Managing Patients With Unlabeled Passive Implants on MR Systems Operating Below 1.5 T.

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.

Benefits of Using Magnetic Resonance Imaging During Breast Tissue Expansion: Literature Review and Case Series.

Breast cancer results in up to 1.6 million new candidates for yearly breast reconstruction (BR) surgery. Two-stage breast reconstruction surgery with the use of a tissue expander (TE) is a common approach to reconstructing the breast after mastectomy. However, a common disadvantage encountered with the traditional breast TE is the magnetic injection port, which has been reported to cause injuries in patients undergoing magnetic resonance (MR) imaging. Therefore this type of breast TE is labeled "MR unsafe." Recent technological advances have incorporated radio-frequency identification (RFID) technology in the TE to allow for the location of the injection port without magnetic components, resulting in an MR-conditional TE. This paper aims to review the information regarding the safety profile of TEs with magnetic ports and to gather distinct clinical scenarios in which an MR-conditional TE benefits the patient during the BR process. A literature review ranging from 2018 to 2022 was performed with the search terms: "tissue expander" OR "breast tissue expander" AND "magnetic resonance imaging" OR "MRI." Additionally, a case series was collected from each of the authors' practices. The literature search yielded 13 recent peer-reviewed papers, and 6 distinct clinical scenarios were compiled and discussed. Most clinicians find MRI examinations to be the state-of-art diagnostic imaging modality. However, due to the preexisting risks associated with TEs with magnetic ports, the MRI labeling classification should be considered when deciding which TE is the most appropriate for the patient requiring MRI examinations.

Near field communication (NFC) device: Evaluation of MRI issues.

OBJECTIVE: Near field communication (NFC) is a wireless, short-range, secure communication technology that may be used for healthcare-related applications. An NFC device was recently developed that was intended for implantation in the dorsal fascia, above the interosseous compartment of the hand. This implant uses a ferrite rod to increase the distance of communication between devices. The purpose of this investigation was to evaluate MRI issues for this NFC device using standardized techniques and well-accepted methodology. METHODS: The NFC device (Vivokey Spark 2, Cryptobionic Implant, Vivokey Technologies, www.vivokey.com) was assessed for magnetic field interactions (force and torque) at 3-Tesla, magnetic field interactions according to the simulated intended use of the implant, MRI-related heating at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz, functional change associated with MRI conditions at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz, and artifacts at 3-Tesla. RESULTS: The mean deflection angle was 90° ± 0 and torque was "positive". However, tests evaluating the simulated intended use of the NFC device demonstrated no movement, displacement, or rotational alignment. The highest temperature changes at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz were 1.7 °C and 1.9 °C, respectively. There was no change in the operational capabilities of the NFC device related to the MRI exposures. Artifacts were relatively large in comparison to the size of the NFC device. CONCLUSIONS: The findings indicated that the particular NFC device that underwent evaluation is "MR Conditional" for a patient undergoing MRI at 1.5-Tesla or 3-Tesla, operating the scanner in the Normal Operating Mode (i.e., default whole-body averaged SAR of 2.0-W/kg). Notably, this is the first NFC device evaluated for MRI-related issues.

Breast Tissue Expander With Radiofrequency Identification Port: Assessment of MRI Issues.

OBJECTIVE. Breast tissue expanders with magnetic ports are MRI unsafe, preventing patients from benefiting from the diagnostic capabilities of MRI. A tissue expander was recently developed with a radiofrequency identification (RFID) port used for needle location and expansion that may be acceptable for a patient undergoing MRI. The purpose of this investigation was to evaluate MRI issues using standardized techniques and well-accepted methods for this tissue expander with RFID port. MATERIALS AND METHODS. The breast tissue expander with RFID port (Motiva Flora Tissue Expander, Establishment Labs) was assessed for magnetic field interactions (translational attraction and torque, 3 T), MRI-related heating (1.5 T/64 MHz and 3 T/128 MHz), artifacts (3 T), and functional changes associated with different MRI conditions (1.5 T/64 MHz and 3 T/128 MHz). RESULTS. Magnetic field interactions were minor (deflection angle of 2° and no torque) and thus will not pose a risk. At 1.5 T/64 MHz and 3 T/128 MHz, the highest temperature elevations (1.7°C and 1.9°C, respectively) were physiologically inconsequential. The tissue expander with RFID port exhibited relatively small artifacts on MRI. Exposures of the tissue expander with RFID port to different MRI conditions did not impact the ability to localize the RFID port or to read the electronic serial number. CONCLUSION. The findings indicated that this tissue expander with RFID port is "MR Conditional" for a patient referred for MRI at 1.5 T or 3 T. Importantly, the relatively small artifact associated with this implant offers potential advantages for patients undergoing MRI compared with tissue expanders that have magnetic ports that create substantial signal losses and distortions on MR images.

