Maximum distance in single-isocenter technique of stereotactic radiosurgery with rotational error using margin-based analysis
Maximum distance in single-isocenter technique of stereotactic radiosurgery with rotational error using margin-based analysis
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DOI：
10.1007/s12194-020-00602-2
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发表时间：
2021-01-03
影响因子：
1.6
通讯作者：
Ishikawa, Hiroyuki
中科院分区：
文献类型：
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作者：
Nakano, Hisashi;Tanabe, Satoshi;Ishikawa, Hiroyuki
通过几何模拟，我们评估了患者设置时旋转误差对几何覆盖的影响，并计算了等中心与目标之间的最大距离，其中临床PTV边缘通过单等中心技术确保几何覆盖。我们使用直径分别为1.0 cm （GTV 1）、1.5 cm （GTV 2）、2.0 cm （GTV 3）和3.0 cm （GTV 4）的模拟球形GTV。设定目标中心的位置，使目标与等中心之间的距离为0 ~ 15 cm。我们创建了几何覆盖向量，以便每个目标都被100%的规定剂量完全覆盖。目标位置的矢量同时围绕x、y和z轴在0 -2.0度范围内旋转。对于每个旋转误差，计算目标几何覆盖的减少量，并与旋转误差为0度时的减少量进行比较。几何覆盖度减少的容差值定义为GTV的5%。在临床PTV边缘为0.1 cm时，计算不同旋转误差值满足5%容差值的最大距离。当旋转误差为0.5度，PTV裕度为0.1 cm时，最大距离为：GTV 1: 7.6 cm；GTV 2: 10.9 cm；GTV 3: 14.3 cm；GTV 4: 21.4 cm。为了满足所有gtv的容差值，在单等心技术中，排除距离等心0 ~ 7.6 cm的目标是可取的。
Through geometrical simulation, we evaluated the effect of rotational error in patient setup on geometrical coverage and calculated the maximum distance between the isocenter and target, where the clinical PTV margin secures geometrical coverage with a single-isocenter technique. We used simulated spherical GTVs with diameters of 1.0 (GTV 1), 1.5 (GTV 2), 2.0 (GTV 3), and 3.0 cm (GTV 4). The location of the target center was set such that the distance between the target and isocenter ranged from 0 to 15 cm. We created geometrical coverage vectors so that each target was entirely covered by 100% of the prescribed dose. The vectors of the target positions were simultaneously rotated within a range of 0 degrees-2.0 degrees around the x-, y-, and z-axes. For each rotational error, the reduction in geometrical coverage of the targets was calculated and compared with that obtained for a rotational error of 0 degrees. The tolerance value of the geometrical coverage reduction was defined as 5% of the GTV. The maximum distance that satisfied the 5% tolerance value for different values of rotational error at a clinical PTV margin of 0.1 cm was calculated. When the rotational errors were 0.5 degrees for a 0.1 cm PTV margin, the maximum distances were as follows: GTV 1: 7.6 cm; GTV 2: 10.9 cm; GTV 3: 14.3 cm; and GTV 4: 21.4 cm. It might be advisable to exclude targets that are > 7.6 cm away from the isocenter with a single-isocenter technique to satisfy the tolerance value for all GTVs.