X-ray diagnostic apparatus, x-ray diagnostic system, and x-ray control method

Abstract

To improve a frame rate of an X-ray image while displaying by keeping a region of interest of an X-ray image still.SOLUTION: An X-ray diagnostic apparatus according to the embodiment includes an image acquisition part, a locus information acquisition part, a specification part, and a control part. The image acquisition part acquires a plurality of X-ray images sequentially obtained at a plurality of cardiac phases. The locus information acquisition part obtains locus information showing a moving locus of a region of interest at the plurality of the cardiac phases from the plurality of the X-ray images. The specification part specifies a plurality of still phases respectively corresponding to the plurality of X-ray images in which a difference of a position of the region of interest for one heart beat is smaller than a threshold value based on the locus information. The control part controls to emit X-rays at each heart beat while using the plurality of the specified still phases as plural timings of X-ray emission.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The embodiments disclosed in this specification and the drawings relate to an X-ray diagnostic apparatus, an X-ray diagnostic system, and an X-ray control method.

Background Art

[0002] In interventional radiology (IVR) of the heart, a technician inserts devices such as a catheter and a guide wire into a patient's body while looking at the X-ray fluoroscopic image of the patient. When electrocardiogram-synchronized fluoroscopy is used at this time, irradiation is performed at a specific cardiac phase in each heartbeat, so that blurring due to heartbeat is suppressed among a plurality of X-ray fluoroscopic images over a plurality of heartbeats, and exposure of the patient is reduced.

[0003] On the other hand, in electrocardiogram-synchronized fluoroscopy, since irradiation is performed at a specific cardiac phase every one cardiac cycle, there is a problem that the frame rate of the collected X-ray fluoroscopic image is lower than that of normal X-ray fluoroscopy, and there is little timing at which the position of the device can be confirmed. As a result, since the technician needs to operate the device carefully, there is a possibility that the operation speed will decrease.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to improve the frame rate of the X-ray image while displaying the region of interest of the X-ray image stationary. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problems. It is also possible to position the problems corresponding to the respective effects of the respective configurations shown in the respective embodiments described later as other problems.

Means for Solving the Problem

[0006] The X-ray diagnostic apparatus according to the embodiment includes an image acquisition unit, a trajectory information acquisition unit, a specifying unit, and a control unit. The image acquisition unit acquires a plurality of X-ray images sequentially obtained at a plurality of cardiac phases. The trajectory information acquisition unit acquires trajectory information indicating the trajectory of the movement of the region of interest in a plurality of cardiac phases from the plurality of X-ray images. The specifying unit specifies a plurality of stationary phases corresponding to the plurality of X-ray images in which the difference in the position of the region of interest in one heartbeat is smaller than a threshold value based on the trajectory information. The control unit controls to irradiate X-rays using the specified plurality of stationary phases as a plurality of X-ray irradiation timings in each heartbeat.

Brief Description of the Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of an X-ray diagnostic apparatus, an X-ray diagnostic system, and an X-ray control method will be described in detail with reference to the drawings.

[0009] 〔First Embodiment〕 FIG. 1 is a schematic diagram showing the configuration of an X-ray diagnostic system 2 including an X-ray diagnostic apparatus 1 according to the first embodiment. FIG. 2 is a perspective view showing a part of the appearance of the X-ray diagnostic system 2 including the X-ray diagnostic apparatus 1 according to the first embodiment.

[0010] Here, the X-ray diagnostic apparatus 1 according to the present embodiment means an apparatus that includes an X-ray tube, controls its output, and can perform imaging. For example, the X-ray diagnostic apparatus 1 according to the present embodiment includes a simple X-ray imaging apparatus (e.g., an X-ray radiography apparatus), a cardiovascular X-ray imaging apparatus (e.g., an X-ray angiography apparatus), a gastrointestinal X-ray imaging apparatus (e.g., an X-ray TV apparatus), and a breast X-ray imaging apparatus (e.g., a mammography apparatus). Hereinafter, the case where the X-ray diagnostic apparatus 1 according to the present embodiment is a cardiovascular X-ray imaging apparatus will be described, but it is not limited to that case.

[0011] As shown in FIGS. 1 and 2, the X-ray diagnostic system 2 includes the X-ray diagnostic apparatus 1 according to the first embodiment and an electrocardiograph 9. The X-ray diagnostic apparatus 1 according to the first embodiment can support imaging, mainly IVR (Interventional Radiology) procedures using X-ray fluoroscopy. The IVR procedure is a treatment mainly using a catheter that is performed during imaging. In the IVR procedure, the X-ray diagnostic apparatus 1 sequentially (in real time) generates a plurality of frames of X-ray fluoroscopy images in time series during X-ray fluoroscopy and sequentially displays them.

[0012] The X-ray diagnostic apparatus 1 includes an imaging unit 5 and a medical image processing apparatus 6. The imaging unit 5 is provided with an X-ray generation unit 10, an X-ray detection unit 20, a C-arm 30, a bed apparatus 40, a high voltage generation unit 50, a mechanism control circuit 60, a mechanism unit 70, and an image processing unit 80. On the other hand, the medical image processing apparatus 6 is provided with a display 90, an input interface 100, and a system control unit 110.

[0013] The imaging unit 5 captures an image of the patient P, who is the subject, under the control of the system control unit 110 to obtain an X-ray image of the patient P. For example, the imaging unit 5 performs only X-ray fluoroscopy on the patient P to obtain a plurality of frames of X-ray fluoroscopy images. Further, the imaging unit 5 performs X-ray fluoroscopy and X-ray imaging on the patient P to obtain a plurality of frames of X-ray fluoroscopy images and one or more X-ray imaging images. Here, X-ray imaging is imaging for the purpose of generating an X-ray image used for diagnosis. X-ray fluoroscopy is imaging for the purpose of generating a plurality of frames of X-ray images showing the process of the IVR technique while reducing the dose compared to X-ray imaging. Further, X-ray fluoroscopy is roughly classified into continuous fluoroscopy and pulse fluoroscopy. Pulse fluoroscopy means a fluoroscopy method in which, unlike continuous fluoroscopy, X-rays are intermittently irradiated by an intermittent rectangular wave. According to pulse fluoroscopy, although the continuity (frame rate) of the frames of the X-ray fluoroscopy image is slightly inferior to that of continuous fluoroscopy, the radiation dose to the patient can be suppressed.

