PennPET Explorer

Principal Investigator: Joel S. Karp

PennPET Explorer Website

The PennPET Explorer is a whole-body imager that can image the major body organs simultaneously with higher sensitivity than that of commercial devices. The device is scalable in axial length and was initially tested in prototype form with 3 rings and axial field-of-view (AFOV) of 64 cm. The technology of the PennPET Explorer is based on the Philips silicon photomultiplier, and the system achieves a time-of-flight (TOF) resolution of 250 ps and a spatial resolution of 4.0 mm (FWHM) (Karp et al. 2019). We completed a series of pilot human imaging studies with each study designed to test specific capabilities of the device. We demonstrated the ability to scan for shorter duration or, alternatively with less activity, without a compromise in image quality. In clinical patients, the PennPET Explorer better delineates extent of FDG-avid disease. Delayed images, up to 10 half-lives with FDG, reveal biological insight and support the ability to track biologic processes over time. Dynamic imaging studies capture image-derived input functions for kinetic modeling applications. Additional studies with experimental research radiotracers illustrate the benefits from the combination of large axial coverage and high sensitivity. As shown in the photo below, the PennPET Explorer was expanded to 5 rings (112 cm AFOV) and installed in the Stemmler Building with an in-line CT scanner, where it was fully operational from summer 2020 to spring 2023, when the system was upgraded to include a 6th ring (resulting in a 143 cm AFOV; Dai et al. 2023). The CT was also upgraded to a Phillips IQon Spectral CT.

 

A detailed description can be found in the caption following this image.
PennPET Explorer PET/CT scanner at the University of Pennsylvania. Left: the system was previously operating with 5 rings and axial field-of-view (AFOV) of 112 cm. Right: expansion to 6 rings and AFOV of 143 cm in the back, and dual-energy spectral CT in the front.

An example of a human study imaged with FDG while the scanner was configured with 3 rings (64 cm AFOV) is shown below. The first scan, acquired at 1.5 hr post-injection. illustrates the excellent image quality – low noise with high structural detail - achieved in a short scan with a single-bed position. The second scan, acquired at 19 hr post-injection illustrates that the very high sensitivity of the PennPET Explorer enables measurement of both fast and slow kinetics and that valuable information can be extracted from the radiotracer distribution after more than 10 half-lives.

Above is a dynamic FDG study to illustrate the ability to capture fast kinetics. The movie shows FDG uptake over the 1-hour dynamic study, starting with the bolus injection, and plots the time-activity curves of the major organs.

A detailed description can be found in the caption following this image.
Patient with breast cancer imaged with 18F-fluoroglutamine radiotracer. Dynamic sequence shows uptake of radiotracer at several post-injection (p.i.) times and scan duration (2 sec - 5 min). (courtesy, Dr. Austin Pantel, U. Penn)

Depending on how the study is designed and the kinetics of the tracer, the dynamic frames can have varying durations, as shown in the 18F-fluoroglutamine study above.