Fig. 6
From: Simultaneous emission and attenuation reconstruction in time-of-flight PET using a reference object
Mean percentage difference for soft tissue as a function of the number of iterations obtained for reference object with several activity concentrations (a), materials (b), and number of cylinders (c), and for different CRTs (d). All other options were set as in the reference configuration (CRT = 300 ps, 107 coincidences and reference object as one water cylinder with A0 activity). All pixels of the attenuation image except for the patient table were updated during the reconstruction