[0014] The X-ray generation unit 10 of the imaging unit 5 includes an X-ray tube 11 and an X-ray irradiation field diaphragm 12. The X-ray tube 11 irradiates the patient P with X-rays according to the control of the system control unit 110. The X-ray tube 11 is a vacuum tube that generates X-rays, and thermoelectrons emitted from the cathode (filament) are accelerated by a high voltage applied between the anode and the cathode and collide with the tungsten anode to generate X-rays.

[0015] The X-ray irradiation field diaphragm 12 slides the diaphragm according to the control of the system control unit 110 to form an X-ray cone (cone beam) for the X-rays irradiated from the X-ray tube 11. The X-ray irradiation field diaphragm 12 is located between the X-ray tube 11 and the patient P, and narrows down the X-ray beam irradiated from the X-ray tube 11 so as to be selectively irradiated to the region of interest of the patient P.

[0016] The X-ray detection unit 20 two-dimensionally detects the X-rays that have passed through the patient P under the control of the system control unit 110. The X-ray detection unit 20 includes a flat panel detector (FPD) 21, a gate driver 22, and an image data generation unit 23.

[0017] The X-ray detection unit 20 has a direct conversion method that directly converts X-rays into electric charges and an indirect conversion method that converts them into light first and then into electric charges. In the embodiment, the former is taken as an example for explanation, but the latter may also be used.

[0018] The flat panel detector 21 is an example of an X-ray detector configured by two-dimensionally arranging minute elements in the column direction and the line direction. Each element of the flat panel detector 21 includes an X-ray detection element, a photoelectric film, a charge storage capacitor, and a TFT (thin film transistor). The X-ray detection element senses X-rays. The photoelectric film generates electric charges according to the incident X-ray dose. The charge storage capacitor stores the electric charges generated in the photoelectric film. The TFT reads out the electric charges stored in the charge storage capacitor as raw data of an X-ray transmission image (X-ray fluoroscopic image or X-ray radiographic image) at a predetermined timing. Note that the raw data of the X-ray transmission image may be converted using the NDD (Non Dosimeter Dosimetry) method to generate surface dose data of the X-ray transmission image.

[0019] The gate driver 22 is installed to extract electric charges from the flat panel detector 21. The image data generation unit 23 generates image data of the X-ray transmission image based on the raw data (or surface dose data) of the X-ray transmission image output from the X-ray detection unit 20.

[0020] The image data generation unit 23 includes a charge-voltage conversion circuit, an A / D (Analog to Digital) conversion circuit, and a parallel-serial conversion circuit (all not shown in the figure). The charge-voltage conversion circuit converts the charge read from the flat panel detector 21 into a voltage. The A / D conversion circuit converts the output of the charge-voltage conversion circuit into a digital signal. The parallel-serial conversion circuit converts the digitally converted image data read in parallel in line units from the flat panel detector 21 into a serial signal.

[0021] In addition, in the X-ray diagnostic apparatus 1, in order to perform X-ray automatic exposure control, a photopic pickup (for example, a fluorescence collection type fiber-shaped detector) FP may be incorporated in front of the flat panel detector 21. In the case of an X-ray examination using X-rays for fluoroscopy, the flat panel detector 21 detects the X-rays for fluoroscopy, and based on the detection signal, a feedback loop is configured so that the luminance of the display 90 becomes constant. Alternatively, a feedback loop may be configured so that the average value of the pixel signals (or video signals) visualized by the flat panel detector 21 becomes constant.

[0022] Also, in FIGS. 1 and 2, the imaging system of the C-arm structure included in the X-ray diagnostic apparatus 1 shows the case where the X-ray generation unit 10 is located below the top plate 42, i.e., an under-table type. However, it is not limited to that case, and it may be an over-table type where the X-ray generation unit 10 is located above the top plate 42.

[0023] The C-arm 30 integrally holds the X-ray generation unit 10 and the X-ray detection unit 20. Note that the arm that integrally holds the X-ray generation unit 10 and the X-ray detection unit 20 is not limited to the so-called C-arm having a "C" shape. For example, the arm that integrally holds the X-ray generation unit 10 and the X-ray detection unit 20 may be a so-called Ω-arm having an "Ω" shape.

[0024] The bed apparatus 40 includes a bed main body 41 and a top plate 42. The bed main body 41 holds the top plate 42 and includes each power unit that operates the top plate 42. The top plate 42 places the patient P thereon. Here, the short side direction of the top plate 42 is defined as the X-axis direction, the vertical direction is defined as the Y-axis direction, and the long side direction of the top plate 42 is defined as the Z-axis direction. The X-axis, Y-axis, and Z-axis are orthogonal to each other.

[0025] The high voltage generation unit 50 supplies high voltage power to the X-ray tube 11 of the X-ray generation unit 10 under the control of the system control unit 110.

[0026] The mechanism control circuit 60 is a power circuit that supplies electricity to the mechanism unit 70 under the control of the system control unit 110 to rotate the C-arm 30 or slide the top plate 42.

[0027] The mechanism unit 70 includes a C-arm rotation mechanism 71 and a top plate slide mechanism 72. The C-arm rotation mechanism 71 operates each power unit constituting the C-arm rotation mechanism 71 under the control of the system control unit 110 via the mechanism control circuit 60. Thereby, the C-arm rotation mechanism 71 rotates the C-arm 30 that holds the X-ray generation unit 10 and the X-ray detection unit 20 in the arc direction of the C-arm 30 or rotates about the fulcrum of the C-arm 30.

[0028] The rotation of the C-arm 30 in the arc direction corresponds to the rotation in the CRA (Cranial View) direction and the rotation in the CAU (Caudal View) direction. The rotation of the C-arm 30 about the fulcrum center corresponds to the rotation in the LAO (Left Anterior Oblique View) direction and the rotation in the RAO (Right Anterior Oblique View) direction. Note that the configuration may be such that the rotation of the C-arm 30 in the arc direction corresponds to the rotation in the LAO direction and the rotation in the RAO direction, and the rotation of the C-arm 30 about the fulcrum center corresponds to the rotation in the CRA direction and the rotation in the CAU direction.

