Miyamoto Naoki, Ishikawa Masayori, Sutherland Kenneth, Suzuki Ryusuke, Matsuura Taeko, Toramatsu Chie, Takao Seishin, Nihongi Hideaki, Shimizu Shinichi, Umegaki Kikuo, Shirato Hiroki
Department of Medical Physics, Graduate School of Medicine, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
Department of Medical Physics, Graduate School of Medicine, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan
J Radiat Res. 2015 Jan;56(1):186-96. doi: 10.1093/jrr/rru069. Epub 2014 Aug 16.
In the real-time tumor-tracking radiotherapy system, a surrogate fiducial marker inserted in or near the tumor is detected by fluoroscopy to realize respiratory-gated radiotherapy. The imaging dose caused by fluoroscopy should be minimized. In this work, an image processing technique is proposed for tracing a moving marker in low-dose imaging. The proposed tracking technique is a combination of a motion-compensated recursive filter and template pattern matching. The proposed image filter can reduce motion artifacts resulting from the recursive process based on the determination of the region of interest for the next frame according to the current marker position in the fluoroscopic images. The effectiveness of the proposed technique and the expected clinical benefit were examined by phantom experimental studies with actual tumor trajectories generated from clinical patient data. It was demonstrated that the marker motion could be traced in low-dose imaging by applying the proposed algorithm with acceptable registration error and high pattern recognition score in all trajectories, although some trajectories were not able to be tracked with the conventional spatial filters or without image filters. The positional accuracy is expected to be kept within ±2 mm. The total computation time required to determine the marker position is a few milliseconds. The proposed image processing technique is applicable for imaging dose reduction.
在实时肿瘤跟踪放射治疗系统中，通过荧光透视法检测插入肿瘤内部或附近的替代基准标记，以实现呼吸门控放射治疗。应将荧光透视法产生的成像剂量降至最低。在这项工作中，提出了一种图像处理技术，用于在低剂量成像中跟踪移动的标记。所提出的跟踪技术是运动补偿递归滤波器和模板模式匹配的组合。所提出的图像滤波器可以根据荧光透视图像中当前标记的位置确定下一帧的感兴趣区域，从而减少递归过程中产生的运动伪影。通过使用从临床患者数据生成的实际肿瘤轨迹进行体模实验研究，检验了所提出技术的有效性和预期的临床益处。结果表明，应用所提出的算法，在所有轨迹中均能在低剂量成像中跟踪标记运动，且配准误差可接受，模式识别得分较高，尽管有些轨迹无法用传统的空间滤波器或不使用图像滤波器进行跟踪。预计位置精度将保持在±2毫米以内。确定标记位置所需的总计算时间为几毫秒。所提出的图像处理技术适用于降低成像剂量。
