![]() In this issue of Radiology, Boutet and colleagues ( 4) add to our knowledge base of the potential for adverse events in patients with DBS. Thus, there is strong interest in research that explores the safety and risks associated with MRI performed outside of the labeling guidelines of DBS manufacturers. The context of performing MRI studies for research purposes becomes even more challenging, where risk tolerance is substantially lower and informed consent requires clear directives on said risks. This leads to concern that patients with DBS are being denied MRI studies based on what may be an extreme interpretation of the associated risks. A 2009 study ( 3) found that a substantial fraction of the National Parkinson’s Foundation’s Centers of Excellence did not perform MRI in patients with DBS. Navigating this amorphous landscape is challenging, and practice across medical centers is variable. Indeed, the benefit to the patient of performing an MRI examination can be substantial and warrant the assumption of some risk. However, the risk of not performing imaging or of using a substandard alternate imaging modality must also be considered. Risks include both the physical risk to the patient and the legal risk associated with performing imaging outside of labeling guidelines. Clinicians must balance the risks and benefits associated with performing the preferred MRI study in a patient with DBS. B 1+rms values up to 2.0 μT are permitted with these systems, but the requirement for 1.5-T horizontal closed-bore MRI remains in place.Ĭurrent circumstances make it difficult for clinicians and researchers to define the risk of MRI outside of manufacturer specifications. For more recent DBS models, labeling from Medtronic (Minneapolis, Minn) has permitted body coil transmission and higher radiofrequency exposure provided the root-mean-square value of the MRI effective component of the radiofrequency magnetic field (B 1), or B 1+rms, rather than just SAR are reported with the MRI systems. Furthermore, the restriction of MRI recommendations to only 1.5-T systems may simply relate to a lack of testing by the implant manufacturer rather than an inherent risk. The lack of events raises the question of an excessive margin of safety in current labeling. Other research groups have reported on MRI of patients with DBS outside of manufacturer guidelines without adverse events ( 2). Indeed, there have been no adverse events reported when manufacturer guidelines were followed. The labeling requirements reflected scenarios where the potential for substantial heating was demonstrated in phantom testing. Manufacturer guidelines at the time were extremely restrictive, limiting scanning to only horizontal bore 1.5-T systems using a transmit-receive head coil and with a specific absorption rate (SAR) limit of 0.1 W/kg. This event set the tone of risk avoidance in MRI of patients with DBS systems. They described a hemorrhagic event that produced a permanent neurologic injury and concluded that manufacturer guidelines should be carefully followed to avoid catastrophic incidents. ![]() The most notable adverse event was documented by Henderson et al ( 1). The safety of such imaging procedures, however, remains controversial. ![]() After implantation of the DBS system, patients may require MRI to evaluate a wide range of disease processes that may or may not be related to their movement disorder. The demand for MRI of patients with implanted deep brain stimulation (DBS) systems continues to grow. ![]()
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