-
Pacing and Clinical Electrophysiology :... Feb 2023The manufacturer of subcutaneous implantable cardioverter defibrillators (S-ICDs) acknowledges that 'deep implants' may fail to elicit a magnet response, however, does...
INTRODUCTION
The manufacturer of subcutaneous implantable cardioverter defibrillators (S-ICDs) acknowledges that 'deep implants' may fail to elicit a magnet response, however, does not define 'deep implant' or recommend a maximum implant depth. This study aims to systematically evaluate the effect of subcutaneous tissue depth and magnet types on evoked magnet response.
METHODS
Sunshine Coast University Hospital's S-ICD cohort underwent magnet response evaluation; where bar and donut magnets were compared and the evoked magnet response was recorded in three separate zones, guided by a template. Ordinal regression (OR) models assessed the relationship between the evoked magnet response and tissue depth (TD), measured via post-implant X-Ray. The patient's ability to hear the magnet response audible tone was recorded.
RESULTS
Patients (n = 39) with measurable TD (n = 30) were analyzed. The bar magnet evoked a magnet response in all zones in 53% of patients, compared with 73% of patients with the donut magnet (p = 0.18). The relationship between bar magnet response and TD showed the odds of an evoked magnet response decreased by 11% every 1 mm increase in TD (OR of 0.89, p < 0.01), whereas the donut magnet decreased by 16% per 1 mm (OR of 0.84, p < 0.01). Directly over the S-ICD was the most effective in evoking magnet response with the bar (85% of patients), and off-centre was most effective for the donut magnet (100%). BMI and Praetorian score were not significantly associated with magnet response. We found 23% of patients were unable to detect the audible tone.
CONCLUSION
We observed a statistically significant association between TD and ability to evoke magnet response. The bar magnet was less reliable than the donut magnet for therapy inhibition in deep implants.
Topics: Humans; Magnets; Subcutaneous Tissue; Electric Countershock; Defibrillators, Implantable
PubMed: 36269082
DOI: 10.1111/pace.14609 -
Otology & Neurotology : Official... Jun 2021To investigate whether ultrasound is a helpful and reliable diagnostic tool to survey the status of the magnet previous and after manual repositioning in patients with...
OBJECTIVE
To investigate whether ultrasound is a helpful and reliable diagnostic tool to survey the status of the magnet previous and after manual repositioning in patients with partially dislocated cochlear implant (CI) magnets and to assess the success rate of a manual repositioning maneuver.
DESIGN
A prospective cohort study.
SETTING
A tertiary referral medical center.
PATIENTS
Patients with a cochlear implant who presented with magnet dislocation after magnetic resonance imaging (MRI) between June 1, 2019 and July 15, 2020.
INTERVENTIONS
Manual repositioning of the partially dislocated CI magnet surveyed by pre- and post-interventional ultrasound.
MAIN OUTCOME MEASURES
Rate of successfully diagnosed and manually repositioned magnets; complication rate and recurrence rate after initial manual repositioning maneuver.
RESULTS
Nine patients presented with a partial magnet dislocation diagnosed by pre-interventional ultrasound following MRI (n = 9 magnets; three ♀; eight right-sided implants; 65.4 ± 21.7 yr). All magnets were repositioned manually. The magnets were successfully repositioned at the first attempt in six out of eight patients. Two patients required a second and one patient a third attempt of manual repositioning. Post-interventional ultrasound confirmed the entirely restored magnet position in all cases. During the mean follow-up period of 7.3 months (±5.4 mo) no patient experienced any complication or recurrent dislocation of the respective magnet.
CONCLUSION
Manual magnet repositioning is a feasible and reliable method with a high success rate for partially dislocated CI magnets. The pre-interventional diagnosis as well as the post-interventional confirmation of the magnet status can be effectively determined by ultrasound. Thus, manual magnet repositioning and ultrasound investigation can be advocated as first-line therapeutic and diagnostic instruments when dealing with partial magnet dislocation.
