The current state of postoperative imaging in the presence of deep brain stimulation electrodes

Abstract

For more than a decade, medically refractory movement disorders have been treated with deep brain stimulation (DBS) devices. Bilateral DBS of the subthalamic nucleus (STN), globus pallidus, and thalamus have been effective in reducing the complications of medications in later-stage movement disorder patients. However, the effectiveness of the DBS device is highly dependent on the proper radiologic and electrophysiological identification of DBS target structures and the accurate placement of the DBS electrodes. The reasons for suboptimal results from DBS surgery could be related to several factors such as patient selection (preoperative), precision of DBS electrode placement (intraoperative), and inadequate device programming and follow-up (postoperative). 1 It should be mentioned from the outset that, regardless of the target, the issues of postoperative MRI in the presence of electrodes hold true.Limited clinical improvement from DBS therapy may result from misplaced electrodes during the intraoperative procedure. Magnetic resonance imaging (MRI) of DBS electrodes is the preferred method for confirming the anatomical location of electrodes given the amount of detail obtained. Recently, computerized topography (CT) has been used for electrode localization by fusing the postoperative CT with the preoperative MRI. This method could introduce more error given the fusion process required (eg, brain shift, CT air pockets). There is an implicit need for the localization of DBS electrodes with a postoperative MRI, and no amount of experienced DBS programming can compensate for a poorly placed electrode. 1 Furthermore, a CT scan cannot replace invaluable MRI scan sequences that are used for diagnostic purposes (outside electrode localization).However, the current restrictions on the postoperative MRI of electrodes has resulted in many centers opting out of the procedure. Importantly, although the potential danger imposed by MRI scanning in the presence of electrodes should not be disregarded, the fear of such procedures should not impact patient care. The current viewpoint will assume that MRI scanning is being performed with both the leads and implantable pulse generator in place. Regardless of the patient, treating neurologist, or the implantation technique, postoperative MRI scanning is invaluable for proper electrode placement verification and diagnostic applications. Specific Absorption RateIn 1979, the concept of specific absorption rate (SAR) was introduced by the National Council on Radiation Protection and Measurements for measuring the rate of radiofrequency (RF) energy absorbed by the body. SAR is defined as the mass normalized rate at which RF power is coupled to biological tissue. 2 SAR is measured in units of watts per kilogram (W/kg). 2 The objective of calculating SAR is to limit the rise in body temperature as a result of RF deposition during the MRI procedure. During the MRI procedure, the patient's body temperature is not easy to detect, so SAR is used to control the potential temperature increases. 2 ...

Understanding the Effects and Adverse Reactions of Deep Brain Stimulation: Is It Time for a Paradigm Shift Toward a Focus on Heterogenous Biophysical Tissue Properties Instead of Electrode Design Only?

“…Owing to its anatomical intricacy, MRI of the subcortex only lends support by using high-field MRI (3 T or higher). Hence, because of imprecise electrode placement (e.g., Gilmore et al, 2017 ) due to the use of preoperative low field structural MRI images, electrode placement planning may lead to unknown electrical fields in brain tissue and hamper an optimal clinical outcome. Meanwhile, computational models have supported the advance of DBS technology (e.g., Butson et al, 2006 ; Miocinovic et al, 2006 ; Gunalan et al, 2017 ).…”

Optimizing the trajectory of deep brain stimulation leads reduces RF heating during MRI at 3 T: Characteristics and clinical translation

“…Deep brain stimulation (DBS) is a neurosurgical procedure where electrical stimulation is delivered to specific subcortical targets in the brain, providing therapeutic benefits to patients with movement disorders and other neurological diseases [ 1 ]–[ 4 ]. For patients with implanted DBS systems, magnetic resonance imaging (MRI) is highly useful, allowing for postoperative monitoring, target verification, and localization of the electrodes [ 5 ], [ 6 ], along with elucidating the functional effects of stimulation on affected brain networks [ 7 ]. As the field of DBS therapy advances, the need for application of higher field strength MRI (i.e., 3 T and above) for improved contrast-to-noise ratio is increasingly imperative [ 8 ], [ 9 ].…”

Day one postoperative MRI findings following electrode placement for deep brain stimulation: analysis of a large case series

“…The existing postoperative DBS MRI literature has largely focused on evaluation of procedure safety ( 19 – 22 ), electrode mapping and clinical correlates ( 7 , 23 , 24 ), functional connectivity ( 25 ), electrode artifact ( 26 , 27 ), and imaging findings such as symptomatic hemorrhage and edema ( 28 – 33 ). To date, there has been no comprehensive evaluation of postoperative radiographic abnormalities using MRI nor comparison of sequences best suited for detecting these phenomena.…”

“…Over time, a number of studies have demonstrated that postoperative MRI can be safely performed in DBS patients at 1.5 T and 3.0 T if specific, restricted conditions are met during scanning (14)(15)(16)(17)(18). These promising safety data have allowed for the incorporation and study of postoperative MRI in the care of DBS patients (19)(20)(21)(22).…”