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Recovery of true scatter in blocked regions for blocker-based scatter correction of CBCT

恢复阻塞区域中的真实散射，用于 CBCT 的基于阻塞的散射校正

基本信息

批准号：
9293299
负责人：
Mingwu Jin
金额：
$ 7.67万
依托单位：
UNIVERSITY OF TEXAS ARLINGTON
依托单位国家：
美国
项目类别：
财政年份：
2016
资助国家：
美国
起止时间：
2016-06-15 至 2019-04-30
项目状态：
已结题

项目摘要

Recovery of true scatter in blocked regions for blocker-based scatter correction of CBCT Scatter correction (SC) is critically important to mitigate problems of shading artifacts, reduced contrast and inaccurate CT numbers of con-beam computed tomography (CBCT) for accurate and precise radiation dose delivery for image-guided adaptive radiotherapy. Among numerous SC methods, the use of lead-strip blockers is low-cost and easy to implement, where the signal detected in the blocked region is deemed scatter under an ideal condition to estimate scatter in the unblocked region. A moving-blocker approach has been developed to estimate scatter and reconstruct the volume image simultaneously from a single CBCT scan and holds the additional advantages of 1) high accuracy potential with subject-dependent measurements; 2) simple lead strip design; and 3) substantial dose reduction benefit (~50%). Since the signal in the blocked region is not pure scatter, heuristic parameter adjustment (denoted as manually tuned scatter estimation, MTSE) has to be done to achieve satisfying SC performance. Moreover, MTSE is hard to optimize these parameters in a spatially variant way and could produce heterogeneous reconstruction results, where large CT number errors (>100 HU) in some regions could occur and were clinically unacceptable (> 2% dose error) for treatment planning. In this work, we propose to overcome the problems of MTSE using rigorous modeling of the blocker-based image acquisition and deconvolution based scatter estimation (DBSE). Our goal is to eliminate manual parameter tuning and to achieve acceptable accuracy of reconstructed CT numbers over all regions of interest for dose calculation (< 100 HU, i.e. < 2% dose error) and significantly improved soft tissue contrast for effective organ segmentation. This goal will be achieved by the following specific aims: 1) to model the detector response function and the penumbra effect, which contaminate the scatter signal in the blocked region with the primary signal in the unblocked region; 2) to develop deconvlution methods for DBSE (frequency-domain methods, maximum likelihood estimate, and constrained optimization); and 3) to validate the model and to evaluate DBSE using Monte Carlo simulation and existing data of physical phantoms using clinically relevant criteria. Successful completion of this research will greatly improve the reliability, robustness, and accuracy of the moving-blocker technology and other blocker-based methods for CBCT, which is an important step to translate them into clinic for accurate soft-tissue localization and dose calculation in adaptive radiotherapy.

基于BLOCKER的CBCT散射校正中块区域真实散射的恢复散射校正(SC)对于缓解阴影伪影、对比度降低和用于精确和精确辐射剂量的共射束计算机断层扫描(CBCT)的CT数不准确影像引导自适应放射治疗的递送。在众多的SC方法中，使用铅条阻滞剂低成本且易于实现，其中在阻塞区域中检测到的信号被认为是在估计非阻塞区域散布的理想条件。一种移动拦截器的方法已经被开发出来从一次CBCT扫描中同时估计、散射和重建体积图像，并保持其他优点：1)与对象相关的测量具有高精度潜力；2)简单的铅条设计；以及3)显著的剂量减少效益(~50%)。由于阻塞区域中的信号不是纯的必须进行散布、启发式参数调整(表示为手动调整散布估计，MTSE 以达到令人满意的供应链绩效。此外，MTSE很难在空间上对这些参数进行优化不同的方式，可能产生不同的重建结果，其中CT数目误差较大(&gt；100 HU)在一些地区可能发生，并且对于治疗计划来说是临床不可接受的(&gt；2%剂量误差)。在这项工作中，我们建议使用基于阻滞剂的严格建模来克服MTSE的问题基于图像采集和反卷积的散布估计(DBSE)。我们的目标是淘汰人工参数调整，并在所有感兴趣的区域实现可接受的重建CT数精度用于剂量计算(&lt；100HU，即&lt；2%的剂量误差)，并显著改善软组织对比度，以实现有效器官分割。这一目标将通过以下具体目标来实现：1)对探测器进行建模响应函数和半影效应，其污染阻塞区域的散射信号非阻塞区域的一次信号；2)开发DBSE(频域)的去卷积方法方法、最大似然估计和约束最优化)；以及3)验证模型和使用蒙特卡罗模拟和现有的临床相关物理模型数据来评估DBSE 标准。这项研究的成功完成将极大地提高系统的可靠性、稳健性和准确性移动拦截器技术和其他基于拦截器的方法是CBCT的重要一步将其转化到临床上，用于适应性放射治疗中精确的软组织定位和剂量计算。