MRI Evaluation of an Atrial-Anchored Transcatheter Mitral Valve Replacement Implant.

OBJECTIVE. A medical implant that is made from metal must undergo proper MRI testing to ensure patient safety. The purpose of this investigation was to assess issues with MRI with a newly developed atrial-anchored transcatheter mitral valve replacement (TMVR) implant. MATERIALS AND METHODS. The atrial-anchored TMVR implant underwent an in vitro evaluation for MRI safety issues using standardized techniques and well-accepted methods. Magnetic field interactions including translational attraction and torque and artifacts were tested at 3 T. MRI-related heating was assessed at 1.5 T/64 MHz and 3 T/128 MHz using numeric simulations with analytical modeling and experimental testing. RESULTS. The atrial-anchored TMVR implant exhibited minor magnetic field interactions (9° deflection angle and no torque) at 3 T. The findings from the numeric simulations with analytical modeling were used to guide the placement of the implant in the phantom for the heating test and to identify the position on the implant that would result in the highest temperature rise. The highest temperature elevations recorded for the TMVR implant obtained on MRI at 1.5 T/64 MHz and 3 T/128 MHz were 2.7°C and 2.4°C, respectively. The maximum artifact size seen on a gradient echo pulse sequence extended approximately 5 mm relative to the size of the implant. CONCLUSION. The results of the tests performed on the atrial-anchored TMVR implant revealed no substantial concerns with respect to the conditions used in this investigation. Therefore, a patient with this new implant can safely undergo MRI by following the specific conditions defined by this study. The implant was deemed MR Conditional.

ACR guidance document on MR safe practices: Updates and critical information 2019.

The need for a guidance document on MR safe practices arose from a growing awareness of the MR environment's potential risks and adverse event reports involving patients, equipment, and personnel. Initially published in 2002, the American College of Radiology White Paper on MR Safety established de facto industry standards for safe and responsible practices in clinical and research MR environments. The most recent version addresses new sources of risk of adverse events, increases awareness of dynamic MR environments, and recommends that those responsible for MR medical director safety undergo annual MR safety training. With regular updates to these guidelines, the latest MR safety concerns can be accounted for to ensure a safer MR environment where dangers are minimized. Level of Evidence: 1 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;51:331-338.

MRI safety and imaging artifacts evaluated for a cannulated screw used for guided growth surgery.

OBJECTIVE: Percutaneously-placed cannulated screws are the implant of choice for treatment of skeletal deformity associated with growing children that have spastic cerebral palsy (CP). These patients often require MRI examinations throughout their childhood to evaluate associated comorbidities and frequently for research protocols. There are concerns related to the use of MRI when metallic implants are present. Therefore, this study characterized MRI safety and imaging artifacts for a cannulated screw commonly used for guided growth. METHODS: Standardized and well-accepted in vitro techniques were used to evaluate a cannulated screw (4.5 mm diameter x 50 mm length, 316 L stainless steel) for MRI issues. Static magnetic field interactions (i.e., translational attraction and torque) and artifacts were tested at 3-Tesla. Radiofrequency-related heating was assessed at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz using relatively high levels of RF energy (whole-body averaged specific absorption rates of 2.7 W/kg and 2.9-W/kg, respectively). Artifacts were determined using T1-weighted, spin echo and gradient echo pulse sequences. RESULTS: The cannulated screw exhibited minor magnetic field interactions (14° deflection angle, no torque). The highest temperature changes at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz MRI were 2.1 °C and 2.4 °C, respectively. The maximum artifact size on a gradient echo sequence extended 20 mm relative to the dimensions of the implant. CONCLUSIONS: The in vitro tests performed on the cannulated screw indicated that there were no substantial concerns with respect to the use of 1.5- and 3-Tesla MRI. Therefore, a patient with this cannulated screw can safely undergo MRI by following specific conditions to ensure safety.

Evaluation of MRI Issues for a New Wirelessly Powered, Spinal Cord Stimulation Lead With Receiver.

