COMPUTERIZED-TOMOGRAPHY ANGIOGRAPHY OF RUPTURED CEREBRAL ANEURYSMS - FACTORS AFFECTING TIME TO MAXIMUM CONTRAST CONCENTRATION

Object. This study was conducted to assess the diagnostic value of thr ee-dimensional computerized tomography (3-D CT) angiography in demonst rating cerebral aneurysms in 42 consecutive patients presenting with a cute subarachnoid hemorrhage (SAH). Methods. To obtain the volume data for selective visualization of the cerebral arteries without enhancem ent of the venous system, the time delay was established between the i njection of contrast medium and the start of scanning by using two dif ferent methods. The circulation lime was calculated with Schad's formu la in the first 13 cases, but the results were not satisfactory. In th e 29 subsequent cases the time delay was established using a single-le vel dynamic CT prescan. The dynamic prescan demonstrated the statistic al differences in peak time with regard to patient age, SAH grade, and the postresuscitation state after cardiopulmonary arrest. The 3-D CT angiograms were generated from the volume data by using a voxel transm ission method. Computerized tomography angiography obtained after opti mally adjusted time delay demonstrated the contour of the cerebral art eries in 97% of cases, and aneurysms were detected in 93%. Enhancement of the cavernous sinus and major cortical veins was avoided. Even in patients who suffered cardiopulmonary arrest, images of the major arte ries were clearly demonstrated after resuscitation. Conclusions. In an emergency situation, CT angiography with a dynamic prescan may be an alternative to magnetic resonance angiography or digital subtraction a ngiography in the diagnosis of ruptured aneurysms. This modality would also be useful for the precise assessment of small aneurysms, blebs, and aneurysms adjacent to the cavernous sinus.