Commercial TMS Coils

Version 1.01 (4-Jan-16)

Copyright © 1994-2016
Samuel M. Goldwasser
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Here is a summary of several commercial figure-8 coils, as well as the author's Sam #13 (built) and Sam #14 (proposed):

    Mfr/Model      #Turns  ID     Mean      OD    Overlap  Wire Size   Angle
-------------------------------------------------------------------------------
 Magstim 70 mm       9x2 5.2 cm  7.0 cm   8.8 cm  0.0 cm 1x7 mm          0 deg
 Medtronic MC-B70   10x2 2.4 cm  6.6 cm  10.8 cm  4.2 cm 3.5 mm (#8)  34.5 deg
 MagVenture CoolB70 11x2 2.3 cm  5.95 cm  9.6 cm ?3.6 cm 3x12 mm?     30.0 deg
 MagVenture MC-B70  10x2 2.7 cm  6.2 cm   9.7 cm ?3.5 cm 3x6 mm?      30.0 deg
 Sam #13             8+9 3.13 cm 5.72 cm  8.26 cm 2.5 cm 2.6 mm (#10) 30.0 deg
 Sam #14            10x2 2.9 cm  6.8 cm  10.5 cm  3.4 cm 3.18 mm Tube 30.0 deg

Calculations show the overlapped configuration to have a slightly higher peak field and dB/dt for the same inductance. Testing with a Gauss probe at low currents results in slightly more than 1 G/A at 2 cm from the coil surface at the center position for Sam #13.

Commercial TMS Coils

The following are specifications and design info obtained from various sources including the manufacturers' Web sites and research papers. For descriptions of the authors coils, see Sam's TMS Coils.

Medtronic MC-B70 double coil

A photo and two X-ray pictures of the Magstim figure- of-eight coil are shown in the paper: Axel Thielschera and Thomas Kammerb, "Electric field properties of two commercial figure-8 coils in TMS: calculation of focality and efficiency", Clin Neurophysiol 2004 Jul;115(7):1697-708.

Coil Winding Data

    Inner diameter 24 mm
    Outer diameter 108 mm
    Wire cross-section: 3.5 mm
    Number of windings 2 x 10
    Thickness of plastic chassis between coils and head 2 mm.

In the coil center the windings of the two wings overlap. Next to the overlap, the windings of the left and right wings are bent by an angle of 18.5 and 16 degrees, respectively.

MagVenture Cool-B70 Butterfly

Electrical and magnetic properties similar to the MCF-B70. Designed for demanding stimulation protocols requiring a very high number of stimuli. Desined with a slightly bent surface for best possible skull contact. Equipped with trigger button to support clinical operation. Built in EPV timer and counter (5 years or 18 million EPV, which ever comes first). Number of pulses remaining = 17,472,068.

Mechanical Properties:

    Weight of transducer head: 2.9 kg.
    Cable length: 1.3 m.
    Dimensions of transducer head: 180 x 116 x 45/64 mm.
    Angulated: 150 degrees.

Coil Winding Data:

    Inner diameter: 23 mm.
    Outer diameter: 96 mm.
    Winding height: 12 mm.
    Number of windings: 2 x 11.

Magnetic and Electrical Properties:

    Max initial dB/dt: 28 kT/s near the coil surface.
    Active pulse width: 280 µs (Biphasic).

Performance:

    Number of stimulations, before warm-up at ambient temperature of 20 °C
     wotj output of 75% of maximum at 2 pps: >20.000 pulses.

    Number of stimulations, before warm-up at ambient temperature of 20 °C
     with protocol: 60 trains at 50 pulses/train at 10 pps with inter-train
     interval of 25 s and output = 75%: >10.000 pulses.

MagVenture MC-B70 Butterfly

Suitable coil for focused stimulation. The coil is produced with a slight bend to closely follow the shape of the head. Equipped with trigger button to support clinical operation.

Mechanical Properties:

    Weight of transducer head: 1.1 kg.
    Cable length: 1,7 m.
    Dimensions of transducer head: 169 x 112 x 16/33 mm.

Coil Winding Data:

    Inner diameter: 27mm.
    Outer diameter: 97mm.
    Winding height: 6mm.
    Number of windings: 2 x 10.

Magnetic and Electrical Properties:

    Max initial dB/dt: 31 kT/s near the coil surface.
    Active pulse width: 280 us (Biphasic).

Performance

    Number of stimulations before warm-up at ambient temperature at 20 °C
     with mean output 75% of maximum at 1 pps: 400 pulses.

Ordering Number:

    9016E0564.

Magventure MC-B35 Butterfly

Mechanical Properties:

    Weight of transducer head: 600 g.
    Cable length: 1.5 m.
    Dimensions of transducer head: 103 x 55 x 18 mm.

