Department of Radiation Oncology and Proton Medical Research Center, Tsukuba University, Ibaraki, Japan.
Radiother Oncol. 2011 May;99(2):124-30. doi: 10.1016/j.radonc.2011.05.009. Epub 2011 May 26.
This study is to evaluate reproducibility of hepatic tumors in end-expiration and end-inspiration on free-breathing, also measure shift of hepatic tumor location in pulsed proton beams exposure in end-expiration in order to estimate feasible planning target volume (PTV) margin.
Pairs (1232) of anterior and lateral radiographs from 30 patients (628 end-expiration and 604 end-inspiration phases) were analyzed using fiducial markers adjacent to the tumors. By using the co-ordinates of the marker centroid of mass related to the isocenter, intrafractional variation was compared in end-expiration and end-inspiration, and a feasible PTV margin was generated using the measured motion.
The average internal motion in end-expiration was 1.1mm, which was significantly smaller than that in end-inspiration. The mean deviation from the plan was -0.1, 0.3, and 0.1mm in the left-right (LR), cranio-cepharal (CC), and anterior-posterior (AP) directions, respectively. The estimated PTV margins were 3.2, 3.5, and 4.6mm, in the LR, CC, and AP directions, respectively.
It was indicated that localization of the targets was more reproducibility in end-expiration than that in end-inspiration. Also, feasible and practical margin values were obtained. These should contribute accuracy of respiration synchronized proton radiotherapy for liver tumors.
本研究旨在评估自由呼吸状态下肝肿瘤在呼气末和吸气末的可重复性，并测量脉冲质子束照射时呼气末肝肿瘤位置的移动，以估计可行的计划靶区（PTV）边界。
对 30 名患者的 1232 对前位和侧位片（628 个呼气末相位和 604 个吸气末相位）进行分析，使用邻近肿瘤的标记物。通过使用与等中心点相关的质量标记物的质心坐标，比较呼气末和吸气末的分次内变化，并使用测量的运动生成可行的 PTV 边界。
呼气末的平均内部运动为 1.1mm，明显小于吸气末。计划的平均偏差在左右（LR）、头脚（CC）和前后（AP）方向分别为-0.1、0.3 和 0.1mm。LR、CC 和 AP 方向的估计 PTV 边界分别为 3.2、3.5 和 4.6mm。
结果表明，呼气末时目标的定位比吸气末时更具可重复性。此外，还获得了可行和实际的边界值。这些应该有助于提高肝脏肿瘤呼吸同步质子放疗的准确性。
