The Dementias Platform UK PET/MR Harmonisation and Test-Retest Study
In this blog, Dr Pawel Markiewicz who leads the DPUK Imaging Network, explains a harmonisation and test/retest study which has been completed across our Imaging Network on PET and MR scans.
The study was an extensive assessment of the reliability of PET and MR and the viability of their use in therapeutic trials.
In the study we aimed to:
(1) harmonise PET and MR imaging protocols across the DPUK network to minimise measurement variability;
(2) quantitatively assess whether PET/MR can achieve reliability comparable to PET/CT through a test-retest amyloid brain PET study; and
(3) make the resulting PET/MR image and raw datasets publicly available.
While several test-retest studies have been reported for brain PET and whole body PET, these have typically involved either small cohorts or limited site configurations. In contrast, this study provides a comprehensive assessment of measurement variability across the DPUK network, incorporating two amyloid PET tracers and evaluating both within-site repeatability and across-site reproducibility. Such extensive assessment of reliability would not only strengthen the role of PET/MR in research studies but also support its qualification for use in therapeutic trials. Although the overall programme encompasses both PET and MRI, the present work focuses specifically on PET data quantification.
CL values across 74 scans showed excellent test-retest agreement (ICC = 0.968), improving to 0.987 after exclusion of one outlier. Mean test-retest variability was 2.58%. No statistically significant differences in variability were observed across repeatability versus reproducibility conditions, scanner types, or tracers. CL measurements were highly consistent with blinded visual reads across three independent raters.
The functional representation of the DPUK Imaging Network with reproducibility test-retest scan connections is shown below. Nodes represent imaging sites and are annotated with the total number of scans performed (n), and with badges indicating scanner vendor (Siemens Biograph mMR or GE Signa). Connection lines indicate achieved inter-site reproducibility test-retest scans, with participant codes shown adjacent to each connection.
The representative reconstructed amyloid PET images acquired with [18F]flutemetamol are shown as six transaxial slices per scan for amyloid positive (top panel) and amyloid negative (bottom panel) test-retest scans.
Test-retest agreement is shown below as scatter plot (a) and Bland-Altman plot (b). Scanner groups are shown in different colours (red for inter-scanner, green for Siemens Biograph mMR pairs, and blue for GE Signa pairs) and the text symbols correspond to participant/site identifiers. Positive visual reads are shown in square frames based on at least two positive reads out of three per scan, obtained from three independent raters. The scans with different tracers are marked by diamonds (♦) for [18F]flutemetamol (FLUTE) and circles (•) for [18F]florbetaben (FBB).
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READ THE PAPER Markiewicz, P.J., Eur J Nucl Med Mol Imaging (2026 |