Reordering method, ct scanning apparatus, and readable storage medium

Abstract

The application provides a rearrangement method, a CT scanning device and a readable storage medium. The rearrangement method comprises the following steps: transposing base data formed by a plurality of fan beam projection data, and calculating and outputting parallel beam projection data based on the transposed base data. In this way, the internal structure of the base data is changed by data transposition, so that the data related to the same parallel beam projection data exists in the same row of the base data, the access frequency of the first storage medium when generating one parallel beam projection data is reduced, the rearrangement time is reduced, and the problem that the CT rearrangement algorithm has frequent memory access, slow speed and affects the reconstruction speed of the whole image reconstruction algorithm in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the field of medical imaging technology, and in particular to a rearrangement method, a CT scanning device and a readable storage medium. Background Art

[0002] The CT realignment algorithm is one of the basic algorithms in all CT filtered back projection (FBP) algorithms. The main function of this algorithm is to convert the original data from the projection view of the fan beam during scanning to the projection view of the parallel beam.

[0003] In the prior art, the calculation process of the CT realignment algorithm is very computationally intensive and memory access is frequent, resulting in a very slow calculation speed of the CT realignment algorithm, which has become the biggest bottleneck in the CT reconstruction process.

[0004] In summary, in the prior art, the memory access of the CT realignment algorithm is frequent and too slow, which affects the reconstruction speed of the entire image reconstruction algorithm. Summary of the Invention

[0005] The purpose of the present invention is to provide a rearrangement method, a CT scanning device and a readable storage medium to solve the problem in the prior art that the CT rearrangement algorithm has frequent memory access, is too slow, and affects the reconstruction speed of the entire image reconstruction algorithm.

[0006] In order to solve the above technical problems, the present invention provides a rearrangement method for converting fan beam projection data into parallel beam projection data, and the rearrangement method includes the following steps: sequentially acquiring a plurality of the fan beam projection data according to the data acquisition angle, and the fan beam projection data are sorted in the order of acquisition, and the plurality of the fan beam projection data constitute basic data; transposing the basic data, and storing the transposed basic data in a first storage medium; reading a row of data along the row direction of the basic data, and the read data is set as intermediate data; storing the intermediate data in a second storage medium; outputting one parallel beam projection data based on the intermediate data in the second storage medium; deleting the current first fan beam projection data in the basic data; and performing an end judgment. If the result is yes, end; if the result is no, repeatedly acquire the intermediate data.

[0007] Optionally, the storage capacity of the first storage medium is greater than a preset multiple of the storage capacity of the second storage medium, and the read and write speed of the second storage medium is greater than the read and write speed of the first storage medium.

[0008] Optionally, the preset multiple is the maximum number of the fan-beam projection data in the basic data.

[0009] Optionally, the logic of the end judgment is: whether the number of the fan beam projection data remaining in the basic data is less than the number required to calculate one parallel beam projection data; if so, the result is yes; otherwise, the result is no.

[0010] Optionally, the first storage medium is a memory, and the second storage medium is a CPU cache.

[0011] Optionally, the step of outputting the parallel beam projection data based on the intermediate data in the second storage medium includes: calculating a first projection result based on the intermediate data in the second storage medium; transposing the first projection result to obtain a second projection result; and configuring the second projection result as the parallel beam projection data and outputting it.

[0012] Optionally, the rearrangement method further includes: reconstructing the parallel beam projection data to obtain a target tomographic image.

[0013] In order to solve the above technical problems, the present invention also provides a CT scanning device, including a tube for emitting penetrating rays, detectors distributed in a fan shape, and a processing module, wherein a space for accommodating an object to be measured is provided between the tube and the detector, the tube and the detector can rotate relatively fixedly around the object to be measured, and the detector is used to obtain fan beam projection data; the processing module is used to rearrange the fan beam projection data based on the above rearrangement method.

[0014] In order to solve the above technical problem, the present invention further provides a readable storage medium, on which a program is stored. When the program is run, the above rearrangement method is executed.

