Journal: PLoS One
Authors: Tzirini M, Roth Y, Harmelech T, Zibman S, Pell GS, Kimiskidis VK, Tendler A, Zangen A, Samaras T.
Background:
The FDA cleared deep transcranial magnetic stimulation (Deep TMS) with the H7 coil for obsessive-compulsive disorder (OCD) treatment, following a double-blinded placebo-controlled multicenter trial. Two years later the FDA cleared TMS with the D-B80 coil on the basis of substantial equivalence.
Objective:
To investigate and compare the induced electric field characteristics of the two coils.
Methods:
The coils were placed at the treatment position for OCD over the prefrontal cortex of a head phantom, and the field distribution was measured. Additionally, numerical simulations were performed in eight Population Head Model repository models with two sets of conductivity values and three Virtual Population anatomical head models and their homogeneous versions.
Results:
The H7 was found to induce significantly higher maximal electric fields and to stimulate two to five times larger volumes in the brain. The rate of decay of electric field with distance is significantly slower for the H7 coil. The field at the scalp is 306% of the field at a 3 cm depth with the D-B80, and 155% with the H7 coil. The H7 induces significantly higher intensities in broader volumes within the brain and in specific brain regions known to be implicated in OCD compared to the D-B80. Significant field ≥ 80 V/m is induced by the
H7 (D-B80) in 15% (1%) of the dACC, 78% (29%) of the pre-SMA, 50% (20%) of the dlPFC, 30% (12%) of the OFC and 15% (1%) of the IFG.
Conclusions:
Considering the substantial differences between the two coils, the clinical efficacy in OCD should be tested and verified separately for each coil.
