Advancing Rapid Acquisition in Lung PET-CT: Protocol Optimisation via Reduced ¹⁸F-FDG Activity and Scan Duration

Lung cancer (LC) is the fourth most common cancer in Egypt and the second in Europe and the United States. Diagnosis and staging rely on fluorodeoxyglucose (¹⁸F-FDG) PET-CT examinations. This study aimed to optimise PET-CT protocols for LC patients by assessing how varying the acquisition duration at a half-dose of ¹⁸F-FDG affects results.

Thirty adult male and female patients with newly diagnosed LC (mean age 42 ± 10.8 years) were prospectively enrolled. Each received 1.85 MBq/kg (50 % dose) intravenous ¹⁸F-FDG. Imaging was performed on a Biograph mCT digital PET-CT scanner with lutetium oxyorthosilicate detectors and time-of-flight resolution < 450 ps. A single 120 s/bp acquisition was obtained, with datasets at 66 s and 50 s reconstructed retrospectively. SUV_max of primary lesions and SUV_mean of liver, sternum, and blood pool were measured to calculate tumour-to-liver (TLR), tumour-to-sternum (TSR), and tumour-to-background (TBR) ratios.

SUV_max values of LC lesions remained stable across all half-dose acquisitions, with only modest (< 5 %) increases at 66 and 120 s/bp. Longer acquisitions enhanced TLR, TSR, and TBR, improving lesion contrast and diagnostic confidence. TLR strongly correlated with TSR and TBR, while TBR showed near-perfect, acquisition-independent agreement (R = 0.99, R² = 0.98). High coefficients of determination (R² ≥ 0.84) confirmed the reliability of these indices, with TBR as the most robust surrogate. Qualitative analysis showed no significant difference in mean image quality scores across acquisition durations.

Shortened half-dose ¹⁸F-FDG PET-CT acquisitions are feasible. Despite the study's limited sample size and demographic scope, a 66 s/bp protocol at 1.85 MBq/kg offers the optimal balance of efficiency, safety, and diagnostic performance.

In clinical oncology, the 66 s/bp scan duration offers an optimal balance of efficiency and safety, making it ideal for routine PET imaging in LC patients requiring repeated scans.