Topics: Cochlear Implantation; Cochlear Implants; Drug Repositioning; Humans; Magnetic Resonance Imaging; Magnets; Prospective Studies
PubMed: 33534388
DOI: 10.1097/MAO.0000000000003019 -
Expert Review of Medical Devices 2015A widely accepted definition of a medical device is an instrument or apparatus that is used to diagnose, prevent or treat disease. Medical devices take a broad range of... (Review)
Review
A widely accepted definition of a medical device is an instrument or apparatus that is used to diagnose, prevent or treat disease. Medical devices take a broad range of forms and utilize various methods to operate, such as physical, mechanical or thermal. Of particular interest in this paper are the medical devices that utilize magnetic field sources to operate. The exploitation of magnetic fields to operate or drive medical devices has become increasingly popular due to interesting characteristics of magnetic fields that are not offered by other phenomena, such as mechanical contact, hydrodynamics and thermodynamics. Today, there is a wide range of magnetically driven medical devices purposed for different anatomical regions of the body. A review of these devices is presented and organized into two groups: permanent magnetically driven devices and electromagnetically driven devices. Within each category, the discussion will be further segregated into anatomical regions (e.g., gastrointestinal, ocular, abdominal, thoracic, etc.).
Topics: Electromagnetic Fields; Humans; Magnetic Fields; Magnetics
PubMed: 26295303
DOI: 10.1586/17434440.2015.1080120 -
Nature Communications Jun 2023Control of magnetization and electric polarization is attractive in relation to tailoring materials for data storage and devices such as sensors or antennae. In...
Control of magnetization and electric polarization is attractive in relation to tailoring materials for data storage and devices such as sensors or antennae. In magnetoelectric materials, these degrees of freedom are closely coupled, allowing polarization to be controlled by a magnetic field, and magnetization by an electric field, but the magnitude of the effect remains a challenge in the case of single-phase magnetoelectrics for applications. We demonstrate that the magnetoelectric properties of the mixed-anisotropy antiferromagnet LiNiFePO are profoundly affected by partial substitution of Ni ions with Fe on the transition metal site. This introduces random site-dependent single-ion anisotropy energies and causes a lowering of the magnetic symmetry of the system. In turn, magnetoelectric couplings that are symmetry-forbidden in the parent compounds, LiNiPO and LiFePO, are unlocked and the dominant coupling is enhanced by almost two orders of magnitude. Our results demonstrate the potential of mixed-anisotropy magnets for tuning magnetoelectric properties.
Topics: Anisotropy; Electricity; Magnetic Fields; Magnets
PubMed: 37296135
DOI: 10.1038/s41467-023-39128-7 -
Molecules (Basel, Switzerland) Feb 2021The effective spin Hamiltonian method has drawn considerable attention for its power to explain and predict magnetic properties in various intriguing materials. In this... (Review)
Review
The effective spin Hamiltonian method has drawn considerable attention for its power to explain and predict magnetic properties in various intriguing materials. In this review, we summarize different types of interactions between spins (hereafter, spin interactions, for short) that may be used in effective spin Hamiltonians as well as the various methods of computing the interaction parameters. A detailed discussion about the merits and possible pitfalls of each technique of computing interaction parameters is provided.
Topics: Magnetic Phenomena; Magnets; Models, Theoretical
PubMed: 33557181
DOI: 10.3390/molecules26040803 -
Topics in Current Chemistry (Cham) Jun 2019Manganese(III) porphyrin complexes with various metal-containing/non-metal bridges reported during the past two decades, including their structural characteristics and... (Review)
Review
Manganese(III) porphyrin complexes with various metal-containing/non-metal bridges reported during the past two decades, including their structural characteristics and magnetic properties, are summarized. As the porphyrin ligands usually adopt a planar chelate form, it is possible that the porphyrin-based complexes, being a coordination-acceptor building block, have two coordination labile sites in trans positions. In particular, the coordination labile sites in an octahedral field face the direction of the Jahn-Teller elongated axis occupying the d orbital. As a result of this characteristic orbital arrangement, the activity and magnetic-electronic properties of the manganese complexes can be tuned by modulating the porphyrin ligand, which is equatorially located around the manganese ion and coupled with the d orbital. The high-spin Mn(III) porphyrin complexes (S = 2) display strong magnetic uniaxial anisotropy with the Jahn-Teller axis as the magnetic easy axis. So far, various manganese(III) porphyrin magnetism systems, including multinuclear clusters, one-dimensional chains, and two- or three-dimensional networks, have been designed and structurally and magnetically characterized. This review shows that the manganese(III) porphyrin complexes have potential as versatile sources for the design of unique magnetic materials as well as other molecular functional materials with various structures.
