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PubMed2004

Dosimetric properties of magnetically collimated electron beams for radiation therapy.

A method of generating magnetically collimated electron beams is developed and the dosimetric properties of magnetically collimated electrons are investigated. An in-air magnetic collimator device was designed and constructed for the study. The magnetic collimator was placed above the exit port of a 14 x 14 cm2 electron cone. Axial magnetic field of approximately 0.6 Tesla is generated inside the collimator via an array of permanent magnets. Fixed and rotational magnetically collimated electron beams were delivered and measured in phantoms. We found that magnetically collimated electron beams significantly lower the surface dose as compared with conventional electron beams. A magnetically collimated arc beam further reduces the surface dose to less than 20% of the maximum dose inside the target. The dose per monitor unit at d(max) for the magnetically collimated electron beams was significantly (approximately 40%) higher than that of the conventional electron beams. The use of magnetic collimation may lead to improved delivery techniques for breast and head and neck cancer treatments.

Electrons↗
PubMed1996

Assessment of coronary artery stenosis by magnetic resonance imaging.

OBJECTIVE: The findings of magnetic resonance and x-ray angiography were compared for assessment of coronary artery stenosis in this validation study. BACKGROUND: Magnetic resonance angiography of the coronary arteries has recently been described, but there has been no comparison with x-ray angiography of localisation or assessment of important characteristics of coronary stenosis. METHODS: A breath hold, segmented k-space, 2D gradient echo imaging technique incorporating fat suppression was used in 39 patients (55 coronary stenoses) with known coronary artery disease. RESULTS: Overall, 47 stenoses (85%) were assessed by magnetic resonance (29 of 33 stenoses in the left anterior descending artery, one of one in the left main stem, 14 of 17 in the right coronary artery, and three of four in the left circumflex artery were detected). There was close agreement between magnetic resonance and x-ray angiography for the distance of the stenosis from the arterial origin (magnetic resonance mean (SD) 27 (16) mm versus x-ray angiography 27 (16) mm, P = NS, mean difference -0.2 mm). The distance to 39 stenoses (83%) agreed to within 5 mm, with increased scatter for more distal stenoses. The severity of magnetic resonance signal loss, assessed visually at the site of stenosis, varied significantly according to the percentage diameter stenosis (F = 30, P < 0.0001); stenosis severity with severe signal loss was 89 (7)%, with partial signal was 70 (16)%, and with irregular wall only 37 (11)%, with significant differences among the three groups (P < 0.001). A significant correlation was found between the proportional magnetic resonance signal loss at the stenosis and the percentage diameter stenosis severity (r = -0.67, P < 0.0001). The length of stenosis measured by magnetic resonance (6 (3) mm) was greater than by x-ray angiography (5 (2) mm, P < 0.006, mean difference +1.1 mm). Spearman's rank test showed that there was significant overestimation of stenosis length by magnetic resonance as stenosis severity increased (rs = 0.34, P < 0.02). CONCLUSIONS: Accurate localisation of coronary stenosis and a qualitative assessment of stenosis severity are possible by magnetic resonance, but stenosis length is overestimated as severity increases, probably because of disturbed patterns of flow with turbulence distal to severe stenoses. Reasonable results for the detection of coronary artery stenosis by magnetic resonance were achieved in this highly selected population, but further progress in imaging techniques is necessary before moving towards appreciable clinical application.

Angina Pectoris↗
PubMed2002

Novel, magnetically guided catheter for endocardial mapping and radiofrequency catheter ablation.

BACKGROUND: Ablation of complex arrhythmias would be greatly facilitated by more precise control of ablation catheters. A feasibility study was performed in animals to evaluate a novel magnetic guidance system (MGS) that generates a magnetic field to control the movement and position of a magnetic ablation catheter. METHODS AND RESULTS: The MGS is composed of a digital biplanar fluoroscope within an array of superconducting electromagnets that surround the torso of the experimental animal and a computer control system that generates a composite magnetic field for directional catheter deflection. Magnetic catheter navigation was performed in dogs and pigs (20 to 30 kg). A 7F magnetic ablation catheter was used for intracardiac navigation and radiofrequency ablation. The performance of a standard 7F deflectable catheter was not affected by the MGS. The magnetic catheter was navigated successfully to 51 predefined targets throughout the heart in 6 animals. In 5 animals, the magnetic catheter, guided by a 3D computed tomogram, was successfully navigated to all pulmonary veins. Navigation accuracy was estimated as <1 mm displacement from the target. The magnetic catheter was used to ablate the atrioventricular node in 4 animals and to perform linear ablations across the endocardial surface underlying an epicardial multielectrode recording plaque in 4 animals. CONCLUSIONS: These results demonstrate that the MGS can navigate and stabilize an ablation catheter at endocardial targets. Linear or focal radiofrequency ablation with the magnetic catheter is not compromised by the magnetic field. This technology provides precise control of endocardial catheters.

