Lesion detectability and quantification in PET/CT oncological studies by Monte Carlo simulations

The aim of this work was to assess lesion detectability and quantification in whole body oncological 18F-FDG studies performed by a state-of-the-art integrated Positron Emission Tomograph/computed tomography (PET/CT) system. Lesion detectability and quantification were assessed by a Monte Carlo (MC) simulation approach as a function of different physical factors (e.g., attenuation and scatter), image counting statistics, lesion size and position, lesion-to-background radioactivity concentration ratio (L/B), and reconstruction algorithms. The results of this work brought to a number of conclusions. ¿ The MC code PET-electron gamma shower (EGS) was accurate in simulating the physical response of the considered PET/CT scanner (90%). ¿ PET-EGS and patient-derived phantoms can be used in simulating18 F-FDG PET oncological studies. ¿ Counting statistics is a dominant factor in lesion detectability. ¿ Correction for scatter (from both inside and outside the field of view) is needed to improve lesion detectability. ¿ Iterative reconstruction and attenuation correction must be used to interpret clinical images. ¿ Re-binning algorithms are appropriate for whole-body oncological data. ¿ A MC-based method for correction of partial volume effect is feasible. For the considered PET/CT system, limits in lesion detectability were determined in situations comparable to those of real oncological studies: at a L B = 3 for lesions of 12 mm diameter and at a L B = 4 for lesions of 8 mm diameter.