[0029] The top plate slide mechanism 72 operates each power unit that constitutes the bed body 41 holding the top plate 42 under the control of the system control unit 110 via the mechanism control circuit 60. Thereby, the top plate slide mechanism 72 can slide the bed body 41 in the left - right direction (X - axis direction), vertical direction (Y - axis direction), and the body axis direction (Z - axis direction) of the patient P.

[0030] The image processing unit 80 includes an image memory 81 and an image arithmetic circuit 82. The image memory 81 stores the image data sequentially output from the image data generation unit 23 in line units or frame units under the control of the system control unit 110.

[0031] The image arithmetic circuit 82 performs image processing on the image data stored in the image memory 81 under the control of the system control unit 110, and stores the image data after the image processing in the image memory 81. Examples of the image processing include enlargement / toning / spatial filtering processing of X - ray transmission image data, minimum / maximum value trace processing of image data accumulated in time series, subtraction processing, addition processing for removing noise, etc.

[0032] As shown in FIGS. 1 and 2, the electrocardiograph 9 may be attached to the arm or the like of the patient P. In that case, the electrocardiograph 9 transmits data including the electrocardiogram waveform of the patient P to the processing circuit 111 of the medical image processing apparatus 6.

[0033] The display 90 of the medical image processing apparatus 6 synthesizes and displays text and graphic information such as X - ray irradiation conditions provided from the system control unit 110 on the image data of the X - ray transmission image processed by the image processing unit 80 under the control of the system control unit 110. For example, the display 90 is a liquid crystal display, a plasma display panel, an organic EL (Electro Luminescence) panel, a CRT (Cathode Ray Tube) display, an OLED (Organic Light Emitting Diode) display, etc. Note that the display 90 is an example of a display unit.

[0034] The input interface 100 includes an input medical device that can be operated by an operator such as a technician, and an input circuit that inputs a signal from the input medical device. The input medical device is realized by a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad that performs an input operation by touching an operation surface, a touch screen in which a display screen and a touch pad are integrated, a non-contact input circuit using an optical sensor, a voice input circuit, and the like. When the input medical device receives an input operation from an operator such as a surgeon, the input circuit generates an electrical signal corresponding to the input operation and outputs it to the processing circuit 111.

[0035] The input interface 100 transmits, according to an operation by an operator, signals corresponding to patient information of the patient P and optimal X-ray irradiation conditions and the like for the observation target site of the patient P to the system control unit 110. Examples of the patient information include the examination site, the examination method, the physique (body thickness), the past diagnosis history, and the like. Note that the input interface 100 is an example of an input unit.

[0036] The system control unit 110 includes a processing circuit 111 and a main memory 112. The system control unit 110 controls the entire X-ray diagnostic apparatus 1 according to an instruction from an operator input from the input interface 100.

[0037] The processing circuit 111 means a processing circuit such as an application-specific integrated circuit (ASIC) and a programmable logic medical device, in addition to a dedicated or general-purpose CPU (Central Processing Unit) or MPU (Micro Processor Unit). Examples of the programmable logic medical device include circuits such as a simple programmable logic medical device (SPLD), a complex programmable logic medical device (CPLD), and a field programmable gate array (FPGA). The processing circuit 111 realizes the functions described later by reading and executing a program stored in the main memory 112 or directly incorporated in the processing circuit 111. Note that the processing circuit 111 is an example of a display control unit and a control unit. Also, the program is an example of a medical image processing program.

[0038] Further, the processing circuit 111 may be configured by a single processing circuit or a combination of a plurality of independent processing circuits. In the latter case, a plurality of main memories 112 may each store a program corresponding to the functions of the plurality of processing circuits, or one main memory 112 may store a program corresponding to the functions of the plurality of processing circuits.

[0039] The main memory 112 is composed of semiconductor memory elements such as RAM (Random Access Memory) and flash memory, hard disks, optical disks, etc. The main memory 112 may be provided with portable media such as a USB (Universal Serial bus) memory and a DVD (Digital Video Disk). The main memory 112 stores various processing programs (including an OS (Operating System) in addition to application programs) used in the processing circuit 111 and data necessary for program execution. Further, the OS can include a GUI (Graphic User Interface) that makes extensive use of graphics for displaying information on the display 90 to the operator and enables basic operations to be performed by the input interface 100.

[0040] Subsequently, the configuration and functions of the X-ray diagnostic apparatus 1 will be described with reference to FIG. 3. FIG. 3 is a block diagram showing the configuration and functions of the X-ray diagnostic apparatus 1 according to the embodiment.

[0041] By executing a computer program stored in the main memory 112 or directly incorporated in the processing circuit 111 by the processing circuit 111, the X-ray diagnostic apparatus 1 realizes a first image acquisition function F1, a trajectory information acquisition function F2, a stationary phase identification function F3, a second image acquisition function F4, a display control function F5, and a storage control function F6. Note that all or part of the functions F1 to F6 are not limited to the case of functioning by executing a computer program, and may be the case of functioning by a circuit such as an ASIC provided in the X-ray diagnostic apparatus 1.

[0042] The first image acquisition function F1 includes a function of controlling the operation of the imaging unit 5 to perform imaging of the patient P and acquiring a plurality of X-ray images (hereinafter referred to as "first X-ray images") corresponding to each of a plurality of cardiac phases, and a function of acquiring (reading out) the plurality of first X-ray images stored in the main memory 112. For example, the plurality of first X-ray images are a plurality of fluoroscopic X-ray images acquired by fluoroscopic imaging.

[0043] The trajectory information acquisition function F2 includes a function of setting a region of interest based on a plurality of first X-ray images acquired by the first image acquisition function F1, and a function of acquiring trajectory information indicating the trajectory of the movement of the region of interest in a plurality of cardiac phases from the plurality of first X-ray images.

[0044] The static phase identification function F3 includes a function of identifying a plurality of static phases corresponding to a plurality of first X-ray images in which the difference in the position of the region of interest within one heartbeat is smaller than a threshold value based on the trajectory information. The plurality of static phases are timings at which the region of interest can be displayed in a seemingly stationary state. Each static phase is an example of the timing of X-ray irradiation for acquiring a second X-ray image described later.

