CN109875589B - Method and device for measuring centering error of vascular machine system - Google Patents
Method and device for measuring centering error of vascular machine system Download PDFInfo
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- CN109875589B CN109875589B CN201910086758.4A CN201910086758A CN109875589B CN 109875589 B CN109875589 B CN 109875589B CN 201910086758 A CN201910086758 A CN 201910086758A CN 109875589 B CN109875589 B CN 109875589B
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Abstract
The application discloses a method and a device for measuring centering errors of a vascular machine system. According to the method, the centering error of the beam limiter and the detector can be calculated according to a linear equation of each boundary of the visual field in a detector coordinate system; the linear equation can be obtained from the X-ray image, which can be obtained by the view of the beam limiter. Therefore, all the processes of the measuring method are completely carried out by a machine without manual participation, and the full-automatic measurement of the centering error can be realized by the measuring method provided by the application. The measuring method has the characteristics of real time, rapidness and accuracy.
Description
Technical Field
The application relates to the technical field of medical imaging, in particular to a method and a device for measuring centering errors of a vascular machine system.
Background
The vascular machine is a medical imaging device for assisting a doctor in performing an examination or operation. It dynamically displays images of internal tissues of the human body by means of X-rays. Vascular machines are typically composed of a gantry, which serves to support the patient, and a couch, which is the primary imaging device. As shown in fig. 1, the gantry is typically in the form of a C-arm with one end holding the X-ray tube ball assembly 11 and one end holding the detector 12. The X-ray tube assembly 11 is an X-ray emitting device and the detector 12 is an X-ray receiving device. The X-ray tube assembly 11 further comprises a tube 111 and a beam limiter 112, wherein the radiation emitted by the tube 111 is limited to a rectangular area by the beam limiter 112, and the area of the specific shape is called a field of view, which is also called FOV (Field of View). FOV generally refers to the size of the X-ray field of view at the detector surface. The field of view must fall within the detector for dose saving reasons, otherwise the portion beyond the detector cannot be imaged, which is equivalent to letting the patient receive extra X-rays, which is harmful to the body. To achieve this, the FOV of beam limiter 112 and detector 12 must be centered so that the range of the FOV on the detector can be deduced from the distance between the detector and the bulb.
In practice, the beam limiter 112 sometimes needs to be rotated, and the detector 12 also needs to be rotated synchronously in order to maintain the FOV of the beam limiter 112 and the alignment of the detector 12. And there may be a certain error between the synchronous rotations of the two, especially after long-term use, the synchronous error may accumulate and increase, which reduces the accuracy of synchronous rotation of the FOV of the beam limiter 112 and the detector 12, and further affects the centering accuracy of the FOV of the beam limiter 112 and the detector 12.
Therefore, in order to ensure the centering accuracy of the FOV of the beam limiter 112 and the detector 12, it is necessary to measure the centering error of the beam limiter 112 and the detector 12. However, the measurement of the alignment errors of the existing beam limiter 112 and detector 12 can only take an image after rotation, and the measurement is performed manually in the image, resulting in a long time consuming measurement process and inaccurate measurement results.
Disclosure of Invention
In view of the foregoing, the present application provides a method and apparatus for measuring centering errors of an vascular machine system to reduce the time consuming of the measurement process and to improve the accuracy of the measurement results.
In order to solve the technical problems, the application adopts the following technical scheme:
a method of measuring a centering error of a vascular machine system, the vascular machine system including a beam limiter and a detector, the method comprising:
Adjusting the size of the field of view of the beam limiter so that the field of view of the beam limiter is in the detector;
shooting an X-ray film according to the adjusted view of the beam limiter so as to generate an X-ray image on the detector;
acquiring a linear equation of each boundary of the visual field in a detector coordinate system according to the X-ray image;
and calculating the centering error of the beam limiter and the detector according to the linear equation of each boundary of the visual field in the detector coordinate system.
Optionally, the outline of the field of view is rectangular, and the acquiring a linear equation of each boundary of the field of view in a detector coordinate system according to the X-ray image specifically includes:
respectively acquiring linear equations of two opposite boundaries in the first direction of the visual field in a detector coordinate system according to the X-ray images;
respectively acquiring linear equations of two opposite boundaries in a second direction of the visual field in a detector coordinate system according to the X-ray images;
wherein the first direction is perpendicular to the second direction.
Optionally, the acquiring, according to the X-ray image, a linear equation of two boundaries opposite to each other in the first direction of the field of view in the coordinate system of the detector specifically includes:
acquiring X-ray signals at a first reference line and a second reference line of the X-ray image; the first reference line and the second reference line are intersected with two boundaries opposite to each other in the first direction of the visual field, and the intersection point of the two boundaries opposite to each other in the first direction of the visual field are different from each other;
Acquiring boundary points on two opposite boundaries in the first direction of the visual field according to X-ray signals at the first reference line and the second reference line;
and acquiring a linear equation of each boundary in the first direction of the visual field in a detector coordinate system according to the boundary points on each two boundaries in the first direction of the visual field.
Optionally, the X-ray signals at the first reference line and the second reference line are both sequence signals;
the acquiring boundary points on two opposite boundaries in the first direction of the visual field according to the X-ray signals at the first reference line and the second reference line specifically comprises:
differentiating the front and rear terms of the X-ray signals at the first reference line and the second reference line to obtain differential signal distribution diagrams at the first reference line and the second reference line; each differential signal distribution diagram comprises extreme points, and the extreme points in each differential signal distribution diagram are boundary points on each boundary in the first direction of the visual field.