Coil Winding Data:

    Inner diameter: 24 mm.
    Outer diameter: 47 mm.
    Winding height: 9 mm.
    Number of windings: 2 x (3X4).

Magnetic and Electrical Properties:

    Max initial dB/dt: 50 kT/s near the coil surface.
    Active pulse width: 280 µs (Biphasic).

Performance:

    Number of stimulations before warm-up at ambient temperature at 20 °C
     with mean output 75% of maximum at 1 pps: 75 pulses.

Ordering Number:

    9016E0671

Magventure C-B60 Butterfly

Suitable coil for focused stimulations. Equipped with power control and trigger button to support clinical operation.

Mechanical Properties:

    Weight of transducer head: 700 g.
    Cable length: 1.7 m.
    Dimensions of transducer head: 165 x 85 x 19 mm.

Coil Winding Data:

    Inner diameter: 35 mm.
    Outer diameter: 75 mm.
    Winding height: 11 mm.
    Number of windings: 2 x (2 x 5).

Magnetic and Electrical Properties:

    Max initial dB/dt: 35 kT/s near the coil surface.
    Active pulse width: 280 µs (Biphasic).

Performance:

    Number of stimulations before warm-up at ambient temperature at 20 °C
     with mean output of 75% of maximum at 1 pps: 350 pulses.

Ordering Number:

    9016E0482.

Magventure D-B80 Butterfly

Opened butterfly design for powerful stimulation. The coil is suitable for deep stimulation. The coil is slightly bend to closely follow curved shapes. Equipped with trigger button to support clinical operation.

Mechanical Properties: Weight of transducer head: 900 g. Cable length: 1.7m. Angle: 120 degrees. Coil Winding Data: Inner diameter: 67 mm. Outer diameter: 95 mm. Winding height: 12 mm. Number of windings: 2 x (3+4). Magnetic and Electrical Properties: Max initial dB/dt: 31 kT/s near the coil surface. Active pulse width: 280 µs (Biphasic). Performance: Number of stimulations, before warm-up at ambient temperature of 20 °C with mean output of 75% of maximum at 1 pps: 500 pulses. Ordering Number: 9016E0431.

Magventure MC-B65-HO Butterfly

The coil handle is placed orthogonal on the cable.

Mechanical Properties:

    Weight of transducer head: 0.7 kg.
    Cable length: 
        2 m (B65-HO-2).
        8 m (B65-HO-8).
    Dimensions of transducer head: 162 x 85 x 22 mm.

Coil Winding Data:

    Inner diameter; 35 mm.
    Outer diameter: 75 mm.
    Winding height: 11 mm.
    Number of windings: 2x (2 x 5).

Magnetic and Electrical Properties:

    Max initial dB/dt: 25 kT/s near the coil surface.
    Active pulse width 280 µs (Biphasic).

Performance:

    Number of stimulations before warm-up at ambient temperature of 20 °C
     with mean output 75% of maximum at 1 pps: 350 pulses.

Ordering Number:

    9016E0462 (2m).
    9016E0472 (8m).

Magventure MCF-B65 Butterfly

The Coil is designed for demanding stimulation protocols, requiring a high number of stimuli without the need for external cooling. Equipped with trigger button to support clinical operation.

Mechanical Properties:

    Weight of transducer head: 1.5 kg.
    Cable length: 2 m.
    Dimensions of transducer head: 174 x 94 x 53 mm.

Coil Winding Data:

    Inner diameter: 35 mm.
    Outer diameter: 75 mm.
    Winding height: 12 mm.
    Number of windings: 2x (2 x 5).

Magnetic and Electrical Properties:

    Max initial dB/dt: 32 kT/s near the coil surface.
    Active pulse width: 280 µs (Biphasic).

Performance:

    Number of stimulations before warm-up at ambient temperature of 20 °C
     with mean output of 75% of maximum at 1 pps: 2000 pulses.

Ordering Number:

    9016E0423.

Magventure MCF-B70 Butterfly Coil

Electrical and magnetic properties similar to the MC-B70. Designed for demanding stimulation protocols requiring a high number of stimuli without the need for external cooling. Designed with a slightly bend surface for best possible skull contact. Large ergonomic handle and equipped with trigger button to support clinical operation.

Mechanical Properties

    Weight of transducer head: 2.5 kg.
    Cable length: 1.3 m.
    Angle: 150 degrees.
    Dimensions of transducer head: 180 x 116 x 46/64 mm.

Coil Winding Data:

    Inner diameter: 23 mm.
    Outer diameter: 96 mm.
    Winding height: 12 mm.
    Number of windings: 2 x 11.

Magnetic and Electrical Properties:

    Max initial dB/dt: 28 kT/s near the coil surface.
    Active pulse width 280 µs (Biphasic).

