58 Chapter 2 For both observers sensitivity of detecting small aneurysms was slightly better with CEMRA than with CTA; however, this difference was not significant. Discussion This was the first report that directly compares the accuracy of CEMRA with CTA in the detection of cerebral aneurysms with a relevant number of consecutive patients. Scans of lesser quality due to patient movement or bolus timing problems were also included, reflecting the clinical situation. We found no significant difference between CTA and CEMRA in the detection of intracranial aneurysms. In their meta-analysis White et al1 calculated a pooled sensitivity and specificity (with 95% CI) for detection of an aneurysm of 90% (88-92) and 86% (79-91) for CTA and 87% (84-90) and 95% (91-97) for MRA respectively. These results are in line with our study, even though our population contained a high percentage of small aneurysms (Figure 4 is an example of such a small aneurysm). Figure 4. a. Oblique projection of a volume rendered reconstruction of the CTA scan of a patient with a small right middle cerebral artery aneurysm. The aneurysm was properly described by both observers. b. Oblique projection of a volume rendered reconstruction of the CEMRA scan of the same patient as in Figure 4(a). The right middle cerebral artery aneurysm was not detected by both observers. In the meta-analysis of White et al. sensitivity decreased to 61% and 38% for CTA and MRA respectively for aneurysms smaller than 3mm. In their own prospective study, the sensitivity for small aneurysms was even lower: 57% for CTA and 35% for MRA for aneurysms smaller than 5 mm. In our series sensitivity for small aneurysms was considerably better for both modalities (Table 6). Therefore, it seems that the improvement in scan techniques has led to better detection of small aneurysms, especially with MRA. The sensitivity and specificity figures in our study are not as high as in previously published articles on the diagnostic performance of CEMRA in the detection of cerebral aneurysms,3-8 but because all acquisitions performed were included (no exclusions because of poor quality (Figure 5)), it likely reflects a more realistic expression of the performance of CEMRA in daily clinical practice. It shows that the
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