Table 1.
Percentage of emphysema using the -950 HU threshold and the perc15 method at different dose levels reconstructed with FBP, HIR and MIR
| -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) |
Values represent the median (interquartile range). The ICC compares with the reference standard, namely FBP at routine dose
aStatistically significant difference compared to FBP at routine dose with a Bonferroni corrected p value of 0.017
FBP filtered back projection, HIR hybrid iterative reconstruction, ICC intraclass correlation coefficient, MIR model-based iterative reconstruction