SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A novel microfluidic platform for manipulation of micro/nano magnetic particles was designed, fabricated and tested for applications dealing with biomolecular separation. Recently, magnetic immunomagnetic cell separation has attracted a noticeable attention due to the high selectivity of such separation methods. Strong magnetic field gradients can be developed along the entire wire, and the miniaturized size of these current-carrying conductors strongly enhances the magnetic field gradient and therefore produces large, tunable and localized magnetic forces that can be applied on magnetic particles and confine them in very small spots. Further increases in the values of the generated magnetic field gradients can be achieved by employing miniaturized ferromagnetic structures (pillars) which can be magnetized by an external magnetic field or by micro-coils on the same chip. In this study, we demonstrate magnetic beads trapping, concentration, transportation and sensing in a liquid sample under continuous flow by employing high magnetic field gradients generated by novel multi-functional magnetic micro-devices. Each individual magnetic micro-device consists of the following components: 1. Cu micro-coils array embedded in the silicon substrate with high aspect ratio conductors for efficient magnetic field generation 2. Magnetic pillar(s) made of the magnetic alloy NiCoP for magnetic field focusing and magnetic field gradient enhancement. Each pillar is magnetized by its corresponding coil 3. Integrated sensing coil for magnetic beads detection 4. Microfluidic chamber containing all the previous components. Magnetic fields of about 0.1 T and field gradients of around 300 T/cm have been achieved, which allowed to develop a magnetic force of 3 x 10(-9) N on a magnetic particle with radius of 1 mum. This force is large enough to trap/move this particle as the required force to affect such particles in a liquid sample is on the order of approximately pN. Trapping rates of up to 80% were achieved. Furthermore, different micro-coil designs were realized which allowed various movement modes and with different step-sizes. These results demonstrate that such devices incorporated within a microfluidic system can provide significantly improved spatial resolution and force magnitude for quick, efficient and highly selective magnetic trapping, separation and transportation, and as such they are an excellent solution for miniaturized mu-total analysis systems.
Magnetic forces have been incorporated into orthodontic mechanics during recent years. However, the biocompatibility of magnet alloys and the possible risk of harmful or unusual reactions in tissues exposed to static magnetic fields have been characterized as inconsistent and often contradictory. It has also been questioned whether magnetic forces have significant advantages over traditional mechanics. The present series of studies aimed to analyse the force and field properties, the biocompatibility and the clinical effects of rare earth magnets as well as to compare the efficiency of tooth movement between magnets and another force system. Samarium-cobalt magnets for molar distalization were tested in experimental models for force and field properties. The cytotoxicity of different magnet alloys (rare earth types) as well as of clinically used and recycled magnets was assessed by two in vitro methods, the millipore filter method and an extraction method. The effect of static magnetic fields on human gingival tissue and dental pulp was examined histologically for alterations in cell pattern and cell morphology. The effects of using repelling samarium-cobalt magnets for simultaneous distalization of maxillary first and second molars were analysed in individuals with Class II malocclusion. The efficiency of molar distalization was also intra-individually compared between repelling magnets and superelastic NiTi-coils in individuals with Class II malocclusion and deep bite. The magnet forces decreased approximately with the reciprocal square of the separation distance between the magnets. No fatigue of force over time could be seen. The static magnetic fields were weak and had a limited extent and the flux density dropped exponentially in all directions with increased distance from the magnets, implying a small exposure area when the magnets are used clinically. Rare earth magnets showed good biocompatibility, particularly coated magnets. However, uncoated samarium-cobalt magnets showed significant cytotoxicity. It was also found that stainless-steel-coated samarium-cobalt magnets could be recycled with maintained good biocompatibility. After exposure to static magnetic fields, normal clinical and histological conditions in the human gingival tissue and normal histological features in the human dental pulp were found. Repelling magnets were effective in producing maxillary molar distalization but some side effects like anchorage loss and molar tipping were found. The superelastic coils were shown to be even more efficient than the repelling magnets for maxillary molar distalization in individuals with Class II malocclusion and deep bite.
