In vitro, contrast agent-based evaluation of the influence of flow diverter size and position on intra-aneurysmal flow dynamics using syngo iFlow.

PURPOSE: Treatment of intracranial aneurysm with flow-diverting devices has become widespread in recent years. Despite that, intra-aneurysmal flow changes are yet not fully understood and can lead to different complications. Our aim was an in vitro contrast-based evaluation of the influence of flow diverter size and position on intra-aneurysmal flow dynamics. METHODS: Flow-diverting devices with different sizes (diameters 4.0, 4.5, and 6.0 mm) were deployed in seven silicone aneurysm models at different positions relative to the aneurysm neck (proximal, central, distal). Using syngo iFlow, we defined quantitative evaluation criteria based on contrast medium intensity and performed a flow evaluation. RESULTS: Intra-aneurysmal flows were heavily dependent on both size and position of flow-diverting devices at the aneurysm neck. We observed a higher peak intensity delay and intra-aneurysmal washout delay with the centrally placed 4.0- and 4.5-mm device, respectively, compared to the proximal and distal positions. Especially distally placed 4.0-mm devices led to an earlier filling of the aneurysm and increased intra-aneurysmal contrast agent intensity compared to the parent vessel, due to a potential endoleak. CONCLUSIONS: Not only size but also position of flow-diverting devices have a considerable impact on the intra-aneurysmal flow dynamics. The suggested evaluation criteria allowed a quantitative comparison of flow-diverting effect using syngo iFlow and could represent an efficient tool for predicting flow diversion pre-procedurally.

Evaluation of occurring complications after flow diverter treatment of elastase-induced aneurysm in rabbits using micro-CT and MRI at 9.4 T.

INTRODUCTION: Flow diverters are increasingly being used to treat intracranial aneurysms. This study evaluates occurring complications of flow-diverting devices in the treatment of experimental aneurysms, involving the use of micro-CT and small animal MRI at 9.4 T, in correlation to angiographic and histological findings. METHODS: We previously published two preclinical studies, in which we assessed two different flow diverters in the treatment of elastase-induced aneurysms. Devices have been implanted across the aneurysm neck as well as in the abdominal aorta. From these studies, a total of 65 devices (prototype FD (n = 30) and Derivo embolization device (n = 35)) additionally underwent micro-CT and MRI after angiographic follow-up and before being histologically examined. RESULTS: The different architectures of both devices were precisely comparable due to high-resolution micro-CT imaging. Micro-CT revealed wire fractures in nine cases (30 %) only with the prototype FD. In three cases (10 %), severe wire fractures correlated with an in-stent stenosis due to intimal hyperplasia. Other complications, like distal stent occlusions and post-stent stenosis, were seen in both groups and verified with both imaging techniques. Osseous metaplasia were correlated to calcifications seen with micro-CT. MRI enabled visualization of the position of the implanted devices relative to the aneurysm and revealed incomplete aneurysm neck coverage with the prototype FD in two cases (6.7 %). CONCLUSION: Micro-CT and 9.4-T MRI are valid to discover and understand occurring complications of flow diverters in the preclinical phase and can serve as evaluation tools to minimize complication rates of endovascular devices in the future.

Corrigendum: Development of a Routinely Applicable Imaging Protocol for Fast and Precise Middle Cerebral Artery Occlusion Assessment and Perfusion Deficit Measure in an Ovine Stroke Model: A Case Study.

[This corrects the article DOI: 10.3389/fneur.2019.01113.].

Development of a Routinely Applicable Imaging Protocol for Fast and Precise Middle Cerebral Artery Occlusion Assessment and Perfusion Deficit Measure in an Ovine Stroke Model: A Case Study.

Temporary middle cerebral artery occlusion (MCAO) in sheep allows modeling of acute large vessel occlusion stroke and subsequent vessel recanalization. However, rapid and precise imaging-based assessment of vessel occlusion and the resulting perfusion deficit during MCAO still represents an experimental challenge. Here, we tested feasibility and suitability of a strategy for MCAO verification and perfusion deficit assessment. We also compared the extent of the initial perfusion deficit and subsequent lesion size for different MCAO durations. The rete mirabile prevents reliable vascular imaging investigation of middle cerebral artery filling status. Hence, computed tomography perfusion imaging was chosen for indirect confirmation of MCAO. Follow-up infarct size evaluation by diffusion-weighted magnetic resonance imaging revealed fluctuating results, with no apparent relationship of lesion size with MCAO at occlusion times below 4 h, potentially related to the variable collateralization of the MCA territory. This underlines the need for intra-ischemic perfusion assessment and future studies focusing on the correlation between perfusion deficit, MCAO duration, and final infarct volume. Temporary MCAO and intra-ischemic perfusion imaging nevertheless has the potential to be applied for the simulation of novel recanalization therapies, particularly those that aim for a fast reperfusion effect in combination with mechanical thrombectomy in a clinically realistic scenario.