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首页> 外文期刊>International Journal of Radiation Oncology, Biology, Physics >A method to estimate mean position, motion magnitude, motion correlation, and trajectory of a tumor from cone-beam CT projections for image-guided radiotherapy.
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A method to estimate mean position, motion magnitude, motion correlation, and trajectory of a tumor from cone-beam CT projections for image-guided radiotherapy.

机译：一种从锥形束CT投影估计图像的放射疗法的平均位置，运动幅度，运动相关性和肿瘤轨迹的方法。

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摘要

PURPOSE: To develop a probability-based method for estimating the mean position, motion magnitude, and trajectory of a tumor using cone-beam CT (CBCT) projections. METHOD AND MATERIALS: CBCT acquisition was simulated for more than 80 hours of patient-measured trajectories for thoracic/abdominal tumors and prostate. The trajectories were divided into 60-second segments for which CBCT was simulated by projecting the tumor position onto a rotating imager. Tumor (surrogate) visibility on all projections was assumed. The mean and standard deviation of the tumor position and motion correlation along the three axes were determined with maximum likelihood estimation based on the projection data, assuming a Gaussian spatial distribution. The unknown position component along the imager axis was approximated by its expectation value, determined by the Gaussian distribution. Transformation of the resulting three-dimensional position to patient coordinates provided the estimated trajectory. Two trajectories were experimentally investigated by CBCT acquisition of a phantom. RESULTS: The root-mean-square error of the estimated mean position was 0.05 mm. The root-mean-square error of the trajectories was <1 mm in 99.1% of the thorax/abdomen cases and in 99.7% of the prostate cases. The experimental trajectory estimation agreed with the actual phantom trajectory within 0.44 mm in any direction. Clinical applicability was demonstrated by estimating the tumor trajectory for a pancreas cancer case. CONCLUSIONS: A method for estimation of mean position, motion magnitude, and trajectory of a tumor from CBCT projections has been developed. The accuracy was typically much better than 1 mm. The method is applicable to motion-inclusive, respiratory-gated, and tumor-tracking radiotherapy.
机译：目的：开发一种基于概率的方法，使用锥束CT（CBCT）投影来估计肿瘤的平均位置，运动幅度和轨迹。方法和材料：模拟了CBCT采集过程，测量了超过80小时的患者测量的胸/腹肿瘤和前列腺的运动轨迹。通过将肿瘤位置投影到旋转成像仪上，将轨迹分为60秒的片段，为此进行了CBCT模拟。假定所有投影的肿瘤（替代）可见度。假定高斯空间分布，基于投影数据以最大似然估计确定沿三个轴的肿瘤位置和运动相关性的均值和标准差。沿成像器轴的未知位置分量由其期望值近似，该期望值由高斯分布确定。将产生的三维位置转换为患者坐标可提供估计的轨迹。通过CBCT幻像的获取，对两条轨迹进行了实验研究。结果：估计平均位置的均方根误差为0.05 mm。在99.1％的胸部/腹部病例和99.7％的前列腺病例中，轨迹的均方根误差<1 mm。实验轨迹估计与在任何方向上0.44 mm以内的实际幻像轨迹一致。通过估计胰腺癌病例的肿瘤轨迹证明了临床适用性。结论：已开发了一种从CBCT投影中估算肿瘤的平均位置，运动幅度和轨迹的方法。精度通常比1毫米好得多。该方法适用于包容性运动，呼吸门控和肿瘤跟踪放疗。

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