Electric and magnetic fields are associated with the production, transmission, and use of electricity; thus the potential for human exposure is high. These electric and magnetic fields are predominantly of low frequency (60 Hz) and generally of low intensity. The prevailing view among physicists is that exposure to these low-frequency, low-intensity fields does not pose a health hazard. However, this view has been challenged by reports linking magnetic field exposure to the development of leukemia and other cancers. Because multiple epidemiologic studies suggested a potential for increased cancer rates with increasing exposure, and because of public concern, the effects of 60-Hz magnetic field exposure were examined in F344/N rats and B6C3F1 mice in 8-week full-body-exposure studies. Animals were evaluated for hematology and clinical chemistry (rats only) parameters, pineal gland hormone concentrations, and histopathology. Additional studies were performed in Sprague-Dawley rats to examine teratologic and reproductive effects of magnetic field exposure. In the 8-week toxicity studies, groups of male and female F344/N rats and B6C3F1 mice were exposed for 18.5 hours per day to 60-Hz magnetic fields at intensities of 0 (control), 0.02, 2, and 10 gauss (G). Additional groups of rats and mice were exposed to intermittent 10 G fields (1 hour on/1 hour off) for 18.5 hours per day. No evidence of toxicity associated with exposure to magnetic fields was observed in rats or mice. Clinical observations provided no evidence of adverse effects associated with magnetic field exposure. Compared to control rats and mice, there were no biologically significant differences in hematology or clinical chemistry parameters of rats exposed to magnetic fields. No gross lesions or histopathologic findings in rats or mice were attributed to exposure to 60-Hz magnetic fields. In addition, magnetic field exposure was not associated with a significant reduction in serum melatonin or pineal gland melatonin concentration, or pineal gland activity of N-acetyltransferase in either species. One female rat in the 2 G exposure group died during the 8-week toxicity study from causes unrelated to magnetic field exposure; all other male and female rats and mice in the study survived until the end of the study. Final mean body weights and mean organ weights of a few groups of exposed animals differed from those of the control groups; however, no clear pattern of magnetic field effects was observed, and these differences are not considered to be biologically significant. For the teratology study, groups of 55 pregnant female Sprague-Dawley rats were exposed to the same magnetic fields as in the toxicity study on gestation days 6 through 19. Fifteen pregnant females exposed to 85 mg ethylenethiourea/kg body weight served as positive controls. Except for the positive controls, there were no changes in maternal or fetal weights, nor were fetal abnormalities found. The number of pregnant females was significantly lower in groups exposed to magnetic fields than in the control group; however, all breeding in the teratology study was completed prior to the first day of magnetic field or sham exposure. On this basis, this finding is unrelated to magnetic field exposure. In addition, there were no differences between control and exposed groups in the number of pregnant females in the continuous breeding study, in which breeding took place within the magnetic fields. Groups of 40 breeding pairs of Sprague-Dawley rats were exposed to the same magnetic fields as in the toxicity study during the breeding and lactation of five litters in a continuous breeding study. The fifth litter was exposed during gestation and lactation; one male and one female from each litter were raised to sexual maturity receiving the same exposures as the parents; rats were mated to nonsibling rats and allowed to deliver the third-generation offspring. The results of the continuous breeding study demonstrated no effects of magnetic field exposure on reproductive performance in either male or female rats.
To control the growth of primary tumors effectively with systemic chemotherapy, we recently developed intravenously administered small-sized magnetic liposomes as an anticancer drug carrier. We previously reported that intravenously administered magnetic liposomes with incorporated adriamycin (magnetic ADR liposomes) effectively delivered ADR to the target site where a permanent magnet was implanted. In the present study, the therapeutic efficacy of this novel treatment approach, which involves a combination of magnet implantation at the target site and intravenous administration of magnetic liposomes, was further evaluated by comparing tumor growth rates among different administration modalities and by histological examination of treated tumors. Small-sized magnetic ADR liposomes with a mean diameter of 146 nm were prepared by the reverse-phase evaporation method. Syrian male hamsters inoculated with osteosarcoma, Os515, in the right hind limb were studied 7 days after inoculation. One day prior to the animal study, either a permanent magnet (with magnetic force) or non-magnetic alloy (without magnetic force) was implanted in the center of the tumors. Treatment with magnetic ADR liposomes under magnetic force showed significantly greater antitumor activity than intravenous administration of ADR solution or that of magnetic ADR liposomes without magnetic force. ADR administered as magnetic liposomes eliminated weight loss of hamsters, one of the side effects produced by ADR. Interestingly, magnetic liposomes (without incorporated ADR) given under magnetic force also suppressed the tumor growth. The selective accumulation of magnetite particles in the tumor blood vessels was observed by histological examination. These results suggest that this systemic chemotherapy can effectively control the primary tumor without significant side effects, due to the targeting of magnetic ADR liposomes.
