CN115227285A - Post-processing calibration method for swing angle offset of ultrasonic volume probe - Google Patents

Post-processing calibration method for swing angle offset of ultrasonic volume probe Download PDF

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CN115227285A
CN115227285A CN202210734749.3A CN202210734749A CN115227285A CN 115227285 A CN115227285 A CN 115227285A CN 202210734749 A CN202210734749 A CN 202210734749A CN 115227285 A CN115227285 A CN 115227285A
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高彩红
陶书僮
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Nanjing Medical Technology Co ltd
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    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/58—Testing, adjusting or calibrating the diagnostic device
    • A—HUMAN NECESSITIES
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    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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Abstract

The invention provides a post-processing calibration method for swing angle deviation of an ultrasonic volume probe. When scanning data is uploaded, the signal change of a probe sensor is detected in real time, the change information is packaged into head information of a current scanning line, a computer marks a current frame image and the current scanning line after analyzing the signal, an angle deviation is calculated after a reversing signal of a stepping motor is detected, the angle deviation is sent to a three-dimensional data generation module, a three-dimensional output image is calibrated in real time, and the problems of angle deviation and image shaking are avoided. The method adopts a post-processing mode, is simple and flexible, and has higher calibration precision for motor control self-calibration.

Description

Post-processing calibration method for swing angle offset of ultrasonic volume probe
Technical Field
The invention relates to the technical field of ultrasonic volume probe imaging.
Background
Ultrasonic four-dimensional imaging has been widely used as an auxiliary diagnostic tool, especially in the aspects of gynaecology and obstetrics, pelvic floor, heart, etc. The four-dimensional imaging is characterized in that a stepping motor is controlled to rotate, multiple pieces of two-dimensional data of human tissues and organs are obtained by matching with real-time scanning, then three-dimensional volume data are generated by the two-dimensional images in a three-dimensional interpolation mode, different section images and surface remade images of the tissues and organs are displayed through certain post-processing, and more diagnosis information is provided for doctors.
The ultrasonic four-dimensional imaging generally uses a volume probe with a stepping motor, and volume scanning is realized by controlling the stepping motor to drive an ultrasonic one-dimensional array transducer to swing inside the probe. The probe driving interface is provided with a motor driving lead and a positioning sensor lead, the output level of the sensor can change in the swing process of the transducer, the level changing position is the reference zero position of the probe, and the probe generally needs to return to zero before and after three-dimensional four-dimensional scanning, so that the probe swings with the current position as the center. The motion of the stepping motor is subjected to forward acceleration, uniform speed, deceleration, reverse acceleration, uniform speed and deceleration, the process is repeated, and if the rotating speed of the stepping motor is too high, phenomena of overshoot during deceleration and step loss during acceleration are easy to occur before and after reversing. For example, chinese patent No. CN106725601B proposes an automatic calibration method for a stepping motor, which obtains an actual step count value of a central point (i.e., a reference zero position) where a probe reaches a uniform velocity zone in a current period, and obtains a step count error caused by step loss or overshoot of the stepping motor in the current period based on the actual step count value and a preset step count, and then performs step count compensation by using the step count error in a next period to solve the problem of forward and backward scanning swing angle offset. However, although the method proposed in this patent can solve the problem of angular offset to some extent, the step motor control cannot realize precise control of non-integer steps, and the actual step counting number usually adopts integer counting, so that the calibration result has an error of one step angle at the maximum, and a better imaging effect cannot be achieved under the influence of the step angle error.
Disclosure of Invention
The purpose of the invention is as follows: the problems of forward and reverse scanning swing angle deviation and image shaking caused by overshoot caused by step loss and deceleration due to acceleration of a stepping motor during four-dimensional imaging of the ultrasonic volume probe are solved.