Animals↗
PubMedDate not supplied

Inductive heating of ferrimagnetic particles and magnetic fluids: physical evaluation of their potential for hyperthermia.

The potential of colloidal subdomain ferrite particle suspensions (SDP) ('magnetic fluids'), exposed to an alternating magnetic field, is evaluated for hyperthermia. Power absorption measurements of different magnetic fluids are presented in comparison to multidomain ferrite particles (MDP). Variations with frequency as well as magnetic field strength have been investigated. The experimental results clearly indicate a definite superiority of even non-optimized magnetic fluids over MDP ferrites regarding their specific absorption rate (SAR). Based on the work of Shliomis et al. (1990) and Hanson (1991), a solid-state physical model is applied to explain the specific properties of magnetic fluids with respect to a possible use in hyperthermia. The experimentally determined SAR data on magnetic fluids are used to estimate the heating capabilities of a magnetic induction heating technique assuming typical human dimensions and tissue parameters. It is considered that for a moderate concentration of 5 mg ferrite per gram tumour (i.e. 0.5% w/w) and clinically acceptable magnetic fields, intratumoral power absorption is comparable to RF heating with local applicators and superior to regional RF heating (by comparison with clinical SAR measurements from regional and local hyperthermia treatments). Owing to the high particle density per volume, inductive heating by magnetic fluids can improve temperature distributions in critical regions. Furthermore, localized application of magnetic fluids in a tumour might be easier and less traumatic than interstitial implantation techniques.

Colloids↗
PubMed2004

Magnetizable needles and wires--modeling an efficient way to target magnetic microspheres in vivo.

The in vivo targeting of tumors with magnetic microspheres is currently realized through the application of external non-uniform magnetic fields generated by rare-earth permanent magnets or electromagnets. Our theoretical work suggests a feasible procedure for local delivery of magnetic nano- and microparticles to a target area. In particular, thin magnetizable wires placed throughout or close to the target area and magnetized by a perpendicular external uniform background magnetic field are used to concentrate magnetic microspheres injected into the target organ's natural blood supply. The capture of the magnetic particles and the building of deposits thereof in the blood vessels of the target area were modeled under circumstances similar to the in vivo situation. This technique could be applied to magnetically targeted cancer therapy or magnetic embolization therapy with magnetic particles that contain anticancer agents, such as chemotherapeutic drugs or therapeutic radioisotopes.

Antineoplastic Agents↗
PubMed2001

Modulation of radiotherapy photon beam intensity using magnetic field.

The purpose of this study was to explore the potential advantages of using strong magnetic fields to increase tumor dose and to decrease normal tissue dose in radiation therapy. Strong magnetic fields are capable of altering the trajectories of charged particles. A magnetic field applied perpendicularly to the X-ray beam forces the secondary electrons and positrons to spiral and produces a dose peak. The same magnetic field also prevents the electrons and positrons from traveling downstream and produces a lower dose region distal to the dose peak. The locations of these high- and low-dose regions are potentially adjustable to enhance the dose to the target volume and decrease the dose to normal tissues. We studied this effect using the Monte Carlo simulation technique. The EGS4 code was used to simulate the effect produced by a coil magnet currently under construction. The coil magnet is designed to support up to 350 A operating current and 15 T peak field on windings. Dose calculations in a water phantom show that the transverse magnetic field produces significant dose effects along the beam direction of radiation therapy X-rays. Depending on the beam orientation, the radiation dose at different depths along the beam can be increased or reduced. This dose effect varies with photon energy, field size, magnetic field strength, and relative magnet/beam geometry. The off-axis beam profiles also show considerable skewness under the influence of the magnetic field. The magnetic field-induced dose shift may result in high dose regions outside the geometrical boundary of the initial radiation beam. We have demonstrated that current or near-term magnet technology is capable of producing significant dose enhancement and reduction in radiation therapy photon beams. This technology should be further developed to improve our ability to deliver higher doses to the tumor and lower doses to normal tissues in radiation therapy.