Electric and magnetic fields are associated with the production, transmission, and use of electricity; thus, the potential for human exposure is high. These elec-tric and magnetic fields are predominantly of low fre-quency (60 Hz in the United States and 50 Hz in Europe) and generally of low intensity. Because some epidemiology studies and initiation/promotion studies in rats have suggested a potential for increased breast cancer rates with increasing magnetic field exposure, the ability of 50- and 60-Hz magnetic fields to pro-mote mammary gland tumors initiated by the administration of 7,12-dimethylbenz(a)anthracene (DMBA) was examined in female Sprague-Dawley rats in 13- and 26-week whole-body exposure studies. Additional animals were evaluated for changes in pineal gland and serum melatonin concentrations. FIRST 13-WEEK STUDY: Groups of 100 female Sprague-Dawley rats were ad-ministered 20 mg DMBA (four weekly gavage doses of 5 mg in sesame oil) and exposed to 1 G 50-Hz, 5 G 50-Hz, or 1 G 60-Hz magnetic fields for 18.5 hours per day, 7 days per week, for 13 weeks. A group of 100 rats administered 20 mg DMBA served as DMBA controls. A group of 100 vehicle control rats was administered only sesame oil on the same schedule. Additional groups of 10 rats receiving similar treatment were evaluated for pineal gland and serum melatonin concentrations at 4, 8, or 12 weeks. All vehicle control rats survived to the end of the study. Of the animals administered 20 mg DMBA, 6 rats in the DMBA control group, 13 in the DMBA/1 G 50-Hz group, eight in the DMBA/5 G 50-Hz group, and five in the DMBA/1 G 60-Hz group died or were removed from the study prior to the final necropsy. Final mean body weights and body weight gains of the DMBA/1 G 50-Hz and DMBA/1 G 60-Hz groups and the mean body weight gain of the DMBA/5 G 50-Hz group were slightly greater than those of the DMBA control group. Clinical findings including torso masses and ulcers (on the mammary masses) were attributed to DMBA administration. The numbers of palpable mammary gland tumors, tumor sizes, and total tumor areas in DMBA/magnetic field groups were similar to those in the DMBA control group. Relative to the DMBA control group, exposure to magnetic fields did not significantly affect overall incidences of mammary gland neoplasms or nonneoplastic lesions in the DMBA/magnetic field groups. SECOND 13-WEEK STUDY: Groups of 100 female Sprague-Dawley rats were ad-ministered 8 mg DMBA (four weekly gavage doses of 2 mg in sesame oil) and exposed to 1 G 50-Hz or 5 G 50-Hz magnetic fields for 18.5 hours per day, 7 days per week, for 13 weeks. A group of 100 female rats administered 8 mg DMBA served as DMBA controls. Additional groups of 10 rats receiving similar treatment were evaluated for pineal gland and serum melatonin concentrations at 4, 8, or 12 weeks. Except for one rat in the DMBA/5 G 50-Hz group, all rats survived until the end of the study. Final mean body weights of DMBA/magnetic field groups were similar to those of the DMBA control group. Clinical findings including torso masses and ulcers were attributed to DMBA administration. The numbers of palpable mammary gland tumors, tumor sizes, and total tumor areas in DMBA/magnetic field groups were similar to those in the DMBA control group. Relative to the DMBA control group, exposure to magnetic fields did not significantly affect overall incidences of mammary gland neoplasms or nonneoplastic lesions in the DMBA/magnetic field groups. 26-WEEK STUDY: Groups of 100 female Sprague-Dawley rats were administered 10 mg DMBA (in sesame oil) by gavage followed by exposure to 1 G 50-Hz, 5 G 50-Hz, or 1 G 60-Hz magnetic fields for 18.5 hours per day, 7 days per week, for 26 weeks. A group of 100 female rats administered 10 mg DMBA served as DMBA controls. Another 100 vehicle control rats were administered only sesame oil. Additional groups of 10 rats receiving similar treatment were evaluated for pineal gland and serum melatonin concentrations at 4, 8, or 12 weeks. All rats in the vehicle control group survived until the end of the study. Twelve rats in the DMBA control group, 15 in the DMBA/1 G 50-Hz group, 9 in the DMBA/5 G 50-Hz group, and six in the DMBA/1 G 60-Hz group died or were removed during the study. The final mean body weights