The technical scheme is as follows: in order to solve the above problems, the present invention provides a method for post-processing calibration of swing angle offset of an ultrasonic volume probe, comprising
A post-processing calibration method for swing angle offset of an ultrasonic volume probe comprises the following steps:
(1) Starting a four-dimensional scan, initializing a frame count signal nCount =0, sensor =0; the SENSOR represents a variable corresponding to the SENSOR level change indicating signal;
(2) The probe starts to transmit and receive signals to scan a certain line, the change of the SENSOR is detected, and if the head information of the scanning line does not exist, the corresponding position is set to be 0; if the head information of the scanning line changes, the corresponding position is set as 1;
(3) The upper computer analyzes each line of data in real time: the upper computer analyzes the head information of a certain line through a data thread, the scanning line number CurLine, a SENSOR, a motor direction signal Dir and the current frame number CurFrame are respectively obtained from a fixed position, if the line detects that SENSOR =1, a frame indicating signal bMid =1 is arranged in the middle of the frame, and the middle position of the frame corresponds to the line number nMidposLine = CurLine; if SENSOR =0, then bMid =0, nMudPosLine =0;
(4) The upper computer calculates three-dimensional data calibration parameters according to the analysis information of the current frame: when the three-dimensional processing module analyzes that the current frame number SENSOR =1, the current frame number CurFrame, the line number nModPosLine corresponding to the frame middle position and the motor direction information Dir are read, the frame calibration value is:
iFrame _ mod = CurFrame- (NFrame-1)/2.0 + (CurLine- (NLine-1)/2.0)/(NLine-1); the iFrame _ mod is used for calculating a difference value between an original storage center frame and a frame where an actual motor is located when the motor is in zero crossing;
(6) Calculating three-dimensional volume data in real time according to the calibration parameters: when mapping from original volume data to three-dimensional volume data, the position [ iPot, iLine, iFrame ] of the original volume data corresponding to each pixel point in the mapping table, and [ iPot, iLine, iFrame ] represent the spatial storage position of the iFrame frame, the iFrame scan line and the iPot sampling point in the original volume data, and iFrame is calibrated by iFrame _ mod to obtain a new frame number iFrameNew = iFrame + iFrame _ mod.
Further, in the step (2), after a line scanning starts, the system detects a change in SENSOR level in real time, if the change in SENSOR level is detected before the header information is packed, the SENSOR =1 is packed into the header information, and then the header information is uploaded, and the SENSOR =0 is packed after the end of the packing; if the header information is packed, the next line scan is not started, the next line scan header information is packed with SENSOR =1, and the packing is finished with SENSOR =0.
Further, the header information further includes a scan line number CurLine, a motor direction signal Dir, and a current frame number CurFrame.
Further, in step (3), the upper computer parses the data thread into 0xAA55 sector in the header information of a certain line.
Further, the calculation process of the scan conversion mapping table is as follows: firstly, calculating the actual physical dimensions [ Dx, dy, dz ] of the three-dimensional data in the vertical, front, rear, left and right directions, wherein X, Y and Z respectively represent the scanning line direction, the three-dimensional frame arrangement direction and the scanning point direction of the three-dimensional data, dx, dy and Dz respectively correspond to the actual lengths of the three-dimensional data in the X, Y and Z directions, the circle center position of the intermediate frame image probe is taken as the origin of coordinates [0, 0], the rotation center of the fan-scanning image is taken as [0, R-R ],
Dz＝r+De-(r+Ds)*cos(Ω/2)；
Dx＝(r+De)*sin(Ω/2)*2；
Dy＝(R+De)*sin(W/2)*2；
r is the probe radius; ds is the initial depth of probe scanning; de is the probe scanning cut-off depth; omega is the scanning angle of the probe array direction; r is the sweep radius of the probe; w is the sweeping angle
Secondly, calculating the actual pixel size [ Nx, ny, nz ] of the three-dimensional volume data, wherein the Nx, the Ny and the Nz respectively correspond to the pixel points of the X, the Y and the Z directions of the three-dimensional volume, and Nmax _ Z is the maximum pixel point preset in the Z direction of the three-dimensional volume data, then
Nz = Nmax _ z, and the physical distance dpixle = Dz/Nz between the pixel points is calculated;
Nx＝int(Dx/dpixle)；
Ny＝int(Dy/dpixle)；
then, calculating the position [ iPot, iLine, iFrame ] of each pixel point in the three-dimensional volume data corresponding to the original volume data, wherein the position variables are float types, assuming that a certain pixel point [ nx, ny, nz ] in the space respectively represents the position of the certain pixel point in the X, Y and Z directions of the three-dimensional volume, and the calculating method corresponding to the position [ iPot, iLine, iFrame ] of the original volume data is as follows:
original volume data mid-frame number dCenFrame, dCenFrame = (Nframe-1)/2.0 before calibration, distance dp between original volume data points = (De-Ds)/NPot.
