KR102127711B1 - X-ray imaging apparatus and control method for the same - Google Patents

Abstract

Provided is an X-ray imaging apparatus capable of minimizing deterioration of image quality or FOV loss while reducing the dose of X-rays, and a control method thereof.
One aspect of the control method of the X-ray imaging apparatus irradiates X-rays having a dose less than the region of interest to an uninteresting region in the object region; And detecting the irradiated X-ray to obtain a frame image related to the object area.

Description

X-ray imaging device and its control method {X-RAY IMAGING APPARATUS AND CONTROL METHOD FOR THE SAME}

The disclosed subject matter relates to an X-ray imaging apparatus that irradiates an X-ray to an object and images the inside thereof, and a control method thereof.

The X-ray imaging apparatus is a device capable of irradiating X-rays to an object and obtaining an internal image of the object using X-rays transmitted through the object. Since the transmittance of X-rays is different according to the characteristics of the materials constituting the object, the intensity or intensity of the X-rays passing through the object may be detected to image the internal structure of the object. Meanwhile, in order to secure the stability of the X-ray imaging apparatus, it is recognized as an important problem to reduce the X-ray dose of the object.

Provided is an X-ray imaging apparatus and a control method that can reduce the dose of X-rays but minimize the deterioration of the quality of an X-ray image or field of view (FOV) loss.

An X-ray imaging apparatus according to an aspect includes an X-ray source irradiating X-rays to an object region; An X-ray detector that detects the irradiated X-rays and acquires a plurality of frame images related to the object region; And a filtering unit configured to filter X-rays irradiated from the X-ray source so that X-rays having a less dose than the region of interest enter the non-interested region among the object regions.

The X-ray imaging apparatus sets the region of interest using the plurality of frame images, and combines the frame images obtained while the small dose of X-rays is incident on the non-interested region with at least one previous frame image to form the frame It may further include an image processor for restoring an uninteresting region of the image.

The image processor averages the frame image and at least one previous frame image, sums the frame image and at least one previous frame image, or performs motion compensation temporal filtering on the frame image and the at least one previous frame image (motion-compensated temporal filtering) or motion-compensated spatial filtering may be applied to restore an uninterested region of the frame image.

The image processor may combine the frame image and at least one previous frame image for the non-interested region.

The image processor may further perform image registration or motion estimation and compensation for a reconstructed non-interested region in combination with the at least one previous frame image.

The image processor may further perform an image smoothing algorithm that matches the brightness and contrast of the region of interest and the region of interest to the frame image in which the region of non-interest is restored.

The controller may set an X-ray imaging mode based on the information on the frame image, information on the imaging mode, or information on the stage.

The controller, according to the size of the movement of the object of interest, the X-ray imaging mode is less than the region of interest in the entire imaging mode and the non-interesting region for irradiating X-rays of a uniform dose to the region of interest and the region of interest. It can be set to one of the region of interest modes for irradiating X-rays of the dose.

The controller increases the size of the region of interest according to the movement of the object of interest and the entire shooting mode in which the X-ray imaging mode irradiates a uniform dose of X-rays to the object region according to the size of the movement of the object of interest. The position can be set to one of the static shooting modes to fix.

The controller may adjust the X-ray imaging mode according to the size of the movement of the object of interest, the dynamic imaging mode of moving the region of interest according to the movement of the object of interest, and the size of the region of interest according to the movement of the object of interest. It can be set to one of the static shooting modes to increase and fix its position.

A control method of an X-ray imaging apparatus according to an aspect includes irradiating X-rays having a dose less than the region of interest to an uninterested region in an object region; And detecting the irradiated X-ray to obtain a frame image related to the object area.

In the control method of the X-ray imaging apparatus, the object region irradiates X-rays; Detecting the irradiated X-rays and acquiring a plurality of frame images related to the object region based on the detected X-rays; The method may further include setting a region of interest in the object region using the plurality of frame images.

Irradiating the non-interested region with an X-ray having a less dose than the region of interest may include filtering X-rays irradiated to the non-interested region.

The control method of the X-ray imaging apparatus may further include restoring an uninterested region of the frame image by combining a frame image obtained while a small dose of X-rays enters the uninterested region with at least one previous frame image. have.

It is possible to obtain an X-ray video that reduces the dose of X-rays but minimizes the deterioration of image quality or FOV loss of X-ray images.

1 is a control block diagram of an X-ray imaging apparatus according to an embodiment.
2 is a cross-sectional view showing the internal structure of an X-ray tube included in an X-ray imaging apparatus according to an embodiment.
3 is a control block diagram in which a configuration of an image processor included in an X-ray imaging apparatus according to an embodiment is specified.
FIG. 4 is a diagram illustrating an example of a region of interest when a stent is inserted into an aorta using angiography.
5 is a control block diagram of an X-ray imaging apparatus further including an object sensing unit of interest.
6 is a control block diagram in which a configuration of a control unit included in an X-ray imaging apparatus according to an embodiment is specified.
7A is a side cross-sectional view of a region of interest filter included in a filtering unit of an X-ray imaging apparatus according to an embodiment, and FIG. 7B is a plan view of an example of a region of interest filter.
8 is a cross-sectional view of a filtering unit having a plurality of ROI filters.
9A and 9B are diagrams schematically showing doses of X-rays incident on a region of interest and a region of interest.
10A is a diagram illustrating movement of a region of interest according to movement of an object of interest, and FIG. 10B is a diagram schematically showing an operation of tracking a region of interest moving.
11 is a control block diagram of an X-ray imaging apparatus further including a source/detector position detector.
12 is a view schematically showing a real-time image combined with a road map.
13A is a diagram illustrating a process of restoring the image quality of a frame image by combining previous images, and FIG. 13B is a diagram schematically showing an effect of reducing noise of a frame image by averaging with a previous image.
14 is a control block diagram of an X-ray imaging apparatus further including a mode control unit.
15 is an external view of an X-ray imaging apparatus according to an embodiment.
16 is a flowchart of a control method of an X-ray imaging apparatus according to an embodiment.
17 is a flowchart illustrating an example of controlling an X-ray imaging mode in a method of controlling an X-ray imaging apparatus.
18 is a flowchart illustrating another example of controlling an X-ray imaging mode in a method of controlling an X-ray imaging apparatus.
19 is a flowchart illustrating another example of controlling an X-ray imaging mode in a method of controlling an X-ray imaging apparatus.
20 is a flowchart illustrating another example of controlling an X-ray imaging mode in a method of controlling an X-ray imaging apparatus.

Hereinafter, embodiments of the X-ray imaging apparatus and its control method will be described in detail with reference to the accompanying drawings.

1 is a control block diagram of an X-ray imaging apparatus according to an embodiment, and FIG. 2 is a cross-sectional view showing an internal structure of an X-ray tube included in the X-ray imaging apparatus according to an embodiment.

Referring to FIG. 1, the X-ray imaging apparatus 100 generates X-rays and irradiates from an X-ray source 110 irradiated, an X-ray detector 120 that detects irradiated X-rays to obtain a frame image, and an X-ray source 110 It includes a filtering unit 140 for filtering X-rays, an image processor 150 for restoring the image quality of the obtained X-ray image, and a control unit 160 for controlling the filtering unit 140.

Referring to FIG. 2, the X-ray source 110 may include an X-ray tube 111 generating X-rays. An anode 111b and a cathode 111e are provided inside the glass tube 111a of the X-ray tube 111, and the inside of the glass tube 111a is made into a high vacuum state, and the filament 111h of the cathode 111e is heated to generate hot electrons. Order. The filament 111h may be heated by applying a current to the electric wire 111f connected to the filament.

The cathode 111e includes a filament 111h and a focusing electrode 111g for focusing electrons, and the focusing electrode 111g is also referred to as a focusing cup. When a high voltage is applied between the anode 111b and the cathode 111e, hot electrons are accelerated to generate X-rays while colliding with the target material 111d of the anode. High-resistance materials such as Cr, Fe, Co, Ni, W, and Mo may be used as the target material 111d of the positive electrode. The generated X-rays are irradiated to the outside through the window 111i, and a beryllium (Be) thin film may be used as a material for the window 111i.