Optionally, the second reference line is a plurality of positions in the X-ray image.
Optionally, after the acquiring the X-ray signals at the first reference line and the second reference line of the X-ray image, before the acquiring the boundary points located on two boundaries opposite in the first direction of the field of view according to the X-ray signals at the first reference line and the second reference line, the method further includes:
Denoising X-ray signals at a first reference line and a second reference line of the X-ray image;
the acquiring boundary points on two opposite boundaries in the first direction of the visual field according to the X-ray signals at the first reference line and the second reference line specifically comprises:
and respectively acquiring boundary points on two opposite boundaries in the first direction of the visual field from the X-ray signals at the first reference line and the second reference line after denoising.
Optionally, the calculating the centering error of the beam limiter and the detector according to the linear equation of each boundary of the view field in the coordinate system of the detector specifically includes:
and calculating the misalignment angle of the beam limiter and the detector according to the slope corresponding to the linear equation of each boundary of the visual field in the detector coordinate system.
A device for measuring a centering error of a vascular machine system, the vascular machine system comprising a beam limiter and a detector, the device comprising:
the adjusting unit is used for adjusting the size of the view field of the beam limiter so that the view field of the beam limiter is in the detector;
the generating unit is used for shooting the X-ray film according to the field of view of the adjusted beam limiter so as to generate an X-ray image on the detector;
The acquisition unit is used for acquiring a linear equation of each boundary of the visual field in a detector coordinate system according to the X-ray image;
and the calculating unit is used for calculating the centering error of the beam limiter and the detector according to the linear equation of each boundary of the visual field in the detector coordinate system.
Optionally, the outline of the field of view is rectangular, and the acquiring unit specifically includes:
the first direction linear equation obtaining subunit is used for respectively obtaining linear equations of two opposite boundaries in the first direction of the visual field in a detector coordinate system according to the X-ray image;
the second direction linear equation obtaining subunit is used for respectively obtaining linear equations of two opposite boundaries in the second direction of the visual field in a detector coordinate system according to the X-ray image;
wherein the first direction is perpendicular to the second direction.
Optionally, the first direction linear equation obtaining subunit specifically includes:
an X-ray signal acquisition module for acquiring X-ray signals at a first reference line and a second reference line of the X-ray image; the first reference line and the second reference line are intersected with two boundaries opposite to each other in the first direction of the visual field, and the intersection point of the two boundaries opposite to each other in the first direction of the visual field are different from each other;
The boundary point acquisition module is used for acquiring boundary points positioned on two opposite boundaries in the first direction of the visual field according to the X-ray signals at the first reference line and the second reference line;
and the linear equation acquisition module is used for acquiring the linear equation of each boundary in the first direction of the visual field in the detector coordinate system according to the boundary points positioned on each two boundaries in the first direction of the visual field.
Compared with the prior art, the application has the following beneficial effects:
based on the above technical solution, according to the method for measuring the centering error of the vascular machine system provided by the present application, the centering error of the beam limiter and the detector can be calculated according to the linear equation of each boundary of the field of view in the detector coordinate system; the linear equation can be obtained from the X-ray image, which can be obtained by the view of the beam limiter. Therefore, all the processes of the measuring method are completely carried out by a machine without manual participation, and the full-automatic measurement of the centering error can be realized by the measuring method provided by the application. The measuring method has the characteristics of real time, rapidness and accuracy.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic view of the effects of a gantry of a vascular machine provided by the present application;
FIG. 2 is a schematic diagram showing the effect of beam limiter and detector alignment provided in the present application;
FIG. 3 is a schematic view of a beam limiter and detector according to the present application, with a misalignment at a gamma angle;
FIG. 4 is a flowchart of a method for measuring centering errors of a vascular machine system according to an embodiment of the present disclosure;
FIG. 5 is a schematic diagram illustrating a process for adjusting the size of a field of view of a beam limiter according to an embodiment of the present disclosure;
FIG. 6 is a schematic illustration of an X-ray image with accurate centering provided in accordance with one embodiment of the present application;
FIG. 7 is a schematic view of an X-ray image with angular misalignment according to an embodiment of the present application;
FIG. 8 is a schematic diagram of a coordinate system of a detector according to an embodiment of the present disclosure;
Fig. 9 is a schematic structural diagram of a first reference line and a second reference line according to a first embodiment of the present disclosure;
FIG. 10 is a schematic diagram of a structure for determining a view boundary at two positions according to an embodiment of the present application;
fig. 11 is a schematic diagram of a sequence signal of a first reference line, a denoised sequence signal, and a differential result thereof according to an embodiment of the present application;
FIG. 12 is a schematic view of a plurality of position determining view boundaries according to an embodiment of the present application;
fig. 13 is a schematic structural diagram of a control device for performing a method for measuring a centering error of an vascular machine system according to an embodiment of the present application;
fig. 14 is a schematic structural diagram of a device for measuring centering errors of an vascular machine system according to an embodiment of the present application.
Detailed Description
Before introducing the embodiments of the present application, the technical terms used to describe the embodiments of the present application are first introduced.
First the concept of centering is introduced.
Referring to fig. 2, the alignment effect of the beam limiter and the detector provided by the application is schematically shown.
In fig. 2, the origin of the X-ray plane of the beam limiter is O, and the coordinate system is X, y and z in sequence; the origin of the detector plane is the detector center O', and the coordinate systems are u and v in sequence.
