Wavelet denoising of fiber optic monitoring signals in permafrost regions.

To address the noise issue in fiber optic monitoring signals in frozen soil areas, this study employs wavelet denoising techniques to process the fiber optic signals. Since existing parameter choices for wavelets are typically based on conventional environments, selecting suitable parameters for frozen soil regions becomes crucial. In this work, an index library is constructed based on commonly used wavelet basis functions in civil engineering. An optimal wavelet basis function is objectively selected through specific criteria. Considering the characteristic of small root mean square error in fiber optic signals in frozen soil areas, a multi-index fusion approach is applied to determine the optimal decomposition level. Field observations validate that denoised signals, with parameters set appropriately, can more accurately identify locations where settlement occurs.

Electrochemical polishing, characterisation and in vitro evaluation of additively manufactured CoCr stents with personalised designs.

Additive manufacturing (AM) technology has paved the way for manufacturing personalised stents. However, there is a notable gap in comprehensive microstructure analyses and in vitro evaluations of the AM CoCr stents using advanced methodologies. To address this gap, this study focuses on investigating the microstructure and in vitro performance of personalised CoCr stents manufactured through micro-laser powder bed fusion (µ-LPBF). The evaluation process begins with the measurements of dimensions and surface roughness, followed by in-depth microstructural analyses. To improve surface roughness and reduce excessive strut size, the µ-LPBF stents undergo electrochemical polishing. Importantly, in vitro stent deployments are carried out in artificial arteries manufactured based on actual patients' data. Compared to the commercial MULTI-LINK VISION CoCr stent, the µ-LPBF personalised stents have rough surface finish (average roughness: 1.55 µm for µ-LPBF vs. 1.09 µm for commercial) and compromised grain microstructures (elongated for µ-LPBF vs. equiaxed for commercial). However, the personalised stents demonstrate better performances in in vitro tests. Notably, compared to the commercial stent in the two studied cases, they deliver larger lumen gains (up to 11.24 %) and reduced recoils (up to 4 times). This study validates the merit of the lesion-specific designs and the feasibility of using AM technology for stent fabrication.

[Analysis of Key Points of Technical Review of Traditional Chinese Medicine Fumigation Treatment Device].

Traditional Chinese medicine fumigation device is the carrier of traditional Chinese medicine fumigation treatment. In recent years, with the rapid development of new technology and new materials, the development of fumigation device changes with each passing day, and a variety of new products continue to emerge. However, at present, the lack of corresponding evaluation norms, resulting in some difficulties in the registration, marketing, quality control, evaluation scale and other aspects of the product. Some products have many disadvantages in clinical use. From the perspective of technical review, this paper elaborates and analyzes the main concerns in technical review, such as product structure, main risks, performance requirements, clinical evaluation, etc., in order to provide a basis for the design, development, production, registration, use and post-marketing supervision of the devices.

Impact of inverse unequal height strut structure on the functional performance of an additively manufactured cardiovascular stent.

Recently, additive manufacturing (AM) has been investigated as an innovative method to manufacture stents due to its capability in producing complex and customized structures. In this paper, the cardiovascular stents of M-type and N-type with inverse unequal height strut structure and N-type with equal height strut structure were designed and manufactured by Selective Laser Melting (SLM). Following surface polishing, balloon expansion, plane compression and three-point bending experiments were carried out to evaluate the mechanical performance of the stent. The stents designed with inverse unequal height strut structure showed higher radial support performance and lower radial recoil when compared to the stents with uniform design. This study proved the feasibility of SLM in rapid manufacturing of cardiovascular stents that can be used for performance evaluation in design stage.

In-vivo assessment of vascular injury for the prediction of in-stent restenosis.

