Fig 1.
Schematic presentation of the simulation experiment.
Table 1.
Percent bias and coefficient of variability of mean BPND in simulated occipital cortex and thalamus voxel-wise TACs as a function of simulated noise and application of FA.
Fig 2.
Recovery (%) (vertical axis) of voxels, in which a difference in radiotracer binding was simulated, plotted against the level of simulated noise (horizontal axis) and the simulated difference in simulated parameters between the groups of scans (represented by different colors).
Continuous lines represent recovery from FA-denoised images while dashed lines represent raw-image derived recovery. Two subplots (a-b) correspond to the different quantification approaches. (c) An axial slice of a parametric image of T-values derived from SPM analysis of difference of binding of two groups of parametric images produced after voxel-wise application of SRTM for a low- (α = 10) and high- noise (α = 20) level as compared in raw and FA-denoised images. Note that FA-denoising leads not only to an increase in recovery of simulated voxels but in an increase in T-values associated with the recovered voxels.
Fig 3.
Average TACs over the voxels in the occipital and thalamic VOI, extracted from raw (RAW-Occ and RAW-Thal respectively) and FA-denoised (FA2c-Occ and FA2c-Thal, respectively) simulated images.
The same TACs are shown for all four levels of noise simulation in comparison to corresponding TACs from the simulated, un-noised dynamic image (SIMUL-Occ and SIMUL-Thal). FA application does not induce any considerable bias in voxel-wise kinetics and markedly diminishes its variability.
Fig 4.
Average percent normalized residuals between the true simulated and FA-denoised dynamic simulated image TACs for all time-frames and for the four levels of noise (marked with different colors).
Fig 5.
Parametric BPND (ml/ml) and CV (%) values of binding parameters obtained from voxel-wise quantification using SRTM and LNIGA on an axial slice on a [123I]IMZ SPECT image from one participant of the study.
Denoising with FA gives equal, if not superior quality parametric images of BPND while markedly diminishes its variability.
Fig 6.
Parametric BPND (ml/ml) and CV values of binding parameters obtained from voxel-wise quantification using SRTM and LNIGA on an axial slice on a [11C]FMZ PET image from one participant of the study.
As with SPECT images of Fig 5, denoising with FA gives equal, if not superior quality parametric images of BPND while markedly diminishes its variability.