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EJNMMI Research
Published in: EJNMMI Research 1/2017

Open Access 01-12-2017 | Short communication

Assessment of simplified ratio-based approaches for quantification of PET [11C]PBR28 data

Authors: Granville J. Matheson, Pontus Plavén-Sigray, Anton Forsberg, Andrea Varrone, Lars Farde, Simon Cervenka

Published in: EJNMMI Research | Issue 1/2017

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Abstract

Purpose

Kinetic modelling with metabolite-corrected arterial plasma is considered the gold standard for quantification of [11C]PBR28 binding to the translocator protein (TSPO), since there is no brain region devoid of TSPO that can serve as reference. The high variability in binding observed using this method has motivated the use of simplified ratio-based approaches such as standardised uptake value ratios (SUVRs) and distribution volume (VT) ratios (DVRs); however, the reliability of these measures and their relationship to VT have not been sufficiently evaluated.

Methods

Data from a previously published [11C]PBR28 test-retest study in 12 healthy subjects were reanalysed. VT was estimated using a two-tissue compartment model. SUVR and DVR values for the frontal cortex were calculated using the whole brain and cerebellum as denominators. Test-retest reliability was assessed for all measures. Interregional correlations were performed for SUV and VT, and principal component analysis (PCA) was applied. Lastly, correlations between ratio-based outcomes and VT were assessed.

Results

Reliability was high for VT, moderate to high for SUV and SUVR, and poor for DVR. Very high interregional correlations were observed for both VT and SUV (all R 2 > 85%). The PCA showed that almost all variance (>98%) was explained by a single component. Ratio-based methods correlated poorly with VT (all R 2 < 34%, divided by genotype).

Conclusions

The reliability was good for SUVR, but poor for DVR. Both outcomes showed little to no association with VT, questioning their validity. The high interregional correlations for VT and SUV suggest that after dividing by a denominator region, most of the biologically relevant signal is lost. These observations imply that results from TSPO PET studies using SUVR or DVR estimates should be interpreted with caution.
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Metadata
Title
Assessment of simplified ratio-based approaches for quantification of PET [11C]PBR28 data
Authors
Granville J. Matheson
Pontus Plavén-Sigray
Anton Forsberg
Andrea Varrone
Lars Farde
Simon Cervenka
Publication date
01-12-2017
Publisher
Springer Berlin Heidelberg
Published in
EJNMMI Research / Issue 1/2017
Electronic ISSN: 2191-219X
DOI
https://doi.org/10.1186/s13550-017-0304-1

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