{
  "abstract": "Background 18F-Fibroblast activation protein inhibitor ([18F]FAPI) positron emission tomography (PET)/CT is an emerging tool for detecting IgG4-related disease (IgG4-RD). However, standardised quantitative analysis and image scoring present ongoing challenges in patients with IgG4-RD.Purpose To establish organ-specific reference thresholds for IgG4-RD involvement on [ 18F]FAPI PET/CT images, and to develop a novel, clinically applicable scoring system to monitor disease activity in patients with IgG4-RD.Methods This retrospective study recruited 85 patients with IgG4-RD and 10 healthy individuals, all of whom underwent [ 18F]FAPI PET/CT. Organ-specific uptake thresholds were defined as [18F]FAPI uptake greater than the maximal standardised uptake value +3 SD in the corresponding anatomical regions of healthy individuals. Moreover, we developed a novel method, [18F]FAPI PET/CT Activity Score of IgG4-RD (FPAS-IgG4), for scoring disease activity using a logistic regression model with receiver operating characteristics curve analysis.Results Among 85 patients with IgG4-RD, 64 lesions suspected of IgG4-RD involvement were biopsied and 58 (90.6%) of these lesions were positive for IgG4. [ 18F]FAPI PET/CT achieved a sensitivity, specificity and accuracy of 86.2%, 83.3% and 85.9%, respectively, for detecting IgG4-RD based on organ-specific uptake thresholds. The active disease group had a higher FPAS-IgG4 than the inactive disease group (5.2±3.0 vs 1.7±1.3, p<0.0001). FPAS-IgG4 >2 showed a sensitivity of 93.2% and a specificity of 73.1% in distinguishing between active and inactive disease. Multivariable logistic regression analysis demonstrated that FPAS-IgG4 was strongly associated with active IgG4-RD (p=0.001).Conclusion [ 18F]FAPI PET/CT could be a valuable tool for monitoring the activity of IgG4-RD, aiding in disease stratification.",
  "authors": [
    {
      "affiliations": [
        "Department of Nuclear Medicine, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China"
      ],
      "name": "Donghe Chen"
    },
    {
      "affiliations": [
        "Department of Rheumatology, Pujiang branch of the First Affiliated Hospital of Zhejiang University, Jinhua, Zhejiang, China"
      ],
      "name": "Danqing Huang"
    },
    {
      "affiliations": [
        "Department of Rheumatology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China"
      ],
      "name": "Chuanyin Sun"
    },
    {
      "affiliations": [
        "Department of Nuclear Medicine, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China"
      ],
      "name": "Zhenfeng Liu"
    },
    {
      "affiliations": [
        "State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, Hangzhou, Zhejiang, China"
      ],
      "name": "Danhua Zhu"
    },
    {
      "affiliations": [
        "Department of Nuclear Medicine, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China"
      ],
      "name": "Kui Zhao"
    },
    {
      "affiliations": [
        "Department of Nuclear Medicine, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China"
      ],
      "name": "Xinhui Su"
    }
  ],
  "title": "[18F]FAPI PET/CT-based scoring systems for patient assessment in IgG4-related disease",
  "uid": "bf8e49ca-1b86-5b4a-aa6f-e6049d86cbca"
}