散射对PET/CT图像空间分辨率影响的模体研究

A phantom research of the effect of scattering on spatial resolution of PET/CT image

目的:对比研究有散射和无散射两种情形下PET/CT图像空间分辨率,为PET/CT在临床的应用提供参考。方法:使用DiscoveryElite型PET/CT设备,对椭圆柱分辨率模体模拟临床有水散射和空气中无散射状态下分别行PET/CT扫描。采用VPFX-S算法,对重建滤波核2.0~10.0 mm(间隔2.0 mm)、不同重建矩阵(128×128、192×192和256×256)进行重建。以线源半高宽(FWHM)表示重建图像的空间分辨率,计算5条线源5个层面上径向、轴向FWHM,并求平均值,运用配对t检验进行统计分析。结果:①128×128矩阵时,有散射时图像空间分辨率较无散射时低4.5%~17.1%;192×192矩阵时低2.4%~8.4%;256×256矩阵时低20.8%~29.6%;②无散射状态下,当滤波核为2.0~10.0 mm(间隔2.0 mm),中心位置空间分辨率分别为(3.68±0.05)mm、(4.12±0.04)mm、(6.11±0.04)mm、(8.12±0.04)mm和(9.11±0.04)mm。结论:临床中PET/CT图像空间分辨率较空气中低,且有散射情形的图像空间分辨率随位置及重建滤波核的变化规律与无散射情形下有差异。空气中测量的PET/CT NEMA空间分辨率不能反映临床情形下的空间分辨率。

Objective:To compare and analyze the spatial resolution of positron-emission tomography/computed tomography(PET/CT)image under scattering and non-scattering so as to provide reference for the clinical application of PET/CT.Methods:Using GE discovery Elite PET/CT equipment to implement PET/CT scan for the elliptical column resolution phantom under two conditions of clinical water scattering and air(no scattering)respectively.VPFX-S algorithm was adopted to reconstruct the reconstruction filter core 2.0-10.0 mm(interval 2.0 mm)and different reconstruction matrices(128×128,192×192 and 256×256).The spatial resolution of the reconstructed image was represented by the full width at half maximum(FWHM)of the line source.The FWHM of the radial and axial directions on five levels of five lines sources were calculated,and the average value was calculated.The paired t-test was used for statistical analysis.Results:In 128×128 matrix,the spatial resolution of the image with scattering was lower of 4.5%-17.1%than that without scattering.And in 192×192 matrix,that with scattering was lower of 2.4%-8.4%than that without scattering.And in 256×256 matrix,that with scattering was lower of 20.8%-29.6%than that without scattering.Under the condition without scattering,the spatial resolution of the center position was(3.68±0.05)mm,(4.12±0.04)mm,(6.11±0.04)mm,(8.12±0.04)mm and(9.11±0.04)mm respectively when the filter core was 2.0-10.0 mm(interval 2.0 mm).Conclusion:The spatial resolution of PET/CT image in clinical situation was lower than that in air,and the change rule that spatial resolution of PET/CT image with scattering situation changed with position and reconstructed filtering core was different with that without scattering situation.The spatial resolution of PET/CT National Electrical Manufacturers Association(NEMA)that was measured in air cannot represent the spatial resolution in clinical situation.