[0045] The second image acquisition function F4 controls the operation of the imaging unit 5 so as to irradiate X-rays with a plurality of static phases within each heartbeat as a plurality of X-ray irradiation timings within each heartbeat, thereby causing the patient P to be imaged and acquiring a plurality of X-ray images (hereinafter referred to as "second X-ray images") within each heartbeat. The second image acquisition function F4 also includes a function of acquiring (reading out) the plurality of second X-ray images stored in the main memory 112. The plurality of second X-ray images are a plurality of fluoroscopic X-ray images acquired by fluoroscopic imaging, and are acquired at intervals sparser than those of the plurality of first X-ray images. For example, there are two second X-ray images per heartbeat.

[0046] The display control function F5 includes a function of displaying a plurality of first X-ray images acquired by the first image acquisition function F1 on the display 90, a function of displaying second X-ray images corresponding to the plurality of static phases acquired by the X-ray irradiation of the second image acquisition function F4 on the display 90, and a function of superimposing and displaying on the display 90 the images of the plurality of regions of interest extracted from the plurality of second X-ray images respectively after aligning them with a predetermined second X-ray image among the plurality of second X-ray images.

[0047] The storage control function F6 includes a function of storing a plurality of first X-ray images, a plurality of second X-ray images, and other necessary information in the main memory 112.

[0048] Here, the blood vessels targeted for medical image processing according to the embodiment will be described. Generally, the blood vessels in the head, chest, abdomen, and lower limbs where vascular treatment is performed are targeted. For the chest, abdomen, etc. with large movements due to breathing, pulse, heartbeat, etc., by combining technologies such as synchronous imaging with the electrocardiogram waveform of the patient P (ECG synchronization) and image processing technologies that make the devices depicted in the X-ray image appear as if they were virtually stationary, it is assumed that real-time X-ray images in which the position of the target blood vessels does not move can be obtained.

[0049] In synchronous imaging with the electrocardiogram waveform, the X-ray diagnostic apparatus irradiates the patient P with X-rays at a specific cardiac phase in synchronization with the electrocardiogram waveform (Electrocardiogram: ECG) of the subject. Here, there are periods when the movement of the heart is relatively small, such as the end-diastolic phase of the ventricle in the heart. If X-ray irradiation is performed during this period, X-ray images with little motion blur can be collected. Thereby, blood vessels that are not moving can be observed. Also, in the image processing technology that makes the devices depicted in the X-ray image appear as if they were virtually stationary, for example, two-point balloon markers provided on a stent for expanding the blood vessel from the inside are detected on the X-ray image, and image deformation and alignment processing are performed so that the positions of the markers in the sequentially collected X-ray images are approximately the same as those in the past images. Thereby, the device equipped with the marker appears to be virtually stopped. Also, for example, there is a technique of adding and averaging a plurality of X-ray images corrected so that the positions of the two-point markers are the same, thereby emphasizing and displaying the device. Thereby, the visibility of the stent can be improved in real time.

[0050] FIG. 4 is a flowchart showing the processing of the X-ray diagnostic apparatus 1 according to the first embodiment. In the processes of steps S1 to S6, the X-ray diagnostic apparatus 1 acquires a plurality of first X-ray images corresponding to a plurality of cardiac phases in advance, and identifies a plurality of stationary phases (for example, two stationary phases) from the plurality of first X-ray images. Then, in the process of step S7, the X-ray diagnostic apparatus 1 irradiates X-rays at a plurality of stationary phases within a predetermined heartbeat to perform imaging (for example, two X-ray irradiations corresponding to two cardiac phases within one heartbeat). Further, in the process of step S8, the X-ray diagnostic apparatus 1 causes the display 90 to display a plurality of stationary images respectively acquired at the plurality of stationary phases. In the process of step S9, the X-ray diagnostic apparatus 1 determines whether to perform imaging in the next heartbeat. If the determination in step S9 is YES, that is, if it is determined to perform imaging in the next heartbeat, the X-ray diagnostic apparatus 1 returns to step S7 and irradiates X-rays at a plurality of stationary phases within the next heartbeat to perform imaging. On the other hand, if the determination in step S9 is NO, that is, if it is determined not to perform imaging in the next heartbeat, the X-ray diagnostic apparatus 1 ends the operation. Each of the processes from step S1 to S9 is executed by the processing circuit 111 of the medical image processing apparatus 6. Hereinafter, the processing of the X-ray diagnostic apparatus 1 will be described.

[0051] In step S1, the first image acquisition function F1 of the processing circuit 111 acquires a plurality of first X-ray images obtained at a predetermined frame rate as learning data for identifying a plurality of stationary phases. The first image acquisition function F1 acquires, for example, a plurality of first X-ray images from the start of the most recent surgery to the present as learning data. The first X-ray image is, for example, a video of at least one heartbeat. In this specification, the timing at which the first X-ray image is actually taken during the time of one heartbeat is referred to as a phase. Note that the X-ray diagnostic apparatus 1 may perform fluoroscopic imaging for learning separately from the surgery to acquire the first X-ray image. At this time, the display control function F5 causes the display 90 to display the plurality of first X-ray images acquired by the first image acquisition function F1.

[0052] In step S2, the trajectory information acquisition function F2 of the processing circuit 111 sets a region of interest for the first X-ray image at the reference time phase (reference time) among the plurality of first X-ray images acquired as learning data. The region of interest is the region that the technician wants to display in a stationary state on the display 90. The region of interest is, for example, a region of interest such as a vascular bifurcation or an occlusion site, or a region including the tip of a medical device being inserted, such as a catheter or a guide wire.

[0053] When setting the region of interest, the technician may manually specify the range for the first X-ray image displayed on the display 90, or may automatically set the range using an existing region extraction process or the like. Also, the position of the set region of interest may be automatically updated as the procedure progresses. FIG. 5 is a diagram showing an example of the region of interest AI in the first X-ray image (X-ray fluoroscopic image) according to the first embodiment. As shown in FIG. 5, for example, when the target of the region of interest AI is a guide wire, the trajectory information acquisition function F2 detects the position of the tip of the guide wire and continues to update the position of the region of interest AI in the first X-ray image so that the tip is positioned at the center of the region of interest AI.

[0054] In step S3 of FIG. 4, the trajectory information acquisition function F2 of the processing circuit 111 identifies the trajectory of the region of interest AI that moves due to the heartbeat. The trajectory of the region of interest AI is, for example, obtained by setting a point, the center of gravity, or other point around the region of interest AI as a representative point of the region of interest AI and connecting the representative points between adjacent time phases. Usually, the trajectory of the region of interest AI has a closed-loop shape.

