Quantitation of dynamic total-body PET imaging: recent developments and future perspectives

Abstract

Background: Positron emission tomography (PET) scanning is an important diagnostic imaging technique used in disease diagnosis, therapy planning, treatment monitoring, and medical research. The standardized uptake value (SUV) obtained at a single time frame has been widely employed in clinical practice. Well beyond this simple static measure, more detailed metabolic information can be recovered from dynamic PET scans, followed by the recovery of arterial input function and application of appropriate tracer kinetic models. Many efforts have been devoted to the development of quantitative techniques over the last couple of decades.

Challenges: The advent of new-generation total-body PET scanners characterized by ultra-high sensitivity and long axial field of view, i.e., uEXPLORER (United Imaging Healthcare), PennPET Explorer (University of Pennsylvania), and Biograph Vision Quadra (Siemens Healthineers), further stimulates valuable inspiration to derive kinetics for multiple organs simultaneously. But some emerging issues also need to be addressed, e.g., the large-scale data size and organ-specific physiology. The direct implementation of classical methods for total-body PET imaging without proper validation may lead to less accurate results.

Conclusions: In this contribution, the published dynamic total-body PET datasets are outlined, and several challenges/opportunities for quantitation of such types of studies are presented. An overview of the basic equation, calculation of input function (based on blood sampling, image, population or mathematical model), and kinetic analysis encompassing parametric (compartmental model, graphical plot and spectral analysis) and non-parametric (B-spline and piece-wise basis elements) approaches is provided. The discussion mainly focuses on the feasibilities, recent developments, and future perspectives of these methodologies for a diverse-tissue environment.

Keywords: Arterial input function; Kinetic models; Multiple organs; Parametric imaging; Total-body PET.

Fig. 1

The number of publications (left y-axis) on the total-body (TB) PET studies (blue) and dynamic TB scanning with the implementation of kinetic analysis (red) for the period from 2019 to 2022. The percentage (right y-axis) of publications relevant to the kinetic model in TB PET is shown as the black line. The data were collected from a search on PubMed on 08/05/2023

Fig. 2

Overview of dynamic PET quantitation. Abbreviations: PET, positron emission tomography; IDIF, image-derived input function; PBIF, population-based input function; ROI, region of interest; FA, factor analysis; SVD, singular value decomposition; PCA, principal component analysis; MA, mixture analysis