Medical Physics Department, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.
Med Phys. 2012 Jan;39(1):160-7. doi: 10.1118/1.3668061.
Treatment plans for the TomoTherapy unit are produced with a planning system that is integral to the unit. The authors have produced an independent dose calculation system, to enable plans to be recalculated in three dimensions, using the patient's CT data.
Software has been written using MATLAB. The DICOM-RT plan object is used to determine the treatment parameters used, including the treatment sinogram. Each projection of the sinogram is segmented and used to calculate dose at multiple calculation points in a three-dimensional grid using tables of measured beam data. A fast ray-trace algorithm is used to determine effective depth for each projection angle at each calculation point. Calculations were performed on a standard desktop personal computer, with a 2.6 GHz Pentium, running Windows XP.
The time to perform a calculation, for 3375 points averaged 1 min 23 s for prostate plans and 3 min 40 s for head and neck plans. The mean dose within the 50% isodose was calculated and compared with the predictions of the TomoTherapy planning system. When the modified CT (which includes the TomoTherapy couch) was used, the mean difference for ten prostate patients, was -0.4% (range -0.9% to +0.3%). With the original CT (which included the CT couch), the mean difference was -1.0% (range -1.7% to 0.0%). The number of points agreeing with a gamma 3%∕3 mm averaged 99.2% with the modified CT, 96.3% with the original CT. For ten head and neck patients, for the modified and original CT, respectively, the mean difference was +1.1% (range -0.4% to +3.1%) and 1.1% (range -0.4% to +3.0%) with 94.4% and 95.4% passing a gamma 4%∕4 mm. The ability of the program to detect a variety of simulated errors has been tested.
By using the patient's CT data, the independent dose calculation performs checks that are not performed by a measurement in a cylindrical phantom. This enables it to be used either as an additional check or to replace phantom measurements for some patients. The software has potential to be used in any application where one wishes to model changes to patient conditions.
TomoTherapy 设备的治疗计划是使用与设备集成的规划系统生成的。作者开发了一种独立的剂量计算系统，能够使用患者的 CT 数据在三维空间重新计算计划。
使用 MATLAB 编写了软件。DICOM-RT 计划对象用于确定使用的治疗参数，包括治疗射束图。射束图的每个投影都被分割，并使用测量光束数据的表在三维网格中的多个计算点计算剂量。使用快速光线追踪算法确定每个计算点的每个投影角度的有效深度。在配备 2.6GHz 奔腾处理器、运行 Windows XP 的标准台式个人计算机上进行了计算。
对于 3375 个点的计算，前列腺计划的平均计算时间为 1 分 23 秒，头颈部计划的平均计算时间为 3 分 40 秒。计算并比较了 50%等剂量线内的平均剂量与 TomoTherapy 计划系统的预测值。当使用包括 TomoTherapy 治疗床的修正 CT 时，十个前列腺患者的平均差值为-0.4%（范围为-0.9%至+0.3%）。当使用包括 CT 治疗床的原始 CT 时，平均差值为-1.0%（范围为-1.7%至 0.0%）。使用修正 CT 时，与伽玛 3%∕3mm 一致的点的平均值为 99.2%，使用原始 CT 时为 96.3%。对于十个头颈部患者，修正 CT 和原始 CT 的平均差值分别为+1.1%（范围为-0.4%至+3.1%）和+1.1%（范围为-0.4%至+3.0%），伽玛 4%∕4mm 通过率分别为 94.4%和 95.4%。该程序已测试了检测各种模拟误差的能力。
通过使用患者的 CT 数据，独立的剂量计算执行了在圆柱形体模中不执行的检查。这使其可以用作附加检查，或者替代某些患者的体模测量。该软件有可能用于希望对患者情况进行建模更改的任何应用。
