阅读说明：本技术 一种计算密集阵列tDCS定向调制最优电极刺激模式的方法 (A kind of method that computation-intensive array tDCS orientation modulates optimal electrode stimulating mode ) 是由 秦伟 杨群 郑斌 于 2019-08-22 设计创作，主要内容包括：本发明公开了一种计算密集阵列tDCS定向调制最优电极刺激模式的新方法。特别地,我们优化了固定电极位置的密集阵列的刺激模式,以最大限度地提高ROI中特定方向的电流密度。我们对大脑中的电流功率、单个电极电流和总注入电流施加一组灵活的安全约束,以保护受试者的安全。(The invention discloses the new methods that a kind of computation-intensive array tDCS orientation modulates optimal electrode stimulating mode.Particularly, we optimize the stimulus modality of the closely spaced array of fixed electrode position, to improve the current density of specific direction in ROI to the maximum extent.We apply one group of flexible security constraint to current power, single electrode electric current and the total Injection Current in brain, to protect the safety of subject.)

1. a kind of method that computation-intensive array tDCS orientation modulates optimal electrode stimulating mode, which is characterized in that according to as follows Step:

(1) acquisition NMR structure is as data；

(2) data reconstruction；

(3) division of head tissue is carried out using gauss hybrid models；

(4) each section tissue after segmentation carries out into one institutional framework by region growing algorithm, flooding filling algorithm Walk careful building；

(5) CAD assembling is carried out to newly-generated each section tissue, and carries out FEM meshing；

(6) positioning of target brain area and coordinate space conversion；

(7) boundary condition for setting up Electric Field Simulation carries out emulation solution；

(8) building of objective function and constraint condition；

(9) convex Constraint Anchored Optimization function is solved.

2. the method as described in claim 1, which is characterized in that in accordance with the following steps:

(1) objective function constructs:

The electricity of objective function optimization is the current value of electrode, is defined as:

Wherein, L is electrode total number, and following formula is the objective function that may be implemented for target area in tdcs:

This objective function can obtain maximum current density along specific direction of an electric field in a particular direction.

3. the method as described in claim 1, it is characterised in that:

(1) constraint condition

In the function for establishing optimal conditions,

By the function, limitation enters the total current on head；

I_min≤I≤I_max

The electric current applied by each electrode is limited by its corresponding bound；Each electrode has the upper bound of oneself under Boundary can change with the key area in the position and brain of electrode；

||J_p||₂≤d_p

Local current densities size is limited in position p；This constraint is applied to ECoG by us to stimulate, to prevent current density hot Point runs through entire brain；Same constraint condition can also be used for closely spaced array tDCS, to prevent certain point on scalp from overheating；

||E_P||₂≤e_p

This constraint not instead of current density, partially restrains the size of electric field；Although this constraint is similar to formula 4.8, If head model includes anisotropy, they are non-equivalences；

This function is by the current limit of intracerebral except ROI；This constraint can be generalized to limitation current power on head Certain key areas.

Technical field:

The invention belongs to system emulation fields, and in particular to a kind of computation-intensive optimal electrode thorn of array tDCS orientation modulation The method of energizing mode.

Background technique:

Originate from through cranium galvanic current stimulation systematic research in the 1960s, being a kind of brain stimulation side of Non-Invasive Method.Through cranium galvanic current stimulation at present to various cerebral diseases (cerebral apoplexy, epilepsy, Parkinson's disease, depression, tinnitus, Alzheimer Disease etc.) treatment have important supporting function.In addition, through cranium galvanic current stimulation under various clinical conditions, if patient is to certain When a little drug tolerances are lower or the nervous system disease lacks enough drug therapies, it is possible to the auxiliary as drug therapy Therapy.In other application, be successfully applied to health volunteer through cranium galvanic current stimulation, improve cognitive function, motor learning, Classification learning, working memory.

Cause the excitatoty change of brain through cranium stimulation target using weak electric current.It is by setting through cranium galvanic current stimulation A kind of faint direct current (Noninvasive brain stimulation method of usual 260 μ A to 2mA), because of its certain journey is generated in the electrode of skull Can be changed on degree cortical neuron activity and excitability and induce brain function variation, therefore as a kind of noninvasive and efficient brain Function point analysis technology shows the value of great potential in the illness such as treatment chronic ache, neurological disease, mental disease.