OBJECTIVE. MRI is an imaging modality frequently ordered for patients with neuromodulation systems implanted for spinal cord stimulation. The purpose of this investigation was to evaluate MRI safety issues (magnetic field interactions, MRI-related heating, functional disturbances, and artifacts) for a new wirelessly powered lead with receiver used for SCS. MATERIALS AND METHODS. Lead samples underwent in vitro evaluation for MRI safety issues using standardized techniques. Magnetic field interactions (i.e., translational attraction and torque) and artifacts were tested at 3 T. MRI-related heating was performed at 1.5 T/64 MHz and 3 T/128 MHz using two different methods: numerical simulations with analytical modeling and physical testing. Possible functional disturbances were evaluated under exposures to 1.5-T/64-MHz and 3-T/128-MHz MRI conditions. RESULTS. The lead exhibited minor magnetic field interactions (22° deflection angle, no torque) at 3 T. The highest temperature change recorded at 1.5 T/64 MHz and 3 T/128 MHz was 3.8°C and 11.3°C, respectively. Exposures to MRI conditions did not damage or alter the functional aspects of the leads. The maximum artifact size seen on a gradient-echo pulse sequence extended approximately 10 mm relative to the size of the lead. CONCLUSION. The MRI tests performed on patients with the new lead with receiver revealed no substantial concerns with respect to the conditions that we provide in the safety guidelines that were based on the results of this investigation. Therefore, MRI examinations will result in acceptable heating when conducted at appropriate whole-body-averaged specific absorption rate levels (i.e., 2.0 W/kg at 1.5 T/64 MHz and 0.3 W/kg at 3 T/128 MHz, corresponding to adjusted temperature rises of 3.6°C and 1.2°C, respectively). Therefore, patients with this wirelessly powered lead and receiver implanted can safely undergo MRI examinations under specific conditions.

Safety Considerations of 7-T MRI in Clinical Practice.

Although 7-T MRI has recently received approval for use in clinical patient care, there are distinct safety issues associated with this relatively high magnetic field. Forces on metallic implants and radiofrequency power deposition and heating are safety considerations at 7 T. Patient bioeffects such as vertigo, dizziness, false feelings of motion, nausea, nystagmus, magnetophosphenes, and electrogustatory effects are more common and potentially more pronounced at 7 T than at lower field strengths. Herein the authors review safety issues associated with 7-T MRI. The rationale for safety concerns at this field strength are discussed as well as potential approaches to mitigate risk to patients and health care professionals.

Reconsidering the "MR Unsafe" breast tissue expander with magnetic infusion port: A case report and literature review.

Breast tissue expanders (TEs) with magnetic infusion ports are labeled "MR Unsafe." Therefore, patients with these implants are typically prevented from undergoing magnetic resonance imaging (MRI). We report a patient with a total submuscular breast TE who inadvertently underwent an MRI exam. She subsequently developed expander exposure, requiring explantation and autologous reconstruction. The safety profile of TEs with magnetic ports and the use of MRI in patients with these implants is surprisingly controversial. Therefore, we present our case report, a systematic literature review, and propose procedural guidelines to help ensure the safety of patients with TEs with magnetic ports that need to undergo MRI exams.

7-Tesla MRI of the brain in a research subject with bilateral, total knee replacement implants: Case report and proposed safety guidelines.

Recently, the first 7-T MR system was approved for clinical use in the United States. Unfortunately, relatively few metallic implants have undergone testing to determine if they are acceptable or pose hazards to research subjects and patients at this ultra-high-field strength. Therefore, in lieu of not performing a research or clinical MRI exam at 7-T, the supervising physician may make a decision to scan the individual with an untested metallic implant based on an analysis of the risks vs. the benefits. We present a case report of a research subject with bilateral, total knee replacement implants that safely underwent MRI of the brain at 7-T and provide guidelines for healthcare professionals to follow in order to ensure safety in research subjects or patients with metallic implants referred for 7-T scans.

Assessment of metallic patient support devices and other items at 7-Tesla: Findings applied to 46 additional devices.

