、3D 适形放疗（3D-CRT）计划、逆向设计的五野强度调制放疗（IMRT）计划、九野 IMRT 计划、单弧容积旋转调强放疗（VMAT）计划和双弧 VMAT 计划，以将 3 Gy 剂量递送至细胞层，并使用 Farmer 室、二维电离室阵列和 Gafchromic 胶片进行验证。每个计划都被递送到二维电离室阵列上，以评估计划的时间特性，包括递送时间和中央电离室的“细胞视野”。还评估了 120 个电离室的有效分数时间，定义为每个检查点接收到任何剂量的分数时间的百分比。每个计划都被递送到人前列腺癌 DU-145 细胞和正常原代 AGO-1522b 成纤维细胞。均匀束被递送到每个细胞系，递送时间从 0.5 到 20.54 分钟不等。随着射束或弧数的减少，有效分数时间增加。对于均匀束递送，AGO-1552b 细胞表现出随着递送时间增加而存活增加的统计学显著趋势。当使用不同的调制临床递送方法时，这种趋势并未重复。对于均匀或临床递送，不那么敏感的 DU-145 细胞没有表现出随着递送时间增加而存活增加的显著趋势。这些结果证实，剂量率效应在更敏感的细胞中最为普遍。在一系列剂量率和递送时间下从均匀束递送产生的细胞存活数据可能并不总是准确地预测对更复杂的递送技术（如 IMRT 和 VMAT）的反应。