The voltage applied between the anode 111b and the cathode 111e is referred to as a tube voltage, and its magnitude can be expressed by a crest value kvp. When the tube voltage increases, the speed of the hot electrons increases, and as a result, energy (photon energy) of X-rays generated by colliding with the target material increases. In addition, by arranging a filter in the irradiation direction of X-rays, the energy of the X-rays can also be adjusted. By placing a filter for filtering X-rays of a specific wavelength band on the front or rear of the window 111i, X-rays of a specific energy band can be filtered. have. For example, when a filter such as aluminum or copper is disposed, the energy of the irradiated X-rays increases as the X-rays of the low energy band are filtered.

The current flowing through the X-ray tube 111 is referred to as a tube current and can be expressed as an average value mA, and as the tube current increases, the dose of X-rays (the number of X-ray photons) increases. Therefore, the energy of the X-rays can be controlled by the tube voltage, and the dose of the X-rays can be controlled by the tube current and the X-ray exposure time.

The X-ray imaging apparatus 100 may generate an X-ray video by applying X-ray fluoroscopy, and may be applied to an X-ray diagnosis field such as angiography or various treatment fields using the same. The X-ray video may be generated and displayed in real time.

The X-ray imaging apparatus 100 continuously performs X-ray imaging to generate an X-ray video. There are a continuous exposure method and a pulse exposure method for continuously performing X-ray imaging.

When a continuous exposure method is applied, a low tube current is continuously supplied to the X-ray tube 111 to continuously generate X-rays, and when a pulse exposure method is applied, X-rays are generated according to a series of short pulses. Therefore, applying the pulse exposure method can reduce the dose and motion blurring of the X-rays. The X-ray imaging apparatus 100 may be applied to both of the above methods, but in the embodiments described below, it will be described as applying a pulse exposure method for convenience of description.

The X-ray source 110 may irradiate the X-ray multiple times according to a predetermined time interval or an arbitrary time interval in the subject area. Here, the predetermined time interval or any time interval may be determined according to a pulse rate or a frame rate. For example, the frame rate can be set to 30 frames per second (30 fps), 15 frames per second (15 fps), 7.5 frames per second (7.5 fps), etc., and the pulse rate is 30 pulses per second (30 pps), 15 pulses per second (15 pps) ), 7.5 pulses per second (7.5pps), and the like.

The object refers to an X-ray imaging object, that is, an object to express the inside of the X-ray image, and the object area refers to an area imaged as an X-ray image as a predetermined area including the object. Accordingly, the object area may correspond to the imaging area (FOV) of the X-ray imaging device 100 or may include the imaging area of the X-ray imaging device 100.

The object region includes at least one of a region of interest and a region of interest. Since the region of the object region that is not the region of interest is a region of interest, a detailed description of the region of interest and the region of interest will be described later.

The X-ray detector 120 detects X-rays and acquires a plurality of frame images of the object area. The frame image refers to each of a plurality of X-ray images obtained according to the frame rate of the X-ray imaging apparatus 100. The X-ray detector 120 may have a two-dimensional array structure including a plurality of pixels, and when the detected X-rays are converted into electrical signals for each pixel, an X-ray image of an object region is obtained.

The X-ray detector 120 may be applied to any of various structures for detecting X-rays and converting them into electrical signals. As an example, a direct method in which X-rays are directly converted into an electrical signal using a photoconductor such as a-Se, and X-rays are converted into visible light using a scintillator such as a CSI, and the visible light is an electrical signal. Any of the indirect methods converted to can be applied.

The filtering unit 140 filters X-rays irradiated from the X-ray source 110 so that X-rays having a dose smaller than the region of interest are incident on the non-interested region. This is to reduce the dose of X-rays, and X-ray filtering adds more doses of X-rays to the region of interest that contains a lot of useful information about the interior of the object, and less doses to regions of interest that have less information X-ray. Since X-rays are incident on the non-interested area, the photographing area FOV is not lost, and a description of the more specific operation of the filtering unit 140 will be described later.

The image processor 150 reconstructs a frame image obtained while X-rays having a dose smaller than the region of interest are incident on the non-interested region using at least one previous frame image. If the dose of X-rays is small, the signal-to-noise ratio (SNR) of the X-ray image may be lowered. Therefore, since the image processor 150 can restore the non-interested region of the current frame image using at least one previous frame image, a more detailed description of restoring the non-interested region will be described later.

Also, the image processor 150 analyzes the frame image of the object region to obtain information about the region of interest. A detailed description of the analysis of the frame image will also be described later.

The control unit 160 may control the X-ray source 110 and the filtering unit 140. To this end, information on the region of interest is provided from the image processor 150, and the X-ray source (based on the information on the region of interest) 110) and the filtering unit 140 may determine parameters for controlling.

Hereinafter, the operation of each component of the X-ray imaging apparatus 100 will be described in detail.

3 is a control block diagram in which the configuration of an image processor included in an X-ray imaging apparatus according to an embodiment is specified, and FIG. 4 is a diagram of an example of a region of interest.

Referring to FIG. 3, the image processor 150 analyzes a frame image related to an object region and restores image quality of a current frame image using an image analysis unit 151 that acquires information on a region of interest and previous frame images An image restoration unit 152 may be included.

As described above, the X-ray imaging apparatus 100 may continuously perform X-ray imaging to obtain an X-ray video related to an object region. The frame images obtained by the X-ray detector 120 are input to the image processor 150, and the image analysis unit 151 of the image processor 150 analyzes the input frame images to obtain information about a region of interest. .

First, in order to set a region of interest, the image analyzer 151 detects an object of interest by performing image processing such as object recognition on a frame image related to the object region. In order to detect the object of interest, image processing may be performed on the current frame image, and image processing may be performed on the current frame image and one or more previous frame images together. Since an object of interest may not exist in the current frame image, when one or more previous frame images are used together, detection performance of the object of interest may be improved.

In order to detect the object of interest, the feature of the object of interest may be pre-stored and an object corresponding to the pre-stored feature may be detected from the frame image of the object region. For example, a feature detectable from an X-ray image among features of the object of interest, such as a shape of an object of interest, an X-ray absorption characteristic, and a motion characteristic, may be stored in advance.

The object of interest is an object that the user must constantly watch during X-ray imaging, and may be a surgical instrument used in the object or a surgical site. For example, when the X-ray imaging apparatus 100 is used for angiography, these procedures are performed when a surgical tool such as a guide wire, a catheter, a needle, a balloon, or a stent is inserted into a blood vessel. Close observation of the tool is necessary. Therefore, the treatment tool can be set as an object of interest to store information about the feature in advance. In addition, when the treatment site is set as an object of interest, a site such as stenosis, aneurysms, and cancerous regions may be the object of interest.

As described above, it is possible to detect an object of interest using a feature of the object of interest stored in advance, as well as to detect an object of interest using a marker attached to the object of interest. The marker can be used for easy identification in the X-ray image, and the image processor 150 can improve the detection performance by detecting the marker instead of the object of interest. The marker may have properties of radiopacity to be identified in the X-ray image, and the material may be at least one selected from the group including stainless steel, steel, gold, platinum, and lead.

When an object of interest is detected, the image analysis unit 151 sets a certain area including the detected object of interest as an area of interest. The position and size of the region of interest may be determined in consideration of the location, size, or motion characteristics of the object of interest, and the uncertainty of the motion characteristics of the object of interest may also be considered.

As an example, the image analysis unit 151 may set the size of the region of interest if the motion of the object of interest is large or the motion characteristics of the object of interest are difficult to predict and the uncertainty is large.

Hereinafter, a specific example of setting the region of interest will be described with reference to FIG. 4.

In FIG. 4, an example of inserting a stent into a blood vessel using angiography is taken as an example. The stent 13a is injected into a blood vessel to prevent clogging of the blood vessel, and has a network-like shape. The stent 13a is mounted on the end of the long tube-shaped stent device 13 in a folded state, injected into the blood vessel, and unfolded in the form of a mesh at a required position.

