块序正则化最大期望值重建算法β值对前列腺癌Al18F-PSMA-11 PET/CT图像质量及半定量参数准确性的影响OA

Objective:To investigate the effect of different β values of the Block Sequential Regularized Expectation Maximization(BSREM)algorithm on the image quality parameters and semi-quantitative parameters of[18F]aluminum fluoride-prostate-specific membrane antigen-11(Al18F-PSMA-11)PET/CT,and to screen out the optimal reconstruction βvalue for this imaging agent.Methods:A retrospective study was conducted on 23 patients pathologically diagnosed with prostate cancer who underwent Al18F-PSMA-11 PET/CT examination at Tianjin Medical University Cancer Institute and Hospital from July 2022 to November 2023,with a total of 56 lesions enrolled.All images were reconstructed using the Ordered Subsets Expectation Maximization(OSEM)algorithm and the BSREM algorithm respectively.For the BSREM algorithm,the β values were set as a gradient series of 100,200,300,400,500,600,700,800,900 and 1000.Two senior radiologists performed double-blind visual quality scoring of all images.The image noise(Noise),signal-to-noise ratio(SNR),signal-to-background ratio(SBR)and maximum standardized uptake value(SUVmax)were measured after reconstruction with the two algorithms.The variations of Noise,SNR,SBR and SUVmax with β values ranging from 100 to 1000 were analyzed,and combined with the results of visual analysis,the effect of β values in BSREM reconstruction on the image quality and semi-quantitative parameters of Al18F-PSMA-11 PET/CT was evaluated.Results:In 23 patients,the overall noise level decreased with increasing β values(Q=227.13,P<0.001),while the noise levels at β100 and β200 were higher than those reconstructed by OSEM(Z=-4.20,-2.54,P<0.05).The signal-to-noise ratio(SNR)of all lesions showed an overall increasing trend with rising β values(Q=305.33,P<0.05).At β100,the SNR did not differ statistically from OSEM reconstruction(P＞0.05).Between β200 and β1000,the SNR was higher than that reconstructed by OSEM(Z=-2.446,-3.920,-5.839,-6.089,-6.464,-6.446,-6.196,-5.562,-5.821,P<0.05).Between adjacent values at β600 and β1000,the SNR did not differ statistically(P＞0.05),indicating a plateau in SNR.The SBR of all lesions gradually decreased with increasing β values.At β600,the SBR showed no difference from OSEM-reconstructed SBR(P＞0.05).Between β700 and β1000,the SBR was lower than OSEM-reconstructed SBR(Z=-1.098,-2.196,-3.250,-4.321,P<0.05).There was no statistically significant difference in SBR between adjacent values within β700 to β1 000(P＞0.05),and SBR tended to stabilize.The SUVmax gradually decreased with increasing β values(Q=529.99,P<0.001).Between β100 and β500,the SUVmax was higher than OSEM-reconstructed(Z=-5.607,-4.714,-3.589,-2.625,-1.357,P<0.05).At β600 and β700,the SUVmax showed no statistically significant difference compared to OSEM-reconstructed(P＞0.05).Between β800 and β1 000,the SUVmax was lower than OSEM-reconstructed(Z=-2.107,-3.188,-4.268,P<0.05).Visual assessment results indicated that image quality at β100 to β300,β900,and β1000 was inferior to OSEM-reconstructed,while β400 and β800 were comparable to OSEM-reconstructed.Image quality at β500 to β700 was significantly superior to OSEM-reconstructed.Conclusion:The β value of BSREM reconstruction has significant impact on the Noise,SNR,SBR and SUVmax of Al18F-PSMA-11 PET/CT images,which can affect the quality of image and the diagnostic level.It is recommended that β=600 is selected as the optimal reconstruction β value.