A method for controlling a helical CT scan

Abstract

This invention provides a control method for a spiral CT scanner, the method comprising: receiving vital sign data of a scanned object; formulating a first scan plan based on the vital sign data; performing a CT scan on the scanned object according to the first scan plan to obtain first projection data, the first projection data including projection data already acquired under the first scan plan and projection data to be acquired; performing an inspection using the first projection data according to image reconstruction inspection rules; evaluating the inspection results according to specific conditions, if the evaluation results meet the specific conditions, maintaining the first scan plan, if the evaluation results do not meet the specific conditions, generating a second scan plan and continuing to perform a CT scan on the scanned object according to the second scan plan, and obtaining second projection data, wherein the specific conditions are whether the first projection data is sufficient or redundant for image reconstruction; and performing image reconstruction based on the first projection data and / or the second projection data.

Description

[0001] Case Analysis

[0002] This application is a divisional application of Chinese application filed on May 31, 2017, with application number 201710402065.2, entitled "A Control Method for Spiral CT Scan". Technical Field

[0003] This invention relates to medical imaging systems, and more particularly to a control method for spiral CT scanning. Background Technology

[0004] Variable pitch spiral CT scanning represents a significant breakthrough in X-ray imaging technology. It allows for on-the-spot adjustment of the pitch to achieve optimal image reconstruction quality. In medical lesion diagnosis, different slice thicknesses are selected for spiral scanning, with appropriate pitch and reconstruction intervals chosen to obtain better image quality. For example, during whole-body scans, a larger pitch can be used for normal areas, while a smaller pitch is used for lesions, thus shortening scan time and reducing radiation dose. Furthermore, combining variable pitch spiral scanning with techniques such as ECG gating, ECG triggering, and respiratory gating effectively reduces artifacts.

[0005] The problem with existing technology is that it cannot definitively determine which path is most suitable for scanning different body parts. Current technology involves planning an ideal path that accounts for errors during scan planning, and then executing the scan according to the original plan without adjusting the plan based on actual conditions. This presents a contradiction: if the pre-set error tolerance is small, it's difficult to guarantee that the scan will stay within the error range during actual execution; conversely, if the pre-set error tolerance is large, the function will not significantly improve dose utilization. Summary of the Invention

[0006] To address the above problems, this invention provides a control method for a spiral CT scanner, which can solve these problems.

[0007] The present invention provides a control method for a spiral CT scanner, comprising: receiving vital sign data of the object being scanned; formulating a first scan plan based on the vital sign data; performing a CT scan on the object being scanned according to the first scan plan to obtain first projection data; performing an examination using the first projection data according to image reconstruction examination rules; evaluating the examination results according to specific conditions; if the evaluation results meet the specific conditions, maintaining the first scan plan; if the evaluation results do not meet the specific conditions, generating a second scan plan and continuing to perform a CT scan on the object being scanned according to the second scan plan to obtain second projection data; and performing image reconstruction based on the first projection data and / or the second projection data.

[0008] In this invention, the vital signs data include electrocardiogram signals or respiratory signals;

[0009] In this invention, the specific condition is whether the first projection data of the first scanning plan is sufficient or redundant for image reconstruction;

[0010] In this invention, the judgment rule for the specific condition is as follows: parse the slice position information, scanning bed code information, and encoder angle information of the first projection data, and arrange the data; calculate the physical position range that the current first projection data can support using the slice position information and the scanning bed code information; perform statistics on the encoder angle information within each physical position range to determine whether the angle information covered by the encoder meets the angle range requirements of the current scan and reconstruction, and determine whether the first projection data is sufficient or redundant;

[0011] In this invention, the first projection data or the second projection data is the projection data that has been acquired or will be acquired under the first scanning plan or the second scanning plan;

[0012] In this invention, the second scanning plan is to acquire more projection data than the first scanning plan, or less projection data than the first scanning plan;

[0013] In this invention, the first scanning plan or the second scanning plan includes setting the rotation speed of the rack;

[0014] In this invention, the first scanning plan or the second scanning plan includes setting the moving speed of the scanning bed;

[0015] In this invention, the first scanning plan or the second scanning plan includes setting the width of the collimator;

[0016] In this invention, the first or second scanning plan includes adjusting the X-ray beam.