Performance

    Number of stimulations before warm-up at ambient temperature of 20 °C
     with mean output of 75% of maximum at 1 pps: 5500 pulses.

    Protocol: 60 trains at 50 pulses/train at 10 pps with inter-train interval
     of 25 s with output of 75%.  (Total number of stimulations = 3000).
     One protocol can be performed without overheating the coil.

    Minimum cooling time between protocols: 2.5 hours at 20 °C or
     1 hour at 7 °C.

Ordering Number:

    9016E0401.

Magventure Cool-B35 Butterfly

Electrical and magnetic properties similar to the MC-B35. Suitable for focused stimulation of peripheral nerves and muscles. Large ergonomic handle. Equipped with trigger button to support clinical operation. Built in EPV timer and counter (5 years or 18 mill. EPV, whichever comes first)

Mechanical Properties:

    Weight of transducer head: 1.2 kg.
    Cable length: 1.3 m.
    Dimensions of transducer head: 113x65x42 mm.

Coil Winding Data:

    Inner diameter: 10 mm.
    Outer diameter: 46 mm.
    Winding height: 15 mm.

Magnetic and Electrical Properties:

    Max initial dB/dt: 50 kT/s near the coil surface.
    Active pulse width: 280 µs (Biphasic).

Performance:

    Number of stimulations before warm-up at ambient temperature of 20 °C
     with mean output of 100% of maximum at 1 pps: 150 pulses.

    Number of stimulations before warm-up at ambient temperature of 20 °C
     with mean output of 75% of maximum at 1 pps: 300 pulses.

Ordering Number:

    9016E0681.

Magventure Cool-B65 Butterfly

Designed for demanding stimulation protocols requiring a very high number of stimuli. Optimized for high repetition rates and long pulse trains. Cooled from an external Cooler Unit. Equipped with trigger button to support clinical operation. Built in EPV timer and counter (5 years or 18 million EPV, whichever comes first).

Mechanical Properties:

    Weight of transducer head: 1.7 kg.
    Cable length: 1.3 m.
    Dimensions of transducer head: 174 x 94 x 41 mm.

Coil Winding Data:

    Inner diameter: 35 mm.
    Outer diameter: 75 mm.
    Winding height: 12 mm.
    Number of windings: 2 x (2 x 5).

Magnetic and Electrical Properties:

    Max initial dB/dt: 36 kT/s near the coil surface.
    Active pulse width 280 µs (Biphasic).

Performance:

    Number of stimulations before warm-up at ambient temperature of 20 °C
     with mean output of 75% of maximum at 2 pps: >20.000 pulses.

    Number of stimulations, before warm-up at ambient temperature of 20 °C
     with protocol: 60 trains at 50 pulses/train at 10 pps with inter-train
     interval or 25 s at output of 75%: >10.000 pulses.

Ordering Number:

    9016E0491.

Magventure Cool D-B80 Butterfly

Electrical and magnetic properties like the D-B80. Suitable for deep stimulation. Designed for demanding stimulation protocols requiring a very high number of stimuli. Equipped with trigger button to support clinical operation. Built in EPV timer and counter (5 years or 18 million EPV, which ever comes first).

Mechanical Properties:

    Weight of transducer head: 1.8 kg.
    Cable length: 1.3 m.
    Dimensions of transducer head: 
        Diameter: 2 x 110mm.
        Thickness 30mm.
    Angle: 120 degrees.

Coil Winding Data:

    Inner diameter: 67 mm.
    Outer diameter: 95 mm.
    Winding height: 12 mm.
    Number of windings: 2 x (3+4).

Magnetic and Electrical Properties:

    Max initial dB/dt: 31 kT/s near the coil surface.
    Active pulse width 280 µs (Biphasic).

Performance:

    Number of stimulations before warm-up at ambient temperature of 20 °C
     with output of 75% of maximum at 2 pps: >20.000 pulses.

    Number of stimulations before warm-up at ambient temperature of 20 °C
     with output of 75%, protocol: 60 trains at 50 pulses/train at 10 pps
     and inter-train interval of 25 sec: >10.000 pulses.

Ordering Number:

    9016E0531.

Magstim 70 mm Double Coil

A photo and two X-ray pictures of the Magstim figure- of-eight coil are shown in the paper: Axel Thielschera and Thomas Kammerb, "Electric field properties of two commercial figure-8 coils in TMS: calculation of focality and efficiency", Clin Neurophysiol 2004 Jul;115(7):1697-708.

Coil Winding Data

    Inner diameter 52 mm
    Outer diameter 88 mm
    Winding height 7 mm
    Wire cross-section: 7x1 mm
    Number of windings 2 x 9
    Thickness of plastic chassis between coils and head 3 mm.