Evaluation of intra-aneurysmal blood flow by digital subtraction angiography: blood flow change after coil embolization

BACKGROUND: The natural course of cerebral aneurysms is related to many factors, and it is very important that intra-aneurysmal blood flow is considered. Our group developed a method that allowed the simultaneous evaluation of blood flow in human cerebral aneurysms using digital subtraction angiography (DSA) with no special devices. The intra-aneurysmal blood flow measurement would also be very useful for coil embolization. Since the Guglielmi detachable coil (GDC) was developed, many patients with cerebral aneurysm have been treated with GDC, but coil compaction has sometimes caused a problem after the coil embolization of a cerebral aneurysm. We believed that an intra-aneurysmal flow measurement would suggest the final result of embolization during the procedure. METHODS: We performed DSA to examine 17 aneurysms in 17 patients. The video signal of serial DSA images was stored on a personal computer, and time-density curves were obtained for each individual pixel. The formula, determined by a two-exponential model, was fitted to the time-density curve 1000 times by least square approximation for each individual pixel. We indirectly substituted the coefficient of the flow-in curve for the blood flow. We were therefore able to display the distribution of intra-aneurysmal blood flow in color. We could compare the blood flow in each portion of the cerebral aneurysm and parent artery during coil embolization. RESULTS: The blood flow k(a) in a small aneurysm was faster than that in a large aneurysm, and it slowed in accordance with the coil embolization. The blood flow in a large aneurysm was sometimes accelerated by incomplete coil embolization. CONCLUSION: We can detect the flow distribution in cerebral aneurysms and the flow change during coil embolization, using existing equipment. Our method would be useful in elucidating the natural history of cerebral aneurysms, treating cerebral aneurysms with coils, and following patients after treatment.