Radiofrequency-induced heating of broken and abandoned implant leads during magnetic resonance examinations

Device-Related Complications Associated with Cylindrical Lead Spinal Cord Stimulator Implants: A Comprehensive Review

PURPOSE OF REVIEW

Spinal cord stimulation (SCS) is an increasingly utilized therapy for the treatment of neuropathic pain conditions. Though minimally invasive and reversable, there are several important device-related complications that physicians should be aware of before offering this therapy to patients. The aim of this review is to synthesize recent studies in device-related SCS complications pertaining to cylindrical lead implantation and to discuss etiologies, symptoms and presentations, diagnostic evaluation, clinical implications, and treatment options.

RECENT FINDINGS

Device-related complications are more common than biologic complications. Device-related complications covered in this review include lead migration, lead fracture, lead disconnection, generator failure, loss of charge, generator flipping, hardware related pain, and paresthesia intolerance. The use of SCS continues to be an effective option for neuropathic pain conditions. Consideration of complications prior to moving forward with SCS trials and implantation is a vital part of patient management and device selection. Knowledge of these complications can provide physicians and other healthcare professionals the ability to maximize patient outcomes.

Safety of magnetic resonance imaging in patients with cardiac implantable electronic devices and abandoned or epicardial leads: a systematic review and meta-analysis

AIMS

Persistent reluctance to perform magnetic resonance imaging (MRI) in patients with abandoned and/or epicardial leads of cardiac implantable electronic devices is related to in vitro studies reporting tip heating. While there is a plethora of data on the safety of MRI in conditional and non-conditional implantable devices, there is a clear lack of safety data in patients with abandoned and/or epicardial leads.

METHODS AND RESULTS

Relevant literature was identified in Medline and CINAHL using the key terms 'magnetic resonance imaging' AND 'abandoned leads' OR 'epicardial leads'. Secondary literature and cross-references were supplemented. For reporting guidance, the Preferred Reporting Items for Systematic reviews and Meta-Analyses 2020 was used. International Prospective Register of Systematic Reviews (PROSPERO) registration number 465530. Twenty-one publications with a total of 656 patients with 854 abandoned and/or epicardial leads and 929 MRI scans of different anatomical regions were included. No scan-related major adverse cardiac event was documented, although the possibility of under-reporting of critical events in the literature should be considered. Furthermore, no severe device dysfunction or severe arrhythmia was reported. Mainly transient lead parameter changes were observed in 2.8% in the subgroup of patients with functional epicardial leads. As a possible correlate of myocardial affection, subjective sensations occurred mainly in the subgroup with abandoned epicardial leads (4.0%), but no change in myocardial biomarkers was observed.

CONCLUSION

Existing publications did not report any relevant adverse events for MRI in patients with abandoned and/or epicardial leads if performed according to strict safety guidelines. However, a more rigorous risk-benefit calculation should be made for patients with epicardial leads.

MRI in Patients with Cardiovascular Implantable Electronic Devices and Fractured or Abandoned Leads

Purpose To examine the clinical effect of lead length and lead orientation in patients with cardiac implantable electronic devices (CIEDs) and lead fragments or abandoned leads undergoing 1.5-T MRI. Materials and Methods This Health Insurance Portability and Accountability Act-compliant retrospective study included patients with CIEDs and abandoned leads or lead fragments undergoing 1.5-T MRI from March 2014 through July 2020. CIED settings before and after MRI were reviewed, with clinically significant variations defined as a composite of the change in capture threshold of at least 50%, in sensing of at least 40%, or in lead impedance of at least 30% between before MRI and after MRI interrogation. Adverse clinical events were assessed at MRI and up to 30 days after. Univariable and multivariable analysis was performed. Results Eighty patients with 126 abandoned CIED leads or lead fragments underwent 107 1.5-T MRI examinations. Sixty-seven patients (median age, 74 years; IQR, 66-78 years; 44 male patients, 23 female patients) had abandoned leads, and 13 (median age, 66 years; IQR, 52-74 years; nine male patients, four female patients) had lead fragments. There were no reported deaths, clinically significant arrhythmias, or adverse clinical events within 30 days of MRI. Three patients with abandoned leads had a significant change in the composite of capture threshold, sensing, or lead impedance. In a multivariable generalized estimating equation analysis, lead orientation, lead length, MRI type, and MRI duration were not associated with a significant change in the composite outcome. Conclusion Use of 1.5-T MRI in patients with abandoned CIED leads or lead fragments of varying length and orientation was not associated with adverse clinical events. Keywords: Cardiac Assist Devices, MRI, Cardiac Implantable Electronic Device Supplemental material is available for this article. © RSNA, 2024.