[0015] Compared with the prior art, the present invention provides a rearrangement method, a CT scanning device, and a readable storage medium, wherein the rearrangement method includes the following steps: sequentially acquiring a plurality of the fan-beam projection data according to the data acquisition angle, the fan-beam projection data being sorted in the order of acquisition, and the plurality of the fan-beam projection data constituting basic data; transposing the basic data, and storing the transposed basic data in a first storage medium; reading a row of data along the row direction of the basic data, and the read data being set as intermediate data; storing the intermediate data in a second storage medium; outputting one parallel beam projection data based on the intermediate data in the second storage medium; deleting the current first fan-beam projection data in the basic data; and performing an end judgment. If the result is yes, the judgment ends; if the result is no, repeatedly acquiring the intermediate data. With such a configuration, the internal structure of the basic data is changed through data transposition, so that data related to the same parallel beam projection data exists in the same row of the basic data, reducing the number of accesses to the first storage medium when generating the parallel beam projection data, thereby reducing the rearrangement time, and solving the problem in the prior art that the CT rearrangement algorithm frequently accesses the memory, the speed is too slow, and the reconstruction speed of the entire image reconstruction algorithm is affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0017] Figure 1 is a schematic flow chart of a rearrangement method according to an embodiment of the present invention;

[0018] Figure 2 is a schematic structural diagram of a CT scanning device according to an embodiment of the present invention;

[0019] Figure 3 is a schematic diagram of fan beam projection data according to an embodiment of the present invention;

[0020] Figure 4 is a schematic diagram of the original structure of image data according to an embodiment of the present invention;

[0021] Figure 5 is a schematic diagram of multiple fan-beam projection data according to an embodiment of the present invention;

[0022] Figure 6 FIG. 4 is a schematic diagram of parallel beam projection data according to an embodiment of the present invention.

[0023] In the attached figure:

[0024] 1-tube; 2-measured object; 3-detector; 4-tube motion trajectory; 5-reference direction. DETAILED DESCRIPTION

[0025] To make the objects, advantages, and features of the present invention more clearly apparent, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale. They are only used to conveniently and clearly assist in illustrating the purposes of the embodiments of the present invention. In addition, the structures shown in the drawings are often part of the actual structure. In particular, different drawings may need to illustrate different focuses and sometimes use different scales.

[0026] As used in the present invention, the singular forms "a", "an" and "the" include plural objects, the term "or" is generally used in a sense including "and / or", the term "several" is generally used in a sense including "at least one", and the term "at least two" is generally used in a sense including "two or more". In addition, the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", and "third" may explicitly or implicitly include one or at least two of such features. The term "proximal end" generally refers to the end closest to the operator, and the term "distal end" generally refers to the end closest to the patient. "One end" and "the other end" as well as "proximal end" and "distal end" generally refer to two corresponding parts, which include not only endpoints. The terms "mounted", "connected", and "connected" should be understood in a broad sense. For example, they can be fixedly connected, detachably connected, or integrated; they can be mechanically connected or electrically connected; they can be directly connected or indirectly connected through an intermediate medium; they can be internal communication between two elements or an interactive relationship between two elements. In addition, as used in the present invention, "one element is arranged on another element" generally only means that there is a connection, coupling, cooperation, or transmission relationship between the two elements, and the connection, coupling, cooperation, or transmission between the two elements can be direct or indirect through an intermediate element, and it should not be understood to indicate or imply a spatial positional relationship between the two elements, that is, one element can be in any position such as inside, outside, above, below, or to the side of another element, unless the content clearly indicates otherwise. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The core idea of ​​the present invention is to provide a rearrangement method, a CT scanning device and a readable storage medium to solve the problem in the prior art that the CT rearrangement algorithm has frequent memory access, is too slow, and affects the reconstruction speed of the entire image reconstruction algorithm.

