CN113384257A - Electrode arrangement method for long-term high-precision EIT detection of lesion part of cerebral hemorrhage patient - Google Patents
Electrode arrangement method for long-term high-precision EIT detection of lesion part of cerebral hemorrhage patient Download PDFInfo
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Abstract
The invention discloses an electrode arrangement method for long-term high-precision EIT detection of a diseased region of a patient with cerebral hemorrhage, which comprises the steps of dividing three regions of the brain of the patient, determining the diseased position according to a previous CT or MRI image, placing n electrodes on a horizontal plane which is 3cm away from the eyebrows of the patient, respectively placing one electrode at the center of the forehead and the center of the forehead as a fixed electrode, and placing the other electrodes at intervals; optimizing the electrode positions according to different regions where lesions are located, selecting and moving the electrodes except the fixed electrodes in pairs, recording and storing RS and PE values, deleting data to a certain extent when the unselected electrode pairs are smaller than the fixed electrodes, and then optimizing and fixing the positions of each pair of electrodes by taking the RS and the PE as standards. And circularly selecting the electrode pairs and optimizing the positions of the electrode pairs until all the electrodes are optimized. The invention effectively improves the relative sensitivity in the divided regions, successfully reduces the artifacts, optimizes the imaging quality and improves the success rate of complete cure of patients.
Description
Technical Field
The invention belongs to the technical field of application of electrical tomography in brain imaging detection, and particularly relates to an electrode arrangement method for long-term high-precision EIT detection of a diseased region of a cerebral hemorrhage patient.
Background
Cerebral hemorrhage is a common cerebral disease with high disability rate and mortality rate. The causes of the disease are overexertion, alternate climate change, bad taste (smoking, alcoholism, salt excess, and overweight), blood pressure fluctuation, emotional agitation, and overwork. To ensure that a patient can recover completely from a cerebral hemorrhage, real-time monitoring of the patient during treatment is required, thereby reducing the time spent in the diagnostic process and increasing the probability of healing. Currently, Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) are commonly used for diagnosis of brain diseases. CT techniques have high radiation, are highly harmful to the human body, MRI techniques are expensive, and the detection time is long. Electrical Impedance Tomography (EIT) is an emerging visualization technology, has the characteristics of no radiation, non-invasion, low cost and the like compared with the traditional CT technology and MRI technology, and is commonly used for industrial detection and clinical medical imaging. The EIT technology can well meet the requirements of cerebral hemorrhage detection, namely, the real-time detection of lesion parts is carried out for a long time at low cost, so that the EIT technology is widely concerned. For example, XC Liu et al, published 2019 in Medical & bioengineering & Computing, volume 57 1917, 1931, entitled "An iterative damped least squares algorithm for simultaneously monitoring the development of hemorrhagic and secondary ischemic lesions of brain injury" (iterative damped least squares-methods for diagnosing the same extent of ischemic lesions in brain injury). Most of the researches optimize the EIT technology around an algorithm, and the accuracy of a reconstructed image is ensured through a more stable algorithm. The arrangement of EIT sensors also has a very large impact on image quality. The existing electrode arrangement mode adopts uniform 16 electrode arrangement to pursue the even distribution of sensitivity in the whole area. However, in the practical application process, the EIT technique has the characteristics of no radiation, non-invasion and the like, and is usually used as a continuous long-time detection means after qualitative analysis such as the CT technique, the MRI technique and the like, so that certain prior information exists when the EIT technique is used, and the conventional uniform 16 electrodes have the problem of high sensitivity to non-diseased regions, thereby affecting the imaging quality of the diseased regions. Therefore, it is necessary to optimize the distribution of EIT sensors to improve the sensitivity of the lesion region of a patient with cerebral hemorrhage.
Disclosure of Invention
The invention solves the technical problem of providing an electrode arrangement method for long-term high-precision EIT detection of a lesion part of a cerebral hemorrhage patient, which utilizes the soft field characteristic of EIT technology and influences the sensitivity distribution of the whole imaging area by changing the arrangement of electrodes, so that the sensitivity of the lesion part of the cerebral hemorrhage patient is improved under the condition of prior information, and the imaging quality is improved.
