To examine the difference in arterial flow before and after flow diverter placement using quantitative flow measurements based on a DSA technique.
As everyone knows the flow diverter stent (FDS) disrupts blood flow into the aneurysm sac, maintaining normal blood flow through the parent vessel; sometimes, there is a neointimal proliferation across the device strut, that contributes to the aneurysm closure. Assessment of the aneurysm closure and the patency of collateral branches have been evaluated using angiographic and clinical findings, with different results. In this paper, published online December 8, 2016 in the Journal of NeuroInterventional Surgery, the study authors quantified the blood flow difference before and after the procedure at the level of proximal and distal internal carotid artery, using the software application syngo iFlow (Siemens, Munich, Germany). This software uses DSA sequence to generate a color map of the blood flow.
Chen C-W., Wong H-F., Ye Y-L. et al. reviewed DSA of 13 patients treated with placement of Pipeline, from November 2013 to November 2015, across the ostia of the ophthalmic artery (OphA) and anterior choroidal artery (AChA). Details about imaging protocol, image post-processing and data analysis are available in the original research.
The quantitative flow analysis showed improved flow in the terminal ICA, MCA and ACA. A decreased flow in the OphA and AChA is always evident after flow diverter placement and tent to be correlated with larger aneurysm volume. The use of adjuvant coiling was not correlated with the hemodynamic differences after the procedure.
Some authors suggested that a single FDS provides sufficient flow diversion for occlusion of most aneurysms; for this reason, any additional device will only increase morbidity, cost, and radiation exposure. Interestingly in this paper, Authors reported a case of a patient with a giant paraclinoid aneurysm treated with FDS and coils who had immediate complications because of partial expansion of FDS, probably the result of mechanical fatigue of the stent, a tortuous arterial curve, or too-dense packing of coils.
In conclusion, Authors considered quantitative DSA andvantageous, for subsequent reasons:
It does not require additional x-ray exposure because conventional DSA acquisition can generate color-coded images and obtain quantitative information.
- It is a real-time tool, because color-coded images with quantitative measurements are obtained immediately after acquiring the DSA series.
Hemodynamic conditions and changes can be analyzed using quantitative parameters.