Total-body [18F]FDG-PET/CT imaging of healthy controls with minimal effective subject dose

Ziel/Aim: Total-body (TB) PET/CT systems offer increased sensitivity, enabling low-tracer-activity protocols. AI-driven methods can generate CT-like attenuation maps from raw PET data. Combining these approaches may lower subject exposure, making TB-PET/CT suitable for screening healthy individuals to evaluate whole-body metabolism in the absence of disease.

Methodik/Methods: 50 healthy controls underwent a test-retest imaging protocol (5-week interval) using a Siemens QUADRA TB-PET system. Subjects fasted for 6 hours before a (113±5) MBq [18F]FDG injection and underwent a 60-min listmode PET scan with a low-dose (1 mSv) CT scan (supine/arms down). Ten controls (6F/4M, BMI 24±4 kg/m²) were included in a first, interim, analysis, focused on the static PET acquired at 55-60 min p.i. Emission counts were removed randomly from PET-listmode files of 55-60 min p.i. to simulate lower tracer activities: 100%, 50%, 25%, 10%, and 5%. Effective doses (ED) were estimated for each activity level. Synthetic CT images (ED=0 mSv) were created with the CTlessPET [1] software and used for reconstructing attenuation-corrected PET images. The original CTs were segmented in multiple volumes of interest using MOOSE [2]. Mean standardized uptake-values normalized to body weight (SUVbw) and coefficients of variation (COV) were extracted and compared across the 5 activity levels.

Ergebnisse/Results: PET-related ED decreased from (2.9±0.3) mSv at 100% counts to (0.1±0.05) mSv at 5% counts. Mean SUVbw at 100% dose ranged from 0.4±0.1 (lungs) to 3.0±0.3 (kidneys). Minimal SUVbw group variations (%-difference<5%) were noted when reducing the dose to 25% (ED=(0.48±0.02) mSv), except in the lungs (%-diff=7% at 25%), likely due to motion-related PET/CT mismatch. At 10% and 5%, mean%-diff of SUVbw exceeded 10% in most regions, and COV increased, particularly in skeletal muscle and subcutaneous fat segmentations, where it rose from an average of 35% to 55%.

Schlussfolgerungen/Conclusions: The effective exposure of healthy controls undergoing TB-FDG-PET/CT for metabolic mapping can be reduced to 0.48 mSv while ensuring robust quantification of organ-based metabolism.

Publication History

Article published online:
12 March 2025

• Literatur/References

• 1 Montgomery ME. et al. Diagnostics 2023;
• 2 Sundar LKS. et al. J Nuc Med 2022;