Magnetic resonance imaging-guided vascular interventions

Magnetic resonance imaging (MRI), which provides superior soft-tissue imaging and no known harmful effects, has the potential as an alternative modality to guide various medical interventions. This review will focus on MR-guided endovascular interventions and present its current state and future outlook. In the first technical part, enabling technologies such as developments in fast imaging, catheter devices, and visualization techniques are examined. This is followed by a clinical survey that includes proof-of-concept procedures in animals and initial experience in human subjects. In preclinical experiments, MRI has already proven to be valuable. For example, MRI has been used to guide and track targeted cell delivery into or around myocardial infarctions, to guide atrial septal puncture, and to guide the connection of portal and systemic venous circulations. Several investigational MR-guided procedures have already been reported in patients, such as MR-guided cardiac catheterization, invasive imaging of peripheral artery atheromata, selective intraarterial MR angiography, and preliminary angioplasty and stent placement. In addition, MR-assisted transjugular intrahepatic portosystemic shunt procedures in patients have been shown in a novel hybrid double-doughnut x-ray/MRI system. Numerous additional investigational human MR-guided endovascular procedures are now underway in several medical centers around the world. There are also significant hurdles: availability of clinical-grade devices, device-related safety issues, challenges to patient monitoring, and acoustic noise during imaging. The potential of endovascular interventional MRI is great because as a single modality, it combines 3-dimensional anatomic imaging, device localization, hemodynamics, tissue composition, and function.     

Building a Magnetic Resonance Imaging Safety Culture from the Ground Up

Magnetic resonance imaging (MRI) uses a strong magnetic field to generate diagnostic images. This magnetic field has the potential to cause serious and even fatal injuries to patients undergoing scans and to personnel in the area. Ensuring awareness of MRI hazards and safety procedures through a formalized education and training program is integral in creating an MRI safety culture that protects patients and staff from harm. The aim of our project was to develop an accessible and interprofessional electronic e-module learning series to instill an MRI safety culture throughout the entire hospital. This is the first such program in Canada. A simplified e-search was conducted using key search terms “mri: safety, education, safety training.” Very few articles were found that fulfilled our needs in helping us build an MRI safety program. In concert with an e-search we reached out to similar institutions and, through informal discussions, we confirmed the lack of a formalized, transferable safety program within Canada. This led to the creation of an interprofessional working team at our institution composed of key stakeholders: educators, clinical and technical experts from radiation therapy, medical imaging, the research institute, medical radiation physics, nursing, and radiation oncology. This team collaborated on the development of three education modules tailored for specific audiences based on classification as Non-MR Personnel, Level 1 MR Personnel, or Level 2 MR Personnel as defined by the American College of Radiology guidelines. All modules were 10 to 20 minutes in length with interactive engagement activities throughout as well as a final summative evaluation to test for comprehension. Knowledge of the existence of the MRI unit is only one facet of creating an MRI safety culture. By increasing the awareness of the hazards of MRI to all personnel throughout the hospital, the risk of harm to patients and staff may be decreased.     

Nitinol in Magnetic Resonance Imaging

Surgical and interventional instruments as well as implants can cause significant magnetic resonance image (MRI) artifacts. The artifacts can be used to visualize instruments, cannulae, guide wires, catheters during interventional MRI and Nitinol devices have proven to be useful for MRI procedures. Diagnostic imaging is often compromised in the area of an implant. Complete vanishing of signals occurs in close proximity or inside implants. The paper presents a fundamental evaluation of MRI artifact of Nitinol devices such as Stents, Vena Cava Filter, heart defect closure devices, cannulae, guide wire, localizer, anastomosis device, etc. in a 1.0 Tesla magnetic field. The American Society for Testing Materials (ASTM) recommendations for selection of sequences and test setup were used but the results of this paper are not sufficient for FDA approval.     

Future of advanced guidance techniques by interventional CT and MRI

Summary

Minimally invasive techniques using endoscopes for image-guided therapy are common in the surgical field and in internal medicine. Interventional procedures in the past were performed with either fluoroscopic, sono-graphic or CT-guidance, but now MRI-guided interventional procedures are being developed. Combining these technologies will improve surgical access and reduce complications. In today's minimally invasive therapy, tomography technology (CT, EBT, MRI) can be used for precise and transparent guidance of endoscopes and surgical instruments inside the body. This will offer a safe and effective access into the body, especially in high risk areas and lead to the new field of ‘Surgical Tomography'.     

