Analysis and Optimization for Support Performance of Magnesium Alloy Stent / 医用生物力学

Objective To conduct simulation analysis on support performance of the stent by using finite element method, and optimize structure parameters of the stent by using Kriging surrogate model, so as to provide more scientific guidance for clinical treatment with design and development of the stent. Methods The contact model was established by penalty function method. The generalized variational principle was selected as theoretical basis of the numerical simulation, and the theory of Kriging surrogate model was used for finite element optimization on support stiffness of the stent, so as to study the effect from the number of circumferential support, the length of the support and the initial diameter on support performance of the stent. Results With the increase of the number of circumferential support or the length of the support, the support performance showed the decreasing tendency; with the increase of the initial diameter, the support performance showed the increasing tendency. From seven stents by using the theory of Kriging surrogate model, it was concluded that structural parameters of the optimal stent were: the number of circumferential support was six, the length of the support was 1.15 mm, and the initial diameter was 1.65 mm. Conclusions The numerical result agreed well with the experimental data and the error was smaller than 5%, and the error rate of experimental repeatability was within 0.5%, which verified effectiveness and rationality of the finite element analysis. The optimization of support performance provides an important reference for design and exploration of new magnesium alloy stent.

The degradation time and the intimal hyperplasia of biodegradable magnesium alloy stent implanted in the abdominal aorta of experimental rabbits / 介入放射学杂志

Objective To observe the degradation time and the intimal hyperplasia of biodegradable magnesium alloy stent (MPM) implanted in the abdominal aorta of experimental rabbits.Methods A total of 24 New Zealand white rabbits were randomly divided into four groups (30 d,60 d,90 d and 180 d) with 6 rabbits in each group.In cach rabbit one MPM stent was implanted in the abdominal aorta at the level of one cm below the left renal artery.Reexamination of abdominal aortography with DSA was separately performed at 30,60,90 and 180 d after stent implantation to check the stent condition.The rabbits of each group were sacrificed at the corresponding scheduled day,the stenting segment of aorta of each rabbit was removed and the specimen was sent for microscopic examination.The experimental results were analyzed with SPSS20.0 software.Results All the 24 experimental rabbits survived.During the follow-up period the stent showed gradual degradation changes,and basically complete degradation was not observed until to 180 days.Meanwhile,the intimal hyperplasia reached its peak at 90 days after implantation.The abdominal aorta remained unobstructed during the whole process of degradation.Conclusion The time of complete degradation for MPM stent is 182 days,which is long enough to meet the needs of vascular positive remodeling.

The degradation performance of AZ31 bioabsorbable magnesium alloy stent implanted in the abdominal aorta of rabbits / 介入放射学杂志

Objective To make a preliminary evaluation of the degradation of AZ31 bioabsorbable magnesium alloy stent implanted in the abdominal aorta of experimental rabbits.Methods Twelve AZ31 biodegradable magnesium alloy stents were separately deployed in the infrarenal abdominal aortas of twelve New Zealand white rabbits.Every three experimental rabbits were sacrificed each time at one,two,three and four months after the procedure of stenting.The stenting segment of the aortas were harvested,radiographod and sent for pathologic examination to observe the degradable performance of the stent.Results All animals survived form the operation in the scheduled follow-up period.Radiographically and pathologically,the stents were fully expanded with perfect shape one month after the procedure,and part of the stent struts began to be degraded and fractured in two months,resulting in the loss of its supporting function.Three months after the implantation most stents were corroded.and in four months all the stents become completely destroyed.The estimating time for producing complete degradation of AZ31 magnesium alloy stents in rabbit's aorta was 104.5 days.Conclusion AZ31 bioabsorbable magnesium alloy stents implanted in rabbit abdominal aorta will lose their radial force in two months.How to prolong the functioning time of the implanted stents is the next research target.

Research progress of biodegradable stent in the application for benign luminal stenosis / 介入放射学杂志

Stent implantation plays an significant role in the interventional therapy, mainly with permanent stent, possessing many disadvantages such as restenosis and inflammatory hyperplasia and can thus hardly be used in children and nonmalignant stenosis. Biodegradable stent has theoretical capability to solve these problems and acquires a bright future. Nowadays, with the development of material industry and manufacture craft, biodegradable stent technique has turned up to be mature in last decades. Through the strict animal experiments and prophase of clinic application, satisfactory result has been acquired. We believe that bioabsorbable stent will be widely used in many benign diseases which would be a good supplement for permanent stent in the near future.