To investigate the predictive value of 2-[18F]-fluoro-2-deoxy-D-glucose ([18F]FDG) PET/CT for evaluating primary tumor (PT) and lymph node (LN) responses after neoadjuvant programmed death-ligand 1 (PD-L1) blockade monotherapy in patients with locally advanced esophageal squamous cell carcinoma (LA-ESCC). In the single-arm phase 1b NATION-1907 trial (NCT04215471), 23 patients with LA-ESCC received two cycles of neoadjuvant PD-L1 blockade Adebrelimab followed by surgery. Among these, 18 patients underwent [18F]FDG PET/CT scans both before immunotherapy and prior to surgery. Standardized uptake value corrected for lean body mass (SUL)-derived parameters, including SULmax and SULpeak, were documented for PTs and LNs. Lesions > 1cm3 were segmented using thresholds of 41

To validate the feasibility of one-stop 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) and [68Ga]Ga-fibroblast activation protein inhibitor-04 ([68Ga]Ga-FAPI-04) dual-low-activity-tracer positron emission tomography/computed tomography (PET/CT) at 34 min post-injection of [68Ga]Ga-FAPI-04 and explore its additional value. Thirty pairs of patients with suspected malignancies who underwent dual-tracer imaging were enrolled in this retrospective study. The images were reconstructed at 34–39 and 50–60 min after additional injection of [68Ga]Ga-FAPI-04 (in one-stop FDG-FAPI PET/CT, named PETFDG, PETD34–39, and PETD50–60; in the 2-day protocol, named PETFDG’, PETF34–39, and PETF50−60, respectively). Tumour-to-normal ratios (TNR) of lesions in PETFDG, PETD34−39, and PETD50−60 and TNR of lesions in PETF34−39 and PETF50−60 were evaluated separately. To evaluate the potential added value of one-stop FDG-FAPI PET/CT over the 2-day protocol, TNRs of PETFDG, PETD34−39, and PETD50−60 were compared with PETF34−39. The lesion detectability of the two imaging protocols was evaluated by chi-square test. Comparing FAPI-weighted PET (PETD34−39 and PETD50−60) and single-tracer imaging (PETFDG) in one-stop FDG-FAPI PET/CT, TNRs of FAPI-weighted PET were higher than those of PETFDG. PETD34−39 and PETD50−60 showed similar performance in lesion detectability and TNRs (all P > 0.05). In the 2-day protocol, there are no statistically significant differences in TNRs of all lesions at PETF34−39 and PETF50−60. Comparing one-stop FDG-FAPI PET/CT with the 2-day protocol, TNRs of PETF34−39 were significantly higher than those of PETFDG but lower than those of PETD34−39 and PETD50−60. Lesion detectability in the one-stop FDG-FAPI PET/CT was higher than that in the 2-day protocol. The average radiation dose in one-stop FDG-FAPI PET/CT was significantly lower than that in the 2-day protocol (P<0.001). One-stop FDG-FAPI PET/CT at 34 min could provide sufficient information to meet clinical diagnosis and showed better lesion detectability than that in the 2-day protocol.

Objectives: To investigate the feasibility of paediatric F-18-FDG total-body PET/CT imaging with an ultra-low activity and explore an optimized acquisition time range. Methods: A total of 38 paediatric patients were prospectively enrolled and underwent dynamic total-body PET/CT imaging using ultra-low F-18-FDG activity (0.37 MBq/kg). The 60-minute list-mode raw data were acquired and then reconstructed as static PET images by using 50-51, 50-52, 50-53, 50-54, 50-55, 50-58, 50-60, and 45-60 minutes data, which were noted as G1, G2, G3, G4, G5, G8, G10, and G15, respectively. Image qualities were subjectively evaluated using the Likert scale and were objectively evaluated by the quantitative metrics including standard uptake value (SUV), signal-to-noise ratio (SNR), target-to-background ratio (TBR), and contrast-to-noise ratio (CNR). Results: The injected activity of FDG was 13.38 +/- 5.68 MBq (4.40-28.16 MBq) and produced 0.58 +/- 0.19 mSv (0.29-1.04 mSv) of effective dose. The inter-reader agreement of subjective image quality was excellent (kappa = 0.878; 95% CI, 0.845-0.910). The average scores of image quality for G1-G15 were 1.10 +/- 0.20, 2.03 +/- 0.26, 2.66 +/- 0.35, 3.00 +/- 0.27, 3.32 +/- 0.34, 4.25 +/- 0.30, 4.49 +/- 0.36, and 4.70 +/- 0.37, respectively. All image scores are above 3, and all lesions are detectable starting from G8. SNRs of backgrounds, TBRs, and CNRs were significant differences from the control group before G8 (all P < 0.05). Conclusion: The image quality of the 8 min acquisition for paediatric F-18-FDG total-body PET/CT with an ultra-low activity could meet the diagnostic requirements.

