A monitoring electrode setting method for parietal and temporal lobe lesions

Abstract

The present invention discloses a monitoring electrode setting method for parietal and temporal lobe lesions. The method utilizes the characteristic that the change of internal impedance of an object will be presented in the change of electrode potential, and optimizes the corresponding monitoring electrodes for the lesions occurring in the parietal and temporal lobes; adopts a relative excitation mode, collects boundary voltage, and performs basic imaging; determines the current lesion position according to basic imaging, and then sets the main electrode and the auxiliary electrode according to the different areas where the lesions are located, and closely arranges the remaining electrodes on both sides of the main electrode to maximize the relative sensitivity of the target area; then selects the electrode pair in turn, moves the electrode pair to the auxiliary electrode, and screens the optimal electrode pair position according to the imaging quality based on RS, BR, and PE, and fixes the electrode pair to the optimal electrode pair position. The present invention optimizes the imaging results of high-probability locations of brain lesions and provides high-quality visualization distribution of internal conductivity of the head.

Description

Technical Field

[0001] The invention belongs to the technical field of application of electrical tomography in brain lesion detection, and specifically is a monitoring electrode setting method for parietal lobe and temporal lobe lesions. Background Art

[0002] Electrical tomography (ET) is a soft field imaging technology. Its principle is to use electrodes installed on the surface of an object to regularly apply excitation to it. If there is a certain impedance change inside the object, it will cause a certain potential change on the measuring electrode. By performing certain mathematical operations on the potential change, the internal impedance change can be inferred, thereby visualizing the inside of the object. Electrical capacitance tomography (ECT), electrical resistance tomography (ERT) and electromagnetic tomography (EMT) are the three basic imaging forms of electrical tomography, on which the electrical impedance tomography (EIT) technology is derived. EIT technology has very attractive prospects in medical testing because it is non-invasive, radiation-free and low-cost. It has good application prospects in lung lesion detection, brain lesion detection, breast cancer detection, and abdominal organ function imaging. T Dowrick et al. published an article titled 'In vivo bioimpedance changes during haemorrhagic and ischaemic stroke in rats: towards 3D stroke imaging using electrical impedance tomography' in Physiological Measurement, Vol. 37, pp. 765-784, in 2016. The article used EIT differential imaging to conduct real experiments and reconstruct images on rat hemorrhage and ischemia models. The results confirmed the feasibility and accuracy of EIT in brain experiments.YD Li et al. published an article titled "In vivo Detection and Imaging of Intraventricular Hemorrhage in Neonatal Piglets Using Electrical Impedance Tomography" in Volume 27, No. 2 of the Chinese Journal of Biomedical Engineering in 2018. The article also used differential imaging and a relative excitation adjacent measurement mode. Because the head is irregular in shape and the skull is highly non-conductive, it is difficult for the current to penetrate and reach the central area of ​​the brain if the conventional adjacent excitation mode is used. The above experiments all used an electrode setting with 16 electrodes evenly arranged. The results of this electrode arrangement can detect bleeding and ischemic sites, but due to the presence of many artifacts, the size and shape of the lesion cannot be accurately determined. The experiment showed that among patients with cerebral hemorrhage, 14% of the bleeding sites were in the frontal lobe, 7% in the parietal lobe, 48% in the temporal lobe, and 31% in the occipital lobe. It can be seen from this that the probability of cerebral hemorrhage in the temporal lobe and parietal lobe is as high as 55%. However, due to the relative excitation mode and the influence of uniform electrode arrangement, the imaging results when the lesions are located in these two parts are poor, and they need to be optimized to ensure image quality, thereby making EIT more advantageous in brain lesion detection. Summary of the invention

[0003] The technical problem solved by the present invention is to propose a monitoring electrode setting method for parietal and temporal lobe lesions. The method utilizes the fact that changes in the internal impedance of an object will be reflected in the potential changes of the electrodes. By changing the arrangement of the electrodes, the potential change information is all from the parietal and temporal lobe parts, that is, the area from the temples on both sides to behind the ears on both sides, thereby reducing irrelevant signals and improving imaging quality.

