Safe MR scanning of patients with metallic middle ear implants

Objective: To determine the MR scanning risk to patients with otologic implants. Design: We used a repeated-measures study with an additional control measure to assess two aspects of risk; i) movement of the device in the magnetic field, and ii) absorption of energy leading to local heating. We used an ex vivo test method that met with international standards. We measured the effects in a Philips Intera Achieva 3 Tesla MR scanner using a Sense Head 8 channel RF coil. Setting: University based magnetic resonance research facility Main outcome measures: Heating or displacement of the stapedectomy pistons Results: No evidence of displacement or heating was found. Conclusion: Complying with the ex vivo standard testing protocols, the Schuknecht and McGee wire pistons, (device product numbers 140106 and 140108 respectively) were found to be safe in a 3 T MR scanner. These conclusions can be extrapolated to the in vivo case

Screening Forms for Patients for MR Procedures and Individuals for the MR Environment

This appendix presents the screening forms that are to be filled by the patient prior to being scanned. Completion of these screening forms is also required for any person accompanying the patient into the magnet room. There are certain answers that will absolutely contraindicate the patient being scanned (e.g., if the patient has a cardiac pacemaker or ferromagnetic implant) while other questions are more designed to evaluate the patient’s tolerance (such as whether they are claustrophobic). Other questions (such as those relating to renal disease) will determine if it is safe to use a contrast agent and make the physician aware of the medical status of the patient.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145337/1/cpmix01.pd

Contrast‐Enhanced Renal MRA

The rapid growth of magnetic resonance imaging systems with enhanced gradient systems together with improved pulse sequences has improved the ability to image blood vessels with a spatial and temporal resolution similar to conventional X‐ray angiography. With patients who cannot undergo X‐ray angiography because they are contraindicated for iodinated contrast agents (having a creatinine level > 2.0), MRA (magnetic resonance angiography) has proven to be the modality of choice. Since the first demonstration of such contrast‐enhanced studies in the abdominal aorta, there have been continual improvements in methods due to improved hardware/software capabilities. This unit presents the MR protocols to image vascular morphology using contrast‐enhanced 3‐D‐MRA techniques. The pulse sequences described herein are based on the authors’ experience with a Siemens 1.5 T Vision and 1.5 T Sonata scanners, but are expected to be equally applicable to machines from other manufacturers.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145369/1/cpmia2801.pd

Diffusion Tensor Imaging

This unit provides step‐by‐step instructions on how to perform diffusion tensor imaging (DTI) in a clinical setting. A brief introduction on DTI techniques and current clinical applications is also presented. Additional technical details, practical considerations, and anticipated results are discussed in a commentary section.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145355/1/cpmia0604.pd

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.Radiolog