The invention adopts the following technical scheme for solving the technical problems, and aims at an electrode arrangement method for long-term high-precision EIT detection of lesion parts of patients with cerebral hemorrhage, which is characterized by comprising the following specific steps:
step one, in order to enable imaging to be more accurate, a brain is divided into three initial areas in a targeted manner, wherein the initial areas are omega 1, omega 2 and omega 3, the omega 1 is an area surrounded by the forehead to the temples on two sides, the omega 3 is an area surrounded by the ears on two sides and the back of the back pillow, the omega 2 is an area surrounded by the temples on two sides and the ears on two sides, and the omega 1 and the omega 3 are areas with multiple hemorrhagic lesions of the brain and are areas with serious imaging deformation under the arrangement of electrodes of a common EIT technology;
step two, determining the position of the lesion according to the early CT or MRI image of the cerebral hemorrhage patient, and judging the region where the lesion is located according to the division in the step one;
step three, respectively placing one electrode as a fixed electrode at the center of the front extra periphery and the center of the periphery of the back pillow on a horizontal plane 3cm above the double eyebrows, and placing the other n-2 electrodes at intervals of arc length
Placing, wherein c is the perimeter of the cranium of the patient on the horizontal plane, and n is the number of electrodes;
step four, calculating and retaining the relative sensitivity RS of the region where the lesion is located, reconstructing an image, calculating and retaining the position offset PE:
SΩiexpressing the sensitivity value of pixel points in the omega i region, expressing the sensitivity value of pixel points in the whole brain region by S, wherein the value range of i is 1 or 3, and Xm、YmRespectively representing the X-axis coordinate and the Y-axis coordinate of the pixel points with the conductivity more than or equal to 50% of the maximum conductivity in all the pixel points of the reconstructed image, q representing the number of the pixel points with the conductivity more than or equal to 50% of the maximum conductivity in all the pixel points of the reconstructed image, and X, Y respectively representing the X-axis coordinate and the Y-axis coordinate of the geometric center of the lesion on the CT or MRI image;
the calculation formula of the sensitivity value of the pixel point is as follows:
wherein i and j represent the ith row and the jth column of the sensitivity pixel,
respectively indicate that the excitation current of the ith electrode group and the jth electrode group is Ii，IjA gradient of a potential distribution of the time-field domain;
and step five, respectively carrying out corresponding electrode position optimization on the n electrodes according to different regions, calculating a sensitivity matrix by adopting a relative excitation mode, and carrying out image reconstruction, wherein the specific steps are as follows:
(5.1) if the lesion area is in the range of omega 1, carrying out the following steps:
step 5.11, selecting a pair of electrodes which are symmetrical left and right by taking a connecting line of the fixed electrodes as a symmetrical axis;
step 5.12, moving the selected electrode, calculating and reserving RE and PE values;
step 5.13, judging whether the unselected electrode pairs are smaller than
If yes, retaining all positions of the selected electrode pairs from the two ears of the head to the back pillow and corresponding RS and PE data, removing the rest data, and if not, not operating;
5.14, screening the optimal electrode position according to the RS and PE values;
step 5.15, fixing the selected electrode pair to the optimal electrode position, circularly performing the step 5.11 to the step 5.15, and then performing selection and optimization on the electrode pair until all the electrodes are fixed to the optimal electrode position, and finishing the regional optimization;
(5.2) if the lesion area is within the range of omega 2, not adjusting;
(5.3) if the lesion area is within the range of omega 3, performing the following steps:
step 5.31, selecting a pair of electrodes which are symmetrical left and right by taking a connecting line of the fixed electrodes as a symmetrical axis;
step 5.32, moving the selected electrode, calculating and reserving RE and PE values;
step 5.33, judge whether the unselected electrode couple is smaller than
If yes, retaining all positions from the forehead to the two ears of the head and corresponding RS and PE data of the selected electrode pair, and removing the rest data, otherwise, not operating;
step 5.34, screening the optimal electrode position according to the RS and PE values;
and 5.35, fixing the selected electrode pair to the optimal electrode position, circularly performing the steps 5.31-5.35, and then selecting and optimizing the electrode pair until all the electrodes are fixed to the optimal electrode position, and finishing the regional optimization.
