RT Journal Article
SR Electronic
T1 Feasibility of whole body dynamic quantification using ultra-fast digital photon counting PET/CT
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1245
OP 1245
VO 59
IS supplement 1
A1 Katherine Binzel
A1 Melissa Magyer
A1 Richard Moore
A1 Michael Friel
A1 Maria Menendez
A1 Jun Zhang
A1 Michael Knopp
YR 2018
UL http://jnm.snmjournals.org/content/59/supplement_1/1245.abstract
AB 1245Objectives: Next-generation digital photon counting PET/CT systems enable ultra-fast PET acquisition times through improvements in system spatial resolution and sensitivity. We have previously explored the use of 9 second per bed acquisitions for clinical applications enabled by optimized reconstruction. We have then applied these short acquisition times to a whole body dynamic protocol, where imaging from the time of injection can cover multiple bed positions in rapid succession, giving new insight into tissue perfusion and uptake characteristics. We assessed the feasibility of quantification based on this whole body dynamic acquisition methodology in a preclinical setting. Methods: Four healthy, adult male beagles were imaged for this initial study. With an average weight of 13.4 kg, the animals were injected with an average dose of 3.3 mCi 18F-FDG. Imaging began at the time of injection and covered 6 bed positions, acquiring 12 seconds per bed position for 15 consecutive whole body sweeps, until 35 minutes post-injection. All imaging was performed on a digital photon counting system (Philips Vereos, pre-commercial release). PET listmode data were reconstructed using a 576x576 matrix with a 1mm isometric voxel size, using both point spread function and Gaussian filtering. Three iterations each with 7 subsets were used for reconstructions evaluated in this study. 3D regions of interest were placed over the cerebellum, myocardium, a portion of the liver, kidney, and muscle, recording SUVmean and SUVmax for each of the 15 acquisitions. Blinded review by three readers was performed to assess image quality. Results: Whole body dynamic acquisitions were readily feasible, resulting in excellent image quality as scored during blinded review, even when using a large reconstruction matrix for 1mm voxel volumes. Quantitative assessment provided detailed insight into tissue perfusion characteristics which was very robust across all subjects. With the exception of the kidneys, nearly identical curves were observed in each region assessed. In the liver, an initial perfusion peak was seen during the 2nd whole body sweep with an average SUVmean of 4.4 (range 3.7-5.3) followed by a gradual decrease in activity thereafter. Immediate, yet gradual FDG uptake in the cerebellum reached an average SUVmean of 3.0 (range 2.5-3.3) by the 15th acquisition. In the heart, the SUVmean was high, averaging 5.9 (range 4.8-7.4) on the first acquisition as the bolus passed through in the vascular phase. The 2nd acquisition showed much lower activity, averaging 3.0 increasing to only 3.1 on the last acquisition, as the myocardium itself took up a minimal amount of the FDG over time. The muscle tissue showed nearly no uptake throughout the entire acquisition time, the average SUVmean at 35 minutes post-injection was 0.37 (range 0.31-0.45). We attribute the consistency of uptake and perfusion curves to the identical lifestyles of the 4 age matched canines. Conclusion: Next-generation digital PET technology will allow for the development of new imaging protocols, such as ultra-fast imaging extended to dynamic whole body acquisitions. We demonstrated quantitative robustness even for the very short acquisition times, making whole body dynamic protocols appear readily feasible and quantitatively accurate.