Table 3.
Bivariate analysis of categorical variables and localization errors a
| Variable | Categories | Frequency (%) | EPLE | TPLE | ||
|---|---|---|---|---|---|---|
| Median | P | Median | P | |||
| Planning scan modality | MRI | 404 (46.7) | 1.53 | 0.351 | 3.01 | 0.035 b |
| CT | 462 (53.3) | 1.57 | 2.80 | |||
| Planning software | Medtronic | 682 (78.8) | 1.54 | 0.463 | 2.93 | 0.594 |
| Brainlab | 184 (21.2) | 1.54 | 2.96 | |||
| Electrode direction | Oblique | 594 (68.6) | 1.50 | 0.023 b | 2.89 | 0.029 b |
| Orthogonal | 272 (31.4) | 1.66 | 3.01 | |||
| Electrode contacts | 5 | 52 (6.4) | 1.63 | 0.856 | 2.63 | 0.433 |
| 8 | 173 (21.4) | 1.48 | 2.70 | |||
| 10 | 148 (18.3) | 1.56 | 2.82 | |||
| 12 | 137 (16.9) | 1.50 | 2.90 | |||
| 15 | 122 (15.1) | 1.61 | 3.13 | |||
| 18 | 178 (22.0) | 1.52 | 3.12 | |||
| Surgeon | A (S) | 239 (27.6) | 1.61 | 0.517 | 2.62 | 0.128 |
| B (D) | 59 (6.8) | 1.46 | 2.77 | |||
| C (K) | 50 (5.8) | 1.61 | 3.29 | |||
| D (S + V) | 225 (26.0) | 1.48 | 2.85 | |||
| E (D + V) | 8 (0.9) | 0.90 | 2.51 | |||
| A + C (S + K) | 75 (8.7) | 1.68 | 3.00 | |||
| B + C (D + K) | 91 (10.5) | 1.52 | 3.30 | |||
| A + B (D + S) | 119 (13.7) | 1.61 | 3.00 | |||
| Temporal pole | Yes | 124 (14.3) | 1.48 | 0.063 | 2.71 | 0.002 b |
| No | 742 (85.7) | 1.56 | 3.00 | |||
| Screw length | 20 mm | 36 (11.0) | 1.24 | 0.003 b | 2.51 | 0.018 b |
| 25 mm | 223 (68.4) | 1.57 | 3.14 | |||
| 30 mm | 55 (16.9) | 1.91 | 3.20 | |||
| 35 mm | 12 (3.7) | 3.26 | 4.13 | |||
| Intracranial bending | No | 771 (89.0) | 1.52 | <0.001 b | 2.74 | <0.001 b |
| Yes | 95 (11.0) | 1.97 | 5.65 | |||
| Quality of registration | Optimal | 777 (89.7) | 1.52 | 0.001 b | 2.77 | <0.001 b |
| Suboptimal | 83 (9.6) | 2.01 | 4.17 | |||
| Bad | 6 (0.7) | 1.94 | 5.13 | |||
aEPLE, entry point localization error; TPLE, target point localization error; MRI, magnetic resonance imaging; CT, computed tomography. None of the variables are normally distributed (Shapiro-Wilk normality test p-values are all < 0.001). A Kruskal-Wallis H-test or Mann-Whitney U-test was performed for all variables
bSignificant