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Optimization and evaluation of 4D MAP-RBI-EM image reconstruction method for gated myocardial perfusion SPECT.

机译：门控心肌灌注SPECT的4D MAP-RBI-EM图像重建方法的优化和评估。

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The objective of this research was to investigate the parameters of generalized 4D space-time Gibbs priors used in 4D MAP-RBI-EM image reconstruction method and to develop a task-based human observer study to evaluate and optimize the method for application to gated myocardial perfusion (GMP) SPECT. To study the characteristics of the parameters, we created simulated GMP SPECT data from a realistic 4D NCAT phantom modeling the uptake distribution of Tc-99m Sestamibi. Noise-free and noisy projection data were generated using an analytical projector that included the effects of attenuation, collimator-detector response and scatter (ADS). The normalized mean squared error (NMSE) in noise-free images and the averaged normalized standard deviation (NSDav) in noisy images were used to describe the spatial and temporal image fidelity with respect to its true phantom image, and image noise magnitude, respectively. We postulated that the optimal value ranges for each parameter of the image reconstruction methods for best image quality were within the region where the trade off was minimum for both NMSE and the NSDav. The results showed that the 4D MAP-RBI-EM with parameters in their own optimal range and correction of image degrading factors provides improved reconstructed image quality as compared to 3D FBP method followed by 4D post-filtering or 3D OS-EM method with the same correction followed by 4D post-filtering. Based on these results, we used a task-based human observer study to evaluate the proposed method and to find the optimal NMSE-NSDav trade-off for the detection task of abnormal myocardial wall motion. Using the 4D NCAT phantom, we created a realistic hypokinetic cardiac motion model as well as a normal motion model. The projection data were generated in the same way as above, and reconstructed using the 3D FBP and the 3D OS-EM methods with ADS corrections followed by different cut-off frequencies of the 4D post-filter to include the reconstructed images from a wide range of the NMSE-NSDav trade-off for the observer study. 4D MAP-RBI-EM method with ADS corrections was also used to reconstruct the projection data using different combinations of prior parameters. Using a newly developed motion image display application for human observer studies, observers were trained to the multi-sliced and multi-oriented gated SPECT images animated with a realistic real-time frame rate, and were instructed to rate their confidence on the absence or presence of a regional myocardial motion defect on a continuous scale. We applied receiver operating characteristic (ROC) analysis and used the area under the ROC curve (AUC) as an index of performance for comparison. The result showed that 4D MAP-RBI-EM with ADS correction had the highest AUC value, resulting in significantly better human observer detection performance among the tested methods, and that the optimal NMSE-NSDav trade-off from optimized reconstruction parameters corresponded to the maximum AUC value for each method. We found that the NMSE-NSD av trade-off could be used as a useful guide in choosing the optimal range of parameter values for each method, and conclude that the optimized 4D MAP-RBI-EM method with corrections for image degrading factors provides significant improvement in detecting wall motion abnormalities with GMP SPECT.
机译：这项研究的目的是研究用于4D MAP-RBI-EM图像重建方法的广义4D时空吉布斯先验参数，并开展基于任务的人类观察者研究，以评估和优化该方法应用于门控心肌灌注（GMP）SPECT。为了研究参数的特征，我们从逼真的4D NCAT幻象创建了模拟的GMP SPECT数据，该模型对Tc-99m Sestamibi的吸收分布进行了建模。使用分析型投影仪生成无噪声且有噪声的投影数据，其中包括衰减，准直仪-检测器响应和散射（ADS）的影响。无噪图像中的归一化均方误差（NMSE）和噪声图像中的归一化平均标准差（NSDav）分别用于描述相对于其真实幻像和图像噪声幅度的空间和时间图像保真度。我们假设，对于最佳图像质量，图像重建方法的每个参数的最佳值范围都在NMSE和NSDav的权衡最小的区域内。结果表明，与3D FBP方法，4D后置滤波或3D OS-EM方法相比，具有在其自身最佳范围内的参数和图像退化因素校正的4D MAP-RBI-EM提供了改进的重建图像质量。校正，然后进行4D后过滤。基于这些结果，我们使用了基于任务的人类观察者研究来评估所提出的方法，并找到用于检测异常心肌壁运动的最佳NMSE-NSDav折衷方案。使用4D NCAT幻像，我们创建了逼真的低运动性心脏运动模型以及正常运动模型。投影数据的生成方法与上述相同，并使用3D FBP和3D OS-EM方法进行了重建，并进行了ADS校正，然后使用了4D后置滤波器的不同截止频率，以包含大范围的重建图像NMSE-NSDav权衡以进行观察者研究。具有ADS校正功能的4D MAP-RBI-EM方法也用于使用先验参数的不同组合来重建投影数据。使用用于人类观察者研究的新开发的运动图像显示应用程序，对观察者进行了训练，使其能够以逼真的实时帧速率进行动画处理，从而对多切片和多方向的门控SPECT图像进行训练，并指示他们对不存在或存在的信心进行评分连续范围的局部心肌运动缺陷的诊断。我们应用了接收机工作特性（ROC）分析，并使用ROC曲线（AUC）下的面积作为性能指标进行比较。结果表明，经过ADS校正的4D MAP-RBI-EM具有最高的AUC值，从而在测试方法中显着改善了人类观察者的检测性能，并且从优化的重建参数中获得的最佳NMSE-NSDav折衷对应于最大值每种方法的AUC值。我们发现，NMSE-NSD av折衷可以用作为每种方法选择参数值的最佳范围的有用指南，并得出结论，对图像降级因子进行校正的优化4D MAP-RBI-EM方法可提供显着效果GMP SPECT在检测壁运动异常方面的改进。

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