CN114469155A - Control method for spiral CT scanning - Google Patents

Abstract

The invention provides a control method of a spiral CT device, which comprises: receiving sign data of a scanned object; formulating a first scanning plan according to the sign data; performing CT scanning on the scanned object according to the first scanning plan to obtain the first scanning plan. a projection data, the first projection data includes the projection data that has been acquired and the projection data to be acquired under the first scanning plan; the first projection data is used to check according to the image reconstruction check rule; the check result is checked according to specific conditions Evaluate, if the evaluation result satisfies the specific condition, maintain the first scan plan, if the evaluation result does not satisfy the specific condition, generate the second scan plan and continue to perform CT scanning on the scanned object according to the second scan plan, and obtain the second projection data, wherein the specific condition is whether the first projection data is sufficient or redundant for image reconstruction; and, image reconstruction is performed according to the first projection data or/and the second projection data.

Description

A control method of helical CT scan

Division description

This application is a divisional application filed against a Chinese application with an application date of May 31, 2017, an application number of 201710402065.2, and the name of the invention is a control method for helical CT scanning.

technical field

The present invention relates to a medical imaging system, in particular to a control method of helical CT scanning.

Background technique

Variable pitch helical CT scanning is a major breakthrough in X-ray imaging technology. It can adjust the pitch at any time according to specific conditions to obtain the best image reconstruction quality. In the diagnosis of medical lesions, according to the needs of diagnosis, when selecting different slice thicknesses for helical scanning, select the appropriate helical pitch and reconstruction interval to obtain better image quality. For example, when scanning the whole body of a patient, a large pitch can be used for normal parts, and a small pitch can be used for lesions, which can shorten the scanning time and reduce the radiation dose. At the same time, the variable pitch helical scanning combined with ECG gating, ECG triggering, respiratory gating and other technologies can effectively reduce artifacts.

The problem with the prior art is that it is impossible to specify which path is more suitable for scanning different parts. The practice in the prior art is to plan an ideal path considering the error when making the scan plan, and then perform the scan according to the original scan plan during execution, without adjusting the scan plan based on the actual situation. In this way, there will be a contradiction. If the error tolerance set aside in advance is small, it is difficult to ensure that it is within the error range during actual execution. Utilization will not be significantly improved.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention provides a control method for a spiral CT device, which can solve the above problems.

The present invention provides a control method of a spiral CT device, comprising: receiving sign data of the scanned object; formulating a first scanning plan according to the sign data; performing CT on the scanned object according to the first scanning plan scan to obtain first projection data; use the first projection data to check according to the image reconstruction check rule; evaluate the result of the check according to a specific condition, and if the evaluation result satisfies the specific condition, maintain the The first scan plan, if the evaluation result does not meet the specific condition, generate a second scan plan and continue to perform CT scanning on the scanned object according to the second scan plan, and acquire the second projection data; and, performing image reconstruction according to the first projection data or/and the second projection data;

In the present invention, the sign data includes an electrocardiogram signal or a breathing signal;

In the present invention, the specific condition is whether the first projection data of the first scanning plan is sufficient or redundant for image reconstruction;

In the present invention, the judgment rule of the specific condition is: parse out the slice position information of the first projection data, scan the bed code information, the encoder angle information, and arrange the data; The position information and the scanning bed code information are used to calculate the physical position range that the current first projection data can support; the encoder angle information is counted in each physical position range to determine whether the angle information covered by the encoder conforms to the current scan and reconstruction. to determine whether the first projection data is sufficient or redundant;

In the present invention, the first projection data or the second projection data is the projection data that has been acquired and will be acquired under the first scanning plan or the second scanning plan;

In the present invention, the second scan plan is to acquire more projection data than the first scan plan, or less projection data than the first scan plan;

In the present invention, the first scan plan or the second scan plan includes setting the rotational speed of the gantry;

In the present invention, the first scanning plan or the second scanning plan includes setting the moving speed of the scanning bed;

In the present invention, the first scan plan or the second scan plan includes setting the width of the collimator;

In the present invention, the first scan plan or the second scan plan includes adjusting the X-ray beam.

