Reliability of targeting methods in TMS for depression: Beam F3 vs. 5.5 cm

Background: No consensus exists in the clinical transcranial magnetic stimulation (TMS) field as to the best method for targeting the left dorsolateral prefrontal cortex (DLPFC) for depression treatment. Two common targeting methods are the Beam F3 method and the 5.5 cm rule. Objective: Evaluate the anatomical reliability of technician-identified DLPFC targets and obtain consensus average brain and scalp MNI152 coordinates. Methods: Three trained TMS technicians performed repeated targeting using both the Beam F3 method and 5.5 cm rule in ten healthy subjects (n = 162). Average target locations were plotted on 7T structural MRIs to compare inter- and intra-rater reliability, respectively. Results: (1) Beam F3 inter- and intra-rater reliability was superior to 5.5 cm targeting (p = 0.0005 and 0.0035). (2) The average Beam F3 location was 2.6±1.0 cm anterolateral to the 5.5 cm method. Conclusions: Beam F3 targeting demonstrates greater precision and reliability than the 5.5 cm method and identifies a different anatomical target.