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1.
Abdom Radiol (NY) ; 2024 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-38831074

RESUMO

Devices for the gastrointestinal tract are widely available and constantly advancing with less invasive techniques. They play a crucial role in diagnostic and therapeutic interventions and are commonly placed by interventional radiologists, gastroenterologists, and surgeons. These devices frequently appear in imaging studies, which verify their proper placement, identify any complications, or may be incidentally detected. Radiologists must be able to identify these devices at imaging and understand their intended purpose to assess their efficacy, detect complications such as incorrect positioning, and avoid misinterpreting them as abnormalities. Furthermore, many patients with these devices may require MRI, making assessing compatibility essential for safe patient care. This review seeks to provide a succinct and practical handbook for radiologists regarding both common and uncommon gastrointestinal devices. In addition to textual descriptions of clinical indications, imaging findings, complications, and MRI compatibility, the review incorporates a summary table as a quick reference point for key information and illustrative images for each device.

2.
Magn Reson Med ; 2024 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-38767407

RESUMO

PURPOSE: Peripheral nerve stimulation (PNS) limits the usability of state-of-the-art whole-body and head-only MRI gradient coils. We used detailed electromagnetic and neurodynamic modeling to set an explicit PNS constraint during the design of a whole-body gradient coil and constructed it to compare the predicted and experimentally measured PNS thresholds to those of a matched design without PNS constraints. METHODS: We designed, constructed, and tested two actively shielded whole-body Y-axis gradient coil winding patterns: YG1 is a conventional symmetric design without PNS-optimization, whereas YG2's design used an additional constraint on the allowable PNS threshold in the head-imaging landmark, yielding an asymmetric winding pattern. We measured PNS thresholds in 18 healthy subjects at five landmark positions (head, cardiac, abdominal, pelvic, and knee). RESULTS: The PNS-optimized design YG2 achieved 46% higher average experimental thresholds for a head-imaging landmark than YG1 while incurring a 15% inductance penalty. For cardiac, pelvic, and knee imaging landmarks, the PNS thresholds increased between +22% and +35%. For abdominal imaging, PNS thresholds did not change significantly between YG1 and YG2 (-3.6%). The agreement between predicted and experimental PNS thresholds was within 11.4% normalized root mean square error for both coils and all landmarks. The PNS model also produced plausible predictions of the stimulation sites when compared to the sites of perception reported by the subjects. CONCLUSION: The PNS-optimization improved the PNS thresholds for the target scan landmark as well as most other studied landmarks, potentially yielding a significant improvement in image encoding performance that can be safely used in humans.

3.
Magn Reson Med ; 92(3): 1290-1305, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-38624032

RESUMO

PURPOSE: To demonstrate the performance of gradient array coils in minimizing switched-gradient-induced electric fields (E-fields) and improving peripheral nerve stimulation (PNS) thresholds while generating gradient fields with adjustable linearity across customizable regions of linearity (ROLs). METHODS: A body gradient array coil is used to reduce the induced E-fields on the surface of a body model by modulating applied currents. This is achieved by performing an optimization problem with the peak E-field as the objective function and current amplitudes as unknown variables. Coil dimensions and winding patterns are fixed throughout the optimization, whereas other engineering metrics remain adjustable. Various scenarios are explored by manipulating adjustable parameters. RESULTS: The array design consistently yields lower E-fields and higher PNS thresholds across all scenarios compared with a conventional coil. When the gradient array coil generates target gradient fields within a 44-cm-diameter spherical ROL, the maximum E-field is reduced by 10%, 18%, and 61% for the X, Y, and Z gradients, respectively. Transitioning to a smaller ROL (24 cm) and relaxing the gradient linearity error results in further E-field reductions. In oblique gradients, the array coil demonstrates the most substantial reduction of 40% in the Z-Y direction. Among the investigated scenarios, the most significant increase of 4.3-fold is observed in the PNS thresholds. CONCLUSION: Our study demonstrated that gradient array coils offer a promising pathway toward achieving high-performance gradient coils regarding gradient strength, slew rate, and PNS thresholds, especially in scenarios in which linear magnetic fields are required within specific target regions.


