Super-Resolution PET Using Stepping of a Deliberately Misaligned Bed

描述(由申请人提供)：本建议的目标是测试正电子发射断层扫描(PET)成像特性的两个假设：(1)通过在采集期间通过患者床沿扫描仪的轴向故意但仔细且准确地近乎连续地运动来对体素进行超采样，可以大幅提高全身PET系统的重建精度；以及(2)超采样将允许使用分辨率恢复技术的迭代算法来提高分辨率，这超出了那些算法在没有超采样的情况下所能达到的效果。抖动超分辨率是早期脑PET系统中用于改善采样的一种技术，这通常会提高分辨率并减少伪影。随着块探测器和全身系统的引入，抖动消失了，因为它的机械繁琐和额外的费用是不合理的，因为对重建的影响可以忽略不计。这是因为块检测器大大减小了晶体尺寸，与读出过程中的线性和信号失真等其他影响相比，降低了晶体尺寸对系统整体分辨率的重要性。因此，采样对分辨率的改善不成比例。自消除摆动以来，扫描仪发生了两个重大变化：(1)3D采集大大增加了计数统计，这支持更小特征的准确重建；(2)分辨率恢复迭代算法已经变得司空见惯。我们认为，改进采样将导致现代重建的准确性和分辨率提高，同时伪影将减少，因为分辨率再次变得比采样更好。我们提出了一种新的方法来增加采样，包括轴向采样，该方法不需要额外的硬件，使该解决方案可能对未来系统的供应商具有吸引力，并作为现有系统的低成本升级，如果该建议的假设得到证实的话。该方法在床位对准中引入了一个小角度，并结合使用现有的床位电机对对象进行超采样，不需要额外的扫描时间。当床层轴向移动时，会产生较小的轴向位移。这项建议的具体目的包括：(I)通过模拟确定最佳的步进模式和床位对准角度；(Ii)修改现有的重建软件以纳入床位信息；以及(Iii)在我们实验室的TOF研究型扫描仪LaPET上进行实验测试。这些目标将使我们能够充分解决这项提案的假设。

DESCRIPTION (provided by applicant): The objective of this proposal is to test two hypotheses of the imaging characteristics of positron emission tomography (PET): (1) that substantial improvements in reconstruction accuracy can be obtained for whole-body PET systems by super-sampling voxels during acquisition through the near-continuous motion of the patient bed along a direction intentionally - but carefully and accurately - misaligned with respect to the scanner's axial direction; and (2) that super-sampling will allow resolution improvement with iterative algorithms using resolution-recovery techniques, beyond what those algorithms can achieve without super-sampling. Super-resolution through wobbling is a technique historically used in early brain PET systems to improve the sampling, which would typically improve resolution and reduce artifacts. With the introduction of block detectors and whole-body systems, wobbling disappeared because its mechanical cumbersomeness and added expense were not justified since the impact on reconstruction was negligible. This is because the block detectors greatly reduced the crystal size, reducing the importance of crystal size on overall system resolution in comparison with other effects such as acolinearity and signal distortions in readout. Thus, the sampling improved disproportionately to the resolution. Two significant changes have occurred since wobbling was removed from scanners: (1) 3D acquisitions greatly increased the count statistics, which supports the accurate reconstruction of smaller features; and (2) resolution-recovery iterative algorithms have become commonplace. We believe that improving sampling will result in increased accuracy and resolution of modern reconstructions while artifacts will be reduced because resolutions are once again becoming better in comparison to the sampling. We propose a novel method for increasing sampling, including axial sampling, that does not require additional hardware, making the solution possibly attractive to vendors for future systems and as low-cost upgrades to existing systems, if the hypotheses of this proposal are confirmed. The method introduces a small angle in the bed alignment combined with the use of existing bed motors to super-sample the object, requiring no additional scan time. When the bed moves axially, a small transaxial shift results. The specific aims of this proposal include: (i) determining through simulation the optimal stepping pattern and bed-alignment angle; (ii) modifying existing reconstruction software to incorporate the bed-position information; and (iii) experimentally test the method on a TOF research scanner, LaPET, that is in our laboratory. These aims will allow us to fully address the hypotheses of this proposal.