Further, the value of the number n of the electrodes is 8, 10, 12, 14, 16 or 18.
Is further defined as relativeThe specific process of the excitation mode is as follows: the forehead fixing electrode is used as the No. 1 electrode, the N electrodes are arranged in a reverse time mode, the first excitation is used for injecting current into the No. 1 electrode,
the signal electrode, namely the rear pillow fixed electrode, is used as a current loop; the second excitation injects current into the No. 2 electrode,
the signal electrode, namely the rear pillow fixed electrode, is used as a current loop; by analogy, when the serial number of the electrode serving as a current loop exceeds n, the serial number is continued from 1 until the n electrode injects current,
the excitation is finished when the signal electrode is used as a current loop, so that the length of the connecting line of all the injected currents and the electrode pair used as the current loop is close to the longest diameter of the head, the current can conveniently penetrate through the skull, and the best effect is obtained.
Further limiting, the sensitivity matrix is specifically processed as follows: the brain region is modeled by using a finite element method and is divided into a finite number of grids, each grid is a pixel point, the sensitivity of each grid to the conductivity change is calculated, and the higher the sensitivity is, the larger the conductivity change is.
Further limiting, the image reconstruction specific process is as follows: in each imaging, n electrodes distributed around the head of a cerebral hemorrhage patient are utilized, safe current is sequentially injected from a forehead fixed electrode in a counterclockwise mode, measuring voltages are respectively obtained from the electrodes except an exciting electrode and the electrodes serving as current loop electrodes in a counterclockwise mode, and the conductivity change of the brain is inverted by utilizing a sensitivity matrix obtained by a corresponding finite element model, namely image reconstruction is carried out.
The invention has the beneficial effects that: the invention provides an electrode arrangement method for long-term high-precision EIT detection of lesion parts of a cerebral hemorrhage patient. The electrodes are divided into pairs, the fixed electrodes are symmetrically moved by the symmetry axis, the optimal positions of the electrode pairs are determined according to evaluation standards such as relative sensitivity and position deviation, and finally all the electrodes are optimized, so that the sensitivity is concentrated in a lesion area. The imaging position deviation precision is guaranteed, meanwhile, reconstruction artifacts are effectively reduced, and the success rate of complete cure of patients is increased.
Drawings
Fig. 1 is a flow chart of an electrode arrangement method for long-term high-precision EIT detection of a diseased region of a cerebral hemorrhage patient according to the present invention.
Fig. 2 shows the division of the regions Ω 1, Ω 2, and Ω 3, the electrode arrangement optimization result for the region Ω 1, the measurement mode, and the excitation mode in the embodiment of the present invention.
Fig. 3 is a comparison graph of the final imaging results for 4 different electrode arrangements.
Fig. 4 shows the relative sensitivities of the regions Ω 1, Ω 2, and Ω 3 for 4 different electrode arrangements.
Fig. 5 is an image comparison of two electrode arrangements at three different bleeding locations within the region of Ω 1.
In the figure: 1-electrode, 2-safety current, 3-measuring voltage.
Detailed Description
The electrode arrangement method for long-term high-precision EIT detection of lesion sites of patients with cerebral hemorrhage according to the present invention will be described in detail with reference to the accompanying drawings and examples.
The electrode arrangement method for long-term high-precision EIT detection of the lesion part of the cerebral hemorrhage patient aims at improving the relative sensitivity of a certain area of the irregular head model, optimizes the electrode arrangement, and specifically comprises the following steps as shown in figure 1:
step one, in order to enable imaging to be more accurate, the brain is divided into three initial areas in a targeted mode, wherein the initial areas are omega 1, omega 2 and omega 3, the omega 1 is an area surrounded by the forehead to the temples on two sides, the omega 3 is an area surrounded by the ears on two sides and the back pillow, the omega 2 is an area surrounded by the temples on two sides and the ears on two sides, and the omega 1 and the omega 3 are areas with multiple occurrence of cerebral hemorrhage and areas with serious imaging deformation under arrangement of common EIT electrodes.
