| Objective To investigate the influences of TOF,PSF and GF on the standardized uptake value (SUV)and signal to noise ratio(SNR)of pulmonary nodules,and to provide the best PET reconstruction algorithm for patients with pulmonary nodules.Materials and Methods The PET/CT images of 38 patients(25 males,13 females,37~82(61.23±11.66)years)who underwent full-body 18F-FDG PET/CT examination in the First Affiliated Hospital of Anhui Medical University from December 2020 to March 2022 were retrospectively analyzed.Images were reconstructed using the filtered back projection(FBP),ordered subset expectation maximization(OSEM),OSEM+TOF,OSEM+PSF,OSEM+TOF+PSF,and OSEM+TOF+PSF+GF reconstruction algorithms,where full width at half maximum(FWHM)of GF in the OSEM+TOF+PSF+GF reconstruction algorithm was 2mm,4mm,6mm,8mm,and 10 mm respectively.The SNR and SUV of pulmonary nodules were analyzed by semi-quantitative method and visual assessment of PET image quality.Holm-Sidak test was used to analyze the SUV differences among different reconstruction algorithms and Friedman test was used to analyze the SNR differences among different reconstruction algorithms.Results Compared with OSEM group,SUV max,SUV peak and SUV mean in FBP group were increased by 5.15%(P>0.05),11.85%(P<0.0001)and 14.08%(P<0.0001),SNR decreased by 292.35%(P<0.01);In OSEM+TOF group,SUV max,SUV peak,SUV mean and SNR increased by 14.62%,13.68%,18.62% and 16.46%(all P<0.05);In OSEM+PSF group,SUV max decreased by 12.54%,while SUV peak,SUV mean and SNR increased by 5.10%,3.41% and 44.23%(all P<0.001);In OSEM+TOF+PSF group,SUV max,SUV peak,SUV mean and SNR were increased by 12.20%,20.38%,27.83%and 50.27%(all P<0.01).Compared with OSEM+TOF+PSF group,SUV max,SUV peak and SUV mean in OSEM+TOF+PSF+GF(2mm FWHM)group were decreased by 12.12%,52.05% and9.24%,and SNR was increased by 3.42%(all P<0.05),SUV max,SUV peak and SUV mean in OSEM+TOF+PSF+GF(4mm FWHM)group decreased by 56.67%,69.79%and 34.75%,and SNR increased by 10.10%(all P<0.05),SUV max,SUV peak,SUV mean and SNR in OSEM+TOF+PSF+GF(6mm FWHM)group decreased by 115.91%,99.10%,73.63% and 1.75%(all P<0.05),SUV max,SUV peak,SUV mean and SNR in OSEM+TOF+PSF+GF(8mm FWHM)group decreased by 198.38%,140.65%,126.04% and 18.68%(all P<0.05),SUV max,SUV peak,SUV mean and SNR in OSEM+TOF+PSF+GF(10mm FWHM)group were decreased by 311.94%,198.99%,201.85% and 60.47%(all P<0.05).The mean excellent rate of FBP,OSEM,OSEM+TOF,OSEM+PSF and OSEM+TOF+PSF reconstruction algorithms for PET image visual score of pulmonary nodules was 0,11.63%,25.58%,18.60% and 50.00%.OSEM+TOF+PSF+GF(FWHM of GF was 2mm,4mm,6mm,8mm and 10mm)showed average excellence rates of 51.16%,54.65%,54.65%,33.72% and 10.47% for PET image visual score of pulmonary nodules.Under the condition of OSEM reconstruction,the SUV max and SNR in the larger nodules group were increased by 69.92% and 120.98% compared with the smaller nodules group(all P < 0.05),and the SUV max and SNR in the overweight or obese group were increased by 3.89% and 21.46% compared with the lean or normal groups(all P > 0.05).Under the reconstruction condition of OSEM+TOF+PSF+GF(the half height and width of GF was 4mm),the SUV max and SNR in the larger nodules group were increased by 19.58% and 33.05% compared with that in the smaller nodules group(both P > 0.05).In overweight or obese groups,SUV max was increased by 1.65%(P >0.05)compared with lean or normal groups,while SNR was decreased by 9.56%(P >0.05).Conclusion Among all reconstruction algorithms,OSEM+TOF+PSF+GF(4mm FWHM)reconstruction algorithm can obtain the best PET image visual score and SNR of pulmonary nodules,but reduce the SUV of pulmonary nodules.It can significantly improve the detection rate of pulmonary malignant nodules and improve the detection performance of PET/CT.There was no significant change in SNR of pulmonary nodules in overweight or obese group(BMI≥25 group). |
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