A narrative review of the methodology deployed in PET studies investigating low activity levels of radiopharmaceuticals

Objectives: This narrative review aims to extract evidence of the available literature on dose optimisations for Positron Emission Tomography (PET) imaging, conducted in clinical PET- Computed Tomography (CT) and PET-Magnetic Resonance (MR) scanners, with non-extended field of view. This work will also strive to present recommendations on the evidence that needs to be collected.

Key findings: The literature pertaining to dose optimisation is sparse, with only sixteen studies eligible for inclusion. Non-clinical experimental designs were the most common methodology for performing dose optimisation, as they don't require an overexposure of patients. Image analysis methodologies ranged from assessment of quantitative outcomes to visual assessments, with most studies deploying a mix of both approaches. The majority of studies focusing on local dose optimisation were conducted in oncology (n = 9) and using [18F]FDG (n = 13). Dose optimisation in PET imaging can lead to a reduction of the patient administered dose, which in turn translates to more doses available for draw-up from the same vial and less radioactive waste. Dose optimisation can therefore foster departmental sustainability.

Conclusion: Advances in scanner hardware and software have created suitable conditions for local dose optimisations to take place. This review suggests that the most suitable methodology to be deployed in such investigations is a non-clinical experimental design. Further evidence on local dose optimisation in PET-CT and PET-MR is required, particularly with a focus on broader clinical indications and novel radiopharmaceuticals.

Implications for practice: This narrative review suggests that, whilst local diagnostic reference levels (DRLs) are available in Nuclear Medicine, local dose optimisations should still be conducted for PET-CT and PET-MR examinations.