Bayesian penalised likelihood reconstruction (Q.Clear) of 18F-fluciclovine PET for imaging of recurrent prostate cancer: semi-quantitative and clinical evaluation.

OBJECTIVE: 18F-Fluciclovine (FACBC) is an amino acid PET radiotracer approved for recurrent prostate cancer imaging. We investigate the use of Bayesian penalised likelihood (BPL) reconstruction for 18F-fluciclovine PET. METHODS: 15 18F-fluciclovine scans were reconstructed using ordered subset expectation maximisation (OSEM), OSEM + point spread function (PSF) modelling and BPL using ß-values 100-600. Lesion maximum standardised uptake value (SUVmax), organ SUVmean and standard deviation were measured. Deidentified reconstructions (OSEM, PSF, BPL using ß200-600) from 10 cases were visually analysed by two readers who indicated their most and least preferred reconstructions, and scored overall image quality, noise level, background marrow image quality and lesion conspicuity. RESULTS: Comparing BPL to OSEM, there were significant increments in lesion SUVmax and signal-to-background up to ß400, with highest gain in ß100 reconstructions (mean ΔSUVmax 3.9, p < 0.0001). Organ noise levels increased on PSF, ß100 and ß200 reconstructions. Across BPL reconstructions, there was incremental reduction in organ noise with increasing ß, statistically significant beyond ß300-500 (organ-dependent). Comparing with OSEM and PSF, lesion signal-to-noise was significantly increased in BPL reconstructions where ß ≥ 300 and  ≥ 200 respectively. On visual analysis, ß 300 had the first and second highest scores for image quality, ß500 and ß600 equal highest scores for marrow image quality and least noise, PSF and ß 200 had first and second highest scores for lesion conspicuity. For overall preference, one reader preferred ß 300 in 9/10 cases and the other preferred ß 200 in all cases. CONCLUSION: BPL reconstruction of 18F-fluciclovine PET images improves signal-to-noise ratio, affirmed by overall reader preferences. On balance, ß300 is suggested for 18F-fluciclovine whole body PET image reconstruction using BPL. Advances in knowledge: The optimum ß is different to that previously published for 18F-fluorodeoxyglucose, and has practical implications for a relatively new tracer in an environment with modern reconstruction technologies.