Optimizing MRI for Radiation Therapy Treatment Planning

描述(申请人提供)：虽然磁共振成像(MRI)在放射治疗(RT)计划和评估中具有显著优势，但由于担心扭曲、支持剂量计算的能力以及支持治疗单元图像指导的信息缺失，其作用仅限于支持计算机断层扫描(CT)RT。这个项目追求的假设是，MRI RT至少可以被证明与CT RT一样准确，这清楚地意味着MRI RT实际上将远远超过CT的好处。具体目标是：SA1通过结合采集和处理方法来评估和提高常规MRI脉冲序列的几何精度，以最大限度地减少残余失真，并执行体模和患者特定的评估，以确定残余几何误差是否在RT SA2的可接受范围内。优化患者建模方法，以创建最适合进行RT SA3的患者的轮廓、剂量计算和图像引导定位的MRI派生表示。3进行虚拟临床试验，以证明基于MRI RT的治疗决策不逊于CT RT得出的治疗决策。本项目将探索两种失真校正方法(校正和场映射)，并将表征MRI的几何精度。增强骨骼信号、量化脂肪和水分分布并提供与其他组织不同对比的成像技术将通过聚类技术进行分析，以标记组织/材料类型(例如，游离液体、致密固体组织、骨、分离或嵌入其他组织中的各种脂肪浓度)。这些分类的组织可以被分配属性，以生成用于剂量计算的电子密度图，以及用于轮廓绘制和图像引导的新的患者模型。将进行一项虚拟临床试验，以评估MRI RT相对于CT RT的准确性。这项研究将支持从某些患者的计划过程中删除多余的和潜在的混杂CT扫描。它将促进使用MRI衍生的生理学、分子和先进的形态信息进行治疗计划。它将加强学术和私立医院诊断放射科和放射治疗部门之间在优化影像资源利用方面的合作发展。它将有助于优化患者的工作流程，这些患者可能会使用不断发展的下一代核磁共振引导远程治疗系统进行治疗。最后，它将直接支持使用新兴的MRI衍生生物标记物进行个性化适应性放射治疗，并将降低纵向评估治疗结果的成本和复杂性。在不太可能的情况下，基于CT的放射治疗仍然被证明是更好的，这些研究将改善MR的几何完整性，以最大限度地有利于基于CT的患者模型的增强。这也将影响MRI在指导非放射治疗如手术、聚焦消融和图像引导活检方面的价值。

DESCRIPTION (provided by applicant): While Magnetic Resonance Imaging (MRI) has significant advantages in Radiation Therapy (RT) planning and assessment, its role is limited to support of computed tomography (CT) RT due to concerns about distortion, ability to support dose calculations, and missing information to support image guidance at the treatment unit. This project pursues the hypothesis that MRI RT can be shown to be at least as accurate as CT RT, with the clear implication that MRI RT will in fact far exceed the benefits of CT. The specific aims are: SA1 Assess and improve the geometric accuracy of routine MRI pulse sequences by combining acquisition and processing methods to minimize residual distortions, and performing phantom and patient-specific assessments to determine whether residual geometric errors are within acceptable bounds for RT SA2 Optimize patient modeling methods to create MRI-derived representations most appropriate for contouring, dose calculation, and support of image-guided positioning of patients undergoing RT SA3 Conduct virtual clinical trials to demonstrate that treatment decisions based on MRI RT are not inferior to those derived from CT RT This project will explore two methods of distortion correction (rectification and field mapping), and will characterize the geometric accuracy of MRI. Imaging techniques that enhance signals from bone, quantify fat and water distributions, and provide differential contrast from other tissues, will be analyzed via clustering techniques to label tissue/material types (e.g. free fluid, dense solid tissue, bone, various fat concentrations isolated or embedded within other tissues). These classified tissues can be assigned properties to generate electron density maps for dose calculation as well as new patient models for contouring and image guidance. A virtual clinical trial will be performed to evaluate the accuracy of MRI RT relative to CT RT. This research will support removal of redundant and potentially confounding CT scans from the planning process for certain patients. It will facilitate the use of MRI-derived physiologic, molecular, and advance morphologic information for treatment planning. It will enhance collaborative development of optimized imaging resource utilization between diagnostic radiology and radiotherapy departments in academic as well as private hospital settings. It will help optimize workflow for patients that may be treated with the evolving next generation of MRI-guided teletherapy systems. Finally it will directly support the use of emerging MRI-derived biomarkers for individualized adaptive radiotherapy, and will reduce the cost as well as complexity of longitudinal assessment of treatment outcome. In the unlikely event that CT-based radiotherapy is still demonstrated to be better, these investigations will improve the geometric integrity of MR to maximally benefit augmentation of CT-based patient models. This will also impact the value of MRI in guiding non-radiotherapy focal interventions such as surgery, focused ablation, and image-guided biopsy.