The coordinate of a pixel point on the three-dimensional volume data, which corresponds to the volume data storage space, is [ Nx _ oR, ny _ oR,0], the coordinate of a pixel point at the rotation center of the fan-scan image is [ Nx _ oR, ny _ oR, nz _ oR ], wherein Nx _ oR = (Nx-1)/2.0, ny \uoR = (Ny-1)/2.0, nz _oR = (- (R + Ds) + (R-R)) > cos (omega/2)/dpi xle.
The pixel distance N _ pixeltooR from the pixel point [ nx, ny, nz ] to the rotation center of the fan-scan image is
N_pixelTooR＝sqrt((nx-nx_oR) 2 +(ny-ny_oR) 2 +(nz-nz_oR) 2 )；
Then
iFrame = asin [ (ny-ny _ oR)/N _ pixelTooR ]/w + dCenFrame; w is the included angle radian between two adjacent frame images
iLine＝asin[(nx-nx_oR)/N_pixelTooR]/θ+(nLine-1)/2.0
iPot＝{sqrt{[(sqrt(N_pixelTooR 2 -(nx-nx_oR) 2 )*dpixle+(r-R)] 2 +(nx-nx_oR) 2 *dpixle 2 }-r-s}/dp
And (4) sequentially calculating [ iPot, iLine and iFrame ] corresponding to each pixel point in the three-dimensional volume data, and outputting a scan conversion mapping table, wherein the mapping table is a floating point type value.
Furthermore, the original mapping table is only calculated once, and when the three-dimensional volume data is calculated in real time, the corresponding frame values in the table are calibrated and then processed by interpolation and the like.
Further, after scanning starts, firstly, rotating the motor to find out the level change of the sensor, enabling the probe to return to zero, then, enabling the motor to rotate at a constant speed and start to count Nstep/2 from zero, and enabling the motor to decelerate; and then, after the motor reversely accelerates for a fixed time length, starting to enter a constant speed interval, controlling the probe to start transmitting to obtain NFrame frame image data, wherein the size of a single frame image is set to be [ NPot, NLine ], NPot represents the number of sampling points of each scanning line in the single frame image, NLine represents the number of scanning lines of the single frame image, and a certain point in the original data is represented as [ iPot, iLine, iFrame ].
Further, the header information includes a current scanning line number CurLine, a sensor level change indication signal, a motor direction Dir, and a current scanning frame number CurFrame, where a sensor level change indication signal of 0 indicates no change; a sensor level change indication signal of 1 indicates a change; a motor direction Dir of 0 indicates a forward direction; a motor direction Dir of 1 indicates the reverse direction.
Has the beneficial effects that: the invention provides a post-processing calibration method for swing angle deviation of an ultrasonic volume probe. When scanning data is uploaded, the signal change of a probe sensor is detected in real time, the change information is packaged into head information of a current scanning line, a computer marks a current frame image and the current scanning line after analyzing the signal, an angle deviation is calculated after a reversing signal of a stepping motor is detected, the angle deviation is sent to a three-dimensional data generation module, a three-dimensional output image is calibrated in real time, and the problems of angle deviation and image shaking are avoided. The method adopts a post-processing mode, is simple and flexible, and has higher calibration precision for the motor control self-calibration.