OBJECTIVE: Recently, the first 7-Tesla MR system was approved for clinical use in Europe and the United States. Unfortunately, few metallic objects have undergone testing in association with this high-field-strength scanner, including essential equipment such as patient support devices and other items. Therefore, the objective of this investigation was to assess metallic patient support devices and other items for translational attraction at 7-Tesla. METHODS: Thirteen different metallic items (e.g., gurney, Mayo stand, step stool, utility table, wheelchair, etc.) underwent testing for translational attraction using a previously described methodology in association with a clinical 7-T MR system. The findings were categorized as pass (no translational attraction) or fail (the item was attracted by the scanner). RESULTS: Every metallic item tested exhibited a lack of magnetism while in a worst-case use position and, thus, passed the test for translational attraction in associated with the 7-Tesla MR system. CONCLUSIONS: The different thirteen different metallic patient support devices and other items can be designated as MR Conditional at 7-T or less. Furthermore, because each item represented a worst-case with respect to its mass and the type of metallic material used for its fabrication, the results can be applied to 46 additional smaller items made from the same material or material with a lower magnetic susceptibility. This expanded list of essential patient support devices and other items will facilitate the clinical use of a comparable 7-Tesla scanner, or another UHF scanner with similar fringe field characteristics.

Assessment of MRI issues at 1.5 T for the Temperature Logger Implant.

PURPOSE: The Temperature Logger Implant is a newly developed device that is capable of providing data for animal studies on thermoregulatory function, hibernation, hypothermia, and general health. During research, it may be necessary to conduct a magnetic resonance imaging (MRI) examination on an animal with this device implanted to assess anatomical changes or other conditions. Notably, this new device was specially designed to be unaffected by the electromagnetic fields used for MRI. Therefore, to verify that there would be no problems related to MRI, the purpose of this investigation was to evaluate MRI-related issues for the Temperature Logger Implant. METHODS: Tests were performed on the Temperature Logger Implant using well-accepted techniques to evaluate magnetic field interactions (translational attraction and torque, 1.5 T), MRI-related heating (whole body averaged specific absorption rate, 2.9 W/kg), artifacts (T1-weighted, spin echo and gradient echo pulse sequences), and functional changes related to exposure to eight different imaging conditions. RESULTS: Magnetic field interactions were relatively low (deflection angle 4°, no torque) and heating was minor (highest temperature rise, > 1.1 °C) indicating that these factors will not pose a hazard to an animal. The largest artifact (gradient echo pulse sequence) extended 10 mm from the size and shape of the Temperature Logger Implant. Exposure to the eight different conditions at 1.5 T/ 64 MHz did not alter or damage the operational aspects of the device. CONCLUSIONS: The findings demonstrated that MRI can be performed safely on an animal with this new Temperature Logger Implant and, thus, this device is deemed "MR Conditional" (i.e., using current labeling terminology), according to the conditions used in this investigation.

Evaluation of Magnetic Resonance Imaging Safety and Imaging Issues Associated with the Occlusion Balloon Used during Fetoscopic Endoluminal Tracheal Occlusion.

INTRODUCTION: Congenital diaphragmatic hernias can be successfully treated by fetoscopic tracheal occlusion (FETO), a minimally invasive procedure that may improve postnatal survival. The endoluminal balloon utilized for FETO contains a metallic component that may pose possible risks for the fetus and mother related to the use of magnetic resonance imaging (MRI). The objective of this study is to evaluate MRI-related imaging and safety issues (magnetic field interactions, heating, and artifacts) for the occlusion balloon used in FETO. MATERIALS AND METHODS: Using well-established techniques, tests were performed to assess magnetic field interactions (translational attraction and torque) and MRI-related heating and artifacts that occurred when exposing the occlusion balloon typically used for FETO (Goldbal2, Balt, www.balt.fr) to a 3-T magnet. MRI-related heating was determined by placing the occlusion balloon in a gelled-saline-filled, head-torso phantom and conducting MRI at relatively high, whole-body-averaged specific absorption rate (2.9 W/kg) for 15 min. Artifacts were measured in association with the use of T1-weighted, spin-echo and gradient-echo pulse sequences. RESULTS: The balloon displayed minor magnetic field interactions and physiologically inconsequential heating (highest temperature rise: 0.1°C above background). Artifacts extended approximately 10 mm from the occlusion balloon on the gradient-echo pulse sequence, suggesting that anatomy located at a position greater than this distance may be visualized on MRI. DISCUSSION: In this paper, we demonstrate that the risks of performing MRI at 3 T or less in a patient who has this occlusion balloon in place are acceptable (or MR conditional, using current terminology).

In Vitro Magnetic Resonance Imaging Evaluation of Fragmented, Open-Coil, Percutaneous Peripheral Nerve Stimulation Leads.

