Impact of different reconstruction algorithms and ordered subset expectation maximization reconstruction parameters on quantitative results in SPECT/CT / 中国医学影像技术

ABSTRACT

Objective To evaluate the impact of 3-dimensional ordered subset expectation maximization (3D-OSEM),2-dimensional ordered subset expectation maximization (2D-OSEM),filtered-back projection (FBP),and the number of OSEM iterations and subsets on quantitative results in SPECT/CT.Methods A Jaszczak cylindrical phantom and NEMA/IEC body phantom were performed in routine SPECT/CT using CT attenuation correction,scatter correction and 3D-OSEM reconstructed image.The system volume sensitivity (cpm/kBq) was acquired from the reconstructed image of Jaszczak phantom,and the absolute activity concentration (kBq/ml) of the hot sphere from IEC phantom was calculated and compared with true activity concentration,then quantitative error was calculated.With changing the reconstruction algorithm (2D-OSEM,FBP) and OSEM reconstruction parameters (number of iterations and subsets) to reconstruct the IEC phantom,the differences of quantitative results from different reconstruction algorithms and OSEM iterations and subsets were compared.Results When reconstructing images with 3D-OSEM,2D-OSEM and FBP,the quantitative error of each sphere increased with the decrease of the spherical volume (r=-0.831,-0.831,-0.826,all P＜0.05).The quantitative error of different volume spheres among three reconstruction algorithms was statistically significant (F=8.850,P＜0.05).Among them,the result of 3D-OSEM was less than that of 2D-OS EM (P＜0.05),and of 2D-OSEM was less than of FBP (P＜0.05).The quantitative error of different volume spheres decreased with the increasing of number of iterations (r=-0.721,-0.681,-0.691,-0.711,-0.845,-0.893,all P＜0.05) and decreased with the increase of number of subsets (r=-0.670,-0.694,-0.717,-0.852,-0.956,-0.998,all P＜0.05).Conclusion The quantitative accuracy of 3D-OSEM reconstruction based on CT attenuation correction and scattering correction is significantly better than that of 2D-OSEM and FBP.Choosing the appropriate OSEM reconstruction parameters is helpful to improve the quantification accuracy in SPECT/CT.