Two 8-shaped cerebral magnetic stimulation coil
[technical field]
The invention belongs to transcranial magnetic stimulation technical field, particularly a kind of stevedore knot structure cerebral magnetic stimulation coil.
[background technology]
Transcranial magnetic stimulation (Transcranial magnetic stimulation, be called for short TMS) be a kind of noinvasive biostimulation technology, it utilizes time-varying magnetic field to produce induction field, bioelectric current is caused to conduct in the tissue, and then make nerve fiber, neuron and muscle depolarization, in order to change the action potential of cortical neurogenic cell, affect brain intracellular metabolite and neuroelectricity activity, therefore can in order to treat quite a few neural and mental sickness.The disease that TMS can be utilized to carry out treating at present comprises aphasia, tinnitus, Parkinson's disease, myodystonia, amyotrophic lateral sclerosis (spinal cord) lateral sclerosis, epilepsy, migraine, dysphasia, half side space are ignored, phantom pain, chronic pain, obsession etc.It can also close the activity of specific cortical area in addition, realizes the virtual damage of brain local function.
Transcranial magnetic stimulation instrument can be divided into two parts: pulse current produces circuit and stimulating coil.The parameters of stimulating coil is the core of whole magnetic stimulating device.In order to appointed part can be stimulated accurately and effectively, to the intensity in the magnetic field that coil produces, the degree of depth and degree of focus is stimulated to be proposed very high requirement.On the other hand, from the angle of studying physiological effect, also need the parameters of accurate quantification coil.The degree of focus of Neural stem cell determines the stimulation selective power of magnetic stimulator.High degree of focus can reduce field stimulation, increases and stimulates specific aim, reduces the possibility that irrelevant nervous tissue is upset.The stimulation degree of depth determines the distance that magnetic stimulator can keep certain stimulus intensity.The high degree of depth that stimulates is only had just likely to realize the effective stimulus organized dark cranial nerve.Right existing figure-eight coil (butterfly coil) degree of focus is not enough, and cause field stimulation large, the problem that specific aim is not strong, the probability that irrelevant nervous tissue is upset is large.
[summary of the invention]
The object of the present invention is to provide a kind of two 8-shaped cerebral magnetic stimulation coil with higher degree of focus, improve the effect of transcranial magnetic stimulation, to solve the problem of traditional figure-eight coil degree of focus deficiency.
To achieve these goals, the present invention adopts following technical scheme:
A kind of two 8-shaped cerebral magnetic stimulation coil, is connected to form by the first figure-eight coil and the second figure-eight coil, spatially the center superposition of the first figure-eight coil and the second figure-eight coil; And two radiuses that the circular coil that two of the second figure-eight coil radiuses are Ri is positioned at the first corresponding figure-eight coil are the circular coil of Ro, wherein Ro > Ri.
The present invention further improves and is: Ri:Ro=(0.4 ~ 0.5): 1.
The present invention further improves and is: Ri:Ro=0.5:1.
The present invention further improves and is: the number of turn Ni of the second figure-eight coil is (1 ~ 10) with the ratio of the number of turn No of the first figure-eight coil: 1.
The present invention further improves and is: the first figure-eight coil and the second figure-eight coil are positioned at same plane.
Compared with prior art, the present invention has the following advantages: a kind of two 8-shaped cerebral magnetic stimulation coil of the present invention, by arranging the less circular coil of two radiuses in traditional figure-eight coil inside, and by arrangement of conductors locus, inner-outer coil radius and the inner-outer coil number of turn to improve the degree of focus of coil stimulation; Field stimulation is concentrated, and with strong points, the probability that irrelevant nervous tissue is upset significantly reduces.
[accompanying drawing explanation]
The HPR comparison diagram of figure-eight coil when Fig. 1 is the different stimulated degree of depth and two figure-eight coil (Double-butterflycoil);
Fig. 2 is of the present invention pair of figure-eight coil structure chart;
Fig. 3 is a kind of through the raw circuit diagram of cranium magnetic thorn pulse excitation;
Fig. 4 is the induction field size distribution figure that two 8 wordline circles produce on certain depth;
When Fig. 5 is the different stimulated degree of depth, the graph of a relation of coil HPR and inside and outside umber of turn ratio;
Fig. 6 is outer winding radius when being 3.5cm, the graph of a relation of HPR and Ni/No and Ri/Ro.