[0004] The present invention adopts the following technical solution to solve the above technical problems, a method for setting monitoring electrodes for parietal and temporal lobe lesions, characterized by the following specific steps:

[0005] Step 1: With the human body standing and the head vertically upward, make plane 1 and plane 2 perpendicular to the ground. The line connecting the temples on both sides of the skull is on plane 1; the line connecting the back of the left ear and the back of the right ear is on plane 2. The area between plane 1 and plane 2 is set as the area to be optimized. Make plane 3 perpendicular to the line connecting the left ear and the right ear, starting from the left ear and moving to the right ear. The intersection of the area scanned during the movement and the area to be optimized is the α1 area. Continue to move the plane three times to the right ear. The intersection of the area scanned during the movement and the area to be optimized is the α2 area, and then continue to move the plane three times to the right ear. The intersection of the area swept during the movement and the area to be optimized is the α3 area, where c is the length of the line segment connecting the left ear to the right ear;

[0006] Step 2: Place an electrode as a reference electrode 6 cm above the left ear and right ear of the patient, and fix the remaining electrodes at intervals of 10 cm on a horizontal plane parallel to the ground where the reference electrode is located. Placed around the patient's head, where D is the circumference of the patient's head and n is the number of electrodes;

[0007] Step 3: Using relative excitation mode, collecting boundary voltage and performing basic imaging;

[0008] The relative excitation mode is to select any electrode as the excitation electrode to inject the excitation current, and select the electrode spaced counterclockwise from the excitation electrode. The electrode of each electrode is grounded as the ground electrode. After obtaining the point information on the electrodes other than the excitation and ground electrodes, the next electrode is selected counterclockwise as the excitation electrode. The ground electrode still maintains a counterclockwise interval with the new excitation electrode. Electrodes are selected until all electrodes have been selected as excitation electrodes and the potential information on the remaining electrodes has been obtained, and then the excitation is terminated;

[0009] Step 4: According to the basic imaging, determine the current lesion position, calculate and retain the relative sensitivity RS, position offset PE, and blur radius BR;

[0010]

[0011]

[0012]

[0013] Among them, S αi represents the sensitivity value of the pixel in the αi area, S represents the sensitivity value of the pixel in the entire brain area, and the value range of i is 1 or 3;

[0014] X t , Y t represent the X-axis coordinate and Y-axis coordinate of the pixel points whose conductivity is greater than or equal to 50% of the maximum conductivity among all the pixel points of the reconstructed image, respectively; P represents the number of pixel points whose conductivity is greater than or equal to 50% of the maximum conductivity among all the pixel points of the reconstructed image;

[0015] X and Y represent the X-axis coordinate and Y-axis coordinate of the geometric center of the lesion on the basic imaging image, respectively;

[0016] R t Indicates the radius of the lesion, A t Represents the area of ​​the lesion, R represents the radius of the entire imaging area, A represents the area of ​​the entire imaging area, and the BR value reflects the accuracy of the reconstructed image. The smaller the BR value, the more accurate the imaging target and the fewer artifacts.

[0017] Step 5: determine whether the lesion position in the image is in the α2 area, that is, in the geometric center of the brain. If so, in order to ensure sufficient current penetration effect, the electrode position is not adjusted and all steps are ended. If not, proceed to step 6;

[0018] Step 6: The two reference electrodes are fixed, the reference electrode closest to the lesion area is set as the main electrode, and the other reference electrode is set as the secondary electrode. All electrodes except the main and secondary electrodes are divided into two groups. One group starts with the main electrode and is placed counterclockwise on the outside of the scalp at the same height as the main electrode with the interval e between the edges of adjacent electrodes. The other group of electrodes starts with the main electrode and is placed clockwise on the outside of the scalp at the same height as the main electrode with the interval e between the edges of adjacent electrodes. RS, PE, and BR values ​​are calculated and saved, where e is the length of a single electrode.

[0019] Step 7: Select a pair of symmetrical electrodes with the main and auxiliary electrodes as symmetry axes, starting from the electrode pair closest to the auxiliary electrode and moving toward the electrode pair closest to the main electrode;

[0020] Step 8: Move the selected electrode pair toward the secondary electrode with a moving step of 2 mm. Calculate and retain the RS, PE, and BR values ​​after each move. Determine whether the RS value saved each time is greater than the RS value of the basic imaging. If so, do not perform other operations. If not, delete the position data and RS, PE, and BR values ​​of the move before continuing to move. The constraint condition of the move is: the spacing between adjacent edges of any electrode cannot be less than e.

