Colour-coded Doppler sonographic study of the haemodynamics in the parent artery of intracranial aneurysms

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.

The physics of endoluminal stenting in the treatment of cerebrovascular aneurysms

Endovascular stenting of aneurysms offers potential advantages over surgical clipping. Stenting is minimally invasive, and with the implementation of rapidly developing micro and nano technologies, it will in the future be possible to deploy stents in more remote locations of the cerebrovasculature. The key advantage of stenting is that in addition to impeding flow into the aneurysm, it provides the parent artery with a scaffold over which the artery can remodel. However, for a stent to be effective in this goal, it must be tailored to the local hemodynamics at the aneurysm site. This paper is a review of the qualitative and quantitative in vitro and in vivo experimentation as well as computer simulations that have been performed to elucidate the effects of various stent design parameters and the prevailing parent vessel hemodynamics on intra-aneurysmal flow patterns. Our results in numerous studies have shown that stenting substantially alters intra-aneurysmal flow. Furthermore, it is demonstrated that techniques have been developed in order to assess the efficacy of the stent in promoting intra-aneurysmal flow stagnation, thus creating the potential to optimize the device design for the treatment of intracranial aneurysms.