SUV/Patlak-4D whole-body PET/CT dynamic and parametric imaging: clinical demonstration and validation of SUV synthesis from dynamic passes

Abstract

Whole-body (WB) PET/CT imaging currently involves single-frame, i.e., static, PET acquisitions over a set of axial bed positions to form standardized uptake value (SUV) images. However, SUV is considered semi-quantitative due to its dependence on post-injection scan time and subject physiology. Recently, we introduced a class of novel WB dynamic PET/CT scan protocols capable of acquiring PET data over multiple time frames at each bed to enable quantitative WB parametric PET imaging. In this study, we are validating a special dynamic WB 18F-FDG PET/CT framework supporting synthesis of staticequivalent SUV as well as dynamic and parametric Patlak WB images from a single set of WB passes acquired within the standard-of-care post-injection time window of 18F-FDG PET/CT exams. The proposed protocol, streamlined for wide clinical adoption, consists of four unidirectional WB passes of constant bed frames (30 sec) or equivalent bed speeds, beginning 1h after injection. The acquired data at each bed may later be used by a direct 4D Patlak reconstruction algorithm to obtain parametric WB Ki images after utilizing a populationbased model to infer the missing first 1h of the input function. Moreover, the same data can be added at each bed to synthesize static PET frames and equivalent SUV WB PET images. For the clinical evaluation of the proposed method, we consented patients scheduled for their regular WB 18F-FDG PET/CT exam to undergo afterwards a second PET-only scan, for the same total scan time, using our protocol. SUV mean comparisons at focal uptake ROIs between the step-and-shoot (S&S) static SUV and the respective synthetic SUV images yielded <14% and <20%.differences, primarily attributed to post-smoothing, when synthesis was conducted on S&S and continuous bed motion scan modes respectively. In addition, the direct 4D Patlak Ki WB images exhibited similar noise levels, while offering similar or better lesion contrast and enhanced quantification relative to SUV.