A DSA low-dose imaging method based on an adaptive collimation system

Abstract

The application discloses a DSA low-dose imaging method based on an adaptive collimation system and belongs to the technical field of X-ray machine imaging. The method comprises the following steps: (1) photography preparation, setting an adaptive collimator with adjustable collimation window area between an X-ray machine ball tube and a subject; (2) first photography, storing a generated mask image into an original image library; (3) if it is necessary to continue photography, executing step (4), otherwise, ending; (4) demarcating a region of interest (ROI) required by clinical diagnosis; (5) forming a hollowed-out collimation window matched with the region of interest (ROI) inside the adaptive collimator; (6) performing low-dose photography on the region of interest (ROI) only and returning to step (3). In the case that multiple photographies are required, only the region of interest (ROI) is irradiated in subsequent photographies, so that the imaging dose can be reduced; the region of interest (ROI) can be dynamically adjusted and optimized before each imaging, so that the imaging dose used in each photography can be as small as possible.

Description

TECHNICAL FIELD

[0001] The application relates to a DSA low-dose imaging method based on an adaptive collimation system and belongs to the technical field of X-ray machine imaging. BACKGROUND

[0002] Digital subtraction angiography (DSA) technology has become the first choice for imaging examination of various blood vessel diseases in the whole body and is the 'gold standard' for brain blood vessel and heart blood vessel imaging. DSA is also indispensable to interventional technology, especially intravascular interventional technology. With the increasingly wide application of DSA in the clinic, the requirements for DSA technology and equipment are also increasing, and new functions are constantly being introduced, such as three-dimensional DSA imaging function, higher frequency real-time imaging function and the like. However, these new technologies and functions often require higher imaging doses. How to reduce the imaging dose as much as possible while keeping the imaging function and imaging quality unaffected has become a problem to be solved.

[0003] Placing a collimator between the X-ray machine bulb and the subject is an effective dose control technology. X-rays in the collimation window area are projected to the subject through the collimation window, pass through the tissue and are collected and analyzed by the detector to obtain diagnostic information, and X-rays outside the collimation window are blocked by the collimator plate made of metal and will not be projected to the subject. By matching the size of the collimation window and the subject area, the imaging dose can be effectively reduced without affecting the imaging examination.

[0004] Unlike the common static collimation technology, the application proposes a DSA low-dose imaging method based on an adaptive collimation system, an adaptive collimator is placed between the X-ray machine bulb and the subject, and a self-adaptive collimation window is used to realize more accurate control of the imaging dose, thereby further greatly reducing the imaging dose. SUMMARY

[0005] The technical problem to be solved by the application is to provide a DSA low-dose imaging method based on an adaptive collimation system, which solves the problem that the imaging dose needs to be further reduced when the X-ray machine uses the static collimation technology.

[0006] The technical problem to be solved by the application is solved by the following technical scheme:

[0007] A DSA low-dose imaging method based on an adaptive collimation system, which comprises the following steps:

[0008] (1) photography preparation, an adaptive collimator with an adjustable collimation window area is arranged between the X-ray machine bulb and the subject, an original image library for storing original images is newly created, and a subtraction image library for storing subtraction images is created;

[0009] (2) Before injecting contrast agent, the collimating window of the adaptive collimator is in the maximum opening state, the first imaging is carried out, and the generated mask image is stored in the original image library;

[0010] (3) If the imaging needs to continue, step (4) is executed, otherwise, the process is ended;

[0011] (4) If the subtraction image has not been stored in the subtraction image library, the reference image is selected from the original image library, and the region of interest (ROI) required for clinical diagnosis is demarcated, otherwise, the reference image is selected from the subtraction image library, and the region of interest (ROI) required for clinical diagnosis is demarcated;

[0012] (5) According to the range of the region of interest (ROI), the position of each leaf of the adaptive collimator is adjusted to form a hollow collimating window matching the region of interest (ROI) inside the adaptive collimator;

[0013] (6) The X-ray machine transmits through the collimating window of the adaptive collimator to perform low-dose imaging on the region of interest (ROI) only, the image is stored in the original image library, and the corresponding subtraction image is generated, which is stored in the subtraction image library, and the process returns to step (3).