Current clinical issues for MRI scanning of pacemaker and defibrillator patients

Dramatic increases in both magnetic resonance imaging (MRI) usage and cardiac device-based therapy have resulted in an estimated 50-75% probability of a patient being indicated for an MRI over the lifetime of their device. Some recent studies have demonstrated "safe procedures" and "no adverse events" in the limited populations, clinical situations, and specific devices and lead orientations tested. While these investigations are useful to help ascertain the hazards for patients with cardiac devices, they do not demonstrate clear freedom from risk. All components of active implantable systems must be engineered during the design stage to provide safety in current and evolving MR environments. Device manufacturers need to secure regulatory approval to confirm their products' safety under multiple clinical and technical variables.     

复旦大学附属中山医院新冠肺炎防控期间核医学科PET检查防护方案(2020 v.1)

PET/CT和PET/MRI检查具有环节多、流程复杂、患者在注射微量放射性示踪剂后需要在相对封闭的环境中停留时间长等特点,工作人员与患者之间、患者与患者之间交叉感染的风险大。在新型冠状病毒肺炎(NCP)防控期间,我们建议对进行PET/CT或PET/MRI检查的患者,根据其流行病学史和临床症状,对其患有NCP潜在的风险进行评估。据此对接触具有潜在风险患者的工作人员要采取必要的防护措施,并对具有潜在风险患者接触的场所进行合理的消毒,以降低交叉感染的风险。     

Magnetic resonance imaging in patients with cardiac pacemakers: era of "MR Conditional" designs

Advances in cardiac device technology have led to the first generation of magnetic resonance imaging (MRI) conditional devices, providing more diagnostic imaging options for patients with these devices, but also new controversies. Prior studies of pacemakers in patients undergoing MRI procedures have provided groundwork for design improvements. Factors related to magnetic field interactions and transfer of electromagnetic energy led to specific design changes. Ferromagnetic content was minimized. Reed switches were modified. Leads were redesigned to reduce induced currents/heating. Circuitry filters and shielding were implemented to impede or limit the transfer of certain unwanted electromagnetic effects. Prospective multicenter clinical trials to assess the safety and efficacy of the first generation of MR conditional cardiac pacemakers demonstrated no significant alterations in pacing parameters compared to controls. There were no reported complications through the one month visit including no arrhythmias, electrical reset, inhibition of generator output, or adverse sensations. The safe implementation of these new technologies requires an understanding of the well-defined patient and MR system conditions. Although scanning a patient with an MR conditional device following the strictly defined patient and MR system conditions appears straightforward, issues related to patients with pre-existing devices remain complex. Until MR conditional devices are the routine platform for all of these devices, there will still be challenging decisions regarding imaging patients with pre-existing devices where MRI is required to diagnose and manage a potentially life threatening or serious scenario. A range of other devices including ICDs, biventricular devices, and implantable physiologic monitors as well as guidance of medical procedures using MRI technology will require further biomedical device design changes and testing. The development and implementation of cardiac MR conditional devices will continue to require the expertise and collaboration of multiple disciplines and will need to prove safety, effectiveness, and cost effectiveness in patient care.     

Main applications of hybrid PET‐MRI contrast agents: a review

In medical imaging, the continuous quest to improve diagnostic performance and optimize treatment strategies has led to the use of combined imaging modalities. Positron emission tomography (PET) and computed tomography (CT) is a hybrid imaging existing already for many years. The high spatial and contrast resolution of magnetic resonance imaging (MRI) and the high sensitivity and molecular information from PET imaging are leading to the development of this new hybrid imaging along with hybrid contrast agents. To create a hybrid contrast agent for PET‐MRI device, a PET radiotracer needs to be combined with an MRI contrast agent. The most common approach is to add a radioactive isotope to the surface of a small superparamagnetic iron oxide (SPIO) particle. The resulting agents offer a wide range of applications, such as pH variation monitoring, non‐invasive angiography and early imaging diagnosis of atherosclerosis. Oncology is the most promising field with the detection of sentinel lymph nodes and the targeting of tumor neoangiogenesis. Oncology and cardiovascular imaging are thus major areas of development for hybrid PET‐MRI imaging systems and hybrid contrast agents. The aim is to combine high spatial resolution, high sensitivity, morphological and functional information. Future prospects include the use of specific antibodies and hybrid multimodal PET‐MRI‐ultrasound‐fluorescence imaging with the potential to provide overall pre‐, intra‐ and postoperative patient care. Copyright © 2015 John Wiley & Sons, Ltd.     

