Varga J, Bettinardi V, Gilardi M C, Riddell C, Castiglioni I, Rizzo G, Fazio F
University Medical School of Debrecen, Hungary.
Med Phys. 1997 Sep;24(9):1431-40. doi: 10.1118/1.598031.
In this study we evaluated pre- (PR-R) and post-reconstruction (PO-R) count-dependent Metz filters for PET brain studies in order to increase signal-to-noise ratio. A set of studies using a 3D Hoffman brain phantom was performed at various count levels, and a reference image set was created from extremely high count images. Several combinations of PR-R and PO-R filtering were considered to find the optimal means of processing, including: Hann filter alone; PR-R Metz filter without or with a PO-R low pass filter; and PO-R Metz filter without or with a PR-R low pass filter. A formula was established to correlate the optimal PO-R Metz filter order with the net counts. Resolution [full width at half-maximum (FWHM) and fill width at tenth maximum (FWTM)], normalized residual mean square differences (NRMSD) between the ideal and the processed images, noise reduction and contrast were used as parameters for the evaluation of the different filter combinations. Resolution is decreased by all filter combinations that can effectively control noise; however, FWTM increases less than FWHM. NRMSD indicates that the use of Hann and (optimal) PO-R Metz filter is the most powerful combination from among those tested. A close correlation (r = 0.969) was found between the net counts and the optimal order of the PO-R Metz filter. At the count levels of clinical studies the PO-R Metz filter was found to control noise much more effectively and enhance the contrast when compared to the routinely used Hann filter alone, and produced images of better quality.
在本研究中，我们评估了用于PET脑显像研究的重建前（PR-R）和重建后（PO-R）计数依赖型梅茨滤波器，以提高信噪比。使用3D霍夫曼脑模型在不同计数水平下进行了一组研究，并从极高计数图像创建了参考图像集。考虑了PR-R和PO-R滤波的几种组合以找到最佳处理方法，包括：单独的汉恩滤波器；不带或带有PO-R低通滤波器的PR-R梅茨滤波器；以及不带或带有PR-R低通滤波器的PO-R梅茨滤波器。建立了一个公式，将最佳PO-R梅茨滤波器阶数与净计数相关联。分辨率[半高宽（FWHM）和十分之一最大处的填充宽度（FWTM）]、理想图像与处理后图像之间的归一化残余均方根差（NRMSD）、降噪和对比度用作评估不同滤波器组合的参数。所有能有效控制噪声的滤波器组合都会降低分辨率；然而，FWTM的增加小于FWHM。NRMSD表明，在测试的组合中，使用汉恩滤波器和（最佳）PO-R梅茨滤波器是最有效的组合。发现净计数与PO-R梅茨滤波器的最佳阶数之间存在密切相关性（r = 0.969）。在临床研究的计数水平上，发现与常规单独使用的汉恩滤波器相比，PO-R梅茨滤波器能更有效地控制噪声并增强对比度，且生成的图像质量更好。