Centering means that the X-rays emitted from the focal spot F through the O-point should coincide with O', and that X is parallel to u and y is parallel to v.
The concept of misalignment is described below.
Referring to fig. 3, the diagram is a schematic diagram of the effect of misalignment of the beam limiter and the detector at a gamma angle.
The detector plane 31 is shown in fig. 3 as a solid rectangle, while the beam limiter FOV32 is shown as a dashed rectangle, with the solid rectangle being angularly displaced from the dashed rectangle by a angle y
The gamma misalignment means that the beam limiter FOV32 is not centered with the detector plane 31 and is offset by gamma.
In order to solve the technical problems in the background art, embodiments of the present application provide a method for measuring a centering error of a vascular machine system, where the vascular machine system includes a beam limiter and a detector, the method includes: adjusting the size of the view field of the beam limiter so that the view field of the beam limiter is in the detector; shooting an X-ray film according to the adjusted view of the beam limiter so as to generate an X-ray image on the detector; acquiring a linear equation of each boundary of the visual field in a detector coordinate system according to the X-ray image; and calculating the centering error of the beam limiter and the detector according to the linear equation of each boundary of the visual field in the detector coordinate system.
According to the method for measuring the centering error of the vascular machine system, the centering error of the beam limiter and the detector can be calculated according to the linear equation of each boundary of the visual field in the detector coordinate system; the linear equation can be obtained from the X-ray image, which can be obtained by the view of the beam limiter. Therefore, all the processes of the measuring method can be completely executed by a machine without manual participation, and the full-automatic measurement of the centering error can be realized by the measuring method provided by the application. The measuring method has the characteristics of real time, rapidness and accuracy.
In order to make the present application solution better understood by those skilled in the art, the following description will clearly and completely describe the technical solution in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
Example 1
Referring to fig. 4, a flowchart of a method for measuring centering errors of a vascular machine system according to an embodiment of the present application is shown.
It should be noted that, a schematic structural diagram of the vascular machine system according to the embodiment of the present application is shown in fig. 1. Thus, the vascular machine system comprises a beam limiter and a detector.
The method for measuring the centering error of the vascular machine system provided by the embodiment of the application comprises the following steps:
s401: adjusting the size of the view field of the beam limiter so that the view field of the beam limiter is in the detector;
s402: shooting an X-ray film according to the adjusted view of the beam limiter so as to generate an X-ray image on the detector;
s403: acquiring a linear equation of each boundary of the visual field in a detector coordinate system according to the X-ray image;
S404: and calculating the centering error of the beam limiter and the detector according to the linear equation of each boundary of the visual field in the detector coordinate system.
In order to more clearly and fully describe each step in the method, a specific implementation manner of each step of the method is described below.
A specific implementation of S401 will be first described.
In S401, since the field of view of the beam limiter is adjustable, the FOV of the beam limiter can be ensured to fall entirely within the detector by adjusting the field of view of the beam limiter.
Because the angle of the FOV of the beam limiter and the detector is smaller, the FOV range of the beam limiter can be completely fallen into the detector as long as the size of the field of view of the beam limiter is smaller than the size of the detector. For example, the size of the FOV may be adjusted to half the detector size. If the detector size is 40 x 30cm, then the FOV size is adjusted to 20 x 15cm.
Referring to fig. 5, a schematic diagram of a process for adjusting a view size of a beam limiter according to an embodiment of the present application is shown.
In fig. 5, the dashed rectangle represents the field of view of the beam limiter, and the solid rectangle represents the planar extent of the detector. Wherein fig. 5 (1) shows the case where the initial beam limiter field of view falls within the detector, and fig. 5 (2) shows the case where the adjusted beam limiter field of view falls within the detector.
As an example, the initial beam limiter field of view in fig. 5 (1) does not all fall within the detector, and a part of the field of view exceeds the plane range of the detector, so as to ensure that the field of view of the beam limiter falls within the detector range, S401 may be specifically: the field of view of the beam limiter is reduced in size so that the field of view of the beam limiter falls entirely within the detector, as shown in fig. 5 (2).
A specific implementation of S402 is described below.
In S402, after the X-rays emitted from the bulb pass through the beam limiter, the detector receives the X-rays within the FOV of the beam limiter after the adjustment, thereby generating an X-ray image. For ease of explanation and understanding, the FOV profile of the beam limiter will be described below as rectangular.
Referring to fig. 6, a schematic diagram of an X-ray image with accurate centering is provided in accordance with an embodiment of the present application.
Referring to fig. 7, a schematic diagram of an X-ray image with gamma misalignment is provided in an embodiment of the present application.
As an example, when the detector is 40X 30cm and the adjusted beam limiter FOV is 20X 15cm, the X-ray image generated by S402 is as follows:
if the beam limiter is centered exactly with the detector, the X-ray image of fig. 6 generated by S402 includes an in-FOV area 601 and an out-FOV area 602, wherein the in-FOV area 601 is a rectangle 20X 15cm at the center of the detector, and the in-FOV area 601 is composed of the X-ray signal, and thus, the signal value is higher, represented by white in fig. 6; however, since the region 602 outside the FOV has no ray signal, the signal value is low, represented in gray in fig. 6.
