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

Objective: F-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 F-fluciclovine PET.

Methods: 15 F-fluciclovine scans were reconstructed using ordered subset expectation maximisation (OSEM), OSEM + point spread function (PSF) modelling and BPL using β-values 100-600. Lesion maximum standardised uptake value (SUV), organ SUV and standard deviation were measured. Deidentified reconstructions (OSEM, PSF, BPL using β200-600) 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 SUV and signal-to-background up to β400, with highest gain in β100 reconstructions (mean ΔSUV 3.9, p < 0.0001). Organ noise levels increased on PSF, β100 and β200 reconstructions. Across BPL reconstructions, there was incremental reduction in organ noise with increasing β, statistically significant beyond β300-500 (organ-dependent). Comparing with OSEM and PSF, lesion signal-to-noise was significantly increased in BPL reconstructions where β ≥ 300 and  ≥ 200 respectively. On visual analysis, β 300 had the first and second highest scores for image quality, β500 and β600 equal highest scores for marrow image quality and least noise, PSF and β 200 had first and second highest scores for lesion conspicuity. For overall preference, one reader preferred β 300 in 9/10 cases and the other preferred β 200 in all cases.

Conclusion: BPL reconstruction of F-fluciclovine PET images improves signal-to-noise ratio, affirmed by overall reader preferences. On balance, β300 is suggested for F-fluciclovine whole body PET image reconstruction using BPL. Advances in knowledge: The optimum β is different to that previously published for F-fluorodeoxyglucose, and has practical implications for a relatively new tracer in an environment with modern reconstruction technologies.