[0055] After the trajectory information acquisition function F2 identifies the position of the representative point of the region of interest AI at an arbitrary phase within one cardiac cycle, it aligns the region of interest AI with the regions of interest AI at other phases within one cardiac cycle using existing methods. If the displacement amounts of the X coordinate and the Y coordinate by which the region of interest AI has moved during the alignment are known, the positions (coordinates) of the respective representative points that constitute the trajectory can be calculated. Examples of existing alignment methods include, for example, template matching and optical flow after extracting a group of feature points of the region of interest AI. The group of feature points will be described later.

[0056] FIG. 6(a) is a diagram showing an example of a plurality of first X-ray images within one cardiac cycle according to the first embodiment. The position of the region of interest AI is different in each first X-ray image for each phase. The position of the region of interest AI moves moment by moment due to cardiac motion.

[0057] FIG. 6(b) is a diagram showing an example of the trajectory of the region of interest AI according to the first embodiment. As shown in FIG. 6(b), the trajectories of the region of interest AI include a gourd shape, an intersecting shape, and an elliptical shape. Note that the trajectory of the region of interest AI is not limited to these. In the example of FIG. 6(b), the representative point of the region of interest AI is the center of gravity of the rectangle formed by the region of interest AI.

[0058] In step S4 of FIG. 4, the trajectory information acquisition function F2 of the processing circuit 111 calculates the period of the region of interest AI based on the trajectory of the region of interest AI specified in step S3. A specific example of the period calculation will be described below.

[0059] FIG. 7(a) is a diagram showing an example of the trajectory of the region of interest AI according to the first embodiment. For example, when the representative point of the region of interest AI traces a trajectory as shown in FIG. 7(a), the trajectory information acquisition function F2 may measure the time from when the representative point of the region of interest AI passes through an arbitrary point A on the trajectory until it passes through the same point A again, and obtain the measured time as the period.

[0060] FIG. 7(b) is a graph showing the temporal change of the displacement of the representative point of the region of interest AI according to the first embodiment. The horizontal axis of the graph represents the elapsed time (seconds). The vertical axis of the graph represents the X coordinate of the representative point. For example, when the trajectory of the region of interest AI is represented in the two-dimensional space (X coordinate, Y coordinate) on the first X-ray image, when the X coordinate changes as shown in FIG. 7(b), the trajectory information acquisition function F2 may obtain the average value of the elapsed time T between the minimum value (local minimum value) on the graph and the adjacent minimum value as a period. Note that since the vertical axis of the graph may be a value that changes periodically, it may represent the Y coordinate of the representative point.

[0061] In step S5 of FIG. 4, the stationary phase specifying function F3 of the processing circuit 111 calculates the evaluation value D of the region of interest AI at each phase. The stationary phase specifying function F3 extracts, for example, a feature point group from each region of interest AI and calculates an evaluation value indicating the degree of variation between the feature point groups. The feature point group is a collection of a plurality of feature points (for example, a plurality of point groups constituting the curves AB in FIGS. 8(b) and 8(c)) and is an example of a figure that is a feature of the region of interest. Note that the trajectory is obtained by sequentially connecting representative points (not necessarily feature points) set in the region of interest AI according to the phase.

[0062] FIG. 8(a) shows two points N i , N j on the trajectory of the region of interest AI according to the first embodiment. The evaluation value D(N i , N j ) is an index for evaluating whether the region of interest AI extracted from the first X-ray image at the timing of passing through these points can be displayed in an apparently stationary state on the trajectory of the region of interest AI. In other words, the evaluation value D(N i , N j ) is an index indicating how much difference there is in appearance between the respective regions of interest AI in the X-ray fluoroscopic images corresponding to two different points N i , N j on the trajectory of the region of interest AI. That is, the evaluation value D(N i , N j i , N jThe smaller i N j is, the smaller the visual difference of the region of interest AI in the first X-ray image corresponding to N i means. Here, i and j are phases corresponding to the X-ray irradiation timing, and represent different phases from each other. When the representative point of the region of interest AI is at phase i, it is drawn at the coordinates of point N j , and when the representative point of the region of interest AI is at phase j, it is drawn at the coordinates of point N

[0063] The evaluation value D(N i N j ) is defined based on, for example, the position and shape of the entire region of interest AI, the positions of the characteristic point group constituting the region of interest AI, and the like. For example, when the region of interest AI is represented by a curve AB connecting point A and point B like a guide wire often used in IVR procedures, the evaluation value D(N i N j ) is calculated based on the positions of each point on the curve AB and the positional relationship between each point. Hereinafter, a calculation example of the evaluation value D(N i N j ) is shown.

[0064] (1) Difference in shape within the region of interest AI The stationary phase specifying function F3 may define the evaluation value D(N i N j ) based on the difference in the shape of the curve AB within the region of interest AI. FIG. 8(b) is a diagram showing an example of the movement of the region of interest AI according to the first embodiment. As shown in FIG. 8(b), the stationary phase specifying function F3 is such that when the curve AB within the region of interest AI at the point N i on the trajectory that is a candidate for the X-ray irradiation timing becomes the curve A'B' at the point N j on the trajectory, the evaluation value D(N i N j ) is obtained from the difference (distance value) between the coordinate values of each point on the curve obtained by aligning the curve AB with the curve A'B' and the coordinate values of each point on the curve A'B'. For alignment, the curve AB is subjected to editing operations of translation, rotation, enlargement, or reduction.

[0065] Let the points on the curve AB be t (A ≤ t ≤ B), and the point N on the trajectoryi , N j The position (X coordinate, Y coordinate) of point t in N is C i (t), C j (t), C i (t) is C j (t) The position aligned with C’ i,j (t) When taking it as, the evaluation value D(N i , N j ) is calculated by the following formula 1.

[0066]

Equation

[0067] (2) Difference in curvature within the region of interest AI The stationary phase identification function F3 defines the evaluation value D(N i , N j ) based on the difference in curvature of curve AB within the region of interest AI. Specifically, the stationary phase identification function F3 is such that when curve AB within the region of interest AI at point N i on the orbit becomes curve A’B’ at point N j on the orbit, the evaluation value D(N i , N j ) is obtained from the difference in curvature between each point on curve AB and each point on curve A’B’.