If the beam limiter is not centered at the gamma angle with the detector, S402 will generate an X-ray image as shown in fig. 7, which image comprises an in-FOV area 701 and an area 702 outside the FOV, wherein the in-FOV area 701 is a rectangle of 20X 15cm with the detector being not centered at the gamma angle, and the in-FOV area 701 is made up of the X-ray signal, thus the signal value is higher, indicated by white in fig. 7; however, since the region 702 outside the FOV has no ray signal, the signal value is low, which is indicated in gray in fig. 7.
A specific implementation of S403 is described below.
In S403, the FOV outline may be rectangular, square, or other shapes. And S403 includes at least the following specific embodiments:
when the FOV profile is rectangular, S403 may specifically include:
s403a: respectively acquiring linear equations of two opposite boundaries in the first direction of the visual field in a detector coordinate system according to the X-ray image;
s403b: respectively acquiring linear equations of two opposite boundaries in a second direction of the visual field in a detector coordinate system according to the X-ray image; wherein the first direction is perpendicular to the second direction.
As an example, the first direction may be the direction in which the lateral boundary of the FOV is located, and the second direction may be the direction in which the vertical boundary of the FOV is located; as another example, the first direction may be the direction in which the vertical boundary of the FOV is located, and the second direction may be the direction in which the lateral boundary of the FOV is located.
The following description will take an example in which the first direction is the vertical direction of the FOV and the second direction is the lateral direction of the FOV.
Referring to fig. 8, a schematic diagram of a detector coordinate system according to an embodiment of the present application is shown.
In fig. 8, the origin of the detector coordinate system is O', the coordinate axes are u and v, respectively, and the FOV range is a rectangle with P1, P2, P3, and P4 as vertices. Wherein, two opposite boundaries in the vertical direction of the FOV are a P1P2 side and a P4P3 side, and two opposite boundaries in the transverse direction of the FOV are a P3P2 side and a P4P1 side. Thus, the straight line equation on the P1P2 side and the straight line equation on the P4P3 side can be obtained by S403a, and the straight line equation on the P3P2 side and the straight line equation on the P4P1 side can be obtained by S403 b.
Since the method of acquiring the straight line equations of the two opposite boundaries in the vertical direction of the FOV is the same as the method of acquiring the straight line equations of the two opposite boundaries in the horizontal direction of the FOV, the straight line equations of the two opposite boundaries in the vertical direction of the FOV will be described as an example.
For fast and accurate acquisition of the straight line equation of the FOV boundary, the embodiment of the present application provides two specific implementations of S403a, which will be described below.
First embodiment of S403a
S403a may specifically be:
s403a-1: acquiring X-ray signals of each sampling point on a first reference line and a second reference line of an X-ray image; the first reference line and the second reference line are intersected with two opposite boundaries in the vertical direction of the visual field, and the intersection point of the first reference line and the two opposite boundaries in the vertical direction of the visual field is different from the intersection point of the second reference line and the two opposite boundaries in the vertical direction of the visual field;
The first reference line may be a position where any line intersecting the P1P2 side and the P4P3 side of the FOV is located, and the second reference line may be a position where any line intersecting the P1P2 side and the P4P3 side of the FOV is located.
Referring to fig. 9, a schematic structural diagram of a first reference line and a second reference line according to an embodiment of the present application is shown.
The two straight lines l1 and l2 in each of fig. 9 represent the first reference line and the second reference line, respectively.
Since the intersection point of the first reference line intersecting the P1P2 side and the P4P3 side of the FOV and the intersection point of the second reference line intersecting the P1P2 side and the P4P3 side of the FOV are different, the first reference line may be parallel to the second reference line, as shown in fig. 9 (1), in which case the second reference line may be obtained by moving the first reference line by a certain distance; the first reference line may also intersect the second reference line as shown in fig. 9 (2); the first reference line may also be neither parallel nor intersecting with the second reference line, as shown in fig. 9 (3). In short, the straight line of the first reference line and the straight line of the second reference line cannot pass through two identical points.
S403a-2: acquiring boundary points on two opposite boundaries in the vertical direction of the visual field according to X-ray signals of sampling points on the first reference line and the second reference line;
Since the X-ray image may be represented by a matrix I, wherein the elements in matrix I of N X M represent N X M pixels of the X-ray image, for example, the matrix of the X-ray image is represented by formula (1) as follows,
wherein, the element p of the Nth row and the Mth column in the I matrix NM Representing the pixel values of the nth row and mth column in the X-ray image.
The X-ray signals at the first reference line and the second reference line are both sequence signals. For convenience of explanation and explanation, the explanation will be given by taking fig. 10 as an example.
Referring to fig. 10, a schematic structural diagram of determining a view boundary at two positions according to an embodiment of the present application is shown.
In fig. 10, the first reference line 1001 is located at the middle position of the image, and the sequence signal L1 of the first reference line 1001 is expressed as follows by equation (2),
the sequence signal L1 of the first reference line 1001 in the formula (2) is all pixel values of the N/2 th row of the image matrix I, and thus, M pixels are included in L1. In fig. 10, the intersection point of the first reference line 1001 and the P1P2 side is vr1 and the intersection point of the first reference line 1001 and the P4P3 side is vl1.
The second reference line 1002 is obtained by shifting the first reference line 1001 downward by 2 pixels, and thus, the sequence signal L2 of the second reference line 1002 is expressed as follows by formula (3):
the sequence signal L2 of the second reference line 1002 in the formula (3) is all pixel values of the (N/2) +2 th row of the image matrix I, and thus, M pixels are included in L2. In fig. 10, the intersection point of the second reference line 1002 and the P1P2 side is vr2 and the intersection point of the second reference line 1002 and the P4P3 side is vl2.