[0028] The following description is made with reference to the accompanying drawings. Figure 1is a schematic flow chart of a rearrangement method according to an embodiment of the present invention; Figure 2 is a schematic structural diagram of a CT scanning device according to an embodiment of the present invention; Figure 3 is a schematic diagram of fan beam projection data according to an embodiment of the present invention; Figure 4 is a schematic diagram of the original structure of image data according to an embodiment of the present invention; Figure 5 is a schematic diagram of multiple fan-beam projection data according to an embodiment of the present invention;

[0029] Figure 6 FIG. 4 is a schematic diagram of parallel beam projection data according to an embodiment of the present invention.

[0030] like Figure 1 As shown, the present invention provides a rearrangement method for converting fan beam projection data into parallel beam projection data, the rearrangement method comprising the following steps:

[0031] S10 sequentially acquires a plurality of the fan-beam projection data according to the data acquisition angle, and the fan-beam projection data are sorted according to the order of acquisition. The plurality of the fan-beam projection data constitute basic data.

[0032] S20 transposes the basic data, and stores the transposed basic data in a first storage medium.

[0033] S30 reads a row of data along the row direction of the basic data, and the read data is set as intermediate data.

[0034] S40 The intermediate data is stored in the second storage medium.

[0035] S50 outputs the parallel beam projection data based on the intermediate data in the second storage medium.

[0036] S60: Delete the first fan-beam projection data in the basic data.

[0037] And, S70 performs an end judgment, if the result is yes, then the process ends; if the result is no, then the intermediate data is repeatedly obtained.

[0038] The storage capacity of the first storage medium is greater than a preset multiple of the storage capacity of the second storage medium, and the read and write speed of the second storage medium is greater than the read and write speed of the first storage medium.

[0039] It should be understood that the read and write speed of the storage medium should be understood as the read and write speed when implementing the rearrangement method. It is not only affected by factors such as the material, working principle, and control circuit of the storage medium itself, but also related to the relative position relationship and communication method between the actuators executing the rearrangement method. In step S60, the current first should be understood as follows. Assuming that the fan-beam projection data are numbered 1, 2, 3, 4, 5, and 6, respectively, and are sorted in sequence, then the first fan-beam projection data in the initial state is the fan-beam projection data numbered 1. After step S60 is executed once, the fan-beam projection data numbered 1 is deleted, and the fan-beam projection data numbered 2, 3, 4, 5, and 6 remain. When step S60 is executed for the second time, the current first fan-beam projection data is the fan-beam projection data numbered 2; when it is executed for the third time, it is the fan-beam projection data numbered 3.

[0040] In this embodiment, due to the limited storage capacity of the second storage medium, only a portion of the basic data can be loaded at a time. However, if calculations are performed directly based on the first storage medium, the read and write speeds will affect the final calculation results. Therefore, the basic data is processed by transposing, so that when the parallel beam projection data is subsequently generated, the total number of data transfers from the first storage medium to the second storage medium can be reduced, thereby speeding up the time of the rearrangement method. According to calculations, after the rearrangement method provided by this embodiment replaces the existing fluoroscopic image reconstruction algorithm, the performance of the fluoroscopic image reconstruction algorithm can be improved by 4 to 6 times, solving the problem of the slow speed of the rearrangement algorithm.

[0041] On the other hand, since transposition calculation is a common operation of general data processing equipment, it often has hardware or software acceleration support. Therefore, it is an optimization method that requires less modification to the existing technology. Compared with other potential solutions for reconstructing the internal structure of the basic data, this embodiment has a lower cost for modifying the existing method and is less likely to cause program bugs.