[0068] Let the point on curve AB within the region of interest AI be t (A ≤ t ≤ B), and the curvature at the position (X coordinate, Y coordinate) of point t on curves AB and A’B’ at points N i , N j on the orbit be r i (t), r j (t). When taking it as, the evaluation value D(N i , N j ) is calculated by the following formula 2.

[0069] [Number] The integration target on the right side of Equation 2 is the difference in curvature at the point t on curve AB and the point on curve A'B' corresponding to point t.

[0070] (3) Difference in position and shape within the region of interest AI The stationary phase identification function F3 defines the evaluation value D(N i , N j ) based on the difference in position and shape of curve AB within the region of interest AI. FIG. 8(c) is a diagram showing an example of the movement of the region of interest AI according to the first embodiment. As shown in FIG. 8(c), the stationary phase identification function F3 is such that when curve AB within the region of interest AI at point N i on the orbit becomes curve A'B' at point N j on the orbit, the evaluation value D(N i , N j ) is obtained from the coordinate difference (distance) between each point on curve AB and each point on curve A'B'.

[0071] Let the point on curve AB be t (A ≤ t ≤ B), and the positions (X coordinate, Y coordinate) of point t at points N i , N j on the orbit be C i (t), C j (t). Then, the evaluation value D(N i , N j ) is calculated by the following Equation 3.

[0072] [Number] The integration target on the right side of Equation 3 is the distance between the point t on curve AB and the point on curve A'B' corresponding to point t.

[0073] (4) Nearest point or intersection point within the region of interest AI FIG. 8(d) is a diagram showing an example of the trajectory of the region of interest AI according to the first embodiment. When the trajectory of the region of interest AI is close to a certain extent on the first X-ray image, or when the trajectory intersects, the stationary phase specifying function F3 may specify two points (a plurality of stationary phases respectively corresponding to a plurality of first X-ray images) as the X-ray irradiation timing. The two points when the trajectories are close to a certain extent refer to two points where the distance between them is equal to or less than a predetermined threshold value in the trajectory viewed in plan view. The two points when the trajectories intersect refer to two points where the distance between them is 0 in the trajectory viewed in plan view. Note that the perspective angle may be adjusted so that the distance between two points on the trajectory of the region of interest AI is equal to or less than a predetermined threshold value or 0 on the first X-ray image.

[0074] (5) Others The stationary phase specifying function F3 may calculate an evaluation value between curves in the region of interest AI at points on the trajectory using a general distance function (such as Hausdorff distance, Frechet distance, etc.) that represents the shape difference.

[0075] In step S6 of FIG. 4, the stationary phase specifying function F3 specifies a plurality of stationary phases at which the region of interest AI can apparently be displayed as stationary as the X-ray irradiation timing. The stationary phase specifying function F3 extracts a plurality of regions of interest based on the evaluation value calculated in step 5, and specifies a plurality of phases of a plurality of first X-ray images corresponding to the plurality of regions of interest as the stationary phases. In this specification, the phase indicates the position within the range delimited by the period T when the trajectory of the region of interest AI moves so as to repeat with the period T.

[0076] Specifically, the stationary phase specifying function F3 specifies the stationary phase based on the evaluation value D(N i , N j ) between points on the trajectory calculated in step 5. For example, when the stationary phase specifying function F3 sets i and j such that the evaluation value D(N i , N j ) is the smallest in the period T as m and n respectively, the points N m , N n on the trajectory are obtained as the stationary phases.

[0077] Note that when the stationary phase identification function F3 identifies the stationary phase, after setting a threshold value Θ that serves as a criterion for obtaining candidates for the stationary phase in advance, the evaluation value D(N i , N j ) may obtain a group of combinations of i and j such that it is less than or equal to the threshold value Θ. Then, the stationary phase identification function F3 may extract i with the largest number of combinations included in the combination group as the reference phase k, and obtain the combination of k and j as the stationary phase group.

[0078] Depending on the X-ray irradiation timing, which is the identified stationary phase, the interval of X-ray irradiation may not be uniform. In such a case, the stationary phase identification function F3 may add a condition for making the interval of X-ray irradiation uniform to the conditions for calculating the X-ray irradiation timing. For example, when the stationary phase identification function F3 sets the time required for one orbit (one heartbeat time) as T and the number of X-ray irradiation timings to be obtained as N, it may add a condition that "the time difference between X-ray irradiation timings is T / N".

[0079] FIG. 9 is a graph for explaining the X-ray irradiation timing according to the first embodiment. FIG. 9(a) shows an example where the interval of X-ray irradiation timing is not uniform. FIG. 9(b) shows an example where the interval of X-ray irradiation timing is uniform. The horizontal axis of the graph indicates the time when X-ray irradiation is performed. The vertical axis of the graph indicates the displacement of the region of interest AI. The graph shows how the region of interest AI is periodically displaced.

[0080] As shown in FIG. 9(a), when the X-ray irradiation timing is set at the point where the displacement of the region of interest AI is Q1, the imaging intervals within one heartbeat time T are T1 and T2 (T1≠T2), which are non-uniform. On the other hand, as shown in FIG. 9(b), when the X-ray irradiation timing is set at the point where the displacement of the region of interest AI is Q2, the imaging intervals within one heartbeat time T are T3 and T4 (T3 = T4), which are uniform.

[0081] According to the above, the static phase identification function F3 may identify the plurality of static phases such that the time difference between the plurality of static phases is equal to or greater than a predetermined value. The predetermined value may be a value obtained by dividing the time of one heartbeat by the desired number of static phases.

[0082] In step S7 of FIG. 4, the second image acquisition function F4 of the processing circuit 111 controls the X-ray generator 10 to perform X-ray fluoroscopic imaging at the static phase identified in step 6. That is, the second image acquisition function F4 controls the X-ray generator 10 to perform X-ray fluoroscopic imaging while synchronizing the identified plurality of static phases with the irradiation timing.

[0083] Synchronization between the static phase and the X-ray irradiation timing may be achieved, for example, by associating each static phase in the cycle of the trajectory of the region of interest AI with a predetermined cardiac phase when the static phase identification function F3 identifies the static phase. That is, after associating and recording the static phase with the predetermined cardiac phase, X-ray fluoroscopic imaging may be performed in accordance with the associated predetermined cardiac phase. The predetermined cardiac phase may be, for example, a cardiac phase with little variation in heartbeat (i.e., the timing when the heart is calm).

