SciCombinator

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Journal: Magnetic resonance imaging clinics of North America

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Magnetic resonance (MR) imaging-related injuries have continued to occur at an alarming rate during more than 3 decades of use. Persistently reported MR imaging-related injuries are caused by (1) radiofrequency thermal effect burns, (2) bruising from table top and coil-related mechanical injuries, (3) magnetic field-related support equipment malfunction, (4) magnetic field-related projectile trauma, (5) gradient switching noise hearing loss. A cohesive and educated MR imaging community under the guidance of a defined management structure is essential for monitoring and mitigating MR imaging risks. This article offers an approach for decreasing MR imaging-related injury risks.

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Although comparatively much younger as a discipline, these early decades of the structure of practice of MR imaging safety have developed in an alarmingly ad hoc manner, particularly when contrasted with contemporary ionizing radiation safety. This absence of structure and metrics for MR imaging safety has impaired the direct safety best practices for the recognizable domains of clinical and operational MR safety. If the built environment of MR imaging is effectively the hardware of the mechanism of health care delivery, then the appropriateness of this hardware to the software (clinical and operational practices) is of great importance.

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Conducting magnetic resonance imaging (MRI) safety screening is not a new idea and has developed as a proved method in efforts to ensure patient safety and prevent accidents in the magnetic resonance (MR) environment. A growing number of surgical procedures with implanted medical devices have complicated MR screening and added to the workload of Level 2 personnel. Level 2 staff members are trained to understand and implement screening procedures and should be consulted by all individuals requiring access to the MR environment. All the steps have potential gaps, but as a whole offer efficient and effective tools to alleviate MR-related accidents.

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Gadolinium (Gd)-based contrast agents (GBCAs) have revolutionized of MR imaging, enabling physicians to obtain life-saving medical information that often cannot be obtained with unenhanced MR imaging or other imaging modalities. Since regulatory approval in 1988, more than 450 million intravenous GBCA doses have been administered worldwide, with an extremely favorable pharmacologic safety profile. Recent evidence has demonstrated, however, that a small fraction of Gd is retained in human tissues. No direct correlation between Gd retention and clinical effects has been confirmed; however, a subset of patients have attributed various symptoms to GBCA exposure. This review details current knowledge regarding GBCA safety.

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MRI is a powerful diagnostic tool with excellent soft tissue contrast that uses nonionizing radiation. These advantages make MRI an appealing modality for imaging the pregnant patient; however, specific risks inherent to the magnetic resonance environment must be considered. MRI may be performed without and/or with intravenous contrast, which adds further fetal considerations. The risks of MRI with and without intravenous contrast are reviewed as they pertain to the pregnant or lactating patient and to the fetus and nursing infant. Relevant issues for gadolinium-based contrast agents and ultrasmall paramagnetic iron oxide particles are reviewed.

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Magnetic resonance (MR) imaging relies on a strong static magnetic field in conjunction with careful orchestration of pulsed linear gradient magnetic fields and radiofrequency magnetic fields in order to generate images. The interaction of these fields with patients as well as materials with magnetic or conducting properties can be a source of risk in the MR environment. This article provides a basic review of the physical underpinnings of the primary risks in MR imaging to foster development of intuition with respect to both patient and risk management in the MR environment.

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Three dimensionally mapping the relative spatial distributions and magnitudes of the various energy sources used in the MR imaging process for a given MR scanner potentiates an understanding of the relative spatial distributions of the potential risks associated with each of these energies or fields. By systematically analyzing the data for each energy source relative to the location and type of implants, devices, and/or foreign bodies within a specific patient, one can prospectively assess and even begin to quantify the risks of exposing that patient to selected MR scanner hardware for a requested diagnostic study.

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New implanted medical devices continue to be made available for treatment of medical conditions. Many recipients can benefit from the diagnostic power of MR imaging. Provisions must be made to determine if these patients can be safely scanned. Metal-containing devices can be considered either MR unsafe or conditional. It is essential that all components of an implanted system are completely and accurately identified, with the most restrictive MR safety condition dictating the scanning approach. MR safety considerations for major classes of implanted devices are discussed, recognizing that there have been reports of serious device-related MR safety incidents.

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MR imaging of patients with implanted devices has become common, with conditions for safe scanning defined in MR Conditional labeling of the medical device. This resulted from collaboration among medical device manufacturing, MR imaging scanner manufacturing, and regulatory authority communities. These efforts resulted in engineering testing standards and methods that enable evaluation and certification of devices for safe scanning of patients within prescribed MR imaging scanning conditions. This article provides a practical perspective on test methods that address distinct potential patient hazards. It also provides general guidelines for how a clinician might think about potential hazards, and guidance on common misconceptions.

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The arrival of 7T MR imaging into the clinic represents a significant step-change in MR technology. This article describes safety concerns associated with imaging at 7T, including the increased magnetic forces on magnetic objects at 7T and the interaction of the 300 MHz (Larmor) radiofrequency energy with tissue in the body. A dedicated multidisciplinary 7T Safety team should develop safety policies and procedures to address these safety challenges and keep abreast of best practice in the field. The off-label imaging of implanted devices is discussed, and also the need for staff training to deal with complexities of patient handling and image interpretation.