The effect of averaging adjacent planes for artifact reduction in matrix inversion tomosynthesis
The effect of averaging adjacent planes for artifact reduction in matrix inversion tomosynthesis
复制标题
DOI：
10.1118/1.4773891
复制
发表时间：
2013-02-01
期刊：
影响因子：
3.8
通讯作者：
Dobbins, James T., III
中科院分区：
文献类型：
--
作者：
Godfrey, Devon J.;McAdams, H. Page;Dobbins, James T., III
目的：矩阵逆断层合成（MITS）使用线性系统理论和成像几何学的知识来去除常规反投影断层合成重建中存在的断层摄影模糊，留下清晰呈现的平面内细节。在反投影过程中使用部分像素插值在断层摄影模糊的MITS建模中引入了不精确性，并且在一些MITS平面中创建了低对比度伪影。本文探讨使用MITS板，平均几个相邻的MITS平面，作为一种方法，用于抑制partial-pixel artifacts.Methods：人类胸部断层合成投影数据，作为IRB批准的试点研究的一部分，被用来生成MITS平面，三平面MITS板（MITSa 3），五平面MITS板（MITSa 5），和七平面MITS板（MITSa 7）。对这些图像进行了定性检查，以确定部分像素伪影以及正常和异常解剖结构的可见性。此外，模拟小（5 mm）细微肺结节，并将其数字叠加在人体胸部断层合成投影图像上，并在不同重建技术中对其可见性进行定性评估。模拟图像的细线被用来产生调制传递函数（MTF）和切片灵敏度曲线的不同MITS和MITS板技术，这些进行了检查的指示部分像素的文物和频率响应的均匀性。最后，平均减去，归一化的噪声功率谱（ENERGY）的估计进行了计算和比较MITS和MITS板重建，从10组断层合成投影数据的丙烯酸板。每种技术的模拟面内MTF响应也结合了ENERGY估计的平方根，以产生不同的重建techniques.Results的随机信号噪声比（SNR）的信息：对于扫描角度为20度和5 mm的平面分离，七个MITS平面必须进行平均，以充分去除部分像素的伪影。MITSa 7似乎确实微妙地降低了高频“边缘”信息的对比度，但部分像素伪影的去除使得低对比度、精细细节解剖结构的外观在MITSa 7切片中更加明显。MITSa 7似乎还在开放肺和覆盖纵隔的区域中呈现比单独的MITS具有更高可见性的模拟的细微5 mm肺结节。最后，MITSa 7技术降低了随机图像方差，尽管平面内随机SNR（对于不跨越多个MITS平面的非常薄的物体）仅在0.05和0.20 cycle/mm之间的空间频率下得到改善。MITSa 7方法是对传统单平面MITS的改进，用于胸部成像和肺结节检测任务，因此，作者计划在作者所在机构的所有未来MITS研究中使用MITSa 7方法。(c)2013年美国医学物理学家协会。[http：//dx.doi.org/10.1118/1.4773891]
Purpose: Matrix inversion tomosynthesis (MITS) uses linear systems theory and knowledge of the imaging geometry to remove tomographic blur that is present in conventional backprojection tomosynthesis reconstructions, leaving in-plane detail rendered clearly. The use of partial-pixel interpolation during the backprojection process introduces imprecision in the MITS modeling of tomographic blur, and creates low-contrast artifacts in some MITS planes. This paper examines the use of MITS slabs, created by averaging several adjacent MITS planes, as a method for suppressing partial-pixel artifacts.Methods: Human chest tomosynthesis projection data, acquired as part of an IRB-approved pilot study, were used to generate MITS planes, three-plane MITS slabs (MITSa3), five-plane MITS slabs (MITSa5), and seven-plane MITS slabs (MITSa7). These were qualitatively examined for partial-pixel artifacts and the visibility of normal and abnormal anatomy. Additionally, small (5 mm) subtle pulmonary nodules were simulated and digitally super-imposed upon human chest tomosynthesis projection images, and their visibility was qualitatively assessed in the different reconstruction techniques. Simulated images of a thin wire were used to generate modulation transfer function (MTF) and slice-sensitivity profile curves for the different MITS and MITS slab techniques, and these were examined for indications of partial-pixel artifacts and frequency response uniformity. Finally, mean-subtracted, exposure-normalized noise power spectra (ENNPS) estimates were computed and compared for MITS and MITS slab reconstructions, generated from 10 sets of tomosynthesis projection data of an acrylic slab. The simulated in-plane MTF response of each technique was also combined with the square root of the ENNPS estimate to yield stochastic signal-to-noise ratio (SNR) information about the different reconstruction techniques.Results: For scan angles of 20 degrees and 5 mm plane separation, seven MITS planes must be averaged to sufficiently remove partial-pixel artifacts. MITSa7 does appear to subtly reduce the contrast of high-frequency "edge" information, but the removal of partial-pixel artifacts makes the appearance of low-contrast, fine-detail anatomy even more conspicuous in MITSa7 slices. MITSa7 also appears to render simulated subtle 5 mm pulmonary nodules with greater visibility than MITS alone, in both the open lung and regions overlying the mediastinum. Finally, the MITSa7 technique reduces stochastic image variance, though the in-plane stochastic SNR (for very thin objects which do not span multiple MITS planes) is only improved at spatial frequencies between 0.05 and 0.20 cycles/mm.Conclusions: The MITSa7 method is an improvement over traditional single-plane MITS for thoracic imaging and the pulmonary nodule detection task, and thus the authors plan to use the MITSa7 approach for all future MITS research at the authors' institution. (c) 2013 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4773891]