The present invention provides a control method for a spiral CT device, comprising: receiving sign data of the scanned object; formulating a scanning plan according to the sign data; performing CT scanning on the scanned object according to the scanning plan to obtain projection data; analyze the projection data to determine whether the scanning plan meets the requirements, if it meets the requirements, continue scanning according to the established scanning plan; if it does not meet the requirements, adjust the scanning plan, and according to the adjusted The scan plan continues scanning.

In the present invention, analyzing the projection data includes judging whether the projection data is sufficient or redundant for image reconstruction.

In the present invention, the adjustment of the scanning plan includes adjusting the rotation speed of the gantry, adjusting the moving speed of the scanning bed, adjusting the width of the collimator, or adjusting the X-ray beam.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present disclosure more clearly, the following briefly introduces the accompanying drawings that are used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

1 is a schematic structural diagram of a spiral CT system of the present invention;

Fig. 2 is the exemplary flow chart of the spiral CT scan image reconstruction of the present invention;

FIG. 3 is a flow chart of an embodiment of the reconstruction of a spiral CT scan image according to the present invention.

Detailed ways

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

In order to fully understand the present invention, please refer to FIG. 1 , which shows a schematic structural diagram of a spiral CT system according to a preferred embodiment of the present invention. The CT system includes, but is not limited to, a CT tube 101 , a collimator 102 , a detector 104 , a high voltage generator 105 , a collimator driver 106 , a rotation driver 107 , a position controller 108 , a vital signal unit 109 , and a scan planning unit 110 , an image reconstruction unit 112 , an acquisition unit 113 and a scanning bed 114 .

The high-voltage generator 105 is used to receive commands from the scan planning unit 110 and control the operation of the CT tube 101 . The CT tube 101 is used to provide X-rays 103 . After passing through the collimator 102, the X-rays pass through the scanned object on the scanning bed 114 and are partially attenuated. The detector 104 receives the partially attenuated X-ray signal and converts it into a corresponding electrical signal. The detectors 104 are installed inside the metal base, and are installed on opposite sides of the gantry with the CT tube 101 . The collimator 102 is used to define the thickness of the X-rays. The detector 104 may include scintillation crystals arranged in an array, an ASIC (Application Specific Integrated Circuit) chip located under the scintillation crystals, and a chip substrate of the scintillation crystals.

The acquisition unit 113 connected to the detector 104 system acquires the electrical signal output by the detector 104 . For example, the detector 104 includes an ASIC chip that can convert the received X-ray signals into corresponding electrical signals. The above-mentioned electrical signals are converted into digital signals (projection data) by an A/D converter. The image reconstruction unit 112 is connected to the acquisition unit 113 to receive projection data. The image reconstruction unit 112 performs data compression and/or reformatting on the received projection data, and then stores (eg, into a cache) and/or further processes the processed data. The back-projection controller in the image reconstruction unit 112 may distribute the projection data to the various units of the back-projection plate. The data contained in each back-projection unit can be from one projection to six projections, and are stored at the same time, and then the image data and the results of each back-projection unit are transmitted to each back-projection plate for summation to synthesize pixel data , the tomographic image can be reconstructed and displayed on a display (not shown in FIG. 1 ) or stored on a storage device.

In some embodiments, the image reconstruction unit 112 may check the projection data obtained by the current CT system according to the image reconstruction check rule, and feed back the check result to the scan planning unit 110 . In some embodiments, the image reconstruction check rule may be determined by determining whether the projection data of the first scan plan (including the projection data already acquired and the projection data to be acquired under the first scan plan) meet certain conditions. In some embodiments, whether the projection data meets a certain condition may be whether the projection data is sufficient or redundant. In some embodiments, the inspection rules are as follows, the image reconstruction unit 112 can parse out the slice position information of the projection data, the scanning bed code information, the encoder angle information, and arrange the data; then, the image The reconstruction unit 112 calculates the physical position range that the current projection data can support based on the slice position information and the scan bed code information; finally, the image reconstruction unit 112 performs statistics on the encoder angle information within each physical position range to determine whether the encoder covers The angle information of the current projection complies with the angle range requirements of the current scan and reconstruction, and it is judged whether the current projection data can reconstruct an image that meets the requirements.