[0021] Step 9: Filter the minimum position among all saved BR values, and determine whether the PE value is the minimum value or less than 0.5 mm at the current position. If so, select the position as the current optimal electrode pair position; if not, delete the position data, repeat this step, filter the new BR minimum position, until the optimal electrode pair position is obtained;

[0022] Step 10: fix the selected electrode pair to the optimal position, delete the data saved when the electrode pair is moved, repeat steps 7 to 9, select the electrode pair again and fix it to the optimal position, until all electrode pairs are fixed, and the optimization is finished.

[0023] It is further defined that the number of electrodes n is in the range of 8, 10, 12, 14, 16 or 18.

[0024] Further defined, imaging is specifically to use the measured potential information and the known normal brain conductivity distribution to obtain the sensitivity of each part of the object to the change of potential information, that is, Ag = b, where A is the sensitivity, b is the potential information, and g is the conductivity. The conductivity information can be obtained by using this sensitivity and the potential information obtained after the internal conductivity changes, that is, g = A -1 b. The conductivity obtained is colored according to the numerical value to form an image.

[0025] To further define, pixel points are specifically used to divide and model the brain area using the finite element method, that is, to divide it into a finite number of small grids, and solve the Maxwell equations corresponding to each small grid column. Each grid is a pixel point. The more pixel points means the higher the resolution and the more accurate the solution.

[0026] The present invention has the following beneficial effects: for parietal and temporal lobe lesions, the present invention places all non-reference electrodes on the reference electrode side closest to the lesion site to maximize the relative sensitivity of the lesion area, and then moves the electrodes to another reference electrode to meet the imaging requirements, and uses the fuzzy radius and position offset to judge the imaging results and determine the optimal electrode position. This method covers all possible positions of the electrode, provides conditions for high-precision imaging, optimizes the imaging results of high-probability positions of brain lesions, and can better judge the current condition and visualize it. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a top view schematic diagram of the excitation mode, measurement mode, α1, α2, α3 partitions, and the final electrode distribution optimized for the α1 region of the present invention.

[0028] Figure 2 The present invention is a flow chart of a method for setting monitoring electrodes for parietal and temporal lobe lesions.

[0029] Figure 3 The maximum relative sensitivity of the present invention is compared with that of uniformly arranged electrodes in the α1, α2, and α3 zones.

[0030] Figure 4 The imaging comparison between the present invention and the uniformly arranged electrodes under six different lesions in the α1 region.

[0031] Figure 5 The figure is a bar graph comparing the blur radius of the present invention and the uniformly arranged electrodes under six different pathological conditions in the α1 region. DETAILED DESCRIPTION

[0032] A monitoring electrode setting method for parietal lobe and temporal lobe lesions of the present invention is described in detail with reference to the accompanying drawings and embodiments.

[0033] The purpose of the monitoring electrode setting method for parietal and temporal lobe lesions described in the present invention is to further optimize the images of the parietal and temporal lobe lesion locations. Since the parietal and temporal lobes are located in the middle of the head from the temples on both sides to behind the ears on both sides, the sensitivity of uniform electrode arrangement here is already high, and it is difficult to optimize using conventional methods. The present invention utilizes the property that changes in the internal impedance of an object will be reflected in changes in the potential of the electrode. By placing the electrodes compactly, the sensitivity of the target area is maximized first, and then the electrode position is changed according to the imaging quality. Figure 1 The relative excitation adjacent measurement mode is shown, allowing the current to penetrate the skull. Figure 1 The right side shows the α1, α2, and α3 divisions for the parietal and temporal lobes, as well as the electrode optimization results when the lesion is in the α1 region. 1 is the excitation current, 2 is the measurement voltage, 3 is the electrode, 4 is the forehead direction, 5 is the occipital direction, 6 is the left ear direction, 7 is the right ear direction, 8 is plane 1, and 9 is plane 2.

