The effect of magnetic resonance imaging on stainless-steel Z-stent–based abdominal aortic prosthesis

Preliminary of finite element analysis (FEA) investigation on the stent expansion

The requirement of stent expansion is important to stent deployment on the inner of the defected blood vessel. This defected blood vessel decreases in lumen diameter size because of accumulation of fat or plaque and caused the reduction of blood flow and oxygen supply to overall body. According to clinical guidelines, blood vessel that blockage by 70% need to be stenting. Stent expand past it elastic limit and plastically deform until the targeted diameter is achieved. Explicit dynamics Finite Element Analysis (FEA) was used in this paper to analyse the stent expansion process. The knowledge of stent radial displacement could prevent the injury of inner surface of artery while understanding on longitudinal foreshortening that aided the stent placement on targeted artery location. The controlled variable was geometry, material and boundary condition of stent. The manipulated variable was the speed of pressure application. The outcomes of this stent expansion simulation are maximum radial expansion, the uniform of radial displacement and longitudinal foreshortening. This simulation results help to improve stent installation on human body for balloon expandable stent and increase the understanding of explicit dynamics structure simulation of finite element in biomedical application.

Spondylodiscitis following endovascular abdominal aortic aneurysm repair: imaging perspectives from a single centre's experience

OBJECTIVE

Very few reports have previously described spondylodiscitis as a potential complication of endovascular aortic aneurysm repair (EVAR). We present to our knowledge the first case series of spondylodiscitis following EVAR based on our institution's experience over an 11-year period. Particular attention is paid to the key imaging features and challenges encountered when performing spinal imaging in this complex patient group.

MATERIALS AND METHODS

Of 1,847 patients who underwent EVAR at our institution between January 2006 and January 2017, a total of 9 patients were identified with imaging features of spondylodiscitis (0.5%). All cross-sectional studies before and after EVAR were assessed by a Consultant Musculoskeletal Radiologist and a Musculoskeletal Radiology Fellow to evaluate for features of spondylodiscitis.

RESULTS

All 9 patients had single-level spondylodiscitis involving lumbosacral levels adjacent to the aortic/iliac stent graft. Eight out of nine patients had an extensive anterior paravertebral phlegmon/abscess that was contiguous with the infected stent graft and native aneurysm sac ± anterior vertebral body erosion. Epidural disease was present in only 3 out of 9 patients and was a minor feature. MRI was non-diagnostic in 3 out of 9 patients owing to susceptibility artefact. ¹⁸F-FDG PET/CT accurately depicted the spinal level involved and adjacent paravertebral disease in patients with non-diagnostic MRI and was adopted as the follow-up modality in 3 out of 5 surviving patients.

CONCLUSION

Spondylodiscitis is a rare complication post-EVAR. Imaging features of disproportionate anterior paravertebral disease and anterior vertebral body bony involvement suggest direct spread of infection posteriorly to the adjacent vertebral column. Use of MRI versus ¹⁸F-FDG PET/CT as the optimal imaging modality should be directed by the type of stent graft deployed.

Posterior reversible encephalopathy syndrome from induced hypertension during endovascular thoracoabdominal aortic aneurysm repair

Endovascular repair of thoracoabdominal aortic aneurysm has been increasingly performed using fenestrated and branched endografts. Spinal cord injury is a complication of complex endovascular aortic repair, especially in patients with extensive aortic involvement. Maneuvers commonly used to avoid spinal cord injury include cerebrospinal fluid drainage and induced hypertension. Posterior reversible encephalopathy syndrome is associated with abnormal cerebral autoregulation through endothelial and blood-brain barrier dysfunction; the pathophysiology involves vasogenic edema, and severe hypertension is a recognized trigger. We report on a patient who developed posterior reversible encephalopathy syndrome associated with induced hypertension used to prevent spinal cord injury during endovascular repair of a type II thoracoabdominal aortic aneurysm using fenestrated and branched stent grafts.

Magnetic nanoparticles for targeted vascular delivery

Magnetic targeting has shown promise to improve the efficacy and safety of different classes of therapeutic agents by enabling their active guidance to the site of disease and minimizing dissemination to nontarget tissues. However, its translation into clinic has proven difficult because of inherent limitations of traditional approaches inapplicable for deep tissue targeting in human subjects and a need for developing well-characterized and fully biocompatible magnetic carrier formulations. A novel magnetic targeting scheme based on the magnetizing effect of deep-penetrating uniform fields is presented as an example of a strategy providing a potentially clinically viable solution for preventing injury-triggered reobstruction of stented blood vessels (in-stent restenosis). The design of optimized magnetic carrier formulations and experimental results showing the feasibility of uniform field-controlled targeting for site-specific vascular delivery of small-molecule pharmaceuticals, biotherapeutics, and cells are discussed in the context of antirestenotic therapy. The versatility of this approach applicable to different classes of therapeutic agents exerting their antirestenotic effects through distinct mechanisms prompts exploring the utility of uniform field-mediated magnetic stent targeting for combination therapies with enhanced efficiencies and improved safety profiles. Additional improvements in terms of site specificity and protracted carrier retention at the site of injury may be expected from the development and use of magnetic carriers exhibiting affinity for arterial wall-specific antigens.