Visualizing the dynamics of cerebral aneurysms with four-dimensional computed tomographic angiography

OBJECTIVE: This study was designed to assess cerebral aneurysm hemodynamics with four-dimensional (4-D) computed tomographic (CT) angiography. METHODS: Multislice computed tomography with a retrospective electrocardiography-gated reconstruction algorithm was used. The motions of the aneurysmal wall, bleb, and dissecting cavity were rendered observable in a 4-D CT movie. RESULTS: The findings for 30 patients with 34 aneurysms who underwent 4-D CT angiography were analyzed. Twenty-three aneurysms were documented in the anterior circulation region, and the remaining 11 aneurysms were in the posterior circulation. The average aneurysm size was 6.4 mm, and there were five large aneurysms. There were 28 saccular, 4 dissecting, and 2 fusiform aneurysms. 4-D CT movies were obtained successfully in all aneurysms. The aneurysm wall motion of two growing aneurysms exhibited a highly irregular pulsation in the 4-D CT movie. Pulsating blebs were detected in nine (32.1%) of the saccular aneurysms. In two patients with subarachnoid hemorrhage, preoperative 4-D CT angiography revealed dangerous pulsating blebs that were confirmed as the ruptured points during the surgical procedure. Specifically, in the dissecting aneurysms, the 4-D CT movie revealed a pulsating line, which provided accurate and detailed information regarding the dissecting cavity and intimal flap. The dissecting cavity revealed by the 4-D CT movie could not be detected with conventional or three-dimensional digital subtraction angiography. The 4-D CT movie images were highly useful in making anatomic judgments for the endovascular surgery procedure. CONCLUSION: 4-D CT images are valuable in determining aneurysmal wall dynamics. Highly useful information was obtained regarding intracranial aneurysms with 4-D CT angiography compared with other modalities. Further studies will be necessary to elucidate the optimal application of this new technology to both the pathological characteristics and therapeutic amelioration of aneurysmal features such as dome pulsation, blebs, and growing aneurysms.