[0014] As a preferred example, the adaptive collimator comprises a plurality of metal leaves and a linear drive motor driving each metal leaf to independently translate, the plurality of metal leaves are closely arranged in two rows to form a split X-ray shielding plate, and each metal leaf is connected with a linear drive motor outside.

[0015] As a preferred example, the region of interest (ROI) is manually demarcated according to the region required for clinical diagnosis observed by the operator from the mask image or the subtraction image.

[0016] As a preferred example, the reference image is selected as the latest image stored in the original image library or the subtraction image library.

[0017] Before injecting contrast agent, the first imaging is required to obtain the mask, at this moment, the collimating window of the adaptive collimator is in the initial state of maximum opening, and the process is normal dose imaging.

[0018] After obtaining the mask, the region of interest (ROI) is first demarcated according to the clinical diagnosis, which is the main concerned region for subsequent imaging and diagnosis.

[0019] If multiple imaging is needed, the ROI can be adjusted according to the latest image before each imaging. For example, as more information is obtained from the subsequent images (especially the images with partial contrast agent), the ROI can be further reduced in size to further reduce the imaging dose, or the ROI can be gradually adjusted in size according to the flow and diffusion trend of the contrast agent in the blood vessels to avoid missing important diagnostic information. The ROI can be freely defined according to various clinical needs.

[0020] After the ROI is defined, the collimation window of the adaptive collimator is formed by two rows of metal leaves. The computer calculates the position of each metal leaf of the adaptive collimator, and according to the calculation result, the computer controls the linear drive motor to drive the metal leaf to the corresponding position to form a collimation window corresponding to the ROI.

[0021] After the adaptive collimator is adjusted, low-dose imaging is performed according to the frame rate required by the clinic until the imaging task is completed.

[0022] The image obtained by each imaging is stored in the original image library, and image processing and analysis including subtraction are performed to generate the corresponding subtraction image, which is stored in the subtraction image library. The image processing and analysis method used to generate the subtraction image is the existing common DSA image processing and analysis method, and there is no difference between the two. Here, it is not repeated. The difference between the images obtained by two adjacent imaging is only the flow of the injected contrast agent in the blood vessels, and the diagnostic difference is within the defined ROI, so the related image processing and analysis are only for the ROI region, reducing the data processing amount.

[0023] The beneficial effects of the present application are: an adaptive collimator is arranged between the X-ray machine ball tube and the subject, and the ROI is covered by the adjustable collimation window of the adaptive collimator. In the case of multiple imaging, only the ROI is irradiated in subsequent imaging, which can reduce the imaging dose. According to the image information obtained by each imaging, the ROI can be further dynamically adjusted and optimized so that the smallest possible imaging dose can be used for each imaging. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The flowchart of the main steps of the present application is shown in the figure;

[0025] Figure 2 The schematic diagram of the larger range of ROI is shown in the figure;

[0026] Figure 3 The schematic diagram of the collimation window adjustment corresponding to the larger range of ROI is shown in the figure;

[0027] Figure 4 schematic diagram of a small range of region of interest (ROI) ;

[0028] Figure 5 schematic diagram of collimation window adjustment corresponding to a small range of region of interest (ROI) ;

[0029] Figure 6 schematic diagram of projection distance L1, L2 of left and right edges of local region of interest (ROI) on X axis;

[0030] Figure 7 schematic diagram of distance of a pair of metal blade ends corresponding to L1, L2 to Z axis;

[0031] Figure 8 schematic diagram of distance between X-ray machine ball tube and metal blade and subject tissue. DETAILED DESCRIPTION

[0032] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific diagrams.