Assuntos
Desenho de Equipamento , Nervos Periféricos , Nervos Periféricos/fisiologia , Humanos , Campos Eletromagnéticos , Imageamento por Ressonância Magnética/instrumentação , Estimulação Elétrica/instrumentação
4.
Radiography (Lond) ; 30(3): 889-895, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38603992

RESUMO

INTRODUCTION: Acoustic noise from magnetic resonance imaging (MRI) can cause hearing loss and needs to be mitigated to ensure the safety of patients and personnel. Capturing MR personnel's insights is crucial for guiding the development and future applications of noise-reduction technology. This study aimed to explore how MR radiographers manage acoustic noise in clinical MR settings. METHODS: Using a qualitative design, we conducted semi-structured individual interviews with fifteen MR radiographers from fifteen hospitals around Sweden. We focused on the clinical implications of participants' noise management, using an interpretive description approach. We also identified sociotechnical interactions between People, Environment, Tools, and Tasks (PETT) by adopting a Human Factors/Ergonomics framework. Interview data were analyzed inductively with thematic analysis (Braun and Clarke). RESULTS: The analysis generated three main themes regarding MR radiographers' noise management: (I) Navigating Occupational Noise: Risk Management and Adaptation; (II) Protecting the Patient and Serving the Exam, and (III) Establishing a Safe Healthcare Environment with Organizational Support. CONCLUSION: This study offers insights into radiographers' experiences of managing acoustic noise within MRI, and the associated challenges. Radiographers have adopted multiple strategies to protect patients and themselves from adverse noise-related effects. However, they require tools and support to manage this effectively, suggesting a need for organizations to adopt more proactive, holistic approaches to safety initiatives. IMPLICATIONS FOR PRACTICE: The radiographers stressed the importance of a soundproofed work environment to minimize occupational adverse health effects and preserve work performance. They acknowledge noise as a common contributor to patient distress and discomfort. Providing options like earplugs, headphones, mold putty, software-optimized "quiet" sequences, and patient information were important tools. Fostering a safety culture requires proactive safety efforts and support from colleagues and management.


Assuntos
Entrevistas como Assunto , Imageamento por Ressonância Magnética , Ruído Ocupacional , Pesquisa Qualitativa , Humanos , Suécia , Feminino , Masculino , Adulto , Pessoa de Meia-Idade , Perda Auditiva Provocada por Ruído/prevenção & controle , Exposição Ocupacional/prevenção & controle , Gestão de Riscos
5.
Radiography (Lond) ; 30(3): 843-855, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38579383

RESUMO

INTRODUCTION: Strict safety practices are essential to ensure the safety of patients and staff in Magnetic Resonance Imaging (MRI). Training regarding the fundamentals of MRI safety is well-established and commonly agreed upon. However, more complex aspect of screening patients, such as image review or screening of unconscious patients/patients with communication difficulties is less well discussed. The current UK and USA guidelines do not suggest the use of communication training for MRI staff nor indicate any training to encourage reviewing images in the screening process. This review aims to map the current guidance regarding safety and patient screening training for MRI diagnostic and therapeutic radiographers. METHODS: A systematic search of PubMed, Trip Medical database and Radiography journal was conducted. Studies were chosen based on the review objectives and pre-determined inclusion/exclusion criteria using the PRISMA-ScR framework. RESULTS: Twenty-four studies were included in the review, which identified some key concepts including MRI safety training and delivery methods, screening and communication, screening of unconscious or non-ambulatory patients and the use of imaging. CONCLUSION: Training gaps lie within the more complex elements of screening such as the inclusiveness of question phrasing, particularly to the neurodivergent population, how we teach radiographers to screen unconscious/unresponsive patients and using imaging to detect implants. IMPLICATIONS FOR PRACTICE: The consequences of incomplete or inaccurate pre-MRI safety screening could be the introduction of unexpected implants into the scanner or forgoing MRI for a less desirable modality. The development of enhanced training programs in implant recognition using imaging and communication could complement existing training.


Assuntos
Imageamento por Ressonância Magnética , Humanos , Segurança do Paciente , Pessoal Técnico de Saúde/educação , Encaminhamento e Consulta
6.
J Cardiovasc Magn Reson ; 26(1): 100006, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38215698

RESUMO

This position statement guides cardiovascular magnetic resonance (CMR) imaging program directors and learners on the key competencies required for Level II and III CMR practitioners, whether trainees come from a radiology or cardiology background. This document is built upon existing curricula and was created and vetted by an international panel of cardiologists and radiologists on behalf of the Society for Cardiovascular Magnetic Resonance (SCMR).


