Stochastic noise characteristics in matrix inversion tomosynthesis (MITS).
Stochastic noise characteristics in matrix inversion tomosynthesis (MITS).
复制标题
矩阵反演断层合成 (MITS) 中的随机噪声特性。
DOI：
10.1118/1.3103399
复制
发表时间：
2009
期刊：
影响因子：
3.8
通讯作者：
Dobbins,JamesTThird
中科院分区：
文献类型：
--
作者：
Godfrey,DevonJ;McAdams,HP;Dobbins,JamesTThird
矩阵逆断层合成（MITS）使用已知的成像几何结构和线性系统理论来确定性地将平面内细节与一组常规断层合成（“移位和相加”）平面中的残余断层摄影模糊分离。先前的研究探讨了扫描角度（ANG）、投影数量和重建平面数量（NP）对MITS脉冲响应和调制传递函数特性的影响，并得出结论，和是我们的原型断层合成系统上胸部成像的最佳MITS成像技术。本文检查了ANG、和NP对MITS曝光归一化噪声功率谱（ENG）的影响，并试图确认先前通过分析MITS脉冲响应选择的成像参数也会在MITS重建平面中产生合理的随机特性。针对实验采集的平均减影投影图像、传统断层合成平面和MITS平面，使用不同的参数ANG、和NP组合生成ENERGY曲线。使用原型断层合成系统收集图像数据，在图像接收器附近放置11.4 cm丙烯酸树脂，以产生肺等效射束硬化和散射辐射。对于每种选定的技术，收集10个相同采集的断层合成数据集（实现），并用于生成总体平均图像，在噪声功率谱（SNR）估计之前，从单个图像实现中减去这些图像。将ENK曲线标准化以考虑入口暴露的差异（如用离子室测量的），得到每种技术的ENK估计值。结果表明，MITS平面中的中频和高频噪声在幅度上与传统断层合成平面中的噪声相当，但低频噪声在最前部和后部重建平面中被放大。选择最大可用数量的投影不会导致任何明显的附加电子噪声惩罚相比，使用较少的投影大致相等的累积曝光。随机噪声通过最大化和NP最小化，但随着ANG的增加而增加。NP和ANG的噪声趋势结果与通过简单考虑MITS矩阵调节预测的结果相反，并且可能是噪声相关性和MITS滤波器极性之间的相互作用的结果。从这项研究中，作者得出结论，先前确定的最佳MITS成像策略的基础上脉冲响应的考虑，产生一些次优的随机噪声特性，但可能仍然是最好的技术MITS成像的胸部。
Matrix inversion tomosynthesis (MITS) uses known imaging geometry and linear systems theory to deterministically separate in‐plane detail from residual tomographic blur in a set of conventional tomosynthesis (“shift‐and‐add”) planes. A previous investigation explored the effect of scan angle (ANG), number of projections , and number of reconstructed planes (NP) on the MITS impulse response and modulation transfer function characteristics, and concluded that , , and is the optimal MITS imaging technique for chest imaging on our prototype tomosynthesis system. This article examines the effect of ANG, , and NP on the MITS exposure‐normalized noise power spectra (ENNPS) and seeks to confirm that the imaging parameters selected previously by an analysis of the MITS impulse response also yield reasonable stochastic properties in MITS reconstructed planes. ENNPS curves were generated for experimentally acquired mean‐subtracted projection images, conventional tomosynthesis planes, and MITS planes with varying combinations of the parameters ANG, , and NP. Image data were collected using a prototype tomosynthesis system, with 11.4 cm acrylic placed near the image receptor to produce lung‐equivalent beam hardening and scattered radiation. Ten identically acquired tomosynthesis data sets (realizations) were collected for each selected technique and used to generate ensemble mean images that were subtracted from individual image realizations prior to noise power spectra (NPS) estimation. NPS curves were normalized to account for differences in entrance exposure (as measured with an ion chamber), yielding estimates of the ENNPS for each technique. Results suggest that mid‐ and high‐frequency noise in MITS planes is fairly equivalent in magnitude to noise in conventional tomosynthesis planes, but low‐frequency noise is amplified in the most anterior and posterior reconstruction planes. Selecting the largest available number of projections does not incur any appreciable additive electronic noise penalty compared to using fewer projections for roughly equivalent cumulative exposure. Stochastic noise is minimized by maximizing and NP but increases with increasing ANG. The noise trend results for NP and ANG are contrary to what would be predicted by simply considering the MITS matrix conditioning and likely result from the interplay between noise correlation and the polarity of the MITS filters. From this study, the authors conclude that the previously determined optimal MITS imaging strategy based on impulse response considerations produces somewhat suboptimal stochastic noise characteristics, but is probably still the best technique for MITS imaging of the chest.