Due to being to be difficult accurately to control come Injection Current using the electrode being placed on scalp through cranium galvanic current stimulation The current direction on head processed, to obtain required current density field in target brain area-of-interest.Especially because scalp With the shunting function of cerebrospinal fluid, the conveying of target brain area region of interest is limited at present.In addition, only controlling target brain area The size of current density may be not enough to reach expected modulation result in region of interest；Current direction is also very crucial.This is just Increase the difficulty of control Injection Current.In addition to this, the comfortableness and security of subject be also need to pay attention to caution because One of element, to prevent being currently applied to scalp (such as skin burn, itch are felt) and brain (such as fatigue, headache, phosphatase) Unintended consequence.Therefore, researcher and clinician are especially interested in improving the accuracy through cranium galvanic current stimulation targeting, To efficiently use the electric current for being transmitted to brain, adverse effect is reduced.

Existing tDCS technical solution

(1) the stimulus modality progress of tDCS

It is simulated in the research of early stage using two disk electrodes, at a distance of 52.4mm between two electrodes, to stimulate just For the purpose of grade motor cortex, anode is placed in above C3, and reference electrode is placed in above forehead.This stimulus modality is also normal in the literature Referred to as unipolar stimulation.It closes on the disk electrode that electrode stimulating is separated by 25mm with two to be simulated, this stimulus modality and morning The bifocus stimulation mode of phase is similar.Three polar stimulation pattern simulations, three disk electrodes are separated by 25mm between each electrode, this It is roughly equivalent to place first anode between CPz and Pz, second anode is placed on C1, places cathode, Mei Geyang on C2 Electric current on extremely is equal, and therefore, cathode current is twice of current value on anode.Band electrode is wound using strip-shaped cathode electrode In forehead (the wide 2mm of band electrode, outer radius 67mm, inside radius 65mm), anode is placed in CZ.This stimulation mode is also claimed For single focus stimulation mode.In recent years, since what tDCS was studied deepens continuously, ring electrode, array electrode etc. stimulate mould Formula also constantly becomes the research emphasis of more and more researchers.

(2) the optimizing research progress of tDCS

Traditional tDCS uses two relatively large patch electrode (25-35cm²) transfer current to brain ROI.It is passing In the tDCS of system, a kind of method for improving targeting is to optimize the position of the two patch electrodes.Optimal location may root Change according to the maximum focusing or directionality of target stimulation site.When the purpose of stimulation be by the electric field strength of target area most When bigization, for the attainment of one's purpose, need constantly to adjust the mode of stimulating electrode.For example, pass through two patch electrodes of normal formula, When modulating cortex target area-primary motor cortex, anode is placed in primary motor cortex, and cathode is placed in the region side on eye socket Formula is not optimal.

Compared with traditional tDCS, improving another method that modulation focuses is using by a large amount of smaller electrode (contacts area For 1-2cm²) composition dense electrode array replace traditional patch electrode, also referred to as closely spaced array tDCS.

In the research of forefathers, Im and colleagues are it is proposed that a kind of method for optimizing two patch electrode positions, then The electric current on 4 × 4 electrod-arrays is determined by optimization algorithm, the electrod-array is instead of traditional anode patch, to obtain Higher target focal power was obtained, but their method is not provided with solution of overall importance.Then, Sadleir and he Colleague use through 19 big patch electrode array that (contact area of electrode is 22cm²) electric current is formed, to make in ROI The maximized idea of average current density^[52], in this process, electric current of the researcher to the non-target area for applying stimulation Apply security constraint, including the ability with cranium external electrode, however, their method do not find yet one it is unique and complete The solution of office, which has limited its versatilities.Dmochowski and his colleague have studied the various unique overall situations of offer The problem of stimulus modality formula^[53], by this method, author has calculated optimal electrode stimulating mode, passes through this mould Formula can increase the degree of focus for target area or the electric field strength intensity of modulation.The optimization process of Ruffini and colleague is Number of electrodes and position are determined with genetic algorithm first, then optimize electrode current with least square method^[54].Their method makes With 27 potential electrode positions, however, the step of due to genetic algorithm, expanding to includes that more multielectrode array is not existing It is real.

The defect of conventional solution

1) big plate electrode diverging, stimulation inaccuracy

Traditional spatial resolution through cranium galvanic current stimulation (tDCS) is considered as relative diffusion, due to skull point It dissipates.However, due to institutional framework/conductibility, the especially details of cerebrospinal fluid (CSF), electric field may concentrate on different brain areas/ Brain ditch.

2) current density of dense electrodes scalp region is excessively high

Also the closely spaced array for having used the electrode more much smaller than patch electrode to form by research, utilizes this dense electrodes side Formula, can effectively improve the focusing of electrode, to achieve the purpose that control stimulated zone, but due between electrode and scalp Contact area is smaller, and the current density that this may cause electrode edge is higher, influences the treatment experience of patient.