Assuntos
Cardiologia , Competência Clínica , Consenso , Currículo , Educação de Pós-Graduação em Medicina , Imageamento por Ressonância Magnética , Humanos , Educação de Pós-Graduação em Medicina/normas , Imageamento por Ressonância Magnética/normas , Cardiologia/educação , Cardiologia/normas , Doenças Cardiovasculares/diagnóstico por imagem , Cardiologistas/educação , Cardiologistas/normas , Valor Preditivo dos Testes , Radiologistas/educação , Radiologistas/normas , Radiologia/educação , Radiologia/normas , Sociedades Médicas/normas
7.
Radiography (Lond) ; 30(1): 168-175, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38035429

RESUMO

INTRODUCTION: Plain film radiographs are recommended to assist in MRI safety screening of patients with unknown medical histories, especially in an emergency setting where patients might be unable to answer a safety questionnaire. This study assesses the performance of CT scout images, which have low radiation dose and are faster and easier to acquire compared to plain film radiographs, in finding and naming a range of head and body implants. METHODS: A retrospective analysis of 40 CT Head and Neck (HN) scout images and 40 CT Chest, Abdomen and Pelvis (CAP) scout images was undertaken. A subset of these were chosen to include a range of common internal implants not identifiable externally to the patient. The images were assessed by three readers with varying levels of clinical experience in MRI who were asked to find and name any implants seen. RESULTS: Collectively, all readers reached a sensitivity of 85 % in finding internal implants, regardless of their clinical experience or experience in reviewing CT images, and a minimum specificity of 95 %. Implants were correctly named in 74 % of the images presented. CONCLUSION: CT scout images were able to reveal most of the implants included. However, clinical experience in reviewing the images enhances a reader's ability to identify the type of implant. IMPLICATIONS FOR PRACTICE: In an emergency setting, imaging can be critical in the management of patients presenting with acute illnesses. In the unconscious or unresponsive patient, the use of CT scouts, where this is the only option available, could provide valuable MRI safety information prior to a scan, improving access to the MRI scan in a timely manner.


Assuntos
Pelve , Tomografia Computadorizada por Raios X , Humanos , Estudos Retrospectivos , Tomografia Computadorizada por Raios X/efeitos adversos , Tomografia Computadorizada por Raios X/métodos , Imageamento por Ressonância Magnética
8.
Laryngoscope ; 134(1): 393-396, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37289065

RESUMO

OBJECTIVE: There is increased confusion regarding MRI-compatible CIs and BAHAs. This report describes two cases when patients underwent MRIs with non-MRI compatible devices. RESULTS: One patient with bilateral Cochlear Osias experienced dislocation of both internal magnets after 1.5 Tesla MRI. Both magnets were outside the silastic sheath, with the left magnet flipped. A second patient with a legacy CI experienced similar internal magnet dislocation and inversion after 3 Tesla MRI. CONCLUSIONS: This study describes internal magnet dislocation/inversion with the Cochlear Osia and a legacy CI after MRI. Our findings suggest the need for improved patient education and simplified radiology guidelines. Laryngoscope, 134:393-396, 2024.


Assuntos
Implante Coclear , Implantes Cocleares , Humanos , Implante Coclear/efeitos adversos , Imageamento por Ressonância Magnética/métodos , Imãs , Tecnologia
9.
J Magn Reson Imaging ; 59(5): 1514-1522, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-37767980