[0017] The present invention provides a control method for a spiral CT scanner, comprising: receiving vital sign data of the object being scanned; formulating a scan plan based on the vital sign data; performing a CT scan on the object being scanned according to the scan plan to obtain projection data; analyzing the projection data to determine whether the scan plan meets the requirements; if it meets the requirements, continuing the scan according to the formulated scan plan; if it does not meet the requirements, adjusting the scan plan and continuing the scan according to the adjusted scan plan.

[0018] In this invention, the analysis of the projection data includes determining whether the projection data is sufficient or redundant for image reconstruction.

[0019] In this invention, adjusting the scanning plan includes adjusting the rotation speed of the gantry, adjusting the movement speed of the scanning bed, adjusting the width of the collimator, or adjusting the X-ray beam. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0021] Figure 1 This is a schematic diagram of the spiral CT system structure of the present invention;

[0022] Figure 2 This is an example flowchart of spiral CT scan image reconstruction according to the present invention;

[0023] Figure 3 This is a flowchart illustrating an embodiment of spiral CT scan image reconstruction according to the present invention. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples.

[0025] For a complete understanding of this invention, please refer to [link / reference]. Figure 1 This diagram illustrates the structure 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 signs signal unit 109, a scan planning unit 110, an image reconstruction unit 112, an acquisition unit 113, and a scanning bed 114.

[0026] A high-voltage generator 105 receives commands from the scan planning unit 110 and controls the operation of the CT tube 101. The CT tube 101 provides X-rays 103. After passing through the collimator 102, the X-rays pass through the scanned object located on the scan bed 114 and are partially attenuated. A detector 104 receives the partially attenuated X-ray signal and converts it into a corresponding electrical signal. The detector 104 is mounted inside a metal substrate and is mounted on opposite sides of the gantry to the CT tube 101. The collimator 102 defines 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 below the scintillation crystals, and a chip substrate for the scintillation crystals.

[0027] The acquisition unit 113, connected to the detector 104 system, acquires the electrical signals 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. These electrical signals are then converted into digital signals (projection data) by an A / D converter. The image reconstruction unit 112, connected to the acquisition unit 113, receives the projection data. The image reconstruction unit 112 performs data compression and / or reformatting on the received projection data, and then stores the processed data (e.g., in a buffer) and / or performs further processing. The back-projection controller in the image reconstruction unit 112 can distribute the projection data to the various units of the back-projection plate. The data contained in each back-projection unit can range from one projection to six projections and is stored simultaneously. The image data, along with the results from each back-projection unit, is then transmitted to each back-projection plate for summation to synthesize pixel data, thereby reconstructing the tomographic image and displaying it on a monitor (not shown on the screen). Figure 1 (As shown in the image) is displayed or stored on a storage device.

[0028] In some embodiments, the image reconstruction unit 112 can inspect the projection data acquired by the current CT system according to image reconstruction inspection rules and feed the inspection results back to the scan planning unit 110. In some embodiments, the image reconstruction inspection rules can determine whether the projection data of the first scan plan (including the projection data already acquired under the first scan plan and the projection data to be acquired) meets specific conditions. In some embodiments, whether the projection data meets specific conditions can 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 the slice position information, scan bed code information, and encoder angle information of the projection data and arrange the data; then, the image reconstruction unit 112 calculates the physical position range that the current projection data can support using the slice position information and scan bed code information; finally, the image reconstruction unit 112 performs statistical analysis of the encoder angle information within each physical position range to determine whether the angle information covered by the encoder meets the angle range requirements of the current scan and reconstruction, and determines whether the current projection data can reconstruct an image that meets the requirements.