BACKGROUND: Despite optimizations of coronary stenting technology, a residual risk of in-stent restenosis (ISR) remains. Vessel wall injury has important impact on the development of ISR. While injury can be assessed in histology, there is no injury score available to be used in clinical practice. METHODS: Seven rats underwent abdominal aorta stent implantation. At 4 weeks after implantation, animals were euthanized, and strut indentation, defined as the impression of the strut into the vessel wall, as well as neointimal growth were assessed. Established histological injury scores were assessed to confirm associations between indentation and vessel wall injury. In addition, stent strut indentation was assessed by optical coherence tomography (OCT) in an exemplary clinical case. RESULTS: Stent strut indentation was associated with vessel wall injury in histology. Furthermore, indentation was positively correlated with neointimal thickness, both in the per-strut analysis (r = 0.5579) and in the per-section analysis (r = 0.8620; both p ≤ 0.001). In a clinical case, indentation quantification in OCT was feasible, enabling assessment of injury in vivo. CONCLUSION: Assessing stent strut indentation enables periprocedural assessment of stent-induced damage in vivo and therefore allows for optimization of stent implantation. The assessment of stent strut indentation might become a valuable tool in clinical practice.

[Three-dimensional printed 316L stainless steel cardiovascular stent's electrolytic polishing and its mechanical properties].

The interventional therapy of vascular stent implantation is a popular treatment method for cardiovascular stenosis and blockage. However, traditional stent manufacturing methods such as laser cutting are complex and cannot easily manufacture complex structures such as bifurcated stents, while three-dimensional (3D) printing technology provides a new method for manufacturing stents with complex structure and personalized designs. In this paper, a cardiovascular stent was designed, and printed using selective laser melting technology and 316L stainless steel powder of 0-10 µm size. Electrolytic polishing was performed to improve the surface quality of the printed vascular stent, and the expansion behavior of the polished stent was assessed by balloon inflation. The results showed that the newly designed cardiovascular stent could be manufactured by 3D printing technology. Electrolytic polishing removed the attached powder and reduced the surface roughness Ra from 1.36 µm to 0.82 µm. The axial shortening rate of the polished bracket was 4.23% when the outside diameter was expanded from 2.42 mm to 3.63 mm under the pressure of the balloon, and the radial rebound rate was 2.48% after unloading. The radial force of polished stent was 8.32 N. The 3D printed vascular stent can remove the surface powder through electrolytic polishing to improve the surface quality, and show good dilatation performance and radial support performance, which provides a reference for the practical application of 3D printed vascular stent.

Effect of balloon pre-dilation on performance of self-expandable nitinol stent in femoropopliteal artery.

Balloon pre-dilation is usually performed before implantation of a nitinol stent in a femoropopliteal artery in a case of severe blockage or calcified plaque. However, its effect on performance of the nitinol stent in a diseased femoropopliteal artery has not been studied yet. This study compares the outcomes of stenting with pre-dilation and without it by modelling the entire processes of stent deployment. Fatigue deformation of the implanted stent is also modelled under diastolic-systolic blood pressure, repetitive bending, torsion, axial compression and their combination. Reduced level of stress in the stent occurs after stenting with pre-dilation, but causing the increased damage in the media layer, i.e. the middle layer of the arterial wall. Generally, pre-dilation increases the risk of nitinol stent's fatigue failure. Additionally, the development of in-stent restenosis is predicted based on the stenting-induced tissue damage in the media layer, and no severe mechanical irritation is induced to the media layer by pre-dilation, stent deployment or fatigue loading.

In silico evaluation of additively manufactured 316L stainless steel stent in a patient-specific coronary artery.

Additive manufacturing (AM) is an emerging method for the fabrication of stents, which is cost-saving and capable of producing personalised stent designs. However, poor surface finish and dimension discrepancy in the manufactured stents can significantly affect not only their own mechanical behavior but also mechanical response of arteries. This study investigates the effects of surface irregularities and dimension discrepancy of a 316L stainless steel stent, manufactured using laser powder bed fusion (LPBF), on its biomechanical performance, in comparison with the original design and a commercial stent. In silico simulations of stent deployment in a patient-specific coronary artery, based on intravital optical coherency tomography imaging, are conducted to assess the stent deformation as well as arterial stress and damage. Severe plastic strain concentrations (with a maximum value of 1.93) occur in the LPBF stent after deployment due to surface irregularities, suggesting a high risk of stent fracture. The LPBF stent is harder to expand due to its thicker struts and closed-cell design (diameter of 4.14 mm at the peak inflating pressure during deployment, compared to 4.58 mm and 4.65 mm for the designed and MULTI-LINK RX ULTRA stents, respectively). Also, the LPBF stent induces a higher level of stress concentration (with a maximum value of 23.04 MPa) to the arterial layers, suggesting a higher risk of tissue damage and in-stent restenosis. This study demonstrates a clear need for further development of the AM process for manufacturing medical implants, especially the surface finish and dimension accuracy.

