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Variability and repeatability of personalized rTMS targeting methods combining repeated fMRI scans and electric field
He Wang1, Jingna Jin1, Xin Zhang2
1Tianjin Key Laboratory of Neuromodulation and Neurorepair, Institute of Biomedical Engineering, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin 300192, PR China.
Background:
Despite growing interest in personalized rTMS targeting methods using fMRI, there is a notable lack of studies examining the variability and repeatability of these techniques.
Objective:
This study investigates the variability and repeatability of personalized rTMS target localization methods, as well as their impact on cortical electric field distribution, using multiple repeated resting-state functional magnetic resonance imaging (rs-fMRI) scans. The goal is to provide a reliable approach for personalizing and precisely targeting rTMS to enhance its clinical efficacy.
Methods:
A total of 19 healthy subjects participated in the study. Each underwent five repeated rs-fMRI scans (with two runs per session, resulting in 10 runs in total). Five established personalized targeting methods were used to calculate the coordinates of single-run and multiple-run targets. The variability and repeatability of the targets were quantified as the mean Euclidean distance between targets and the probability of locating the same coordinates across scans. These were compared for both single-run and multiple-run targets. Additionally, the electric field distribution for each participant was calculated at various coordinates in individual space.
Results:
Variability in the single-run target ranged from 8.75 mm to 31.48 mm across the five personalized targeting methods. The repeatability for these single-run targets varied between 0.12% and 5.1%. Simulation results revealed that variability in single-run targeting significantly impacted cortical electric field distribution (p<0.0001). In contrast, the variability of multiple-run targets was significantly reduced (p<0.0001), ranging from 1.44 mm to 13.5 mm, and the repeatability improved significantly (p<0.0001), spanning 4.2% to 78.6%. Furthermore, multiple-run targets demonstrated greater consistency in cortical electric field distribution across the five targeting methods.
Conclusion:
These findings indicate that personalized rTMS targeting methods based on a single run of rs-fMRI data introduce inherent variability. Averaging data across multiple rs-fMRI scans yields more reliable and stable rTMS targeting, producing a more consistent electric field at the targeted cortical area.
