The metal coverage ratio (MCR) of a flow diverter influences the intra-aneurysmal hemodynamics; a high MCR will occlude an aneurysm early, while a low MCR may delay aneurysm occlusion. The true MCR of a pipeline embolization device (PED) could be lower due to oversize, device deformation, or aneurysm location. In this study deviation of the true MCR from the nominal MCR is assessed and whether their difference affects aneurysm occlusion rate is determined.
Methods
A total of 40 consecutive patients, each of them treated by one PED for their aneurysms at the internal carotid artery (ICA), were retrospectively analyzed. The DynaCT images of these deployed PEDs were used to determine their true dimensions and estimate three MCRs (local, mean, and nominal). These data were compared in two groups of patients who had different aneurysm outcomes at six months.
Results
The difference in the local MCR between two groups is small, but statistically significant (24.5% vs 21.6%, p = 05). The local MCR is consistently lower than the nominal MCRs (23.2% vs 30.2%, p < 0.001); however, the difference between the mean and local MCRs is small (23.9% vs 23.2%).
Conclusions
An expectation that a PED can achieve a MCR of 30% may not be reasonable. Device oversize and deformation during deployment lower the local MCR by 5–7%. A lowered MCR affects the aneurysm occlusion rate at six months.
Crobeddu E, Lanzino G, Kallmes DF, et al. Marked decrease in coil and stent utilization following introduction of flow diversion technology. J Neurointerv Surg 2013; 34: 481--485.
2.
D'UrsoPIKaradeliHHKallmesDF. Coiling for paraclinoid aneurysms: Time to make way for flow diverters?AJNR Am J Neuroradiol2012; 33: 1470–1474.
3.
AugsburgerLFarhatMReymondP. Effect of flow diverter porosity on intraaneurysmal blood flow. Klin Neuroradiol2009; 19: 204–214.
4.
LieberBBStancampianoAPWakhlooAK. Alteration of hemodynamics in aneurysm models by stenting: Influence of stent porosity. Ann Biomed Eng1997; 25: 460–469.
5.
WangKHuangQHongB. Correlation of aneurysm occlusion with actual metal coverage at neck after implantation of flow-diverting stent in rabbit models. Neuroradiology2012; 54: 607–613.
6.
FiorellaDWooHHAlbuquerqueFC. Definitive reconstruction of circumferential, fusiform intracranial aneurysms with the pipeline embolization device. Neurosurgery2008; 62: 1115–1120. discussion 20–21.
7.
JouLDMitchellBDShaltoniHM. Effect of structural remodeling (retraction and recoil) of the pipeline embolization device on aneurysm occlusion rate. AJNR Am J Neuroradiol2014; 35: 1772–1778.
8.
MaDXiangJChoiH. Enhanced aneurysmal flow diversion using a dynamic push-pull technique: An experimental and modeling study. AJNR Am J Neuroradiol2014; 35: 1779–1785.
9.
Mut F and Cebral JR. Effects of flow-diverting device oversizing on hemodynamics alteration in cerebral aneurysms. AJNR Am J Neuroradiol 2012; 33: 2010--2016.
10.
Bing F, Darsaut TE, Salazkin I, et al. Stents and flow diverters in the treatment of aneurysms: Device deformation in vivo may alter porosity and impact efficacy. Neuroradiology 2013; 55: 85--92.
11.
Berez A and Tran Q. Procedures for vascular occlusion. US Patent 12/9095460, 16 October 2012, US patent application full-text and image database (appft.uspto.gov).
12.
Ma D, Dumont TM, Kosukegawa H, et al. High fidelity virtual stenting (HiFiVS) for intracranial aneurysm flow diversion: in vitro and in silico. Ann Biomed Eng 2013; 41: 2143--2156.
13.
WangKYuanS. Actual metal coverage at the neck is critical for flow-diverting stents in treating intracranial aneurysms. AJNR Am J Neuroradiol2013; 34: E31–E32.