For fast and accurate acquisition of the straight line equation of the FOV boundary, S403a-2 may be specifically:
differentiating the front and rear terms of the X-ray signals at the first reference line and the second reference line to obtain differential signal distribution diagrams at the first reference line and the second reference line; each differential signal distribution diagram comprises extreme points, and the extreme points in each differential signal distribution diagram are boundary points on each boundary in the vertical direction of the visual field.
It should be noted that, assuming that the X-ray signal is S (i) and i e {1,2, …, n } is expressed, the difference between the front and rear terms of the X-ray signal means that the front term is subtracted from the rear term in the signal sequence, and the calculation formula (4) is as follows:
ΔS(i)＝S(i+1)-S(i),i∈{1,2,...,(n-1)} (4)
where Δs (i), and i e {1,2,., (n-1) } is a differential result.
The differential signal distribution map is a map drawn from the differential result of the X-ray signals.
In addition, because of the scattering and refraction of X-rays, the focus is not an ideal point light source, and some X-ray signals are also arranged outside the FOV, but the quantity is smaller. The L1 signal is therefore not an ideal staircase signal and there is some glitch noise.
Thus, in order to solve the above-mentioned problem, after acquiring X-ray signals at a first reference line and a second reference line of an X-ray image, before acquiring boundary points located on two boundaries opposite in a vertical direction of a field of view from the X-ray signals at the first reference line and the second reference line, the embodiment of the present application further includes:
Denoising X-ray signals at a first reference line and a second reference line of an X-ray image;
the denoising method is various, for example, the method is that, assuming that the original signal is S (i) and i=1 to n, the calculation formula (5) of the denoised signal is as follows:
wherein X (j), and j E {1,2, …, n } is the denoised signal; and m can be taken as required, and the larger m is, the smoother the denoised signal is.
Since the method of obtaining the intersection vr1 of the first reference line and the P1P2 side and the intersection vl1 of the first reference line and the P4P3 side is the same as the method of obtaining the intersection vr2 of the second reference line and the P1P2 side and the intersection vl2 of the second reference line and the P4P3 side, a method of obtaining the intersection vr1 of the first reference line and the P1P2 side and the intersection vl1 of the first reference line and the P4P3 side will be described below as an example.
Referring to fig. 11, the sequence signal of the first reference line, the denoised sequence signal and the differential result thereof provided in the first embodiment of the present application are schematic diagrams.
Fig. 11 (1) is a sequence signal distribution diagram of a first reference line, the vertical axis is a pixel signal value, and the horizontal axis is a pixel point; FIG. 11 (2) is a plot of the signal of the first reference line sequence after denoising; fig. 11 (3) is a front-rear differential signal distribution diagram of the sequence signal of the first reference line.
Because the first reference line penetrates through the X-ray image, the first reference line sequentially passes through the X-ray free area, the X-ray free area and the X-ray free area, the signal of the X-ray free area is low, and the signal of the X-ray free area is high, the sequence signal of the first reference line jumps at the junction of the X-ray free area and the X-ray free area. Further, since there are two intersections between the X-ray-free region and the X-ray region, there are two positions of signal jumps in fig. 11 (1), and the positions of the two intersections are vr1 and vl1, respectively.
First, in order to reduce the influence of noise on the sequence signal of the first reference line, the first sequence is subjected to denoising processing of n=2, that is, a calculation formula (6) for the denoised sequence signal of the first reference line is expressed as follows:
next, in order to obtain the positions vr1 and vl1, the difference between the front and rear of the sequence signal of the first reference line after denoising is performed, and the definition of the difference can be obtained according to the front and rear terms of the X-ray signal:
the calculation formula (7) of the differential result at the first reference line is expressed as follows:
ΔL1'(i)＝L1'(i+1)-L1'(i),i∈{1,2,...,(M-1)} (7)
then, the differential result of the sequence signal of the first reference line is represented by a front-to-rear differential signal distribution map of the sequence signal of the first reference line, as shown in fig. 11 (2), which includes two extreme points: maximum point and minimum point. In this figure, the maximum point is located at the point vl1, and the minimum point is located at the point vr1, so that the points vr1 and vl1 can be determined according to the positions of the maximum point and the minimum point.
The above embodiments describe the process of directly mapping differential signal according to differential results, and another embodiment is provided in the present application. In this embodiment, after the differential result is obtained, the differential result is taken as an absolute value, and then a differential signal absolute value distribution diagram is drawn, where the differential signal absolute value distribution diagram includes two maximum points: a first maximum point and a second maximum point. Wherein the first maximum point in the figure is located at point vl1 and the second maximum point is located at point vr1, whereby the points vr1 and vl1 can be determined from the positions of the first and second maximum points.
S403a-3: and acquiring a linear equation of each boundary in the vertical direction of the visual field in the detector coordinate system according to boundary points on each two boundaries in the vertical direction of the visual field.
Since two points can determine one straight line, the straight line equation on the side of P1P2 can be obtained by using the point vr1 and the point vr2 obtained in S403a-2, and the straight line equation on the side of P4P3 can be obtained by using the point vl1 and the point vl 2.
In addition, in order to further improve the accuracy of the measurement result, the second reference line may be a plurality of positions in the X-ray image, and then, a linear equation of each boundary in the vertical direction of the field of view in the detector coordinate system is fitted according to the boundary points located on each two boundaries in the vertical direction of the field of view and the least square method, respectively.