[0042] Please refer to Figure 2 The fan-beam projection data is obtained based on a CT scanning device, which includes a tube 1 (also called a radiation source) for emitting penetrating rays and detectors 3 distributed in a fan shape. A space for accommodating a test object 2 (e.g., a patient) is provided between the tube 1 and the detector 3. The tube 1 and the detector 3 can rotate relatively fixedly around the test object 2. The detector 3 is used to obtain fan-beam projection data. During rotation, the tube 1 moves along the tube motion trajectory 4. Please combine Figure 3 ,exist Figure 3In the figure, since the perspective rays (such as X-rays) emitted by the tube are received by the multiple detectors 3 in a straight line, and the lines between the tube 1 and the detectors 3 are distributed in a fan shape, the data received by the multiple detectors 3 at a certain moment is called the fan beam projection data. Figure 4 , the above fan beam projection data are displayed in the same coordinate system, and the following can be obtained: Figure 4 The screen shown. Figure 4 In the example, each independent small rectangle represents all the data content received by a detector at a moment, and each point in the small rectangle represents a pixel in a detector. Figure 4 The horizontal direction is the channel direction. If the detector moves along the horizontal direction, the number of the detector changes, but the data receiving time remains unchanged. Figure 4 The vertical direction is the row direction, or it can be understood as the data input direction. Moving along the vertical direction, the detector number does not change, but the data receiving time changes. Figure 4 The displayed data cannot be restored to an actual image through one's own imagination, so it is necessary to rearrange the above data using the rearrangement method described in this embodiment to ultimately obtain an intuitive image that can be understood by the user.

[0043] Please combine Figure 5 or Figure 6 When the tube 1 keeps rotating, multiple fan beam projection data can be obtained at multiple moments, and the multiple fan beam projection data are displayed in one picture. The result is as follows Figure 5 or Figure 6 As shown, the image reconstruction process requires obtaining data in a parallel beam format to facilitate subsequent image processing. Therefore, it is necessary to extract the "relatively parallel" data from the multiple fan-beam projection data and reassemble it into the parallel beam projection data. It should be understood that the data is not actually "relatively parallel." It's just that the line connecting the detector 3 and the tube 1 that acquires the data is relatively parallel. For ease of description, the data with parallel lines is referred to as "relatively parallel." Figure 6 All the thick black solid lines in the figure constitute one parallel beam projection data. In step S70, repeatedly acquiring the intermediate data means repeating step S30 and continuing to execute according to the subsequent steps. In step S30, the rows in a row of data should be understood as the basic data as a matrix, and a row corresponds to a row in the matrix.

[0044] In one embodiment, the preset multiple is the maximum number of fan-beam projection data in the basic data. That is, the storage space of the first storage medium and the second storage medium is significantly different. In this case, the rearrangement method provided in this embodiment can better exert its advantages.

[0045] To ensure that each output of parallel beam projection data contains all relevant information, the termination judgment logic is as follows: Is the number of remaining fan beam projection data in the basic data less than the number N required to calculate one parallel beam projection data? If so, the result is yes; otherwise, the result is no. This configuration allows calculation to be terminated when insufficient data is available, avoiding the output of incorrect or incomplete data. The value range of N is an integer greater than 0.

[0046] Where N is calculated according to the following formula:

[0047]

[0048] Among them, ceil represents the upward rounding function, max represents the maximum value function, DetAgl i Represents the relationship between the i-th detector and the emission source (which can be understood as Figure 2 The angle formed by the line formed by the tube 1 shown (which may also be other forms of emission sources) relative to the reference direction 5 is counterclockwise positive. The reference direction 5 refers to the direction from the emission source toward the rotation center. The value of i is an integer from 1 to m, where m is the total number of detectors. AglPerView represents the interval between the data acquisition angles of two adjacent fan beam projection data. Here, max(|DetAgl i |) means in all |DetAgl i | Take the maximum value. i Can be followed Figure 3 The angle shown is understood, wherein the reference direction 5 is Figure 3 As shown in the AglPerView Figure 5 In Figure 3 In the figure, the “i-th detector” points to the point representing the 8th detector. This is because only one specific point can be selected in the picture for indication. In fact, the “i-th detector” can refer to any one of the 1st to mth detectors, and is not limited to Figure 3 The "8th detector" pointed in the middle.

