68 Chapter 3 Sensitivity and specificity for prediction of feasibility of endovascular treatment, calculated only for those cases where an aneurysm was detected by the observer, are given in table 1b. Table 1b. Sensitivity and specificity of CTA and CEMRA for assessing the feasibility of endovascular treatment of the aneurysm if only the patients harboring aneurysms (as scored by the observer) are considered. Obs = Observer. CTA CEMRA Obs 1 64.5 (45.4 - 80.2) 52.9 (35.5 - 69.1) Sensitivity Obs 2 80.6 (61.9 - 91.9) 63.6 (45.1 - 79.0) Obs 1 82.8 (63.5 - 93.5) 81.8 (63.9 - 92.4) Specificity Obs 2 66.7 (47.1 - 82.1) 70.0 (50.4 - 84.6) If Cohen’s Kappa for feasibility of endovascular treatment is calculated for these cases only, this value decreases to 0.38 for CTA and to 0.46 for CEMRA. The accuracy for measuring the size of an aneurysm is given by the regression lines with the 95% predictive interval in figure 2a-d. Using the regression equation DSA = ɲ + ɴ x (CTA or MRA), the regression coefficients ɴ with 95% CI are given in table 2. ɲ is small (zero is in the 95% CI in all cases) and therefore is of no importance. Table 2. Regression coefficients ɴ (95% CI) for size measurement of aneurysms for CTA and CEMRA with DSA as standard of reference. CTA (95% CI) MRA (95% CI) Obs 1 0.84 (0.72 - 0.96) 0.80 (0.72 - 0.88) Obs 2 0.83 (0.72 - 0.95) 0.83 (0.73 - 0.92)
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