High-Resolution MLC Leaf Position Measurements With a Large Area MAPS
High-Resolution MLC Leaf Position Measurements With a Large Area MAPS
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DOI：
10.1109/trpms.2020.3007859
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发表时间：
2021-05-01
影响因子：
4.4
通讯作者：
Hugtenburg, R. P.
中科院分区：
文献类型：
--
作者：
Pritchard, J. L.;Velthuis, J. J.;Hugtenburg, R. P.
多叶准直器（MLCs）是现代放射治疗中塑造x射线治疗光束的重要组成部分。目前，MLC叶片位置精度每月验证为+/- 1毫米。然而，叶片位置精度可能在验证日期和处理验证之间漂移，仅发生预处理。为了防止严重的错误，使用实时验证系统将是非常有益的。我们正在开发一个基于单片有源像素传感器（MAPSs）的系统。map在光子和电子照射下具有很强的辐射强度，具有高读出率，低衰减，适合高分辨率应用，使其成为理想的上游辐射探测器。在这里，我们使用Lassena MAPS报告结果，该MAPS尺寸为12 x 14 cm(2)，具有三面可按钮，可以监测整个处理区域。Lassena检测器被放置在Elekta Synergy LINAC的处理场中，其MLC叶片宽度为0.5 cm。一个MLC叶片在田间伸展到十个不同的位置。采用基于sobel的方法重建叶片边缘位置。当传感器放置在85cm的高度时，处理光束时间为0.3 s，重建的叶片位置与设置的叶片位置之间的对应关系非常好，对于叶片延伸范围为1 ~ 35mm的中心叶片，分辨率在60.6 +/- 8 ~ 109 +/- 12 μ m之间。
Multileaf collimators (MLCs) are an essential component in modern radiotherapy that shape the X-ray treatment beam. Currently, MLC leaf position accuracy is verified to +/- 1 mm every month. However, leaf position accuracy can drift between verification dates and treatment verification only occurs pretreatment. To prevent serious errors, it would be highly beneficial to use a real-time verification system. We are developing a system based on monolithic active pixel sensors (MAPSs). MAPS are radiation hard under photon and electron irradiation, have high readout rates, low attenuation and are suitable for high-resolution applications making them an ideal upstream radiation detector. Here, we report results using the Lassena MAPS, which measures 12 x 14 cm(2) and is three-side buttable, allowing full treatment fields to be monitored. The Lassena detector was placed in the treatment field of an Elekta Synergy LINAC which has an MLC leaf width of 0.5 cm. An MLC leaf was extended to ten different positions within the field. Sobel-based methods were used to reconstruct the leaf edge position. Correspondence between reconstructed and set leaf position was excellent and resolutions ranged between 60.6 +/- 8 and 109 +/- 12 mu m for a central leaf with leaf extensions ranging from 1 to 35 mm using similar to 0.3 s of treatment beam time while the sensor was placed at an SSD of 85 cm.