Electromagnetic Fields↗
PubMed2001

Interplay of magnetism and high-Tc superconductivity at individual Ni impurity atoms in Bi2Sr2CaCu2O8+delta.

Magnetic interactions and magnetic impurities are destructive to superconductivity in conventional superconductors. By contrast, in some unconventional macroscopic quantum systems (such as superfluid 3He and superconducting UGe2), the superconductivity (or superfluidity) is actually mediated by magnetic interactions. A magnetic mechanism has also been proposed for high-temperature superconductivity. Within this context, the fact that magnetic Ni impurity atoms have a weaker effect on superconductivity than non-magnetic Zn atoms in the high-Tc superconductors has been put forward as evidence supporting a magnetic mechanism. Here we use scanning tunnelling microscopy to determine directly the influence of individual Ni atoms on the local electronic structure of Bi2Sr2CaCu2O8+delta. At each Ni site we observe two d-wave impurity states of apparently opposite spin polarization, whose existence indicates that Ni retains a magnetic moment in the superconducting state. However, analysis of the impurity-state energies shows that quasiparticle scattering at Ni is predominantly non-magnetic. Furthermore, we show that the superconducting energy gap and correlations are unimpaired at Ni. This is in strong contrast to the effects of non-magnetic Zn impurities, which locally destroy superconductivity. These results are consistent with predictions for impurity atom phenomena derived from a magnetic mechanism.

Journal Article↗
PubMed2006

Hidden magnetism and quantum criticality in the heavy fermion superconductor CeRhIn5.

With only a few exceptions that are well understood, conventional superconductivity does not coexist with long-range magnetic order (for example, ref. 1). Unconventional superconductivity, on the other hand, develops near a phase boundary separating magnetically ordered and magnetically disordered phases. A maximum in the superconducting transition temperature T(c) develops where this boundary extrapolates to zero Kelvin, suggesting that fluctuations associated with this magnetic quantum-critical point are essential for unconventional superconductivity. Invariably, though, unconventional superconductivity masks the magnetic phase boundary when T < T(c), preventing proof of a magnetic quantum-critical point. Here we report specific-heat measurements of the pressure-tuned unconventional superconductor CeRhIn5 in which we find a line of quantum-phase transitions induced inside the superconducting state by an applied magnetic field. This quantum-critical line separates a phase of coexisting antiferromagnetism and superconductivity from a purely unconventional superconducting phase, and terminates at a quantum tetracritical point where the magnetic field completely suppresses superconductivity. The T --> 0 K magnetic field-pressure phase diagram of CeRhIn5 is well described with a theoretical model developed to explain field-induced magnetism in the high-T(c) copper oxides, but in which a clear delineation of quantum-phase boundaries has not been possible. These experiments establish a common relationship among hidden magnetism, quantum criticality and unconventional superconductivity in copper oxides and heavy-electron systems such as CeRhIn5.

Journal Article↗
PubMed2004

Substantial reduction of critical current for magnetization switching in an exchange-biased spin valve.

Great interest in current-induced magnetic excitation and switching in a magnetic nanopillar has been caused by the theoretical predictions of these phenomena. The concept of using a spin-polarized current to switch the magnetization orientation of a magnetic layer provides a possible way to realize future 'current-driven' devices: in such devices, direct switching of the magnetic memory bits would be produced by a local current application, instead of by a magnetic field generated by attached wires. Until now, all the reported work on current-induced magnetization switching has been concentrated on a simple ferromagnet/Cu/ferromagnet trilayer. Here we report the observation of current-induced magnetization switching in exchange-biased spin valves (ESPVs) at room temperature. The ESPVs clearly show current-induced magnetization switching behaviour under a sweeping direct current with a very high density. We show that insertion of a ruthenium layer between an ESPV nanopillar and the top electrode effectively decreases the critical current density from about 10(8) to 10(7) A cm(-2). In a well-designed 'antisymmetric' ESPV structure, this critical current density can be further reduced to 2 x 10(6) A cm(-2). We believe that the substantial reduction of critical current could make it possible for current-induced magnetization switching to be directly applied in spintronic devices, such as magnetic random-access memory.

