The Dementias Platform UK PET/MR harmonisation and test-retest study: assessment of PET repeatability and reproducibility across the national network

Pawel J Markiewicz; Gerard Thompson; Joanna M Wardlaw; Catriona Wimberley; Craig Ritchie; John-Paul Taylor; David Brooks; Ross Maxwell; Michael Firbank; Nigel Hoggard; Li Su; Jim Wild; Philip Hillel; Victoria Rhodes-Bradford; Laura M Parkes; John T O'Brien; Stephen F Carter; Franklin I Aigbirhio; Tim Fryer; Paul M Matthews; Paresh Malhotra; Gabrielle Grey; Will Hallett; Dilek Ocal; John C Dickson; Enrico De Vita; David L Thomas; Nick C Fox; Giorgios Krokos; Jane E Mackewn; Paul Marsden; Alexander Hammers; Karl Herholz; Frederik Barkhof; Julian C Matthews

doi:10.1007/s00259-026-07885-4

The Dementias Platform UK PET/MR harmonisation and test-retest study: assessment of PET repeatability and reproducibility across the national network

Pawel J Markiewicz^*
, Gerard Thompson
, Joanna M Wardlaw
, Catriona Wimberley
, Craig Ritchie
, John-Paul Taylor
, David Brooks
, Ross Maxwell
, Michael Firbank
, Nigel Hoggard
, Li Su
, Jim Wild
, Philip Hillel
, Victoria Rhodes-Bradford
, Laura M Parkes
, John T O'Brien
, Stephen F Carter
, Franklin I Aigbirhio
, Tim Fryer
, Paul M Matthews

Paresh Malhotra, Gabrielle Grey, Will Hallett, Dilek Ocal, John C Dickson, Enrico De Vita, David L Thomas, Nick C Fox, Giorgios Krokos, Jane E Mackewn, Paul Marsden, Alexander Hammers, Karl Herholz, Frederik Barkhof, Julian C Matthews

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

Purpose
Positron emission tomography combined with magnetic resonance imaging (PET/MR) has not yet achieved the level of adoption of PET/CT. This study aimed to harmonise PET imaging protocols across a national PET/MR network and to quantitatively assess whether PET/MR can achieve reliability comparable to PET/CT. While previous PET test-retest studies have demonstrated good repeatability, they have typically been limited to small cohorts or restricted site configurations.

Methods
We conducted a multi-site harmonisation and rigorous test-retest study across the network of eight PET/MR scanners. Thirty-seven healthy older participants (65-90 years) underwent harmonised one-hour amyloid PET/MR scans using either [¹⁸F]flutemetamol or [¹⁸F]florbetaben on two occasions. Retest scans were performed under conditions of same-site repeatability or multi-site reproducibility. Harmonised acquisition and reconstruction protocols were applied, and amyloid burden was quantified on the Centiloid (CL) scale.

Results
CL values across 74 scans showed excellent test-retest agreement (ICC = 0.968), improving to 0.987 after exclusion of one attenuation correction related outlier. Mean test-retest variability was 2.58%. No statistically significant differences were observed across repeatability versus reproducibility conditions, scanner types, or tracers. CL measurements were highly consistent with three independent blinded visual reads.

Conclusion
This study demonstrates that harmonised PET/MR achieves high reliability comparable to PET/CT. Although the accuracy of attenuation maps requires checks, this study supports the use of PET/MR for quantitative amyloid imaging in research and therapeutic trials, and provides a valuable open resource of image and raw PET/MR data for further methodological development.

Original language	English
Pages (from-to)	1-20
Journal	European journal of nuclear medicine and molecular imaging
Volume	Online First
Early online date	29 Apr 2026
DOIs	https://doi.org/10.1007/s00259-026-07885-4
Publication status	E-pub ahead of print - 29 Apr 2026

Keywords

Reproducibility
Repeatability
PET
Harmonisation
Multi-site
Test-Retest
Amyloid
PET/MR

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Markiewicz, P. J., Thompson, G., Wardlaw, J. M., Wimberley, C., Ritchie, C., Taylor, J.-P., Brooks, D., Maxwell, R., Firbank, M., Hoggard, N., Su, L., Wild, J., Hillel, P., Rhodes-Bradford, V., Parkes, L. M., O'Brien, J. T., Carter, S. F., Aigbirhio, F. I., Fryer, T., ... Matthews, J. C. (2026). The Dementias Platform UK PET/MR harmonisation and test-retest study: assessment of PET repeatability and reproducibility across the national network. European journal of nuclear medicine and molecular imaging, Online First, 1-20. Advance online publication. https://doi.org/10.1007/s00259-026-07885-4