And step two, determining the position of the lesion according to the previous CT or MRI image of the patient, and judging the region where the lesion is located according to the division in the step one.
Step three, respectively placing one electrode as a fixed electrode at the center of the front extra periphery and the center of the periphery of the back pillow on a horizontal plane 3cm above the double eyebrows, and spacing arc lengths of the rest n-2 electrodes at the electrode centers
Placing, wherein c is the perimeter of the cranium of the patient on the horizontal plane, and the value range of the number n of the electrodes is as follows: 8. 10, 12, 14, 16 or 18.
Step four, calculating and reserving the relative sensitivity RS of the region where the lesion is located; and calculating a sensitivity matrix by adopting a relative excitation mode, reconstructing an image, and calculating and reserving the position offset PE.
SΩiExpressing the sensitivity value of pixel points in the omega i region, and expressing the sensitivity value of pixel points in the whole brain region by S, wherein the value range of i is 1 or 3; xm、YmRespectively representing the X-axis coordinate and the Y-axis coordinate of the pixel points with the conductivity being more than or equal to 50% of the maximum conductivity in all the pixel points of the reconstructed image, q representing the number of the pixel points with the conductivity being more than or equal to 50% of the maximum conductivity in all the pixel points of the reconstructed image, and X, Y representing the X-axis coordinate and the Y-axis coordinate of the geometric center of the lesion on the CT or MRI image.
The relative excitation modes are specifically: the forehead fixing electrode is used as the No. 1 electrode, the N electrodes are arranged in a reverse time mode, the first excitation is used for injecting current into the No. 1 electrode,
the signal electrode, namely the rear pillow fixed electrode, is used as a current loop; the second excitation injects current into the No. 2 electrode,
the signal electrode, namely the rear pillow fixed electrode, is used as a current loop; by analogy, when the serial number of the electrode serving as a current loop exceeds n, the serial number is continued from 1 until the n electrode injects current,
the excitation is finished when the signal electrode is used as a current loop, so that the length of the connecting line of all the injected currents and the electrode pair used as the current loop is close to the longest diameter of the head, the current can conveniently penetrate through the skull, and the best effect is obtained.
The sensitivity matrix is specifically: the brain region is modeled by using a finite element method and is divided into a finite number of grids, each grid is a pixel point, the sensitivity of each grid to the conductivity change is calculated, and the higher the sensitivity is, the larger the conductivity change is.
The calculation formula of the sensitivity value of the pixel point is as follows:
wherein i and j represent the ith row and the jth column of the sensitivity pixel,
respectively indicate that the excitation current of the ith electrode group and the jth electrode group is Ii、IjGradient of potential distribution of the time-field domain.
The image reconstruction specifically comprises: in each imaging, n electrodes 1 distributed around the head of a patient are utilized, safe current 2 is sequentially injected from a forehead fixed electrode in a counterclockwise direction, measuring voltage 3 is respectively obtained from the other electrodes in a counterclockwise direction, and the conductivity change of the brain is inverted by utilizing a sensitivity matrix obtained by a corresponding finite element model, namely image reconstruction is carried out.
Step five, respectively carrying out corresponding electrode position optimization on the n electrodes according to different regions, specifically as follows:
(5.1) if the lesion area is in the range of omega 1, carrying out the following steps:
and 5.11, selecting a pair of electrodes which are symmetrical left and right by taking the connecting line of the fixed electrodes as a symmetrical axis, and sequentially selecting the electrode pairs towards the direction of the back pillow fixed electrode from the pair of electrodes closest to the forehead fixed electrode.
Step 5.12, after selecting a pair of electrodes in step 5.11, the selected pair of electrodes is moved towards the forehead fixed electrode symmetrically from side to side by taking the connecting line of the fixed electrodes as a symmetrical axis, and the arc length of each movement is equal to
e is the length of a single electrode, and RS and PE values after each movement are calculated and reserved. The constraint conditions for the electrode pair movement are: the spacing of any electrode edge cannot be less than e.
