ABSTRACT
Objective:To investigate the asymmetric geometry of middle cerebral artery (MCA) bifurcations and aneurysm formation.Methods:From January 2017 to April 2020, 65 patients with MCA aneurysm underwent 3D-digital subtraction angiography (DSA) in our hospital were recruited in this study; 170 patients without arterial stenosis or cerebral aneurysm at the same time period were selected as normal control group; their corresponding morphological parameters of MCA bifurcations in the imaging data were analyzed. Bifurcation angle was termed as φ1, while small and large lateral angles were termed as φ2 and φ3, respectively. D2, S2, C2, T2 and E2 represented diameter, sectional area, circumference, tortuosity and ellipticity of the branch forming angle φ2 with parent vessel, respectively; whereas D3, S3, C3, T3 and E3 represented diameter, sectional area, circumference, tortuosity and ellipticity of the branch forming angle φ2 with parent vessel on the contralateral branch, respectively. The independent factors affecting the formation of MCA aneurysm were screened by binary Logistic regression, and the predictive value of independent factors affecting the formation of MCA aneurysm was evaluated by receiver operating characteristic (ROC) curve.Results:(1) The aneurysmal group had significantly larger φ1, significantly smaller φ2 and φ3 than the normal control group ( P<0.05); D3, S3, C3, T2, T3 and E2 in the aneurysmal group were significantly higher/larger than those in the normal control group ( P<0.05). In terms of the symmetry of bilateral branches of blood vessels, the difference of φ3/φ2 ratio between the normal control group and aneurysm group was statistically significant ( P<0.05). (2) Binary Logistic regression results showed that φ2 was the protective factor for aneurysm formation ( OR=0.880, 9 5%CI: 0.844-0.918, P=0.000), while D3 and φ3/φ2 ratio were the risk factors for aneurysm formation ( OR=4.493, 9 5%CI: 1.414-14.278, P=0.011; OR=30.676, 95%CI: 9.884-95.202, P=0.000). (3) The ROC curve showed that the area under the curve of φ2 was the largest, reaching 0.93, and the optimal cut-off point was 104.59°, enjoying sensitivity and specificity of 87.7% and 85.9%, respectively. Conclusion:Normal MCA bifurcations almost show symmetrical morphology, whereas aneurysmal MCA bifurcations show asymmetrical morphology in both lateral angles and daughter branches; φ2 is the best morphological parameter to predict the aneurysm formation of MCA bifurcations.
ABSTRACT
Objective To explore the mechanism of ankle sprain varus, a kind of human ankle brace with asymmetric physiological structure which can protect the ankle effectively is designed. Methods The anatomic factors of ankle varus were analyzed firstly, and a kind of ankle brace with asymmetric structure was designed based on asymmetric structure of ankle joint by anatomy. Using Kinect system and Geomagic Studio software, 3D scanning and digital modeling on ankle joint of a male adult were performed, and the ankle model was established by 3D printing technology. With EVA film, silica gel film and wrapped edge copper network as raw materials, two kinds of ankle brace with asymmetric structure were prepared by 3D draping and composite materials processing technology. The shaping properties, tensile properties, fatigue performance, outer fabric breathability and friction of the designed brace were tested. Results The outside of ankle brace with asymmetric structure had good shaping property, low tensile elastic recovery rate. Under the effect of repeated small load, EVA composite materials and silicone composite materials could keep good elastic recovery and effectively bear external varus forces. The results from air permeability and grinding test showed that polyester material was a kind of suitable fabrics for the outer lining material. Conclusions The mechanical properties of ankle brace with asymmetric structure can meet the requirement of ankle varus protection. The fabric of ankle brace can improve moisture permeability and frictional properties.
ABSTRACT
Objective To design a novel high performance stent with preferable axial flexibility by using smaller strut thickness and less metal coverage which would not compromise its radial strength, so as to reduce the in-stent restenosis. Methods Based on researches about deformation properties of both the symmetric and asymmetric cell structures, the new stent structure was designed and analyzed through numerical simulation. The radial strength and bending stiffness tests were performed to evaluate the stent made by the new design. Results The proposed design possessed a higher radial strength, smaller metal coverage and good flexibility, which would be beneficial for the reduction of in-stent restenosis. Conclusions The asymmetric structure-based stent design method is effective, by which a high performance stent design can be obtained.