Marschner Mathias, Birnbacher Lorenz, Willner Marian, Chabior Michael, Herzen Julia, Noël Peter B, Pfeiffer Franz
Chair of Biomedical Physics, Department of Physics and Munich School of BioEngineering, Technical University of Munich, 85748 Garching, Germany.
Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar, Technical University of Munich, 81675 München, Germany.
PLoS One. 2017 Sep 6;12(9):e0184217. doi: 10.1371/journal.pone.0184217. eCollection 2017.
Phase-contrast x-ray computed tomography (PCCT) is currently investigated as an interesting extension of conventional CT, providing high soft-tissue contrast even if examining weakly absorbing specimen. Until now, the potential for dose reduction was thought to be limited compared to attenuation CT, since meaningful phase retrieval fails for scans with very low photon counts when using the conventional phase retrieval method via phase stepping. In this work, we examine the statistical behaviour of the reverse projection method, an alternative phase retrieval approach and compare the results to the conventional phase retrieval technique. We investigate the noise levels in the projections as well as the image quality and quantitative accuracy of the reconstructed tomographic volumes. The results of our study show that this method performs better in a low-dose scenario than the conventional phase retrieval approach, resulting in lower noise levels, enhanced image quality and more accurate quantitative values. Overall, we demonstrate that the lower statistical limit of the phase stepping procedure as proposed by recent literature does not apply to this alternative phase retrieval technique. However, further development is necessary to overcome experimental challenges posed by this method which would enable mainstream or even clinical application of PCCT.
相衬X射线计算机断层扫描（PCCT）目前被作为传统CT的一项有趣扩展进行研究，即使在检查弱吸收标本时也能提供高软组织对比度。到目前为止，与衰减CT相比，人们认为剂量降低的潜力有限，因为当使用通过相位步进的传统相位恢复方法时，对于光子计数非常低的扫描，有意义的相位恢复会失败。在这项工作中，我们研究了反向投影法（一种替代的相位恢复方法）的统计行为，并将结果与传统的相位恢复技术进行比较。我们研究了投影中的噪声水平以及重建断层体积的图像质量和定量准确性。我们的研究结果表明，在低剂量情况下，该方法比传统的相位恢复方法表现更好，从而产生更低的噪声水平、更高的图像质量和更准确的定量值。总体而言，我们证明了最近文献中提出的相位步进程序的较低统计极限不适用于这种替代的相位恢复技术。然而，有必要进一步发展以克服该方法带来的实验挑战，这将使PCCT能够实现主流甚至临床应用。