[0033] As shown in Figure 1 , a DSA low-dose imaging method based on an adaptive collimation system includes the following steps:

[0034] (1) photography preparation, setting an adaptive collimator with adjustable collimation window region between the X-ray machine ball tube and the subject tissue, creating a raw image library for storing raw images and a subtraction image library for storing subtraction images;

[0035] (2) before injecting contrast agent, the collimation window of the adaptive collimator is in the maximum opening state, and the first photography is performed, and the generated mask image is stored in the raw image library;

[0036] (3) if it is necessary to continue photography, step (4) is performed, otherwise, it is ended;

[0037] (4) if there is no subtraction image stored in the subtraction image library, a reference image is selected from the raw image library, and a region of interest (ROI) required for clinical diagnosis is delineated, otherwise, a reference image is selected from the subtraction image library, and a region of interest (ROI) required for clinical diagnosis is delineated; the region of interest (ROI) is manually delineated according to the region required for clinical diagnosis observed by the operator from the mask image or the subtraction image; the reference image selects the latest image stored in the raw image library or the subtraction image library;

[0038] (5) According to the range of the region of interest ROI, the position of each leaf of the adaptive collimator is adjusted to form a hollowed collimating window in the adaptive collimator that matches the region of interest ROI.

[0039] (6) The X-ray machine transmits through the collimating window of the adaptive collimator to perform low-dose photography only on the region of interest ROI, the image is stored in the original image library, and the corresponding silhouette image is generated and stored in the silhouette image library, and the process returns to step (3).

[0040] Embodiment

[0041] As shown in Figure 3 , Figure 5 , Figure 7 , the adaptive collimator includes a plurality of metal leaves (strip-shaped pieces in the figure) and linear drive motors (not shown in the figure) that drive each metal leaf to independently translate, the plurality of metal leaves are closely arranged in two rows to form a split X-ray shielding plate that completely corresponds to and covers the region of the subject tissue, and each metal leaf is connected to a linear drive motor on the outside. The linear drive motor completes the position adjustment of the metal leaf through the adaptive collimator driving algorithm of the computer. In the figure, the strip-shaped piece is a metal leaf, and the blank area is a collimating window.

[0042] Before the contrast agent is injected, a first photography is needed to obtain a mask, at this moment, the collimating window of the adaptive collimator is in the initial state of maximum opening, and this process is normal dose imaging.

[0043] After the mask is obtained, the region of interest ROI is first delineated according to the clinical diagnosis, which is the main area of interest for subsequent imaging and diagnosis.

[0044] As shown in Figures 2-5 , if multiple photography is needed, the region of interest ROI can be adjusted according to the latest image before each shooting. For example, as more information is obtained from subsequent images (especially some contrast agent images), the region of interest ROI can be further reduced in range to further reduce the imaging dose, or the ROI range can be gradually adjusted to be enlarged according to the flow and diffusion trend of the contrast agent in the blood vessels to avoid missing important diagnostic information. The region of interest ROI required by the clinic can be freely delineated according to various clinical needs.

[0045] After the region of interest ROI is delineated, the collimating window of the adaptive collimator is formed by the two rows of metal leaves together, and the position of each metal leaf of the adaptive collimator is calculated by the computer, according to the calculation result, the computer controls the linear drive motor to drive the metal leaf to the corresponding position to form a collimating window corresponding to the region of interest ROI.

[0046] As shown in Figures 6-8The adaptive collimator driving algorithm is shown as follows:

[0047] (1) Taking the middle split line of the two rows of metal blades as the Z axis and the moving direction of the metal blades as the X axis, a coordinate system is established with the Y axis passing through the intersection of the X axis and the Z axis;

[0048] (2) A pair of left and right symmetric metal blades are numbered as 1, 2, 3, …, n, … in sequence along the Z axis direction; n，1 (t) represents the distance from the end of the left metal blade in the nth pair of metal blades to the Z axis according to the ROI defined at the t time; n，2 (t) represents the distance from the end of the right metal blade in the nth pair of metal blades to the Z axis according to the ROI defined at the t time;

[0049] (3) In the local ROI covered by the nth pair of metal blades, L1 represents the projection distance of the left edge of the local ROI on the X axis, and L2 represents the projection distance of the right edge of the local ROI on the X axis;

[0050] (4) In the Y axis direction, the distance between the X-ray machine ball tube and the metal blade is h1, and the distance between the X-ray machine ball tube and the subject is h2;

[0051] (5) According to the principle of similar triangles (the top point of the triangle is the position of the X-ray machine ball tube), the following is calculated:

[0052] δ n，1 (t) = (h1 / h2)L1, δ n，2 (t) = (h1 / h2)L2

[0053] (6) According to the calculation results above, the linear drive motor moves each metal blade to the corresponding position to complete the collimation window adjustment.