[0029] For example, during a cardiac scan, the scan planning unit 110 formulates and executes a first scan plan. At a certain moment, if the image reconstruction unit 112 determines, according to the image reconstruction check rules, that the projection data acquired under the first scan plan (including the projection data already acquired under the first scan plan and the projection data to be acquired) cannot reconstruct a satisfactory image, i.e., the projection data acquired under the current scan plan is insufficient, the image reconstruction unit 112 can transmit the check result to the scan planning unit 110 to generate and execute a second scan plan to acquire additional projection data to reconstruct a satisfactory image. At a certain moment, if the image reconstruction unit 112 determines, according to the image reconstruction check rules, that the projection data acquired under the first scan plan (including the projection data already acquired under the first scan plan and the projection data to be acquired) cannot reconstruct a satisfactory image, the image reconstruction unit 112 can transmit the check result to the scan planning unit 110 to generate and execute a second scan plan to acquire additional projection data to reconstruct a satisfactory image. If the acquired projection data can reconstruct a satisfactory image without any redundant data (meaning the acquired projection data under the current scan plan is sufficient), then 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 determines, according to the image reconstruction check rules, that the acquired projection data under the first scan plan (including the already acquired projection data and the projection data to be acquired under the first scan plan) can reconstruct a satisfactory image, and there is redundant projection data (meaning the acquired projection data under the current scan plan is excessive), then the image reconstruction unit 112 can transmit the check result to the scan planning unit 110 to generate and execute the third scan plan, skipping the position where redundant projection data is generated and stopping the acquisition of redundant projection data. The so-called "satisfaction with requirements" can refer to the clarity and completeness of the reconstructed image, or it can be preset according to specific circumstances.

[0030] It should be noted that the first scan plan, the second scan plan, and the third scan plan mentioned in this disclosure do not refer to any one or more scan plans, but are only used to distinguish different scan plans from each other.

[0031] The CT tube 101, collimator 102, and detector 104 can be fixed to the rotating gantry (not in...). Figure 1 As shown in the diagram, the rotating gantry can be driven to rotate by the rotary driver 107. The scan planning unit 110 can control the rotation speed and direction of the rotating gantry by controlling the rotary driver 107. Simultaneously, the position controller 108 can drive the scan bed 114 along the z-direction (perpendicular to the x and y directions, where the y-direction is perpendicular to the scan bed, and the x-direction is parallel to the scan bed and perpendicular to the y-direction, as shown in the diagram). Figure 1 (As shown) the movement. The scan planning unit 110 can control the direction and speed of movement of the scan bed 114 via the position controller 108. The collimator 102 is used to determine the thickness of the X-rays. The specific thickness of the X-rays is determined by the width of the collimator 102. The scan planning unit 110 can change the width of the collimator 102 via the collimator driver 106.

[0032] During the scanning process, the CT tube 101, collimator 102, and detector 104 can rotate in a certain direction and at a certain speed under the drive of the rotating gantry, while 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 object being scanned, while the object being scanned moves forward at a constant speed under the drive of the scanning bed. As a result, the trajectory left by the X-rays on the object being scanned is a spiral curve.

[0033] The vital signs signal unit 109 can collect the patient's vital signs data, such as electrocardiogram (ECG) data and respiratory data. The vital signs data that the vital signs signal unit 109 can collect include, but are not limited to, ECG signals and respiratory signals. In some embodiments, the ECG signal can be an electrical signal generated by the heartbeat and can be collected by electrodes placed on the scanned object during scanning. In some embodiments, the respiratory signal can be collected by a breathing band placed on the abdomen of the scanned object, and the collected respiratory signal represents the movement of the diaphragm of the scanned object. The vital signs signal unit 109 may include, or be connected to, a device for collecting vital signs signals to acquire vital signs signals. In some embodiments, the image reconstruction unit 112 can selectively reconstruct images based on the vital signs data collected by the vital signs signal unit 109. In some embodiments, the image reconstruction unit 112 can select projection data at a certain moment for reconstruction based on the ECG signal collected by the vital signs signal unit 109. For example, if a cardiac cycle is divided into 20 phases, the image reconstruction unit 112 can collect the ECG signal from the vital signs signal unit 109, extract the projection data of each of the 20 phases, and reconstruct 20 images corresponding to different phases.