The invention also provides a computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps of the above method when executing the computer program.
The invention also provides a computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the above-mentioned method.
Drawings
FIG. 1 is a flow chart illustrating a method for post-processing calibration of the swing angle offset of an ultrasonic volume probe according to the present invention;
FIG. 2 is a flowchart illustrating the calculation of a scan conversion mapping table according to the present invention;
FIG. 3 shows a coronal image of a motor positive-negative scan of a body membrane without self-calibration;
figure 4 shows a coronal image of a motor positive and negative scan body film with self-calibration added.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
The basic theory of the technical scheme provided by the invention is as follows:
the motor motion mode of the ultrasonic volume probe can be convex array fan scanning, convex array flat scanning, linear array fan scanning and linear array flat scanning. The probe collects original data of a frame of two-dimensional image in the moving process, and after one scanning period is finished (after the motor changes the direction, the speed is reduced from left swing to right swing or from right swing to left swing to one period), original volume data can be obtained, the data are not real three-dimensional volume data, the physical distance among the data is not uniform, the original volume data need to be scanned and converted, and real ultrasonic three-dimensional volume data are generated. The scan conversion process needs to be calculated separately according to different motion modes.
The process is briefly described below by taking the convex array fan scan as an example.
Assuming that the radius of the probe is R (unit mm), the scanning angle in the array direction of the probe is Ω, the included angle radian between adjacent scanning lines is θ, the scanning start depth is Ds (distance to the surface of the probe), the scanning stop depth is De (distance to the surface of the probe), the sweep radius of the probe is R (unit mm), the included angle radian between two adjacent frames of images is w, the number of frames to be collected is NFrame, and the maximum pixel size of preset volume data is [ Nmax _ x, nmax _ y, nmax _ z ] respectively. To keep the forward and reverse fan-scan positions overlapping, the scan lines of the forward scan are typically taken, e.g., from 0 to N-1; the scan lines of the reverse scan are taken, for example, from N-1 to 0. Because the motor operates at a constant speed during scanning, ideally, the forward and reverse scanning zero-crossing points correspond to the middle frame of the fan-scanned image and the middle scanning line thereof (odd frame scanned image), or correspond to the connection between the ending line of two frames adjacent to the middle and the starting line of the next frame (even frame scanned image).
Motor control and generation process of original volume data: after setting the fan scanning angle W, the user calculates the number of steps Nstep (to prevent the number of steps from being insufficient, the number of steps Nstep may be an even number) during the constant speed period of the motor according to the current working parameters of the probe. The motor is first rotated to find the sensor level change, the probe is zeroed, then the motor is rotated at a constant speed and begins counting Nstep/2 from zero, the motor is decelerated (the probe does not have to be fired before, just to find the sector sweep boundary). And then, after the motor reversely accelerates for a fixed time length, starting to enter a constant speed interval, controlling the probe to start transmitting to obtain NFrame frame image data, wherein the size of a single frame image is set as [ NPot, NLine ], the NPot and the NLine respectively represent the number of sampling points of each scanning line in the single frame image and the number of scanning lines of the frame image, and a certain point in the original data can be represented as [ iPot, iLine, iFrame ], namely the spatial storage position of an iFrame frame, an iLine scanning line and an iPot sampling point in the original volume data. It is noted that the counting of the forward and reverse frame numbers can be performed in a forward increasing manner, a reverse decreasing manner, or a forward increasing manner, a reverse increasing manner (the first manner is adopted by default in this description). Generally, each line (or each frame) of original data uploaded contains header information, which may include the following (only information relevant to the description of the present technical solution is listed):
Figure BDA0003715297390000051
scan conversion is a process of generating three-dimensional volume data from original volume data, and generally, according to user settings, a set of mapping tables is calculated to map the original volume data into the three-dimensional volume data, which only needs to be calculated once.
