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Published on: October 22, 2019
Test-retest reproducibility of 18F-MPPF PET in healthy humans: a reliability study
Nicolas Costes1, Luc Zimmer, Anthonin Reilhac
1CERMEP-Imagerie du vivant, PET Department, Lyon, France. costes@cermep.fr
Unlabelled:
The aim of this study was to assess the reliability of 2'-methoxyphenyl-(N-2'-pyridinyl)-p-18F-fluoro-benzamidoethylpiperazine (18F-MPPF) PET binding parameter's quantification via a test-retest study over a long-term period.
Methods:
Ten healthy volunteers underwent 2 dynamic 18F-MPPF PET scans in an interval of 6 mo. As a methodologic control, 10 simulated datasets, including interindividual functional and anatomic variabilities, were also used to assess the measurement variations in the absence of intraindividual variability. Indices of tracer binding were computed using 2 different models: (a) the simplified reference tissue model (SRTM) and (b) the Logan graphical model. The SRTM allows computing the binding potential (BP) index and plasma-to-brain transport constants (R1, k2). The Logan model evaluates the distribution volume (DV). For both methods, cerebellum was taken as the reference region. From both models, binding indices were calculated with time-activity curves extracted from regions of interest, on one hand, and for each voxel to perform parametric images on the other hand.
Results:
Reliability indices--that is, bias, variability, and intraclass correlation (ICC)--indicated a good reproducibility: the BP percentage change in mean between test and retest is close to 1% in rich regions and 2% in poor regions. The typical error is around 7%. Mean ICC is over 0.70. The DV percentage change in the mean is +/-2.5%, with a typical error close to 6% and an ICC over 0.60.
Conclusion:
Our results show a good reliability, with a reasonable level of intraindividual biologic variability that allows crossover studies with 18F-MPPF in which small percentage changes are expected between test and retest measurements, in group studies and for single subject assessment.
Insights
This study demonstrates that the PET tracer 18F-MPPF shows reliable quantification of binding parameters over a 6-month period. This high reproducibility supports its use in clinical trials for assessing treatment effects with 18F-MPPF.
Area of Science:
- Neuroscience
- Radiochemistry
- Pharmacology
Background:
- Positron Emission Tomography (PET) is crucial for quantifying neuroreceptor binding.
- 2'-methoxyphenyl-(N-2'-pyridinyl)-p-18F-fluoro-benzamidoethylpiperazine (18F-MPPF) is a PET tracer used for serotonin receptor imaging.
- Assessing the reliability of PET tracer quantification is essential for clinical trial design.
Purpose of the Study:
- To evaluate the long-term test-retest reliability of 18F-MPPF PET binding parameter quantification.
- To determine the intraindividual variability of 18F-MPPF binding measurements over a 6-month interval.
- To assess the suitability of 18F-MPPF for crossover studies and group analyses in clinical settings.
Main Methods:
- Ten healthy volunteers underwent two dynamic 18F-MPPF PET scans separated by 6 months.
- Binding potential (BP) and distribution volume (DV) were calculated using the simplified reference tissue model (SRTM) and Logan graphical model.
- Simulated datasets were used to control for interindividual variability and assess measurement variations.
- Time-activity curves were extracted from regions of interest and analyzed voxel-wise.
Main Results:
- The test-retest reliability for BP showed a mean percentage change of approximately 1-2% in rich and poor regions, respectively.
- Intraclass correlation (ICC) for BP was over 0.70, indicating good reproducibility.
- The DV measurements demonstrated a mean percentage change of +/-2.5% with an ICC over 0.60.
- Typical errors for BP and DV were around 7% and 6%, respectively.
Conclusions:
- 18F-MPPF PET demonstrates good test-retest reliability over a 6-month period.
- The observed intraindividual variability is sufficiently low for crossover studies and group analyses.
- These findings support the use of 18F-MPPF for detecting small changes in receptor binding in clinical research.
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