and body weight gains of the DMBA/1 G 50-Hz and DMBA/5 G 50-Hz groups were significantly greater than those of the DMBA control group. Clinical findings including torso masses, abscesses, and ulcers were attributed to DMBA administration. The pineal gland melatonin concentrations of DMBA/5 G 50-Hz and DMBA/1 G 60-Hz rats were significantly greater than that of the DMBA controls at week 12; however, these data were highly variable between individual animals within each group. The numbers of palpable mammary gland tumors, tumor sizes, and total tumor areas in DMBA/magnetic field groups were similar to those in the DMBA controls. The incidences of mammary gland carci-noma (including multiple) in the DMBA/1 G 60-Hz group were significantly decreased relative to the DMBA control group. CONCLUSIONS: In an initiation/promotion study in which female Sprague-Dawley rats were initiated by four weekly doses of 5 mg DMBA per rat beginning at 50 days of age and exposed to 50-Hz magnetic fields at 1 or 5 G field intensities or to 1 G 60-Hz magnetic fields for 13 weeks, there was no evidence that magnetic fields promoted the development of mammary gland neoplasms. The prevalence and multiplicity of mammary gland carcinomas in all DMBA groups limited the ability of this assay to detect a promoting effect of magnetic fields. In an initiation/promotion study in which female Sprague-Dawley rats were initiated by four weekly doses of 2 mg DMBA per rat beginning at 50 days of age and exposed to 50-Hz magnetic fields at 1 or 5 G field intensities for 13 weeks, there was no evidence that magnetic fields promoted the development of mammary gland neoplasms. In an initiation/promotion study in which female Sprague-Dawley rats were initiated by a single 10 mg DMBA dose at 50 days of age and then exposed to 50-Hz magnetic fields at 1 or 5 G field intensities or to 1 G 60-Hz magnetic fields for 26 weeks, there was no evidence that magnetic fields promoted the development of mammary gland neoplasms.
Aberration in the eruption process was found to be a prime etiologic factor in inducing impaction. Thus an ideal treatment approach should attempt to mimic the normal eruption modus. However, conventional traction methods have been found to be associated with gingiva inflammation, bone recession, reduced attached gingiva, periodontal pockets, exposed cementoenamel junction, and root resorption of the impacted and adjacent teeth. These side effects are the result of premature exposure of the impacted tooth to the oral cavity through a nonself-cleansing pathway and an uncontrolled force system. The present study introduces a new, magnetic attraction system, with a magnetic bracket bonded to an impacted tooth and an intraoral magnet linked to a Hawley type retainer. Vertical and horizontal magnetic brackets were designed, with the magnetic axis magnetized parallel and perpendicular to the base of the bracket, respectively. The vertical type is used for impacted incisors and canines, and the horizontal magnetic bracket is applied for impacted premolars and molars. A three-dimensional analysis of the magnetic force system, by means of the OMSS apparatus, found the small magnetic bracket combined with a large pole surface area of the intraoral magnet to exhibit the most efficient convergent guidance. For this report the magnetic eruption device was examined on one animal subject and four patients. The Nd2Fe14B magnets were coated with parylene and/or encapsulated in stainless steel housings. In deep impaction, the magnetic bracket was cold-sterilized before surgery, and the surgical mucoperiosteal flap was then sutured over the bonded magnetic bracket. Attraction was initiated 1 to 2 weeks after healing. Thus tooth emergence into the oral cavity replicated normal eruption conditioning. The system operated at an attractive force level of 0.2 to 0.5 N. Adjustment was accomplished by temporarily interposing a magnetic spacer between the two magnetic units. No side effects were observed in this restricted number of treated cases, and treatment time was reduced. The study recommends the application of magnets in the treatment of impaction on the grounds of less invasive surgical procedure, effective attractive forces at short distances, and controlled spatial guidance.