Topics: Coordination Complexes; Crystallography, X-Ray; Cyanides; Dimerization; Magnetics; Magnets; Metalloporphyrins; Models, Molecular
PubMed: 31161309
DOI: 10.1007/s41061-019-0244-5 -
Nature Methods May 2015
Topics: Animals; Magnetic Resonance Spectroscopy; Magnets; Molecular Probes; Nanostructures
PubMed: 26120630
DOI: 10.1038/nmeth.3388 -
Journal of Magnetic Resonance (San... Oct 2021Early detection of fatty-liver disease is important before further aggravations of the disease, such as cirrhosis, can develop. In this study, we developed a low-cost,...
Early detection of fatty-liver disease is important before further aggravations of the disease, such as cirrhosis, can develop. In this study, we developed a low-cost, movable single-sided magnet for in vivo liver fat quantification. A gradient field of 73.5 G/cm and a field strength of 0.0725 T were obtained by structurally optimizing the concave U-shaped magnet, on which the region of interest (ROI) was a curved shape about 0.4 mm thick, 8 cm above the surface of the radiofrequency (RF) coil. We constructed a prototype nuclear magnetic-resonance (NMR) relaxometry system based on this optimized magnet. Subsequent phantom experiments demonstrated the effectiveness of the single-sided magnet in evaluating different proton density fat fraction (PDFF) phantoms. As expected, the results of the six phantoms showed good positive correlation between PDFF and the fitted fat amplitude, which suggested that single-sided NMR relaxometry could be used to quantify liver fat in vivo.
Topics: Adipose Tissue; Liver; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Magnets; Phantoms, Imaging
PubMed: 34428727
DOI: 10.1016/j.jmr.2021.107053 -
Journal of Visualized Experiments : JoVE Feb 2022Mechanobiology describes how the physical forces and mechanical properties of biological material contribute to physiology and disease. Typically, these approaches are...
Mechanobiology describes how the physical forces and mechanical properties of biological material contribute to physiology and disease. Typically, these approaches are limited single-molecule methods, which restricts their availability. To address this need, a microplate assay was developed that enables mechanical manipulation while performing standard biochemical assays. This is achieved using magnets incorporated into a microplate lid to create multiple magnetic tweezers. In this format, force is exerted across biomolecules connected to paramagnetic beads, equivalent to a typical magnetic tweezer. The study demonstrates the application of this tool with FRET-based assays to monitor protein conformations. However, this approach is widely applicable to different biological systems ranging from measuring enzymatic activity through to the activation of signaling pathways in live cells.
Topics: Biophysics; Magnetic Phenomena; Magnetics; Magnets; Nanotechnology; Optical Tweezers
PubMed: 35225277
DOI: 10.3791/62994 -
Clinical Radiology Dec 2019The number of patients with cochlear implants (CIs) is increasing due to expanding indications, and improving CI services. Furthermore, as the use of imaging increases... (Review)
Review
The number of patients with cochlear implants (CIs) is increasing due to expanding indications, and improving CI services. Furthermore, as the use of imaging increases in clinical medicine, it is increasingly likely that patients with CIs will require a magnetic resonance imaging (MRI) examination during their lifetime. Therefore it is important that clinicians are aware of the safety aspects and manufacturer recommendations for CI patients with retained magnets. This article summarises guidelines from all major CI manufacturers and reviews the published literature on the safety of MRI in CI patients with magnets in situ. The most commonly reported complication of MRI in CI patients was pain. Other significant complications included magnet displacement, depolarisation, and polarity reversal. Artefacts caused by the CI remain an issue, but may be reduced by the use of specific sequences. Manufacturer recommendations should be followed to reduce the risk of complications, although complications may occur even when guidelines are followed. For this reason, the indication for imaging these patients should be reviewed, and patients should be appropriately counselled and consented.
Topics: Cochlear Implants; Humans; Magnetic Resonance Imaging; Magnets; Neuroimaging
PubMed: 31324337
DOI: 10.1016/j.crad.2019.06.011