3) safety issue

Since the electric current flowing on head is very multiple due to factors such as anatomical structure, tissue signature, electrode position and shapes It is miscellaneous, during blindness inputs electro photoluminescence to patient, it is more likely that can be input to current transition greatly due to experience deficiency The key area of brain causes partial power excessive, to cause safety problem.Therefore it may need to increase in specific setting Current power constraint, to prevent electric current to be excessively transported to the key area of brain.Although we only limit except ROI herein Current power in brain, but optimization problem is easy to merge multiple key areas, there is the safety limit of oneself in each region Limit, to allow neatly to define the key area specific to theme.

4) traditional electrode setting can not cope with individual difference

Traditional gasket stimulation causes disperse to be modulated, and has maximum current flowing between the pad between all subjects.For One subject, there is high current flow immediately below pad, and the position of cortex electric current caused by peak value is variable.These numbers According to showing according to not being that situation carries out specific modeling and can promote consistent and more effective tDCS.Simultaneously as the brain of people Portion's institutional framework has very big otherness, and when carrying out targeting stimulation, single stimulus modality lures electricity to different models Field is also different.

Summary of the invention:

It is an object of the invention to overcome the above-mentioned prior art, a kind of computation-intensive array tDCS orientation tune is provided The method for making optimal electrode stimulating mode.Particularly, we optimize the stimulus modality of the closely spaced array of fixed electrode position, with The current density of specific direction in ROI is improved to the maximum extent.We are to current power, the single electrode electric current and total in brain Injection Current applies one group of flexible security constraint, to protect the safety of subject.

A kind of method that computation-intensive array tDCS orientation modulates optimal electrode stimulating mode, in accordance with the following steps:

(1) acquisition NMR structure is as data；

(2) data reconstruction；

(3) division of head tissue is carried out using gauss hybrid models；

(4) each section tissue after segmentation carries out institutional framework by region growing algorithm, flooding filling algorithm Further careful building；

(5) CAD assembling is carried out to newly-generated each section tissue, and carries out FEM meshing；

(6) positioning of target brain area and coordinate space conversion；

(7) boundary condition for setting up Electric Field Simulation carries out emulation solution；

(8) building of objective function and constraint condition；

(9) convex Constraint Anchored Optimization function is solved.

In accordance with the following steps:

(1) objective function constructs:

The electricity of objective function optimization is the current value of electrode, is defined as:

Wherein, L is electrode total number, and following formula is the target letter that may be implemented for target area in tdcs Number:

This objective function can obtain maximum current density along specific direction of an electric field in a particular direction.

The method:

(1) constraint condition

In the function for establishing optimal conditions,

By the function, limitation enters the total current on head；

I_min≤I≤I_max

The electric current applied by each electrode is limited by its corresponding bound；Each electrode have oneself the upper bound and Lower bound can change with the key area in the position and brain of electrode；

||J_p||₂≤d_p

Local current densities size is limited in position p；This constraint is applied to ECoG by us to stimulate, to prevent electric current close It spends hot spot and runs through entire brain；Same constraint condition can also be used for closely spaced array tDCS, to prevent certain point on scalp from overheating；

||E_P||₂≤e_P

This constraint not instead of current density, partially restrains the size of electric field；Although this constraint is similar to formula 4.8, but if head model includes anisotropy, they are non-equivalences；

This function is by the current limit of intracerebral except ROI；This constraint can be generalized to limitation current power in head Certain key areas in portion.

Beneficial effects of the present invention: the stimulus modality of the closely spaced array of fixed electrode position is optimized, with to the maximum extent Improve the current density of specific direction in ROI.We apply current power, single electrode electric current and the total Injection Current in brain Add one group of flexible security constraint, to protect the safety of subject.

Detailed description of the invention:

Fig. 1 is brain tissue's structure chart；

Fig. 2 is head model structure chart；

Fig. 3 is target brain area positioning figure；

Fig. 4 is brain distribution map of the electric field；

Fig. 5 is flow chart.

Specific embodiment:

The invention will be described in further detail with reference to the accompanying drawing:

It is right below in conjunction with example, such as Fig. 5 in order to which the purpose of the present invention, technical solution and advantage is more clearly understood The present invention is described in detail, and steps are as follows:

1) scanning NMR structure is as data (being the data of schizophrenic patients used in present case)

2) nuclear magnetic data is formatted, and carries out brain tissue's based fragmentation, be divided into scalp, skull, brain ridge Liquid, grey matter, white matter ingredient.As shown in Fig. 1, the basic organization divided.

3) tissue split is filtered, smoothly, acnode removal, the operation such as Boolean calculation, carry out detailed-oriented place Reason, and surface model hypostazation conversion and CAD splicing are assembled.To obtain true head model structure.It is as shown in Fig. 2 Head model structure.