RESUMO

The standard of care for managing a patient with an implant is to identify the item and to assess the relative safety of scanning the patient. Because the 1.5 T MR system is the most prevalent scanner in the world and 3 T is the highest field strength in widespread use, implants typically have "MR Conditional" (i.e., an item with demonstrated safety in the MR environment within defined conditions) labeling at 1.5 and/or 3 T only. This presents challenges for a facility that has a scanner operating at a field strength below 1.5 T when encountering a patient with an implant, because scanning the patient is considered "off-label." In this case, the supervising physician is responsible for deciding whether to scan the patient based on the risks associated with the implant and the benefit of magnetic resonance imaging (MRI). For a passive implant, the MRI safety-related concerns are static magnetic field interactions (i.e., force and torque) and radiofrequency (RF) field-induced heating. The worldwide utilization of scanners operating below 1.5 T combined with the increasing incidence of patients with implants that need MRI creates circumstances that include patients potentially being subjected to unsafe imaging conditions or being denied access to MRI because physicians often lack the knowledge to perform an assessment of risk vs. benefit. Thus, physicians must have a complete understanding of the MRI-related safety issues that impact passive implants when managing patients with these products on scanners operating below 1.5 T. This monograph provides an overview of the various clinical MR systems operating below 1.5 T and discusses the MRI-related factors that influence safety for passive implants. Suggestions are provided for the management of patients with passive implants labeled MR Conditional at 1.5 and/or 3 T, referred to scanners operating below 1.5 T. The purpose of this information is to empower supervising physicians with the essential knowledge to perform MRI exams confidently and safely in patients with passive implants. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 3.


Assuntos
Campos Magnéticos , Próteses e Implantes , Humanos , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas
10.
SA J Radiol ; 27(1): 2701, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38059118

RESUMO

Background: An MRI is potentially hazardous for patients with retained ferromagnetic bullets. Recent studies have aimed to develop dual-energy computed tomography (DECT) as a screening tool for recognising highly ferromagnetic bullets. Inconsistent findings have been ascribed to inherent CT technology differences. Previous research demonstrated significant Hounsfield unit (HU) measurement variation among single-source CT machines. Objectives: This study investigated the theoretical dual-energy index (DEI) variation between DECT machines when evaluating the potential ferromagnetic properties within the same sample of ex vivo bullets and metal phantoms. Method: An experimental ex vivo study was conducted on eight metal phantoms and 10 unused bullets individually positioned in the same Perspex head phantom and scanned on two DECT machines. Two senior radiology registrars independently recorded the HU readings, and DEI values were calculated. Statistical analysis was performed using non-parametric methods for paired data, namely the Signed Rank Test. The DEI values based on mean HU readings between the DECT machines were compared. Results: Inter- and intra-reader agreement was not statistically significant. The metal phantoms had poor interscanner agreement, with an overlap of the ferromagnetic and non-ferromagnetic ranges. The bullets had good interscanner agreement, with a similar ferromagnetic to non-ferromagnetic relationship. Conclusion: The use of DEI values negates the previous assumption that significant interscanner variability exists among different DECT technologies while assessing highly attenuative ex vivo bullets. Contribution: This investigation demonstrated that even though HU readings may be variable, the implementation of the DEI equation translates this into comparable values with good interscanner agreement.

11.
Case Rep Dermatol ; 15(1): 85-92, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37928338

RESUMO

Adverse reactions in tattooed skin during magnetic resonance imaging (MRI) are rare but well known. Previous reports describe sudden burning pain in tattooed skin, sometimes accompanied by mild erythema and oedema when entering MRI scanners. The pathophysiology remains unclear, but simple direct thermal heating can be excluded. It has been hypothesized that MRI-triggered torque and traction create neural sensations from magnetic pigment particles. However, this case enlightens yet another possible mechanism. We present a 35-year-old woman experiencing reoccurring stinging sensations in three decorative black tattoos just seconds after the initiation of the MRI. Single-blind tests with handheld power magnets or a dummy could reproduce painful subjective feelings in her tattooed skin. Similar events were provoked during re-evaluation with MRI. Surprisingly, chemical analyses and electron microscopy of skin samples revealed carbon black as the colouring agent - no iron-based solids were detected. Our case demonstrates that MRI tattoo reactions are not limited to magnetic contaminants alone. More distinct subgroups of MRI-induced reactions may occur. We hypothesize that radiofrequency induction of surface currents in black carbon particles adjacent to sensory axons in the dermis may lead to neurosensations.

