Relative role of motion and PSF compensation in whole-body oncologic PET-MR imaging.
Relative role of motion and PSF compensation in whole-body oncologic PET-MR imaging.
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DOI：
10.1118/1.4868458
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发表时间：
2014-04
期刊：
影响因子：
3.8
通讯作者：
Y. Petibon;Chuan Huang;J. Ouyang;T. Reese;Quanzheng Li;Aleksandra Syrkina;Yen-Lin E Chen;G. El Fakhri-G.
中科院分区：
文献类型：
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作者：
Y. Petibon;Chuan Huang;J. Ouyang;T. Reese;Quanzheng Li;Aleksandra Syrkina;Yen-Lin E Chen;G. El Fakhri-G.
呼吸运动和部分容积效应是全身PET成像中图像退化的两个主要来源。同步PET-MR允许在收集PET事件的同时使用MRI测量呼吸运动。可以通过在PET迭代重建过程内对呼吸运动和点扩散函数（PSF）进行建模来获得改进的PET图像。在本研究中，作者使用全身PET-MR扫描仪评估了PSF建模和基于MR的呼吸运动校正在体模和患者研究中的相对影响。方法从PET-MR扫描仪中进行的点源采集中获得一个非对称指数PSF模型，该模型考虑了径向变化和轴向探测器模糊效应。开发了一种专用MRI采集协议，使用单层稳态自由进动MR采集与双光束导航回波交错，以跟踪PET-MR研究期间的呼吸运动。开发了一种迭代普通泊松全三维OSEM PET重建算法，该算法对采集的所有物理效应（衰减、散射、随机事件、探测器效率、PSF）以及组织的基于MR的非刚性呼吸变形（在发射图和衰减图中）进行建模。进行了体模和（18）F-FDG PET-MR患者研究，以评价拟议的定量PET-MR方法。结果体模实验结果表明，PSF建模在抑制噪声传播的同时，显著提高了对比度恢复。在软组织静态病变患者中，PSF建模将病变对比度提高了19.7%-109%，增强了小肿瘤病灶的可检测性和评估。在一项小型移动肝脏病变的患者研究中，提出的重建技术将病变对比度提高了54.4%-98.1%，并将明显病变尺寸减小了21.8%-34.2%。对于在肺-肝界面经历大运动的最小病变，改善尤其重要。异质性肿瘤结构勾画得到显著改善。PSF建模提供的增强功能在同时校正运动时更为重要。结论与传统方法相比，本文提出的定量PET-MR方法可以显著提高肿瘤诊断和分期的性能。这种方法可以使扫描仪的全部潜力，在肿瘤学研究的下腹部，与移动病变，以及其他部分的身体不受运动。
PURPOSE Respiratory motion and partial-volume effects are the two main sources of image degradation in whole-body PET imaging. Simultaneous PET-MR allows measurement of respiratory motion using MRI while collecting PET events. Improved PET images may be obtained by modeling respiratory motion and point spread function (PSF) within the PET iterative reconstruction process. In this study, the authors assessed the relative impact of PSF modeling and MR-based respiratory motion correction in phantoms and patient studies using a whole-body PET-MR scanner. METHODS An asymmetric exponential PSF model accounting for radially varying and axial detector blurring effects was obtained from point source acquisitions performed in the PET-MR scanner. A dedicated MRI acquisition protocol using single-slice steady state free-precession MR acquisitions interleaved with pencil-beam navigator echoes was developed to track respiratory motion during PET-MR studies. An iterative ordinary Poisson fully 3D OSEM PET reconstruction algorithm modeling all the physical effects of the acquisition (attenuation, scatters, random events, detectors efficiencies, PSF), as well as MR-based nonrigid respiratory deformations of tissues (in both emission and attenuation maps) was developed. Phantom and(18)F-FDG PET-MR patient studies were performed to evaluate the proposed quantitative PET-MR methods. RESULTS The phantom experiment results showed that PSF modeling significantly improved contrast recovery while limiting noise propagation in the reconstruction process. In patients with soft-tissue static lesions, PSF modeling improved lesion contrast by 19.7%-109%, enhancing the detectability and assessment of small tumor foci. In a patient study with small moving hepatic lesions, the proposed reconstruction technique improved lesion contrast by 54.4%-98.1% and reduced apparent lesion size by 21.8%-34.2%. Improvements were particularly important for the smallest lesion undergoing large motion at the lung-liver interface. Heterogeneous tumor structures delineation was substantially improved. Enhancements offered by PSF modeling were more important when correcting for motion at the same time. CONCLUSIONS The results suggest that the proposed quantitative PET-MR methods can significantly enhance the performance of tumor diagnosis and staging as compared to conventional methods. This approach may enable utilization of the full potential of the scanner in oncologic studies of both the lower abdomen, with moving lesions, as well as other parts of the body unaffected by motion.