Corrosion Behavior of Zn,Fe and Fe-Zn Powder Materials Prepared via Uniaxial Compression

Powder metallurgy is one of the most prevalent ways for metallic degradable materials preparation. Knowledge of the properties of initial powders used during this procedure is therefore of great importance. Two different metals, iron and zinc, were selected and studied in this paper due to their promising properties in the field of biodegradable implants. Raw powders were studied using scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDX). Powders (Fe, Zn and Fe-Zn in a weight ratio of 1:1) were then compressed at the pressure of 545 MPa to the form of pellets with a diameter of 1.7 cm. Surface morphology and degradation behavior in the Hanks´ solution were studied and evaluated. Electrochemical polarization tests along with the static immersion tests carried out for 21 days were employed for corrosion behavior characterization. The highest corrosion rate was observed for pure Zn powder followed by the Fe-Zn and Fe, respectively. A mixed Fe-Zn sample showed similar properties as pure zinc with no signs of iron degradation after 21 days due to the effect of galvanic protection secured by the zinc acting as a sacrificial anode.     

TRANSECTION OF METAL STENTS USING ARGON PLASMA COAGULATION

Background: Placement of self‐expandable metallic stents has become the preferred palliative treatment for patients with unresectable malignant biliary obstruction. Metallic stents provide longer patency compared with plastic stents. Distal malposition or migration of metallic stents sometimes occurs, but it is often difficult to remove them. We evaluated the efficacy and safety of argon plasma coagulation (APC), and the optimum conditions for cutting metallic stents (Wallstent). Methods: We wrapped porcine small intestines around a metallic Wallstent with and without silicon lining membrane (Permulume®), leaving the distal portion unwrapped to resemble the protrusion of the biliary metallic stent from the ampulla of Vater. APC irradiation was applied to the metallic stent at 1 cm from the edge of the wrapped small intestine at 30, 60 and 99 watts (W) for 3 or 6 s. Results: Metallic Wallstent with the silicone‐based membrane Permalume® was cut at 30 W power, whereas more than 60 W power was required to cut the bare metallic wire. The irradiation of APC (flow rate at 2.0 L/min) at 30 W to the covered metallic stent transected the metallic mesh stent not only under dry but also under wet conditions (moisturized stent). Irradiation of APC caused no gross damage to the small intestines irrespective of the power applied and duration of irradiation. Conclusions: Our results suggest that APC is efficacious and safe for endoscopic sectioning of wire mesh stents at low power (30 W) without gross damage to the surrounding pancreaticobiliary tissues.     

Contrast and nuclear arthrography in loosening of the uncemented hip prosthesis

The recent popularity of ingrowth or uncemented hip arthroplasties has presented problems in the radiographic diagnosis of loosening because there is no longer a cement interface in which lucencies may be seen. We evaluated a combination of positive contrast and nuclear arthrography to see whether these studies could accurately detect loosening of uncemented femoral components of hip prostheses. We performed routine contrast and nuclear arthrography in 21 patients with ingrowth total hip arthroplasties or bipolar endoprostheses. The results were surgically confirmed in 12 patients. The contrast arthrogram was true positive in 5 and false negative in 5. There were no false positives and 2 true negatives. The nuclear arthrogram was true positive in 7 patients, false negative in 3, and true negative in 2. Taken together, there was only 1 patient in whom both contrast and nuclear arthrography were false negative, and there were no false positives. Thus, when either contrast or nuclear arthrography is positive, the sensitivity of the combined procedures is 90%; when both studies are negative, the specificity is 100%. The combination of contrast and nuclear arthrography is an accurate method of determining loosening of the femoral component of an uncemented hip arthroplasty or bipolar endoprosthesis in the patient with postoperative hip pain.     

