Measuring PET Spatial Resolution Using a Cylinder Phantom Positioned at an Oblique Angle
Measuring PET Spatial Resolution Using a Cylinder Phantom Positioned at an Oblique Angle
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DOI：
10.2967/jnumed.118.209593
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发表时间：
2018-11-01
影响因子：
9.3
通讯作者：
Frey, Eric C.
中科院分区：
文献类型：
--
作者：
Lodge, Martin A.;Leal, Jeffrey P.;Frey, Eric C.
相对于 PET 扫描仪的 z 轴稍微倾斜的圆柱体模型可以对边缘扩散函数进行精细采样。我们展示了如何使用该技术来测量临床 PET 协议预期的空间分辨率，从而可能提供比通常通过已建立的实验程序获得的更相关的估计。方法：将一个直径为 20 厘米、充满水的圆柱体模型放置在与临床 PET/CT 系统的 z 轴成小角度的中心位置，其中含有均匀的 F-18 溶液。倾斜角度确保幻影边缘在不同切片中与图像矩阵的相交不同。组合多个切片的线轮廓会产生具有精细采样的复合轮廓。通过将模型拟合到径向和轴向上的精细采样边缘扩展函数，将空间分辨率测量为半高全宽 (FWHM)。通过图像重建参数的受控调制以及与具有可填充插入物的扩展模型的比较，对该技术进行了验证。使用包含 F-18、C-11、N-13、Ga-68 和 I-124 的均匀圆柱体进行单独实验来进一步评估所提出的方法。结果：高斯重建后滤波器的受控调整准确地反映在测量的 FWHM 值中。使用圆柱体 FWHM 值得出的恢复系数与在一系列插入与背景比率、体模几何形状和重建协议上从物理体模得出的恢复系数非常一致。增加正电子能量的影响清楚地反映在用不同同位素测量的半高宽值中。结论：已经开发出一种测量临床 PET 方案所实现的空间分辨率的方法，提供比通常通过既定程序获得的更相关的估计。所提出的方法不需要特殊设备并且用途广泛，能够测量不同同位素以及不同重建协议的分辨率。这项新技术有望通过更明智地选择重建参数来帮助 PET 数据采集的标准化。
A cylinder phantom positioned at a slightly oblique angle with respect to the z-axis of a PET scanner allows for fine sampling of the edge-spread function. We show how this technique can be used to measure the spatial resolution that can be expected with clinical PET protocols, potentially providing more relevant estimates than are typically obtained with established experimental procedures. Methods: A 20-cm-diameter water-filled cylinder phantom containing a uniform F-18 solution was centrally positioned at a small angle with respect to the z-axis of a clinical PET/CT system. The oblique angle ensures that the phantom edge intersects the image matrix differently in different slices. Combining line profiles from multiple slices results in a composite profile with fine sampling. Spatial resolution was measured as the full width at half maximum (FWHM) by fitting a model to the finely sampled edge-spread functions in both radial and axial directions. The technique was validated by controlled modulation of image reconstruction parameters and by comparison with extended phantoms with fillable inserts. Separate experiments with uniform cylinders containing F-18, C-11, N-13, Ga-68, and I-124 were used to further assess the proposed method. Results: Controlled adjustment of a gaussian postreconstruction filter was accurately reflected in the measured FWHM values. Recovery coefficients derived using the cylinder FWHM values agreed closely with recovery coefficients derived from physical phantoms over a range of insert-to-background ratios, phantom geometries, and reconstruction protocols. The effect of increasing positron energy was clearly reflected in the FWHM values measured with different isotopes. Conclusion: A method has been developed for measuring the spatial resolution that is achieved with clinical PET protocols, providing more relevant estimates than are typically obtained with established procedures. The proposed method requires no special equipment and is versatile, being capable of measuring resolution for different isotopes as well as for different reconstruction protocols. The new technique promises to aid standardization of PET data acquisition by allowing a more informed selection of reconstruction parameters.