Step 5.13, judging whether the unselected electrode pairs are smaller than
If yes, retaining all positions of the selected electrode pairs from the two ears of the head to the back pillow and corresponding RS and PE data, and removing the rest data. If not, no operation is performed.
And 5.14, screening out the position of the maximum value of the RS in all the stored data of the selected electrode pair, and judging whether the PE value at the position is the minimum value or not, or whether the PE value is less than or equal to 0.5 mm: if yes, selecting the position as the optimal electrode position of the selected electrode pair; if not, removing the position data, repeating the step, and screening a new RS maximum position until an optimal electrode position is obtained.
And 5.15, fixing the selected electrode pair to the optimal electrode position, and removing all data. And (5.11-5.15) circularly performing the steps, and selecting and optimizing the electrode pairs until the region optimization is finished when all the electrodes are fixed to the optimal electrode positions.
(5.2) if the lesion area is within the range of omega 2, no adjustment is made.
(5.3) if the lesion area is within the range of omega 3, performing the following steps:
and 5.31, selecting a pair of electrodes which are symmetrical left and right by taking the connecting line of the fixed electrodes as a symmetrical axis, and sequentially selecting the electrode pairs towards the direction of the back pillow fixed electrode from the electrode pair closest to the forehead fixed electrode.
Step 5.32, after selecting a pair of electrodes in step 5.31, the selected pair of electrodes is moved towards the back pillow fixed electrode symmetrically by taking the connecting line of the fixed electrodes as a symmetry axis, and the arc length of each movement is equal to
e is the length of a single electrode, and RS and PE values after each movement are calculated and reserved. The constraint conditions for the electrode pair movement are: the spacing of any electrode edge cannot be less than e.
Step 5.33, judge whether the unselected electrode couple is smaller than
If yes, retaining all positions of the selected electrode pair from the forehead to the two ears of the head and corresponding RS and PE data, and removing the rest data. If not, no operation is performed.
And 5.34, screening out the position of the maximum value of the RS in all the stored data of the selected electrode pair, and judging whether the PE value at the position is the minimum value or not, or whether the PE value is less than or equal to 0.5 mm: if yes, selecting the position as the optimal electrode position of the selected electrode pair; if not, removing the position data, repeating the step, and screening a new RS maximum position until an optimal electrode position is obtained.
And 5.35, fixing the selected electrode pair to the optimal electrode position, and deleting all data. And (5.31-5.35) circularly performing the steps, and selecting and optimizing the electrode pairs until the region optimization is finished when all the electrodes are fixed to the optimal electrode positions.
Fig. 2 shows an embodiment of the electrode arrangement optimized for the region Ω 1 according to the present invention, in which 16 electrodes are used, the electrodes are set at a horizontal plane 3cm above the brow, and optimized to the optimal position, the electrode spacing of the whole electrode arrangement is closer to the forehead fixation electrode, and the electrode spacing is thinner near the back pillow fixation electrode. With relative excitation, the adjacent measurement mode, ensures penetration of the skull for intracerebral imaging by maximizing the excitation electrode distance, i.e., the path through which current flows.
