Evaluation of two population-based input functions for quantitative neurological FDG PET studies

Area of Science:

• Nuclear Medicine
• Neuroscience
• Medical Imaging

Background:

• Positron Emission Tomography (PET) with fluorodeoxyglucose (FDG) is crucial for measuring regional cerebral metabolic rate of glucose (rCMRGlc).
• Conventional rCMRGlc measurement necessitates frequent arterial or arterialised-venous (a-v) blood sampling to determine the plasma input function (IF).
• Frequent blood sampling increases radiation exposure for personnel and patient burden.

Purpose of the Study:

• To evaluate the accuracy of rCMRGlc measurements using population-based IFs calibrated with minimal blood samples.
• To assess if simplified IFs maintain diagnostic accuracy compared to traditional frequent sampling methods.
• To determine the feasibility of reducing blood sampling in FDG-PET studies.

Main Methods:

• Developed two population-based IFs: Standard IF (average of 26 patients' a-v IFs) and Feng IF (published model).
• Calibrated population-based IFs using only two a-v blood samples.
• Compared rCMRGlc values derived from population-based IFs with those from frequent a-v blood sampling in 20 non-diabetic and 6 diabetic patients.

Main Results:

• rCMRGlc values calculated using population-based IFs showed high correlation (r >= 0.992) with values from frequent sampling in both patient groups.
• Root mean square residuals were low (< 0.24 mg/min/100 g), indicating minimal loss of accuracy.
• The Feng IF showed a tendency to underestimate high rCMRGlc values.

Conclusions:

• Population-based IFs, calibrated with just two a-v blood samples, significantly simplify rCMRGlc measurement with minimal impact on accuracy.
• This approach substantially reduces the number of blood samples required, thereby decreasing radiation exposure for blood samplers.
• Simplified IFs offer a practical and safer alternative for routine FDG-PET rCMRGlc quantification.