For example, when scanning the heart, the scan planning unit 110 formulates and executes the first scan plan. At a certain moment, if the image reconstruction unit 112 judges the projection data (included in the first scan plan) acquired under the first scan plan according to the image reconstruction check rule If the projection data acquired under the scan plan and the projection data to be acquired) cannot reconstruct an image that meets the requirements, that is, the projection data acquired under the current scan plan is insufficient, the image reconstruction unit 112 can transmit the inspection result to the scan plan unit 110 to generate and execute the second scan plan, to obtain other projection data for reconstructing the image that meets the requirements; at a certain moment, if the image reconstruction unit 112 judges the projection data obtained under the first scan plan (( Including the projection data that has been acquired under the first scan plan and the projection data to be acquired), an image that meets the requirements can be reconstructed, and there is no redundant data, that is, the projection data acquired under the current scan plan is sufficient. At this time, the image reconstruction unit 112 can send a signal to the scan planning unit 110 to continue executing the first scan plan; at a certain moment, if the image reconstruction unit 112 judges the projection data (included under the first scan plan) acquired under the first scan plan according to the image reconstruction check rules The acquired projection data and the projection data to be acquired) can reconstruct an image that meets the requirements, and there is redundant projection data, that is, the projection data acquired under the current scanning plan is redundant, then the image reconstruction unit 112 can transmit the inspection result to the scanning The planning unit 110 generates and executes the third scan plan, skips the position where the redundant projection data is generated, and stops acquiring the redundant projection data. The so-called meeting the requirements may refer to the clarity and integrity of the reconstructed image, and may also be preset according to specific conditions.

It should be noted that the first scan plan, the second scan plan and the third scan plan described in this disclosure do not specifically refer to one or several scan plans, but only to distinguish different scan plans from each other.

The CT tube 101 , the collimator 102 , and the detector 104 can be fixed on a rotating gantry (not shown in FIG. 1 ), and the rotating gantry can be driven to rotate by a rotating driver 107 . The scan planning unit 110 can control the rotation speed and rotation direction of the rotating gantry by controlling the rotation driver 107 . At the same time, the position controller 108 can drive the couch 114 to move in the z direction (perpendicular to the x and y directions, where the y direction is perpendicular to the couch and the x direction is parallel to the couch and perpendicular to the y direction, as shown in FIG. 1 ) . The scanning planning unit 110 may control the moving direction and moving speed of the scanning bed 114 through the position controller 108 . The collimator 102 is used to determine the thickness of the X-rays. The specific thickness of the X-ray is determined by the width of the collimator 102 . The scan planning unit 110 may vary the width of the collimator 102 via the collimator driver 106 .

During the scanning process, the CT tube 101 , the collimator 102 and the detector 104 can rotate in a certain direction and a certain speed under the driving of the rotating gantry, and the scanning bed 114 can move in the z direction at a certain speed. Therefore, during the scanning process, the CT tube 101 rotates around the scanned object, and at the same time, the scanned object moves forward at a constant speed under the driving of the scanning bed, so the trajectory left by the X-ray on the scanned object is a spiral curve.

The vital signal unit 109 may collect vital data of the patient, such as ECG data and respiratory data. The vital sign data that can be collected by the vital sign signal unit 109 include, but are not limited to, electrocardiographic signals and breathing signals. In some embodiments, the ECG signal may be an electrical signal generated by the beating of the heart, and may be acquired by electrodes placed on the scanned object during scanning. In some embodiments, the breathing signal may be collected by a breathing belt placed on the abdomen of the scanned object, and the collected breathing signal represents the movement of the diaphragm of the scanned object. The vital signal unit 109 may include, or be connected to, a device for collecting vital signals to obtain vital signals. In some embodiments, the image reconstruction unit 112 may selectively reconstruct images based on the vital data collected by the vital signal unit 109 . In some embodiments, the image reconstruction unit 112 may select the projection data at a certain moment for reconstruction according to the electrocardiographic signal collected by the vital signal unit 109 . For example, if a cardiac cycle is divided into 20 phases, the image reconstruction unit 112 can collect the ECG signal according to the vital signal unit 109, extract the projection data of the 20 phases respectively, and reconstruct 20 pictures corresponding to different phases respectively .

