The earliest optimal timing for total-body 68Ga-fibroblast activation protein inhibitor-04 PET scans: an evidence-based single-centre study

• Published in: European radiology 2024-07, Vol.34 (7), p.4550-4560
• Main Authors: Zheng, Zhe, Gao, Huaping, Lin, Yu, Yu, Haojun, Mao, Wujian, Yang, Runjun, He, Yibo, Chen, Xueqi, Wu, Ha, Hu, Pengcheng, Shi, Hongcheng
• Format: Article
• Language: English
• Subjects: Background noise; Computed tomography; Diagnostic Radiology; Fibroblast activation protein; Fibroblasts; Image acquisition; Image quality; Image reconstruction; Imaging; Inhibitors; Injection; Internal Medicine; Intervals; Interventional Radiology; Lesions; Medical imaging; Medicine; Medicine & Public Health; Metastases; Neuroradiology; Nuclear Medicine; Positron emission; Positron emission tomography; Proteins; Radiology; Signal to noise ratio; Statistical analysis; Tumors; Ultrasound; Windows (intervals)
• ISSN: 1432-1084; 0938-7994; 1432-1084
• DOI: 10.1007/s00330-023-10264-4

Objectives To investigate the earliest optimal timing for positron emission tomography (PET) scans after 68 Ga-fibroblast activation protein inhibitor-04 ([ 68 Ga]Ga-FAPI-04) injection. Methods This prospective study enrolled patients who underwent 60-min dynamic 68 Ga-FAPI-04 total-body PET/CT scans; the images were reconstructed at 10-min intervals (G0-10, G10-20, G20-30, G30-40, G40-50, and G50-60), and the [ 68 Ga]Ga-FAPI-04 uptake patterns were evaluated. The standardised uptake value (SUV), liver signal-to-noise ratio (SNR), and lesion-to-background ratios (LBRs) for different time windows were calculated to evaluate image quality and lesion detectability. The period from 30 to 40 min was then split into overlapping 5-min intervals starting 1 min apart for further evaluation. G50-60 was considered the reference. Results A total of 30 patients with suspected malignant tumours were analysed. In the images reconstructed over 10-min intervals, longer acquisition times were associated with lower background uptake and better image quality. Some lesions could not be detected until G30-40. The lesion detection rate, uptake, and LBRs did not differ significantly among G30-40, G40-50, and G50-60 (all p  > 0.05). The SUVmean and LBRs of primary tumours in the reconstructed images did not differ significantly among the 5-min intervals between 30 and 40 min; for metastatic and benign lesions, G34-39 and G35-40 showed significantly better SUVmean and LBR values than the other images. The G34-39 and G50-60 scans showed no significant differences in uptake, LBRs, or detection rates (all p  > 0.05). Conclusion The earliest optimal time to start acquisition was 34 min after injection of half-dose [ 68 Ga]Ga-FAPI-04. Clinical relevance statement This study evaluated 68 Ga-fibroblast activation protein inhibitor-04 ([ 68 Ga]Ga-FAPI-04) uptake patterns by comparing the image quality and lesion detection rate with 60-min dynamic [ 68 Ga]Ga-FAPI-04 total-body PET/CT scans and identified the earliest optimal scan time after [ 68 Ga]Ga-FAPI-04 injection. Key Points • A prospective single-centre study showed that the earliest optimal time point to start acquisition was 34 min after injection of half-dose [ 68 Ga-fibroblast activation protein inhibitor-04 ( 68 Ga]Ga-FAPI-04) . • There were statistically significant differences in standardised uptake value, lesion-to-background ratios, and lesion detectability between scans before and after 34 min from the injection of [ 68 Ga]