两种Ramp滤波函数重建SPECT图像的比较

A comparison of two kinds of Ramp filters function in the reconstruction image of SPECT

目的 :比较普通 Ramp滤波函数与定量分析型Ramp滤波函数重建单光子发射计算机断层摄影 (SPECT)图像的差异 ,为正确选择重建滤波函数提供依据 .方法 :采用一个部分空心部分含有不同孔径冷区的圆柱体模型 ,内充 99Tcm 做 36 0° SPECT采集 ,分别用上述两种滤波函数以滤波反投影法重建横断面图像 .测量断面的平均计数、噪声、冷区对比度及剖面曲线 .结果 :与普通的 Ramp滤波函数相比 ,定量分析型所重建的图像平均计数提高约 5 0 % ,噪声降低约 30 % .但对比度大为降低 .后者重建图像的计数值更接近实际值 .结论 :SPECT仅做定性分析时可用普通Ramp滤波函数以获得对比度较高的重建图像 ;当用于定量半定量分析时 。

Aim:An ordinary Ram p filter and a quantitative Ramp filter were compared in the reconstruction of single- photon em ission- com puted tomography (SPECT ) . Methods:A phantom with a hollow space and som e cold spots filled with 99Tcm was imaged by a SPECT for 36 0°. Two kinds of Ramp filters were used to reconstruct transverse slices. The mean counts,noise,contrast and profile curves of the slices were measured. Results: Compared to the ordinary Ram p filter,with the quantitative Ramp filter,the mean counts of the slice increased about50 % . In the mean while the noise decreased about 30 % . But the contrast was also decreased largely. The relative counts in different parts and the value of counts are more acceptable for quantitative Ramp filter.Conclusion:In the case of qualitative analysis of SPECT,ordinary Ramp filter is better used to achieve higher contrast. When doing quantitative analysis,the quantitative Ramp filter should be adopted so as to acquire more accurate results