Improved PGC demodulation algorithm to eliminate modulation depth and intensity disturbance.

In this paper, an improved phase generated carrier (PGC) demodulation algorithm based on frequency mixing and division difference is proposed. The effects of phase modulation depth variation and light intensity disturbance of the light source on the demodulated phase signal are investigated theoretically and experimentally. Compared to the traditional PGC differential-cross-multiplying (PGC-DCM) and PGC arctangent (PGC-Arctan) demodulation algorithms, the ameliorated demodulation algorithm eliminates the harmonic distortion of the demodulated signal by extracting the carrier modulation depth through frequency mixing. The demodulation error caused by the light intensity disturbance of the light source is suppressed by division difference. The stability of the demodulation system is improved. To verify the algorithm, a PGC demodulation system is built based on a Michelson interferometer. The experimental results show that when the frequency and amplitude of the sensed signal are set to 1 kHz and 0.4 rad, respectively, the signal-to-noise ratio with the proposed algorithm achieves a gain of 35.66 dB over the PGC-Arctan algorithm and 26.26 dB over the PGC-DCM algorithm.

Plan-Do-Check-Action Circulation Combined with Accelerated Rehabilitation Nursing under Computed Tomography in Prevention and Control of Hospital Infection in Elderly Patients Undergoing Elective Orthopedic Surgery.

To explore the adoption of plan-do-check-action (PDCA) circulation combined with accelerated rehabilitation nursing based on gemstone spectral imaging computed tomography (GSICT) in the prevention and control of hospital infection in the elderly patients undergoing the elective orthopedic surgery, 80 elderly patients who underwent the elective orthopedic surgery in the hospital were selected. Then, according to the randomized controlled principle, these 80 patients were divided into control group (40 cases) with conventional nursing and observation group (40 cases) with accelerated rehabilitation surgical nursing combined with PDCA circulation. All the patients underwent the GSICT examination without any contraindicators. Compared with the conventional CT scan, metal artifacts in GSICT were considerably reduced. In the images processed by GSI and metal artifacts reduction system (MARS), metal artifacts were basically eliminated and the positions, forms, and edges of metal artifacts in the human body were clearly presented. Hospital infection occurred in 1 (2.5%) patient in the observation group and 5 (12.5%) patients in the control group, and the difference was statistically significant (P < 0.05). In terms of temperature increase, patients in control group (37.5%) had a remarkably higher value than that of observation group (7.5%). The increase rate of white blood cell (WBC) count in control group (12.5%) was obviously higher than that in observation group (2.5%). Besides, the differences were statistically significant (P < 0.05). After PDCA circulation combined with accelerated rehabilitation nursing mode was applied, the hospitalization time of observation group (5.3 ± 2.4 days) was markedly lower than that of control group (9.7 ± 3.8 days). Moreover, the total hospitalization cost of observation group (791.44 yuan) was notably lower than that of control group (4068.96 yuan), with significant differences (P < 0.05). Nursing satisfaction in observation group (92.5%) was higher than that in control group (77.5%), and the difference was statistically significant (P < 0.05). In short, GSICT could effectively reduce beam hardening artifacts and metal implant artifacts and improve image quality. Furthermore, accelerated rehabilitation nursing combined with PDCA circulation could effectively reduce the incidence of hospital infection and improve nursing satisfaction.

Personalised nitinol stent for focal plaques: Design and evaluation.

The purpose of this study is to develop personalised nitinol stents for arteries with one and two opposite focal plaques. Novel designs are evaluated through comparison with a commercial stent design, in terms of lumen gain and shape as well as stress levels in the media layer after stenting. METHODS: Personalised stents are developed for arteries with one and two opposite focal plaques, based on medical imaging of patients and computer simulations. In silico analysis is then carried out for assessment of stent performance in the diseased arteries. RESULTS: Personalised designs significantly increase the lumen gain, reduce the stresses in the media layer, and improve the lumen shape compared to the commercial nitinol stent. CONCLUSION: The personalised designs show outstanding performance compared to the commercial stent. SIGNIFICANCE: This pilot study proves that personalised nitinol stents are able to deliver desirable treatment outcomes.