Based on the above description of the basic theory, the present invention provides a post-processing calibration method for the swing angle offset of an ultrasonic volume probe, as shown in fig. 1, including the following steps:
step1: starting a four-dimensional scan, initializing a frame count signal nCount =0 and SENSOR =0 (where SENSOR represents a variable corresponding to the SENSOR level change indication signal);
the initialization parameters include the calculation process of the scan conversion mapping table. Referring to fig. 2, an embodiment of the calculation process of the scan conversion mapping table is to calculate the actual physical dimensions [ Dx, dy, dz ] of the three-dimensional volume data, up, down, front, back, left, right, and left, wherein X, Y, and Z respectively represent the scanning line direction, the three-dimensional volume frame arrangement direction, and the scanning point direction (X/Y/Z, and X/_ Y/_ Z mentioned in this embodiment are all consistent with the description herein), dx, dy, and Dz respectively correspond to the actual lengths of the three-dimensional volume in the X, Y, and Z directions, and the center position of the center of the middle frame image probe is the origin of coordinates [0, 0], and the rotation center of the fan-scan image is [0, R-R ] (for simplicity, the height of the middle frame image is used as the imaging height of the three-dimensional volume data),
Dz＝r+De-(r+Ds)*cos(Ω/2)；
Dx＝(r+De)*sin(Ω/2)*2；
Dy＝(R+De)*sin(W/2)*2；
secondly, calculating the actual pixel size [ Nx, ny, nz ] of the three-dimensional volume data;
nz = Nmax _ z, and the physical distance dpixle = Dz/Nz between the pixel points is calculated;
Nx＝int(Dx/dpixle)；
Ny＝int(Dy/dpixle)；
then, calculating the position [ iPot, iLine, iFrame ] of each pixel point in the three-dimensional volume data corresponding to the original volume data, wherein the position variables are float types, assuming that a certain pixel point [ nx, ny, nz ] in the space respectively represents the position of the certain pixel point in the X, Y and Z directions of the three-dimensional volume, and the calculating method corresponding to the position [ iPot, iLine, iFrame ] of the original volume data is as follows:
original volume data mid-frame number dCenFrame, dCenFrame = (Nframe-1)/2.0 before calibration, distance dp between original volume data points = (De-Ds)/NPot.
The coordinate of a pixel point on the three-dimensional volume data, which corresponds to the volume data storage space, is [ Nx _ oR, ny _ oR,0], the coordinate of a pixel point at the rotation center of the fan-scan image is [ Nx _ oR, ny _ oR, nz _ oR ], wherein Nx _ oR = (Nx-1)/2.0, ny \uoR = (Ny-1)/2.0, nz _oR = (- (R + Ds) + (R-R)) > cos (omega/2)/dpi xle.
The pixel distance from the pixel point [ nx, ny, nz ] to the rotation center of the fan-scan image is
N_pixelTooR＝sqrt((nx-nx_oR) 2 +(ny-ny_oR) 2 +(nz-nz_oR) 2 )；
Then
iFrame＝asin[(ny-ny_oR)/N_pixelTooR]/w+dCenFrame；
iLine＝asin[(nx-nx_oR)/N_pixelTooR]/θ+(nLine-1)/2.0
iPot＝{sqrt{[(sqrt(N_pixelTooR 2 -(nx-nx_oR) 2 )*dpixle+(r-R)] 2 +(nx-nx_oR) 2 *dpixle 2 }-r-s}/dp
And sequentially calculating [ iPot, iLine and iFrame ] corresponding to each pixel point in the three-dimensional volume data, and outputting a scanning transformation mapping table, wherein the mapping table is a floating point type value.
And after the four-dimensional scanning is started, receiving the original volume data in real time, and performing scanning conversion to obtain three-dimensional volume data. The scan conversion process may directly round the mapping table values and extract the corresponding raw data values as the values of the pixels. The value of the pixel may also be calculated by linear interpolation or spline interpolation (linear interpolation or spline interpolation is a well-known method and will not be described here).
Step2: the probe starts to transmit and receive signals, detects the change of the SENSOR, and responds if the head information does not exist
Position 0; if the position is changed, the corresponding position is set to 1.
