Fig 1. Noise in PET/CT images at different exposures.

Shown are examples of four differently exposed HR FBP (a) and UHR PSF (b) images, using the daily QA phantom. Images are maximum intensity projections (MIPs) in the axial direction of the PET system with black set to naught and white set to the maximal intensity found in the PET image. The green rectangle marks the VOI, where all the calculations were performed. The associated noise histograms of the HR FBP (c) and UHR PSF (d) measurements are depicted below, showing the measured AC distribution in the VOI after four different acquisition durations. N_voxel denotes the number of analyzed voxels in the VOI. Black insets are magnified histograms of the longest acquisition. Color legend of acquisition durations applies to both (c) and (d).