Stroke is the second leading cause of death in the world. Ischemic stroke, caused by the blockage of intracranial arteries, accounts for approximately 80% of strokes. Among this proportion, acute ischemic stroke, usually caused by the sudden formation of blood clots, can cause fatal blockages in arteries. We proposed a unique blood clot retriever for the treatment of acute ischemic stroke, and conducted a series of tasks, including design, computer simulation, prototyping, and bench testing, for the proof of concept. Unlike most blood clot retrievers used today, our novel design deviates from traditional stent-like blood clot retrievers and uses large closed cells, irregular spikes, and strut protrusions to achieve maximum entanglement for better retrieval performance. Experimental results showed that the retrieval rate of our blood clot retriever was 79%, which demonstrated the feasibility of our new design concept.
Vascular stents could suffer from repetitive motions due to pulsatile blood pressure and daily activities. Stent fatigue resistance has thus become a critical issue for stent design. In this paper, an intriguing stent design concept aimed at enhancing the fatigue life was investigated. The concept was to re-distribute stresses more uniformly by tapering the stent strut width. Finite element models were developed to evaluate the mechanical integrity and fatigue safety factor of the stent under various loading conditions. Simulation results show that the fatigue safety factor of this novel stent design increased by 4 times that of a conventional stent. Conceptual stent prototypes were cut by a pulsed-fiber laser, followed by a series of expansions and heat treatments to gradually shape the stent to its target size. A rotating bending fatigue tester was built for this study and stent fatigue tests were conducted for proof of concept. Experimental results show that this stent design concept successfully enhanced the fatigue life as designed. Its fatigue cycle number jumped to 6∼7 times that of a conventional stent, which agreed well with the trend predicted by FEA simulations. The findings of this paper provide an excellent guide to greatly improve stent fatigue life.
Background Carotid artery stenosis (CAS) is a common cause of ischemic stroke, and the early detection of CAS may improve patient outcomes. Carotid Doppler ultrasound is commonly used to diagnose CAS. However, it is costly and may not be practical for regular screening practice. This article presents a novel noninvasive and noncontact detection technique using video‐based motion analysis (VMA) to extract useful information from subtle pulses on the skin surface to screen for CAS. Methods and Results We prospectively enrolled 202 patients with prior carotid Doppler ultrasound data. A short 30‐second video clip of the neck was taken using a commercial mobile device and analyzed by VMA with mathematical quantification of the amplitude of skin motion changes in a blinded manner. The first 40 subjects were used to set up the VMA protocol and define cutoff values, and the following 162 subjects were used for validation. Overall, 54% of the 202 subjects had ultrasound‐confirmed CAS. Using receiver operating characteristic curve analysis, the area under the curve of VMA‐derived discrepancy values to differentiate patients with and without CAS was excellent (area under the curve, 0.914 [95% CI, 0.874–0.954]; P <0.01). The best cutoff value of VMA‐derived discrepancy values to screen for CAS was 5.1, with a sensitivity of 87% and a specificity of 87%. The diagnostic accuracy was consistently high in different subject subgroups. Conclusions A simple and accurate screening technique to quickly screen for CAS using a VMA system is feasible, with acceptable sensitivity and specificity.
An intracranial aneurysm is a weakened area in the wall of a cerebral artery which causes abnormal localized ballooning of the blood vessel. As an aneurysm grows, it puts pressure on adjacent structures and may eventually rupture, leading to severe complications or even sudden death. The standard treatments for intracranial aneurysms include traditional craniotomy and endovascular coiling. The purpose of these treatments is to stop the blood flow to an aneurysm to reduce the risk of rupture. In recent years, another new device, "flow diverter", has gained popularity. It is placed in the parent artery to divert the blood flow away from the weakened area, isolating aneurysms from normal circulation. Although flow diverter stents have great potential, there remains clinical issues to be resolved. This paper proposes a unique hybrid flow diverter, the first of its kind in the world, for treatment of the intracranial aneurysm. The hybrid flow diverter is designed to have variable mesh densities, with the denser side facing an aneurysm to block the blood flow and the lighter side facing the artery to prevent stenosis. It is deployed in the main cerebral artery next to an aneurysm to divert the blood flow away from the weakened aneurysm. Simulation results showed that the hybrid flow diverter reduced the blood flow into an aneurysm by a whopping 75-95%. The residence time of the blood flow inside an aneurysm was 12.47 times longer with the hybrid flow diverter, which may trigger thrombogenic reaction to fill an aneurysm and thus reduce the risk of rupture.
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