Optimization of the relative acquisition duration for PET/CT imaging in oncology

In optimizing the PET acquisition in FDG PET/CT imaging there are a number of variables to be considered, such as the injected dose. Noise equivalent count rates (NECR) measured using the NEMA 2001 NU2 standard relate activity concentrations to peak achievable NECR. The optimal dose will generally vary both from NEMA and from patient to patient. However precise uptake times may not always be achievable in practice and the optimum dose for the individual bed positions may not generally be optimized simultaneously. Furthermore differences remain in the maximum achievable NECR for patients of different weights, assuming a common acquisition duration. One possibility to further achieve uniformity of image quality is to adopt different imaging durations, both in terms of the total imaging time for different patients and also for different acquired bed positions within each patient. Modeling the dependence of the clinical count rates on patient weight and axial anatomical locations leads to predicted optimized imaging times for equalizing the NECR. To equalize image quality, defined for this purpose as equalizing the signal to noise ratio in relatively homogeneous regions such as the liver, spleen and vertebral marrow, these imaging times are further corrected to account for variations in the absolute activity concentration which approximately correlates with the lean body mass