Intrapatient repeatability of background ¹⁸F-FDG uptake on PET/CT

Area of Science:

• Nuclear Medicine
• Radiology
• Oncology

Background:

• Standardized uptake values (SULs) are crucial for assessing tumor treatment response using 18F-FDG PET/CT.
• Selecting a stable background region is essential for reliable longitudinal assessments.

Purpose of the Study:

• To evaluate the repeatability of background standardized uptake values (SULs) in the aortic blood pool (ABP), liver, and muscle.
• To identify the most suitable background region for sequential 18F-FDG PET/CT scans in tumor treatment response assessment.

Main Methods:

• Repeat 18F-FDG PET/CT scans from 30 patients were analyzed within 1-4 days.
• Standardized uptake values (SULs) from ABP, liver, and muscle were measured.
• Intraclass correlation coefficients (ICCs), coefficients of variation (CVs), and Bland-Altman plots assessed repeatability.

Main Results:

• Muscle SUL demonstrated the highest repeatability (ICC=0.82, CV=10%), followed by ABP (ICC=0.65, CV=9%).
• Liver SUL showed lower repeatability (ICC=0.47, CV=12%) and was significantly correlated with blood glucose levels (BGL).
• Muscle SUL variations also correlated with BGL and tracer uptake period.

Conclusions:

• Liver SUL is sensitive to BGL fluctuations, making it less suitable as a reference background.
• ABP and muscle SULs are more stable and recommended as preferred backgrounds for serial 18F-FDG PET/CT evaluations.
• Consistent background selection improves the accuracy of tumor treatment response assessment.