F Nascimento Luana, Verellen Dirk, Goossens Jo, Struelens Lara, Vanhavere Filip, Leblans Paul, Akselrod Mark
Belgian Nuclear Research Centre, Mol, Belgium.
Iridium Kankernetwerk, University of Antwerp, Antwerp, Belgium.
Phys Imaging Radiat Oncol. 2020 Oct 5;16:26-32. doi: 10.1016/j.phro.2020.09.008. eCollection 2020 Oct.
There is a continual need for more accurate and effective dosimetric systems for quality assurance (QA) as radiotherapy evolves in complexity. The purpose of this project was to introduce a new system that minimally perturbs the main beam, while assessing its real time 2D dose-rate and field shapes. The system combined reusability, linear dose-rate response, and high spatial and time resolution in a single radiation detection technology that can be applied to surface dose estimation and QA.
We developed a 2D prototype system consisting of a camera, focusing lenses and short pass filter, placed on the head of a linear accelerator, facing an AlO:C,Mg radioluminescent film. To check the appropriateness of multi-leaf collimator, stability/reproducibility QA tests were prepared using the treatment planning system: including the routinely used alternating leaves, chair and pyramid checks.
The AlO:C,Mg film did not perturb the dose vs depth dose curves determined with a point detector (-0.5% difference). Our results showed a dose-rate linear film response (R = 0.999), from 5 to 600 MU/min. Measured output factors agreed with reference data within ~1%, indicating a potential for small field dosimetry. Both chair and pyramid measured profiles were comparable with those obtained with the treatment planning system within 1%. The alternating leaves test showed an average discrepancy in the valleys of 14%.
The prototype demonstrated promising results. It obviated the need for corrections regarding the relative position of the camera, confirming accurate dose-rate delivery and detection of radiation fields.
随着放射治疗的复杂性不断增加，持续需要更准确有效的剂量测定系统用于质量保证（QA）。本项目的目的是引入一种新系统，该系统对主射束的干扰最小，同时评估其实时二维剂量率和射野形状。该系统在单一辐射检测技术中结合了可重复使用性、线性剂量率响应以及高空间和时间分辨率，可应用于表面剂量估计和质量保证。
我们开发了一个二维原型系统，该系统由一台相机、聚焦透镜和短通滤光片组成，放置在线性加速器的头部，朝向AlO:C,Mg放射性发光薄膜。为检查多叶准直器的适用性，使用治疗计划系统准备了稳定性/可重复性QA测试：包括常规使用的交替叶片、椅子和金字塔检查。
AlO:C,Mg薄膜对用点探测器确定的剂量与深度剂量曲线没有干扰（差异为-0.5%）。我们的结果显示剂量率线性薄膜响应（R = 0.999），范围为5至600 MU/分钟。测量的输出因子与参考数据在约1%以内相符，表明在小射野剂量测定方面具有潜力。椅子和金字塔测量的轮廓与用治疗计划系统获得的轮廓在1%以内具有可比性。交替叶片测试显示谷值处的平均差异为14%。
该原型展示了有前景的结果。它无需对相机的相对位置进行校正，证实了准确的剂量率传递和辐射野的检测。
