Comparison of 3T and 7T MRI for the visualization of globus pallidus sub-segments

Abstract

The success of deep brain stimulation (DBS) targeting the internal globus pallidus (GPi) depends on the accuracy of electrode localization inside the GPi. In this study, we sought to compare visualization of the medial medullary lamina (MML) and accessory medullary lamina (AML) between proton density-weighted (PDW) and T2-weighted (T2W) sequences on 3T and 7T MRI scanners. Eleven healthy participants (five men and six women; age, 19–28 years; mean, 21.5) and one 61-year-old man were scanned using two-dimensional turbo spin-echo PDW and T2W sequences on 3T and 7T MRI scanners with a 32-channel receiver head coil and a single-channel transmission coil. Profiles of signal intensity were obtained from the pixel values of straight lines over the GP regions crossing the MML and AML. Contrast ratios (CRs) for GPe/MML, GPie/MML, GPie/AML, and GPii/AML were calculated. Qualitatively, 7T visualized both the MML and AML, whereas 3T visualized the MML less clearly and hardly depicted the AML. The T2W sequence at 7T yielded significantly higher CRs for GPie/MML, GPie/AML, and GPii/AML than the PDW sequence at 7T or 3T. The T2W sequence at 7T allows visualization of the internal structures of GPi segments with high signal intensity and contrast.

Past, Present, and Future of Deep Brain Stimulation: Hardware, Software, Imaging, Physiology and Novel Approaches

“…Finally, ultra-high-field imaging with 7T MRI has become increasingly popular due to its higher signal-to-noise ratio, spatial resolution, and structural contrast compared to 1.5T or 3T scanners ( 72 ). Ultra-high-field imaging may improve the visualization of the STN ( 73 ), the GPi ( 74 ), and thalamic nuclei ( Figure 3 ) ( 58 , 76 ). Currently, 7T MRI scanners are limited in availability to specialized imaging centers; however, as access to these scanners increases, more routine use in neurosurgical planning will become more common.…”

Effect of field strength on RF power deposition near conductive leads: A simulation study of SAR in DBS lead models during MRI at 1.5 T—10.5 T

“…There are strong incentives to do so: increasing the strength of the static magnetic field substantially increases the signal-to-noise ratio to visualize small structures previously unobservable on MRI scans. For example, MRI at 7 T can differentiate subsegments of the globus pallidus, a small brain nucleus that is the target of neuromodulation therapies, such as deep brain stimulation (DBS) [ 1 ].…”

A Comparison of 3 T and 7 T MRI for the Clinical Evaluation of Uveal Melanoma

“…Steensma et al, eg, showed that for imaging the prostate a higher SNR could be achieved using 7 T 32 . Similarly, Maruyama et al described a superior delineation of anatomical brain structures on 7 T, while Harteveld et al showed that small lesions in the arterial vessel walls could be visualized much better on 7 T than on 3 T 33,34 . However, unlike the aforementioned studies with up to 20 minutes per sequence, imaging the eye requires short acquisition times to limit eye‐motion related artifacts.…”

“…Given the increased signal intensity at 7 T, a better delineation at 7 T could be expected, as this was also observed in different studies of other anatomies. Steensma et al, eg, showed that for imaging the prostate a higher SNR could be achieved using 7 T. 32 Similarly, Maruyama et al described a superior delineation of anatomical brain structures on 7 T, while Harteveld et al showed that small lesions in the arterial vessel walls could be visualized much better on 7 T than on 3 T. 33 , 34 However, unlike the aforementioned studies with up to 20 minutes per sequence, imaging the eye requires short acquisition times to limit eye‐motion related artifacts. As a result, the image resolution was limited by the number of k‐space lines that could be acquired within 4 minutes.…”