Fig. 3 shows 4 different electrode arrangements for comparing the imaging results of the region of Ω 1. The brain background conductivity is 0.15S/m, the human brain cerebrospinal fluid conductivity is 0.8S/m, and the bleeding conductivity is 0.8S/m. Wherein the first column is an image of the uniform electrode; the second column is that 15 electrodes are uniformly arranged on the front half of the head of each ear of the forehead, and one electrode is arranged in the center of the back pillow (15-1 arrangement mode); the third column divides the 16 electrodes into two groups, and the two groups are uniformly placed on the forehead to the temple and the two ears to the back pillow position. The fourth column is the electrode arrangement optimized for the present invention. It can be seen that the optimized electrode imaging of the invention has fewer artifacts and is closer to a real model, which is obviously superior to other electrode distributions. Under the 15-1 electrode arrangement mode, the number of the rear half-cycle electrodes from the two ears to the head of the rear pillow is too small, so that the whole imaging result is very poor, and the number of the rear half-cycle electrodes cannot be less than that of the rear half-cycle electrodes when the electrode arrangement is optimized
As shown in fig. 4, there are 4 different electrode arrangement modes, and the relative sensitivities in the regions Ω 1, Ω 2, and Ω 3, it can be seen that the conventional uniform electrode arrangement mode has a lower sensitivity in the regions Ω 1 and Ω 3 and a higher sensitivity in the region Ω 2. The relative sensitivity of the optimized electrode arrangement to the omega 1 area is obviously improved. Although the 15-1 electrode arrangement has the highest relative sensitivity to the region of Ω 1, it does not satisfy the requirement that the number of second half-cycle electrodes is less than that of second half-cycle electrodes
The imaging effect is deteriorated, so that the condition that the number of half-period electrodes is less than that of half-period electrodes is avoided in the optimization process
This is the case.
The imaging contrast for 3 different bleeding sites, a uniform electrode arrangement and an optimized electrode arrangement of the present invention is shown in fig. 5. The background conductivity of the brain is 0.15S/m, and the background conductivity of the brain is the conductivity of cerebrospinal fluid of the human brain. The bleeding conductivity is set to be 0.8S/m, and it can be seen that the imaging result of the optimized electrode arrangement of the invention is obviously superior to the imaging of uniform electrode arrangement at 3 different positions in the omega 1 region, the final artifact is very little, the image has almost no deformation, and the shape and the size of the original model are still kept, thus proving that the imaging precision of the optimized electrode arrangement of the invention in the omega 1 region is obviously improved. Since the PE values are extremely small and satisfy the conditions after the electrodes are homogenized and optimized, they are not listed here.
The above description is only exemplary of the present invention and should not be taken as limiting the invention, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. The electrode arrangement method for long-term high-precision EIT detection of the lesion part of a cerebral hemorrhage patient is characterized by comprising the following steps of:
step one, in order to enable imaging to be more accurate, a brain is divided into three initial areas in a targeted manner, wherein the initial areas are omega 1, omega 2 and omega 3, the omega 1 is an area surrounded by the forehead to the temples on two sides, the omega 3 is an area surrounded by the ears on two sides and the back of the back pillow, the omega 2 is an area surrounded by the temples on two sides and the ears on two sides, and the omega 1 and the omega 3 are areas with multiple hemorrhagic lesions of the brain and are areas with serious imaging deformation under the arrangement of electrodes of a common EIT technology;
step two, determining the position of the lesion according to the early CT or MRI image of the cerebral hemorrhage patient, and judging the region where the lesion is located according to the division in the step one;
step three, respectively placing one electrode as a fixed electrode at the center of the front extra periphery and the center of the periphery of the back pillow on a horizontal plane 3cm above the double eyebrows, and placing the other n-2 electrodes at intervals of arc length
Placing, wherein c is the perimeter of the cranium of the patient on the horizontal plane, and n is the number of electrodes;
step four, calculating and retaining the relative sensitivity RS of the region where the lesion is located, reconstructing an image, calculating and retaining the position offset PE:
SΩiexpressing the sensitivity value of pixel points in the omega i region, expressing the sensitivity value of pixel points in the whole brain region by S, wherein the value range of i is 1 or 3, and Xm、YmRespectively representing the X-axis coordinate and the Y-axis coordinate of the pixel points with the conductivity more than or equal to 50% of the maximum conductivity in all the pixel points of the reconstructed image, q representing the number of the pixel points with the conductivity more than or equal to 50% of the maximum conductivity in all the pixel points of the reconstructed image, and X, Y respectively representing the X-axis coordinate and the Y-axis coordinate of the geometric center of the lesion on the CT or MRI image;