[0084] In other words, the second image acquisition function F4 acquires an electrocardiogram waveform from the electrocardiograph 9, identifies a plurality of cardiac phases in which the variation width of the electrocardiogram waveform is smaller than a threshold value, and controls to irradiate X-rays at a plurality of irradiation timings with cardiac phases close to each static phase (each of the plurality of static phases identified in step S6) among the identified plurality of cardiac phases in each heartbeat.

[0085] Also, as a method for synchronizing the static phase and the X-ray irradiation timing, first, continuous fluoroscopy may be performed once to determine which phase of the cycle of the trajectory of the region of interest AI the X-ray irradiation timing of each frame corresponds to. Next, the static phase identification function F3 may identify the static phase to be the X-ray irradiation timing from among the obtained phases. Then, the second image acquisition function F4 may control to perform X-ray fluoroscopic imaging in accordance with the identified static phase.

[0086] The second image acquisition function F4 may be controlled to limit the imaging range and dose at some X-ray irradiation timings during fluoroscopic imaging. That is, in order to display only the region of interest AI that is important to the user in a seemingly stationary state, only the region of interest AI in the fluoroscopic X-ray image is updated, so dose suppression may be performed on parts other than the region of interest AI. For example, the second image acquisition function F4 performs imaging within a normal range at a certain X-ray irradiation timing, but at other X-ray irradiation timings, it performs imaging with the imaging range restricted, and suppresses the dose by generating a composite image obtained by combining the X-ray image within the imaging range and the X-ray image (LIH: Last Image Hold) collected last outside the imaging range. Alternatively, the second image acquisition function F4 may be controlled to perform fluoroscopic imaging only at the first stationary phase within a normal range, and thereafter, to suppress the dose by restricting the imaging range.

[0087] Furthermore, the second image acquisition function F4 may be controlled to perform imaging not only at the stationary phase but also at phases near the stationary phase in consideration of the timing error during imaging. The vicinity of the stationary phase is a margin for absorbing the blur because the heart does not move exactly periodically. For example, the second image acquisition function F4 may be controlled to capture a total of about 3 frames including the phases before and after the stationary phase. Also, the second image acquisition function F4 may adjust the width of the vicinity according to the specifications of the imaging unit 5 and the movement of the patient P's heart.

[0088] Then, the display control function F5 may cause the display 90 to display second X-ray images respectively corresponding to a plurality of stationary phases obtained by the X-ray irradiation of the second image acquisition function F4.

[0089] In step S8 of FIG. 4, the display control function F5 causes the display 90 to display the region of interest AI in a seemingly stationary state based on a plurality of second X-ray images obtained by X-ray irradiation at the stationary phase in step S7. For example, when the position of the region of interest AI is different between X-ray irradiation timings, the display control function F5 may cause the display 90 to display the region of interest AI in a seemingly stationary state by shifting the display position of the second X-ray image by the difference in the position of the region of interest AI. The display control function F5 may shift and display the entire imaging range. The display control function F5 may update only the display range of the region of interest AI in the second X-ray image at any time with the image of the region of interest AI in the stationary phase.

[0090] FIG. 10 is a diagram showing an example of updating only the image of the region of interest AI in the second X-ray image according to the first embodiment. Specifically, FIG. 10 shows an operation example of a program in which the region of interest AI is set in the first X-ray image at the reference phase, the position where the region of interest AI exists in the first X-ray images at other phases is searched for, and the region of interest AI is updated and displayed at the X-ray irradiation timing in the second X-ray image. Note that, in the second X-ray image, the region other than the region of interest AI is displayed as the last collected X-ray image as it is.

[0091] FIG. 10(a) shows a state in which the region of interest AI is set in the first X-ray image at the reference phase. FIG. 10(b) shows a state in which the feature point group FPG is extracted from the region of interest AI at the reference phase. FIG. 10(c) shows a state in which the region of interest AI is set and the feature point group FPG is extracted at each phase. Note that the rectangular frames (solid lines) of the region of interest AI and the feature point group FPG in FIGS. 10(a), (b), and (c) are actually displayed on the screen.

[0092] FIG. 10(d) shows a state in which the region of interest AI is displayed in the second X-ray image obtained at each X-ray irradiation timing at the display position of the region of interest AI set in the first X-ray image in the reference phase. In this example, the image update shown in FIG. 10(d) is performed only in the stationary phase. Note that the rectangular frame (broken line) of the region of interest AI in FIG. 10(d) is shown for convenience and is not actually displayed on the screen. Also, in the second X-ray image, the X-ray image collected last is displayed as it is in the regions other than the region of interest AI.

[0093] 〔Effects of the First Embodiment〕 According to the first embodiment, the exposure dose of the patient P can be suppressed as compared with the case of X-ray fluoroscopy imaging at a predetermined frame rate. Next, according to the first embodiment, since the imaging frame rate is increased as compared with electrocardiogram-synchronized fluoroscopy, the technician can view the latest X-ray image more frequently. As a result, the timing for proceeding with the procedure increases, and the device can reach the target site quickly, so the overall time of the procedure can be shortened. And since the region of interest AI is displayed statically, the procedure becomes easier. In other words, since there is no need to visually track the movement of the region of interest AI, the visibility is improved and the burden of the procedure can be reduced.

[0094] 〔Second Embodiment〕 Hereinafter, as the second embodiment, a modification of the first embodiment will be described.

[0095] (1) The imaging timing may be visualized. The display control function F5 may display the imaging timing on the screen of the display 90. Thereby, the user can grasp when the image is updated. The display control function F5 may, for example, display an electrocardiogram on the screen and highlight the points corresponding to the imaging timing in the electrocardiogram.

[0096] (2) The number of X-ray irradiation timings is not limited to two. Evaluation value D(N k , N j ) is smaller than a predetermined threshold value N k, N j When there are multiple combinations of X-ray irradiation timings, the number of X-ray irradiation timings may exceed two. For example, it may be three. When there are multiple candidates for the phase group used as the X-ray irradiation timing, the user may be able to select the X-ray irradiation timing.

