Kilovoltage radiographs are acquired during motion-synchronized treatments on Radixact to localize the tumor during the treatment. Several previous publications have provided estimates of patient dose from these planar radiographs. However, a recent hardware update changed several aspects of the kV imaging system, including a new X-ray tube, an extended source-to-axis distance (SAD), and a larger field size. This is denoted the extended configuration. The purpose of this work was to assess the impact of the configuration change on patient dose from these procedures. Point doses in water were measured using the TG-61 protocol for tube potentials between 100 and 140 kVp for both the standard and extended configurations under the same water tank setup. Comparisons were made for equal mAs since the same protocols (kVp, mAs) will be used for both configurations. In comparison to the standard configuration, doses per mAs from the extended configuration were found to be ~66% less and falloff less steep due to the increased SAD. However, a larger volume of tissue is irradiated due to the larger field size. Beam quality for a given tube potential was the same as determined by half-value layer measurements. Both kV configurations are available from the vendor, therefore, the values in this work can be used to compare values previously published in the literature for the standard configuration or to intercompare doses from these two system configurations.

中文翻译：

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技术说明：关于 kV 成像配置对 Radixact® 运动同步治疗期间平面图像剂量的影响

在 Radixact 的运动同步治疗期间获取千伏 X 线照片，以在治疗期间定位肿瘤。之前的一些出版物提供了这些平面 X 光片对患者剂量的估计。然而，最近的硬件更新改变了 kV 成像系统的几个方面，包括新的 X 射线管、扩展的源轴距离 (SAD) 和更大的场尺寸。这表示扩展配置。这项工作的目的是评估配置更改对这些程序中患者剂量的影响。使用 TG-61 协议测量在相同水箱设置下标准和扩展配置的管电位在 100 到 140 kVp 之间的水中点剂量。由于相同的协议（kVp，mAs) 将用于两种配置。与标准配置相比，发现扩展配置的每毫安剂量减少了约 66%，并且由于 SAD 增加而下降不那么陡峭。然而，由于更大的场尺寸，更大体积的组织被照射。给定管电位的光束质量与通过半值层测量确定的相同。两种 kV 配置均可从供应商处获得，因此，这项工作中的值可用于比较先前在文献中发布的标准配置值或比较这两种系统配置的剂量。由于更大的场尺寸，更大体积的组织被照射。给定管电位的光束质量与通过半值层测量确定的相同。两种 kV 配置均可从供应商处获得，因此，这项工作中的值可用于比较先前在文献中发布的标准配置值或比较这两种系统配置的剂量。由于更大的场尺寸，更大体积的组织被照射。给定管电位的光束质量与通过半值层测量确定的相同。两种 kV 配置均可从供应商处获得，因此，这项工作中的值可用于比较先前在文献中发布的标准配置值或比较这两种系统配置的剂量。