Daily imaging is mandatory for the Halcyon and Ethos, which are the new ring-shaped radiotherapy units. This study quantified the imaging dose of the cone beam computed tomography (CBCT) system of the new ring-shaped radiotherapy units using the latest International Electrotechnical Commission (IEC) measurement approach. Furthermore, we investigated the influence of collimation width on the imaging dose and compared the imaging dose values obtained using three IEC measurement approaches. The IEC has proposed three approaches for measuring CTDI: traditional, transition, and the latest measurement approach. In addition to the dose measured on the CTDI phantom, the latest IEC approach uses correction factors measured in free air for CTDI measurement. The imaging dose was measured for all scanning protocols using the latest IEC approach. To investigate the influence of the collimation width on the imaging dose, the associated dose metric values were evaluated and compared using different IEC approaches to increase the collimation width (2–28 cm). Furthermore, the imaging system output stability was evaluated by repeated measurements. In the repeated measurements, the standard deviation of CTDI value for the pelvis and head protocol was 0.05 mGy and 0.01 mGy, respectively. And the coefficient of variation was 0.21% and 0.23%, respectively. The measured CTDI values of the clinical protocols were higher than the vendor-provided value, except for the pelvis protocol. The value of CTDI changes little with increasing collimation width using the latest IEC approach. The traditional and transition approaches either underestimated or overestimated the value of CTDI, as measured by the latest IEC approach, with increasing collimation width. The new ring-shaped radiotherapy units imaging system has good output stability. The CTDIw values measured for clinical scanning protocols generally exceeded the vendor-provided values. Compared with the latest IEC CTDI measurement approach, the traditional and transition measurement approaches were more influenced by beam width. For wide CBCT scans, rationalizing the choice of imaging dose measurement approach is important.

中文翻译：

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使用不同的国际电工委员会方法评估环形放射治疗单元的锥形束计算机断层扫描系统的成像剂量


Halcyon 和 Ethos 是新型环形放射治疗装置，每日成像是强制性的。本研究使用最新的国际电工委员会（IEC）测量方法量化了新型环形放射治疗装置的锥形束计算机断层扫描（CBCT）系统的成像剂量。此外，我们研究了准直宽度对成像剂量的影响，并比较了使用三种 IEC 测量方法获得的成像剂量值。 IEC 提出了三种测量 CTDI 的方法：传统的、过渡的和最新的测量方法。除了在 CTDI 体模上测量的剂量外，最新的 IEC 方法还使用在自由空气中测量的校正因子来进行 CTDI 测量。使用最新的 IEC 方法测量所有扫描协议的成像剂量。为了研究准直宽度对成像剂量的影响，使用不同的 IEC 方法来增加准直宽度 (2-28 cm) 来评估和比较相关的剂量度量值。此外，通过重复测量来评估成像系统输出稳定性。在重复测量中，骨盆和头部协议的 CTDI 值的标准偏差分别为 0.05 mGy 和 0.01 mGy。变异系数分别为0.21%和0.23%。除骨盆协议外，临床协议的测量 CTDI 值高于供应商提供的值。使用最新的 IEC 方法，随着准直宽度的增加，CTDI 的值几乎没有变化。随着准直宽度的增加，传统方法和过渡方法要么低估或高估了通过最新 IEC 方法测量的 CTDI 值。 新型环形放疗台成像系统具有良好的输出稳定性。针对临床扫描协议测量的 CTDIw 值通常超过供应商提供的值。与最新的IEC CTDI测量方法相比，传统和过渡测量方法受波束宽度的影响更大。对于宽 CBCT 扫描，合理选择成像剂量测量方法非常重要。