The scan planning unit 110 may formulate a scan plan. The scan plan may be the plan by which the CT system acquires projection data. In some embodiments, the scan planning unit 110 may formulate a scan plan according to the periodic vital data collected by the vital signal unit 109 . For example, according to the ECG signals collected by the vital signal unit 109, a cardiac cycle can be divided into several phases. When performing a heart scan, the scan planning unit 110 can formulate and execute a scan plan, and acquire only one or several phases. Projection data of the heart in a specific phase. The scan planning unit 110 controls one or a combination of one or more of the high voltage generator 105 , the collimator driver 106 , the rotation driver 107 , the position controller 108 and the like according to the scan plan, thereby realizing the scan plan. The scanning plan can be whether the high-voltage generator 105 works at a certain time, the width of the collimator 102 at a certain time, the rotation speed and/or rotation direction of the rotating gantry at a certain time, and the scanning plan at a certain time. The moving speed and/or moving direction of the couch 114 is scanned at all times.

In some embodiments, the scan planning unit 110 may formulate different scan plans according to different scan positions. For example, when performing a whole-body CT scan, the scan planning unit 110 may formulate a scan plan for parts that require high scan accuracy (such as the head, heart, etc.), so that the rotating speed of the rotating gantry is slower and the scanning bed 114 moves faster slow, thereby improving scanning accuracy. For parts with low scanning accuracy requirements (such as abdomen, legs, etc.), the scanning planning unit 110 can formulate a scanning plan, so that the rotating gantry rotates faster and the scanning bed 114 moves faster, so as to quickly scan these areas and reduce unnecessary radiation dose.

In some embodiments, the scan planning unit 110 may implement an updated scan plan based on feedback from the image reconstruction unit 112 . The ways of updating the scanning plan include but are not limited to: setting the rotational speed of the rotating gantry, setting the moving speed of the scanning bed 114, setting the width of the collimator 102, adjusting the X-ray beam, or any combination of the above methods. Adjusting the X-ray beam can be done by turning the beam off or on, or changing the beam size. For example, when scanning the heart, the scan planning unit 110 may formulate and execute a first scan plan, and at some point, when the image reconstruction unit 112 feeds back projection data acquired under the first scan plan (including those already acquired under the first scan plan) When the projection data and the projection data to be acquired are redundant, the scan planning unit 110 will formulate a second scan plan, including increasing the rotational speed of the rotating gantry at a certain moment, increasing the moving speed of the scanning bed 114 at a certain moment, and at a certain moment Turning off the high-voltage generator 105 at any time, or any combination of the above methods, skips the position where the redundant projection data is generated, thereby preventing the heart and/or other organs in its vicinity from receiving unnecessary radiation doses. For another example, when scanning the heart, the scan planning unit 110 may formulate and execute a first scan plan, and at a certain moment, when the image reconstruction unit 112 feeds back the projection data acquired under the first scan plan (including those already acquired under the first scan plan) When the acquired projection data and the projection data to be acquired) are not enough, the scan planning unit 110 will formulate a second scan plan, including reducing the rotational speed of the rotating gantry at a certain moment, reducing the moving speed of the scanning bed 114 at a certain moment, and at a certain moment. Turn on the high-voltage generator 105 at a moment, or any combination of the above methods, so as to obtain necessary projection data and reconstruct an image that meets the requirements.

In some embodiments, during the scanning process, when the vital signal unit 109 acquires a specific signal, the scanning planning unit 110 may update the scanning plan in real time. For example, when scanning the heart, when the sign signal unit 109 collects the r-wave peak of the ECG signal, after a delay, which is equivalent to entering the mid-diastole of the ventricle, the scan planning unit 110 triggers the high-voltage generator 105 to work, and the tube 102 generates X-rays are used for radio frequency excitation and signal acquisition. On the eve of the next ventricular systole, the scanning planning unit 110 controls the high-voltage generator 105 to stop working, and the tube 102 stops generating X-rays. This basically guarantees the acquisition of projection data in the middle and late ventricular diastole, because the heart movement is relatively static during this period, which can significantly reduce motion artifacts, and the CT system does not generate X-rays during other stages of heart movement, thus reducing the impact on the heart and/or the heart. or unnecessary radiation doses to other nearby organs.

