Monitoring of fractures with internal fixators using weight-bearing quantitative cone beam CT

项目摘要/摘要 对于骨不连和延迟愈合的患者来说，骨折的医疗负担会加剧。 骨不连的预测和刺激骨生长的新疗法的开发受到缺乏 同时评估骨愈合的两个主要方面的定量、非侵入性测试：(I)矿物质 骨痂和骨折间隙的密度；(Ii)承重下的机械稳定性。要解决这个问题 挑战，我们提出使用一种新的四肢锥束CT系统(CBCT)，它提供了一种独特的能力 高空间分辨率的负重3D成像。这将允许测量骨骼的运动 通过估计碎片在承重和非承重扫描之间的位移 极端。此外，与传统CT非常相似，CBCT可以进行骨密度(BMD)测量 骨折的原因。为了能够对四肢CBCT上的骨折修复进行定量的负重评估， 必须减少金属固定硬件造成的伪影和图像不一致性。科学的前提是 这项工作是，金属硬件的影响可以通过组合新的双能量(DE)来最小化 适合于肢体CBCT和基于高级模型的图像重建(MBIR)的技术 手术硬件的先验知识。De成像将提供对衰减值的稳健校正 由于射束硬化而导致的不准确。高效的单次扫描实施DE CBCT将使用 肢体CBCT扫描仪上的创新多源配置。已知分量重构 算法(KCR)将被用来处理金属诱导的光子饥饿和非线性部分体积效应 利用金属部件的形状和姿势的先验知识。这种方法所固有的是一个 部件配准步骤，将提供在承重下的植入物变形的精确估计， 从而产生了一种评估断裂稳定性的新方法。将实现以下具体目标：1)使 基于一种新的DE MBIR算法和优化DE的多源CBCT数据的双能量CBCT 成像方案在模体中产生~5%的骨密度相对变化的检测；2)集成 精准(~0.5 mm靶区)重建MBIR DE的手术硬件先验知识 配准误差)骨折固定硬件的可变形3D-2D配准以估计部件姿势和 变形；3)对植入身体的已知成分DE算法进行临床翻译 四肢在受控负荷和先导性患者研究中。骨折患者将在2、4、8和12岁时进行成像 骨折后数周，观察骨折修复过程中骨痂矿化的变化。这 研究将建立一种创新的定量成像方法，用于同时、非侵入性评估 骨折修复的两个主要生物标志物：骨痂和骨折间隙的矿化和机械稳定性 在载荷作用下的植骨结构。

PROJECT SUMMARY / ABSTRACT The healthcare burden of fractures is exacerbated for patients who suffer from non-unions and delayed unions. Prediction of non-unions and development of new therapies stimulating bone growth is challenged by a lack of quantitative, non-invasive tests to simultaneously assess the two primary aspects of bone healing: (i) mineral density of the callus and fracture gap; and (ii) mechanical stability under weight-bearing. To address this challenge, we proposed to use a novel extremity cone-beam CT system (CBCT) that provides a unique capability of weight-bearing 3D imaging at high spatial resolution. This will allow measurement of the motion of bone fragments by estimating their displacement between weight-bearing and non-weight-bearing scans of the extremity. In addition, much like conventional CT, CBCT can perform bone mineral density (BMD) measurements of the fracture. To enable quantitative weight-bearing assessment of fracture repair on extremities CBCT, artifacts and image nonuniformity due to metal fixation hardware must be mitigated. The scientific premise of this work is that the effects of metal hardware can be minimized by a combination of novel Dual Energy (DE) techniques suitable for extremities CBCT and advanced model-based image reconstruction (MBIR) incorporating prior knowledge of the surgical hardware. DE imaging will provide a robust correction of the attenuation value inaccuracy due to beam hardening. Efficient, single-scan implementation of DE CBCT will be achieved using the innovative multi-source configuration on the extremities CBCT scanner. The Known-Component Reconstruction algorithm (KCR) will be used to address metal-induced photon starvation and nonlinear partial volume effects by exploiting prior knowledge of the shape and pose of the metal component. Inherent in this approach is a component registration step that will provide a precise estimate of implant deformation under weight-bearing, resulting in a novel approach to asses fracture stability. The following specific aims will be pursued: 1) Enable Dual Energy CBCT from multi-source CBCT data by means of an novel DE MBIR algorithm and optimized DE imaging protocols to yield detection of ~5% relative change in bone mineral density in phantoms; 2) Integrate prior knowledge of surgical hardware in MBIR DE reconstruction by exploiting accurate (~0.5 mm Target Registration Error) deformable 3D-2D registration of fracture fixation hardware to estimate component pose and deformation; 3) Perform clinical translation of the Known-Component DE algorithms in implanted cadaveric extremities under controlled load and in pilot patient study. Fracture patients will be imaged at 2, 4, 8 and 12 weeks post-fracture to demonstrate detection of changes in callus mineralization during fracture repair. This research will establish an innovative quantitative imaging approach for simultaneous, non-invasive assessment of two primary biomarkers of fracture repair: mineralization of the callus and fracture gap, and mechanical stability of the bone-implant construct under load.