[0034] The scan planning unit 110 can formulate a scan plan. The scan plan can be a plan for the CT system to acquire projection data. In some embodiments, the scan planning unit 110 can formulate a scan plan based on periodic vital sign data collected by the vital sign signal unit 109. For example, based on the electrocardiogram signals collected by the vital sign signal unit 109, a cardiac cycle can be divided into several phases. During a cardiac scan, the scan planning unit 110 can formulate and execute the scan plan, acquiring only the projection data of the heart within one or several specific phases. The scan planning unit 110 controls one or more combinations of the high-voltage generator 105, collimator driver 106, rotation driver 107, position controller 108, etc., according to the scan plan to realize the scan plan. The scan plan can be whether the high-voltage generator 105 is working at a certain moment within a certain scan cycle, the width of the collimator 102 at a certain moment, the rotation speed and / or rotation direction of the gantry at a certain moment, and the moving speed and / or moving direction of the scanning table 114 at a certain moment.

[0035] In some embodiments, the scan planning unit 110 can formulate different scan plans based on different scan locations. For example, during a whole-body CT scan, for areas requiring high scanning accuracy (such as the head, heart, etc.), the scan planning unit 110 can formulate a scan plan that slows down the rotation speed of the gantry and the movement speed of the scanning bed 114, thereby improving scanning accuracy. For areas requiring low scanning accuracy (such as the abdomen, legs, etc.), the scan planning unit 110 can formulate a scan plan that speeds up the rotation speed of the gantry and the movement speed of the scanning bed 114, thereby quickly scanning these areas and reducing unnecessary radiation dose.

[0036] In some embodiments, the scan planning unit 110 can update the scan plan based on feedback from the image reconstruction unit 112. Updating the scan plan can be achieved by, but is not limited to: setting the rotational speed of the gantry, setting the movement speed of the scanning bed 114, setting the width of the collimator 102, adjusting the X-ray beam, or any combination thereof. Adjusting the X-ray beam can be done by turning the beam on or off, or by changing the beam size. For example, when scanning the heart, the scan planning unit 110 can formulate and execute a first scan plan. At a certain moment, if the image reconstruction unit 112 reports that there is excess projection data acquired under the first scan plan (including projection data already acquired and projection data to be acquired under the first scan plan), the scan planning unit 110 will formulate a second scan plan. This includes increasing the rotational speed of the gantry at a certain moment, increasing the movement speed of the scanning bed 114 at a certain moment, turning off the high-voltage generator 105 at a certain moment, or any combination thereof, skipping the locations that generate excess projection data, thereby preventing the heart and / or other nearby organs from receiving unnecessary radiation doses. For example, when scanning the heart, the scan planning unit 110 can formulate and execute a first scan plan. At a certain moment, when the image reconstruction unit 112 reports that the projection data acquired under the first scan plan (including the projection data already acquired under the first scan plan and the projection data to be acquired) is insufficient, the scan planning unit 110 will formulate a second scan plan, including reducing the rotation speed of the gantry at a certain moment, reducing the moving speed of the scanning bed 114 at a certain moment, turning on the high voltage generator 105 at a certain moment, or any combination of the above methods, so as to acquire the necessary projection data and reconstruct an image that meets the requirements.