[0097] (3) Depending on the shape of the feature point group FPG in the region of interest AI and the change in that shape, the definition of the evaluation value D(N i , N j ) may be made changeable. When calculating the evaluation value between regions of interest AI, based on the shape of the feature point group FPG in the region of interest AI obtained during the setting or trajectory calculation of the region of interest AI, it may be possible to select which definition of the evaluation value D(N i , N j ) to use. For example, for a region of interest AI where the apparent shape hardly changes in each phase, an evaluation value that focuses only on the position of the region of interest AI may be used. Also, when the change in the shape of the region of interest AI in each phase is mainly due to the difference in the degree of curvature of the curve, the calculation method of the evaluation value D(N i , N j ) that focuses on the curvature may be used.

[0098] (4) When obtaining the trajectory of the region of interest AI in each phase, the search range may be restricted. That is, after obtaining in advance the range within which the region of interest AI can move in each phase, the position of the region of interest AI may be tracked within that range. For example, the vicinity of the position of the previous region of interest AI may be defined as the range within which the region of interest AI can move. Also, based on the amount of movement and period of the region of interest AI due to respiratory motion, the range within which the region of interest AI can move may be corrected. According to this, the speed and accuracy of the search process can be improved.

[0099] According to at least one of the embodiments described above, while keeping the region of interest of the X-ray image stationary and displayed, the frame rate of the X-ray image can be improved.

[0100] Note that the first image acquisition function F1 is an example of the first image acquisition unit. The trajectory information acquisition function F2 is an example of the trajectory information acquisition unit. The stationary phase identification function F3 is an example of the identification unit. The second image acquisition function F4 is an example of the second image acquisition unit. The display control function F5 is an example of the display control unit. The memory control function F6 is an example of the memory control unit.

[0101] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations of the embodiments can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0102] 1…X-ray diagnostic apparatus 2…X-ray diagnostic system 5…Imaging unit 6…Medical image processing apparatus 90…Display 110…System control unit 111…Processing circuit F1…First image acquisition function F2…Trajectory information acquisition function F3…Stationary phase identification function F4…Second image acquisition function F5…Display control function F6…Memory control function

Claims

1. A first image acquisition unit that acquires a plurality of first X-ray images respectively corresponding to a plurality of cardiac phases; A trajectory information acquisition unit that acquires trajectory information indicating the trajectory of movement of a region of interest in the plurality of cardiac phases from the plurality of first X-ray images; A specifying unit that specifies a plurality of stationary phases respectively corresponding to the plurality of first X-ray images in which the difference in the position of the region of interest within one cardiac cycle is smaller than a threshold value based on the trajectory information; A second image acquisition unit that acquires a plurality of second X-ray images within each cardiac cycle by controlling to irradiate X-rays using the plurality of stationary phases within each cardiac cycle as a plurality of X-ray irradiation timings within each cardiac cycle; An X-ray diagnostic apparatus comprising the above.

2. The specifying unit: Specifies a plurality of stationary phases respectively corresponding to the plurality of first X-ray images when the trajectories of movement of the region of interest in the plurality of first X-ray images are close to or intersect each other. The X-ray diagnostic apparatus according to Claim 1.

3. The specifying unit: Extracts a characteristic figure from each of the regions of interest, calculates an evaluation value indicating the degree of variation between the figures, Extracts a plurality of regions of interest based on the evaluation value, and specifies the plurality of stationary phases of the plurality of first X-ray images corresponding to the plurality of regions of interest. The X-ray diagnostic apparatus according to Claim 1.

4. The specifying unit: Specifies the plurality of stationary phases such that the time difference between the plurality of stationary phases is equal to or greater than a predetermined value. The X-ray diagnostic apparatus according to Claim 3.

5. The predetermined value is a value obtained by dividing the time of one cardiac cycle by the desired number of the stationary phases. The X-ray diagnostic apparatus according to Claim 4.

6. The second image acquisition unit: Acquires an electrocardiogram waveform, specifies a plurality of cardiac phases in which the variation range of the electrocardiogram waveform is smaller than a threshold value, In each cardiac cycle, controls to irradiate X-rays using the cardiac phases close to each of the specified plurality of stationary phases as a plurality of irradiation timings. The X-ray diagnostic apparatus according to Claim 1.

7. Further includes a display control unit that superimposes and displays on a display unit an image of the region of interest extracted from the plurality of second X-ray images on a predetermined first X-ray image among the plurality of first X-ray images. The X-ray diagnostic apparatus according to Claim 1.

8. A first image acquisition unit that acquires a plurality of first X-ray images respectively corresponding to a plurality of cardiac phases; A trajectory information acquisition unit that acquires trajectory information indicating the trajectory of movement of a region of interest in the plurality of cardiac phases from the plurality of first X-ray images; A specifying unit that specifies a plurality of stationary phases corresponding to a plurality of first X-ray images in which the difference in the position of the region of interest within one heartbeat is smaller than a threshold value based on the trajectory information; A second image acquisition unit that acquires a plurality of second X-ray images within each heartbeat by controlling to irradiate X-rays using the plurality of stationary phases within each heartbeat as a plurality of X-ray irradiation timings; An X-ray diagnostic system comprising the above.

9. Further comprising an electrocardiograph, The second image acquisition unit, Acquires an electrocardiogram waveform from the electrocardiograph, specifies a plurality of cardiac phases in which the variation width of the electrocardiogram waveform is smaller than a threshold value, Controls to irradiate X-rays using, as a plurality of irradiation timings within each heartbeat, the cardiac phases close to each of the plurality of stationary phases within each heartbeat; The X-ray diagnostic system according to claim 8.

10. An X-ray control method by an X-ray diagnostic apparatus, comprising: Acquiring a plurality of first X-ray images respectively corresponding to a plurality of cardiac phases; Obtaining trajectory information indicating the trajectory of the movement of the region of interest in the plurality of cardiac phases from the plurality of first X-ray images; Based on the trajectory information, specifying a plurality of stationary phases corresponding to a plurality of second X-ray images in which the difference in the position of the region of interest within one heartbeat is smaller than a threshold value; Acquiring a plurality of second X-ray images within each heartbeat by controlling to irradiate X-rays using the plurality of stationary phases within each heartbeat as a plurality of X-ray irradiation timings within each heartbeat; An X-ray control method.

Images