Simulation study employing different scenarios 81 Table 3. Consequences of the four different scenarios. Scenario 1 2 3 4 Patients undergoing DSA 75 16 37 29 Diagnostic costs (€) 54,375 30,500 45,725 39,925 Unjustified clipping (pt) 0 6 1 1 Unsuccessful coiling (pt) 0 1 0 1 Discussion The least costly of the four scenarios which were studied is Scenario 2, in which all patients underwent CEMRA and only the 16 patients with normal CEMRA findings would undergo additional diagnostic DSA. In this scenario however, of the 65 aneurysms which were present in our patient group, three aneurysms in two patients would have been assigned to a coiling procedure which, according to the DSA findings, would not have proved to be possible. One of those three was a left middle cerebral artery (MCA) aneurysm additional to a left posterior inferior cerebellar artery (PICA) aneurysm. This PICA aneurysm was judged coilable on both MRA and DSA, and was successfully coiled. So in this patient no unfruitful attempt at coiling would have been undertaken and the DSA study performed during the coiling of the PICA aneurysm would show the true nature and non-coilability of the MCA aneurysm. The other two aneurysms were a small lobulated right posterior communicating (PCom) aneurysm and a small left PCom aneurysm, both in the same patient. This patient would have undergone an unsuccessful attempt at coiling of the two aneurysms under general anesthesia in Scenario 2. Another six aneurysms would have been referred for surgery while coiling of the aneurysm was in fact possible, depriving the patients of the benefit of the preferred coiling procedure, if this scenario had been implemented. Four of these aneurysms were anterior communicating (ACom) aneurysms, three small and one large. The other two were a small left and a medium sized right MCA aneurysm. Scenario 3 in this group of 75 patients would result in the performance of 75 CEMRA studies and an additional 37 DSA studies. The total diagnostic costs per patient in this scenario are lower than those of the first scenario, as 38 patients would not need to undergo DSA in the diagnostic phase. In this scenario one aneurysm was considered not coilable on the basis of the CEMRA images but proved to be coilable on the “gold standard” DSA images, though in this case DSA had not been requested by the observers. This was a left small MCA aneurysm (Figure 1). The observers reported a wide neck and uncertainty about the relation of the MCA branches to the neck of the aneurysm. One aneurysm was judged to be coilable on the CEMRA images, but proved to be not coilable on the “gold standard” DSA images, in a case in which no additional DSA had been considered necessary by the observers. This aneurysm was the left MCA aneurysm also described above in Scenario 2, which was additional to a coilable PICA aneurysm. Again this would not have resulted in an unnecessary procedure as explained above. Altogether Scenario 3 would have resulted in a saving of 38 diagnostic DSA studies at the cost of one aneurysm being clipped although a coiling procedure would in fact have been possible.
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