Interventional treatment of hepatic arterial and venous pathology: A commentary

Hepatic aneurysms, pseudoaneurysms and fistulas (arterial biliary and arterial portal) causing blecding or portal hypertension, and arteriovenous malformations causing high output cardiac failure in adults can be successfully managed by embolization techniques. Results of embolization in infantile hemangioendotheliomas are less uniform and tumors with massive arteriovenous shunting are difficult to manage. Transjugular intrahepatic portal systemic shunts using expendable stents have been successfully created in patients and have effectively controlled portal hypertension and variceal bleeding.     

Elective (planned) colectomy in patients with colorectal obstruction after placement of a self-expanding metallic stent as a bridge to surgery: the results of a prospective study

Introduction  Acute malignant colorectal obstruction (CRO) can be satisfactorily dealt by the placement of a self-expanding metallic stent (SEMS). The aim of this prospective study was to evaluate the rate of elective (planned) colectomy (EPC) in patients with CRO after SEMS placement as a bridge to surgery on an intention-to-treat (ITT) basis.
Method  From 2002 to 2007, 30 SEMS were placed as a bridge to surgery in 30 CRO patients (median age 73 ± 12 years). The obstructing lesions were located in the right ( n  = 1), transverse ( n  = 1) or left colon ( n  = 24) or the upper third of the rectum ( n  = 4).
Results  The SEMS was placed successfully in 25 (83%) patients. Five patients underwent Hartmann's procedure ( n  = 2) or a diverting colostomy ( n  = 3). The SEMS was functionally operational in 23 (92%) of the 25 patients. A diverting colostomy was avoided in 23 (77%) of the 30 patients (placement failure n  = 5, clinical failure n  = 2). There were no complications in 17 (80%) patients. On an ITT basis, 70% of the patients (21 out of 30) underwent an EPC.
Conclusion  On an ITT basis, SEMS placement in CRO patients enabled EPC in 70% of patients.     

Thresholds for perceiving metallic taste at high magnetic field

PURPOSE: To perform an initial characterization of the metallic taste effect observed by some workers when moving around an MRI scanner. MATERIALS AND METHODS: A total of 21 subjects performed controlled movements in the stray field of a 7-T scanner. Rates of change of magnetic flux were recorded during the study using a custom-built three-axis coil unit connected to a data logger. RESULTS: Relatively normal movements could generate switched fields of 2 T/second. Of the 21 subjects, 12 detected a metallic taste, but the threshold at which it was perceived varied greatly between subjects, with the minimum dB/dt value at which such a taste was detected being 1.3 T/second. The threshold also depended on the direction of movement. CONCLUSION: This study indicates that 50% of subjects will perceive a metallic taste for head shaking with a period of 1.5 seconds (magnetic field in an anterior/posterior direction) causing a dB/dt of 2.3 +/- 0.3 T/second. The presence of dental fillings is not a requirement for the sensation of metallic taste.     

高Z重金介质的肿瘤放疗增敏效应研究现状

目的：探讨高Z重金介质的放射剂量增强效应及其应用于肿瘤放疗增敏的研究历史、当前进展与未来发展方向。方法：全面检索高Z介质表面/界面的剂量效应及其用于肿瘤放疗增敏的早期研究和最新报道。针对近年来开展的重金介质放疗增敏相关研究,按照放疗射线类型和增敏效应研究手段分别进行总结述评,以把握该领域的发展历史和研究现状,并对现存的问题进行讨论和展望。结果：目前针对高Z重金介质的放疗增敏研究主要包括质粒DNA辐照、体外细胞辐照、动物肿瘤模型试验以及剂量学模拟等手段。针对传统X-γ射线放疗的增敏效应研究最为深入,针对同步辐射放疗、质子重离子放疗等先进放疗技术的重金增敏研究也有开展。研究结果已充分证明了重金介质的放射增敏效应及其用于肿瘤放疗增敏的可行性,为临床前试验的进一步开展提供了重要的理论和实验依据。结论：高Z重金介质的肿瘤放疗增敏效应研究近年来取得了较快的进展,部分研究已从增敏效应验证进入放疗试验的增敏参数优化和作用机理研究阶段,为实现其在临床肿瘤放疗中的应用,增敏效应的微观作用机理是必须深入研究的重要课题。