TABLE 3.
Scan Length and Dose Estimates
| Scanner 1 (Aquilion 64) | Scanner 2 (Revolution CT) | Scanner 3 (SOMATOM Force) | All Scanners | |
|---|---|---|---|---|
| Study cohort | n=297 | n=152 | n=46 | n=495 |
| Original scan length (cm) | 27.1±3.0b | 26.4±2.9 | 25.6±3.3b | 26.8±3.0 |
| Reduced scan length (cm) | 14.5±2.5ab | 13.1±2.3a | 12.4±2.2b | 13.9±2.6 |
| Delta scan length (%) | −46.3±8.2ab | −50.3±8.7a | −51.3±8.5b | −48.0±8.6 |
| Original CTDI (mGy) | 21.3±8.8ab | 3.6±2.2ac | 5.5±3.3bc | 14.4±11.0 |
| Original DLP (mGy*cm) | 473.1±236.9ab | 121.0±77.1ac | 179.6±106.5bc | 338.0±253.5 |
| Original effective dose (mSv) | 6.9±3.5ab | 1.8±1.1ac | 2.6±1.6bc | 4.9±3.7 |
| Random sample | n=10 | n=10 | n=10 | n=30 |
| Delta ∑mA (%) | −48.4±13.8 | −58.7±9.3 | −61.7±17.3 | −56.3±14.6 |
| Prescan dose estimates | — | n=10 | n=10 | n=20 |
| Delta scan length (%) | — | −44.1±4.7 | −47.0±3.6 | −45.5±4.3 |
| Delta CTDI (%) | — | −6.2±23.0 | −24.4±8.5 | −15.3±19.3 |
| Delta DLP (%) | — | −45.6±8.4 | −50.6±9.9 | −48.1±9.3 |
Numbers are mean±SD. All parameters from the helical scan only (ie, without topogram or bolus tracking).
Prescan dose estimates were calculated on topograms of 20 different patients (not part of the main study cohort). In the study cohort, Games-Howell post-hoc analysis revealed significant differences between scanners 1 and 2 (a), 1 and 3 (b), and 2 and 3 (c).
∑mA indicates sum of mA extracted per slice over the respective scan range (this estimate takes dose modulation into account, but not overranging) calculated in a subset of the main study cohort (random sample).