Journal Article↗
PubMed2003

Induction of kinetochore-positive and kinetochore-negative micronuclei in CHO cells by ELF magnetic fields and/or X-rays.

To test the genotoxic effects of extremely low frequency (ELF) magnetic fields, the induction of micronuclei by exposure to ELF magnetic fields and/or X-rays was investigated in cultured Chinese hamster ovary (CHO) cells, using the cytokinesis block method. Micronuclei derived from acentric fragments or from whole chromosomes were evaluated by immunofluorescent staining using anti-kinetochore antibodies from the serum of scleroderma (CREST syndrome) patients. A 60 Hz ELF magnetic field at 5 mT field strength was applied, either before or after 1 Gy X-ray irradiation or without additional X-ray irradiation. No statistically significant difference in the frequency of micronuclei in CHO cells was observed between a sham exposure (no exposure to an ELF magnetic field) and a 24 h ELF magnetic field exposure. Exposure to an ELF magnetic field for 24 h before X-ray irradiation or for 18 h after X-ray irradiation did not affect the frequency of X-ray-induced micronuclei. However, the number of kinetochore-positive micronuclei was significantly increased in the cells subjected to X-ray irradiation followed by ELF magnetic field exposure, but not in the cells treated with ELF magnetic field exposure before X-ray irradiation, compared with exposure to X-rays alone. The number of spontaneous kinetochore-positive and kinetochore-negative micronuclei was not affected by exposure to an ELF magnetic field alone. Our data suggest that exposure to an ELF magnetic field has no effect on the number of spontaneous and X-ray-induced micronuclei. However, ELF magnetic field exposure after but not before X-ray irradiation may somehow accelerate X-ray-induced lagging of whole chromosomes (or centric fragments) in CHO cells.

Animals↗
PubMed2005

Revising the Essentials of Magnetism tool: there is more to adequate staffing than numbers.

In the Essentials of Magnetism (EOM) study, staff nurses in 9 of 16 hospitals known to have excellent staffing structures, ie Magnet hospitals, perceived staffing on their units as less than adequate. These hospitals did not fit the Magnet profile when compared to 26 Magnet, Magnet-aspiring, and non-Magnet hospitals. In the EOM study, the process "perception of adequacy of staffing" (PAS) was measured with a single-item indicator. A multi-item scale incorporating the results of a delivery system survey reported here, as well as other factors known to affect PAS, was constructed and evaluated. Results indicate that the 6-item PAS Scale is valid and reliable and is a more accurate measure of PAS than is a single-item indicator. The Magnet hospitals scored significantly higher on all 6 items of the scale than did the comparison hospitals. The 2 Magnet hospitals that did not score in the Magnet profile in the EOM study scored similarly to the Magnet hospital that scored very high in the Magnet profile. Measurement of the PAS process indicates whether staffing structures are viable and enabling and may account for the mixed results seen in some studies assessing the impact of staffing structures on patient outcomes. Discussion includes suggestions on how to promote smooth handoffs and accountability with flex delivery models, and emphasizes the need to evaluate the relationship between staff nurses' perceptions of adequate staffing and patient outcomes.

Analysis of Variance↗
PubMed2001

Studies of the magnetic structure at the ferromagnet-antiferromagnet interface.

Antiferromagnetic layers are a scientifically challenging component in magnetoelectronic devices, such as magnetic sensors in hard-disk heads, or magnetic random-access memory (RAM) elements. In this paper, it is shown that photoelectron emission microscopy (PEEM) is capable of determining the magnetic structure at the interface of ferromagnets and antiferromagnets with high spatial resolution (down to 20 nm). Dichroism effects at the L edges of the magnetic 3d transition metals, using circularly or linearly polarized soft X-rays from a synchrotron source, give rise to a magnetic image contrast. Images, acquired with the PEEM2 experiment at the Advanced Light Source, show magnetic contrast for antiferromagnetic LaFeO3, microscopically resolving the magnetic domain structure in an antiferromagnetically ordered thin film for the first time. Magnetic coupling between LaFeO3 and an adjacent Co layer results in a complete correlation of their magnetic domain structures. From field-dependent measurements, a unidirectional anisotropy resulting in a local exchange bias of up to 30 Oe in single domains could be deduced. The elemental specificity and the quantitative magnetic sensitivity render PEEM a perfect tool to study magnetic coupling effects in multilayered thin-film samples.

