Diagnostic performance of original and measured-duration protocolsa
| Estimated Duration (n = 151) | Measured Duration (n = 53) | P Value | Adjusted P Value | |
|---|---|---|---|---|
| Exposure and dose | ||||
| Exposure time (sec) | 15.75 (8.25–25.5) | 10.0 (8–12) | <.001 | <.001b |
| No. of volumes | 31 (26–36) | 19 (19–19) | ||
| Dose-length product (mGy × cm) | 3021 (2536–3502) | 1473 (1459–1526) | ||
| Volume CT dose index (mGy) | 185 (162–223) | 88.9 (88.9–88.9) | ||
| Effective dose (mSv) | 6.9 (5.8–8.0) | 3.4 (3.4–3.5) | ||
| Study quality | ||||
| Maximum venous enhancement (HU) | 372 (352–392) | 324 (294–353) | .019 | .076 |
| Adequate time coverage (No.) | 134 (88.7%) | 49 (92.5%) | .444 | 1.00 |
| Quality score | 5 (5–5) | 5 (5–5) | .837 | 1.00 |
| No. of prearterial volumes | 6 (4–10) | 0 (0–1) | <.001c | <.001b,c |
| No. of postpeak venous volumes | 2 (0–6) | 0 (0–2) | <.001c | <.001b,c |
| Diagnostic performance | ||||
| Positive findings (No.) | 58 (38.4%) | 21 (39.6%) | ||
| No. having DSA | 56 (37.1%) | 22 (41.5%) | ||
| Intermodality concordance between 4D-CTA and DSA (No.) | 51 (91.0%) | 22 (100.0%) | ||
| Cohen κ statistic | κ = 0.88 | κ = 1.0 |
↵a Noncount values are shown as median (interquartile range), except for exposure time shown as median (range) and enhancement shown as mean (95% CI). Values for dose-length product include the entire examination, including test-bolus acquisition. CT dose index values include only whole-head acquisitions.
↵b Significant at the 5% level after Bonferroni correction.
↵c Post hoc test.