The least square method is to fit a straight line from a plurality of points such that the sum of squares of distances of the points to the fitted straight line is minimized.
Referring to fig. 12, a schematic diagram of a structure of determining a view boundary at a plurality of positions according to an embodiment of the present application is shown.
Four locations are shown in FIG. 12, the first reference line intersecting the P1P2 edge at vr1 and the first reference line intersecting the P4P3 edge at vl1; the second reference line intersects the P1P2 edge at vr2 and the second reference line intersects the P4P3 edge at vl2; the third position intersects the P1P2 edge at vr3 and the third position intersects the P4P3 edge at vl3; the fourth location intersects the P1P2 edge at vr4 and the fourth location intersects the P4P3 edge at vl4.
The points vr1, vl1, vr2, vl2, vr3, vl3, vr4, and vl4 are obtained using S403a-2, and then the P1P2 side and the P4P3 side are obtained using S403a-3 based on the least square method.
The first embodiment of S403a is described above by obtaining the first reference line and the second reference line at the same time, and obtaining two boundaries in the vertical direction of the visual field using the first reference line and the second reference line. In order to improve accuracy of centering error measurement and simplify operation, the embodiment of the present application further provides another implementation mode of S403 a.
Second embodiment of S403a
According to the embodiment, boundary points on two opposite boundaries in the vertical direction of the visual field are obtained according to X-ray signals of a first reference line, the first reference line is translated to obtain a second reference line, then the boundary points on the two opposite boundaries in the vertical direction of the visual field are obtained according to X-ray signals of the second reference line, and finally the intersection point on the boundary obtains a linear equation of each boundary in the vertical direction of the visual field in a detector coordinate system.
As one example, the first reference line translates upward to obtain the second reference line, and as another example, the first reference line translates downward to obtain the second reference line.
The first reference line is translated upward to obtain the second reference line, which will be described below as an example.
S403a may specifically be:
s403a-a: acquiring an X-ray signal of a first reference line of an X-ray image; the first reference line intersects two boundaries opposite to each other in the vertical direction of the visual field;
the content of S403a-a related to the "first reference line" in S403a-1 is the same, and will not be described here again.
S403a-b: acquiring boundary points on two opposite boundaries in the vertical direction of the visual field according to the X-ray signals of the first reference line;
s403a-b are the same as those related to the "first reference line" in S403a-2, and will not be described here again.
S403a-c: translating the first reference line upwards by a certain distance to acquire an X-ray signal of a second reference line of the X-ray image; the second reference line intersects two boundaries opposite in the vertical direction of the field of view.
As an example, when the sequence signal L1 of the first reference line is expressed as follows by formula (2),
s403a-c may be specifically: the first reference line is shifted up by 4 pixels, a second reference line is obtained, and a serial number signal L2 of the second reference line is expressed as follows by formula (3):
s403a-d: acquiring boundary points on two opposite boundaries in the vertical direction of the visual field according to the X-ray signals of the second reference line;
the content of S403a-d related to the "second reference line" in S403a-2 is the same, and will not be described here again.
S403a-e: and acquiring a linear equation of each boundary in the vertical direction of the visual field in the detector coordinate system according to boundary points on each two boundaries in the vertical direction of the visual field.
S403a-e are the same as S403a-3, and are not described here.
In addition, in order to further improve the accuracy of the measurement result, in the embodiment of the present application, after S403a-d, before S403a-e, a plurality of positions such as a third position and a fourth position may be sequentially obtained by translating the first reference line multiple times, and then, a linear equation of each boundary in the vertical direction of the field of view in the coordinate system of the detector may be fitted according to the boundary points located on each two boundaries in the vertical direction of the field of view and the least square method, respectively.
The specific implementation of S404 is described below.
In S404, to further improve the accuracy of the measurement result, the specific implementation manner of this step may be: and calculating the misalignment angle of the beam limiter and the detector according to the slope corresponding to the linear equation of each boundary of the visual field in the detector coordinate system.
The process may be specifically:
first, with the view boundary located furthest from the origin of the detector coordinate system as the starting point, the slopes corresponding to the linear equations of the boundaries of the view are a1, a2, a3, and a4, respectively, along the counterclockwise direction, and then the linear equations of the P1P2 side, the P4P3 side, the P3P2 side, and the P4P1 side are:
the linear equation of P1P2 is v=a1×u+b1;
the linear equation of P3P2 is v=a2×u+b2;
the linear equation of P4P3 is v=a3×u+b3;
the linear equation of P4P1 is v=a4×u+b4.
Then, calculating the misalignment angle of the beam limiter and the detector according to the slope corresponding to the linear equation of each boundary in the detector coordinate system and the following formula:
wherein, gamma is the misalignment angle of the beam limiter and the detector.
According to the method for measuring the centering error of the vascular machine system, the centering error of the beam limiter and the detector can be calculated according to the linear equation of each boundary of the visual field in the detector coordinate system; the linear equation can be obtained from the X-ray image, which can be obtained by the view of the beam limiter. Therefore, all processes of the measuring method can be completely executed by a machine, and therefore, the measuring method provided by the application can realize full-automatic measurement of centering errors. The measuring method has the characteristics of real time, rapidness and accuracy.
