Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
J Nucl Med. 2011 Oct;52(10):1646-53. doi: 10.2967/jnumed.110.087114. Epub 2011 Aug 17.
Several commercial small-animal SPECT scanners using multipinhole collimation are presently available. However, generally accepted standards to characterize the performance of these scanners do not exist. Whereas for small-animal PET, the National Electrical Manufacturers Association (NEMA) NU 4 standards have been defined in 2008, such standards are still lacking for small-animal SPECT. In this study, the image quality parameters associated with the NEMA NU 4 image quality phantom were determined for a small-animal multipinhole SPECT scanner.
Multiple whole-body scans of the NEMA NU 4 image quality phantom of 1-h duration were performed in a U-SPECT-II scanner using (99m)Tc with activities ranging between 8.4 and 78.2 MBq. The collimator contained 75 pinholes of 1.0-mm diameter and had a bore diameter of 98 mm. Image quality parameters were determined as a function of average phantom activity, number of iterations, postreconstruction spatial filter, and scatter correction. In addition, a mouse was injected with (99m)Tc-hydroxymethylene diphosphonate and was euthanized 6.5 h after injection. Multiple whole-body scans of this mouse of 1-h duration were acquired for activities ranging between 3.29 and 52.7 MBq.
An increase in the number of iterations was accompanied by an increase in the recovery coefficients for the small rods (RC(rod)), an increase in the noise in the uniform phantom region, and a decrease in spillover ratios for the cold-air- and water-filled scatter compartments (SOR(air) and SOR(wat)). Application of spatial filtering reduced image noise but lowered RC(rod). Filtering did not influence SOR(air) and SOR(wat). Scatter correction reduced SOR(air) and SOR(wat). The effect of total phantom activity was primarily seen in a reduction of image noise with increasing activity. RC(rod), SOR(air), and SOR(wat) were more or less constant as a function of phantom activity. The relation between acquisition and reconstruction settings and image quality was confirmed in the (99m)Tc-hydroxymethylene diphosphonate mouse scans.
Although developed for small-animal PET, the NEMA NU 4 image quality phantom was found to be useful for small-animal SPECT as well, allowing for objective determination of image quality parameters and showing the trade-offs between several of these parameters on variation of acquisition and reconstruction settings.
目前有几种使用多针孔准直器的商用小动物 SPECT 扫描仪。然而，目前还没有普遍接受的标准来描述这些扫描仪的性能。虽然对于小动物 PET，2008 年已经定义了美国电器制造商协会（NEMA）的 NU 4 标准，但对于小动物 SPECT，仍然缺乏这样的标准。在这项研究中，我们确定了一种小动物多针孔 SPECT 扫描仪与 NEMA NU 4 图像质量体模相关的图像质量参数。
在 U-SPECT-II 扫描仪中，使用（99m）Tc 进行了长达 1 小时的 NEMA NU 4 图像质量体模的多次全身扫描，其活度范围在 8.4 到 78.2MBq 之间。准直器包含 75 个直径为 1.0mm 的针孔，其孔径为 98mm。图像质量参数是作为平均体模活度、迭代次数、后重建空间滤波器和散射校正的函数来确定的。此外，用（99m）Tc-羟甲基二膦酸盐注射一只老鼠，在注射后 6.5 小时将其安乐死。对这只老鼠进行了长达 1 小时的多次全身扫描，其活度范围在 3.29 到 52.7MBq 之间。
随着迭代次数的增加，小棒的回收系数（RC（rod））增加，均匀体模区域的噪声增加，冷空气和水填充散射室的溢出比（SOR（air）和 SOR（wat））降低。应用空间滤波降低了图像噪声，但降低了 RC（rod）。滤波对 SOR（air）和 SOR（wat）没有影响。散射校正降低了 SOR（air）和 SOR（wat）。总体模活度的影响主要表现为随着活度的增加而降低图像噪声。RC（rod）、SOR（air）和 SOR（wat）几乎是随着体模活度的变化而保持不变。在（99m）Tc-羟甲基二膦酸盐鼠扫描中证实了采集和重建设置与图像质量之间的关系。
尽管是为小动物 PET 开发的，但 NEMA NU 4 图像质量体模也被发现对小动物 SPECT 有用，允许客观地确定图像质量参数，并显示在采集和重建设置变化时这些参数之间的权衡。