Referring to FIG. 4, a guide wire 11 is first inserted to insert a stent device 13 into a blood vessel in an object region. The stent device 13 is inserted into the blood vessel along the guide wire 11, while the stent device 13 is inserted, the stent device 13, in particular, the stent 13a at the end may be an object of interest, and the stent The region of interest including (13a) may be the region of interest.

While the guide wire 11 is inserted, the guide wire 11 or the tip of the guide wire 11 may be an object of interest, and while the catheter is inserted to inject a contrast agent into a blood vessel, the catheter or catheter The end of can be the object of interest.

Meanwhile, the image analysis unit 151 may use information input from the outside to detect an object of interest. For example, when information on a type of a surgical tool, a type of a procedure, information on a surgical site, whether a contrast agent is injected, etc., an object of interest can be detected from a frame image based on the input information.

As an example, when the procedure to be performed is a stent implantation of the aorta, and information that a surgical tool to be inserted is a stent device, the image analysis unit 151 uses the information about the characteristics of the previously stored stent to perform a target region. The stent in the aorta is detected from the frame image.

The image analysis unit 151 may determine the motion characteristics of the object of interest while tracking the detected object of interest, and detecting, tracking, and acquiring information on the region of interest of the object of interest may include a frame image input to the image analysis unit 151 It can be made in real time according to their frame rate. Here, the acquisition of information about the region of interest includes detection of an object of interest, tracking, and setting of the region of interest based thereon.

The movement characteristics of the object of interest include information such as the location of the object of interest, the size of the movement, and the direction of movement. The size of the motion may include speed, but the motion of the object of interest may not have a certain pattern. Accordingly, the size of the motion may include various information indicating the degree of motion in addition to the speed.

Since the region of interest is a certain region including the object of interest, the region of interest is defined by the object of interest, and thus the motion characteristic of the region of interest may be determined according to the motion characteristics of the object of interest.

Meanwhile, the image analysis unit 151 may be used to set a region of interest by estimating periodic movements such as breathing or heartbeat of the patient. For example, an object of interest, such as a stent or catheter, may be moved by the patient's movement even if it does not move on its own. In this case, since the object of interest moves according to the movement pattern of the patient, it is possible to predict the movement of the patient and reset the region of interest using the motion. Specifically, it is possible to reset the region of interest by detecting the object of interest, setting the region of interest, and compensating for the location or size of the region of interest by using a movement amount or a movement direction according to a patient's periodic movement pattern.

5 is a control block diagram of an X-ray imaging apparatus further including an object sensing unit of interest.

In the embodiments described so far, it is assumed that an object of interest is set through an image processing on an X-ray image and a region of interest is set, but a separate sensor capable of estimating location information according to the movement of the object of interest to set the region of interest It is also possible to use. To this end, the X-ray imaging apparatus 100 may further include an object-of-interest sensing unit 170 that detects an object of interest, as illustrated in FIG. 5.

For example, if a variable magnetic field is applied to a certain region including the object of interest, and a coil is attached to the object of interest, the voltage applied to the coil varies according to the movement of the object of interest. Therefore, the voltage applied to the coil can be measured, and the position and the moving direction of the coil can be estimated based on the measured voltage. The position and direction of the coil can be treated as the position and direction of the object of interest. In this case, the object sensing unit 170 may include a magnetic field applying device for applying a magnetic field and a voltage sensor for measuring the voltage.

Or, by attaching an optically recognizable marker to the object of interest, and recognizing the marker using an optical sensor, the position and moving direction of the object of interest may be estimated. In this case, the object-of-interest sensing unit 170 may include an optical sensor capable of recognizing a marker.

The voltage sensor or the optical sensor can be mounted anywhere that can recognize the voltage applied to the coil attached to the object of interest or the marker attached to the object of interest. In the embodiment of the X-ray imaging apparatus 100, the mounting position of the sensors There are no restrictions.

The use of a voltage measurement sensor or an optical sensor to detect the object of interest is only examples, and in addition, the object of interest may be detected using various sensing methods.

As described above, when an object of interest is detected using a separate sensor, the object of interest may be detected even when the object of interest is located outside the X-ray irradiation range. When an object of interest outside the X-ray irradiation range is detected, the controller 160 warms up the filter driver 143 for rapid movement of the ROI filter 141 (see FIG. 7A) before the object of interest appears in the X-ray image. Alternatively, the region of interest filter 141 may be previously moved by estimating the moving speed and the moving direction of the object of interest.

Meanwhile, the embodiment of the X-ray imaging apparatus 100 also includes combining two or more of the above-described methods for the detection of the object of interest, thereby improving the accuracy of detection.

Information about the region of interest acquired by the image analysis unit 151, specifically, information such as the location, size, or motion characteristics of the region of interest is transmitted to the control unit 160 and used to control the filtering unit 140.

Meanwhile, the image analysis unit 151 may acquire information on image characteristics such as noise and contrast appearing on the frame image, as well as information on the region of interest, and these characteristics are transmitted to the control unit 160 to X-ray It can be used to control shooting conditions.

6 is a control block diagram in which a configuration of a control unit included in an X-ray imaging apparatus according to an embodiment is specified.

Referring to FIG. 6, the control unit 160 of the X-ray imaging apparatus 100 includes a shooting control unit 161 for controlling X-ray imaging parameters and a filtering control unit 162 for controlling the filtering unit 140.

The imaging control unit 161 controls various imaging parameters applied to X-ray imaging. The shooting parameter is also called an exposure parameter, and the automatic control of the shooting parameter in the X-ray imaging apparatus 100 is called an auto exposure control.

The imaging parameter may be at least one selected from the group including tube voltage, tube current, exposure time, filter type, imaging area (FOV), frame rate, pulse rate, and target material type.

The imaging parameter may be determined based on the frame image of the object area, or may be determined based on the inputted prior information before starting X-ray imaging. Hereinafter, embodiments of the former case will be described in detail.

The photographing control unit 161 may determine photographing parameters based on an analysis result of the image analysis unit 151. For example, when the image analysis unit 151 analyzes the frame image to determine characteristics such as the thickness or density of the object, the imaging control unit 161 based on the determination result, the tube voltage, tube current, and exposure suitable for the characteristics of the object It is possible to determine imaging parameters such as time, filter type, and target material type.

Also, the photographing control unit 161 may determine a photographing parameter based on the information on the region of interest acquired by the image analysis unit 151. As an embodiment, the photographing control unit 161 may control photographing parameters such as frame rate, tube current, and dose per frame according to the size of motion of the object of interest or the characteristics of the image displayed in the region of interest, and may be controlled respectively or simultaneously.

For example, the photographing control unit 161 increases the frame rate when the motion of the object of interest is large, thereby obtaining as much information as possible about the motion of the object of interest, and when the motion of the object of interest is small, increases the frame rate. By reducing it, the subject's exposure can be reduced.

Also, the photographing control unit 161 may control the dose per frame according to the noise level of the region of interest. For example, if the noise level of the region of interest is higher than a preset reference value, the dose per frame is increased to lower the noise level so that the region of interest can be seen more clearly, and if the noise level of the region of interest is lower than the preset reference value , It is possible to reduce the exposure of the object by reducing the dose per frame.

The filtering control unit 162 controls the filtering unit 140 based on the information on the region of interest acquired by the image analysis unit 151. To describe the operation of the filtering control unit 162, the configuration of the filtering unit 140 will be described with reference to FIG. 7 first.

7A is a side cross-sectional view of the ROI filter included in the filtering unit, and FIG. 7B is a plan view of an example of the ROI filter.

Referring to FIG. 7A, the filtering unit 140 includes a region of interest filter 141 and a filter driver 143 for moving the region of interest filter 141. The filter driving unit 143 may include a mechanical structure such as a motor that generates power and a gear that transmits the generated power to the region of interest filter 141.

