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

该项目旨在为图像引导治疗产生更好的靶空间定义。为了覆盖 当肿瘤在治疗期间移位时，临床目标必须扩大以覆盖该区域， 它可能会移动。在放射治疗中，扩展的目标被称为计划目标体积。的 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，它能解释运动的三个平移分量。旋转 位移分量被忽略，产生的规划目标体积要么错过真正的目标， 运动或大于覆盖目标路径所需的。当头部绕运动的长轴以弧形旋转时， 脊柱（例如，计划目标体积）不遵循与脊柱相切的目标的真实路径， 椎前咽缩肌，但突出到这些结构中以形成包围弯曲的盒。的 重叠产生更高的缩窄剂量，这是头颈部放射治疗晚期的一个已知预测因素 并发症，包括有死亡风险的误吸和需要长期喂食管 依赖主要在欧洲对统计抽样进行了审查， 配准计划和治疗图像所需的班次。这些方法之所以失败， 旋转的交换性意味着位置不能从位移的均匀采样中恢复 件.六维采样置换旋转的计算负担是可怕的 并且忽略远离目标中心的旋转。 表示为对偶四元数的位移，以形成目标扫过的位置的凸船体 因为它在其平移、旋转角度和旋转轴的范围内移动。计算实验 将使用头颈部病例进行，以证明在 可接受的时间范围（0.25小时）。计划靶体积大小、覆盖范围和与咽部的重叠 通过形成由离轴旋转产生的位移的凸形船体而产生的收缩器， 将平移与简单的笛卡尔展开进行比较。长期目标是减少治疗 提高发病率和提高目标覆盖率。减少发病率，如吸入风险，从替代 用于传统简单各向同性膨胀的靶体积创建的新方法在未来是可测试的 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.