12.
Biomed Phys Eng Express ; 9(6)2023 10 26.
Artigo em Inglês | MEDLINE | ID: mdl-37844574

RESUMO

Purpose. The goal of this study was to develop and validate a computational model that can accurately predict the influence of flow on the temperature rise near a peripheral vascular stent during magnetic resonance imaging (MRI).Methods. Computational modeling and simulation of radio frequency (RF) induced heating of a vascular stent during MRI at 3.0 T was developed and validated with flow phantom experiments. The maximum temperature rise of the stent was measured as a function of physiologically relevant flow rates.Results. A significant difference was not identified between the experiment and simulation (P > 0.05). The temperature rise of the stent during MRI was over 10 °C without flow, and was reduced by 5 °C with a flow rate of only 58 ml min-1, corresponding to a reduction of CEM43from 45 min to less than 1 min.Conclusion. The computer model developed in this study was validated with experimental measurements, and accurately predicted the influence of flow on the RF-induced temperature rise of a vascular stent during MRI. Furthermore, the results of this study demonstrate that relatively low flow rates significantly reduce the temperature rise of a stent and the surrounding medium during RF-induced heating under typical scanning power and physiologically relevant conditions.


Assuntos
Calefação , Temperatura Alta , Imageamento por Ressonância Magnética/métodos , Simulação por Computador , Stents
13.
NMR Biomed ; 36(12): e5022, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37574441

RESUMO

Since the introduction of MRI as a sustainable diagnostic modality, global accessibility to its services has revealed a wide discrepancy between populations-leaving most of the population in LMICs without access to this important imaging modality. Several factors lead to the scarcity of MRI in LMICs; for example, inadequate infrastructure and the absence of a dedicated workforce are key factors in the scarcity observed. RAD-AID has contributed to the advancement of radiology globally by collaborating with our partners to make radiology more accessible for medically underserved communities. However, progress is slow and further investment is needed to ensure improved global access to MRI.


Assuntos
Países em Desenvolvimento , Imageamento por Ressonância Magnética
14.
Med Phys ; 50(9): 5913-5919, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37469178

RESUMO

BACKGROUND: Parallel radiofrequency transmission (pTx) remains a promising technology for addressing high-field magnetic resonance imaging (MRI) challenges, particularly regarding the safety of patients with implanted deep brain stimulation (DBS) devices. Radiofrequency (RF) shim optimization methods utilizing pTx technology have shown the potential to minimize induced RF heating effects at the electrode tips of DBS devices at 3 T. PURPOSE: Research pTx system implementations often involve the combination of custom and commercial hardware that are integrated onto an existing MRI system. As a result, system characterization is important to ensure implant-friendly safe imaging conditions are satisfied for the operating range of the hardware. METHODS: Utilizing electromagnetic and thermal simulations, the impact of system uncertainty is studied for the proposed 4- and 8-channel pTx system setup and its associated "safe mode" for DBS applications. RESULTS: Electromagnetic simulations indicated that instrumentation errors can affect the overall electric field strength experienced at the DBS lead tip, and a worst-case system uncertainty analysis predicted temperature elevations of +1.5°C in the 4-channel setup and +0.9°C in the 8-channel setup. CONCLUSIONS: In conclusion, system uncertainty can impact the precision of pTx RF inputs which in the worst-case, may lead to an unsafe imaging scenario and the proposed 8-channel setup may provide more robustness and thus, safer conditions for MRI of DBS patients.


Assuntos
Estimulação Encefálica Profunda , Humanos , Estimulação Encefálica Profunda/métodos , Incerteza , Imageamento por Ressonância Magnética , Próteses e Implantes , Imagens de Fantasmas , Ondas de Rádio
15.
Magn Reson Med ; 90(6): 2524-2538, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37466040

RESUMO

PURPOSE: To predict subject-specific local specific absorption rate (SAR) distributions of the human head for parallel transmission (pTx) systems at 7 T. THEORY AND METHODS: Electromagnetic energy deposition in tissues is nonuniform at 7 T, and interference patterns due to individual channels of pTx systems may result in increased local SAR values, which can only be estimated with very high safety margins. We proposed, designed, and demonstrated a multichannel 3D convolutional neural network (CNN) architecture to predict local SAR maps as well as peak-spatial SAR (ps-SAR) levels. We hypothesized that utilizing a three-channel 3D CNN, in which each channel is fed by a B 1 + $$ {B}_1^{+} $$ map, a phase-reversed B 1 + $$ {B}_1^{+} $$ map, and an MR image, would improve prediction accuracies and decrease uncertainties in the predictions. We generated 10 new head-neck body models, along with 389 3D pTx MRI data having different RF shim settings, with their B1 and local SAR maps to support efforts in this field. RESULTS: The proposed three-channel 3D CNN predicted ps-SAR10g levels with an average overestimation error of 20%, which was better than the virtual observation points-based estimation error (i.e., 152% average overestimation). The proposed method decreased prediction uncertainties over 20% (i.e., 22.5%-17.7%) compared to other methods. A safety factor of 1.20 would be enough to avoid underestimations for the dataset generated in this work. CONCLUSION: Multichannel 3D CNN networks can be promising in predicting local SAR values and perform predictions within a second, making them clinically useful as an alternative to virtual observation points-based methods.