The region-of-interest filter 141 can be moved on the xy plane or the z-axis by the filter driver 143, and the movement on the xy-plane is for matching the location of the region-of-interest filter 141 with the region of interest, z The movement on the axis is to match the size of the region of interest with the region of interest filter 141.

The collimator 131 may be disposed in an X-ray irradiation direction corresponding to the front of the X-ray source 110. The collimator 131 is made of a material that absorbs or blocks X-rays, such as lead or tungsten, to adjust the range of the imaging area (FOV) corresponding to the X-ray irradiation area of the X-ray source 110 and reduce scattering of X-rays.

The region of interest filter 141 may be positioned between the collimator 131 and the X-ray detector 120 to filter X-rays radiated from the X-ray source 110. The region-of-interest filter 141 may be made of a material that attenuates X-rays, and the X-rays are attenuated while passing through the region-of-interest filter 141 to reduce the dose. Therefore, when the ROI filter 141 is positioned at a position corresponding to the non-interested area of the object area, X-rays having a less dose than the ROI may be incident on the uninterested area.

In general, since the region of interest is surrounded by the region of interest, the region of interest filter 141 may have a ring shape in which the center is empty, that is, the opening 141b is formed in the center, as illustrated in FIG. 7B.

7B, the opening 141b may have a polygonal ring shape, as shown in the left-hand square ring of FIG. 7B, or the opening 141b may have a circular ring shape, as shown on the right side of FIG. 7B. The shape of 141) is not limited thereto, and the region of interest filter 141 may have various shapes according to characteristics of the region of interest, or a relationship between the region of interest and the region of interest.

The operation of the filtering control unit 162 will be described based on the configuration of the filtering unit 140 described above. The filtering control unit 162 generates a control signal for movement of the ROI filter 141 based on the information on the ROI, and transmits the generated control signal to the filter driver 143 to transmit the ROI filter 141 It can be moved to a position corresponding to an uninteresting area.

As a specific example, the filtering control unit 162 controls movement of the region of interest filter 141 on the xy plane so that the opening 141b of the region of interest filter 141 is positioned at a position corresponding to the region of interest, and the region of interest filter The movement of the region of interest filter 141 on the z-axis may be controlled so that the opening 141b of the (141) corresponds to the size of the region of interest.

The filtering control unit 162 may control not only the position of the ROI filter 141, but also the type or thickness of the ROI filter 141. Hereinafter, an operation of the filtering control unit 162 controlling the type or thickness of the ROI filter 141 will be described with reference to FIG. 8.

8 is a cross-sectional view of a filtering unit having a plurality of ROI filters.

Referring to FIG. 8, the region of interest filter 141 may be formed of a plurality of filter layers independently movable on the xy plane or the z-axis, and each filter layer includes a first region of interest filter 141-1 and a second region. It becomes the region of interest filter 141-2 and the third region of interest filter 141-3.

The first region of interest filter 141-1, the second region of interest filter 141-2, and the third region of interest filter 141-3 have the same type of fitting material and different thicknesses, The type and thickness of the filter material may be different, or the type of filter material may be different and the thickness may be the same, or both the type and thickness of the filter material may be the same.

The filtering control unit 162 may determine a difference in dose of X-rays to be incident on the region of interest and the region of interest based on image characteristics of the region of interest and the region of interest, such as noise, motion, and contrast, and filter the region of interest according to the determined difference in dose The type or thickness can be variably controlled.

As an example, the filtering control unit 162 may use a combination of the first region of interest filter 141-1, the second region of interest filter 141-2, and the third region of interest filter 141-3. First, based on the image characteristics of the region of interest and the region of interest, the difference in the dose of X-rays to be incident on the region of interest and the region of non-interest is determined, and the region-of-interest filters 141-1,141- that can incident X-rays according to the determined dose 2,141-3).

For example, when it is determined that the second region of interest filter 141-2 and the third region of interest filter 141-3 are required, the filtering control unit 162 may include the second region of interest filter 141-2 and the third region. The region-of-interest filter 141-3 is positioned at a position capable of filtering X-rays irradiated from the X-ray source 110 or passed through the collimator 131, and the first region-of-interest filter 141-1 is excluded from the filtering location. . The filtering control unit 162 may control the position of the region-of-interest filter 141 by moving it on the z-axis or moving it on the xy plane.

As the region of interest filter 141 is closer to the X-ray source 110 or the collimator 131, the width of the X-rays passing through the opening 141b of the region of interest filter 141 is narrowed. Therefore, in order to increase the region of interest by reducing the filtering region, if the region of interest filter 141 is moved toward the X-ray source 110 or the collimator 131 on the z-axis, and the region of interest is reduced by increasing the filtering region, The region of interest filter 141 is moved on the z-axis to the opposite side of the X-ray source 110 or the collimator 131.

9A and 9B are diagrams schematically showing doses of X-rays incident on a region of interest and a region of interest.

9A shows the dose of X-rays incident on an arbitrary straight line AB passing through the region of interest and the region of interest. When the filtering control unit 162 moves the region of interest filter 141 to a position corresponding to the region of non-interest, X-rays having a less dose than the region of interest enter the non-interested region as shown in FIG. 9A. Although the dose is small, X-rays enter the non-interested area, thereby obtaining information on the entire imaging area.

As described above, the X-ray imaging apparatus 100 can obtain a video by continuously performing X-ray imaging, and as a result, as long as the region of interest exists in the object region, the dose of X-rays incident on the region of interest and the non-interested region is shown. 8b. For example, the dose of X-rays incident on the region of interest may be 1/5, 1/10 or 1/20 or less of the dose of X-rays incident on the region of interest.

10A is a diagram illustrating movement of a region of interest according to movement of an object of interest, and FIG. 10B is a diagram schematically showing an operation of tracking a region of interest moving.

The X-ray video may represent a motion existing in the object area, and when the subject of the motion is the object of interest, the area of interest may be moved by the motion of the object of interest. As an example, when performing a stent implantation procedure in which a stent device 13 is inserted into a blood vessel as illustrated in FIG. 10A, the stent 13a, which is an object of interest, moves to a target position in the blood vessel and moves the stent 13a The region of interest also moves accordingly.

Earlier, it was said that the image analysis unit 151 can detect and track an object of interest in real time. As shown in FIG. 10B, when the region of interest moves, the image analysis unit 151 tracks it in real time. The filtering control unit 162 controls the ROI filter 141 to move together in synchronization with the movement of the ROI.

On the other hand, if the image analysis unit 151 fails to detect the object of interest, or if it detects it, a very low reliability may occur. For example, the reliability of detection may be obtained by various algorithms that calculate the reliability of the object recognition result, and when the reliability value is less than a preset reference value, it may be determined that the detection result of the object of interest is unreliable. If the detection of the object of interest fails or the reliability is less than a preset reference value, the image analysis unit 151 may maintain the previous region of interest without resetting the region of interest.

11 is a control block diagram of an X-ray imaging apparatus further including a source/detector position detector.

The location of the X-ray source 110 or the X-ray detector 120 may vary during X-ray imaging. The user may manually move the X-ray source 110 or the X-ray detector 120, or the X-ray source 110 or the X-ray detector 120 may be moved automatically. Even if the object of interest does not move, the relative position between the object of interest and the X-ray source 110 or the X-ray detector 120 may vary while the X-ray source 110 or the X-ray detector 120 moves. In this case, similarity between the previous frame image and the current frame image may deteriorate, and even if the image analysis unit 151 detects and tracks the object of interest in real time, performance or reliability of object detection may be deteriorated. have. Therefore, when the X-ray source 110 or the X-ray detector 120 moves, the image analysis unit 151 detects an object of interest by reflecting the position change of the X-ray source 110 or the X-ray detector 120 and detects the region of interest. Can be reset. Specifically, the image analysis unit 151 may estimate a relative position change with an object of interest according to the position change of the X-ray source 110 or the X-ray detector 120, and reflect the relative position change in detecting the object of interest Thus, it is possible to prevent a decrease in detection performance or reliability.