[detailed description of the invention]
Below in conjunction with accompanying drawing, the present invention is described in further detail.
Refer to shown in Fig. 2, a kind of two 8-shaped cerebral magnetic stimulation coil of the present invention, connected to form by the figure-eight coil of two different winding radiuses, the figure-eight coil of two different winding radiuses is positioned at same plane, the spatially center superposition of two figure-eight coils, flow through same electric current I in two coils, the effect strengthening center field intensity in center in the same way, is played in electric current I direction.Two 8-shaped cerebral magnetic stimulation coil produces the alternating magnetic field of high degree of focus after being connected to a pulse power under the function of current, may be used for experiment and the treatment of carrying out transcranial magnetic stimulation.The two figure-eight coil of the present invention can use various plain conductor coiling to form, and adopts the mode of not shield electromagnetic to make coil arrangement become Fig. 2 structure.
The two 8-shaped cerebral magnetic stimulation coil of the present invention, compared with traditional figure-eight coil, reaches the object improving degree of focus by arrangement of conductors locus, inner-outer coil radius and the inner-outer coil number of turn.Referring to shown in Fig. 4, is the induction field size distribution that the two 8 wordline circles of the present invention produce on certain depth, can find out that the piezomagnetic theory of the two 8 wordline circles of the present invention is similar with 8 wordline loop-shaped, but main peak is narrower, is conducive to raising degree of focus.Inside and outside two 8-shaped cerebral magnetic stimulation coil, winding radius is respectively Ri, Ro, inside and outside umber of turn is Ni, No, in order to quantize degree of focus, introduce half values of powers region (Half Power Region, HPR), namely electric field magnitude is the area in the region formed a little at maximum decay-3dB place, and HPR is less, then degree of focus is better.The degree of focus of more two 8-shaped cerebral magnetic stimulation coil and figure-eight coil, calculate the HPR value in the different stimulated degree of depth, wherein, the radius of figure-eight coil is 3.5cm, and the number of turn is 4 circles; Two 8-shaped cerebral magnetic stimulation coil selects parameters optimization, i.e. Ro=3.5cm, Ri=2cm, No=4, Ni=8, and result as shown in Figure 1; When stimulating the degree of depth to change from 1cm to 4cm, the HPR of two 8-shaped cerebral magnetic stimulation coil is less than 8-shaped all the time, illustrates that the degree of focus of two 8-shaped cerebral magnetic stimulation coil is better than the degree of focus of figure-eight coil.
Provide some references at this, such as, get Ro=3.5cm, Ri=2.0cm, stimulate depth H to get 2.0cm respectively, 3.0cm and 4.0cm, I=5kA, f=10kHz, Ni/No get 1 to 10.HPR result is as shown in Figure 5, visible, and stimulate the degree of depth darker, HPR is larger, and degree of focus is poorer; When inside and outside umber of turn ratio increases, its HPR reduces, but the speed reduced increases with the number of turn and slows down, and therefore, in order to improve the degree of focus of two figure-eight coil as far as possible, should make interior umber of turn slightly more than outer umber of turn.If get Ro=3.5cm, H=3.0cm, I=5kA, f=10kHz, Ni/No get 1 to 10, Ri/Ro and get 0.1 to 0.9, as shown in Figure 6, for certain Ni/No, when Ri/Ro close to 0.5 time, HPR obtains minima.Ni/No close to 10 time, make HPR obtain the Ri/Ro of optimal value close to 0.4, when Ni/No close to 1 time, make HPR obtain the Ri/Ro of optimal value close to 0.5.In order to reach best degree of focus, suggestion adopts Ri/Ro=0.5.
Length and the method for arranging of lead-in wire will be noted when coil being connected to pulse generating circuit, as far as possible simple, in order to avoid have influence on coil effect.Provide a kind of pulse generating circuit at this, as shown in Figure 3, L is two figure-eight coils; C is charging capacitor, and R is current-limiting resistance, and D is commutation diode, and these elements constitute rectification charging loop.The control signal sent by control circuit triggers turn on thyristors, makes electric capacity to coil discharge, produces sinusoidal single-pulse current, for transcranial magnetic stimulation.