The specific implementation mode is as follows: after a certain line scanning starts, the system detects the change of the SENSOR level in real time, if the change of the SENSOR level is detected before the head information is packaged, the SENSOR =1 is packaged into the head information, then the head information is uploaded, and the SENSOR =0 is packaged; if the header information is packed, the next line scan is not started, the next line scan header information is packed with SENSOR =1, and the packing is finished with SENSOR =0.
The header information also contains a scan line number CurLine, a motor direction signal Dir, and a current frame number CurFrame.
Step3: and the upper computer analyzes each line of data in real time.
The specific implementation mode is as follows: the upper computer analyzes the data thread to 0xAA55 in the head information of a certain line, respectively obtains the scanning line number CurLine, SENSOR, a motor direction signal Dir and the current frame number CurFrame from a fixed position, if the line detects SENSOR =1, the frame middle position frame indicating signal bMid =1, and the frame middle position corresponds to the line number nMosLine = CurLine; if SENSOR =0, then bMid =0, nMudPosLine =0;
step4: the upper computer calculates three-dimensional data calibration parameters according to the analysis information of the current frame
The specific implementation mode is as follows: when the three-dimensional processing module analyzes the current frame SENSOR =1, reading the current frame number
CurFrame, and the frame middle position corresponds to the line number nMidPosLine, the motor direction information Dir, then the frame calibration value iFrame _ mod = CurFrame- (NFrame-1)/2.0 + (CurLine- (NLine-1)/2.0)/(NLine-1)
The iFrame _ mod is a difference value between the original storage center frame and a frame where the actual motor is located when the frame crosses zero.
Step5: real-time computation of three-dimensional volume data from calibration parameters
The specific implementation mode is as follows: when mapping from original volume data to three-dimensional volume data, the position [ iPot, iLine, iFrame ] of the original volume data corresponding to each pixel point in the mapping table is calibrated by iFrame _ mod to obtain a new frame number iFrameNew = iFrame + iFrame _ mod.
It should be noted that the original mapping table only needs to be calculated once, and when the three-dimensional volume data is calculated in real time, the corresponding frame values in the table are calibrated and then processed by interpolation and the like.
When the constant speed of the probe exceeds 250 degrees/s, the displacement of the coronal image of the forward and backward scanning of the motor is obvious, the number of steps of step-missing and overshoot is large, the lower graph 3 shows that the coronal image of the body membrane of the forward and backward scanning (the standard ultrasound body membrane of the Chinese academy is used in the image) is not subjected to self-calibration, and the change of the target spot at the deeper part is large, which is caused by the forward and backward scanning position deviation of the motor stepping motor.
The reduction ratio of the volume probe motor in fig. 3 is 4.29, the rotation angle of the probe is 0.4196 degrees when the stepping motor advances for 1 step, and the uniform motion speed of the motor is about 256.1 degrees/s. After the post-processing self-calibration is added, the actual displacement and the expected error in the uniform speed interval are controlled to be the angle of the motor travelling in the single-line scanning time, the single-line scanning time in fig. 3 is about 174us, the error is smaller than 0.0446 degrees, the error depends on the length of the single-line scanning time, the depth in the general four-dimensional mode does not exceed 20cm, the error is smaller than 0.0796 degrees and smaller than the single-step rotation angle of the motor, fig. 4 is a coronal image obtained by the forward scanning and the reverse scanning of the motor stepping motor after the post-processing self-calibration is added, the displacement error cannot be seen by naked eyes in the two images, and the calibration precision is higher.
The embodiment has no requirement on whether a motor control self-calibration method (such as the method mentioned in patent document CN 106725601B) is adopted, and a small displacement error can be realized without adopting the motor control self-calibration method.

