  Standard Patlak plot is widely used to describe FDG kinetics for dynamic PET
imaging. Whole-body Patlak parametric imaging remains constrained due to the
need for a full-time input function. Here, we demonstrate the Relative Patlak
(RP) plot, which eliminates the need for the early-time input function, for
total-body parametric imaging and its application to clinical 20-min scan
acquired in list-mode. We demonstrated that the RP intercept b' is equivalent
to a ratio of standardized uptake value relative to the blood, while the RP
slope Ki' is equal to the standard Patlak Ki multiplied by a global scaling
factor for each subject. One challenge in applying RP to a short scan duration
(20 min) is the high noise in parametric images. We applied a deep kernel
method for noise reduction. Using the standard Patlak plot as the reference,
the RP method was evaluated for lesion quantification, lesion-to-background
contrast, and myocardial visualization in total-body parametric imaging with
uEXPLORER in 22 human subjects who underwent a 1-h dynamic 18F-FDG scan. The RP
method was also applied to the dynamic data regenerated from a clinical
standard 20-min scan either at 1-h or 2-h post-injection for two cancer
patients. We demonstrated that it is feasible to obtain high-quality parametric
images from 20-min dynamic scans using the RP plot with a self-supervised
deep-kernel noise reduction strategy. The RP Ki' highly correlated with Ki in
lesions and major organs, demonstrating its quantitative potential across
subjects. Compared to conventional SUVs, the Ki' images significantly improved
lesion contrast and enabled visualization of the myocardium for potential
cardiac assessment. The application of RP parametric imaging to two clinical
scans also showed similar benefits. Total-body PET with the RP plot is feasible
to generate parametric images from the dynamic data of a 20-min clinical scan.
