正则化最大期望值重建算法中β值对PET图像质量和定量分析的影响

Influence of β value on image quality and quantitative analysis of PET in the BSREM reconstruction algorithm

目的:评估正电子发射断层扫描(PET)中正则化最大期望值(BSREM)重建算法β值对图像质量和热灶定量分析的影响,探讨模体图像重建合适的β值及其对不同直径热灶定量分析的准确性。方法:采用美国国家电气制造商协会(NEMA)图像质量模体进行PET图像采集,并用BSREM算法重建图像。评估PET图像本底变异系数(CV)、靶本比(TBR)、对比噪声比(CNR),模体中直径为10 mm、13 mm、17 mm、22 mm、28 mm和37 mm的6个直径不同的空心小球、可灌注液体的热灶恢复系数(HRC)和体积恢复系数(VRC)。结果:BSREM算法重建中随β值的增大,CV值降低,而TBR和CNR升高;当β值>300时,10 mm热灶TBR呈现保持较为稳定趋势的平台期,CNR开始缓慢下降。所有热灶随β值增大,HRC下降,而VRC升高;β值为300时,直径10 mm热灶的TBR为0.48,VRC为1.34;其余5个>13 mm的热灶HRC均值为0.72(0.65~0.72);VRC均值为0.99(0.86~1.05)。结论:模体图像BSREM算法重建中的β值为300时,图像具有较好的CV、TBR和CNR,β值对不同直径热灶的HRC和VRC的定量测定存在差异性。

Objective:To assess the influence ofβvalue of reconstruction algorithm of block sequential regularized expectation maximization(BSREM)on image quality and quantitative analysis of hot sphere in positron emission tomography(PET)and to explore how to reconstruct the appropriateβvalue of the model image and the accuracy of that on quantitative analysis of hot sphere with different diameter.Methods:The phantom of image quality of American National Electrical Manufacturers Association(NEMA)was adopted to implement PET image acquisition,and BSREM algorithm was adopted to reconstruct image.The coefficient of variance(CV)of background,target-tobackground ratio(TBR),contrast noise ratio(CNR)of PET image were assessed.And hollow globules with 6 kinds of diameters included 10 mm,13 mm,17 mm,22 mm,28 mm and 37 mm in phantom,hot sphere recovery coefficient(HRC)and volume recovery coefficient(VRC)that could be perfused by fluid also were assessed.Results:In BSREM algorithm reconstruction,the CV value decreased while the TBR and CNR enhanced with the increasing ofβvalue.The TBR value of 10mm hot sphere appeared platform stage of keeping relative stable trend and CNR value started to slowly decreased whenβvalue was larger than 300.And HRC decreased but VRC increased with increasing ofβvalues of all hot sphere.TBR of hot sphere with 10 mm diameter was 0.48 and VRC of that was 1.34 whenβvalue was 300.The HRC mean of other 5 hot spheres which diameter were larger than 13mm was 0.72(0.65-0.72),and VRC mean of that was 0.99(0.86-1.05).Conclusion:In the reconstruction of BSREM algorithm of phantom image,the image has better CV,TBR and CNR whenβvalue was 300,and there is difference in the quantitative determination ofβvalue for HRC and VRC of hot sphere with different diameters.