Article

Three-Dimensional Distribution of the Electric Field Induced in the Brain by Transcranial Magnetic Stimulation Using Figure-8 and Deep H-Coils

Tel Aviv University, Tell Afif, Tel Aviv, Israel
Journal of Clinical Neurophysiology (Impact Factor: 1.43). 03/2007; 24(1):31-8. DOI: 10.1097/WNP.0b013e31802fa393
Source: PubMed

ABSTRACT

The H-coils are a novel development in transcranial magnetic stimulation (TMS), designed to achieve effective stimulation of deep neuronal regions without inducing unbearable fields cortically, thus broadly expanding the potential feasibility of TMS for research and for treating various neurologic disorders. This study compared the field distribution of two H-coil versions, termed H1 and H2, and of a standard figure-of-eight coil. Three-dimensional electrical field distributions of the H1 and H2-coils, designed for effective stimulation of prefrontal regions, and of a standard figure-8 coil, were measured in a head model filled with physiologic saline solution. With stimulator output at 120% of the hand motor threshold, suprathreshold field is induced by the H1-coil at lateral and medial frontal regions at depths of up to 4 to 5 cm, and by the H2-coil at medial prefrontal regions up to 2 to 3 cm, and at lateral frontal regions up to 5 to 6 cm. The figure-8 coil induced suprathreshold field focally under the coil's central segment, at depths of up to 1.5 cm. The ability of the H-coils to stimulate effectively deeper neuronal structures is obtained at the cost of a wider electrical field distribution in the brain. However, the H-coils enable simultaneous stimulation of several brain regions, whereas the depth penetration in each region can be controlled either by adjusting the stimulator output, and/or by varying the distance between various coil elements and the skull.

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Available from: Yiftach Roth, Sep 29, 2015
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    • "This limitation led to the newly developed deep TMS (deepTMS) H-coil [33] which is able to safely modulate cortical excitability of deeper neural circuits [32] [33]. Similar to standard TMS, these deepTMS techniques target hypoactivity within the DLPFC [32] [33] [47] while stimulating deeper cortical structures within the frontoparietal-limbic circuitry in treating depressive disorders [45] [46] [48] [49]. Therefore, delivery of repetitive TMS (rTMS) to the DLPFC targets the same compromised circuitry which correlates with impaired attentional control in MDD [6] [8] [10]. "
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    • "For dTMS sessions we used Brainsway's H1 coil deep TMS System (Brainsway, Har Hotzvim, Jerusalem, Israel). The H1 coil is designed to elicit neuronal activation in medial and lateral prefrontal regions, including the orbitofrontal cortex, with a preference for the left hemisphere (Roth et al., 2007). H1 coils were positioned over patient's scalp. "
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    Full-text · Article · Nov 2014 · Journal of Affective Disorders
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    • "A recently developed variant of TMS is deep TMS. Deep TMS coils minimize the accumulation of electrical charge on the surface of the brain and maximize the electrical field deep in the brain by the summation of separate fields projected into the skull from several different points around its periphery (Roth, Amir, Levkovitz &amp; Zangen, 2007). A review comparing the efficacy and tolerability of deepTMS, rTMS and ECT in drug-free patients with pharmaco-resistant unipolar depression confirmed the superior efficacy of ECT as the most effective treatment option after 4 weeks of therapy. "
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