Kyoto University.
J Appl Clin Med Phys. 2013 Sep 6;14(5):255-64. doi: 10.1120/jacmp.v14i5.4488.
The Vero4DRT (MHI-TM2000) is capable of performing X-ray image-based tracking (X-ray Tracking) that directly tracks the target or fiducial markers under continuous kV X-ray imaging. Previously, we have shown that irregular respiratory patterns increased X-ray Tracking errors. Thus, we assumed that audio instruction, which generally improves the periodicity of respiration, should reduce tracking errors. The purpose of this study was to assess the effect of audio instruction on X-ray Tracking errors. Anterior-posterior abdominal skin-surface displacements obtained from ten lung cancer patients under free breathing and simple audio instruction were used as an alternative to tumor motion in the superior-inferior direction. First, a sequential predictive model based on the Levinson-Durbin algorithm was created to estimate the future three-dimensional (3D) target position under continuous kV X-ray imaging while moving a steel ball target of 9.5 mm in diameter. After creating the predictive model, the future 3D target position was sequentially calculated from the current and past 3D target positions based on the predictive model every 70 ms under continuous kV X-ray imaging. Simultaneously, the system controller of the Vero4DRT calculated the corresponding pan and tilt rotational angles of the gimbaled X-ray head, which then adjusted its orientation to the target. The calculated and current rotational angles of the gimbaled X-ray head were recorded every 5 ms. The target position measured by the laser displacement gauge was synchronously recorded every 10 msec. Total tracking system errors (ET) were compared between free breathing and audio instruction. Audio instruction significantly improved breathing regularity (p < 0.01). The mean ± standard deviation of the 95th percentile of ET (E95T ) was 1.7 ± 0.5 mm (range: 1.1-2.6mm) under free breathing (E95T,FB) and 1.9 ± 0.5 mm (range: 1.2-2.7 mm) under audio instruction (E95T,AI). E95T,AI was larger than E95T,FB for five patients; no significant difference was found between E95T,FB and E95T,AI (p = 0.21). Correlation analysis revealed that the rapid respiratory velocity significantly increased E95T. Although audio instruction improved breathing regularity, it also increased the respiratory velocity, which did not necessarily reduce tracking errors.
Vero4DRT（MHI-TM2000）能够进行基于 X 射线图像的跟踪（X 射线跟踪），可在连续千伏 X 射线成像下直接跟踪目标或基准标记物。在此之前，我们已经表明不规则的呼吸模式会增加 X 射线跟踪误差。因此，我们假设通常会改善呼吸周期性的音频指令应该会减少跟踪误差。本研究的目的是评估音频指令对 X 射线跟踪误差的影响。从 10 名肺癌患者在自由呼吸和简单音频指令下获得的前后腹部皮肤表面位移被用作上/下方向肿瘤运动的替代物。首先，基于 Levinson-Durbin 算法创建了一个顺序预测模型，用于在连续千伏 X 射线成像下估计直径为 9.5 毫米的钢球目标移动时的未来三维（3D）目标位置。创建预测模型后，根据预测模型，每隔 70 毫秒，从当前和过去的 3D 目标位置连续计算未来的 3D 目标位置。同时，Vero4DRT 的系统控制器计算了万向架 X 射线头的相应俯仰旋转角度，然后将其定向到目标。每隔 5 毫秒记录计算出的和当前的万向架 X 射线头的旋转角度。激光位移计测量的目标位置每隔 10 毫秒同步记录。比较了自由呼吸和音频指令下的总跟踪系统误差（ET）。音频指令显著改善了呼吸规律性（p < 0.01）。在自由呼吸下（E95T,FB），ET 的第 95 百分位（E95T）的平均值±标准偏差为 1.7 ± 0.5mm（范围：1.1-2.6mm），在音频指令下（E95T,AI）为 1.9 ± 0.5mm（范围：1.2-2.7mm）。E95T,AI 对于五名患者大于 E95T,FB；E95T,FB 和 E95T,AI 之间无显著差异（p = 0.21）。相关分析表明，快速呼吸速度显著增加了 E95T。虽然音频指令改善了呼吸规律性，但它也增加了呼吸速度，这并不一定能减少跟踪误差。
