Table 2.
Effect of scan length on radiation dose
| Patient characteristics | All scans (n = 90) | Scan length ≤ 4 cm (n = 26) | Scan length > 4 cm (n = 64) | P-value | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Body mass index (kg/m2) | 90 | 21.1 | (19.5; 22.4) | 26 | 21.2 | (19.9; 22.4) | 64 | 21.0 | (19.4; 22.5) | 0.621 |
| Weight (kg) | 90 | 62.0 | (57.5; 67.9) | 26 | 62.2 | (58.0; 68.0) | 64 | 62.0 | (57.3; 67.8) | 0.793 |
| Height (cm) | 90 | 172.0 | (168.0; 177.5) | 26 | 170.5 | (166.0; 177.5) | 64 | 173.0 | (169.0; 177.2) | 0.207 |
| Scan characteristics | ||||||||||
| CT scan length (cm) | 90 | 4.9 | (4.2; 5.4) | 26 | 4.1 | (3.9; 4.2) | 64 | 5.1 | (4.8; 5.7) | < 0.001 |
| Total humeral head inclusion (R&L) (cm) | 90 | 0.4 | (0.0; 2.3) | 26 | 0.3 | 90.0; 1.1) | 64 | 0.1 | (0.0; 2.8) | 0.169 |
| Right humeral head inclusion (cm) | 90 | 0.0 | (0.0; 1.2) | 26 | 0.0 | (0.0; 0.4) | 64 | 0.4 | (0.0; 1.7) | 0.028 |
| Left humerus head inclusion (cm) | 90 | 0.5 | (0.0; 1.0) | 26 | 0.5 | (0.0; 0.4) | 64 | 0.1 | (0.0; 1.2) | 0.368 |
| Humeral head position, n (%) | 90 | 26 | 64 | |||||||
| Arms in | 55 | (61.1) | 16 | (61.5) | 39 | (60.9) | ||||
| Arms out | 35 | (38.9) | 10 | (38.5) | 25 | (39.1) | 0.958 | |||
| Scan length/humeral head inclusion | 90 | 26 | 64 | |||||||
| SL: ≤4 cm, Arms out | 10 | (11.1) | 10 | (38.5) | 0 | (0.0) | ||||
| SL: ≤4 cm, Arms in | 16 | (17.8) | 16 | (61.5) | 0 | (0.0) | ||||
| SL: >4 cm, Arms out | 25 | (27.8) | 0 | (0.0) | 25 | (39.1) | < 0.001 | |||
| SL: >4 cm, Arms in | 39 | (43.3) | 0 | (0.0) | 39 | (60.9) | ||||
| Radiation doses | ||||||||||
| Effective CT tube current (mAs) | 90 | 65.5 | (58.0; 81.0) | 26 | 69.0 | (59.0; 83.0) | 64 | 64.5 | (58.0; 78.0) | 0.325 |
| CT dose index (mGy) | 90 | 4.5 | (3.9; 5.5) | 26 | 4.7 | (4.0; 5.6) | 64 | 4.3 | (3.9; 5.3) | 0.306 |
| Dose length product (mGy*cm) | 90 | 30.0 | (27.0; 38.0) | 26 | 28.5 | (24.0; 32.0) | 64 | 32.0 | (28.0; 41.0) | 0.007 |
| Effective dose (mSv) | 90 | 0.4 | (0.4; 0.5) | 26 | 0.4 | (0.3; 0.4) | 64 | 0.4 | (0.4; 0.6) | 0.007 |
Continuous variables are described with median (IQR), p-values obtained by Wilcoxon rank sum test
Categorical variables are shown with number (%) in each category, p-values obtained by Chi-squared test
Fisher’s exact test was additionally calculated if possible (otherwise signed by -), when the expected frequency of one cell was less than 5