[0049] In one embodiment, the step of outputting the parallel beam projection data based on the intermediate data in the second storage medium includes: calculating a first projection result based on the intermediate data in the second storage medium; obtaining a second projection result after transposing the first projection result; and configuring the second projection result as the parallel beam projection data and outputting it. With such a configuration, the effect of the misalignment of the channel data caused by the first transposition can be eliminated by the second transposition to obtain the correct result. It should be understood that in other embodiments, the effect of the first transposition can also be eliminated by other means (for example, directly positioning to the corresponding position), and the second transposition is not required. However, as mentioned above, the transposition and other operations are all performed on the entire matrix data, and have been optimized and accelerated in software or hardware, so they have better results.

[0050] Specifically, the first projection result is calculated as follows:

[0051] If the channel of the first projection result is not an edge channel, the following formula is used for calculation:

[0052] fRawOut i,j,k =(1-α)*fRawIn i,j,k′ +α*fRawIn i,j,(k′+1)

[0053] Among them, fRawOut i,j,k represents the value of the kth channel of the jth row of the i-th first projection result, the channels are sorted from left to right, and the first projection results are sorted in the order of output time; fRawIn i,j,k’ represents the value of the k'th channel of the jth row of the i-th fan-beam projection data; wherein is an integer greater than 0, and its value range is between 1 and the maximum number of rows of the fan-beam projection data; k and k' are both integers greater than 0, and their values ​​range is between 1 and the maximum number of channels of the fan-beam projection data. α represents the weighting coefficient, which is calculated according to the following formula:

[0054] α=ViewIdx i -floor(ViewIdx i )

[0055] Among them, ViewIdx i represents the number of the fan-beam projection data corresponding to the i-th first projection result, floor represents a floor rounding function; and

[0056] If the channel of the first projection result is an edge channel, calculation is performed according to a preset rule.

[0057] That is, most of the data in the first projection result is calculated according to the above formula, and when an edge channel is encountered, the preset rule is used for special processing. In one embodiment, the preset rule is:

[0058] fRawOut i,j,k =fRawIn i,j,k′

[0059] Other preset rules may also be used for processing. The preset rules do not actually affect the content of the central area of ​​the final imaging result, but are only set to prevent program errors.

[0060] The above formulas are all derived and verified through geometric mapping transformation rules, and the specific derivation process will not be described in detail here.

[0061] Furthermore, ViewIdx i Calculated according to the following formula:

[0062]

[0063] Among them, DetAgl i The angle between the line formed by the i-th detector and the emission source and the reference direction is positive, with counterclockwise being the positive direction. The reference direction is the direction from the emission source toward the rotation center. The value of i is an integer from 1 to m, where m is the total number of detectors. AglPerView represents the interval between the data acquisition angles of two adjacent fan-beam projection data. StartAgl is calculated according to the following formula:

[0064]

[0065] Among them, ceil represents the ceiling function.

[0066] In one embodiment, the first storage medium is a memory, and the second storage medium is a CPU cache. The rearrangement method is executed by the CPU. The CPU has a relatively fast read and write speed to the CPU cache, but due to hardware limitations, the CPU cache has a relatively small storage space. The read and write speed of the memory is slower than that of the CPU cache, but it has a relatively large storage space, as described earlier in this specification.

[0067] Based on the results obtained in the above steps, the rearrangement method further comprises: S80 (not shown) reconstructing the parallel beam projection data to obtain a target tomographic image. With such configuration, an intuitive image that is easy for the naked eye to recognize is finally obtained.

[0068] Please refer to Figure 2The present invention also provides a CT scanning device comprising a tube 1 for emitting penetrating rays, a fan-shaped array of detectors 3, and a processing module. A space for accommodating an object 2 is provided between the tube and the detectors. The tube 1 and the detectors 3 can rotate relatively fixedly around the object 2. The specific implementation can be configured according to actual needs. The detector is configured to acquire fan-beam projection data; the processing module is configured to rearrange the fan-beam projection data based on the aforementioned rearrangement method. The processing module may include a CPU or another computing core.

[0069] Other components and working logic of the CT scanning device can be understood and configured according to common knowledge in the art and will not be described in detail here.

[0070] This embodiment further provides a readable storage medium, on which a program is stored. When the program is run, the above-mentioned rearrangement method is executed.