14.
SzikoraIBerenteiZKulcsarZ. Treatment of intracranial aneurysms by functional reconstruction of the parent artery: The Budapest experience with the pipeline embolization device. AJNR Am J Neuroradiol2010; 31: 1139–1147.
15.
FischerSVajdaZAguilar PerezM. Pipeline embolization device (PED) for neurovascular reconstruction: Initial experience in the treatment of 101 intracranial aneurysms and dissections. Neuroradiology2012; 54: 369–382.
16.
SaatciIYavuzKOzerC. Treatment of intracranial aneurysms using the pipeline flow-diverter embolization device: A single-center experience with long-term follow-up results. AJNR Am J Neuroradiol2012; 33: 1436–1446.
17.
LylykPMirandaCCerattoR. Curative endovascular reconstruction of cerebral aneurysms with the pipeline embolization device: The Buenos Aires experience. Neurosurgery2009; 64: 632–642. discussion 42–43; quiz N6.
18.
NelsonPKLylykPSzikoraI. The pipeline embolization device for the intracranial treatment of aneurysms trial. AJNR Am J Neuroradiol2011; 32: 34–40.
19.
KulcsarZHoudartEBonafeA. Intra-aneurysmal thrombosis as a possible cause of delayed aneurysm rupture after flow-diversion treatment. AJNR Am J Neuroradiol2011; 32: 20–25.
20.
ChalouhiNTjoumakarisSPhillipsJL. A single pipeline embolization device is sufficient for treatment of intracranial aneurysms. AJNR Am J Neuroradiol2014; 35: 1562–1566.
21.
De VriesJBoogaartsJVan NordenA. New generation of flow diverter (surpass) for unruptured intracranial aneurysms: A prospective single-center study in 37 patients. Stroke2013; 44: 1567–1577.
22.
PufferRCKallmesDFCloftHJ. Patency of the ophthalmic artery after flow diversion treatment of paraclinoid aneurysms. J Neurosurg2012; 116: 892–896.
Durst CR, Starke RM, Clopton D, et al. Endovascular treatment of ophthalmic artery aneurysms: Ophthalmic artery patency following flow diversion versus coil embolization. J Neurointerv Surg 2015. Epub ahead of print: 2015-011887.
25.
MascitelliJRPainMPanovF. Ophthalmic artery occlusion immediately following placement of a flow diverter without clinical sequelae. Interv Neuroradiol2015; 21: 191–195.
26.
Chalouhi N, Daou B, Kung D, et al. Fate of the ophthalmic artery after treatment with the pipeline embolization device. Neurosurgery 2015; 77: 581--584.
27.
ChalouhiNTjoumakarisSStarkeRM. Comparison of flow diversion and coiling in large unruptured intracranial saccular aneurysms. Stroke2013; 44: 2150–2154.
28.
LieberBBSadasivanC. Endoluminal scaffolds for vascular reconstruction and exclusion of aneurysms from the cerebral circulation. Stroke2010; 41: S21–S25.
29.
WakhlooAKLylykPde VriesJ. Surpass flow diverter in the treatment of intracranial aneurysms: A prospective multicenter study. AJNR Am J Neuroradiol2015; 36: 98–107.
30.
MohlenbruchMAHerwehCJestaedtL. The FRED flow-diverter stent for intracranial aneurysms: Clinical study to assess safety and efficacy. AJNR Am J Neuroradiol2015; 36: 1155–1161.
31.
LubiczBVan der ElstOCollignonL. Silk flow-diverter stent for the treatment of intracranial aneurysms: A series of 58 patients with emphasis on long-term results. AJNR Am J Neuroradiol2015; 36: 542–546.
32.
Caroff J, Mihalea C, Klisch J, et al. Single-layer WEBs: Intrasaccular flow disrupters for aneurysm treatment-feasibility results from a European study. AJNR Am J Neuroradiol 2015; 36: 1942--1946.