@article{25a938395a6a4494bb00c1acc1c6640a,

title = "The Dementias Platform UK PET/MR harmonisation and test-retest study: assessment of PET repeatability and reproducibility across the national network",

abstract = "Purpose Positron emission tomography combined with magnetic resonance imaging (PET/MR) has not yet achieved the level of adoption of PET/CT. This study aimed to harmonise PET imaging protocols across a national PET/MR network and to quantitatively assess whether PET/MR can achieve reliability comparable to PET/CT. While previous PET test-retest studies have demonstrated good repeatability, they have typically been limited to small cohorts or restricted site configurations. Methods We conducted a multi-site harmonisation and rigorous test-retest study across the network of eight PET/MR scanners. Thirty-seven healthy older participants (65-90 years) underwent harmonised one-hour amyloid PET/MR scans using either [18F]flutemetamol or [18F]florbetaben on two occasions. Retest scans were performed under conditions of same-site repeatability or multi-site reproducibility. Harmonised acquisition and reconstruction protocols were applied, and amyloid burden was quantified on the Centiloid (CL) scale. Results CL values across 74 scans showed excellent test-retest agreement (ICC = 0.968), improving to 0.987 after exclusion of one attenuation correction related outlier. Mean test-retest variability was 2.58\%. No statistically significant differences were observed across repeatability versus reproducibility conditions, scanner types, or tracers. CL measurements were highly consistent with three independent blinded visual reads. Conclusion This study demonstrates that harmonised PET/MR achieves high reliability comparable to PET/CT. Although the accuracy of attenuation maps requires checks, this study supports the use of PET/MR for quantitative amyloid imaging in research and therapeutic trials, and provides a valuable open resource of image and raw PET/MR data for further methodological development.",

keywords = "Reproducibility, Repeatability, PET, Harmonisation, Multi-site, Test-Retest, Amyloid, PET/MR",

author = "Markiewicz, \{Pawel J\} and Gerard Thompson and Wardlaw, \{Joanna M\} and Catriona Wimberley and Craig Ritchie and John-Paul Taylor and David Brooks and Ross Maxwell and Michael Firbank and Nigel Hoggard and Li Su and Jim Wild and Philip Hillel and Victoria Rhodes-Bradford and Parkes, \{Laura M\} and O'Brien, \{John T\} and Carter, \{Stephen F\} and Aigbirhio, \{Franklin I\} and Tim Fryer and Matthews, \{Paul M\} and Paresh Malhotra and Gabrielle Grey and Will Hallett and Dilek Ocal and Dickson, \{John C\} and \{De Vita\}, Enrico and Thomas, \{David L\} and Fox, \{Nick C\} and Giorgios Krokos and Mackewn, \{Jane E\} and Paul Marsden and Alexander Hammers and Karl Herholz and Frederik Barkhof and Matthews, \{Julian C\}",

note = "Funding: This study was funded primarily by an UK MRC partnership grant (MR/N025792/1). Additional support was provided by the Innovative Medicines Initiative 2 Joint Undertaking under grant agreement No 115952 (European Union{\textquoteright}s Horizon 2020). Partners also received support from other individual grants and from NIHR Biomedical Research Centres. Joanna M Wardlaw is part supported by the UK Dementia Research Institute Ltd., which is supported by the UK Medical Research Council, Alzheimer{\textquoteright}s Society and Alzheimer{\textquoteright}s Research UK. Li Su is funded by Alzheimer{\textquoteright}s Research UK Senior Research Fellowship (ARUK-SRF2017B-1). Michael Firbank and John-Paul Taylor are supported by the NIHR Newcastle Biomedical Research Centre. John O{\textquoteright}Brien, Franklin Aigbirhio and Tim Fryer are supported by the NIHR Cambridge Biomedical Research Centre. Nick Fox and Frederik Barkhof were supported by the NIHR UCLH Biomedical Research Centre. Paul Matthews acknowledges generous personal support from the Edmond J Safra Foundation and Lily Safra and an NIHR Senior Investigator Award. His work was supported by the UK Dementia Research Institute, which receives funding from UK DRI Ltd., funded by the UK Medical Research Council, Alzheimer{\textquoteright}s Society, and Alzheimer{\textquoteright}s Research UK.",

