{
  "abstract": "Introduction PET-CT has shown potential as a research tool for characterising heterogeneity in TB infection. Its prospective application requires standardisation of imaging protocols, interpretation and analysis to improve generalisability and enable data integration across discrete cohorts. We evaluated a semi-automated approach using open-source software to minimise inter-operator variability in image interpretation. We further assessed the impact of normalising PET metrics to a physiological reference organ and explored associations between metabolic change and prospective outcomes in recent pulmonary TB contacts.Methods We quantified nineteen PET-CT scans with thoracic FDG uptake from eleven QuantiFERON-TB Gold-Plus (QFT)-positive TB contacts enrolled in a prospective observational study. Eight contacts underwent serial imaging at 3 months, providing data to evaluate metabolic trajectory. Imaging was analysed using a clinical platform (XD3) and 3D Slicer 5.4.0, an open-source research imaging platform that provides semi-automated segmentation and automated liver quantification. A primary reader extracted SUV-based and volumetric PET metrics using both platforms. A second reader independently extracted the data using 3D Slicer. Extracted metrics included maximum and mean standardised uptake value (SUVmax and SUVmean), metabolic volume (MV), total lesion glycolysis (TLG) in intrathoracic lymph nodes (ITLNs), and liver SUVmean. PET metrics were normalised to liver SUVmean + 3 standard deviations (SDs).Results All ITLN PET metrics from 3D Slicer showed strong agreement with the clinical platform (concordance correlation coefficient [CCC]>0.90) and moderate agreement with liver SUVmean+3SDs (CCC=0.85). Inter-reader agreement using 3D Slicer was excellent (intraclass correlation coefficient [ICC]>0.90). Three participants received TB treatment during the study period for incident TB; in two, TB was microbiologically confirmed, and in one, a new lung lesion developed on follow-up imaging that resolved with treatment. All three demonstrated increasing metabolic trajectory from baseline to 3 months when normalised to liver uptake ( figure 1). In one case, liver normalisation revealed increasing metabolic activity otherwise obscured by lower physiological FDG uptake on the second scan. Contacts remaining healthy showed decreasing PET metrics.Abstract M34 Figure 1Conclusions Semi-automated PET quantification can reduce inter-operator variability. Normalising to reference organs enhances analytical sensitivity. We report preliminary findings that the metabolic trajectory in early infection is a promising indicator of prospective TB risk.",
  "authors": [
    {
      "affiliations": [
        "NIHR Respiratory Biomedical Research Centre, University of Leicester, Leicester, UK"
      ],
      "name": "JW Kim"
    },
    {
      "affiliations": [
        "University Hospitals of Leicester NHS Trust, Leicester, UK"
      ],
      "name": "A Kamil"
    },
    {
      "affiliations": [
        "University Hospitals of Leicester NHS Trust, Leicester, UK"
      ],
      "name": "J Lee"
    },
    {
      "affiliations": [
        "University Hospitals of Leicester NHS Trust, Leicester, UK"
      ],
      "name": "I Novsarka"
    },
    {
      "affiliations": [
        "NIHR Respiratory Biomedical Research Centre, University of Leicester, Leicester, UK"
      ],
      "name": "P Haldar"
    }
  ],
  "title": "M34 Semi-automated quantification of PET-CT in TB contacts and its association with prospective outcomes",
  "uid": "ea58f516-53e4-54cb-8a18-58600303e2cb"
}