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Table 1 Percentage of emphysema using the -950 HU threshold and the perc15 method at different dose levels reconstructed with FBP, HIR and MIR

From: Emphysema quantification using chest CT: influence of radiation dose reduction and reconstruction technique

  -950 HU (%) ICC (95% CI) Perc15 (HU-value) ICC (95%CI)
Routine dose
 FBP 5.1 (1.7–8.4) NA -923 (-936 – -895) NA
 HIR 1.5 (0.1–4.5)a 0.63 (0.00–0.88) -914 (-927 – -881)a 0.91 (0.00–0.98)
 MIR 0.9 (0.0–3.6)a 0.50 (0.00–0.80) -913 (-926 – -879)a 0.88 (0.01–0.97)
45% reduced dose
 FBP 8.0 (3.3–12.4)a 0.83 (0.00–0.96) -932 (-944 – -898)a 0.93 (0.39–0.98)
 HIR 2.5 (0.2–5.1)a 0.79 (0.01–0.94) -916 (-929 – -875)a 0.89 (0.28–0.97)
 MIR 1.2 (0.0–3.1)a 0.51 (0.00–0.81) -913 (-927 – -867)a 0.83 (0.07–0.95)
60% reduced dose
 FBP 10.2 (5.5–14.7)a 0.63 (0.00–0.89) -940 (-949 – -912)a 0.77 (0.00–0.94)
 HIR 2.7 (0.5–6.2)a 0.83 (0.24–0.95) -917 (-931 – -881)a 0.87 (0.62–0.95)
 MIR 1.3 (0.0–3.2)a 0.49 (0.00–0.79) -911 (-927 – -874)a 0.80 (0.28–0.93)
75% reduced dose
 FBP 14.3 (9.7–19.6)a 0.42 (0.00–0.79) -948 (-961 – -925)a 0.59 (0.00–0.88)
 HIR 3.5 (0.7–8.1)a 0.92 (0.76–0.97) -921 (-935 – -878)a 0.94 (0.81–0.98)
 MIR 0.9 (0.0–4.2)a 0.47 (0.00–0.78) -914 (-927 – -869)a 0.84 (0.16–0.95)
  1. Values represent the median (interquartile range). The ICC compares with the reference standard, namely FBP at routine dose
  2. aStatistically significant difference compared to FBP at routine dose with a Bonferroni corrected p value of 0.017
  3. FBP filtered back projection, HIR hybrid iterative reconstruction, ICC intraclass correlation coefficient, MIR model-based iterative reconstruction