Seungkwan Cho

Suggestion of Potential Stent Design Parameters to Reduce Restenosis Risk driven by Foreshortening or Dogboning due to Non-uniform Balloon-Stent Expansion

The foreshortening or dogboning of a stent that occurs due to transient non-uniform balloon-stent expansion can induce a vascular injury, resulting in restenosis of the coronary artery. However, previous studies rarely considered the effects of transient non-uniform balloon expansion on analysis of the mechanical properties and behaviors of stents during stent deployment, nor did they determine design parameters to minimize the restenosis risk driven by foreshortening or dogboning. The aim of the current study was, therefore, to suggest potential design parameters capable of reducing the possibility of restenosis risk driven by foreshortening or dogboning through a comparative study of seven commercial stents using finite element (FE) analyses of a realistic transient non-uniform balloon-stent expansion process. The results indicate that using stents composed of opened unit cells connected by bend-shaped link structures, in particular the MAC Plus stent, and controlling the geometrical and morphological features of the unit cell strut or the link structure at the distal ends of stent may prevent restenosis risk caused by foreshortening or dogboning. This study provides a first look at the realistic transient non-uniform balloon-stent expansion by investigating the mechanical properties, behaviors, and design parameters capable of reducing the possibility of restenosis risk induced by the foreshortening or the dogboning.

Comparative Studies of Different Vascular Stents in terms of Mechanical Performances: Finite Element Analysis

Seven representative commercialized stents were evaluated by FE analysis in terms of the criteria based on the itemized list of Food and Drug Administration (FDA) and European Standards (prEN). Tenax and MAC standard were generally excellent in various evaluation items. Palmaz-Schatz was the most excellent in fatigue durability, but its flexibility was a little inferior than that of other stents. This study may suggest a guideline for improvement in stent design and function.

Effectiveness of micro-current electrical stimulation for treating rheumatoid arthritis

Induction of micro-current in subject is known to be effective on the treatment of inflammatory disease. Thus, this study evaluated that the micro-current electrical treatment (MET) can reduce rheumatoid arthritis (RA), which is one of inflammatory disease, and tried to find optimized level of current for treatment. 55 male 11-week-old C57BL/6 mice were used and randomly allocated into five groups; normal group (N; n=11), the group of induced RA (C; n=11) and three groups of induced RA with MET (M) using different levels of current by 22 μA, 50 μA, and 400 μA (22M, 50M and 400M; n=11, respectively). MET was carried out for 1 hour each day. Both 3rd metatarsal (3rd MT) and tarsal (T) were scanned by in-vivo micro computed tomography (micro-CT) at 0week and after 3weeks in order to obtain structural parameters including BMD (Bone mineral density), BV (Bone volume) and Obj.N (Mean number of objects per slice). In M groups, all the measured parameters after 3 weeks were significantly higher than those of C group regardless of the current levels. However, there is no significant difference among the different levels of electrical current at 3week. These results indicated that the MET may be effective on the treatment of RA. However, we cannot assure the optimized level of current to treat RA tremendously.

Joint moments and center of body mass according to the weight of side loaded carriage in walking

The present study investigated the biomechanical effects of weight variation for side loaded carriage during walking upon joint moments and the center of body mass by using the inverse dynamic analysis. The motion data which were used as input data for inverse dynamic simulation were measured by the 3D motion analysis system. Six infrared cameras and two force plates were utilized and thirty nine reflective markers were attached to the subject to capture the walking motion with side loaded carriage. The healthy male subjects were participated in the experiment, and they walked with side loaded carriage which weighs 0, 5, 10 and 15kg, respectively. For each walking, the weight of side loaded carriage was selected randomly. As a result, the COM(Center Of Mass) was more inclined to the opposite side of side loaded carriage as the weight increased. This is the result of the balance mechanism of human in walking with side load. In other words, the human kept the total balance, leaning to the side of unloading when the human walked with one heavy side loaded. In addition, the ankle plantar-flexion moment of loading side was larger than that of unloading side when the weight increased. In knee joint, the knee extension moment of unloading side was smaller than that of loading side when the weight increased. The magnitude of hip extension moment had no significant difference. The hip extension moment of loading side was larger than that of unloading side. These results showed that the human used the ankle and hip joint of the loading side to support the body and the knee joint of the unloading side to progress the walking with keeping the balance of the body.