[0037] In some embodiments, during the scanning process, when the vital signs signal unit 109 acquires a specific signal, the scan planning unit 110 can update the scan plan in real time. For example, when scanning the heart, when the vital signs signal unit 109 acquires the r-wave peak of the electrocardiogram signal, after a delay, equivalent to entering the mid-diastolic phase of the ventricle, the scan planning unit 110 triggers the high-voltage generator 105 to operate, and the X-ray tube 102 generates X-rays for radiofrequency excitation and signal acquisition. Just before the next ventricular systole, the scan planning unit 110 controls the high-voltage generator 105 to stop operating, and the X-ray tube 102 to stop generating X-rays. This essentially ensures that projection data is acquired during the mid-to-late diastolic phase of the ventricle, because the heart is relatively still during this period, significantly reducing motion artifacts. Furthermore, since the CT system does not generate X-rays during other phases of heart movement, unnecessary radiation doses to the heart and / or other nearby organs can be reduced.

[0038] Figure 2 This is an example flowchart of spiral CT scan image reconstruction according to the present invention.

[0039] In step 201, the vital signs signal unit 109 collects vital signs signals.

[0040] In step 202, the scan planning unit 110 formulates a scan plan based on the vital signs signals.

[0041] In step 203, the scan planning unit 110 controls the high voltage generator 105, collimator driver 106, rotary driver 107, and position controller 108 to execute the scan plan according to the scan plan.

[0042] In step 204, the acquisition unit 113 converts the electrical signal generated by the detector 104 into a digital signal (projection data).

[0043] In step 206, the image reconstruction unit 112 receives the projection data generated by the acquisition unit 113 and begins image reconstruction. The image reconstruction unit 112 can check the projection data acquired by the current CT system according to image reconstruction check rules and feed the check results back to the scan planning unit 110. In some embodiments, the image reconstruction check rules can determine whether the projection data of the first scan plan (including the projection data already acquired under the first scan plan and the projection data to be acquired) meets specific conditions. If the current projection data of the first scan plan (including the projection data already acquired under the current scan plan and the projection data to be acquired) does not meet specific conditions (e.g., the projection data of the current scan plan is insufficient or excessive), the scan planning unit 110 updates the scan plan according to the judgment result of the image reconstruction unit 112, and the scan planning 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 already acquired and the projection data to be acquired under the current scan plan) meets certain conditions (e.g., the projection data of the current scan plan is sufficient and not redundant), then the scan plan unit 110 continues to perform the scan in step 203 according to the original scan plan.

[0044] Figure 3 This is a specific embodiment of an example flowchart for spiral CT scan image reconstruction of the present invention.

[0045] In step 301, the vital signs signal unit 109 acquires the electrocardiogram signal of the scanned object.

[0046] In step 302, the scan planning unit 110 formulates or updates the first scan plan based on the vital signs signals. The scan planning unit 110 can update the first scan plan in real time based on the electrocardiogram (ECG) signals acquired by the vital signs signal unit 109. For example, when scanning the heart, when the vital signs signal unit 109 acquires the R-wave peak of the ECG signal, after a delay, equivalent to entering the mid-diastolic phase of the ventricle, the scan planning unit 110 triggers the high-voltage generator 105 to operate, and the X-ray tube 102 generates X-rays for radiofrequency excitation and signal acquisition. Just before the next ventricular systole, the scan planning unit 110 controls the high-voltage generator 105 to stop operating, and the X-ray tube 102 stops generating X-rays. When the vital signs signal unit 109 acquires the R-wave peak of the ECG signal again, the scan planning unit 110 triggers the high-voltage generator 105 to operate again, and so on in a cycle.

[0047] In step 303, the acquisition unit 113 converts the electrical signal generated by the detector 104 into a digital signal (projection data).

[0048] In step 304, the image reconstruction unit 112 receives the projection data generated by the acquisition unit 113 and begins image reconstruction.

[0049] In step 305, the image reconstruction unit 112 determines whether the projection data of the first scanning plan (including the projection data already acquired under the first scanning plan and the projection data to be acquired) is redundant and / or sufficient. If the image reconstruction unit 112 determines that the projection data of the first scanning plan is not redundant and is sufficient, then proceed to step 306, the scanning plan unit 110 maintains the first scanning plan, and proceeds to step 308 to continue scanning. Then, the scanned data is sent to step 303 to continue reconstruction.

