Abstract
PurposeThe aim of this study was to evaluate the use of a Bayesian penalized likelihood reconstruction algorithm (Q.Clear) for 89Zr-immunoPET image reconstruction and its potential to improve image quality and reduce the administered activity of 89Zr-immunoPET tracers.MethodsEight 89Zr-immunoPET whole-body PET/CT scans from three 89Zr-immunoPET clinical trials were selected for analysis. On average, patients were imaged 6.3 days (range 5.0–8.0 days) after administration of 69 MBq (range 65–76 MBq) of [89Zr]Zr-DFO-daratumumab, [89Zr]Zr-DFO-pertuzumab, or [89Zr]Zr-DFO-trastuzumab. List-mode PET data was retrospectively reconstructed using Q.Clear with incremental β-values from 150 to 7200, as well as standard ordered-subset expectation maximization (OSEM) reconstruction (2-iterations, 16-subsets, a 6.4-mm Gaussian transaxial filter, “heavy” z-axis filtering and all manufacturers’ corrections active). Reduced activities were simulated by discarding 50% and 75% of original counts in each list mode stream. All reconstructed PET images were scored for image quality and lesion detectability using a 5-point scale. SUVmax for normal liver and sites of disease and liver signal-to-noise ratio were measured.ResultsQ.Clear reconstructions with β = 3600 provided the highest scores for image quality. Images reconstructed with β-values of 3600 or 5200 using only 50% or 25% of the original counts provided comparable or better image quality scores than standard OSEM reconstruction images using 100% of counts.ConclusionThe Bayesian penalized likelihood reconstruction algorithm Q.Clear improved the quality of 89Zr-immunoPET images. This could be used in future studies to improve image quality and/or decrease the administered activity of 89Zr-immunoPET tracers.
Highlights
There are an increasing number of investigations of immunoPET for multiple clinical applications, including targeted imaging of HER2, CD38, PD-L1, CA9, PSMA, and others [1,2,3,4,5,6,7]
Images reconstructed with β-values in the range 150–600 (Fig. 1, a–c) were noisier and of inferior quality to the ordered-subset expectation maximization (OSEM) reference (Fig. 1, j) while β-values of 1000 generated images (Fig. 1, d) approximately similar to OSEM
Q.Clear image quality improved with increasing β from 1600 to 3600 (Fig. 1, e–g)
Summary
There are an increasing number of investigations of immunoPET for multiple clinical applications, including targeted imaging of HER2, CD38, PD-L1, CA9, PSMA, and others [1,2,3,4,5,6,7]. Zirconium-89 (89Zr) is most often chosen as the imaging radionuclide for immunoPET due to its favorable physical and chemical properties, including a 78-h half-life that is compatible with the relatively long times (on the order of a week) required to achieve optimal target-to-background differentials with antibody tracers [1, 4, 8]. The positron yield of 89Zr is only 23% and it emits a (non-coincident) 909 keV gamma ray photon in 100% of disintegrations. These characteristics, coupled with protracted antibody bio-kinetics, lead to relatively high radiation doses to patients. Even lower activities of approximately 37 MBq (1 mCi) [1, 6] have been used
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
