How patient specific are patient-specific computational models of cerebral aneurysms? An overview of sources of error and variability

Computational modeling of cerebral aneurysms, derived from clinical 3D angiography, has become widespread over the past 15 years. While such "image-based" or "patient-specific" models have shown promise for the assessment of rupture risk, much debate remains about their reliability in light of necessary modeling assumptions and incomplete or uncertain model input parameters derived from the clinic. The aims of this review were to walk through the various steps of this so-called patient-specific modeling pipeline and to highlight evidence supporting those steps that we can or cannot rely on. The relative importance of the different sources of error and variability on hemodynamic predictions is summarized, with recommendations to standardize for those that can be avoided and to pay closer attention those to that cannot.

Computational Hemodynamic Modeling of Arterial Aneurysms: A Mini-Review

Arterial aneurysms are pathological dilations of blood vessels, which can be of clinical concern due to thrombosis, dissection, or rupture. Aneurysms can form throughout the arterial system, including intracranial, thoracic, abdominal, visceral, peripheral, or coronary arteries. Currently, aneurysm diameter and expansion rates are the most commonly used metrics to assess rupture risk. Surgical or endovascular interventions are clinical treatment options, but are invasive and associated with risk for the patient. For aneurysms in locations where thrombosis is the primary concern, diameter is also used to determine the level of therapeutic anticoagulation, a treatment that increases the possibility of internal bleeding. Since simple diameter is often insufficient to reliably determine rupture and thrombosis risk, computational hemodynamic simulations are being developed to help assess when an intervention is warranted. Created from subject-specific data, computational models have the potential to be used to predict growth, dissection, rupture, and thrombus-formation risk based on hemodynamic parameters, including wall shear stress, oscillatory shear index, residence time, and anomalous blood flow patterns. Generally, endothelial damage and flow stagnation within aneurysms can lead to coagulation, inflammation, and the release of proteases, which alter extracellular matrix composition, increasing risk of rupture. In this review, we highlight recent work that investigates aneurysm geometry, model parameter assumptions, and other specific considerations that influence computational aneurysm simulations. By highlighting modeling validation and verification approaches, we hope to inspire future computational efforts aimed at improving our understanding of aneurysm pathology and treatment risk stratification.

Numerical simulation of hemodynamics in intracranial saccular aneurysm treated with a novel stent

Different from the traditional stents, a novel stent with triangular wire cross-section is proposed, and numerical simulation is performed to compare the hemodynamic effect of the novel stent with that of traditional ones. Three kinds of stents with circular, rectangular, and triangular wire cross-sections were designed to treat saccular aneurysm, which were named the C-stent model, the R-stent model, and the T-stent model, respectively. An unstented aneurysm model (named the Unstented model), as a control, was also designed. Fluid-structure interaction in these four models was simulated. The results demonstrate that the resistance of the novel T-stent model is lower than that of the R-stent model, but higher than that of the C-stent model. Compared with the C-stent model, the T-stent model exhibits greater velocity decrease and longer turnover time. Meanwhile, the pressure increase of the T-stent model is lower than the R-stent model, and the magnitude and the fluctuation of wall shear stress is optimized in the T-stent model. The novel stent with a bare triangular wire cross-section has some comparative advantages. These results may provide some theoretical guidance for the structural design of an endovascular stent for the interventional treatment of aneurysm.