Assuntos
Aprendizado Profundo , Humanos , Simulação por Computador , Cabeça/diagnóstico por imagem , Radiação Eletromagnética , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas
16.
J Clin Med ; 12(13)2023 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-37445444

RESUMO

This study aims to assess potential complications and effects on the magnetic resonance imaging (MRI) image quality of a new MRI-conditional breast tissue expander (Motiva Flora®) in its first in-human multi-case application. Twenty-four patients with 36 expanders underwent non-contrast breast MRI with T1-weighted, T2-weighted, and diffusion-weighted imaging (DWI) sequences on a 3 T unit before breast tissue expander exchange surgery, being monitored during and after MRI for potential complications. Three board-certified breast radiologists blindly and independently reviewed image quality using a four-level scale ("poor", "sufficient", "good", and "excellent"), with inter-reader reliability being assessed with Kendall's τb. The maximum diameters of RFID-related artifacts on T1-weighted and DWI sequences were compared with the Wilcoxon signed-rank test. All 24 examinations were completed without patient-related or device-related complications. The T1-weighted and T2-weighted sequences of all the examinations had "excellent" image quality and a median 11 mm (IQR 9-12 mm) RFID artifact maximum diameter, significantly lower (p < 0.001) than on the DWI images (median 32.5 mm, IQR 28.5-34.5 mm). DWI quality was rated at least "good" in 63% of the examinations, with strong inter-reader reliability (Kendall's τb 0.837, 95% CI 0.687-0.952). This first in-human study confirms the MRI-conditional profile of this new expander, which does not affect the image quality of T1-weighted and T2-weighted sequences and moderately affects DWI quality.

17.
Magn Reson Med ; 90(5): 2011-2018, 2023 11.
Artigo em Inglês | MEDLINE | ID: mdl-37382200

RESUMO

PURPOSE: To propose an efficient numerical method to predict the temperature increase of an implantable medical device induced by any linearly polarized homogeneous magnetic field, according to the ISO 10974 methodology for testing of gradient-induced device heating. THEORY AND METHODS: The concepts of device-specific power and temperature tensors are introduced to mathematically describe the electromagnetic and thermal anisotropic behavior of the device, from which the device heating for an arbitrary exposure direction can be predicted. The proposed method is compared to a brute-force approach based on simulations, and validated by applying it to four reference orthopedic implants with a commercial simulation software. RESULTS: The proposed method requires about 5 % $$ \% $$ of the time required by the brute-force approach, and 30 % $$ \% $$ of the memory occupancy. The temperature increase predicted by the proposed method over a range of incident magnetic field exposures deviated from brute-force direct simulations by less than ± $$ \pm $$ 0.3 % $$ \% $$ . CONCLUSION: The proposed method allows efficient prediction of the heating of an implantable medical device induced by any linearly polarized homogeneous magnetic field using a small fraction of the simulations required by the brute-force approach. The results can be used to predict the worst-case orientation of the gradient field, for subsequent experimental characterization according to the ISO 10974 standard.