year = "2026",

month = apr,

day = "29",

doi = "10.1007/s00259-026-07885-4",

language = "English",

volume = "Online First",

pages = "1--20",

journal = "European journal of nuclear medicine and molecular imaging",

issn = "1619-7089",

publisher = "Springer",

}

Markiewicz, PJ, Thompson, G, Wardlaw, JM, Wimberley, C, Ritchie, C, Taylor, J-P, Brooks, D, Maxwell, R, Firbank, M, Hoggard, N, Su, L, Wild, J, Hillel, P, Rhodes-Bradford, V, Parkes, LM, O'Brien, JT, Carter, SF, Aigbirhio, FI, Fryer, T, Matthews, PM, Malhotra, P, Grey, G, Hallett, W, Ocal, D, Dickson, JC, De Vita, E, Thomas, DL, Fox, NC, Krokos, G, Mackewn, JE, Marsden, P, Hammers, A, Herholz, K, Barkhof, F & Matthews, JC 2026, 'The Dementias Platform UK PET/MR harmonisation and test-retest study: assessment of PET repeatability and reproducibility across the national network', European journal of nuclear medicine and molecular imaging, vol. Online First, pp. 1-20. https://doi.org/10.1007/s00259-026-07885-4

The Dementias Platform UK PET/MR harmonisation and test-retest study: assessment of PET repeatability and reproducibility across the national network. / Markiewicz, Pawel J; Thompson, Gerard; Wardlaw, Joanna M et al.
In: European journal of nuclear medicine and molecular imaging, Vol. Online First, 29.04.2026, p. 1-20.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - The Dementias Platform UK PET/MR harmonisation and test-retest study

T2 - assessment of PET repeatability and reproducibility across the national network

AU - Markiewicz, Pawel J

AU - Thompson, Gerard

AU - Wardlaw, Joanna M

AU - Wimberley, Catriona

AU - Ritchie, Craig

AU - Taylor, John-Paul

AU - Brooks, David

AU - Maxwell, Ross

AU - Firbank, Michael

AU - Hoggard, Nigel

AU - Su, Li

AU - Wild, Jim

AU - Hillel, Philip

AU - Rhodes-Bradford, Victoria

AU - Parkes, Laura M

AU - O'Brien, John T

AU - Carter, Stephen F

AU - Aigbirhio, Franklin I

AU - Fryer, Tim

AU - Matthews, Paul M

AU - Malhotra, Paresh

AU - Grey, Gabrielle

AU - Hallett, Will

AU - Ocal, Dilek

AU - Dickson, John C

AU - De Vita, Enrico

AU - Thomas, David L

AU - Fox, Nick C

AU - Krokos, Giorgios

AU - Mackewn, Jane E

AU - Marsden, Paul

AU - Hammers, Alexander

AU - Herholz, Karl

AU - Barkhof, Frederik

AU - Matthews, Julian C

N1 - Funding: This study was funded primarily by an UK MRC partnership grant (MR/N025792/1). Additional support was provided by the Innovative Medicines Initiative 2 Joint Undertaking under grant agreement No 115952 (European Union’s Horizon 2020). Partners also received support from other individual grants and from NIHR Biomedical Research Centres. Joanna M Wardlaw is part supported by the UK Dementia Research Institute Ltd., which is supported by the UK Medical Research Council, Alzheimer’s Society and Alzheimer’s Research UK. Li Su is funded by Alzheimer’s Research UK Senior Research Fellowship (ARUK-SRF2017B-1). Michael Firbank and John-Paul Taylor are supported by the NIHR Newcastle Biomedical Research Centre. John O’Brien, Franklin Aigbirhio and Tim Fryer are supported by the NIHR Cambridge Biomedical Research Centre. Nick Fox and Frederik Barkhof were supported by the NIHR UCLH Biomedical Research Centre. Paul Matthews acknowledges generous personal support from the Edmond J Safra Foundation and Lily Safra and an NIHR Senior Investigator Award. His work was supported by the UK Dementia Research Institute, which receives funding from UK DRI Ltd., funded by the UK Medical Research Council, Alzheimer’s Society, and Alzheimer’s Research UK.