FIG. 2 is an exemplary flowchart of the reconstruction of a spiral CT scan image according to the present invention.

In step 201, the vital sign signal unit 109 collects the vital sign signal.

In step 202, the scan planning unit 110 formulates a scan plan according to the vital signs.

In step 203, the scan planning unit 110 controls the high voltage generator 105, the collimator driver 106, the rotation driver 107, and the position controller 108 to execute the scan plan according to the scan plan.

In step 204, the acquisition unit 113 converts the electrical signal generated by the detector 104 into a digital signal (projection data).

In step 206, the image reconstruction unit 112 receives the projection data generated by the acquisition unit 113, and starts to perform image reconstruction. The image reconstruction unit 112 may check the projection data obtained by the current CT system according to the image reconstruction check rule, and feed back the check result to the scan planning unit 110 . In some embodiments, the image reconstruction check rule may be determined by determining whether the projection data of the first scan plan (including the projection data already acquired and the projection data to be acquired under the first scan plan) meet certain conditions. If the current projection data of the first scan plan (including the projection data that has been acquired and the projection data to be acquired under the current scan plan) do not meet certain conditions (eg, the projection data of the current scan plan is insufficient or redundant), the scan planning unit 110 updates the scan plan according to the judgment result of the image reconstruction unit 112, and the scan plan unit 110 continues to perform scanning in step 203 according to the updated scan plan. If the projection data of the current scan plan (including the projection data that has been acquired and the projection data to be acquired under the current scan plan) meet certain conditions (eg, the projection data of the current scan plan is sufficient and not redundant), the scan planning unit 110 Continue to perform scanning in step 203 according to the original scanning plan.

FIG. 3 is a specific embodiment of an exemplary flowchart of the reconstruction of a spiral CT scan image according to the present invention.

In step 301, the vital sign signal unit 109 collects the ECG signal of the scanned object.

In step 302, the scan planning unit 110 formulates or updates a first scan plan according to the vital signal. The scan plan unit 110 may update the first scan plan in real time according to the ECG signal collected by the vital signal unit 109 . For example, when scanning the heart, when the sign signal unit 109 collects the r-wave peak of the ECG signal, after a delay, which is equivalent to entering the mid-diastole of the ventricle, the scan planning unit 110 triggers the high-voltage generator 105 to work, and the tube 102 generates X-ray, radio frequency excitation and signal acquisition. On the eve of the next ventricular contraction, the scan planning unit 110 controls the high-voltage generator 105 to stop working, and the tube 102 stops generating X-rays. When the vital sign signal unit 109 collects the r-wave peak of the ECG signal again, the scan planning unit 110 triggers the high-voltage generator 105 to work again, and the cycle is repeated.

In step 303, the acquisition unit 113 converts the electrical signal generated by the detector 104 into a digital signal (projection data).

In step 304, the image reconstruction unit 112 receives the projection data generated by the acquisition unit 113, and starts to perform image reconstruction.

In step 305, the image reconstruction unit 112 determines whether the projection data of the first scan plan (including the projection data already acquired and the projection data to be acquired under the first scan plan) is redundant and/or sufficient. If the image reconstruction unit 112 determines that the projection data of the first scan plan is not redundant and sufficient, then go to step 306 , the scan plan unit 110 maintains the first scan plan, and goes to step 308 to continue scanning. Then, the scanned data is sent to step 303 to continue reconstruction.

If the image reconstruction unit 112 determines that the projection data of the first scan plan is redundant, the scan plan unit 110 may generate a second scan plan at 307 , skipping the location where the redundant projection data is generated. For example, the scan planning unit 110 may increase the rotational speed of the rotating gantry at a certain moment, and in step 308 speed up the rotational speed of the rotating gantry by controlling the rotation driver 107 . For another example, the scan planning unit 110 may increase the movement speed of the couch 114 at a certain moment, and at step 308 speed up the movement speed of the couch 114 in the z direction (perpendicular to the x and y directions) by the position controller 108 . For another example, the scan planning unit 110 may stop the supply of the radiation dose at a certain moment, and stop the high-voltage generator 105 from working in step 308, so that the CT tube 101 does not emit X-rays temporarily. For another example, the scan planning unit 110 may change the width of the collimator 102 at a certain moment through the collimator driver 106 in step 308 to reduce or eliminate the radiation dose at the current position. The above methods can ensure sufficient projection data acquisition, and do not waste dose on useless projection data. Then, the acquired projection data is sent to step 303, and image reconstruction is continued.