Joint British Society consensus recommendations for magnetic resonance imaging for patients with cardiac implantable electronic devices

Magnetic Resonance Imaging (MRI) is increasingly a fundamental component of the diagnostic pathway across a range of conditions. Historically, the presence of a cardiac implantable electronic device (CIED) has been a contraindication for MRI, however, development of MR Conditional devices that can be scanned under strict protocols has facilitated the provision of MRI for patients. Additionally, there is growing safety data to support MR scanning in patients with CIEDs that do not have MR safety labelling or with MR Conditional CIEDs where certain conditions are not met, where the clinical justification is robust. This means that almost all patients with cardiac devices should now have the same access to MRI scanning in the National Health Service as the general population. Provision of MRI to patients with CIED, however, remains limited in the UK, with only half of units accepting scan requests even for patients with MR Conditional CIEDs. Service delivery requires specialist equipment and robust protocols to ensure patient safety and facilitate workflows, meanwhile demanding collaboration between healthcare professionals across many disciplines. This document provides consensus recommendations from across the relevant stakeholder professional bodies and patient groups to encourage provision of safe MRI for patients with CIEDs.

SCMR expert consensus statement for cardiovascular magnetic resonance of patients with a cardiac implantable electronic device

Cardiovascular magnetic resonance (CMR) is a proven imaging modality for informing diagnosis and prognosis, guiding therapeutic decisions, and risk stratifying surgical intervention. Patients with a cardiac implantable electronic device (CIED) would be expected to derive particular benefit from CMR given high prevalence of cardiomyopathy and arrhythmia. While several guidelines have been published over the last 16 years, it is important to recognize that both the CIED and CMR technologies, as well as our knowledge in MR safety, have evolved rapidly during that period. Given increasing utilization of CIED over the past decades, there is an unmet need to establish a consensus statement that integrates latest evidence concerning MR safety and CIED and CMR technologies. While experienced centers currently perform CMR in CIED patients, broad availability of CMR in this population is lacking, partially due to limited availability of resources for programming devices and appropriate monitoring, but also related to knowledge gaps regarding the risk-benefit ratio of CMR in this growing population. To address the knowledge gaps, this SCMR Expert Consensus Statement integrates consensus guidelines, primary data, and opinions from experts across disparate fields towards the shared goal of informing evidenced-based decision-making regarding the risk-benefit ratio of CMR for patients with CIEDs.

A new method to improve RF safety of implantable medical devices using inductive coupling at 3.0 T MRI

OBJECTIVE

To enhance RF safety when implantable medical devices are located within the body coil but outside the imaging region by using a secondary resonator (SR) to reduce electric fields, the corresponding specific absorption rate (SAR), and temperature change during MRI.

MATERIALS AND METHODS

This study was conducted using numerical simulations with an American Society for Testing and Materials (ASTM) phantom and adult human models of Ella and Duke from Virtual Family Models, along with corresponding experimental results of temperature change obtained using the ASTM phantom. The circular SR was designed with an inner diameter of 150 mm and a width of 6 mm. Experimental measurements were carried out using a 3 T Medical Implant Test System (MITS) body coil, electromagnetic (EM) field mapping probes, and an ASTM phantom.

RESULTS

The magnitudes of B1+ (|B1+|) and SAR1g were reduced by 15.2% and 5.85% within the volume of interest (VoI) of an ASTM phantom, when a SR that generates opposing electromagnetic fields was utilized. Likewise, the Δ|B1+| and ΔSAR1g were reduced by up to 56.7% and 57.5% within the VoI of an Ella model containing a copper rod when an opposing SR was used.

CONCLUSION

A novel method employing the designed SR, which generates opposing magnetic fields to partially shield a sample, has been proposed to mitigate the risk of induced-RF heating at the VoI through numerical simulations and corresponding experiments under various conditions at 3.0 T.

Efficient prediction of MRI gradient-induced heating for guiding safety testing of conductive implants

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.

Implants talk to each-other: RF heating changes when two DBS leads are present simultaneously during MRI

Deep brain stimulation (DBS) has proven to be an effective treatment for Parkinson's disease and other brain disorders. The procedure often involves implanting two elongated leads aimed at specific brain nuclei in both the left and right hemispheres. However, evaluating the safety of MRI in patients with such implants has only been done on an individual lead basis, ignoring the possibility of crosstalk between the leads. This study evaluates the impact of crosstalk on power deposition at the lead tip through numerical simulation and phantom experiments. We used CT images to obtain patient-specific lead trajectories and compared the power deposition at the lead tip in cases with bilateral and unilateral DBS implants. Our results indicate that the RF power deposition at the lead tip can vary by up to 6-fold when two DBS leads are present together compared to when only one lead is present. Experimental measurements in a simplified case of two lead-only DBS systems confirmed the existence of crosstalk.Clinical Relevance-Our results indicate that RF heating of implanted leads during MRI can be affected by the presence of another lead in the body, which may increase or decrease the power deposition in the tissue depending on the position and configuration of the leads.

