TMS equipment is a device that uses high-voltage energy storage capacitors to instantaneously discharge magnetic field coils to generate pulsed magnetic fields that act on the nervous system to generate stimulation. Common TMS equipment currently used for treatment mainly includes three parts: stimulator, stimulation coil, and cooling system.

Stimulator

The host circuit of transcranial magnetic stimulation instrument is composed of charging circuit, energy storage capacitor, pulse control circuit and silicon controlled switch. TMS equipment generates high-intensity and fast time-varying pulsed magnetic field, which is mainly discharged to the stimulation coil after charging by high-voltage energy storage capacitor. The time-varying magnetic field generated by the coil can reach tens of thousands of Tesla/s (tens of kT/s).

Stimulation Coil

Magnetic field stimulation coil is a key component of TMS. The intensity, depth of action, stimulation range and focusing characteristics of magnetic stimulation are closely related to the stimulation coil, involving the geometric shape, size, current direction, cooling mode, thickness and weight of the coil, hollow coil and iron core coil. The coil designed for scientific research requires a true stimulation coil with the same shape and weight as the sham stimulation coil, so as to meet the needs of random double-blind control.

Figure 8 Coil

Figure 8 coil is to place two circular coils side by side on a plane. The current direction of one coil is clockwise and the other is counterclockwise. The current direction at the middle connection of the two coils is the same. The turns of the coils are added together, and the magnetic field intensity and direction are also superposed. Therefore, the magnetic induction intensity at the middle connection is the largest, the stimulation area is small, the stimulation depth is shallow, and it has the function of focusing stimulation. It is generally used for scientific research and mapping of functional areas with strict positioning requirements, and can also be used for treatment, but the stimulation area and intensity are relatively small.

Circular Coil

The coil, which has been used since the birth of TMS in 1985, has a large stimulation area and the same intensity of output stimulation. It is easy to elicit motor evoked potentials and is also suitable for stimulating peripheral nerves. It is used for routine examination and treatment. During high-frequency stimulation, due to the large area of the coil, it is easy to have time and space superposition effect on nerve stimulation, so as to achieve the effect of strong stimulation.

Double Cone Coil

Double cone coil is composed of two circular coils with opposite current directions at an angle of about 90 degrees. The magnetic field vector at the middle point is larger than figure 8 coil. The coil is consistent with the head shape as much as possible according to the size and arc surface of the general human head. The intensity of local stimulation is high, and the focus is not as good as the "8" shaped coil. The biggest feature is that the depth of stimulation is large, and it is suitable for directly stimulating the motor cortex that controls the pelvic floor muscle and lower limb muscle, It can be used for monitoring spinal cord surgery.

Placebo coil

In order to test the stimulation effect of TMS, a double-blind experiment should be conducted in clinic, and placebo coil like the real coil should be used as a control.

YINGCHI Sham TMS System integrates the sham and active stimuation in the same coil, and the device intelligently switches the active and sham output by reading the properties of the IFM stimulation card. The sham coil adopts a special winding process and a physical shielding layer, which can achieve the same output intensity, and the magnetic induction intensity reaching the stimulation target is close to 0. It can realize a true randomized, double-blind, multi-center study, and meet the requirements for the accuracy, reliability and consistency of results in clinical research. The YINGCHI TMS sham-stimulation system not only implements to deliver the active and sham stimulation on one side, but also establishes intelligent random grouping and intelligent output protocols of the active and sham stimulation.

Cooling System

The transcranial magnetic stimulation device generates a high intensity, fast time-varying pulse magnetic field. According to the law of energy conservation, whether electrical energy can be completely converted into magnetic energy in this conversion process, and the lost energy is finally released in the form of heat energy. In different development stages, there are many heat dissipation modes, such as natural cooling, air cooling, liquid external cooling and liquid internal cooling.

The higher the frequency and the longer the duration of continuous stimulation, the higher the heat generated by the coil beat surface. According to the safety standards for medical equipment, TMS magnetic field stimulation coil is a part that may contact the human body. Its surface temperature should be controlled below 41 ℃, and a temperature control device must be installed. Therefore, the super cooling system is the core standard to verify that the transcranial magnetic stimulation instrument can work safely, stably and continuously for a long time.