Quantification of [¹¹C]PBR28 data after systemic lipopolysaccharide challenge

Area of Science:

• Neuroscience
• Immunology
• Radiochemistry

Background:

• Lipopolysaccharide (LPS) is a key immune stimulus.
• Positron emission tomography (PET) imaging of 18 kDa translocator protein (TSPO) with LPS provides a human model for neuroimmune signaling.
• Optimal quantification methods for LPS-PET TSPO studies require evaluation.

Purpose of the Study:

• To compare the sensitivity of six different quantification approaches for analyzing LPS-induced changes in brain TSPO.
• To identify the most effective methods for quantifying neuroimmune responses in human subjects.

Main Methods:

• Collected [11C]PBR28 PET data from 8 healthy volunteers before and after LPS challenge.
• Applied six quantification methods: two-tissue compartment models (2TCM, 2TCM-1k), multilinear analysis-1 (MA-1), simultaneous estimation (SIME), standardized uptake value (SUV), and SUV ratio (SUVR).
• Analyzed effect sizes for LPS-induced changes in TSPO binding.

Main Results:

• 2TCM, 2TCM-1k, MA-1, and SIME demonstrated significant effect sizes for LPS effects (partial η² = 0.56–0.89, p < .05).
• SUV and SUVR methods did not yield significant results for LPS effects.
• These findings indicate differential sensitivity among quantification techniques.

Conclusions:

• Kinetic modeling approaches (2TCM, 2TCM-1k, MA-1, SIME) are superior for quantifying LPS-induced neuroinflammation via TSPO PET.
• Standardized uptake values (SUV, SUVR) are less sensitive for detecting these neuroimmune changes.
• Accurate arterial input function (AIF) measurements are crucial for robust quantification in LPS-TSPO PET studies.