PY - 2026/4/29

Y1 - 2026/4/29

N2 - Purpose Positron emission tomography combined with magnetic resonance imaging (PET/MR) has not yet achieved the level of adoption of PET/CT. This study aimed to harmonise PET imaging protocols across a national PET/MR network and to quantitatively assess whether PET/MR can achieve reliability comparable to PET/CT. While previous PET test-retest studies have demonstrated good repeatability, they have typically been limited to small cohorts or restricted site configurations. Methods We conducted a multi-site harmonisation and rigorous test-retest study across the network of eight PET/MR scanners. Thirty-seven healthy older participants (65-90 years) underwent harmonised one-hour amyloid PET/MR scans using either [18F]flutemetamol or [18F]florbetaben on two occasions. Retest scans were performed under conditions of same-site repeatability or multi-site reproducibility. Harmonised acquisition and reconstruction protocols were applied, and amyloid burden was quantified on the Centiloid (CL) scale. Results CL values across 74 scans showed excellent test-retest agreement (ICC = 0.968), improving to 0.987 after exclusion of one attenuation correction related outlier. Mean test-retest variability was 2.58%. No statistically significant differences were observed across repeatability versus reproducibility conditions, scanner types, or tracers. CL measurements were highly consistent with three independent blinded visual reads. Conclusion This study demonstrates that harmonised PET/MR achieves high reliability comparable to PET/CT. Although the accuracy of attenuation maps requires checks, this study supports the use of PET/MR for quantitative amyloid imaging in research and therapeutic trials, and provides a valuable open resource of image and raw PET/MR data for further methodological development.

AB - Purpose Positron emission tomography combined with magnetic resonance imaging (PET/MR) has not yet achieved the level of adoption of PET/CT. This study aimed to harmonise PET imaging protocols across a national PET/MR network and to quantitatively assess whether PET/MR can achieve reliability comparable to PET/CT. While previous PET test-retest studies have demonstrated good repeatability, they have typically been limited to small cohorts or restricted site configurations. Methods We conducted a multi-site harmonisation and rigorous test-retest study across the network of eight PET/MR scanners. Thirty-seven healthy older participants (65-90 years) underwent harmonised one-hour amyloid PET/MR scans using either [18F]flutemetamol or [18F]florbetaben on two occasions. Retest scans were performed under conditions of same-site repeatability or multi-site reproducibility. Harmonised acquisition and reconstruction protocols were applied, and amyloid burden was quantified on the Centiloid (CL) scale. Results CL values across 74 scans showed excellent test-retest agreement (ICC = 0.968), improving to 0.987 after exclusion of one attenuation correction related outlier. Mean test-retest variability was 2.58%. No statistically significant differences were observed across repeatability versus reproducibility conditions, scanner types, or tracers. CL measurements were highly consistent with three independent blinded visual reads. Conclusion This study demonstrates that harmonised PET/MR achieves high reliability comparable to PET/CT. Although the accuracy of attenuation maps requires checks, this study supports the use of PET/MR for quantitative amyloid imaging in research and therapeutic trials, and provides a valuable open resource of image and raw PET/MR data for further methodological development.

KW - Reproducibility

KW - Repeatability

KW - PET

KW - Harmonisation

KW - Multi-site

KW - Test-Retest

KW - Amyloid

KW - PET/MR

U2 - 10.1007/s00259-026-07885-4

DO - 10.1007/s00259-026-07885-4

M3 - Article

C2 - 42050257

SN - 1619-7089

VL - Online First

SP - 1

EP - 20

JO - European journal of nuclear medicine and molecular imaging

JF - European journal of nuclear medicine and molecular imaging

ER -

Markiewicz PJ, Thompson G, Wardlaw JM, Wimberley C, Ritchie C, Taylor JP et al. The Dementias Platform UK PET/MR harmonisation and test-retest study: assessment of PET repeatability and reproducibility across the national network. European journal of nuclear medicine and molecular imaging. 2026 Apr 29;Online First:1-20. Epub 2026 Apr 29. doi: 10.1007/s00259-026-07885-4

The Dementias Platform UK PET/MR harmonisation and test-retest study: assessment of PET repeatability and reproducibility across the national network

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