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Updated: Jun 27, 2026
Erosion Identification in Metacarpophalangeal Joints in Rheumatoid Arthritis using High-Resolution Peripheral Quantitative Computed Tomography
Published on: October 6, 2023
Quantification of (R)-[11C]PK11195 binding in rheumatoid arthritis
M A Kropholler1, R Boellaard, E H Elzinga
1Department of Nuclear Medicine & PET Research, VU University Medical Centre, Amsterdam, The Netherlands. m.a.kropholler@gmail.com
Purpose:
Rheumatoid arthritis (RA) involves migration of macrophages into inflamed areas. (R)-[(11)C]PK11195 binds to peripheral benzodiazepine receptors, expressed on macrophages, and may be used to quantify inflammation using positron emission tomography (PET). This study evaluated methods for the quantification of (R)-[(11)C]PK11195 binding in the knee joints of RA patients.
Methods:
Data from six patients with RA were analysed. Dynamic PET scans were acquired in 3-D mode following (R)-[(11)C]PK11195 injection. During scanning arterial radioactivity concentrations were measured to determine the plasma (R)-[(11)C]PK11195 concentrations. Data were analysed using irreversible and reversible one-tissue and two-tissue compartment models and input functions with various types of metabolite correction. Model preferences according to the Akaike information criterion (AIC) and correlations between measures were evaluated. Correlations between distribution volume (V(d)) and standardized uptake values (SUV) were evaluated.
Results:
AIC indicated optimal performance for a one-tissue reversible compartment model including blood volume. High correlations were observed between V(d) obtained using different input functions (R(2)=0.80-1.00) and between V(d) obtained with one- and two-tissue reversible compartment models (R(2)=0.75-0.94). A high correlation was observed between optimal V(d) and SUV after injection (R(2)=0.73).
Conclusion:
(R)-[(11)C]PK11195 kinetics in the knee were best described by a reversible single-tissue compartment model including blood volume. Applying metabolite corrections did not increase sensitivity. Due to the high correlation with V(d), SUV is a practical alternative for clinical use.
Insights
Quantifying inflammation in rheumatoid arthritis (RA) using (R)-[(11)C]PK11195 PET scans is feasible. A reversible single-tissue compartment model best describes the tracer kinetics, with standardized uptake values (SUV) serving as a practical alternative to distribution volume (V(d)) for clinical use.
Area of Science:
- Nuclear medicine
- Radiochemistry
- Rheumatology
Background:
- Rheumatoid arthritis (RA) is characterized by macrophage infiltration into inflamed joints.
- (R)-[(11)C]PK11195 is a positron emission tomography (PET) tracer that binds to peripheral benzodiazepine receptors on macrophages, enabling inflammation imaging.
- Accurate quantification of tracer binding is crucial for assessing disease activity in RA.
Purpose of the Study:
- To evaluate methods for quantifying (R)-[(11)C]PK11195 binding in the knee joints of RA patients using PET.
- To determine the optimal kinetic model for describing (R)-[(11)C]PK11195 uptake in RA knee joints.
- To assess the correlation between different quantification methods and the utility of standardized uptake values (SUV) for clinical application.
Main Methods:
- Dynamic 3-D PET scans were acquired in six RA patients following intravenous injection of (R)-[(11)C]PK11195.
- Arterial blood samples were analyzed to determine plasma tracer concentrations (input function).
- Data were analyzed using irreversible and reversible one- and two-tissue compartment models with various metabolite corrections; Akaike Information Criterion (AIC) was used for model selection, and correlations between distribution volume (V(d)) and SUV were evaluated.
Main Results:
- The reversible single-tissue compartment model including blood volume demonstrated optimal performance based on AIC.
- High correlations were found between V(d) values derived from different input functions and between one- and two-tissue reversible models.
- A significant correlation (R(2)=0.73) was observed between the optimal V(d) and SUV, indicating good agreement.
Conclusions:
- The kinetics of (R)-[(11)C]PK11195 in RA knee joints are best described by a reversible single-tissue compartment model.
- Metabolite correction of the input function did not significantly enhance the sensitivity of the quantification.
- Standardized uptake value (SUV) offers a practical and reliable alternative to V(d) for clinical quantification of (R)-[(11)C]PK11195 binding in RA.
