Imaging for deep brain stimulation: The zona incerta at 7 Tesla

Abstract

AIM:To evaluate different promising magnetic resonance imaging (MRI) methods at 7.0 Tesla (T) for the pre-stereotactic visualization of the zona incerta (ZI). METHODS:Two neuroradiologists qualitatively and quantitatively examined T2-turbo spin-echo (T2-TSE), T1-weighted gradient-echo, as well as FLASH2D-T2Star and susceptibility-weighted imaging (SWI) for the visualization of the ZI at 7.0 T MRI. Delineation and image quality for the ZI were independently examined using a 6-scale grading system. Inter-rater reliability using Cohen's kappa coefficient (κ ) were assessed. Contrast-tonoise ratios (CNR), and signal-to-noise ratios (SNR) for the ZI were calculated for all sequences. Differences in delineation, SNR, and CNR between the sequences were statistically assessed using a paired t -test. For the anatomic validation the coronal FLASH2D-T2Star images were co-registered with a stereotactic atlas (Schaltenbrand-Wahren). RESULTS:The rostral part of the ZI (rZI) could easily be identified and was best and reliably visualized in the coronal FLASH2D-T2Star images. The caudal part was not definable in any of the sequences. No major artifacts in the rZI were observed in any of the scans. FLASH2D-T2Star and SWI imaging offered significant higher CNR values for the rZI compared to T2-TSE images (P > 0.05). The co-registration of the coronal FLASH2D-T2Star images with the stereotactic atlas schema (Schaltenbrand-Wahren) confirmed the correct localization of the ZI in all cases.CONCLUSION: FLASH2D-T2Star imaging (particularly coronal view) provides the reliable and currently optimal visualization of the rZI at 7.0 T. These results can facilitate a better and more precise targeting of the caudal part of the ZI than ever before.

Interleaving Stimulation in Parkinson’s Disease, Tremor, and Dystonia

“…In addition, inconsistencies in the efficacy and adverse effects of ZI stimulation exist and likely reflect the inability to directly target the ZI resulting in variability of contact placement [20-23, 31, 32]. Methods for visualization of the rZI allowing direct stereotactic targeting have recently been reported [33, 34]. In addition, intraoperative microelectrode recordings may aide in direct targeting of the ZI as this region reveals a low amplitude background and a sparse cell density, as well as a lack of proprioceptive responses, which help to distinguish it from surrounding areas [24].…”

Direct visualization and characterization of the human zona incerta and surrounding structures

“…Many explorations of the deep brain at ultra-high field (7-Tesla; 7 T) exploited T2w tissue properties enabling visualization of many deep brain nuclei with improved resolution and signal-to-noise ratio (SNR) including the RN, substantia nigra, and STN (Keuken et al, 2013;Plantinga et al, 2018;Schäfer et al, 2012), known to be rich in iron (Haacke et al, 2005;Luigi, Youdim, Riederer, Connor, & Crichton, 2004). Paralleling these successes, previous attempts at direct visualization of the ZI have focused on the use of T2w contrast, with purported identification of the rZI, but not the cZI (Kerl et al, 2013). In this study, we report that, by employing high-resolution longitudinal (T1) mapping at 7 T, robust visualization of the ZI and surrounding WM structures is possible in vivo along the entire rostrocaudal axis, allowing comprehensive anatomical characterization of this previously obscure deep brain region.…”

Direct visualization and characterization of the human zona incerta and surrounding structures

“…The ZI has proven to be elusive to visualization using T2w contrast. In one study at 7T, using a T2w 423 sequence, the rostral but not the cZI was reported as visible (Kerl et al, 2013), which we demonstrate is 424 actually the fasciculus lenticularis ( Figure 2). As a result, protocols for stereotactic targeting of the cZI have 425 relied on the relative visibility of the surrounding RN and STN, from which the location of the stereotactic 426 target within the PSA could be indirectly inferred.…”

“…Many explorations of the deep brain at 7T have exploited T2w tissue 94 properties enabling visualization of many deep brain nuclei with improved resolution and signal-to-noise 95 ratio (SNR) including the RN, substantia nigra, and STN (Keuken et al, 2013;Plantinga et al, 2018;Schäfer 96 et al, 2012), known to be rich in iron (Haacke et al, 2005;Luigi Zecca et al, 2004). Paralleling these 97 successes, previous attempts at direct visualization of the ZI have focused on the use of T2w contrast, with 98 purported identification of the rZI, but not the cZI (Kerl et al, 2013). In this study, we report that, by 99 employing high-resolution longitudinal (T1) mapping at 7T, robust visualization of the ZI and surrounding 100 WM structures is possible in vivo along the entire rostrocaudal axis, allowing comprehensive anatomical 101 characterization of this previously obscure deep brain region.…”