OBJECTIVE: Percutaneous peripheral nerve stimulation (PNS) is an FDA-cleared pain treatment. Occasionally, fragments of the lead (MicroLead, SPR Therapeutics, LLC, Cleveland, OH, USA) may be retained following lead removal. Since the lead is metallic, there are associated magnetic resonance imaging (MRI) risks. Therefore, the objective of this investigation was to evaluate MRI-related issues (i.e., magnetic field interactions, heating, and artifacts) for various lead fragments. METHODS: Testing was conducted using standardized techniques on lead fragments of different lengths (i.e., 50, 75, and 100% of maximum possible fragment length of 12.7 cm) to determine MRI-related problems. Magnetic field interactions (i.e., translational attraction and torque) and artifacts were tested for the longest lead fragment at 3 Tesla. MRI-related heating was evaluated at 1.5 Tesla/64 MHz and 3 Tesla/128 MHz with each lead fragment placed in a gelled-saline filled phantom. Temperatures were recorded on the lead fragments while using relatively high RF power levels. Artifacts were evaluated using T1-weighted, spin echo, and gradient echo (GRE) pulse sequences. RESULTS: The longest lead fragment produced only minor magnetic field interactions. For the lead fragments evaluated, physiologically inconsequential MRI-related heating occurred at 1.5 Tesla/64 MHz while under certain 3 Tesla/128 MHz conditions, excessive temperature elevations may occur. Artifacts extended approximately 7 mm from the lead fragment on the GRE pulse sequence, suggesting that anatomy located at a position greater than this distance may be visualized on MRI. CONCLUSIONS: MRI may be performed safely in patients with retained lead fragments at 1.5 Tesla using the specific conditions of this study (i.e., MR Conditional). Due to possible excessive temperature rises at 3 Tesla, performing MRI at that field strength is currently inadvisable.

Assessment of MRI issues for a new cerebral spinal fluid shunt, gravitational valve (GV).

PURPOSE: A gravitational valve (GV) may be used to treat hydrocephalus, offering possible advantages that include avoidance of over drainage and long-term complications. Because a GV is made from metal, there are potential safety and other problems related to the use of MRI. The objective of this investigation was to evaluate MRI-related issues (i.e., magnetic field interactions, heating, and artifacts) for a newly developed, metallic GV. METHODS: Tests were performed on the GV (GAV 2.0) using well-accepted techniques to assess magnetic field interactions (translational attraction and torque, 3-Tesla), MRI-related heating (1.5-T/64-MH and 3-T/128-MHz, whole body averaged SAR, 2.7-W/kg and 2.9-W/kg, respectively), artifacts (3-Tesla; gradient echo and T1-weighted, spin echo sequences), and possible functional changes related to exposures to different MRI conditions (exposing six samples each to eight different pulse sequences at 1.5-T/64-MHz and 3-T/128-MHz). RESULTS: Magnetic field interactions were not substantial (deflection angle 2°, no torque) and heating was minor (highest temperature rise, ≥1.9°C, highest background temperature rise, ≥1.7°C). Artifacts on the gradient echo pulse sequence extended approximately 10mm from the size and shape of the GV. The different exposures to 1.5-T/64-MHz and 3-T/128-MHz conditions did not alter or damage the operational aspects of the GV samples. CONCLUSIONS: The findings demonstrated that MRI can be safely used in patients with this GV and, thus, this metallic implant is deemed acceptable or "MR Conditional" (i.e., using current labeling terminology), according to the conditions used in this study.

Gadolinium deposition in the brain: summary of evidence and recommendations.

Emerging evidence has linked MRI signal changes in deep nuclei of the brain with repeated administration of gadolinium-based contrast agents. Gadolinium deposits have been confirmed in brain tissue, most notably in the dentate nuclei and globus pallidus. Although some linear contrast agents appear to cause greater MRI signal changes than some macrocyclic agents, deposition of gadolinium has also been observed with macrocyclic agents. However, the extent of gadolinium deposition varies between agents. Furthermore, the clinical significance of the retained gadolinium in the brain, if any, remains unknown. No data are available in human beings or animals to show adverse clinical effects due to the gadolinium deposition in the brain. On behalf of the International Society for Magnetic Resonance in Medicine, we present recommendations for the clinical and research use of gadolinium-based contrast agents. These recommendations might evolve as new evidence becomes available.