Image quality and radiation dose reduction in chest CT in pulmonary infection

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Purpose: To evaluate the effect of dose reduction with iterative reconstruction (IR) on image quality of chest CT scan comparing two protocols. Materials and methods: Fifty-nine patients were enrolled. The two CT protocols were applied using Iterative Reconstruction (ASIR™) 40% but different noise indexes, recording dose-length product (DLP) and volume computed tomography dose index (CTDIvol). The subjective IQ was rated based on the distinction of anatomic details using a 4-point Likert scale based on the European Guidelines on Quality Criteria for CT. For each patient, two single CTs, at enrollment (group 1) and at follow-up after lowering the dose (group 2), were evaluated by two radiologists evaluating, for each examination, five different lung regions (central zone—CZ; peripheral zone—PZ; sub-pleural region—SPR; centrilobular region—CLR; and apical zone—AZ). An inter-observer agreement was expressed by weighted Cohen’s kappa statistics (k) and intra-individual differences of subjective image analysis through visual grading characteristic (VGC) analysis. Results: An average 50.4% reduction in CTDIvol and 51.5% reduction in DLP delivered were observed using the dose-reduced protocol. An agreement between observers evaluating group 1 CTs was perfect (100%) and moderate to good in group 2 examinations (k-Cohen ranging from 0.56 for PZ and AZ to 0.70 for SPR). In the VGC analysis, image quality ratings were significantly better for group 1 than group 2 scans for all regions (AUCVGC ranging from 0.56 for CZ to 0.62). However, disagreement was limited to a score 4 (excellent)-to-score 3 (good) IQ transition; apart from a single case in PZ, both the observers scored the IQ at follow-up as 2 (sufficient) starting from a score 4 (excellent). Conclusion: Dose reduction achieved in the follow-up CT scans, although a lower IQ still allows a good diagnostic confidence.

Original languageEnglish
Pages (from-to)451
Number of pages460
JournalRadiologia Medica
Issue number5
Publication statusPublished - May 1 2020


  • Chest
  • Computerized tomography
  • Image quality
  • Iterative reconstruction
  • Radiation dose

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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