部分性运动性癫痫状态临床分析

目的:分析部分性运动性癫痫状态的临床特点。方法:记录7例部分性运动性癫痫状态患者的临床表现、脑电图及影像学检查结果,给予抗癫痫治疗并随访半年。结果:7例患者中5例病因明确,发作期及发作间期脑电图表现为痫性放电或节律紊乱;随访时5例痫性发作被控制,1例发作减轻,1例猝死。结论:脑电图及MRI有助于提高部分性运动性癫痫状态的诊断,及时有效地控制本病很有必要。     

Remote control catheter navigation: options for guidance under MRI

Background

Image-guided endovascular interventions have gained increasing popularity in clinical practice, and magnetic resonance imaging (MRI) is emerging as an attractive alternative to X-ray fluoroscopy for guiding such interventions. Steering catheters by remote control under MRI guidance offers unique challenges and opportunities.

Methods

In this review, the benefits and limitations of MRI-guided remote control intervention are addressed, and the tools for guiding such interventions in the magnetic environment are summarized. Designs for remote control catheter guidance include a catheter tip electromagnetic microcoil design, a ferromagnetic sphere-tipped catheter design, smart material-actuated catheters, and hydraulically actuated catheters. Remote control catheter guidance systems were compared and contrasted with respect to visualization, safety, and performance. Performance is characterized by bending angles achievable by the catheter, time to achieve bending, degree of rotation achievable, and miniaturization capacity of the design. Necessary improvements for furthering catheter design, especially for use in the MRI environment, are addressed, as are hurdles that must be overcome in order to make MRI guided endovascular procedures more accessible for regular use in clinical practice.

Conclusions

MR-guided endovascular interventions under remote control steering are in their infancy due to issues regarding safety and reliability. Additional experimental studies are needed prior to their use in humans.     

Intraoperative and interventional MRI: Recommendations for a safe environment

In this paper we report on current experience and review magnetic resonance safety protocols and literature in order to define practices surrounding MRI‐guided interventional and surgical procedures. Direct experience, the American College of Radiology White paper on MR Safety, and various other sources are summarized. Additional recommendations for interventional and surgical MRI‐guided procedures cover suite location/layout, accessibility, safety policy, personnel training, and MRI compatibility issues. Further information is freely available for sites to establish practices to minimize risk and ensure safety. Interventional and intraoperative MRI is emerging from its infancy, with twelve years since the advent of the field and well over 10,000 cases collectively performed. Thus, users of interventional and intraoperative MRI should adapt guidelines utilizing universal standards and terminology and establish a site‐specific policy. With policy enforcement and proper training, the interventional and intraoperative MR imaging suite can be a safe and effective environment.     

Evaluation of resource allocation and supply–demand balance in clinical practice with high‐cost technologies

Rationale, aims and objectives Japan has one of the highest numbers of high‐cost medical devices installed relative to its population. While evaluations of the distribution of these devices traditionally involve simple population‐based assessments, an indicator that includes the demand of these devices would more accurately reflect the situation. The purpose of this study was to develop an indicator of the supply–demand balance of such devices, using examples of magnetic resonance imaging scanners (MRI) and extracorporeal shockwave lithotripters (ESWL), and to investigate the relationship between this indicator, personnel distribution statuses and operating statuses at the prefectural level. Methods Using data from nation‐wide surveys and claims data from 16 hospitals, we developed an indicator based on the ratio of the supplied number of device units to the number of device units in demand for MRI and ESWL. The latter value was based on patient volume and utilization proportion. Correlation analyses were conducted between the supply–demand balances of these devices, personal distribution and operating statuses. Results Comparisons between our indicator and conventional population‐based indicators revealed that 15% and 30% of prefectures were at risk of underestimating the availability of MRI and ESWL, respectively. The numbers of specialist personnel/device units showed significant, negative correlations with our indicators in both devices. Conclusions Utilization‐based analyses of health care resource placement and utilization status provide a more accurate indication than simple population‐based assessments, and can assist decision makers in reviewing gaps between health policy and management. Such an indicator therefore has the potential to be a tool in helping to improve the efficiency of the allocation and placement of such devices.     

Microtechnologies in medicine: an overview.