To this end, the X-ray imaging apparatus 100 may further include a source/detector position detection unit 180 capable of detecting a position change of the X-ray source 110 or the X-ray detector 120 as illustrated in FIG. 11. have. The source/detector position detector 180 may be implemented as a position sensor to obtain position information of the X-ray source 110 or the X-ray detector 120, and the X-ray source 110 or the X-ray detector 120 may be the same as the motor. When it can be automatically moved by the driving unit, it may be implemented as a sensor that measures the driving amount of the driving unit to obtain information about the moving amount or the moving direction of the X-ray source 110 or the X-ray detector 120.

In addition, when the X-ray source 110 or the X-ray detector 120 automatically moves under the control of the control unit 160, the source/detector position detection unit 180 is not provided, and the X-ray source from the control unit 160 is not provided. It is also possible to obtain information on the movement amount or the movement direction of the 110 or X-ray detector 120.

In the embodiment of the X-ray imaging apparatus 100, there is no limitation on a configuration or a method for obtaining information on the position change of the X-ray source 110 or the X-ray detector 120. Information regarding a position change of the source 110 or the X-ray detector 120 may be obtained.

In the example of FIG. 10B, the region of interest is also moved according to the movement of the object of interest, but according to another example, the size of the region of interest may be changed according to the movement of the object of interest. When the object of interest moves, the image analysis unit 151 may fix the position of the region of interest, but increase the size to include the moved object of interest. Accordingly, the rate of increase in the size of the region of interest varies according to the size of movement of the object of interest.

Alternatively, as described later, it is also possible to fix the position of the region of interest and increase the size only when the size of movement of the object of interest is small.

Since the X-ray imaging apparatus 100 can perform road mapping, it is possible to adjust the X-ray dose through detection and tracking of a region of interest in performing road mapping.

12 is a view schematically showing a real-time image combined with a road map.

Referring to FIG. 12, first, a roadmap mask is generated by injecting a contrast agent into a target blood vessel into which a surgical tool is to be inserted. The roadmap mask acts like a blood vessel map and corresponds to a still image. The image processor 150 may combine the roadmap mask with the following subsequent live fluoroscopic images to obtain an image such that a surgical tool is superimposed on the roadmap.

As an example, the following real-time perspective image is subtracted from the roadmap mask to remove the background and obtain an image in which the surgical tool and the target blood vessel appear in excellent contrast. Alternatively, the roadmap mask may be subtracted from the next real-time perspective image.

The image processor 150 may perform digital subtraction angiography (DSA) on these images before combining the roadmap mask and the real-time perspective image. DSA subtracts the image before the contrast agent is added from the image after the contrast agent is injected, thereby improving the recognition rate of blood vessels by removing the background anatomy or tissue.

Here, the real-time perspective image is an image in which a low dose of X-rays is incident on an uninterested region through real-time detection and tracking of a region of interest. When a low-dose real-time perspective image is combined with a roadmap, it is possible to obtain a real-time image with excellent contrast between blood vessels and surgical instruments while reducing the dose.

The image restoration unit 152 may perform image restoration or image enhancement to improve image quality of a region of interest of a frame image.

The image reconstruction unit 152 uses a denoising algorithm such as spatial filtering, temporal filtering, spatio-temporal filtering, and super-resolution reconstruction. By doing so, the region of interest of the frame image can be restored. A detailed description of restoration to the region of interest will be described later.

In addition, the image restoration unit 152 may enhance a region of interest of the frame image using a histogram or wavelet-based contrast enhancement algorithm, a detail enhancement algorithm such as an edge enhancement filter, and the like.

On the other hand, since low-dose X-rays are incident in the non-interested region, the signal-to-noise ratio may appear in the non-interested region of the frame image. Therefore, the image restoration unit 152 performs a restoration operation to improve the image quality of the non-interested area. Hereinafter, an operation of restoring an uninterested region of a frame image will be described in detail with reference to FIGS. 13A and 13B.

13A is a diagram illustrating a process of restoring the image quality of a frame image by combining previous images, and FIG. 13B is a diagram schematically showing an effect of reducing noise of a frame image by averaging with a previous image.

Referring to FIG. 13A, the image restoration unit 152 may perform image restoration to improve image quality by combining the current frame image with at least one previous frame image. At this time, the combination between the frame images may be made for an uninteresting region. According to the example of FIG. 13A, by combining and restoring the current frame image with two previous frame images, a frame image having an excellent signal-to-noise ratio, such as a frame image for a region of interest in which a high dose of X-rays is incident, can be obtained.

As an example of a method of combining a current frame image and at least one previous frame image, a method of summing the current frame image and at least one previous frame image, a method of averaging the current frame image and at least one previous frame image, edge direction Considering such image characteristics, the filter applied to the current frame image is varied, the method of applying motion-compensated temporal filtering, the method of applying motion-compensated spatial filtering, etc. There is this. Here, the summation may be a simple summation or a weighted summation, and the average may be a simple average or a weighted average.

The image restoration unit 152 may use one of the above methods, or may combine and use two or more methods.

Referring to FIG. 13B, if the current frame image is called a frame image m, the frame image m and the frame image m-1 can be averaged to restore the frame image m, and if necessary, the frame image m and more previous frame images. You can also average them together.

When the number of previous images used for averaging increases, the noise reduction rate of the image also increases. For example, by averaging frame images m and 4 previous frame images, noise can be reduced to about 60%. The image restoration unit 152 may determine the number of previous frame images used in the average in consideration of noise of the current frame image, image lag, and the like.

In addition, the image reconstruction unit 152 may perform additional image enhancement on the uninterested region of the reconstructed frame image. As an example, alignment or registration or motion prediction/compensation between frame images to reduce resolution and image blurring that may occur when combining the current frame image and the previous frame image. You can do

As an algorithm for matching between frame images, a feature-based algorithm, an intensity-based algorithm, or a mixture of features and signal strength may be used.

Motion field models for motion prediction/compensation include translational motion, block-based piecewise translational motion, rotation, scaling, and non-rigid deformable motion. Etc. can be used.

In addition, the image restoration unit 152 may perform image restoration not only for the region of interest but also for the region of interest. At this time, the reconstruction of the image may be performed by combining the current frame image and the previous frame image for the region of interest. In restoring both the region of interest and the region of interest, spatial denoising filtering may be performed on both regions, temporal denoising filtering may be applied, and both spatial filtering and temporal filtering may be applied. You may. Here, both spatial filtering and temporal filtering may be motion compensation filtering.

Alternatively, appropriate filtering may be selected according to motion characteristics of the non-interesting region and the region of interest. As an example, spatial filtering may be applied when the motion is large or fast, and temporal filtering may be applied otherwise. Therefore, when the movement in the region of interest is large or fast, spatial filtering may be applied to the region of interest, and temporal filtering may be applied to the region of interest.

Alternatively, while temporal filtering is applied to both the region of interest and the region of interest, it is also possible to optimize the image quality of the entire image including the region of interest and region of interest by varying the intensity of filtering. For example, if the similarity between temporally adjacent frame images is large because the movement of the object of interest is large, the effect of filtering may be reduced when temporal filtering is applied. In this case, temporal filtering of relatively weak intensity may be applied to the region of interest, and temporal filtering of relatively strong intensity may be applied to the region of interest. Accordingly, it is possible to restore the image quality of an uninterested region to which relatively low-dose X-rays are irradiated, and to prevent blurring of an object of interest with complex movement.

In order to adjust the intensity of temporal filtering, the number of previous frame images used to reconstruct the current frame image may be adjusted, or a weight applied to each previous frame image may be adjusted. For example, to apply temporal filtering of weak intensity, a relatively small number of previous frame images may be used for reconstruction. Alternatively, the same number of previous frame images as in the case of applying strong intensity filtering may be used, but the weight applied to the previous frame image may be adjusted according to temporal proximity to the current frame image. For example, a higher weight may be applied to a previous frame image temporally close to a current frame image, and a lower weight may be applied to a temporally distant previous frame image.

Then, the image restoration unit 152 may perform an image equalization algorithm to match the brightness and contrast of the region of interest and the region of interest of the frame image.