Claims (10)

1. A post-processing calibration method for swing angle offset of an ultrasonic volume probe is characterized by comprising the following steps:
(1) Starting a four-dimensional scanning, initializing a frame counting signal nCount =0, and SENSOR =0; SENSOR represents a variable corresponding to the SENSOR level change indication signal;
(2) The probe starts to transmit and receive signals to scan a certain line, the change of the SENSOR is detected, and if the head information of the scanning line does not exist, the corresponding position is set to be 0; if the head information of the scanning line changes, the corresponding position is set as 1;
(3) The upper computer analyzes each line of data in real time: the upper computer analyzes the head information of a certain line through a data thread, the scanning line number CurLine, a SENSOR, a motor direction signal Dir and the current frame number CurFrame are respectively obtained from a fixed position, if the line detects that SENSOR =1, a frame indicating signal bMid =1 is arranged in the middle of the frame, and the middle position of the frame corresponds to the line number nMidposLine = CurLine; if SENSOR =0, then bMid =0, nMidPosLine =0;
(4) The upper computer calculates three-dimensional data calibration parameters according to the analysis information of the current frame: when the three-dimensional processing module analyzes that the current frame number SENSOR =1, the current frame number CurFrame, the line number nModPosLine corresponding to the frame middle position and the motor direction information Dir are read, the frame calibration value is:
iFrame_mod＝CurFrame-(NFrame-1)/2.0+(CurLine-(NLine-1)/2.0)/(NLine-1)；
the iFrame _ mod is used for calculating a difference value between an original storage center frame and a frame where an actual motor is located when the motor crosses zero;
(5) And calculating three-dimensional volume data in real time according to the calibration parameters: when mapping from the original volume data to the three-dimensional volume data, the position [ iPot, iLine, iFrame ] of the original volume data corresponding to each pixel point in the mapping table,
[ iPot, iLine, iFrame ] represents the spatial storage position of the iFrame frame, iLine scan line and iPot sampling point in the original volume data, and the iFrame is calibrated by using iFrame _ mod to obtain a new frame number iFrameNew = iFrame + iFrame _ mod.
2. The method for post-processing calibration of the swing angle offset of the ultrasonic volume probe according to claim 1, wherein in step (2), after a line scan is started, the system detects the change of SENSOR level in real time, if the change of SENSOR level is detected before the header information is packed, the SENSOR =1 is packed into the header information, and then the header information is uploaded and the SENSOR =0 is packed after the end of the packing; if the header information is packed, the next line scan is not started, the next line scan header information is packed with SENSOR =1, and the packing is finished with SENSOR =0.
3. The method of post-processing calibration of ultrasonic volume probe oscillation angle offset of claim 2, wherein the header information further comprises a scan line number CurLine, a motor direction signal Dir, and a current frame number CurFrame.
4. The method for post-processing calibration of the swing angle offset of the ultrasonic volume probe as claimed in claim 1, wherein in step (3), the upper computer analyzes the data thread to 0xAA55 sector in the header information of a certain line.
5. The method for post-processing calibration of the swing angle offset of the ultrasonic volume probe according to claim 2, wherein the scan conversion mapping table is calculated by: firstly, calculating the actual physical dimensions [ Dx, dy, dz ] of three-dimensional data in the vertical, front, rear, left and right directions, wherein X, Y and Z respectively represent the scanning line direction, the three-dimensional frame arrangement direction and the scanning point direction of the three-dimensional data, dx, dy and Dz respectively correspond to the actual lengths of the three-dimensional data in the X, Y and Z directions, the center of circle of an image probe of an intermediate frame is taken as the origin of coordinates [0, 0], the rotation center of a fan-scanned image is taken as [0, R-R ],
Dz＝r+De-(r+Ds)*cos(Ω/2)；
Dx＝(r+De)*sin(Ω/2)*2；
Dy＝(R+De)*sin(W/2)*2；
r is the probe radius; ds is the initial depth of probe scanning; de is the probe scanning cut-off depth; omega is the scanning angle of the probe array direction; r is the sweep radius of the probe; w is the fan sweep angle
Secondly, calculating the actual pixel size [ Nx, ny, nz ] of the three-dimensional volume data, wherein the Nx, the Ny and the Nz respectively correspond to the pixel points of the X, the Y and the Z directions of the three-dimensional volume, and Nmax _ Z is the maximum pixel point preset in the Z direction of the three-dimensional volume data, then
Nz = Nmax _ z, and the physical distance dpixle = Dz/Nz between the pixel points is calculated;
Nx＝int(Dx/dpixle)；
Ny＝int(Dy/dpixle)；
then, calculating the position [ iPot, iLine, iFrame ] of each pixel point in the three-dimensional volume data corresponding to the original volume data, wherein the position variables are float types, assuming that a certain pixel point [ nx, ny, nz ] in the space respectively represents the position of the certain pixel point in the X, Y and Z directions of the three-dimensional volume, and the calculating method corresponding to the position [ iPot, iLine, iFrame ] of the original volume data is as follows:
original volume data mid-frame number dCenFrame, dCenFrame = (Nframe-1)/2.0 before calibration, distance dp between original volume data points = (De-Ds)/NPot.