BACKGROUND: Electrical stimulation of the phrenic nerve is a useful non-volitional method of assessing diaphragm contractility. During the assessment of hemidiaphragm contractility with electrical stimulation, low twitch transdiaphragmatic pressures may result from difficulty in locating and stimulating the phrenic nerve. Cervical magnetic stimulation overcomes some of these problems, but this technique may not be absolutely specific and does not allow the contractility of one hemidiaphragm to be assessed. This study assesses both the best means of producing supramaximal unilateral magnetic phrenic stimulation and its reproducibility. This technique is then applied to patients. METHODS: The ability of four different magnetic coils to produce unilateral phrenic stimulation in five normal subjects was assessed from twitch transdiaphragmatic pressure (TwPDI) measurements and diaphragmatic electromyogram (EMG) recordings. The results from magnetic stimulation were compared with those from electrical stimulation. To determine whether the magnetic field affects the contralateral phrenic nerve as well as the intended phrenic nerve, EMG recordings from each hemidiaphragm were compared during stimulation on the same side and the opposite side relative to the recording electrodes. The EMG recordings were made from skin surface electrodes in five normal subjects and from needle electrodes placed in the diaphragm during cardiac surgery in six patients. Similarly, the direction of hemidiaphragm movement was evaluated by ultrasonography. To determine the usefulness of the technique in patients the 43 mm mean diameter double coil was used in 54 patients referred for assessment of possible respiratory muscle weakness. These results were compared with unilateral electrical phrenic stimulation, maximum sniff PDI, and TwPDI during cervical magnetic stimulation. RESULTS: In the five normal subjects supramaximal stimulation was established for eight out of 10 phrenic nerves with the 43 mm double coil. Supramaximal unilateral magnetic stimulation produced a higher TwPDI than electrical stimulation (mean (SD) 13.4 (2.5) cm H2O with 35 mm coil; 14.1 (3.8) cm H2O with 43 mm coil; 10.0 (1.7) cm H2O with electrical stimulation). Spread of the magnetic field to the opposite phrenic nerve produced a small amplitude contralateral diaphragm EMG measured from skin surface electrodes which reached a mean of 15% of the maximum EMG amplitude produced by ipsilateral stimulation. Similarly, in six patients with EMG activity recorded directly from needle electrodes, the contralateral spread of the magnetic field produced EMG activity up to a mean of 3% and a maximum of 6% of that seen with ipsilateral stimulation. Unilateral magnetic stimulation of the phrenic nerve was rapidly achieved and well tolerated. In the 54 patients unilateral magnetic TwPDI was more closely related than unilateral electrical TwPDI to transdiaphragmatic pressure produced during maximum sniffs and cervical magnetic stimulation. Unilateral magnetic stimulation eliminated the problem of producing a falsely low TwPDI because of technical difficulties in locating and adequately stimulating the nerve. Eight patients with unilateral phrenic nerve paresis, as indicated by a unilaterally elevated hemidiaphragm on a chest radiograph and maximum sniff PDI consistent with hemidiaphragm weakness, were all accurately identified by unilateral magnetic stimulation. CONCLUSIONS: Unilateral magnetic phrenic nerve stimulation is easy to apply and is a reproducible technique in the assessment of hemidiaphragm contractility. It is well tolerated and allows hemidiaphragm contractility to be rapidly and reliably assessed because precise positioning of the coils is not necessary. This may be particularly useful in patients. In addition, the anterolateral positioning of the coil allows the use of the magnet in the supine patient such as in the operating theatre or intensive care unit.
