Pacemakers in MRI for the Neuroradiologist

MRI safety screening of children with implants: updates and challenges

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.

Acute Ischemic Stroke: MR Imaging-Based Paradigms

Multimodal MR imaging provides valuable information in the management of patients with acute ischemic stroke (AIS), with diagnostic, therapeutic, and prognostic implications. MR imaging plays a critical role in treatment decision making for (1) thrombolytic treatment of AIS patients with unknown symptom-onset and (2) endovascular treatment of patients with large vessel occlusion presenting beyond 6 hours from the symptom onset. MR imaging provides the most accurate information for detection of ischemic brain and is invaluable for differentiating AIS from stroke mimics.

2020 MR Safety for Cardiac Devices: An Update for Radiologists

Magnetic resonance imaging (MRI) is a unique and powerful diagnostic tool that provides images without ionizing radiation and, at times, can be the only modality to properly assess and diagnose some pathologies. Although many patients will need an MRI in their lifetime, many of them are still being unjustly denied access to it due to what were once considered absolute contraindications, including MR nonconditional pacemakers and implantable cardioverter-defibrillators. However, there are a number of large studies that have recently demonstrated that MRI can safely be performed in these patients under certain conditions. In addition, there are an increasing number of novel cardiac devices implanted in patients who may require an MRI. Radiologists need to familiarize themselves with these devices, identify which patients with these devices can safely undergo MRI, and under which conditions. In this article, we will review the current literature on MR safety and cardiac devices, elaborate on how to safely image patients with cardiac devices, and share the expertise of our tertiary cardiac institute.

Neuroimaging for the Neurologist: Clinical MRI and Future Trends

MRI is a commonly used diagnostic tool in neurology, and all neurologists should possess a working knowledge of imaging fundamentals. An overview of current and impending MRI techniques is presented to help the referring clinician communicate better with the imaging department, understand the utility and limitations of current and emerging technology, improve specificity and appropriateness when ordering MRI studies, and recognize key findings.

Chest radiographs of cardiac devices (Part 1): Cardiovascular implantable electronic devices, cardiac valve prostheses and Amplatzer occluder devices

Several new innovative cardiac devices have been created over the last few decades. Chest radiographs (CXRs) are the most common imaging investigations undertaken because of their value in evaluating the cardiorespiratory system. It is important for the interpreting radiologist to not only identify these iatrogenic objects but also to assess for their accurate placement, as well as for any complications related to their placement, which may be seen either on the immediate post-procedural CXR or on a follow-up CXR.

Safety of Laser Interstitial Thermal Therapy in Patients With Pacemakers

BACKGROUND AND IMPORTANCE

Laser interstitial thermal therapy (LiTT) has increasingly been used as a treatment option for medically refractory epilepsy, tumors, and radiation necrosis. The use of LiTT requires intraoperative magnetic resonance (MR) thermography. This can become an issue in patients with other implanted therapeutic devices such as pacemakers and vagal nerve stimulators due to concerns regarding increases in the specific absorption rate (SAR). This is a technical case report demonstrating a successfully and safely performed LiTT in a 1.5-T magnetic resonance imaging (MRI) in a patient with a pacemaker for mesial temporal sclerosis.

CLINICAL PRESENTATION

An 83-yr-old gentleman who had an implanted cardiac pacemaker presented with medically intractable epilepsy and was confirmed to have mesial temporal sclerosis on imaging. Video electroencephalography demonstrated concordant ipsilateral seizures and semiology. He underwent LiTT for ablation of the mesial temporal lobe. This was performed with the below described protocol with a cardiology nurse monitoring the patient's cardiac condition and a physicist monitoring SAR, and MR imaging quality without any adverse events.

CONCLUSION

This study reports on a protocol of cardiac and MR SAR to safely perform MR-guided LiTT in the setting of traditional pacemakers in patients who are not pacemaker dependent.

MRI of Patients with Cardiac Implantable Electronic Devices

Purpose of Review

The purpose of this review is to clarify the risks associated with MRI exams for patients with cardiac implantable electronic devices (CIEDs) and to provide information regarding the MRI examination protocol for patients with CIEDs.

Recent Findings

Several prospective studies evaluated the feasibility of MRI exams for patients with CIEDs and reported no adverse events. These studies suggest that by following a specific MRI examination protocol and monitoring both CIED parameters and the patient's symptoms, an MRI exam can be performed by appropriately trained personnel with an acceptable benefit-to-risk ratio.

Summary

Both MR unsafe and MR conditional CIEDs are commercially available, but there are no MR safe CIEDs. The potential risks faced by patients with CIEDs during an MRI exam are always present and warrant careful monitoring. Three magnetic fields in the MRI scanner interact with the device in ways that can damage the CIED or harm the patient. Due to safety concerns and out of an abundance of caution, the majority of MRI exams for patients with CIEDs are currently denied. However, when following a specific MRI exam protocol, these risks can be mitigated.