The method of measuring the centering error of the vascular machine system of the above-described embodiment may be performed by the control apparatus shown in fig. 13. The control device shown in fig. 13 includes a processor 1310, a communication interface (Communications Interface) 1320, a memory 1330, and a bus 1340. Processor 1310, communication interface 1320, and memory 1330 communicate with each other via bus 1340.
The memory 1330 may store therein logic instructions for measuring a centering error of the vascular system, and may be, for example, a nonvolatile memory (non-volatile memory). The processor 1310 may invoke logic instructions to perform the measurement of the centering error of the vascular machine system in the memory 1330 to perform the method of measuring the centering error of the vascular machine system described above. As an embodiment, the logic instruction for measuring the centering error of the vascular machine system may be a program corresponding to the control software, and when the processor executes the instruction, the control device may correspondingly display a functional interface corresponding to the instruction on the display interface.
The functions of the logic instructions for the measurement of centering errors of the vascular machine system, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present disclosure may be embodied in essence or a part contributing to the prior art or a part of the technical solution, or in the form of a software product stored in a storage medium, including several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods of the embodiments of the present disclosure. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
The logic instruction for measuring the centering error of the vascular machine system may be referred to as "a device for measuring the centering error of the vascular machine system", and the device may be divided into functional modules. See in particular example two.
Example two
Referring to fig. 14, the structure of a device for measuring the centering error of the vascular machine system according to the second embodiment of the present application is shown.
The embodiment of the application provides a device for measuring centering error of a vascular machine system, which comprises:
an adjusting unit 1401, configured to adjust a size of a field of view of the beam limiter, so that the fields of view of the beam limiter are all within the detector;
a generating unit 1402 for photographing the X-ray film according to the adjusted view of the beam limiter to generate an X-ray image on the detector;
an acquisition unit 1403 for acquiring a linear equation of each boundary of the field of view in a detector coordinate system from the X-ray image;
a calculating unit 1304, configured to calculate a centering error of the beam limiter and the detector according to a linear equation of each boundary of the field of view in the detector coordinate system.
Optionally, the outline of the field of view is rectangular, and the acquiring unit 1403 specifically includes:
the first direction linear equation obtaining subunit is used for respectively obtaining linear equations of two opposite boundaries in the first direction of the visual field in a detector coordinate system according to the X-ray image;
The second direction linear equation obtaining subunit is used for respectively obtaining linear equations of two opposite boundaries in the second direction of the visual field in a detector coordinate system according to the X-ray image;
wherein the first direction is perpendicular to the second direction.
Optionally, the first direction linear equation obtaining subunit specifically includes:
an X-ray signal acquisition module for acquiring X-ray signals at a first reference line and a second reference line of the X-ray image; the first reference line and the second reference line are intersected with two boundaries opposite to each other in the first direction of the visual field, and the intersection point of the two boundaries opposite to each other in the first direction of the visual field are different from each other;
the boundary point acquisition module is used for acquiring boundary points positioned on two opposite boundaries in the first direction of the visual field according to the X-ray signals at the first reference line and the second reference line;
and the linear equation acquisition module is used for acquiring the linear equation of each boundary in the first direction of the visual field in the detector coordinate system according to the boundary points positioned on each two boundaries in the first direction of the visual field.
Optionally, the X-ray signals at the first reference line and the second reference line are both sequence signals;
the boundary point acquisition module is specifically configured to:
differentiating the front and rear terms of the X-ray signals at the first reference line and the second reference line to obtain differential signal distribution diagrams at the first reference line and the second reference line; each differential signal distribution diagram comprises extreme points, and the extreme points in each differential signal distribution diagram are boundary points on each boundary in the first direction of the visual field.
Optionally, the second reference line in the device for measuring the centering error of the vascular machine system is a plurality of positions in the X-ray image.
Optionally, the device for measuring the centering error of the vascular machine system further includes:
the denoising unit is used for denoising X-ray signals at a first reference line and a second reference line of the X-ray image;
the boundary point acquisition module is specifically configured to:
and respectively acquiring boundary points on two opposite boundaries in the first direction of the visual field from the X-ray signals at the first reference line and the second reference line after denoising.
Optionally, the calculating unit 1404 specifically includes:
And the angle calculating subunit is used for calculating the misalignment angle of the beam limiter and the detector according to the slope corresponding to the linear equation of each boundary of the visual field in the detector coordinate system.
Optionally, taking a view field boundary located furthest from the origin of the detector coordinate system as a starting point, and along the anticlockwise direction, the slopes corresponding to the linear equations of the boundaries of the view field are a1, a2, a3 and a4 respectively;
the angle calculation subunit is specifically configured to:
the misalignment angle of the beam limiter and the detector is calculated according to the following formula:
wherein, gamma is the misalignment angle of the beam limiter and the detector.
The device for measuring the centering error of the vascular machine system provided by the embodiment of the application can calculate the centering error of the beam limiter and the detector according to the linear equation of each boundary of the visual field in the detector coordinate system; the linear equation can be obtained from the X-ray image, which can be obtained by the view of the beam limiter. Therefore, the measuring device provided by the application can realize full-automatic measurement of centering errors. The measuring device has the characteristics of real time, rapidness and accuracy.
The foregoing is an introduction to the apparatus for measuring a centering error of a vascular machine system provided in the embodiments of the present application, and a specific implementation manner may refer to the description in the method embodiment shown above, so that the achieved effect is consistent with the method embodiment described above, and will not be described herein again.
The foregoing is merely a preferred embodiment of the present application and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present application and are intended to be within the scope of the present application.
