Total-Body PET: Maximizing Sensitivity to Create New Opportunities for Clinical Research and Patient Care

Abstract

PET is widely considered the most sensitive technique available for noninvasively studying physiology, metabolism, and molecular pathways in the living human being. However, the utility of PET, being a photon-deficient modality, remains constrained by factors including low signal-to-noise ratio, long imaging times, and concerns about radiation dose. Two developments offer the potential to dramatically increase the effective sensitivity of PET. First by increasing the geometric coverage to encompass the entire body, sensitivity can be increased by a factor of about 40 for total-body imaging or a factor of about 4-5 for imaging a single organ such as the brain or heart. The world's first total-body PET/CT scanner is currently under construction to demonstrate how this step change in sensitivity affects the way PET is used both in clinical research and in patient care. Second, there is the future prospect of significant improvements in timing resolution that could lead to further effective sensitivity gains. When combined with total-body PET, this could produce overall sensitivity gains of more than 2 orders of magnitude compared with existing state-of-the-art systems. In this article, we discuss the benefits of increasing body coverage, describe our efforts to develop a first-generation total-body PET/CT scanner, discuss selected application areas for total-body PET, and project the impact of further improvements in time-of-flight PET.

Keywords: PET; PET/CT; instrumentation; molecular imaging; total-body imaging.

FIGURE 1.

Whole-body PET (A) vs. total-body PET (B). (Reprinted with permission of (31).)

FIGURE 2.

Photograph of EXPLORER mock-up installed at University of California Davis Medical Center.

FIGURE 3.

Design drawing for EXPLORER PET/CT scanner. (Courtesy of United Imaging Healthcare.)

FIGURE 4.

Photograph of mini EXPLORER scanner (left) and maximum-intensity-projection images of 2 frames from dynamic total-body imaging study after injection of 8.5 MBq of ¹⁸F-FDG (¹/₁₀ standard activity) in 4.6-kg rhesus macaque (right).

FIGURE 5.

Localization through time-of-flight PET showing effect of improving timing resolution. Better timing resolution translates into higher effective sensitivity due to improved localization of each event.