Background Effective deep brain stimulation (DBS) requires precise visualisation of the target on magnetic resonance imaging (MRI). However, on clinical 3 Tesla (T) MRI these targets are often imperfectly delineated, introducing potential error. Higher magnetic field strength e.g. 7T MRI ought to improve visualisation via resolution or contrast. Our aim was to appraise current evidence for proposed improvements with 7T MRI for DBS implantation. Specifically, we wanted to consider evidence for improvements in target visualisation, the imaging sequences that can leverage improvements, and how better MRI quality translated into clinical outcomes. Methods A scoping review was performed across multiple databases (PubMed and EMBASE). Search criteria included the terms ('7 Tesla' OR '7T') AND ('deep brain stimulation' OR 'thalamus' OR 'basal ganglia' OR 'globus pallidus' OR 'zona incerta' OR 'pedunculopontine' OR 'subthalamic nucleus'). Studies were selected based on target visualisation, sequence appraisal, or clinical application. Quantitative data were extracted for meta-analysis. Results 66 papers were identified. Target visualisation was improved with better signal- and contrast-to-noise ratio compared to 1.5T or 3T MRI, while manual segmentations of the subthalamic nucleus at 7T showed high inter-rater reliability (Dice = 0.75, 10 studies). Gradient echo sequences and quantitative susceptibility mapping offered the best demarcation and tissue contrast of basal ganglia structures. Clinical studies have demonstrating promising results with novel targets and targeting strategies, but not when simply implementing 7T MRI data in existing targeting approaches. Conclusions 7T MRI offers objectively better data quality that translates to better delineation of DBS targets. However, to translate these benefits into improved clinical outcomes will require a development of DBS planning and targeting approaches rather than just utilising current practices. In the future, there is significant potential for establishing larger multi-centre series, exploring new sequences, and developing novel clinical trials to test for improvements in patient outcomes.
Ishihara et al. (Tue,) studied this question.