Claims (9)
1. A method of measuring a centering error of a vascular machine system, the vascular machine system including a beam limiter and a detector, the method comprising:
adjusting the size of the field of view of the beam limiter so that the field of view of the beam limiter is in the detector;
shooting an X-ray film according to the adjusted view of the beam limiter so as to generate an X-ray image on the detector;
acquiring a linear equation of each boundary of the visual field in a detector coordinate system according to the X-ray image;
calculating the centering error of the beam limiter and the detector according to a linear equation of each boundary of the visual field in a detector coordinate system;
the method for calculating the centering error of the beam limiter and the detector according to the linear equation of each boundary of the visual field in the detector coordinate system specifically comprises the following steps:
and calculating the misalignment angle of the beam limiter and the detector according to the slope corresponding to the linear equation of each boundary of the visual field in the detector coordinate system.
2. The method according to claim 1, wherein the outline of the field of view is rectangular, and the acquiring the linear equation of each boundary of the field of view in the detector coordinate system according to the X-ray image specifically includes:
respectively acquiring linear equations of two opposite boundaries in the first direction of the visual field in a detector coordinate system according to the X-ray images;
respectively acquiring linear equations of two opposite boundaries in a second direction of the visual field in a detector coordinate system according to the X-ray images;
wherein the first direction is perpendicular to the second direction.
3. The method according to claim 2, wherein the acquiring, from the X-ray image, the linear equations of the two boundaries opposite in the first direction of the field of view in the detector coordinate system, respectively, specifically includes:
acquiring X-ray signals at a first reference line and a second reference line of the X-ray image; the first reference line and the second reference line are intersected with two boundaries opposite to each other in the first direction of the visual field, and the intersection point of the two boundaries opposite to each other in the first direction of the visual field are different from each other;
Acquiring boundary points on two opposite boundaries in the first direction of the visual field according to X-ray signals at the first reference line and the second reference line;
and acquiring a linear equation of each boundary in the first direction of the visual field in a detector coordinate system according to the boundary points on each two boundaries in the first direction of the visual field.
4. A method according to claim 3, wherein the X-ray signals at the first and second reference lines are each a sequence signal;
the acquiring boundary points on two opposite boundaries in the first direction of the visual field according to the X-ray signals at the first reference line and the second reference line specifically comprises:
differentiating the front and rear terms of the X-ray signals at the first reference line and the second reference line to obtain differential signal distribution diagrams at the first reference line and the second reference line; each differential signal distribution diagram comprises extreme points, and the extreme points in each differential signal distribution diagram are boundary points on each boundary in the first direction of the visual field.
5. The method of claim 3 or 4, wherein the second reference line is a plurality of locations in the X-ray image.
6. The method of claim 4, wherein after the acquiring X-ray signals at the first reference line and the second reference line of the X-ray image, the acquiring boundary points located on two boundaries opposite in the first direction of the field of view from the X-ray signals at the first reference line and the second reference line is preceded by:
denoising X-ray signals at a first reference line and a second reference line of the X-ray image;
the acquiring boundary points on two opposite boundaries in the first direction of the visual field according to the X-ray signals at the first reference line and the second reference line specifically comprises:
and respectively acquiring boundary points on two opposite boundaries in the first direction of the visual field from the X-ray signals at the first reference line and the second reference line after denoising.
7. A device for measuring a centering error of a vascular machine system, the vascular machine system comprising a beam limiter and a detector, the device comprising:
the adjusting unit is used for adjusting the size of the view field of the beam limiter so that the view field of the beam limiter is in the detector;
the generating unit is used for shooting the X-ray film according to the field of view of the adjusted beam limiter so as to generate an X-ray image on the detector;
The acquisition unit is used for acquiring a linear equation of each boundary of the visual field in a detector coordinate system according to the X-ray image;
the calculating unit is used for calculating the centering error of the beam limiter and the detector according to a linear equation of each boundary of the visual field in the detector coordinate system;
the computing unit specifically comprises:
and the angle calculating subunit is used for calculating the misalignment angle of the beam limiter and the detector according to the slope corresponding to the linear equation of each boundary of the visual field in the detector coordinate system.
8. The apparatus according to claim 7, wherein the outline of the field of view is rectangular, and the acquisition unit specifically comprises:
the first direction linear equation obtaining subunit is used for respectively obtaining linear equations of two opposite boundaries in the first direction of the visual field in a detector coordinate system according to the X-ray image;
the second direction linear equation obtaining subunit is used for respectively obtaining linear equations of two opposite boundaries in the second direction of the visual field in a detector coordinate system according to the X-ray image;
wherein the first direction is perpendicular to the second direction.
9. The apparatus of claim 8, wherein the first direction linear equation acquisition subunit specifically comprises:
An X-ray signal acquisition module for acquiring X-ray signals at a first reference line and a second reference line of the X-ray image; the first reference line and the second reference line are intersected with two boundaries opposite to each other in the first direction of the visual field, and the intersection point of the two boundaries opposite to each other in the first direction of the visual field are different from each other;
the boundary point acquisition module is used for acquiring boundary points positioned on two opposite boundaries in the first direction of the visual field according to the X-ray signals at the first reference line and the second reference line;
and the linear equation acquisition module is used for acquiring the linear equation of each boundary in the first direction of the visual field in the detector coordinate system according to the boundary points positioned on each two boundaries in the first direction of the visual field.
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