The coordinate of a pixel point on the three-dimensional volume data, which corresponds to the volume data storage space, is [ Nx _ oR, ny _ oR,0], the coordinate of a pixel point at the rotation center of the fan-scan image is [ Nx _ oR, ny _ oR, nz _ oR ], wherein Nx _ oR = (Nx-1)/2.0, ny \uoR = (Ny-1)/2.0, nz _oR = (- (R + Ds) + (R-R)) > cos (omega/2)/dpi xle.
The pixel distance N _ pixeltooR from the pixel point [ nx, ny, nz ] to the rotation center of the fan-scan image is
N_pixelTooR＝sqrt((nx-nx_oR) 2 +(ny-ny_oR) 2 +(nz-nz_oR) 2 )；
Then the
iFrame = asin [ (ny-ny _ oR)/N _ pixelTooR ]/w + dCenFrame; w is the radian of an included angle between two adjacent frames of images
iLine＝asin[(nx-nx_oR)/N_pixelTooR]/θ+(nLine-1)/2.0
iPot＝{sqrt{[(sqrt(N_pixelTooR 2 -(nx-nx_oR) 2 )*dpixle+(r-R)] 2 +(nx-nx_oR) 2 *dpixle 2 }-r-s}/dp
And sequentially calculating [ iPot, iLine and iFrame ] corresponding to each pixel point in the three-dimensional volume data, and outputting a scanning transformation mapping table, wherein the mapping table is a floating point type value.
6. The method for post-processing calibration of ultrasonic volume probe swing angle offset according to claim 5, wherein the original mapping table is calculated once, and the corresponding frame values in the table are calibrated and then processed by interpolation or the like when the three-dimensional volume data is calculated in real time.
7. The method of post-processing calibration of the swing angle offset of an ultrasonic volumetric probe as defined in any of claims 1 to 6 wherein after scanning begins, the motor is first rotated to find the sensor level change, the probe is zeroed, then the motor is rotated at a constant speed and begins counting from zero Nstep/2, the motor is decelerated; and then, after the motor reversely accelerates for a fixed time length, starting to enter a constant speed interval, controlling the probe to start transmitting to obtain NFrame frame image data, wherein the size of a single frame image is set to be [ NPot, NLine ], NPot represents the number of sampling points of each scanning line in the single frame image, NLine represents the number of scanning lines of the single frame image, and a certain point in the original data is represented as [ iPot, iLine, iFrame ].
8. The method for post-processing calibration of the swing angle offset of the ultrasonic volume probe according to any one of claims 1 to 6, wherein the header information comprises a current scanning line number CurLine, a sensor level change indication signal, a motor direction Dir, and a current scanning frame number CurFrame, wherein a sensor level change indication signal of 0 indicates no change; a sensor level change indication signal of 1 indicates a change; a motor direction Dir of 0 indicates a forward direction; a motor direction Dir of 1 indicates reverse.
9. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the steps of the method of claims 1 to 8 are implemented by the processor when executing the computer program.
10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of claims 1 to 8.
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