Fracture Toughness of Three-Dimensional Stereolithography Printed Polymer Reinforced with Continuous Carbon Fibers.

Additive manufacturing of fiber-reinforced polymers is one of the latest technical developments in composites manufacturing. However, there is a severe shortage of research into continuous fiber-reinforced polymers manufactured through stereolithography. For the first time, this article investigates the fracture properties of continuous carbon fiber-reinforced polymer produced by three-dimensional stereolithography printing. Compact tension (CT) specimens, both plain and fiber reinforced, were produced and tested systematically. The results showed a significant improvement in fracture toughness for fiber-reinforced specimens when compared with plain ones. The positioning of fiber bundles had a substantial effect on fracture properties, and a higher fracture toughness was reported for specimens with the fiber bundle placed closer to the crack tip. By increasing the number of fiber bundles, a significant increase in fracture toughness was reported when compared with the sample with a single fiber bundle, indicating a strong contribution of fiber volume. Also, the contribution appeared to be most effective when the fiber bundles were placed symmetrically in the thickness direction. The study is of importance and value for the development of the stereolithography technique in manufacturing continuous fiber-reinforced composites with enhanced mechanical properties.

Pioneering personalised design of femoropopliteal nitinol stents.

BACKGROUND/MOTIVATION: Percutaneous femoropopliteal artery intervention moves towards personalised therapy, which requires design of unique lesion-specific stents. However, to date, not much progress has been made in the development of personalised stents. OBJECTIVE: This paper aims to design personalised nitinol stents for femoropopliteal arteries based on medical imaging of patients and advanced computational mechanics, which is the first attempt to the authors' best knowledge. METHODS: The design process is based on three objectives: (i) achieving the healthy lumen area; (ii) reducing the stress in the media layer; (iii) improving the lumen shape after stenting. The design parameters include the strut width and thickness, the crown length, the nominal radius and the number of strut units per crown. Using representative unit-cell models, the effects of the five geometric parameters on the stent performance are investigated thoroughly with numerical simulations. Then, design protocols, especially for the circumferentially varying strut size and the oval stent shape, are developed and fully evaluated for an asymmetric stenosis. RESULTS: Using the design protocols, full personalised stents are designed for arteries with diffuse and focal plaques, based on medical imaging of patients. The personalised stent designs provide a double lumen gain, a reduced stress in the media layer and an improved lumen shape compared to a commercial stent. CONCLUSIONS: The suggested protocols prove their high effectiveness in design of personalised stents, and the suggested approach can be applied to development of personalised therapies involving the use of stent technology including percutaneous coronary artery intervention, transcatheter aortic valve implantation, endovascular aneurysm repair and ureteric stenting.

Mechanistic evaluation of long-term in-stent restenosis based on models of tissue damage and growth.

Development and application of advanced mechanical models of soft tissues and their growth represent one of the main directions in modern mechanics of solids. Such models are increasingly used to deal with complex biomedical problems. Prediction of in-stent restenosis for patients treated with coronary stents remains a highly challenging task. Using a finite element method, this paper presents a mechanistic approach to evaluate the development of in-stent restenosis in an artery following stent implantation. Hyperelastic models with damage, verified with experimental results, are used to describe the level of tissue damage in arterial layers and plaque caused by such intervention. A tissue-growth model, associated with vessel damage, is adopted to describe the growth behaviour of a media layer after stent implantation. Narrowing of lumen diameter with time is used to quantify the development of in-stent restenosis in the vessel after stenting. It is demonstrated that stent designs and materials strongly affect the stenting-induced damage in the media layer and the subsequent development of in-stent restenosis. The larger the artery expansion achieved during balloon inflation, the higher the damage introduced to the media layer, leading to an increased level of in-stent restenosis. In addition, the development of in-stent restenosis is directly correlated with the artery expansion during the stent deployment. The correlation is further used to predict the effect of a complex clinical procedure, such as stent overlapping, on the level of in-stent restenosis developed after percutaneous coronary intervention.