the calculation formula of the sensitivity value of the pixel point is as follows:
wherein i and j represent the ith row and the jth column of the sensitivity pixel,
respectively indicate that the excitation current of the ith electrode group and the jth electrode group is Ii，IjA gradient of a potential distribution of the time-field domain;
and step five, respectively carrying out corresponding electrode position optimization on the n electrodes according to different regions, calculating a sensitivity matrix by adopting a relative excitation mode and carrying out image reconstruction, wherein the specific steps are as follows:
(5.1) if the lesion area is in the range of omega 1, carrying out the following steps:
step 5.11, selecting a pair of electrodes which are symmetrical left and right by taking a connecting line of the fixed electrodes as a symmetrical axis;
step 5.12, moving the selected electrode, calculating and reserving RE and PE values;
step 5.13, judging whether the unselected electrode pairs are smaller than
If yes, retaining all positions of the selected electrode pairs from the two ears of the head to the back pillow and corresponding RS and PE data, removing the rest data, and if not, not operating;
5.14, screening the optimal electrode position according to the RS and PE values;
step 5.15, fixing the selected electrode pair to the optimal electrode position, circularly performing the step 5.11 to the step 5.15, and then performing selection and optimization on the electrode pair until all the electrodes are fixed to the optimal electrode position, and finishing the regional optimization;
(5.2) if the lesion area is within the range of omega 2, not adjusting;
(5.3) if the lesion area is within the range of omega 3, performing the following steps:
step 5.31, selecting a pair of electrodes which are symmetrical left and right by taking a connecting line of the fixed electrodes as a symmetrical axis;
step 5.32, moving the selected electrode, calculating and reserving RE and PE values;
step 5.33, judge whether the unselected electrode couple is smaller than
If yes, retaining all positions from the forehead to the two ears of the head and corresponding RS and PE data of the selected electrode pair, and removing the rest data, otherwise, not operating;
step 5.34, screening the optimal electrode position according to the RS and PE values;
and 5.35, fixing the selected electrode pair to the optimal electrode position, circularly performing the steps 5.31-5.35, and then selecting and optimizing the electrode pair until all the electrodes are fixed to the optimal electrode position, and finishing the regional optimization.
2. The electrode arrangement method for long-term high-precision EIT detection of lesion sites of patients with cerebral hemorrhage according to claim 1, wherein the electrode arrangement method comprises the following steps: the number of electrodes n ranges from 8, 10, 12, 14, 16 or 18.
3. The electrode arrangement method for long-term high-precision EIT detection of lesion sites of patients with cerebral hemorrhage according to claim 1, wherein the specific process of the relative excitation mode is as follows: the forehead fixing electrode is used as the No. 1 electrode, the N electrodes are arranged in a reverse time mode, the first excitation is used for injecting current into the No. 1 electrode,
the signal electrode, namely the rear pillow fixed electrode, is used as a current loop; the second excitation injects current into the No. 2 electrode,
the signal electrode, namely the rear pillow fixed electrode, is used as a current loop; by analogy, when the serial number of the electrode serving as a current loop exceeds n, the serial number is continued from 1 until the n electrode injects current,
the excitation is finished when the signal electrode is used as a current loop, so that the length of the connecting line of all the injected currents and the electrode pair used as the current loop is close to the longest diameter of the head, the current can conveniently penetrate through the skull, and the best effect is obtained.
4. The electrode arrangement method for long-term high-precision EIT detection of lesion sites of patients with cerebral hemorrhage according to claim 1, wherein the sensitivity matrix comprises the following specific processes: the brain region is modeled by using a finite element method and is divided into a finite number of grids, each grid is a pixel point, the sensitivity of each grid to the conductivity change is calculated, and the higher the sensitivity is, the larger the conductivity change is.
5. The electrode arrangement method for long-term high-precision EIT detection of lesion sites of patients with cerebral hemorrhage according to claim 1, wherein the image reconstruction comprises the following steps: in each imaging, n electrodes distributed around the head of a cerebral hemorrhage patient are utilized, safe current is sequentially injected from a forehead fixed electrode in a counterclockwise mode, measuring voltages are respectively obtained from the electrodes except an exciting electrode and the electrodes serving as current loop electrodes in a counterclockwise mode, and the conductivity change of the brain is inverted by utilizing a sensitivity matrix obtained by a corresponding finite element model, namely image reconstruction is carried out.
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