To investigate the earliest optimal timing for positron emission tomography (PET) scans after 68Ga-fibroblast activation protein inhibitor-04 ([68Ga]Ga-FAPI-04) injection. This prospective study enrolled patients who underwent 60-min dynamic 68Ga-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 [68Ga]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. 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). The earliest optimal time to start acquisition was 34 min after injection of half-dose [68Ga]Ga-FAPI-04. This study evaluated 68Ga-fibroblast activation protein inhibitor-04 ([68Ga]Ga-FAPI-04) uptake patterns by comparing the image quality and lesion detection rate with 60-min dynamic [68Ga]Ga-FAPI-04 total-body PET/CT scans and identified the earliest optimal scan time after [68Ga]Ga-FAPI-04 injection. • A prospective single-centre study showed that the earliest optimal time point to start acquisition was 34 min after injection of half-dose [68Ga-fibroblast activation protein inhibitor-04 (68Ga]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 [68Ga]Ga-FAPI-04, but these values did not change further from 34 to 60 min after injection. • With a reasonable acquisition time, the image quality could still meet diagnostic requirements.

To investigate the feasibility of ultra-low-dose CT (ULDCT) reconstructed with the artificial intelligence iterative reconstruction (AIIR) algorithm in total-body PET/CT imaging. The study included both the phantom and clinical parts. An anthropomorphic phantom underwent CT imaging with ULDCT (10mAs) and standard-dose CT (SDCT) (120mAs), respectively. ULDCT was reconstructed with AIIR and hybrid iterative reconstruction (HIR) (expressed as ULDCT-AIIRphantom and ULDCT-HIRphantom), respectively, and SDCT was reconstructed with HIR (SDCT-HIRphantom) as control. In the clinical part, 52 patients with malignant tumors underwent the total-body PET/CT scan. ULDCT with AIIR (ULDCT-AIIR) and HIR (ULDCT-HIR), respectively, was reconstructed for PET attenuation correction, followed by the SDCT reconstructed with HIR (SDCT-HIR) for anatomical location. PET/CT images’ quality was qualitatively assessed by two readers. The CTmean, as well as the CT standard deviation (CTsd), SUVmax, SUVmean, and the SUV standard deviation (SUVsd), was recorded. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared. The image quality of ULDCT-HIRphantom was inferior to the SDCT-HIRphantom, but no significant difference was found between the ULDCT-AIIRphantom and SDCT-HIRphantom. The subjective score of ULDCT-AIIR in the neck, chest and lower limb was equivalent to that of SDCT-HIR. Besides the brain and lower limb, the change rates of CTmean in thyroid, neck muscle, lung, mediastinum, back muscle, liver, lumbar muscle, first lumbar spine and sigmoid colon were −2.15, −1.52, 0.66, 2.97, 0.23, 8.91, 0.06, −4.29 and 8.78%, respectively, while all CTsd of ULDCT-AIIR was lower than that of SDCT-HIR. Except for the brain, the CNR of ULDCT-AIIR was the same as the SDCT-HIR, but the SNR was higher. The change rates of SUVmax, SUVmean and SUVsd were within $$\pm$$ 3% in all ROIs. For the lesions, the SUVmax, SUVsd and TBR showed no significant difference between PET-AIIR and PET-HIR. The SDCT-HIR could not be replaced by the ULDCT-AIIR at date, but the AIIR algorithm decreased the image noise and increased the SNR, which can be implemented under special circumstances in PET/CT examination.

Objective:To explore the feasibility of one-tenth dose 18F-FDG total-body PET/CT (TB PET/CT) in patients with malignant tumors. Methods:A retrospective analysis was carried out on 34 preliminarily diagnosed cancer patients (30 males, 4 females, age (64.0±1.6) years) who underwent one-tenth dose (0.37 MBq/kg) 18F-FDG TB PET/CT examination between April 2020 and September 2022 in Zhongshan Hospital, Fudan University. The raw data were reconstructed into 15 min and initial 2 min PET images (G15 and G2, respectively). A matched cohort of 34 preliminarily diagnosed malignant tumor patients (27 males, 7 females, age (63.3±2.1) years) undergoing full dose (3.70 MBq/kg) 18F-FDG conventional digital PET/CT (C PET/CT) examination with a PET scan rate of 2-3 min/bed position, were analyzed in line with the same pathological types. Signal-to-noise ratios (SNR) of G15, G2 and C PET/CT groups were compared, and based on the pathological results, the detection rates of those 3 groups for lesions were also compared. The χ2 test, independent sample t-test, Mann-Whitney U test, and Wilcoxon rank sum test were used for data analysis. Results:The significant differences in gender, age, body mass index (BMI), blood sugar level and postinjection waiting time between TB PET/CT group and C PET/CT group were not found ( χ2=0.98, t values: 0.08, -1.05, z values: 0.68, 0.41, all P>0.05). The SNR, from G15 to C PET and G2 groups, decreased gradually, which were 16.0(11.3, 20.0), 10.5(8.2, 13.5) and 8.4±0.3 respectively ( z values: 5.09, 3.31, -4.24, all P<0.05). All primary lesions and hepatic metastases were detected by G15 and G2 imaging (100%, 37/37) as well as by C PET/CT (100%, 36/36). The detection rates for lymph node metastasis lesions were 10/15 in the G2/G15 groups, which were higher than the detection rate in the C PET/CT group (64.4%(29/45); χ2=62.03, P=0.002). Conclusion:One-tenth dose 18F-FDG TB PET/CT with a 2-minute acquisition is feasibility in the clinical practice.