Table 3.
Subjective image quality and noise per reconstruction method and per dose level. For the image quality, the average score of the two observers was used. Those data are presented as median [interquartiles]. Also, the number of examinations [%] with unacceptable image quality (score 1 or 2) is shown per observer. The noise is presented as medians (interquartiles)
| Subjective image quality | Unacceptable image quality | Renal cortex (right) | Renal cortex (left) | Aorta | Retroperitoneal fat | Air | ||
|---|---|---|---|---|---|---|---|---|
| Routine dose | Obs. 1 | Obs. 2 | ||||||
| FBP | 3 [3–3] | 0 [0] | 9 [47] | 53.3 (48.6–61.2) Reference | 51.8 (42.8–60.0) Reference | 56.5 (50.3–68.8) Reference | 54.7 (45.7–61.4) Reference | 23.5 (22.4–26.3) Reference |
| iDose4 | 4 [4–4]* | 0 [0] | 1 [5] | 32.2 (29.0–37.1)* | 32.4 (28.5–36.1)* | 37.4 (30.8–42.0)* | 35.6 (29.6–37.3)* | 17.7 (16.9–17.7)* |
| MIR (BR) | 4 [4–4]* | 0 [0] | 0 [0] | 10.2 (9.5–11.6)* | 11.5 (10.0–12.3)* | 11.7 (10.0–13.6)* | 13.0 (11.4–14.8)* | 6.6 (5.7–7.3)* |
| MIR (ST) | 4 [4–4]* | 0 [0] | 0 [0] | 7.2 (6.2–8.2)* | 7.5 (7.0–8.0)* | 7.7 (6.0–9.5)* | 9.1 (7.6–10.9)* | 4.2 (4.0–7.3)* |
| 40% reduced dose | ||||||||
| FBP | 3 [3–3] | 3 [16] | 15 [79] | 70.0 (62.8–83.5)* | 72.2 (63.5–79.3)* | 77.3 (69.6–97.0)* | 74.8 (55.6–83.8)* | 31.7 (25.9–37.7)* |
| iDose4 | 3 [3–4] | 0 [0] | 8 [42] | 37.8 (34.6–39.7)* | 38.0 (34.2–42.4)* | 44.0 (37.7–45.7)* | 39.4 (36.2–44.2)* | 23.6 (20.0–28.6) |
| MIR (BR) | 4 [3–4]* | 0 [0] | 4 [21] | 12.4 (10.2–12.8)* | 11.6 (9.8–14.4)* | 13.6 (11.4–15.7)* | 13.5 (11.2–17.6)* | 7.5 (5.9–8.6)* |
| MIR (ST) | 4 [3–4]* | 0 [0] | 2 [11] | 8.4 (7.3–9.8)* | 9.3 (7.3–10.7)* | 10.2 (9.4–11.3)* | 10.5 (8.9–14.3)* | 5.6 (4.9–7.9)* |
| 60% reduced dose | ||||||||
| FBP | 2 [2–3]* | 13 [68] | 19 [100] | 97.5 (84.1–106.7)* | 88.7 (77.4–120.8)* | 103.1 (89.8–115.0)* | 103.7 (85.6–111.1)* | 42.2 (33.0–49.8)* |
| iDose4 | 3 [3–3] | 0 [0] | 6 [32] | 40.6 (38.9–45.1)* | 39.3 (35.8–48.1)* | 46.2 (40.2–52.5)* | 45.6 (38.3–49.5)* | 27.4 (24.5–37.2)* |
| MIR (BR) | 4 [3–4] | 1 [5] | 7 [37] | 13.7 (11.2–15.6)* | 12.9 (10.8–14.6)* | 15.2 (13.1–17.4)* | 14.2 (12.5–16.4)* | 8.5 (7.3–11.7)* |
| MIR level 2 (ST) | 3 [3–4]* | 0 [0] | 2 [5] | 10.1 (8.3–12.0)* | 9.2 (8.6–10.7)* | 11.6 (10.1–13.3)* | 10.2 (9.2–12.3)* | 7.2 (5.3–10.5)* |
| 80% reduced dose | ||||||||
| FBP | 1 [1–1]* | 19 [100] | 19 [100] | 160.9 (136.0–187.6)* | 168.7 (131.0–192.9)* | 184.7 (152.8–203.3)* | 165.6 (146.9–187.5)* | 57.2 (36.8–63.2)* |
| iDose4 | 2 [2–3]* | 11 [58] | 17 [90] | 47.4 (45.3–64.7) | 51.0 (45.4–59.0) | 50.6 (44.3–63.6) | 51.8 (48.0–64.7) | 33.4 (26.8–41.7)* |
| MIR (BR) | 3 [3–3]* | 4 [21] | 14 [74] | 15.9 (12.9–17.2)* | 14.6 (12.3–17.8)* | 17.1 (15.6–19.4)* | 15.2 (13.9–19.1)* | 9.8 (8.8–15.4)* |
| MIR (ST) | 3 [2–3]* | 6 [32] | 13 [69] | 12.4 (9.9–13.9)* | 11.8 (10.3–14.7)* | 14.4 (11.8–16.0)* | 12.5 (10.5–15.7)* | 9.2 (6.4–15.1)* |
*Significant difference compared to the reference (p<0.0125)
FBP filtered back projection, HIR hybrid iterative reconstruction, MIR model-based iterative reconstruction, BR body routine, ST soft tissue, Obs observer