On the other hand, if the dose of X-rays incident on the region of interest and the region of interest is different by X-ray filtering of the region of interest, artifacts may be generated in the boundary region of the two regions. Therefore, the image restoration unit 152 may reduce artifacts generated in the boundary region by performing image processing using a boundary correction algorithm on the boundary region between the region of interest and the region of interest.

The characteristics of the boundary region may vary depending on the material, shape, and location of the region of interest filter 141. Accordingly, when the image restoration unit 152 performs image processing by applying a boundary correction algorithm to the boundary region, characteristics of the region of interest filter 141 may be considered.

As an example of the boundary correction algorithm applied by the image restoration unit 152, a linear blending algorithm may be used. Linear blending algorithms are also called feathering or alpha blending. The linear blending algorithm is a method of fusion by weighting each pixel value in a region where a boundary occurs, and as the area where a weight is increased, a boundary region can be naturally formed.

As another example of the boundary correction algorithm applied by the image reconstruction unit 152, a multi band blending algorithm may be used. The multi-band blending algorithm is a method of separating high-frequency and low-frequency images for each band through a Gaussian pyramid, separating the band images based on the maximum weight function, and then fusing different weights for each band image to fuse them. Narrow and low-frequency images are widely fused, so it is possible to effectively fuse detail components.

The above-described boundary correction algorithms are only examples that can be applied to an embodiment of the disclosed invention, and the type of the boundary correction algorithm used by the image restoration unit 152 is not limited to these examples.

Meanwhile, when the region of interest filter 141 moves while the X-ray is irradiated, the pattern of the boundary region may be changed. Therefore, the image restoration unit 152 may estimate the pattern of the boundary region using information on the movement speed or position change of the region of interest filter 141 during X-ray irradiation, and correct the boundary region using the information. have.

14 is a control block diagram of an X-ray imaging apparatus further including a mode control unit.

Referring to FIG. 14, the control unit 160 of the X-ray imaging apparatus 100 may further include a mode control unit 163 for controlling the X-ray imaging mode. The X-ray imaging mode that can be controlled by the mode controller 163 includes a region of interest mode and a whole imaging mode. The region of interest mode is a photographing mode in which a region of interest is detected and a difference between the region of interest and the region of non-interest is detected as described above, and a full field of view (Full FOV) mode differs in the X-ray dose between the region of interest and the region of interest. This is a general shooting mode in which a uniform dose of X-rays is irradiated to an object region without being placed.

The mode control unit 163 may control the X-ray imaging mode based on information on the frame image analyzed by the image analysis unit 151, information on the imaging mode, or information on the stage. In controlling the X-ray imaging mode, the mode control unit 163 may consider all of these information or only some of them.

The information on the frame image may include information on a region of interest or information on image characteristics. Hereinafter, an operation in which the mode control unit 163 controls the X-ray imaging mode based on information on the region of interest will be described in detail.

Since the information on the region of interest includes the motion characteristics of the object of interest, the mode controller 163 may control the X-ray imaging mode based on the size of the movement of the object of interest.

Specifically, when the movement of the object of interest is large, it may be more efficient to irradiate the X-ray of a uniform dose to the entire imaging area than to change the X-ray irradiation amount for each region according to the movement of the object of interest. Therefore, when the movement of the object of interest is large, the mode control unit 163 may set the X-ray imaging mode to the entire imaging mode, so that X-rays of a uniform dose are irradiated to the entire imaging area.

On the other hand, the mode control unit 163 can compare the size of the motion of the object of interest with a preset reference value to determine whether the size of the motion is large. The reference value can be set based on experiment, statistics, simulation, theory, etc. . In order to distinguish it from other reference values, which will be described later, the reference value, which is a setting criterion for the entire shooting mode, capable of determining whether the size of the motion is large is referred to as a first reference value.

When the movement of the object of interest is not large, the mode controller 163 may set the X-ray imaging mode as the region of interest mode, and the region of interest mode may be further divided into two modes based on the size of the movement of the object of interest. .

When the movement of the object of interest is small, since the X-ray irradiation amount for each region needs to be finely changed, the size of the region of interest is increased by a certain amount to include the movement of the object of interest, and it may be more efficient not to move. In this embodiment, the X-ray imaging mode performing such an operation is referred to as a static imaging mode. The mode controller 163 may set the X-ray imaging mode to the static imaging mode when the size of the movement of the object of interest is smaller than a preset second reference value.

The mode control unit 163 moves the region of interest according to the movement of the object of interest when the movement of the object of interest is intermediate, that is, when the size of the movement of the object of interest is larger than a preset second reference value, the region of interest filter By moving the (141) to a position corresponding to the non-interested area to set the X-ray irradiation amount as a shooting mode, the shooting mode will be a dynamic shooting mode (dynamic mode).

On the other hand, the mode control unit 163 may set the X-ray imaging mode to only two of the above-described whole shooting mode, static shooting mode, and dynamic shooting mode, or to only one mode.

Specifically, the mode control unit 163 may set the X-ray imaging mode as the entire imaging mode when the size of the movement of the object of interest is larger than the preset third reference value, and set the X-ray imaging mode as the static imaging mode when the motion size of the object of interest is greater than the preset third reference value. Here, the preset third reference value may be the same value as the first reference value or the second reference value, or may be a different value.

Alternatively, if the size of the movement of the object of interest is larger than a preset fourth reference value, the X-ray imaging mode may be set as the entire imaging mode, and if it is small, the X-ray imaging mode may be set as the dynamic imaging mode. Here, the fourth reference value may be the same value as the first reference value, the second reference value, or the third reference value, or may be a different value.

Alternatively, if the size of the movement of the object of interest is greater than a preset fifth reference value, the X-ray imaging mode may be set as a dynamic imaging mode, and if the motion size of the object of interest is small, the X-ray imaging mode may be set as a static imaging mode. Here, the fifth reference value may be the same value as the first reference value, the second reference value, the third reference value, or the fourth reference value, or may be a different value.

Alternatively, regardless of the size of the movement of the object of interest, it is also possible to set the X-ray shooting mode only to the static shooting mode or to the dynamic shooting mode only.

Hereinafter, an operation in which the mode control unit 163 controls the X-ray imaging mode based on information on the imaging mode or information on the stage will be described.

The imaging modes that the X-ray imaging apparatus 100 can perform include a general X-ray fluoroscopic mode and a digital subtraction angiography (DSA) mode.

Since the DSA image acquired by the DSA mode can be usefully used to grasp the position or shape of the blood vessel to be observed in the entire object area, when the imaging mode of the X-ray imaging apparatus 100 is the DSA mode, the mode controller 163 X-ray shooting mode can be set to full shooting mode.

In the case of the X-ray fluoroscopy mode, the region of interest mode may be set. Accordingly, the dynamic shooting mode or the static shooting mode may be set according to the motion characteristics of the object of interest, but as described above, when the motion of the object of interest is large, it may be set to the entire shooting mode.

The information on the stage includes information about which stage is the current stage among various stages for X-ray imaging. For example, information regarding whether the catheter is inserted, the stent is inserted, or the contrast agent is injected may be information about the stage.

As an example, even if the imaging mode is an X-ray fluoroscopy mode, when the current step is a contrast injection step, the X-ray imaging mode may be set as the entire imaging mode in order to grasp the overall structure of the object.

Meanwhile, since information on the imaging mode or information on the stage may be determined by the device itself or input by a user, the mode control unit 163 may display the entire image based on various information input by the user in addition to the examples described above. The X-ray imaging mode may be set according to whether information is important or whether image information of a region of interest is important.

15 is an external view of an X-ray imaging apparatus according to an embodiment.

As an example, the X-ray imaging apparatus 100 may have a C-arm structure as shown in FIG. 15. The X-ray source assembly 107 and the X-ray detector 120 may be mounted at both ends of a C-shaped C-arm 101, respectively. The C-arm 101 is connected to the main body 103 through a connecting shaft 105 and can be rotated in an orbital direction.

