Panin Vladimir Y, Matej Samuel
Siemens Medical Solutions USA, Molecular Imaging, Knoxville, Tennessee, United States.
University of Pennsylvania, Department of Radiology, Philadelphia, Pennsylvania, United States.
J Med Imaging (Bellingham). 2020 May;7(3):032505. doi: 10.1117/1.JMI.7.3.032505. Epub 2020 Jun 2.
In spite of the general acceptance of iterative reconstruction for clinical use, analytic algorithms provide an important alternative tool due to their linearity, unbiased performance, and predictability for quantitative imaging and quality control studies. On modern time-of-flight (TOF) positron emission tomography scanners with excellent timing resolution, substantial angular compression of (histoprojection) data is possible without loss of resolution, but this also brings challenges for analytical algorithms. We propose TOF and non-TOF Fourier-based analytic approaches that appropriately handle the data sparsity on modern TOF systems. The proposed TOF algorithm (3D-DIFTOF-direct inversion Fourier transform for TOF) works directly on histoprojection data. The proposed Fourier-based approaches for histoprojection data are further extended to include non-TOF reconstruction (TOF-binned 3D-DIFT), which is particularly useful in time calibration procedures due to its insensitivity to time calibration errors. TOF information is used here to extend available histoprojection data to a larger number of views, essential for artifact-free non-TOF reconstruction. The proposed algorithms are compared with standard analytic techniques on Siemens scanners-space-based confidence-weighted TOF FBP and non-TOF DIFT. 3D-DIFTOF reconstruction demonstrates both improved NEMA-based resolution and contrast versus background variability trade-offs. Similarly, the TOF-binned 3D-DIFT approach shows improved contrast-noise trade-offs over the standard non-TOF approach and is well suited for timing calibration. Our results demonstrate that the proposed 3D-DIFTOF technique provides an improved and more faithful characterization of image resolution compared with standard space-based analytic reconstructions. The proposed tools also provide accurate translation of sparse TOF data available on clinical scanners to upsampled data for non-TOF algorithms.
尽管迭代重建已被广泛应用于临床，但解析算法因其线性、无偏性能以及在定量成像和质量控制研究中的可预测性，提供了一种重要的替代工具。在具有出色时间分辨率的现代飞行时间（TOF）正电子发射断层扫描仪上，（组织投影）数据可以在不损失分辨率的情况下进行大幅角度压缩，但这也给解析算法带来了挑战。我们提出了基于TOF和非TOF傅里叶的解析方法，以适当处理现代TOF系统上的数据稀疏性。所提出的TOF算法（3D-DIFTOF-TOF直接反演傅里叶变换）直接作用于组织投影数据。所提出的基于傅里叶的组织投影数据方法进一步扩展到包括非TOF重建（TOF分箱3D-DIFT），由于其对时间校准误差不敏感，在时间校准程序中特别有用。这里使用TOF信息将可用的组织投影数据扩展到更多视图，这对于无伪影的非TOF重建至关重要。将所提出的算法与西门子扫描仪上的标准解析技术——基于空间的置信加权TOF FBP和非TOF DIFT进行比较。3D-DIFTOF重建在基于NEMA的分辨率和对比度与背景变异性权衡方面均有改善。同样，TOF分箱3D-DIFT方法在对比度-噪声权衡方面比标准非TOF方法有所改善，并且非常适合时间校准。我们的结果表明，与标准的基于空间的解析重建相比，所提出的3D-DIFTOF技术在图像分辨率的表征方面有改进且更准确。所提出的工具还能将临床扫描仪上可用的稀疏TOF数据准确转换为非TOF算法的上采样数据。
