Related Experiment Video
Updated: Aug 7, 2026
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Conventional Repetitive Transcranial Magnetic Stimulation for Depression: A Step-by-Step Protocol
Published on: November 21, 2025
Depression Improvement Correlates With Lower TMS Intensity in a Randomized Trial With Real-Time E-Field Modeling
Prem Ganesh1, Hakjoo Kim1,2, Jamie Kweon1
1Brain Stimulation Mechanisms Laboratory, Division of Depression and Anxiety Disorders, McLean Hospital, Belmont, Massachusetts, USA.
Human Brain Mapping
|August 4, 2026
Summary
Individual brain anatomy significantly impacts transcranial magnetic stimulation (TMS) dosing for depression. Real-time electric-field (E-Field) modeling offers more precise TMS delivery than standard methods, improving treatment accuracy.
Area of Science:
- Neuroscience
- Psychiatry
- Biomedical Engineering
Background:
- Current transcranial magnetic stimulation (TMS) for depression relies on fixed-percentage motor threshold (rMT) dosing, typically 120% rMT.
- Individual anatomical differences can lead to significant variations in cortical electric-field (E-Field) strength, potentially affecting treatment efficacy.
Purpose of the Study:
- To investigate the variability of TMS E-Field strengths due to individual anatomy.
- To assess the precision of real-time E-Field-guided dosing compared to conventional fixed-percentage dosing.
- To examine the relationship between E-Field parameters and clinical outcomes in major depressive disorder (MDD) patients.
Main Methods:
- Prospective study involving 28 MDD subjects receiving accelerated intermittent theta-burst stimulation (aTBS).
- Real-time E-Field modeling was used to guide TMS intensity, targeting M1-equivalent stimulation at the left dorsolateral prefrontal cortex (DLPFC).
- Dosing strategies were compared based on precision in approximating motor-equivalent E-Field delivery and correlation with symptom reduction (QIDS-SR16 scores).
Main Results:
- Required %rMT for motor-equivalent DLPFC E-Field varied widely (49.7%-150.4%), with over half of subjects needing <100% rMT.
- Real-time E-Field-guided dosing demonstrated 48.1% greater precision in delivering motor-equivalent E-Fields compared to the conventional 120% rMT approach (p=0.021).
- Higher absolute DLPFC E-Field strength and a higher DLPFC to M1 E-Field ratio were significantly correlated with less symptom reduction (ρ=-0.49, p=0.008).
Conclusions:
- Fixed-percentage TMS dosing exhibits substantial inter-individual variability in cortical E-Field delivery.
- Real-time E-Field guidance provides more precise and individualized TMS dosing than conventional methods.
- The findings challenge the assumption that higher stimulation intensity equates to better clinical outcomes, suggesting lower E-field intensities may be more effective for DLPFC stimulation in MDD.