An X-ray source 110, a collimator 131, and a filtering unit 140 may be provided inside the X-ray source assembly 107. When the patient table 109 is located between the X-ray source assembly 107 and the X-ray detector 120 and an object is placed on the patient table 109, the X-ray source 110 irradiates X-rays to the object and the X-ray detector 120 The irradiated X-ray is detected to obtain an X-ray image of the object.

As described above, the X-ray imaging apparatus 100 may perform X-ray imaging according to various imaging modes, and can obtain a real-time video of an object, so the user is provided with a plurality of screens for various procedures or diagnosis A procedure or diagnosis may be performed while viewing the display unit 172 capable of displaying an image.

As mentioned above, when the image analysis unit 151 obtains information about the region of interest, or the imaging control unit 161 sets the imaging parameters, or the mode control unit 163 controls the X-ray imaging mode, from the user You can use input information. The user may input necessary information through the input unit 171 provided in the X-ray imaging apparatus 100.

Hereinafter, an embodiment of a method of controlling an X-ray imaging apparatus will be described.

16 is a flowchart of a control method of an X-ray imaging apparatus according to an embodiment. The aforementioned X-ray imaging apparatus 100 may be used as a control method according to an embodiment. Therefore, it goes without saying that the above description of the embodiment of the X-ray imaging apparatus 100 of FIGS. 1 to 15 can be applied to the control method of the X-ray imaging apparatus.

Referring to FIG. 16, X-rays are irradiated to a target area at predetermined time intervals (310 ). It is also possible to continuously irradiate X-rays, but in this embodiment, a pulse exposure method for irradiating X-rays at regular time intervals is adopted to reduce the dose of X-rays and improve temporal resolution. Here, the predetermined time interval may be determined according to the pulse rate. For example, when the pulse rate is 30 pulses per second (30pps), X-rays are irradiated 30 times per second.

The irradiated X-ray is detected to obtain a frame image of the object region (311). Here, the object area may coincide with the X-ray imaging area, and acquisition of the frame image may be performed in real time in synchronization with X-ray irradiation.

Information on a region of interest is obtained from a frame image of the region of the object (312). Obtaining information about a region of interest includes detecting an object of interest and setting a region of interest based on the detected object of interest. Specifically, an object of interest is detected from a frame image related to the object area, and a predetermined area including the detected object of interest is set as an area of interest. The position and size of the region of interest may be determined in consideration of the location, size, or motion characteristics of the object of interest, and the uncertainty of the motion characteristics of the object of interest may also be considered. The information on the region of interest includes the location, size, or motion characteristics of the region of interest, and the movement characteristics of the region of interest may be defined by the movement characteristics of the object of interest.

The region-of-interest filter is controlled such that less dose of X-rays enters the region of interest than the region of interest (313). The region of interest filter 141 is disposed to enable position control between the X-ray source 110 irradiating X-rays and the X-ray detector 120 detecting X-rays. Accordingly, the region of interest filter 141 may be positioned at a position corresponding to the region of interest, such that less dose of X-rays is incident on the region of interest. The region of interest may be set in real time according to the frame rate, and if the region of interest moves, the region of interest filter 141 is moved to a location corresponding to the region of interest.

Meanwhile, the control of the region of interest filter may also include adjusting the difference in the dose of X-rays to be incident on the region of interest and the region of interest based on image characteristics of the region of interest and the region of interest, such as noise, motion, and contrast.

Since low-dose X-rays are incident on the non-interested region, the signal-to-noise ratio is low in the non-interested region of the frame image. Accordingly, the current frame image is reconstructed using at least one previous frame image to improve the image quality of the non-interested region (314). Specifically, the current frame image may be combined with at least one previous frame image, and a method of combining the current frame image and the previous frame image may average or sum the current frame image and the previous frame image, or appear in the previous frame image. How to apply the filter applied to the current frame image variably, or to apply motion-compensated temporal filtering, motion-compensated spatial filtering in consideration of image characteristics such as noise and edge direction ). Here, the inter-image coupling may be performed for an uninteresting region.

In addition, additional image enhancement may be performed on the reconstructed frame image. As an example, alignment or registration or motion prediction/compensation between frame images to reduce resolution and image blurring that may occur when combining the current frame image and the previous frame image. You can do

On the other hand, a restoration operation for improving the image quality of an image may be performed on a region of interest of a frame image, such as a spatial filter, a temporal filter, a spatio-temporal filter, and a super resolution. A region of interest in a frame image may be reconstructed using a denoising algorithm such as super-resolution reconstruction, and a contrast enhancement algorithm based on a histogram or wavelet, edge enhancement filter, etc. The region of interest of the frame image may be enhanced using a detail enhancement algorithm or the like.

Then, an image equalization algorithm is performed to match the brightness and contrast of the region of interest and the region of interest of the frame image, and the restored frame image is displayed in real time on the display unit (315).

A control method of an X-ray imaging apparatus according to an embodiment may automatically control an X-ray imaging mode based on information on a frame image, information on an imaging mode, or information on a stage. An embodiment of controlling the X-ray imaging mode based on the size of the movement of the object of interest will be described.

17 is a flowchart illustrating an example of controlling an X-ray imaging mode in a method of controlling an X-ray imaging apparatus.

Referring to FIG. 17, X-rays are irradiated to the object area at predetermined time intervals (320), and the irradiated X-rays are detected to obtain a frame image of the object area (321). Information on a region of interest is obtained from a frame image of the region of the object (322). Here, the information on the region of interest includes the size of movement of the object of interest.

If the size of the motion of the object of interest is greater than the first reference value (YES in 323), the X-ray imaging mode is set to the entire imaging mode (324), and X-ray imaging is performed accordingly. Full FOV mode is a general shooting mode that does not make a difference in the X-ray dose between the region of interest and the region of interest.

If the size of the motion of the object of interest is smaller than the first reference value (No in 323), it is determined whether it is greater than the second reference value (325). If the size of the movement of the object of interest is greater than the second reference value (YES in 325), the X-ray imaging mode is set to the dynamic imaging mode (326), and X-ray imaging is performed accordingly. The dynamic photographing mode is a mode in which the region of interest is moved according to the movement of the object of interest, among the region of interest modes having a difference in X-ray dose between the region of interest and the region of interest.

If the size of the motion of the object of interest is smaller than the second reference value (No in 325), the X-ray imaging mode is set to the static imaging mode (327), and X-ray imaging is performed accordingly. The static shooting mode is a mode in which only the size of the region of interest is increased by a certain amount to include the movement of the object of interest, and the movement is not performed.

18 is a flowchart illustrating another example of controlling an X-ray imaging mode in a method of controlling an X-ray imaging apparatus.

Referring to FIG. 18, X-rays are radiated to a target area at predetermined time intervals (330), and the irradiated X-rays are detected to obtain a frame image of the target area (331). Information on a region of interest is obtained from a frame image of the region of the object (332). Here, the information on the region of interest includes the size of movement of the object of interest.

If the size of the movement of the object of interest is greater than the reference value (YES in 333), the X-ray imaging mode is set to the entire imaging mode (334), and X-ray imaging is performed accordingly.

If the size of the motion of the object of interest is smaller than the reference value (No in 333), the X-ray imaging mode is set to the dynamic imaging mode (335), and X-ray imaging is performed accordingly. Here, the reference value may be the same value as the first reference value or the second reference value in the example of FIG. 17, or may be a different value.

19 is a flowchart illustrating another example of controlling an X-ray imaging mode in a method of controlling an X-ray imaging apparatus.

Referring to FIG. 19, X-rays are irradiated to a target area at predetermined time intervals (340), and the irradiated X-rays are detected to obtain a frame image of the target area (341). Information on a region of interest is obtained from a frame image of the region of the object (342). Here, the information on the region of interest includes the size of movement of the object of interest.

If the size of the motion of the object of interest is greater than the reference value (YES in 343), the X-ray imaging mode is set to the dynamic imaging mode (344), and X-ray imaging is performed accordingly.

