Standardisation of PET scanners participating in multicentre trials is important in achieving reliable results and in maximizing the power of the study. The first multicentre clinical trial studies involving seven PET-MR scanners in the UK (four GE SIGNA and three Siemens mMR) are underway, led by Dementias Platform UK. In this study, the qualification of the seven scanners was tested using the NEMA image quality phantom. Consistent scanning methodology was followed across all sites with a 5:1 sphere-to-background contrast ratio and a CT-based μ-map used for attenuation correction. The reconstruction parameters were consistent between scanners of the same manufacturer. The SUVmean and SUVmax for all spheres were comparable between all scanners and within EARL performance specifications. Moreover, the averaged SUV values from all scanners were similar with the averaged corresponding values from 25 PET-CT scanners across the UK currently eligible to participate in multicentre trials. In conclusion, these preliminary results support the reliable comparison of PET performance across the PET-MR scanners.