If the image reconstruction unit 112 determines that the projection data of the first scan plan is insufficient, the scan plan unit 110 will formulate a second scan plan, and proceed to step 308 to execute the second scan plan, including reducing the rotational speed of the rotating gantry at a certain moment, reducing the The moving speed of the scanning bed 114 at a certain moment, turning on the high-voltage generator 105 at a certain moment, changing the width of the collimator at a certain moment, or any combination of the above methods, so as to obtain the necessary projection data and send the data Go to step 303, reconstruct the image that meets the requirements.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection.

Claims (10)

1. a control method of helical CT equipment, the helical CT equipment comprises a rotating gantry, a CT tube, a detector and a collimator that are fixed on the rotating gantry, and a scanning bed supporting a scanned object, The method includes: receiving physical data of the scanned object; formulating a first scan plan according to the physical sign data; CT scan is performed on the scanned object according to the first scan plan to acquire first projection data, where the first projection data includes projection data that has been acquired and projection data to be acquired under the first scan plan ; using the first projection data to perform inspection according to the image reconstruction inspection rule; Evaluate the result of the inspection according to a specific condition, if the evaluation result satisfies the specific condition, maintain the first scan plan, and if the evaluation result does not satisfy the specific condition, generate a second scan plan and continue to perform CT scanning on the scanned object according to the second scan plan, and obtain second projection data, wherein the specific condition is whether the first projection data is sufficient or redundant for image reconstruction; and, Image reconstruction is performed based on the first projection data or/and the second projection data. 2. The method of claim 1, wherein the vital sign data comprises an electrocardiogram signal or a breathing signal. 3 . The method of claim 1 , wherein the formulating the first scan plan according to the vital sign data comprises formulating different first scanning plans according to the vital sign data and different scanning positions. 4 . 4. The method of claim 1, wherein the judgment rule of the specific condition is: Parse out the layer position information of the first projection data, scan the bed code information, the encoder angle information, and arrange the data; Calculate the physical position range that the first projection data can support based on slice position information and scanning bed code information; The encoder angle information is counted within each physical location range to determine whether the angle information covered by the encoder meets the angle range requirements of the current scan and reconstruction, and to determine whether the first projection data is sufficient or redundant. 5. The method of claim 1, wherein the second projection data is projection data that has been acquired or will be acquired under the second scan plan. 6. The method of claim 1, wherein the second scan plan acquires more projection data than the first scan plan, or less projection data than the first scan plan. 7. The method of claim 1, wherein the first scan plan or the second scan plan comprises setting the rotation speed of the gantry, setting the moving speed of the scanning bed, setting the standard Adjust the width of the straightener or adjust the X-ray beam. 8. A control method of a spiral CT device, the spiral CT device comprising a rotating gantry, a CT tube, a detector and a collimator fixed on the rotating gantry, and a scanning bed supporting a scanned object, The method includes: receiving physical data of the scanned object; formulating a scan plan based on the physical sign data; CT scan is performed on the scanned object according to the scan plan to obtain projection data, the projection data including the projection data already acquired and the projection data to be acquired under the scan plan; Analyze the projection data to determine whether the scan plan meets the requirements. If it meets the requirements, continue scanning according to the established scan plan; if it does not meet the requirements, adjust the scan plan and continue according to the adjusted scan plan. Performing a scan, the analyzing the projection data includes determining whether the projection data is sufficient or redundant for image reconstruction. 9 . The method of claim 8 , wherein formulating the first scan plan according to the vital sign data comprises formulating different first scanning plans according to the vital sign data and different scanning positions. 10 . 10. The method of claim 8, wherein the adjusting the scan plan comprises adjusting the rotational speed of the gantry, adjusting the moving speed of the scanning bed, adjusting the width of the collimator, or adjusting the X-ray beam.

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