It has been reported previously that exposure to static high magnetic fields of 7 T or above in superconducting magnets has behavioral effects on rats. In particular, magnetic field exposure acutely but transiently suppressed rearing and induced walking in tight circles; the direction of circular locomotion was dependent on the rats' orientation within the magnet. Furthermore, when magnet exposure was paired with consumption of a palatable, novel solution, rats acquired a persistent taste aversion. In order to confirm these results under more controlled conditions, we exposed rats to static magnetic fields of 4 to 19.4 T in a 189 mm bore, 20 T resistive magnet. By using a resistive magnet, field strengths could be arbitrary varied from -19.4 to 19.4 T within the same bore. Rearing was suppressed after exposure to 4 T and above; circling was observed after 7 T and above. Conditioned taste aversion was acquired after 14 T and above. The effects of the magnetic fields were dependent on orientation. Exposure to +14 T induced counter-clockwise circling, while exposure to -14 T induced clockwise circling. Exposure with the rostral-caudal axis of the rat perpendicular to the magnetic field produced an attenuated behavioral response compared to exposure with the rostral-caudal axis parallel to the field. These results in a single resistive magnet confirm and extend our earlier findings using multiple superconducting magnets. They demonstrate that the behavioral effects of exposure within large magnets are dependent on the magnetic field, and not on non-magnetic properties of the machinery. Finally, the effects of exposure to 4 T are clinically relevant, as 4 T magnetic fields are commonly used in functional MRI assays.
The aim of this study was to evaluate the use of functional magnetic resonance imaging as an alternative to intraoperative electrocortical stimulation mapping for the localization of critical language areas in the temporoparietal region. We investigated several requirements that functional magnetic resonance imaging must fulfill for clinical implementation: high predictive power for the presence as well as the absence of critical language function in regions of the brain, user-independent statistical methodology, and high spatial accuracy. Thirteen patients with temporal lobe epilepsy performed four different functional magnetic resonance imaging language tasks (ie, verb generation, picture naming, verbal fluency, and sentence comprehension) before epilepsy surgery that included intraoperative electrocortical stimulation mapping. To assess the optimal statistical threshold for functional magnetic resonance imaging, images were analyzed with three different statistical thresholds. Functional magnetic resonance imaging information was read into a surgical guidance system for identification of cortical areas of interest. Intraoperative electrocortical stimulation mapping was recorded by video camera, and stimulation sites were digitized. Next, a computer algorithm indicated whether significant functional magnetic resonance imaging activation was present or absent within the immediate vicinity (<6.4mm) of intraoperative electrocortical stimulation mapping sites. In 2 patients, intraoperative electrocortical stimulation mapping failed during surgery. Intraoperative electrocortical stimulation mapping detected critical language areas in 8 of the remaining 11 patients. Correspondence between functional magnetic resonance imaging and intraoperative electrocortical stimulation mapping depended heavily on statistical threshold and varied between patients and tasks. In 7 of 8 patients, sensitivity of functional magnetic resonance imaging was 100% with a combination of 3 functional magnetic resonance imaging tasks (ie, functional magnetic resonance imaging correctly detected all critical language areas with high spatial accuracy). In 1 patient, sensitivity was 38%; in this patient, functional magnetic resonance imaging was included in a larger area found with intraoperative electrocortical stimulation mapping. Overall, specificity was 61%. Functional magnetic resonance imaging reliably predicted the absence of critical language areas within the region exposed during surgery, indicating that such areas can be safely resected without the need for intraoperative electrocortical stimulation mapping. The presence of functional magnetic resonance imaging activity at noncritical language sites limited the predictive value of functional magnetic resonance imaging for the presence of critical language areas to 51%. Although this precludes current replacement of intraoperative electrocortical stimulation mapping, functional magnetic resonance imaging can at present be used to speed up intraoperative electrocortical stimulation mapping procedures and to guide the extent of the craniotomy.
