A method for incorporating organ motion due to breathing into 3D dose calculations in the liver: Sensitivity to variations in motion
A method for incorporating organ motion due to breathing into 3D dose calculations in the liver: Sensitivity to variations in motion
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DOI：
10.1118/1.1609057
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发表时间：
2003-10-01
期刊：
影响因子：
3.8
通讯作者：
Ten Haken, RK
中科院分区：
文献类型：
--
作者：
Lujan, AE;Balter, JM;Ten Haken, RK
器官运动以前使用概率分布函数来描述，该函数仅依赖于运动的幅度和呼吸周期中的不对称程度，并且该函数已与患者特定参数一起使用剂量卷积方法来校正患者呼吸的静态剂量分布。在这项研究中，错误的选择这两个参数的后果进行了评估。以前使用局灶性肝剂量递增方案治疗的患者选择肿瘤位于肝脏上部或下部。对于一定程度的不对称（振幅），运动的振幅（不对称）在其标称值和器官运动对剂量分布和（潜在的新）处方剂量的影响进行了评估。这些比较表明，相对于标称测量值的运动幅度的微小变化（+/-3 mm）可能不会导致临床显著的变化（处方剂量的单个分数变化），然而，较大的变化（0.5 mm）可能导致显著的变化。根据测量假设患者呼吸不对称（呼气时花费更多时间），假设的不对称程度的变化很少导致临床显著的变化；最值得关注的是，当患者的呼吸周期与治疗计划的情况最大程度地不同时（例如，假设患者在呼气时花费更多的时间，但后来的呼吸是对称的）。结果指出，质量保证工作应该集中在哪里，以帮助确保使用卷积方法校正患者呼吸的静态剂量分布的假设的有效性。(C) 2003年美国医学物理学家协会。
Organ motion has been previously described using a probability distribution function that depends solely upon the amplitude: of motion and the degree of asymmetry in the breathing cycle, and that function has been used with patient specific parameters to correct static dose distributions for patient breathing using a dose convolution method. In this study, the consequences of errors in the selection of those two parameters were evaluated. Patients previously treated using a focal liver dose escalation protocol were selected with tumors located in the superior or inferior portion of the liver. For a fixed degree of asymmetry (amplitude), the amplitude (asymmetry) of motion was varied about its nominal, value and the consequences of organ motion on the dose distribution and the (potentially new) prescription dose were evaluated. These comparisons show that small (+/-3 mm) variations of the amplitude of motion about the nominally measured value may not result in clinically significant changes (< a single fraction change in the prescription dose), however, larger variations (>5 mm) can lead to significant changes. Assuming from measurement that the patient breathes asymmetrically (spends more time at expiration), variations in the assumed degree of asymmetry rarely lead to clinically significant changes; the most significant cause for concern being when the patient breathing cycle is maximally different from the treatment planning case (e.g., patient assumed to spend more time at expiration, but later breaths symmetrically). The results point out where quality assurance efforts should be concentrated to help assure the validity of the assumptions used to correct the static dose distributions for patient breathing using the convolution method. (C) 2003 American Association of Physicists in Medicine.