PurposeTo enable a real‐time applicator guidance for brachytherapy, we used for the first time infra‐red tracking cameras (OptiTrack, USA) integrated into a mobile cone‐beam computed tomography (CBCT) scanner (medPhoton, Austria). We provide the first description of this prototype and its performance evaluation.MethodsWe performed assessments of camera calibration and camera‐CBCT registration using a geometric calibration phantom. For this purpose, we first evaluated the effects of intrinsic parameters such as camera temperature or gantry rotations on the tracked marker positions. Afterward, calibrations with various settings (sample number, field of view coverage, calibration directions, calibration distances, and lighting conditions) were performed to identify the requirements for achieving maximum tracking accuracy based on an in‐house phantom. The corresponding effects on camera‐CBCT registration were determined as well by comparing tracked marker positions to the positions determined via CBCT. Long‐term stability was assessed by comparing tracking and a ground‐truth on a weekly basis for 6 weeks.ResultsRobust tracking with positional drifts of 0.02 ± 0.01 mm was feasible using the system after a warm‐up period of 90 min. However, gantry rotations affected the tracking and led to inaccuracies of up to 0.70 mm. We identified that 4000 samples and full coverage were required to ensure a robust determination of marker positions and camera‐CBCT registration with geometric deviations of 0.18 ± 0.03 mm and 0.42 ± 0.07 mm, respectively. Long‐term stability showed deviations of more than two standard deviations from the initial calibration after 3 weeks.ConclusionWe implemented for the first time a standalone combined camera‐CBCT system for tracking in brachytherapy. The system showed high potential for establishing corresponding workflows.

中文翻译：

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首次实施集成到移动 CBCT 扫描仪中的创新红外摄像头系统，用于近距离放射治疗中的施源器跟踪 — 初始性能表征

目的为了实现近距离放射治疗的实时施药器引导，我们首次使用集成到移动锥形束计算机断层扫描 (CBCT) 扫描仪（奥地利 medPhoton）中的红外跟踪摄像机（OptiTrack，美国）。我们提供了该原型的首次描述及其性能评估。方法我们使用几何校准模型对相机校准和相机 CBCT 配准进行了评估。为此，我们首先评估了相机温度或机架旋转等内部参数对跟踪标记位置的影响。随后，进行了各种设置（样本数量、视场覆盖范围、校准方向、校准距离和照明条件）的校准，以确定基于内部模型实现最大跟踪精度的要求。通过将跟踪标记位置与通过 CBCT 确定的位置进行比较，也确定了对相机 CBCT 配准的相应影响。通过在 6 周内每周比较跟踪和地面实况来评估长期稳定性。结果在 90 分钟的预热期后，使用该系统可以实现位置漂移为 0.02 ± 0.01 毫米的鲁棒跟踪。然而，龙门旋转会影响跟踪并导致高达 0.70 毫米的误差。我们发现需要 4000 个样本和完全覆盖才能确保可靠地确定标记位置和相机-CBCT 配准，几何偏差分别为 0.18 ± 0.03 mm 和 0.42 ± 0.07 mm。长期稳定性显示，3 周后与初始校准的偏差超过两个标准差。结论我们首次实现了用于近距离放射治疗跟踪的独立组合相机-CBCT 系统。该系统显示出建立相应工作流程的巨大潜力。