[0034] The specific optimization steps are as follows: Figure 2 As shown in the process, it is divided into the following steps:

[0035] Step 1: With the human body standing and the head vertically upward, make plane 1 and plane 2 perpendicular to the ground. The line connecting the temples on both sides of the skull is on plane 1; the line connecting the back of the left ear and the back of the right ear is on plane 2. The area between plane 1 and plane 2 is set as the area to be optimized. Make plane 3 perpendicular to the line connecting the left ear and the right ear, starting from the left ear and moving to the right ear. The intersection of the area scanned during the movement and the area to be optimized is the α1 area. Continue to move the plane three times to the right ear. The intersection of the area scanned during the movement and the area to be optimized is the α2 area, and then continue to move the plane three times to the right ear. The intersection of the area swept during the movement and the area to be optimized is the α3 area, where c is the length of the line segment connecting the left ear to the right ear;

[0036] Step 2: Place an electrode as a reference electrode 6 cm above the left ear and right ear of the patient, and fix the remaining electrodes at intervals of 10 cm on a horizontal plane parallel to the ground where the reference electrode is located. Placed around the patient's head. Where D is the circumference of the patient's head, n is the number of electrodes, and the value range of the number of electrodes n is 8, 10, 12, 14, 16 or 18.

[0037] Step 3: Using relative excitation mode, collecting boundary voltage and performing basic imaging;

[0038] The relative excitation mode is to select any electrode as the excitation electrode to inject the excitation current, and select the electrode spaced counterclockwise from the excitation electrode. The electrode of each electrode is grounded as the ground electrode. After obtaining the potential information on the electrodes other than the excitation and ground electrodes, the next electrode is selected counterclockwise as the excitation electrode. The ground electrode is still kept counterclockwise from the new excitation electrode. Electrodes are selected until all electrodes have been selected as excitation electrodes and the potential information on the remaining electrodes has been obtained, and then the excitation is terminated;

[0039] Specifically, imaging uses the measured potential information and the known normal brain conductivity distribution to obtain the sensitivity of each part of the object to the change of potential information, that is, Ag = b, where A is the sensitivity, b is the potential information, and g is the conductivity. Using this sensitivity and the potential information obtained after the internal conductivity changes, the conductivity information can be obtained, that is, g = A -1 b, the conductivity obtained is colored according to the numerical value to form an image;

[0040] Step 4: According to the basic imaging, determine the current lesion position, calculate and retain the relative sensitivity RS, position offset PE, and blur radius BR;

[0041]

[0042]

[0043]

[0044] Among them, S αi represents the sensitivity value of the pixel in the αi area, S represents the sensitivity value of the pixel in the entire brain area, and the value range of i is 1 or 3;

[0045] X t , Y t represents the X-axis coordinate and Y-axis coordinate of the pixel whose conductivity is greater than or equal to 50% of the maximum conductivity among all the pixels of the reconstructed image, P represents the number of the pixel whose conductivity is greater than or equal to 50% of the maximum conductivity among all the pixels of the reconstructed image, and X and Y represent the X-axis coordinate and Y-axis coordinate of the geometric center of the lesion on the basic imaging image, respectively;

[0046] R t Indicates the radius of the lesion, A t Represents the area of ​​the lesion, R represents the radius of the entire imaging area, A represents the area of ​​the entire imaging area, and the BR value reflects the accuracy of the reconstructed image. The smaller the BR value, the more accurate the imaging target and the fewer artifacts.

[0047] Specifically, the pixel point is to use the finite element method to segment and model the brain area, that is, to divide it into a finite number of small grids, and solve the grid information for the Maxwell equations corresponding to each small grid column. Each grid is a pixel point. The more pixel points means the higher the resolution and the more accurate the solution.

[0048] Step 5: determine whether the lesion position in the image is in the α2 area, that is, in the geometric center of the brain. If so, in order to ensure sufficient current penetration effect, the electrode position is not adjusted and all steps are ended. If not, proceed to step 6;

[0049] Step 6: The two reference electrodes are fixed, the reference electrode closest to the lesion area is set as the main electrode, and the other reference electrode is set as the secondary electrode. All electrodes except the main and secondary electrodes are divided into two groups. One group starts with the main electrode and is placed counterclockwise on the outside of the scalp at the same height as the main electrode with the interval e between the edges of adjacent electrodes. The other group of electrodes starts with the main electrode and is placed clockwise on the outside of the scalp at the same height as the main electrode with the interval e between the edges of adjacent electrodes. RS, PE, and BR values ​​are calculated and saved, where e is the length of a single electrode.

