Early 10-Minute Postinjection [¹⁸F]F-FAPI-42 uEXPLORER Total-Body PET/CT Scanning Protocol for Staging Lung Cancer Using HYPER Iterative Reconstruction

Abstract

Sensitive detection of small metastatic lesions, which is highly dependent on lesion visualization, is crucial for staging lung cancer. We investigated the potential benefit of HYPER Iterative for improving the visualization of small metastatic lesions of lung cancer on early ¹⁸F-labeled fibroblast activation protein inhibitor (FAPI) PET/CT. Methods: A total of 19 patients with lung cancer underwent a 60-min [¹⁸F]F-FAPI-42 dynamic total-body uEXPLORER PET/CT scan. PET images with a 5-min acquisition time were extracted at 10, 30 min, and 60 min after tracer injection. Ordered-subset expectation maximization (OSEM) and HYPER Iterative were used for image reconstruction. SUV_max, tumor-to-liver ratio, tumor-to-blood ratio, and tumor–to–adjacent-nontumor ratio were calculated and compared between the 2 reconstruction methods and at 10, 30, and 60 min after injection. Results: All HYPER and OSEM PET images were of high quality, with HYPER PET images showing superior clarity. Small positive lesions (maximum diameter, ≤1 cm) were depicted clearer on HYPER PET than on OSEM PET images at all time points, particularly at 10 min after injection, where 16.4% of lesions were poorly visualized on OSEM PET but clearly depicted on HYPER PET images. The tumor-to-liver ratio, tumor-to-blood ratio, and tumor-to-nontumor ratio at 10, 30, and 60 min after injection scan on HYPER PET images were significantly higher than those on OSEM images at corresponding time points (P ≥ 0.05 for all comparisons). SUV_max was more than 2-fold greater in large positive lesions (maximum diameter, >1.0 cm) than in small positive lesions (maximum diameter, ≤1 cm) on both OSEM and HYPER PET images at 10, 30, and 60 min after injection (P < 0.05 for all comparisons). The visualization of large positive lesions was not significantly affected by reconstruction methods or scan times. Conclusion: HYPER Iterative reconstruction enhanced the visualization of small metastatic lesions in lung cancer when compared with conventional OSEM, enabling effective early imaging using [¹⁸F]F-FAPI-42 uEXPLORER total-body PET/CT at 10 min after tracer injection.