[0054] After the adaptive collimator is adjusted, low-dose imaging is performed according to the frame frequency required by the clinic until the imaging task is completed.

[0055] The image obtained each time is stored in the original image library, and image processing and analysis including subtraction are performed to generate the corresponding subtraction image, which is stored in the subtraction image library. The image processing and analysis method used to generate the subtraction image is the existing common DSA image processing and analysis method, and there is no difference between the two. Here, it is not repeated. The difference between the images obtained by two adjacent imaging is only caused by the flowing of the injected contrast agent in the blood vessels, and the difference with diagnostic significance is within the defined ROI, so the relevant image processing and analysis is only for the ROI area, reducing the data processing amount.

[0056] The adaptive collimator is arranged between the X-ray machine ball tube and the examined tissue, the adjustable collimating window of the adaptive collimator covers the region of interest (ROI), in the case of multiple imaging, the subsequent imaging only irradiates the region of interest (ROI), which can reduce the imaging dose; according to the image information obtained by each imaging, the region of interest (ROI) can be further dynamically adjusted and optimized, so that the imaging dose used by each imaging is as small as possible.

[0057] Under the guidance of the prior information of the region of interest (ROI), the collimating system performs real-time adaptive conformal adjustment. Unlike the conventional fixed window collimator of the DSA and other imaging devices, the window of the adaptive collimating system can be dynamically adjusted and conformal to the shape of the region of interest (ROI). The X-ray imaging of the region within the corresponding conformal window is not affected, and meaningful diagnostic information is generated; the region outside the conformal window does not generate meaningful diagnostic information, and the X-ray is blocked by the metal leaf of the high-attenuation collimating system, so as to avoid the examined tissue from receiving additional radiation dose.

[0058] The basic principles, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited by the above-mentioned embodiments, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A DSA low-dose imaging method based on an adaptive collimation system, characterized in that, It includes the following steps: (1) Photographic preparation: Set up an adjustable adaptive collimator between the X-ray machine tube and the tissue under examination; create a new original image library for storing original images; and a silhouette image library for storing silhouette images. (2) Before injecting the contrast agent, the collimation window of the adaptive collimator is in the maximum opening state, and the first photograph is taken. The generated mask image is stored in the original image library. (3) If photography needs to continue, proceed to step (4); otherwise, end. (4) If the silhouette image library does not yet store a silhouette image, a reference image is selected from the original image library to delineate the region of interest (ROI) required for clinical diagnosis; otherwise, a reference image is selected from the silhouette image library to delineate the region of interest (ROI) required for clinical diagnosis. The reference image is the latest image stored in the original image library or the silhouette image library. The region of interest (ROI) is manually delineated based on the area required for clinical diagnosis observed by the operator from the masked image or the silhouette image. (5) Adjust the position of each blade of the adaptive collimator according to the range of the region of interest (ROI) to form a hollow collimation window inside the adaptive collimator that matches the ROI. (6) The X-ray machine takes low-dose images of only the region of interest (ROI) through the collimation window of the adaptive collimator. The images are stored in the original image library and corresponding silhouette images are generated. The silhouette images are stored in the silhouette image library. Based on the image information obtained from each imaging, the region of interest (ROI) is dynamically adjusted and optimized, and the process returns to step (3).

2. The DSA low-dose imaging method based on an adaptive collimation system according to claim 1, characterized in that, The adaptive collimator includes multiple metal blades and a linear drive motor that drives each metal blade to translate independently. The multiple metal blades are arranged closely in two columns to form a split X-ray shield, and a linear drive motor is connected to the outside of each metal blade.

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