Performance of Contrast Enhanced Magnetic Resonance Angiography 67 Results In 18 patients (24%) no aneurysm was found. Fifty patients harbored one aneurysm, six patients had two aneurysms and one patient had three aneurysms, adding up to a total of 65 aneurysms. Thirty three out of sixty five (50.8%) of the aneurysms in our study population were smaller than 5mm and 12/65 (18.5%) were smaller than 3mm. Sensitivity and specificity of the CEMRA and CTA assessments for the verdict whether an aneurysm could be treated by endovascular coiling or not, are given in table 1a. Calculations were done on all 75 cases, where the 18 cases with ‘no aneurysm present’ were regarded as ‘coiling not feasible’. Table 1a. Sensitivity and specificity (95% CI) of CTA and CEMRA for assessing the feasibility of endovascular treatment of the aneurysm, calculated for all 75 cases. Obs = Observer. CTA CEMRA Obs 1 58.8 (40.7 - 75.4) 52.9 (35.5 - 69.1) Sensitivity Obs 2 73.5 (55.6 - 87.1) 61.8 (43.6 - 77.8) Obs 1 89.8 (77.8 - 96.6) 87.8 (75.2 - 95.4) Specificity Obs 2 79.6 (65.7 - 89.8) 79.6 (65.7 - 89.8) There is no significant difference between the sensitivity and specificity of CTA and CEMRA tested with McNemar’s test statistics. Cohen’s Kappa for inter-observer agreement is 0.49 for both CEMRA and CTA for assessing the feasibility of endovascular treatment. ROC curves for the feasibility of endovascular treatment are given in figure 1. The areas under the curve are: 0.73 (0.62-0.83) and 0.78 (0.69-0.88) for CTA and 0.71 (0.60-0.81) and 0.77 (0.67-0.86) for CEMRA. The areas of CTA and CEMRA are not significantly different (p=0.75 for obs 1 and p=0.83 for obs 2). Figure 1. ROC curves for feasibility of coiling by both observers for CTA and CEMRA.
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