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Laser-based metal powder bed fusion (PBF-LB/M) offers great potential for producing complex and filigree sub-millimetre parts with customised shapes, such as patient-specific vascular stents. However, stent fabrication via PBF-LB/M encounters fundamental challenges, including dimensional limitations, poor surface quality, difficult support structure handling and geometrical deviations. This study addresses these challenges by investigating the potential and limitations of a novel hybrid post-processing approach. This technique uses the combination of electrochemical polishing and chemical etching and is investigated from process and design perspectives, to emphasise the interactions between the two. With the systematic application of hybrid post-processing, the strut thickness and the surface roughness were substantially reduced. Moreover, it enabled the successful removal of part-internal support structures. Furthermore, angle and orientation-dependent geometrical deviations could be compensated, highlighting the potential of achieving homogenous strut thicknesses within parts containing variable overhang angles. This study demonstrates that the usage of hybrid (electro)chemical post-processing methods with specifically tailored process parameters is a promising approach for overcoming the design- and process-related challenges in PBF-LB/M manufactured sub-millimetre parts. [ABSTRACT FROM AUTHOR]

Magnesium alloy, as a new material for vascular stents, possesses excellent mechanical properties, biocompatibility, and biodegradability. However, the mechanical properties of magnesium alloy stents exhibit relatively inferior performance compared to traditional metal stents with identical structural characteristics. Therefore, improving their mechanical properties is a key issue in the development of biodegradable magnesium alloy stents. In this study, three new stent structures (i.e., stent A, stent B, and stent C) were designed based on the typical structure of biodegradable stents. The changes made included altering the angle and arrangement of the support rings to create a support ring structure with alternating large and small angles, as well as modifying the position and shape of the link. Using finite element analysis, the compressive performance, expansion performance, bending flexibility performance, damage to blood vessels, and hemodynamic changes of the stent were used as evaluation indexes. The results of these comprehensive evaluations were utilized as the primary criteria for selecting the most suitable stent design. The results demonstrated that compared to the traditional stent, stents A, B, and C exhibited improvements in radial stiffness of 16.9%, 15.1%, and 37.8%, respectively; reductions in bending stiffness of 27.3%, 7.6%, and 38.1%, respectively; decreases in dog-boning rate of 5.1%, 93.9%, and 31.3%, respectively; as well as declines in the low wall shear stress region by 50.1%, 43.8%, and 36.2%, respectively. In comparison to traditional stents, a reduction in radial recoiling was observed for stents A and C, with decreases of 9.3% and 7.4%, respectively. Although there was a slight increase in vessel damage for stents A, B, and C compared to traditional stents, this difference was not significant to have an impact. The changes in intravascular blood flow rate were essentially the same after implantation of the four stents. A comparison of the four stents revealed that stents A and C exhibited superior overall mechanical properties and they have greater potential for clinical application. This study provides a reference for designing clinical stent structures. [ABSTRACT FROM AUTHOR]

This study aims to develop reticular, tubular polyvinyl alcohol (PVA) vascular stents, and then examines their structure and properties. PVA fibers are knitted, followed by being immersed in a polycaprolactone (PCL) solution and thermally treated in order to form vascular stents. The test results indicate that the combination of a loop structure of knits and the PCL film that is adhered to fibers can effectively form elastic, compression-resistant PVA vascular stents. The vascular stents retain a stabilized path after an in vitro degradation, and thus this study successfully creates the desired elastic PVA vascular stents. [ABSTRACT FROM AUTHOR]

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The clinical results of endovascular stent grafting (EVG) on open surgery for distal aortic arch aneurysm were compared with those of conventional graft replacement to evaluate the lesser degree of invasiveness of EVG. Thirteen men with an average age of 68±6 years under-went EVG. Total arch replacement was performed in one and aortocoronary bypass grafting was combined in two. The controls were 12 men and one woman with an average age of 69±5 years. Surgery were performed via midsternotomy in seven and via left thoracotomy in six. Total arch replacement was performed in five. The operation time in the EVG group was shorter than that in the control group (410±88 vs. 515±147 min). There were no significant differences between the groups in bypass time (228±57 vs. 209±39 min) and circulatory arrest time (42 ±8 vs. 44±14 min). The blood transfusion rate was 31% in the EVG group and 77% in the control group. Long-term respiratory support was required in one EVG patient, compared with 46% of control patients. There was no operative mortality, but paraplegia occurred in one patient, cerebral infarction in one, and temporary partial spinal cord dysfunction in two in the EVG group. In the control group, one patient died of stroke, three had cerebral infarction, two had low output syndrome, one had sepsis, and one had gastrointestinal bleeding. EVG on open surgery had a shorter operative time, lower blood transfusion rate, and shorter respiratory support time. These results suggest that EVG is less invasive. However, further improvement is required to prevent complications. [ABSTRACT FROM AUTHOR]

Copyright of Der Radiologe is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A woven tantalum vascular stent (Strecker stent) was tested for ferromagnetism at 4.7 T and underwent magnetic resonance imaging (MRI) in vitro and in vivo at 1.5 T to evaluate the production of magnetic susceptibility artifacts. No ferromagnetism was detected. Spin-echo, phase reconstruction, and gradient echo images revealed a low level of susceptibility artifacts both in vitro and in vivo. Our findings demonstrate the feasibility of using MRI to evaluate blood vessels noninvasively following tantalum stent placement. [ABSTRACT FROM AUTHOR]