In Vitro Study of Bond Strength Between Abutments with Different Degrees of Convergence and Crowns by Pre-Bonding Method.

PURPOSE: To investigate the optimal degree of convergence of the abutment with which the bond strength achieved by the pre-bonding method is comparable with that in direct bonding with a conventional degree of convergence. MATERIALS AND METHODS: Abutments with 5.5-mm diameter, 5-mm height, 0.5-mm shoulder width, and three kinds of degrees of convergence (2, 4, and 6 degrees) were first designed by digital modeling. Their corresponding inner crowns were also modeled, and a gap of 40 µm was kept between the abutment and the inner crown. Thirty abutments and 30 inner crowns were then lathed out from a titanium plate (10 sets per degree of convergence). Six groups were defined in this study, according to the different degrees of convergence and bonding methods (direct bonding, pre-bonding) (n = 10 sets). The samples handled with direct bonding would be cleaned for reuse in tests with pre-bonding. Temporary cement was used as an adhesive, and the bond strength was tested in each set of samples. The comparison among the results was performed by the Kruskal-Wallis test. RESULTS: The mean values of bond strength with direct bonding methods were 349.39 ± 65.75 N, 316.49 ± 54.22 N, and 277.49 ± 56.96 N, and with pre-bonding methods were 279.35 ± 48.58 N, 227.97 ± 26.72 N, and 154.6 ± 23.03 N, respectively (2, 4, and 6 degrees). No statistical difference was found among the values in direct bonding groups and, in pre-bonding groups, only the comparison between 2 and 6 degrees of convergence showed statistical significance (P = .000). Between different bonding methods, statistical differences were shown in abutments with 4 and 6 degrees of convergence (P = .006, P = .000), respectively. The bond strength with pre-bonding methods and 2 degrees of convergence showed no significant difference from that with direct bonding and 6 degrees of convergence. CONCLUSION: The bond strength was inversely proportional to the degree of convergence, and the bond strength of pre-bonding was lower than that of direct bonding with the same degree of convergence. When using the pre-bonding method, the bond strength between the abutment and inner crown with 2 degrees of convergence could be comparable with using the direct bonding method and abutments with conventional degrees of convergence.

Effect of Rolling Route on Microstructure and Tensile Properties of Twin-Roll Casting AZ31 Mg Alloy Sheets.

Twin-roll casting AZ31 Mg alloy sheets have been fabricated by normal unidirectional-rolling, head-to-tail rolling, and clock-rolling, respectively. It has been demonstrated that head-to-tail rolling is the most effective to refine the microstructure and weaken the basal texture among the three rolling routes. Excellent integrated tensile properties can be obtained by the head-to-tail rolling. The yield strength, ultimate tensile strength, and plastic elongation are 196 MPa, 301 MPa, and 28.9%, respectively. The strength can benefit from the fine grains (average value of 4.0 µm) of the AZ31 alloy processed by the head-to-tail rolling route, while the excellent plastic elongation is achieved owing to the weakened basal texture besides the fine grains. Results obtained here can be used as a basis for further study of some simple rolling methods, which is critical to the development of Mg alloys with high strength and plasticity.

Study of novel chitosan-gelatin artificial skin in vitro.

A novel absorbable scaffold composed of chitosan and gelatin was fabricated by freezing and lyophilizing methods, resulting in an asymmetric structure. This bilaminar texture is suitable for preparing a bilayer skin substitute. The methods employed to confirm the applicability of this chitosan-gelatin scaffold as an ideal skin substitute were a water uptake ability test, in vitro fibroblast proliferation, and scaffold tests in which fibroblasts were co-cultured with keratinocytes. The chitosan-gelatin scaffolds were more wettable and adsorbed more water than did chitosan alone. In static cell culture the thinner scaffold is better than the thicker one, and because of diffusion limitations in the scaffold, culture time must be within 3 weeks before transplantation to living tissues. Keratinocytes were co-cultured with fibroblasts in chitosan-gelatin scaffolds to construct an artificial bilayer skin in vitro. The artificial skin obtained was flexible and had good mechanical properties. Moreover, there was no contraction observed in the in vitro cell culture tests. The data from this study suggest that chitosan-gelatin scaffolds are suitable for skin tissue engineering goals.