4) electrode configuration and finite element meshing division based on the 10-10 system of brain electricity are carried out to head model, applied Added electric field simulated conditions, and carry out the simulation calculation of Basic Solutions.

5) brain area positioning is carried out to target brain area to be optimized.It is as shown in Fig. 3 brain area positioning figure.

6) to the institutes objective function and optimal conditions of obtained Basic Solutions, constrained linear optimization iteration is carried out Solution procedure calculates, and electrode position and Injection Current size after being optimized accordingly.

By taking the region of optimization is back lateral prefrontal as an example, this region is in " bow " shape in cortex for we, covers volume The 7.07% of the total ingredient of grey matter is occupied, and is distributed in cortex surface layer, in optimization process, we select to allow forehead on the outside of left dorsal Leaf obtains maximum forward current value density, and right side back lateral prefrontal obtains reversed current density.So we have selected the mesh Scalar functions

Realize optimization.By this method, we do not need a determining target area electric current to be achieved Size.Such as scheme the attached 4 brain electric fields point showing after the electrode position being calculated and such as current distributions, and optimization Butut.

Optimization system design cycle is as follows:

(1) acquisition NMR structure is as data；

(2) data reconstruction；

(3) division of head tissue is carried out using gauss hybrid models；

(4) to each section tissue after segmentation by region growing algorithm, flooding filling algorithm etc. to institutional framework into Row further careful building；

(5) CAD assembling is carried out to newly-generated each section tissue, and carries out FEM meshing；

(6) positioning of target brain area and coordinate space conversion；

(7) boundary condition for setting up Electric Field Simulation carries out emulation solution；

(8) building of objective function and constraint condition；

(9) convex Constraint Anchored Optimization function is solved.

Process of optimization is as follows:

Table 4-1 symbol description

(2) objective function constructs:

The electricity of objective function optimization is the current value of electrode, we are defined as:

Wherein, L is electrode total number, and following formula is the target letter that may be implemented for target area in tdcs Number:

This objective function can obtain maximum current density along specific direction of an electric field in a particular direction.

(2) constraint condition

In the function for establishing optimal conditions, we consider the total current, the head surface local current mistakes that enter head (the edge current problems of too occurred in chapter 3 emulation), the electric current of single electrode etc. greatly.

By the function, limitation enters the total current on head.

7_min≤I≤I_max

The electric current applied by each electrode is limited by its corresponding bound.Each electrode have oneself the upper bound and Lower bound, this may change with the key area in the position and brain of electrode.

||J_p||₂≤d_p

Local current densities size is limited in position p.This constraint is applied to ECoG by us to stimulate, to prevent electric current close It spends hot spot and runs through entire brain.Same constraint condition can also be used for closely spaced array tDCS, to prevent certain point on scalp from overheating.

||E_P||₂≤e_p

This constraint not instead of current density, partially restrains the size of electric field.Although this constraint is similar to formula 4.8, but if head model includes anisotropy, they are non-equivalences.

This function is by the current limit of intracerebral except ROI.This constraint can be generalized to limitation current power in head Certain key areas in portion.

Different for the selection in electric Field Optimization direction in the research of forefathers, tangential field, radial field are as main research Content, in addition to this, according to the specific position of brain area, the research for specific direction electric field is also a big content.It is special calculating During the electric field strength for determining direction, we need known to obtain the component of electric field strength in that direction The direction of vector field and the size of electric field strength, and projected in this specific direction.

1.1.1 the optimization of computational efficiency

We assume that in ROI region, the electric field value in expected direction is seen as constant in each individually unit, Integral in majorized function then becomes weighted sum.We calculate these integrals, and they are reduced to electrode current array Linear sum quadratic function, in this way, whole optimization problem has then evolved into as follows:

The formula is constrained in following condition:

Constraint condition one:

I^TQI≤p_max

Constraint condition two:

||I||₁≤2I_max

Constraint condition three:

I_min≤I≤I_max

Herein, regard matrix w as weight array, indicate each electric current of clicking to the correlation of ROI directcd current density. Matrix Q is by these electrode currents with the brain electrical communication outside ROI to together.Since objective function and constraint optimal conditions are all Therefore convex optimization problem has unique global solution.In solution procedure, we used the kit CVX in matlab. It is studied referring to forefathers, in this analogue simulation, the total current for entering head is limited in 2mA, the electric current of each electrode is limited Electric current outside 0.50mA, ROI is limited in 10^-6A²/m.By this group of constraint condition, we expand for constraint condition with The research of interaction mode between optimal stimulus mode.