Hospital Clínic de Barcelona, Department of Radiation Oncology, Barcelona, Spain.
Rambam Health Care Campus, Department of Radiotherapy, Division of Oncology, Haifa, Israel.
Radiother Oncol. 2023 Sep;186:109775. doi: 10.1016/j.radonc.2023.109775. Epub 2023 Jun 28.
To demonstrate the feasibility of characterising MLCs and MLC models implemented in TPSs using a common set of dynamic beams.
A set of tests containing synchronous (SG) and asynchronous sweeping gaps (aSG) was distributed among twenty-five participating centres. Doses were measured with a Farmer-type ion chamber and computed in TPSs, which provided a dosimetric characterisation of the leaf tip, tongue-and-groove, and MLC transmission of each MLC, as well as an assessment of the MLC model in each TPS. Five MLC types and four TPSs were evaluated, covering the most frequent combinations used in radiotherapy departments.
Measured differences within each MLC type were minimal, while large differences were found between MLC models implemented in clinical TPSs. This resulted in some concerning discrepancies, especially for the HD120 and Agility MLCs, for which differences between measured and calculated doses for some MLC-TPS combinations exceeded 10%. These large differences were particularly evident for small gap sizes (5 and 10 mm), as well as for larger gaps in the presence of tongue-and-groove effects. A much better agreement was found for the Millennium120 and Halcyon MLCs, differences being within ± 5% and ± 2.5%, respectively.
The feasibility of using a common set of tests to assess MLC models in TPSs was demonstrated. Measurements within MLC types were very similar, but TPS dose calculations showed large variations. Standardisation of the MLC configuration in TPSs is necessary. The proposed procedure can be readily applied in radiotherapy departments and can be a valuable tool in IMRT and credentialing audits.
用一组通用的动态射束来证明对在 TPS 中实现的多叶准直器和多叶准直器模型进行特性描述的可行性。
一组包含同步（SG）和异步扫描间隙（aSG）的测试在 25 个参与中心之间进行了分配。剂量使用 Farmer 型电离室进行测量，并在 TPS 中进行计算，这为每个多叶准直器的叶尖、凹凸槽和多叶准直器传输提供了剂量学特性描述，以及对每个 TPS 中的多叶准直器模型进行了评估。评估了五种多叶准直器类型和四种 TPS，涵盖了放射治疗部门最常用的组合。
在每种多叶准直器类型内测量到的差异很小，而在临床 TPS 中实现的多叶准直器模型之间则存在较大差异。这导致了一些令人担忧的差异，特别是对于 HD120 和 Agility 多叶准直器，对于某些 MLC-TPS 组合，测量和计算剂量之间的差异超过 10%。这些较大的差异在小间隙尺寸（5 和 10 毫米）以及存在凹凸槽效应时的较大间隙中尤为明显。对于 Millennium120 和 Halcyon 多叶准直器，发现差异在±5%和±2.5%之间，吻合得更好。
使用一组通用的测试来评估 TPS 中的多叶准直器模型的可行性得到了证明。在多叶准直器类型内的测量非常相似，但 TPS 剂量计算显示出较大的变化。在 TPS 中标准化多叶准直器配置是必要的。所提出的程序可以很容易地应用于放射治疗部门，并成为 IMRT 和认证审核的有价值的工具。