BACKGROUND: Recently we introduced the CellTracks cell analysis system, in which samples are prepared based on a combination of immunomagnetic selection, separation, and alignment of cells along ferromagnetic lines. Here we describe the underlying magnetic principles and considerations made in the magnetic field design to achieve the best possible cell selection and alignment of magnetically labeled cells. Materials and Methods Computer simulations, in combination with experimental data, were used to optimize the design of the magnets and Ni lines to obtain the optimal magnetic configuration. RESULTS: A homogeneous cell distribution on the upper surface of the sample chamber was obtained with a magnet where the pole faces were tilted towards each other. The spatial distribution of magnetically aligned objects in between the Ni lines was dependent on the ratio of the diameter of the aligned object and the line spacing, which was tested with magnetically and fluorescently labeled 6 microm polystyrene beads. The best result was obtained when the line spacing was equal to or smaller than the diameter of the aligned object. CONCLUSIONS: The magnetic gradient of the designed permanent magnet extracts magnetically labeled cells from any cell suspension to a desired plane, providing a homogeneous cell distribution. In addition, it magnetizes ferro-magnetic Ni lines in this plane whose additional local gradient adds to the gradient of the permanent magnet. The resultant gradient aligns the magnetically labeled cells first brought to this plane. This combination makes it possible, in a single step, to extract and align cells on a surface from any cell suspension.
INTRODUCTION: The magnetic navigation system consists of an externally generated magnetic field that is used to control and steer a magnetically tipped microguidewire. The goal of this study was to demonstrate that the use of the magnetic navigation system and its magnetic microguidewire is feasible and safe in all types of neuroendovascular procedures. METHODS: A magnetic navigation system is an interventional workstation that combines a biplanar fluoroscopy system with a computer-controlled magnetic field generator to provide both visualization and control of a magnetically activated endovascular microguidewire. Ten consecutive patients underwent a variety of neuroendovascular procedures using the magnetic guidance system and magnetic microguidewire. All patients presented with a neurovascular disease that was suitable for endovascular treatment. Multiple different devices and embolic agents were used. RESULTS: Of the ten patients, three were male and seven female. Their mean age was 53.9 years. The predominant neurovascular condition was the presence of intracranial aneurysm (nine patients). One patient had a left mandibular arteriovenous malformation. All treatments were successfully performed on the magnetic navigation system suite. The magnetic navigation system and the magnetic microguidewire allowed safe and accurate endovascular navigation allowing placement of the microcatheters in the desired location. There were no neurological complications or death in our series. CONCLUSION: The use of the magnetic navigation system and the magnetic microguidewire in the endovascular treatment of patients with neurovascular diseases is feasible and safe.
In this study, we used lung and liver tissue specimens distracted from tissue to investigate remanant magnetization, and found that specimens with a volume of 6 mm3 had an intensity of 10(-10) Am2, which was significantly stronger than the noise level of the superconducting magnetometer. This finding indicates that both lung and liver tissues contain magnetic materials. We speculated that biological magnetite is the magnetic material in these tissues. In addition, we found that lung tissue specimens with strong magnetization had correspondingly strong magnetized findings in the liver tissue specimens. In a comparison of magnetization in lung cancer tissue specimens and normal lung tissue, no significant relationship was noted, but two of the lung cancer tissue specimens showed strong magnetization. The number of lung cancer specimens studies was insufficient to investigate the relation between the magnetization (accumulation of magnetic materials) and lung cancer, and further studies are necessary. The magnetic properties of two lung cancer tissue specimens showing strong magnetization were further investigated, and an alternating field demagnetization experiment showed that their magnetization was composed of a unit stable vector, which indicates that the lung tissue may have been magnetized after the accumulation of magnetic materials. The Wohlfarth ratio (Moskowitz et al., 1989) of them was less than 0.5, which suggests that magnetic materials are distributed in clusters in lung tissue.