If the size of the motion of the object of interest is smaller than the reference value (NO in 343), the X-ray imaging mode is set to a static imaging mode (345), and X-ray imaging is performed accordingly. Here, the reference value may be the same as the first reference value, the second reference value in the example of FIG. 17, or the reference value in the example of FIG. 16, or a different value.

20 is a flowchart illustrating another example of controlling an X-ray imaging mode in a method of controlling an X-ray imaging apparatus.

Referring to FIG. 20, X-rays are irradiated to a target area at predetermined time intervals (350), and the irradiated X-rays are detected to obtain a frame image of the target area (351). Information about a region of interest is obtained from a frame image of the region of the object (352). Here, the information on the region of interest includes the size of movement of the object of interest.

If the size of the motion of the object of interest is greater than the reference value (YES in 353), the X-ray imaging mode is set to the entire imaging mode (354), and X-ray imaging is performed accordingly.

If the size of the motion of the object of interest is smaller than the reference value (No in 353), the X-ray imaging mode is set to the static imaging mode (355), and X-ray imaging is performed accordingly. Here, the reference value may be the same as the first reference value, the second reference value in the example of FIG. 17, the reference value in the example of FIG. 18, or the same value as the reference value in the example of FIG. 19.

In addition, according to another example of controlling the X-ray imaging mode, it is also possible to set the X-ray imaging mode only to the static shooting mode or only the dynamic shooting mode regardless of the size of movement of the object of interest.

Hereinafter, an example of a control method of an X-ray imaging apparatus that controls an X-ray imaging mode based on information on an imaging mode or information on a stage will be described.

Imaging mode includes a general fluoroscopic mode (DSA), digital subtraction angiography (DSA) mode, and information about the stage, whether the current stage is a catheter insertion stage, a stent insertion stage, or a contrast agent administration among various stages for X-ray imaging. It may include information on whether or not the step.

As an example, the region of interest in which the X-ray imaging mode is set to the entire imaging mode when the imaging mode is the DSA mode and the X-ray imaging mode is set to the default among the dynamic shooting mode or the static shooting mode in the X-ray perspective mode Mode.

On the other hand, in the case of the X-ray fluoroscopy mode, it is also possible to set to one of the entire shooting mode, the dynamic shooting mode, or the static shooting mode based on the size of movement of the object of interest, as shown in FIGS. 17 to 20 above.

According to the above-described X-ray imaging apparatus and its control method, it is possible to lower the dose of all X-rays by injecting low-dose X-rays into the region of interest, and to perform low-dose X-rays by performing image restoration on the non-interested region of the frame image. Due to this, it is possible to improve the deteriorated image quality. Therefore, while reducing the dose of X-rays, it is possible to obtain high-quality X-ray images.

In addition, since the region-of-interest filter automatically moves according to the location of the region of interest and does not require a separate user manipulation, it is possible to ensure the continuity of the procedure using the X-ray imaging apparatus.

100: medical imaging device 110: X-ray source
120: X-ray detector
140: filtering unit
150: image processor
160: control unit

Claims (49)

An X-ray source irradiating X-rays to an object region including the object of interest;
An X-ray detector that detects the irradiated X-rays and acquires frame images related to the object region based on the detected X-rays;
A filtering unit configured to filter X-rays irradiated from the X-ray source so that X-rays having a less dose than the region of interest are incident on the non-interested region among the object regions; And
And a controller configured to set an X-ray imaging mode according to the size of movement of the object of interest. According to claim 1,
The region of interest is set by using the frame images, a current frame image is combined with a previous frame image among image frames acquired while a small dose of X-rays is incident on the non-interested region, and based on the combined frame images The X-ray imaging apparatus further comprises an image processor that performs image restoration on an uninterested region of the current frame image. According to claim 2,
The control unit controls the filtering unit,
The image processor,
An X-ray imaging apparatus that obtains information about the region of interest from the current frame image and transmits it to the control unit. According to claim 2,
The filtering unit,
A region-of-interest filter made of a filter material that attenuates X-rays; And
X-ray imaging apparatus including a filter driver for moving the filter of interest. According to claim 2,
The image processor,
An X-ray imaging apparatus that detects an object of interest from the current frame image and sets the region of interest based on the location, size, or motion characteristics of the object of interest. The method of claim 5,
The image processor,
The X-ray imaging apparatus detects the object of interest by detecting a marker attached to the object of interest from the frame image. The method of claim 5,
The image processor,
An X-ray imaging apparatus that estimates a periodic motion pattern of the target area and resets the region of interest using the estimated motion pattern. The method of claim 4,
X-ray imaging device further comprising; an object detection unit for detecting the object of interest. The method of claim 8,
The control unit,
An X-ray imaging apparatus for preheating the filter driver based on the location of the object of interest. The method of claim 4,
The image processor,
Estimate the moving direction and the moving speed of the object of interest based on the position of the object of interest,
The control unit,
An X-ray imaging apparatus for moving the filter of interest region in advance according to the estimated moving direction and moving speed of the object of interest. The method of claim 5,
The image processor,
The X-ray imaging apparatus performs real-time detection of the object of interest and setting of the region of interest according to a frame rate of the X-ray imaging apparatus. The method of claim 3,
The image processor,
Detect an object of interest from the frame image, set the region of interest based on the location, size, or motion characteristics of the object of interest, obtain information about the set region of interest, and transmit it to the controller,
Information about the region of interest,
An X-ray imaging apparatus that is at least one of a location of the region of interest, a size of the region of interest, and motion characteristics of the region of interest. The method of claim 12,
The filtering unit,
A region-of-interest filter made of a filter material that attenuates X-rays; And
It includes a filter driver for moving the filter of interest,
The control unit,
An X-ray imaging apparatus that controls the filter driver to move the filter of interest to a position corresponding to a position of the non-interested region based on the information on the region of interest. According to claim 2,
The image processor,
Average the frame image and the previous frame image, sum the frame image and the previous frame image, and perform motion-compensated temporal filtering or motion-compensated filtering on the frame image and the previous frame image. X-ray imaging apparatus for performing the image restoration by applying at least one of spatial filtering. The method of claim 14,
The image processor,
An X-ray imaging apparatus performing image restoration on the non-interested region and the region of interest. The method of claim 15,
The image processor,
An X-ray imaging apparatus that selects a type of filtering to be applied to the non-interested region and the region of interest based on the motion characteristics of the object of interest. According to claim 2,
The image processor,
The X-ray imaging apparatus further performs image registration or motion estimation and compensation for an uninterested region in which image restoration is performed by combining the current frame image with the previous frame image. According to claim 2,
The image processor,
The X-ray imaging apparatus further performs an image smoothing algorithm that matches the brightness and contrast of the region of interest and the region of interest with respect to the current frame image in which the image restoration is performed on the region of interest. The method of claim 13,
The control unit,
An X-ray imaging apparatus that sets an X-ray imaging mode based on information on the current frame image, information on an imaging mode, or information on a stage. Setting an X-ray imaging mode according to the size of movement of the object of interest included in the object area;
Irradiating X-rays to the subject area;
Detecting the irradiated X-ray and acquiring a frame image related to the object region,
A method of controlling an X-ray imaging apparatus for irradiating X-rays having a dose less than a region of interest to an uninterested region in the object region. The method of claim 20,
Irradiating the X-ray,
And filtering the X-rays incident on the non-interested region. The method of claim 21,
Irradiating X-rays to the region of interest of the object region;
Detecting the irradiated X-ray, and acquiring a frame image of the object area based on the detected X-ray;
And setting the region of interest using the frame image. The method of claim 22,
Setting the region of interest,
And detecting an object of interest from a current frame image among the frame images, and setting the region of interest based on the location, size, or motion characteristics of the object of interest. The method of claim 23,
Filtering the X-ray,
And moving the region of interest filter that attenuates the irradiated X-ray to a location corresponding to the location of the non-interested region based on information on the region of interest. The method of claim 20,
And setting an X-ray imaging mode based on information on a current frame image, information on an imaging mode, or information on a stage. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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