Assuntos
Calefação , Temperatura Alta , Próteses e Implantes , Simulação por Computador , Imagens de Fantasmas , Imageamento por Ressonância Magnética/métodos , Ondas de Rádio
18.
Radiography (Lond) ; 29(4): 697-704, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-37187067

RESUMO

INTRODUCTION: The MRI technologist (radiographer) is at the frontline of MRI safety decision-making and has the primary responsibility to provide high quality, efficient and safe patient care in the MRI environment. As MRI technology advances and new safety issues emerge, this study aimed to provide a snapshot of the preparedness of MRI technologists in New Zealand (NZ) and Australia to practise confidently and safely. METHOD: An online questionnaire, administered via Qualtrics and covering a range of MRI safety topics, was distributed in 2018 via the New Zealand MR Users Group, the MRI Australia-NZ Group Facebook, and relevant professional bodies. RESULTS: A total of 312 MRI technologists attempted the questionnaire, with 246 surveys being fully completed. Of these, 61% (n = 149) were in Australia, 36% (n = 89) in NZ, and 3% (n = 8) from other countries. Findings indicated that current MRI education is preparing MRI technologists in NZ and Australia to practise safely. However, while these technologists are confident in their MRI safety decision-making, accuracy levels within some groups need addressing. CONCLUSION: To develop a consistent level of safe practice, it is proposed that a minimum level of MRI-specific education is defined and mandated to practise. Continuing professional development focussing on MRI safety must be encouraged and, if audited as part of registration, could also be mandated. Implementation of a supporting regulatory framework similar to NZ is recommended for other countries. IMPLICATIONS FOR PRACTICE: All MRI technologists are responsible for the safety of their patients and staff. Employers must support and ensure MRI-specific education has been completed. Ongoing engagement in MRI safety events provided by MRI safety experts, professional bodies and/or universities is essential to remain up-to-date.


Assuntos
Pessoal Técnico de Saúde , Imageamento por Ressonância Magnética , Humanos , Austrália , Nova Zelândia , Escolaridade , Imageamento por Ressonância Magnética/efeitos adversos
19.
Magn Reson Med ; 90(2): 784-801, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37052387

RESUMO

PURPOSE: Peripheral nerve stimulation (PNS) limits the image encoding performance of both body gradient coils and the latest generation of head gradients. We analyze a variety of head gradient design aspects using a detailed PNS model to guide the design process of a new high-performance asymmetric head gradient to raise PNS thresholds and maximize the usable image-encoding performance. METHODS: A novel three-layer coil design underwent PNS optimization involving PNS predictions of a series of candidate designs. The PNS-informed design process sought to maximize the usable parameter space of a coil with <10% nonlinearity in a 22 cm region of linearity, a relatively large inner diameter (44 cm), maximum gradient amplitude of 200 mT/m, and a high slew rate of 900 T/m/s. PNS modeling allowed identification and iterative adjustment of coil features with beneficial impact on PNS such as the number of winding layers, shoulder accommodation strategy, and level of asymmetry. PNS predictions for the final design were compared to measured thresholds in a constructed prototype. RESULTS: The final head gradient achieved up to 2-fold higher PNS thresholds than the initial design without PNS optimization and compared to existing head gradients with similar design characteristics. The inclusion of a third intermediate winding layer provided the additional degrees of freedom necessary to improve PNS thresholds without significant sacrifices to the other design metrics. CONCLUSION: Augmenting the design phase of a new high-performance head gradient coil by PNS modeling dramatically improved the usable image-encoding performance by raising PNS thresholds.


Assuntos
Imageamento por Ressonância Magnética , Nervos Periféricos , Imageamento por Ressonância Magnética/métodos , Nervos Periféricos/diagnóstico por imagem , Nervos Periféricos/fisiologia , Desenho de Equipamento
20.
Pediatr Radiol ; 53(7): 1454-1468, 2023 06.
Artigo em Inglês | MEDLINE | ID: mdl-37079039

RESUMO

MRI is the imaging modality of choice for assessing many pediatric medical conditions. Although there are several inherent potential safety risks associated with the electromagnetic fields exploited for MRI, they are effectively mitigated through strict adherence to established MRI safety practices, enabling the safe and effective use of MRI in clinical practice. The potential hazards of the MRI environment may be exacerbated by/in the presence of implanted medical devices. Awareness of the unique MRI safety and screening challenges associated with these implanted devices is critical to ensuring MRI safety for the affected patients. In this review article, we will discuss the basics of MRI physics as they relate to MRI safety in the presence of implanted medical devices, strategies for assessing children with known or suspected implanted medical devices, and the particular management of several well-established common, as well as recently developed, implanted devices encountered at our institution.


Assuntos
Imageamento por Ressonância Magnética , Próteses e Implantes , Humanos , Criança , Imageamento por Ressonância Magnética/efeitos adversos
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