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Table 1 The percentage increase/decrease for different parameters comparing 8 TOF BSREM reconstructions with reference TOF OSEM reconstructions

From: Quantitative performance and optimal regularization parameter in block sequential regularized expectation maximization reconstructions in clinical 68Ga-PSMA PET/MR

  TOF BSREM
β = 300 β = 350 β = 400 β = 450 β = 500 β = 550 β = 600 β = 700
Background SUVmean 0.0% (0.60) 0.0% (0.63) 0.0% (0.65) 0.1% (0.69) 0.1% (0.67) 0.1% (0.69) 0.1% (0.75) 0.1% (0.87)
Background SUVstd 22.0% (< 0.01) H 8.3% (< 0.01) H −1.0% (0.41) − 9.2% (< 0.01) L − 15.2% (< 0.01) L −18.4% (< 0.01) L − 21.0% (< 0.01) L −27.0% (< 0.01) L
Small size, low-uptake lesions (N = 8) SUVmax 28.0% (0.02) H 17.7% (0.15) 8.0% (0.55) −1.6% (0.74) − 8.1% (0.25) −12.8% (0.11) − 18.1% (0.05) L − 24.6% (0.02) L
CR 32.4% (0.02) H 20.2% (0.15) 8.1% (0.55) − 2.8% (0.74) −10.0% (0.15) −15.4% (0.08) − 21.6% (0.05) L − 29.3% (0.02) L
Medium size, medium uptake lesions (N = 15) SUVmax 27.0% (< 0.01) H 18.6% (< 0.01) H 14.5% (0.01) H 10.5% (0.08) − 0.4% (0.64) − 3.3% (0.42) − 5.8% (0.21) − 10.6% (< 0.01) L
CR 28.2% (< 0.01) H 20.4% (< 0.01) H 15.6% (0.02) H 8.8% (0.15) 0.1% (0.89) − 2.9% (0.42) − 5.5% (0.06) −12.4% (< 0.01) L
Large size, high-uptake lesions (N = 17) SUVmax 16.3% (< 0.01) H 11.5% (< 0.01) H 7.0% (< 0.01) H 4.1% (0.01) H 1.8% (0.19) 0.3% (0.43) − 1.7% (0.89) − 4.9% (0.03) L
CR 17.4% (< 0.01) H 12.5% (< 0.01) H 9.1% (< 0.01) H 6.2% (< 0.01) H 2.9% (0.08) 0.2% (0.46) − 1.9% (0.71) − 5.2% (0.02) L
  1. The regularization parameter applied in TOF BSREM is indicated by the β value (top). P values are listed in parentheses. H indicates significantly higher values, and L indicates significantly lower parameter values for TOF BSREM compared to reference TOF OSEM with 28 subsets and 2 iterations SUV standardized uptake value, SUVmax the average of the hottest 5 voxels in the lesion, CR the percentage increase of the tumor to background ratio of the indicated reconstruction compared to the reference TOF OSEM reconstruction with 2 iterations and 28 subsets, TOF time-of-flight, OSEM ordered subset expectation maximization, BSREM block sequential regularized expectation maximization