Towards an integrated radiofrequency safety concept for implant carriers in MRI based on sensor-equipped implants and parallel transmission

To protect implant carriers in MRI from excessive radiofrequency (RF) heating it has previously been suggested to assess that hazard via sensors on the implant. Other work recommended parallel transmission (pTx) to actively mitigate implant-related heating. Here, both ideas are integrated into one comprehensive safety concept where native pTx safety (without implant) is ensured by state-of-the-art field simulations and the implant-specific hazard is quantified in situ using physical sensors. The concept is demonstrated by electromagnetic simulations performed on a human voxel model with a simplified spinal-cord implant in an eight-channel pTx body coil at 3 T . To integrate implant and native safety, the sensor signal must be calibrated in terms of an established safety metric (e.g., specific absorption rate [SAR]). Virtual experiments show that E -field and implant-current sensors are well suited for this purpose, while temperature sensors require some caution, and B 1 probes are inadequate. Based on an implant sensor matrix Q s , constructed in situ from sensor readings, and precomputed native SAR limits, a vector space of safe RF excitations is determined where both global (native) and local (implant-related) safety requirements are satisfied. Within this safe-excitation subspace, the solution with the best image quality in terms of B 1 + magnitude and homogeneity is then found by a straightforward optimization algorithm. In the investigated example, the optimized pTx shim provides a 3-fold higher mean B 1 + magnitude compared with circularly polarized excitation for a maximum implant-related temperature increase ∆ T imp ≤ 1 K . To date, sensor-equipped implants interfaced to a pTx scanner exist as demonstrator items in research labs, but commercial devices are not yet within sight. This paper aims to demonstrate the significant benefits of such an approach and how this could impact implant-related RF safety in MRI. Today, the responsibility for safe implant scanning lies with the implant manufacturer and the MRI operator; within the sensor concept, the MRI manufacturer would assume much of the operator's current responsibility.

Computational dosimetry in MRI in presence of hip, knee or shoulder implants: do we need accurate surgery models?

Objective.To quantify the effects of different levels of realism in the description of the anatomy around hip, knee or shoulder implants when simulating, numerically, radiofrequency and gradient-induced heating in magnetic resonance imaging. This quantification is needed to define how precise the digital human model modified with the implant should be to get realistic dosimetric assessments.Approach. The analysis is based on a large number of numerical simulations where four 'levels of realism' have been adopted in modelling human bodies carrying orthopaedic implants.Main results. Results show that the quantification of the heating due to switched gradient fields does not strictly require a detailed local anatomical description when preparing the digital human model carrying an implant. In this case, a simple overlapping of the implant CAD with the body anatomy is sufficient to provide a quite good and conservative estimation of the heating. On the contrary, the evaluation of the electromagnetic field distribution and heating caused by the radiofrequency field requires an accurate description of the tissues around the prosthesis.Significance. The results of this paper provide hints for selecting the 'level of realism' in the definition of the anatomical models with embedded passive implants when performing simulations that should reproduce, as closely as possible, thein vivoscenarios of patients carrying orthopaedic implants.

Radiofrequency-induced heating of broken and abandoned implant leads during magnetic resonance examinations

Purpose

The risks of RF‐induced heating of active implantable medical device (AIMD) leads during MR examinations must be well understood and realistically assessed. In this study, we evaluate the potential additional risks of broken and abandoned (cut) leads.

Methods

First, we defined a generic AIMD with a metallic implantable pulse generator (IPG) and a 100‐cm long lead containing 1 or 2 wires. Next, we numerically estimated the deposited in vitro lead‐tip power for an intact lead, as well as with wire breaks placed at 10 cm intervals. We studied the effect of the break size (wire gap width), as well as the presence of an intact wire parallel to the broken wire, and experimentally validated the numeric results for the configurations with maximum deposited in vitro lead‐tip power. Finally, we performed a Tier 3 assessment of the deposited in vivo lead‐tip power for the intact and broken lead in 4 high resolution virtual population anatomic models for over 54,000 MR examination scenarios.

Results

The enhancement of the deposited lead‐tip power for the broken leads, compared to the intact lead, reached 30‐fold in isoelectric exposure, and 16‐fold in realistic clinical exposures. The presence of a nearby intact wire, or even a nearby broken wire, reduced this enhancement factor to <7‐fold over the intact lead.

Conclusion

Broken and abandoned leads can pose increased risk of RF‐induced lead‐tip heating to patients undergoing MR examinations. The potential enhancement of deposited in vivo lead‐tip power depends on location and type of the wire break, lead design, and clinical routing of the lead, and should be carefully considered when performing risk assessment for MR examinations and MR conditional labeling.