[0050] Step 7: Select a pair of symmetrical electrodes with the main and auxiliary electrodes as symmetry axes, starting from the electrode pair closest to the auxiliary electrode and moving toward the electrode pair closest to the main electrode;

[0051] Step 8: Move the selected electrode pair toward the secondary electrode with a moving step of 2 mm. Calculate and retain the RS, PE, and BR values ​​after each move. Determine whether the RS value saved each time is greater than the RS value of the basic imaging. If so, do not perform other operations. If not, delete the position data and RS, PE, and BR values ​​of the move before continuing to move. The constraint condition of the move is: the spacing between adjacent edges of any electrode cannot be less than e.

[0052] Step 9: Filter the minimum position among all saved BR values, and determine whether the PE value is the minimum value or less than 0.5 mm at the current position. If so, select the position as the current optimal electrode pair position; if not, delete the position data, repeat this step, filter the new BR minimum position, until the optimal electrode pair position is obtained;

[0053] Step 10: fix the selected electrode pair to the optimal position, delete the data saved when the electrode pair is moved, repeat steps 7 to 9, select the electrode pair again and fix it to the optimal position, until all electrode pairs are fixed, and the optimization is finished.

[0054] like Figure 3As shown, the optimal relative sensitivity of the present invention and the uniformly arranged electrodes in the α1, α2, and α3 regions. It can be seen that the present invention has obvious numerical advantages in the α1 and α3 regions, which proves that the electrodes arranged by this method can effectively improve the relative sensitivity.

[0055] like Figure 4 The figure shows the imaging effects of six different lesions in the α1 region, including three locations of bleeding and three locations of bleeding accompanied by secondary ischemia. Referring to the real human tissue parameters, the brain background conductivity is 0.15S / m, which is the conductivity of human cerebrospinal fluid. The bleeding conductivity is set to 0.8S / m (both on the left) and the ischemic conductivity is set to 0.06S / m (both on the right). It can be seen that the imaging of the second row of uniform electrodes arranged in this area has a good imaging quality, but when it is close to the edge and accompanied by secondary ischemia, the imaging still has certain deformation and deviation. The images formed by the third row of the present invention maintain good imaging quality at all positions without obvious deformation, which can provide better guidance for the diagnosis and treatment of the disease.

