Authors: (including presenting author): :
Keith Kwan
Affiliation: :
Department of Clinical Oncology, Tuen Mun Hospital
Keyword 2: :
half-time acquisition
Keyword 4: :
higher patient throughput
Keyword 6: :
digital-PET scanner
Introduction: :
Shorter acquisition times have conventionally been associated with reduced lesion detectability in early generation of analog-based PET systems. However, this is not the case for new generation digital-based PET systems, with which many-folds of higher radioactivity sensitivity are detected so that clinically shorter acquisition times are feasible for patient service. We performed phantom studies to confirm comparable lesion detectability in half acquisition time with that in full acquisition time in 18FDG PET imaging.
Objectives: :
To study the consistency in measurable image quality of standardized uptake values (SUV) of SUVmax, SUVmean and SUVpeak as obtained from a PET body phantom undergone different acquisition times to ensure comparable lesion detectability in half-time acquisition protocol with regular full-time protocol for higher patient throughput from our 18FDG PET service.
Methodology: :
Due to the many-folds gain in radioactivity sensitivity of digital-PET imaging compared to conventional analog-PET scans, it offers a wide range of combinations of injection doses and scan times. A 3D-volumetric PET body phantom, inserted with spheres of different diameters, was scanned with a digital-PET scanner (GE, Discovery MI) for acquisition protocols of full-time and half-time. Ratio of radioactivity concentration of 18FDG in spheres to that in the phantom body was 4:1. Image reconstruction was performed with the Bayesian penalized-likelihood iterative method, with which values of SUV indices were evaluated and compared between acquisition protocols of full-time and half-time in order to confirm comparable lesion detectability between the two protocols.
Result & Outcome: :
For the full-time protocol, the SUVmax, SUVmean and SUVpeak converged to 5.0, 3.4 and 4.2 respectively for large sized spheres and for their different radioactivity concentration while for half-time protocol, the corresponding SUV indices were 4.8, 3.5 and 4.0 respectively (p=0.29, Wilcoxcon matched pairs test), showing no statistically significant difference in SUV indices between the full-time and half-time protocol and hence comparable lesion detectability between the two protocols. Reconstructed phantom images will be presented and discussed to achieve these results. If the acquisition time is reduced to half, theoretically patient throughput will be increased twice. Indices of SUV are good measurable parameters to demonstrate that full dose with half time can be achieved because of the gain in radioactivity detection with the use of digital-PET scanners. Further phantom studies will be performed to optimize the patient dose and imaging time in order to further save hospital resources in radiopharmaceuticals and to further increase patient throughput.
