Primary Sjögren's syndrome (pSS) is a chronic autoimmune exocrinopathy characterized by lymphocytic infiltration, progressive destruction of salivary gland acini, and varying degrees of functional impairment and fibrosis. Conventional imaging provides limited ability to simultaneously evaluate glandular function and inflammatory activity, leading to challenges in disease staging and treatment decision-making. This study explores a conceptual dual-tracer imaging framework using PSMA PET and FAPI PET to delineate complementary biological processes in pSS.
Age 18-80 years;
Fulfillment of the 2016 ACR-EULAR Classification Criteria for pSS at enrollment. OR diagnosis of a solid tumor scheduled for FAPI PET imaging
Combined with tumors or other connective tissue diseases (for SS group);
Patients who are currently using hormones/biological agents (for both groups)；
Pregnancy or lactation
Parallel
⁶⁸Ga-PSMA PET/CT
Diagnostic testPSMA PET imaging performed for clinical evaluation in prostate cancer patients, used as a comparator for physiologic salivary gland PSMA uptake.
⁶⁸Ga-FAPI PET/CT
Diagnostic testFAPI PET imaging to assess inflammatory activity (FAPI) in patients with primary Sjögren's syndrome.
Difference in Salivary Gland PSMA Uptake Across Groups
Quantitative comparison of PSMA PET uptake parameters (SUVmax, SUVmean) of the parotid glands among three groups: pSS patients, individuals with normal salivary glands, and prostate cancer patients.
Multiglandular PSMA Uptake Comparison
Evaluation of PSMA PET uptake (SUVmax, SUVmean) in the parotid, submandibular, and lacrimal glands across the same study groups.
Correlation Between PSMA Uptake and Clinical Indicators
Correlation of salivary gland PSMA SUV values with clinical, immunological, and functional markers of pSS, including ESR, CRP, IgG, RF, anti-SSA/SSB titers, unstimulated whole salivary flow rate, sialography findings, ESSDAI, and ESSPRI scores.
Quantitative and Spatial Relationship Between PSMA and FAPI Uptake Definition
1. Quantitative correlation: Association between PSMA SUV and FAPI SUV in the same glands. 2. Spatial co-localization: Overlap or complementarity of low-PSMA and high-FAPI regions within individual glands using image fusion and voxel-based analysis (e.g., Dice coefficient).
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