[0071] In summary, in a rearrangement method, a CT scanning device and a readable storage medium provided in this embodiment, the rearrangement method includes the following steps: sequentially acquiring a plurality of the fan-beam projection data according to the data acquisition angle, the fan-beam projection data are sorted in the order of acquisition, and the plurality of the fan-beam projection data constitute basic data; transposing the basic data, and storing the transposed basic data in a first storage medium; reading a row of data along the row direction of the basic data, and the read data is set as intermediate data; storing the intermediate data in a second storage medium; outputting a parallel beam projection data based on the intermediate data in the second storage medium; deleting the current first fan-beam projection data in the basic data; and performing an end judgment. If the result is yes, end; if the result is no, repeatedly acquire the intermediate data. With such a configuration, the internal structure of the basic data is changed through data transposition, so that data related to the same parallel beam projection data exists in the same row of the basic data, reducing the number of accesses to the first storage medium when generating the parallel beam projection data, thereby reducing the rearrangement time, and solving the problem in the prior art that the CT rearrangement algorithm frequently accesses the memory, the speed is too slow, and the reconstruction speed of the entire image reconstruction algorithm is affected.

[0072] The above description is only a description of the preferred embodiment of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure are within the scope of protection of the technical solution of the present invention.

Claims

1. A rearrangement method for converting fan beam projection data into parallel beam projection data, characterized in that: The rearrangement method comprises the following steps: sequentially acquiring a plurality of the fan-beam projection data according to a data acquisition angle, wherein the fan-beam projection data are sorted according to a sequence of acquisition, and the plurality of the fan-beam projection data constitute basic data; Transposing the basic data, and storing the transposed basic data in a first storage medium; Reading a row of data along the row direction of the basic data, and setting the read data as intermediate data; The intermediate data is stored in a second storage medium; outputting the parallel beam projection data based on the intermediate data in the second storage medium; Deleting the first current fan-beam projection data in the basic data; as well as, Perform an end judgment, if the result is yes, then end; if the result is no, repeat to obtain the intermediate data.

2. The rearrangement method according to claim 1, characterized in that The storage capacity of the first storage medium is greater than a preset multiple of the storage capacity of the second storage medium, and the read and write speed of the second storage medium is greater than the read and write speed of the first storage medium.

3. The rearrangement method according to claim 2, characterized in that The preset multiple is the maximum number of the fan-beam projection data in the basic data.

4. The rearrangement method according to claim 2, characterized in that The logic of the end judgment is: whether the number of the fan beam projection data remaining in the basic data is less than the number required to calculate one parallel beam projection data; if so, the result is yes; otherwise, the result is no.

5. The rearrangement method according to claim 2, characterized in that The first storage medium is a memory, and the second storage medium is a CPU cache.

6. The rearrangement method according to claim 1, characterized in that The required amount of the parallel beam projection data is determined according to CT geometric parameters, which include detector angles and / or the number of detectors.

7. The rearrangement method according to claim 1, characterized in that The step of outputting the parallel beam projection data based on the intermediate data in the second storage medium comprises: Calculating a first projection result based on the intermediate data in the second storage medium; The first projection result is transposed to obtain a second projection result; and The second projection result is configured as the parallel beam projection data and output.

8. The rearrangement method according to claim 1, characterized in that The method further comprises: The parallel beam projection data is reconstructed to obtain a target tomographic image.

9. A CT scanning device, characterized in that: The invention comprises a tube for emitting penetrating rays, detectors distributed in a fan shape, and a processing module, wherein a space for accommodating an object to be measured is provided between the tube and the detector, the tube and the detector can rotate relatively fixedly around the object to be measured, and the detector is used to obtain fan beam projection data; the processing module is used to rearrange the fan beam projection data based on the rearrangement method described in any one of claims 1 to 8.

10. A readable storage medium, characterized in that: The readable storage medium stores a program, and when the program is run, the rearrangement method according to any one of claims 1 to 8 is executed.

Images