Optimization of PET acquisition time for thoracic lesions in 18F-FDG PET/MRI: a retrospective analysis.

OBJECTIVE

This study aimed to define the minimum positron emission tomography (PET) acquisition time for chest PET/magnetic resonance imaging (MRI), providing image quality and lesion detectability comparable to a 20-min reference.

MATERIALS AND

METHODS

In this retrospective study, list-mode data from 101 patients undergoing chest 18F-fluorodeoxyglucose (18F-FDG) PET/MRI on a 3-T PET/MRI system were reconstructed to simulate 10 acquisition times (0.5-20 min). Two readers assessed subjective image quality using a 5-point Likert scale. Quantitative parameters, including maximum, mean of the lesion standardized uptake value (L_SUVmax, L_SUVmean), image noise ratio (INR), and lesion-to-background ratio (LBR), were measured. Lesion detectability was defined as the miss rate relative to lesions visible on the 20-min reference acquisition.

RESULTS

In 101 patients, 283 lesions were identified. Subjective scores increased from a median of 2 (interquartile range 2-2) at 0.5 min to 5 (5-5) at 7 min (p < 0.001), then plateaued (7-20 min; all p = 1.000). L_SUVmax, L_SUVmean, and LBR inversely correlated with scan duration (all p < 0.001). L_SUVmean stabilized at 3 min (p = 1.000), while L_SUVmax/LBR stabilized at 5 min (p = 1.000). INR required 10 min (p ≥ 0.054). Lesion miss rates increased time dependently, from 0% at 15 min to 7.77% at 0.5 min.

CONCLUSION

A 7-min acquisition time provided subjective quality and detectability comparable to the 20-min protocol, supporting routine use. For quantitative assessments, 3-5 min sufficed, and patients with shorter 18F-FDG uptake or larger lesions may be adequately assessed with 2 min.

KEY POINTS: Question What is the minimum PET acquisition time for chest 18F-FDG PET/MRI that maintains image quality and lesion detectability equivalent to a 20‑min reference? Findings A 7‑min PET acquisition matches 20‑min image quality and detectability; quantitative parameters stabilize at 3‑5 min; 2 min suffices for patients with shorter uptake or larger lesions. Relevance statement Reducing PET acquisition time to 7 min enhances patient comfort, reduces motion artifacts, and increases scanner throughput without compromising chest PET/MRI diagnostic performance, thereby improving patient experience and workflow efficiency. Further clinical validation is needed.