Computing proton dose to irregularly moving targets.
Computing proton dose to irregularly moving targets.
复制标题
计算不规则移动目标的质子剂量。
DOI：
10.1088/0031-9155/59/15/4261
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发表时间：
2014
影响因子：
3.5
通讯作者：
Sharp,GregoryC
中科院分区：
文献类型：
--
作者：
Phillips,Justin;Gueorguiev,Gueorgui;Shackleford,JamesA;Grassberger,Clemens;Dowdell,Stephen;Paganetti,Harald;Sharp,GregoryC
目的：虽然四维计算机断层扫描（4DCT）和可变形配准可用于评估输送到规则移动目标的剂量，但很少有方法可用于不规则移动目标。4DCT捕获理想化的波形，但治疗期间的人类呼吸的特征在于逐渐的基线偏移和与周期性信号的其他偏差。本文介绍了一种基于传输时采集的1D或3D波形计算不规则运动靶区剂量的方法。方法：该方法使用CT或4DCT图像进行剂量计算，并使用传输时靶区位置的1D或3D呼吸波形。将剂量体积从其笛卡尔几何形状转换为射束特定的放射学深度空间，通过射束孔径在2D中参数化，并通过放射学深度纵向参数化。在这个新的参考系中，质子剂量根据在1D或3D轨迹中发现的运动进行平移。对这些转换的剂量体积进行加权和求和，然后转换回笛卡尔空间，产生包括测量的呼吸运动的影响的剂量估计。使用合成肺体模和单个代表性患者CT对该方法进行了验证。模拟4DCT生成的体模与2 cm的peak-to-peak motion.Results：一个被动散射质子治疗计划生成使用6 mm和5 mm涂抹体模和患者计划，分别。该方法在没有运动的情况下进行测试，并使用两个模拟呼吸信号：2 cm振幅正弦曲线和体模中具有3 cm线性漂移的2 cm振幅正弦曲线。对于患者计算，对肿瘤位置进行同等加权。根据体模中的通气中期CT图像和患者的呼气峰位置计算运动校正剂量。伽马评价为97.8%，无运动，95.7%为2厘米正弦运动，95.7%与3厘米漂移的幻影（2毫米，2%），和90.8%（3毫米，3%）的患者data.Conclusions：我们已经证明了一种方法，准确地再现质子剂量不规则移动的目标，从一个单一的CT图像。我们相信，该算法可以证明是一个有用的工具，研究剂量测定的影响，无论是在治疗前或治疗期间的基线偏移。
Purpose: While four-dimensional computed tomography (4DCT) and deformable registration can be used to assess the dose delivered to regularly moving targets, there are few methods available for irregularly moving targets. 4DCT captures an idealized waveform, but human respiration during treatment is characterized by gradual baseline shifts and other deviations from a periodic signal. This paper describes a method for computing the dose delivered to irregularly moving targets based on 1D or 3D waveforms captured at the time of delivery.Methods: The procedure uses CT or 4DCT images for dose calculation, and 1D or 3D respiratory waveforms of the target position at time of delivery. Dose volumes are converted from their Cartesian geometry into a beam-specific radiological depth space, parameterized in 2D by the beam aperture, and longitudinally by the radiological depth. In this new frame of reference, the proton doses are translated according to the motion found in the 1D or 3D trajectory. These translated dose volumes are weighted and summed, then transformed back into Cartesian space, yielding an estimate of the dose that includes the effect of the measured breathing motion. The method was validated using a synthetic lung phantom and a single representative patient CT. Simulated 4DCT was generated for the phantom with 2 cm peak-to-peak motion.Results: A passively-scattered proton treatment plan was generated using 6 mm and 5 mm smearing for the phantom and patient plans, respectively. The method was tested without motion, and with two simulated breathing signals: a 2 cm amplitude sinusoid, and a 2 cm amplitude sinusoid with 3 cm linear drift in the phantom. The tumor positions were equally weighted for the patient calculation. Motion-corrected dose was computed based on the mid-ventilation CT image in the phantom and the peak exhale position in the patient. Gamma evaluation was 97.8% without motion, 95.7% for 2 cm sinusoidal motion, 95.7% with 3 cm drift in the phantom (2 mm, 2%), and 90.8%(3 mm, 3%) for the patient data.Conclusions: We have demonstrated a method for accurately reproducing proton dose to an irregularly moving target from a single CT image. We believe this algorithm could prove a useful tool to study the dosimetric impact of baseline shifts either before or during treatment.