Journal Article↗
PubMed1998

Residential wire codes: reproducibility and relation with measured magnetic fields.

OBJECTIVES: To investigate the reproducibility of wire codes to characterise residential power line configurations and to determine the extent to which wire codes provide a proxy measure of residential magnetic field strength in a case-control study of childhood leukaemia conducted in nine states within the United States. METHODS: Misclassification of wire codes was assessed with independent measurements by two technicians for 187 residences. The association between categories of wire code and measured level of magnetic field was evaluated in 858 residences with both a wire code measurement and a 24 hour measurement of the magnetic field in the bedroom. The strength of the association between category of wire code and risk of leukaemia was examined in two regions with different average levels of magnetic field in homes with high categories of wire code. RESULTS: The reproducibility of any of three different classifications of wire codes was excellent (kappa > or = 0.89). Mean and median magnetic fields, and the percentage of homes with high magnetic fields increased with increasing category for each of the wire code classification schemes. The size of the odds ratios for risk of leukaemia and high categories of wire code did not reflect the mean levels of the magnetic field in those categories in two study regions. CONCLUSION: Misclassification of categories of wire code is not a major source of bias in the study. Wire codes provide a proxy measure of exposure to residential magnetic fields. If magnetic fields were a risk factor for leukaemia, however, there would be some attenuation of risk estimates based on wire codes because of misclassification of exposure to magnetic fields at both extremes of the wire code range. The lack of an association between high categories of wire code and risk of leukaemia cannot be explained by a failure of the wire code classification schemes to estimate exposure to magnetic fields in the study area.

Bias↗
PubMed2004

A biocompatible magnetic film: synthesis and characterization.

BACKGROUND: Biotechnology applications of magnetic gels include biosensors, targeted drug delivery, artificial muscles and magnetic buckles. These gels are produced by incorporating magnetic materials in the polymer composites. METHODS: A biocompatible magnetic gel film has been synthesized using polyvinyl alcohol. The magnetic gel was dried to generate a biocompatible magnetic film. Nanosized iron oxide particles (gamma-Fe2O3, ~7 nm) have been used to produce the magnetic gel. RESULTS: The surface morphology and magnetic properties of the gel films were studied. The iron oxide particles are superparamagnetic and the gel film also showed superparamagnetic behavior. CONCLUSION: Magnetic gel made out of crosslinked magnetic nanoparticles in the polymer network was found to be stable and possess the magnetic properties of the nanoparticles.

Journal Article↗
PubMed2003

Assessment of exposure to magnetic fields in occupational settings.

OBJECTIVE: It is important to have data about occupational magnetic field intensity to consider the contribution of occupational magnetic field exposure on the human body. We conducted research on exposure to occupational magnetic fields and tried to qualify data on the distribution of magnetic field' intensity in certain general working environments with individual measurements. SUBJECTS AND METHODS: We performed sample research on the exposure to low-frequency magnetic fields of workers in certain occupations and in the working environment. We also assessed the relationship between working environmental magnetic field distribution and individual exposure. RESULTS: Some occupations were found to be exposed to high magnetic fields. We observed that some workspaces, such as the transformer substation, generally had a uniform and high magnetic field measurement but employees were exposed to a lower intensity. We also found that welders were exposed to high magnetic fields at about 600 microT in a very short time but with a geometrical value of 0.08 microT. CONCLUSION: The determination of administrative levels and control levels, not only of the time weighted average of threshold limits or short term exposure limits, but also ceiling limits should be considered. More systematic research is necessary to determine variables such as operating conditions, measuring position, and frequency bands. Also, further studies will be needed to make a job-exposure matrix for the magnetic fields for each occupation type and to combine it with exposure in non-occupational settings such as commuting and ordinary life situations to explore the causal relationship between exposure to magnetic fields and disease.

Electromagnetic Fields↗
PubMedDate not supplied

Variability and consistency of electric and magnetic field occupational exposure measurements.