[0056] like Figure 5 The figure shows the comparison of BR values ​​under the above six different lesions. The BR values ​​of the present invention under different lesions at various locations are small and stable, with only a certain increase at F, but still smaller than the BR value of the uniformly arranged electrodes. In summary, the electrode arrangement optimized by the present invention can well improve the relative sensitivity of the area to be optimized, thereby improving the imaging quality and better judging the current lesion condition.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for setting monitoring electrodes for parietal and temporal lobe lesions, characterized in that The specific steps are as follows: Step 1: With the human body standing and the head vertically upward, make plane 1 and plane 2 perpendicular to the ground. The line connecting the temples on both sides of the skull is on plane 1; the line connecting the back of the left ear and the back of the right ear is on plane 2. The area between plane 1 and plane 2 is set as the area to be optimized. Make plane 3 perpendicular to the line connecting the left ear and the right ear, starting from the left ear and moving to the right ear. The intersection of the area scanned during the movement and the area to be optimized is the α1 area. Continue to move the plane three times to the right ear. The intersection of the area scanned during the movement and the area to be optimized is the α2 area, and then continue to move the plane three times to the right ear. The intersection of the area swept during the movement and the area to be optimized is the α3 area, where c is the length of the line segment connecting the left ear to the right ear; Step 2: Place an electrode as a reference electrode 6 cm above the left ear and right ear of the patient, and fix the remaining electrodes at intervals of 10 cm on a horizontal plane parallel to the ground where the reference electrode is located. Placed around the patient's head, where D is the circumference of the patient's head and n is the number of electrodes; Step 3: Using relative excitation mode, collecting boundary voltage and performing basic imaging; The relative excitation mode is to select any electrode as the excitation electrode to inject the excitation current, and select the electrode spaced counterclockwise from the excitation electrode. -1 electrode is grounded as the ground electrode. After obtaining the point information on the electrodes other than the excitation and ground electrodes, the next electrode is selected counterclockwise as the excitation electrode. The ground electrode still maintains a counterclockwise interval with the new excitation electrode. -1 electrode, until all electrodes have been selected as excitation electrodes and the potential information on the remaining electrodes has been obtained, then the excitation is terminated; Step 4: According to the basic imaging, determine the current lesion position, calculate and retain the relative sensitivity RS, position offset PE, and blur radius BR; Among them, S αi represents the sensitivity value of the pixel in the αi area, S represents the sensitivity value of the pixel in the entire brain area, and the value range of i is 1 or 3; X t , Y t represent the X-axis coordinate and Y-axis coordinate of the pixel points whose conductivity is greater than or equal to 50% of the maximum conductivity among all the pixel points of the reconstructed image, respectively; P represents the number of pixel points whose conductivity is greater than or equal to 50% of the maximum conductivity among all the pixel points of the reconstructed image; X and Y represent the X-axis coordinate and Y-axis coordinate of the geometric center of the lesion on the basic imaging image, respectively; R t Indicates the radius of the lesion, A t Represents the area of ​​the lesion, R represents the radius of the entire imaging area, A represents the area of ​​the entire imaging area, and the BR value reflects the accuracy of the reconstructed image. The smaller the BR value, the more accurate the imaging target and the fewer artifacts. Step 5: determine whether the lesion position in the image is in the α2 area, that is, in the geometric center of the brain. If so, in order to ensure sufficient current penetration effect, the electrode position is not adjusted and all steps are ended. If not, proceed to step 6; Step 6: The two reference electrodes are fixed, the reference electrode closest to the lesion area is set as the main electrode, and the other reference electrode is set as the secondary electrode. All electrodes except the main and secondary electrodes are divided into two groups. One group starts with the main electrode and is placed counterclockwise on the outside of the scalp at the same height as the main electrode with the interval e between the edges of adjacent electrodes. The other group of electrodes starts with the main electrode and is placed clockwise on the outside of the scalp at the same height as the main electrode with the interval e between the edges of adjacent electrodes. RS, PE, and BR values ​​are calculated and saved, where e is the length of a single electrode. Step 7: Select a pair of symmetrical electrodes with the main and auxiliary electrodes as symmetry axes, starting from the electrode pair closest to the auxiliary electrode and moving toward the electrode pair closest to the main electrode; Step 8: Move the selected electrode pair toward the secondary electrode with a moving step of 2 mm. Calculate and retain the RS, PE, and BR values ​​after each move. Determine whether the RS value saved each time is greater than the RS value of the basic imaging. If so, do not perform other operations. If not, delete the position data and RS, PE, and BR values ​​of the move before continuing to move. The constraint condition of the move is: the spacing between adjacent edges of any electrode cannot be less than e. Step 9: Filter the minimum position among all saved BR values, and determine whether the PE value is the minimum value or less than 0.5 mm at the current position. If so, select the position as the current optimal electrode pair position; if not, delete the position data, repeat this step, filter the new BR minimum position, until the optimal electrode pair position is obtained; Step 10: fix the selected electrode pair to the optimal position, delete the data saved when the electrode pair is moved, repeat steps 7 to 9, select the electrode pair again and fix it to the optimal position, until all electrode pairs are fixed, and the optimization is finished.

2. The method for setting monitoring electrodes for parietal and temporal lobe lesions according to claim 1, characterized in that: The number of electrodes n ranges from 8, 10, 12, 14, 16 or 18.

3. The method for setting monitoring electrodes for parietal and temporal lobe lesions according to claim 1, characterized in that The imaging is specifically as follows: using the measured potential information and the known normal brain conductivity distribution to obtain the sensitivity of each part of the object to the change of potential information, that is, Ag = b, where A is the sensitivity, b is the potential information, and g is the conductivity. Using this sensitivity and the potential information obtained after the internal conductivity changes, the conductivity information can be obtained, that is, g = A -1 b. The conductivity obtained is colored according to the numerical value to form an image.

4. The method for setting monitoring electrodes for parietal and temporal lobe lesions according to claim 1, characterized in that Specifically, pixel points are: the finite element method is used to segment and model the brain area, that is, it is divided into a finite number of small grids, and the Maxwell equations corresponding to each small grid column are solved to obtain the grid information. Each grid is a pixel point. The more pixel points means the higher the resolution and the more accurate the solution.

Images