The National Center for Complementary and Alternative Medicine of the National Institutes of Health has published a detailed set of questions and answers about using magnets to treat pain. This resource cites the relevant scientific literature and addresses the following questions. What are magnets? Is the use of magnets considered conventional medicine or complementary and alternative medicine? What is the history of the discovery and use of magnets to treat pain? How common is the use of magnets to treat pain? What are some examples of theories and beliefs about magnets and pain? How are static magnets used in attempts to treat pain? How are electromagnets used in attempts to treat pain? What is known from the scientific evidence about the effectiveness of magnets in treating pain? Are there scientific controversies associated with using magnets for pain? Have any side effects or complications occurred from using magnets for pain? What should consumers know if they are considering using magnets to treat pain? Is the National Center for Complementary and Alternative Medicine (NCCAM) funding research on magnets for pain and other diseases and conditions? The report also includes definitions and three appendices that address the following issues: Research on Theories and Beliefs On How Magnets Might Relieve Pain, General and Systematic Reviews on CAM Magnetic Therapy for Pain Published From August 1999 to August 2003, and Reports on Randomized Clinical Trials of Magnetic Therapy for Pain from January 1997 to March 2004.
Bonded neodymium-iron-boron (NdFeB) permanent magnets in a paired configuration were successfully used to control mass transport in redox-based, magnetohydrodynamics (MHD). Control of fluid flow based on magnetic fields has potential for use in portable lab-on-a-chip (LOAC) and analytical devices. Bonded magnets, composed of magnetic powder and organic binder materials, are less expensive and easier to fabricate and pattern than electromagnets and sintered permanent magnets, which have been previously used in MHD studies on electrochemical systems. The ability to pattern bonded magnets near and around the electrodes is expected to allow for better control over the magnetic field distribution and solution flow. Current was generated at an 800-microm-radius platinum disk electrode in a solution of 0.06 M nitrobenzene and 0.5 M tetra-n-butylammonium hexafluorophosphate in acetonitrile. Increases in limiting current in the presence of the magnetic field, which indicate enhancement in mass transport, for sintered (210+/-14%, N = 4, where B(r) = 1.23 T and magnetic field strength is 0.55 T) and bonded (94+/-8%, N = 4, where B(r) = 0.41 T and magnetic field strength is 0.20 T) magnets, were similar to those obtained using an electromagnet with the same magnetic flux densities. The magnetic field strength and not the magnet type is important in controlling fluid flow, which is encouraging for integration of bonded permanent magnets into LOAC devices.
OBJECTIVE: Using functional magnetic resonance imaging, we assessed variation in location and intensity of blood oxygen level-dependent contrast associated with movements induced by transcranial magnetic stimulation or volition. BACKGROUND: Anatomic location and within-subject repeatability of blood oxygen level-dependent responses induced by transcranial magnetic stimulation comprise critical information to the use of interleaved transcranial magnetic stimulation/functional magnetic resonance imaging as a neuroscience tool. METHODS: Eleven healthy adults were scanned 3 times each at 1.5 T. Interleaved with functional magnetic resonance imaging, 1-Hz transcranial magnetic stimulation was applied over motor cortex. VOL was alternated with transcranial magnetic stimulation over the scans. RESULTS: Intra-subject standard deviations in blood oxygen level-dependent locations ranged between 3 and 6 millimeters, allowing localization to subregions of the motor strip. Coil placement relative to blood oxygen level-dependent location varied more than blood oxygen level-dependent location (sdx = 9.5mm, sdy = 8.7 mm, sdz = 9.0mm) with consistent anterior displacement (dy = 21.8 mm, P = <0.025). Analysis of variance did not detect significant differences between transcranial magnetic stimulation and VOL blood oxygen level-dependent locations or intensities, in contrast to significant intensity differences detected in auditory blood oxygen level dependence. CONCLUSION: The high repeatability of location of transcranial magnetic stimulation-induced blood oxygen level-dependent activation suggests that transcranial magnetic stimulation/functional magnetic resonance imaging stimulation can be used as a precise tool in investigation of cortical mechanisms. The similarity between VOL and transcranial magnetic stimulation suggests that transcranial magnetic stimulation may act through natural brain movement circuits.