Evaluating Reconstruction Parameter for Improving Quantitative Accuracy in PET
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Purpose: This work evaluates the effect of Point Spread Function (PSF) reconstruction and post-processing parameters on quantitative accuracy in Jaszczak© phantom (Data Spectrum Corporation).
Methods: The phantom was prepared with diluted F-18 to emulate a 15 mCi of patient [ACR. Phantom Testing: PET (Rev 11-30-2020)]. Acquisition was done in a Siemens Biograph 6 Truepoint PET/CT scanner with the whole body protocol. A TrueX© PSF was used to reconstruct the Sinogram using Iterations (Gaussian filter FWHM): 2 (4mm), 4 (4, 6, 8 mm) and 8 (4, 6, 8 mm) at 14 subsets. Percentage difference of measured maximum SUV obtained by drawing regions of interest on hot cylinders (8, 12, 16 and 25 mm diameter) and theoretical SUV (injected activity concentration in cylinder/input patient activity concentration) were evaluated.
Results: Smallest SUV errors were observed for largest cylinder at lower iterations (25mm: 8i: 18%, 2i: 0.2%) and for smaller cylinders at higher iterations (16 mm: 8i: 6.5%, 2i: 19%; 12 mm: 8i: 8%, 2i: 34%; 8 mm: 8i: 37%, 2i: 49%). At higher iterations (8i), increasing the filter smoothing (4mm to 6mm) increased accuracy for larger cylinder (0.04%) but not for smaller cylinders (45%, 25% and 10% for 8, 12 and 16 mm cylinders respectively). Marginal increase in number of iteration (4i, 4mm FWHM) improved accuracy for smaller cylinders while partially reducing the accuracy for larger cylinder (25 mm: 5%, 16 mm: 5%, 12 mm: 18%, 8 mm: 37%).
Conclusion: The measured SUV was more accurate for larger cylinders than smaller cylinders because of increased count loss due to partial volume effect. Increasing iterations improved accuracy for smaller cylinders because of better resolution convergence but introduced noise in larger cylinders. Smoothing reduced that noise but increased count loss in smaller cylinders. Marginal increase in iterations without increase of smoothing provided a workable compromise.
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