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The patients fasted for at least 6 h before the [¹⁸F]-FDG PET/CT scan. The blood glucose level of all patients was < 7.0 mmol/L (the blood glucose of patients with diabetes was < 11.1 mmol/L). Patients who underwent [⁶⁸Ga]Ga-FAPI-04 PET/CT examinations did not require special preparation. The intravenous doses of [¹⁸F]-FDG and [⁶⁸Ga]Ga-FAPI-04 were weight-adjusted (3.7 and 1.85 MBq/kg, respectively). Patients were required to drink 1,000 mL of water to fill their stomach before examination and to urinate before the PET/CT scan. 60 minutes after intravenous injection (15 (link)), PET/CT examination (uMI780, United Imaging Healthcare) was performed from the head (separate head scans for patients with suspected brain metastasis) to the middle thigh. CT scanning was performed with the following parameters: tube voltage, 120 kV; current, 120 mA; layer thickness, 3.00 mm. The scans were reconstructed using a matrix size of 128×128 pixels. Data were uploaded to a post-processing workstation (version R002, uWS-MI, United Imaging Healthcare) for processing. All PET images required iterative reconstructions.

All patients underwent PET/CT using a dedicated PET/CT system (United Imaging, uMI780, China) at 60 ± 5 min after intravenous injection of 2–2.3 MBq/kg ⁶⁸Ga-PSMA-11 synthesized as previously described [18 (link)]. A non-enhanced CT scan (120 kV, mA modulation, pitch 0.988, slice thickness 3.0 mm, increment 1.5 mm) was obtained followed by a whole-body PET scan (3 min/bed, field of view 60 cm) in 3D mode (matrix 256 × 256) from the vertex to the proximal legs. Datasets were fully corrected for random coincidences, scatter radiation, and attenuation. PET image reconstruction used the ordered-subsets expectation maximization method. Attenuation corrections of the PET images were performed using data from CT scans. PET/CT fusion was performed using a workstation (uWS-MI, United Imaging).
The training and test sets were reviewed independently by two nuclear medicine radiologists (F.W and S.Y.A, with 10 and 8 years of experience in prostate PET/CT, respectively). The radiologists were completely blinded to the clinical information and were encouraged to decide if an intraprostatic PCa lesion was present or not using a four-point scale: 1, definite BPD; 2, probable BPD; 3, probable PCa; and 4, definite PCa. Inter-reader agreement was evaluated using the Cohen's kappa coefficient. Agreement between the radiologists was reached by consensus.

All PET imaging was performed using the PET/CT scanner (uMI780, United Imaging Healthcare). Detailed configuration of this scanner can be found in previous study [24 (link)]. The resulting data were provided to a post-processing workstation (Version R002, uWS-MI, United Imaging Healthcare). The doses of ⁶⁸Ga-DOTATATE via intravenous injection were 3.7 and 2.0 MBq/kg, respectively. The patients were instructed to drink adequate water, rest at a quiet and suitable temperature for 45–60 min after intravenous injection of imaging agent, empty the bladder, and perform CT scans from the top of the head to the upper middle of the thighs. Scanning parameters were as follows: tube voltage = 120 kV, tube current = 100 mAs, and layer thickness = 6 mm. After the completion of CT scanning, PET 3D acquisition was performed with 3 min/bed, 9–11 total beds subsequently. After the acquisition, attenuation correction was performed with CT data. PET images were reconstructed iteratively to generate cross-sectional, coronal plane, sagittal plane sectional images and 3D projected images.

All PET/CT images were anonymous and transferred to a commercial medical image processing workstation (uWS-MI, United Imaging Healthcare) for analysis.

All of the patients underwent PET/CT using a dedicated PET/CT system (United Imaging, uMI780, China) at 60 ± 5 min after intravenous injection of 2–2.3 MBq/kg 68Ga-PSMA-11 synthesized as previously described (17 (link)). A nonenhanced CT scan (120 kV, mA modulation, pitch 0.988, slice thickness 3.0 mm, increment 1.5 mm) was obtained, followed by a whole-body PET scan (3 min/bed, field of view 60 cm) in 3D mode (matrix 256 × 256) from the vertex to the proximal legs. The datasets were fully corrected for random coincidences, scatter radiation, and attenuation. For PET image reconstruction, the ordered-subsets expectation maximization method was used. Attenuation corrections of the PET images were performed using data from the CT scans. PET/CT fusion was performed using a workstation (uWS-MI, United Imaging).
The volumes of interest (VOIs) for the prostate gland were accurately delineated and segmented slice by slice using 3D Slicer software (version: 4.1.1.0; www.slicer.org) by a highly experienced nuclear medicine radiologist (FW) with 20 years of expertise in prostate PET/CT. The radiologist, blinded to the clinical information, performed this task by carefully analyzing the PET images and factoring in the corresponding CT scan for accurate localization and segmentation of the VOIs.

In the retrospective study of this work, the image quality was quantitatively assessed on an advanced workstation (uWS-MI, United Imaging Healthcare). For each patient, a volume of interest (VOI) with a diameter of 30 ± 3 mm was manually drawn at the same position and the slice on a homogeneous area of the right liver lobe. The SUVmean and standard deviation (SD) within the VOI were recorded. The liver COV, as a measure of background noise, was obtained by dividing the SD by the SUVmean. Regarding the lesions, SUVmax of the identified FDG-avid lesions was measured by placing a VOI to encompass the whole lesion. Thus, tumor-to-liver ratio (TLR), as a measure of image contrast, was obtained by dividing the lesion SUVmax by the liver SUVmean.