Clement T Chow, Sriranga Kashyap, Brendan Santyr, Benson Yang, Jürgen Germann, Michael Colditz, Aaron Loh, Garene Matossian, Sarah Varughese, Nicole Owsicki, Asma Naheed, Jianwei Qiu, Afis Ajala, Michelle Paff, Simon J Graham, Kâmil Uludağ, Andres M Lozano, Alexandre Boutet
Optimized BOLD fMRI protocols effectively minimized susceptibility artifacts while preserving image quality, enabling reliable functional imaging in DBS patients-a timely advancement given the rise in DBS implants and introduction of directional stimulation systems.
BACKGROUND AND OBJECTIVES: Deep brain stimulation (DBS) is an established neuromodulation therapy for Parkinson disease and other neurological disorders. Active DBS-functional MRI (fMRI) enables visualization of circuit engagement and may provide objective biomarkers of therapeutic efficacy, yet susceptibility artifacts compromise data quality. The aim of this study was to develop optimized blood oxygenation-level-dependent (BOLD) fMRI protocols for DBS patients by adjusting operator-accessible parameters to mitigate susceptibility artifacts while preserving image quality.
METHODS: In vitro testing was performed on a 3-dimensional-printed anthropomorphic phantom simulating a patient with a 3T-conditional directional DBS system. We evaluated operator-adjustable parameters-spatial resolution, GeneRalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) acceleration, echo time, and simultaneous multislice acceleration-for their effects on artifact volume and temporal signal-to-noise ratio (tSNR). As exploratory analysis, optimized protocols were demonstrated in subthalamic nucleus-DBS patients (n = 3).
RESULTS: Higher spatial resolution and GRAPPA acceleration significantly reduced artifact volume (isotropic voxel size: 95% CI [1620.2, 2605.6], P < .001; GRAPPA: 95% CI [-1169.7, -749.0], P < .001) but also lowered tSNR (isotropic voxel size: 95% CI [62.5, 77.1], P < .001; GRAPPA: 95% CI [-17.3, -12.7], P < .001). Echo time adjustments had smaller yet significant effects on both artifact reduction (95% CI [127.3, 174.4], P < .001) and tSNR (95% CI [-1.3, -0.6], P < .001). Three optimized fMRI protocols were developed: (1) high spatial resolution, (2) balanced high resolution and whole-brain coverage (both with standard temporal resolution), and (3) high temporal resolution at standard spatial resolution (with reduced inner coil volume). Patients were scanned with the second protocol variant and total DBS artifact volume reduced by 45.1% ± 2.4% compared with clinical BOLD fMRI.
CONCLUSION: Optimized BOLD fMRI protocols effectively minimized susceptibility artifacts while preserving image quality, enabling reliable functional imaging in DBS patients-a timely advancement given the rise in DBS implants and introduction of directional stimulation systems.