There is widespread scientific and public interest in possible health effects from exposure to electric and magnetic fields at frequencies associated with electricity use. Electric and magnetic field exposure assessment presents specific problems, among which are the inherent variability in exposure, the lack of robust statistical summary measures, and the lack of an accepted metric based on biological response. These pose challenges in defining distinct exposure groups, a basic goal for exposure assessments used in epidemiological studies. This paper explores the extent to which distinct electric and magnetic field exposure groups can be defined, by examining the variability and consistency of occupational electric and magnetic field exposure measurements among studies and within individual studies. Principal analyses are made by job titles because they are the most frequently used descriptors for stratifying occupational exposures to electric and magnetic fields. Methodological issues affecting the degree of consistency in measured electric and magnetic field exposures among occupational environments are also examined. Exposures by job title reported from electric and magnetic field measurement studies are summarized by general job category and industry. Analyses are performed both within and between job categories. Distributions of daily measured exposures for job categories taken from three large studies in the U.S. electric utility industry are compared to investigate consistency of exposures at a more detailed level. Analyses of reported personal exposure measurements from many studies and countries are consistent with less rigorous observations made heretofore on the basis of individual studies. In these studies, significantly elevated electric and magnetic field exposures are found in the electrician, lineworker, and substation worker categories; significantly elevated magnetic field exposures are also noted in the generation worker category; and magnetic field exposures in these groups are consistent across countries. Analyses within and among the elevated exposure job categories indicate that there are no significant differences between them. Among the studies, it is not possible to distinguish between exposures for well-defined groups within the categories, such as between transmission lineworkers and distribution lineworkers in the lineworker category; between generation operators and generation mechanics; or between substation operators and substation maintenance workers. This information provides a context for past studies and will help future efforts to define distinct occupational exposure groups exposed to electric and magnetic fields. Compilations of measured personal exposure data by industry and job title have been prepared as appendices (available from the author upon request).

Analysis of Variance↗
PubMed2004

Functional magnetic particles for medical application.

Magnetic particles for medical applications have been developed by many researchers. Since magnetic particles have unique magnetic features not present in other materials, they can be applied to special medical techniques. Separation, immunoassay, magnetic resonance imaging (MRI), drug delivery, and hyperthermia are enhanced by the use of magnetic particles. Magnetite cationic liposomes (MCLs), one of the groups of cationic magnetic particles, can be used as carriers to introduce DNA into cells since their positively charged surface associates with the negatively charged DNA. MCLs can also be used as heat mediators for cancer therapy. Magnetic particles conjugated with tumor-specific antibodies have enabled tumor-specific contrast enhancement in MRI. In addition, antibody-conjugated magnetic particles were shown to target renal cell carcinoma cells, and are applicable to the hyperthermic treatment of carcinomas. It was also found that the hyperthermic treatment using magnetic particles induced an antitumor immunity. Thus, the use of magnetic particles with their unique features will further improve medical techniques.

Animals↗
PubMedDate not supplied

Magnetic resonance imaging implications of metal-reinforced spinal microcatheters.

STUDY OBJECTIVE: To estimate the magnitude behavior of ferrous-alloy, wire-reinforced microcatheters for subarachnoid anesthesia and the possible hazards of exposing patients to magnetic resonance imaging (MRI) after accidental catheter fracture within the subarachnoid space. DESIGN: Open, qualitative in vitro study. SETTING: MRI facility of a university-affiliated medical center. MEASUREMENTS AND MAIN RESULTS: Measurements were made of the angular deflection of 28-gauge and 32-gauge TFX catheters from their resting alignment by a small bar magnet. Mobility of 28-gauge catheter fragments 3.0 to 3.5 cm in length and 3.3 to 4.0 mg in mass were tested (1) when lying free on a polished surface in an MRI magnetic field of 1.5 tesla and 60 cm from the magnetic casing, and (2) when mounted on a mildly viscous agar surface 40 to 50 cm from the magnetic casing. Catheters were attracted to a small bar magnet and could be pulled out of alignment by the magnetic attraction to a degree inversely proportional to their caliber. Catheter fragments released in a magnetic field of 1.5 tesla flew from a glass surface and attached themselves firmly to the magnet casing, while catheter fragments adhering to an agar surface were not levitated but were rotated from their resting orientation. CONCLUSIONS: The microcatheters under test exhibited marked magnetic properties. Two questions arise: First, should MRI be avoided in patients where broken TFX catheter fragments may lie partly or completely within the subarachnoid space? Second, should ferrous metallic strengthening wire be replaced by a nonmetallic fiber of comparable or greater tensile strength? Further in vitro studies are indicated to answer these questions.

Anesthesia, Spinal↗