Microsystems technology (MST) has become a significant enabler of novel medical devices and implants over the last years. Typical examples are MST units in cardiac rhythm management devices or in hearing implants. A classification of medical MST applications can be made according to their relationship with the anatomy that is based on the kind and duration of interaction with the human body: Class 1: Extra-corporeal devices such as telemetric health monitoring systems or point of care testing systems. Class 2: Intra-corporeal devices such as intelligent surgical instruments. Class 3: Temporarily incorporated or ingested devices, such as telemetric endoscopes. Class 4: Long-term implantable devices such as telemetric implants. Medical applications of MST are growing at double-digit compounded growth rates, leading to a forecasted global market volume of over USD 1 billion in 2006 or 2007, making MST devices a relevant segment of the medical technology market. The clinical foundation for promoting the use of MST in medicine is mainly based on the significant potential of MST to enable products that improve early disease detection and the monitoring of chronic illnesses. This refers to a number of the most important health problems such as cardiovascular disease, hypertension, diabetes and cancer, to name just a few. More recently microrobotics has become a relevant research area for enabling the atraumatic transport of MST-enhanced diagnostic and therapeutic devices inside the human body.     

Scientific Evaluation and Pricing of Medical Devices and Associated Procedures in France

Medical devices are many and various, ranging from tongue spatulas to implantable or invasive devices and imaging machines; their lifetimes are short, between 18 months and 5 years, due to incessant incremental innovation; and they are operator-dependent: in general, the clinical user performs a fitting procedure (hip implant or pacemaker), a therapeutic procedure using a non-implantable invasive device (arrhythmic site ablation probe, angioplasty balloon, extension spondyloplasty system, etc.) or follow-up of an active implanted device (long-term follow-up of an implanted cardiac defibrillator or of a deep brain stimulator in Parkinson’s patients).A round-table held during the XXVIII^th Giens Workshops meeting focused on the methodology of scientific evaluation of medical devices and the associated procedures with a view to their pricing and financing by the French National Health Insurance system. The working hypothesis was that the available data-set was sufficient for and compatible with scientific evaluation with clinical benefit. Post-registration studies, although contributing to the continuity of assessment, were not dealt with. Moreover, the focus was restricted to devices used in health establishments, where the association between devices and technical medical procedures is optimally representative.An update of the multiple regulatory protocols governing medical devices and procedures is provided. Issues more specifically related to procedures as such, to non-implantable devices and to innovative devices are then dealt with, and the proposals and discussion points raised at the round-table for each of these three areas are presented.     

Nitinol in magnetic resonance imaging.

Surgical and interventional instruments as well as implants can cause significant magnetic resonance image (MRI) artifacts. The artifacts can be used to visualize instruments, cannulae, guide wires, catheters during interventional MRI and Nitinol devices have proven to be useful for MRI procedures. Diagnostic imaging is often compromised in the area of an implant. Complete vanishing of signals occurs in close proximity or inside implants. The paper presents a fundamental evaluation of MRI artifact of Nitinol devices such as Stents, Vena Cava Filter, heart defect closure devices, cannulae, guide wire, localizer, anastomosis device, etc. in a 1.0 Tesla magnetic field. The American Society for Testing Materials (ASTM) recommendations for selection of sequences and test setup were used but the results of this paper are not sufficient for FDA approval.     

Can pacemakers, neurostimulators, leads, or guide wires be MRI safe? Technological concerns and possible resolutions.

The substantial benefits of magnetic resonance imaging are often denied to patients known to have implanted medical devices such as pacemakers and neurostimulators. Other patients are put at potential risk when they undergo an MRI procedure, even though specific informed consent is required regarding the possible MRI interactions with the implanted device. The medical community is currently divided over the actual extent of the MRI safety problem. In this report, insight is provided into the wide array of results achieved by many researchers; also, several options for producing medical devices that are inherently safe under worst-case MRI conditions are presented. As the problem is very complex and the variety of implants is large, this paper focuses on the problems of MRI-induced lead heating.     

Safety Planning for Intraoperative Magnetic Resonance Imaging

An intraoperative magnetic resonance imaging (MRI) suite (ie, a type of hybrid OR) is a high-risk zone that requires well-defined safety procedures to avoid adverse events related to magnetic forces. At one facility, the opening of an MRI suite necessitated the creation of a safety plan to establish guidelines, procedures, education, and nursing care specific to the use of MRI technology in the operative environment. Formation of a steering committee enabled a multidisciplinary approach to planning and implementation. The addition of two new perioperative nursing roles (ie, MRI control room monitor, MRI safety nurse) addressed staffing challenges related to strictly enforcing MRI safety procedures and delineating duties different from those of the RN circulator. Benefits of a safe approach to an MRI-integrated operative setting included the elimination of an entire surgical experience for patients who underwent additional resection of the tumor during their initial surgical procedure instead of postoperatively or during a subsequent return to the OR.