[0050] If the image reconstruction unit 112 determines that the projection data of the first scan plan is redundant, the scan planning unit 110 can generate a second scan plan at 307, skipping the position where redundant projection data is generated. For example, the scan planning unit 110 can increase the rotation speed of the gantry at a certain moment, and accelerate the gantry speed by controlling the rotation driver 107 in step 308. Alternatively, the scan planning unit 110 can increase the moving speed of the scanning bed 114 at a certain moment, and accelerate the moving speed of the scanning bed 114 along the z-direction (perpendicular to the x and y directions) by the position controller 108 in step 308. Another example is that the scan planning unit 110 can stop the supply of radiation dose at a certain moment, and pause the operation of the high-voltage generator 105 in step 308, thereby temporarily stopping the CT tube 101 from emitting X-rays. Yet another example is that the scan planning unit 110 can change the width of the collimator 102 at a certain moment by using the collimator driver 106 in step 308, reducing or eliminating the radiation dose at the current position. These methods ensure sufficient projection data acquisition and prevent wasting dose on useless projection data. Then, the acquired projection data is sent to step 303 to continue image reconstruction.

[0051] If the image reconstruction unit 112 determines that the projection data of the first scanning plan is insufficient, the scanning plan unit 110 will formulate a second scanning plan and proceed to step 308 to execute the second scanning plan. This includes reducing the rotation speed of the gantry at a certain moment, reducing 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, thereby obtaining the necessary projection data and sending the data to step 303 to reconstruct an image that meets the requirements.

[0052] 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 within the protection scope of the present invention.

Claims

1. A control method for a spiral CT scanner, the spiral CT scanner comprising a rotating gantry, a CT tube, a detector, and a collimator fixed on the rotating gantry, and a scanning bed supporting the object being scanned, the method comprising: Receive the vital signs data of the scanned object; A first scanning plan is formulated based on the aforementioned vital sign data; The object to be scanned is subjected to a CT scan according to the first scan plan to obtain first projection data, which includes projection data already obtained under the first scan plan and projection data to be obtained. The first projection data is used to perform an inspection based on image reconstruction inspection rules; The results of the examination are evaluated according to specific conditions. If the evaluation results meet the specific conditions, the first scanning plan is maintained. If the evaluation results do not meet the specific conditions, a second scanning plan is generated and the object being scanned is scanned again according to the second scanning plan, and second projection data is obtained. The specific conditions are whether the first projection data is sufficient or redundant for image reconstruction. as well as, Image reconstruction is performed based on the first projection data and / or the second projection data.

2. The method as claimed in claim 1, characterized in that, The vital signs data include electrocardiogram signals or respiratory signals.

3. The method as described in claim 1, characterized in that, The step of formulating a first scanning plan based on the vital signs data includes formulating different first scanning plans based on the vital signs data and different scanning locations.

4. The method as claimed in claim 1, characterized in that, The judgment rule for the specific condition is as follows: The layer position information, bed code information, and encoder angle information of the first projection data are parsed out, and the data is arranged. The range of physical locations that the first projection data can support is calculated using slice location information and scanned bed code information; Statistical analysis of encoder angle information is performed within each physical location range to determine whether the angle information covered by the encoder meets the angle range requirements for the current scan and reconstruction, and to determine whether the first projection data is sufficient or redundant.

5. The method as claimed in claim 1, characterized in that, The second projection data refers to the projection data that has been acquired and will be acquired under the second scanning plan.

6. The method as claimed in claim 1, characterized in that, The second scanning plan is to acquire more projection data than the first scanning plan, or less projection data than the first scanning plan.

7. The method as claimed in claim 1, characterized in that, The first or second scanning plan includes setting the rotation speed of the gantry, setting the movement speed of the scanning bed, setting the width of the collimator, or adjusting the X-ray beam.

Images