A Dual Quaternion Based Method for Estimating PTV Margins in Intensity-Modulated Radiotherapy

该项目旨在为影像引导治疗产生更好的靶区定义。为了覆盖 当肿瘤在治疗过程中移位时，临床靶点必须扩大到通过 它可能会移动它。在放射治疗中，扩大的靶点称为计划靶区体积。这个 国际辐射单位和测量委员会指出，现有的规划系统允许 只有笛卡尔展开式才能解释运动的三个平移分量。旋转式 位移的组成部分被忽略，产生的规划目标体积要么没有达到真正的目标 运动或大于覆盖目标路径所需的大小。当头部绕长轴弧形旋转时 脊椎，例如，规划目标体积不遵循与 椎前咽缩肌，但伸入这些结构，形成一个包围曲线的盒子。这个 重叠会产生更高的缩窄器剂量，这是头颈部晚期放射治疗的已知预测因素 并发症，包括有死亡风险和需要长期放置喂养管的抱负 依赖。对统计抽样进行了审查，主要是在欧洲，以根据观察到的情况绘制头寸 配准计划和处理图像所需的班次。这些方法失败是因为没有 旋转的交换性意味着正电子不能从位移的均匀采样中恢复 组件。六维采样置换旋转的计算负担是令人望而生畏的 并且忽略了远离目标中心的旋转。该方案旨在利用射影几何 以对偶四元数表示的位移，以形成目标扫出的位置的凸包 因为它在其平移、旋转角和旋转轴的范围内移动。计算实验 将使用头部和颈部病例进行演示，以演示在 可接受的时间范围(0.25小时)。规划目标体积大小、覆盖范围以及与咽部的重叠 通过形成由离轴旋转产生的位移的凸壳而产生的收缩 平移将被比作简单的笛卡尔展开。长期目标是减少治疗 发病率和提高目标覆盖率。减少发病率，如吸入风险，通过替代 对于常规的简单各向同性膨胀，新的靶体生成方法在未来是可以测试的 临床试验。

This project aims to produce a better definition of the target space for image guided therapy. In order to cover the tumor as it is displaced during treatment, the clinical target must be expanded to cover the region through which it might move. In radiation therapy, the expanded target is known as the Planning Target Volume. The International Commission on Radiation Units and Measurements notes that available planning systems allow only Cartesian expansions that account for the three translational components of motion. The rotational components of displacements are neglected, producing planning target volumes that either miss the true target motion or are larger than needed to cover the target path. As the head rotates in an arc about the long axis of the spine,eg, the planning target volume does not follow the true path of the target that tangents the prevertebral pharyngeal constrictors but juts into these structures to form a box that encloses the curve. The overlap produces higher constrictor doses, a known predictor for late head and neck radiotherapy complications including aspirations which carry mortality risk and necessitate long term feeding tube dependence. Statistical sampling has been examined, mainly in Europe, to draw positions based on observed shifts needed to register planning and treatment images. These methods breakdown because the non commutativity of rotations means that positons can’t be recovered from a uniform sampling of the displacement components. The computational burdens of a six dimensional sampling permuting the rotations is forbidding and rotations away from the target center are neglected This proposal aims to use the projective geometry of displacements expressed as dual quaternions to form the convex hull of the positions swept out by the target as it shifts within its range of translations, rotational angles and rotational axes. Computational experiments will be performed using head and neck cases, to demonstrate generation of planning target volumes within an acceptable time frame (0.25hr). The planning target volume size, coverage, and overlap with the pharyngeal constrictors produced by forming the convex hull of displacements generated by off axis rotations and translations will be compared to simple Cartesian expansions. The long term goal is to reduce treatment morbidity and improve target coverage. The reduction in morbidity, such as aspiration risk, from substituting the new method for target volume creation for conventional simple isotropic expansion is testable in future clinical trials.