X-ray diagnostic equipment and medical image processing equipment

Abstract

To estimate an indicator of cardiac length, regardless of imaging conditions. [Solution] The X-ray diagnostic apparatus according to the embodiment comprises an acquisition unit, a measurement unit, and a calculation unit. The acquisition unit acquires a first X-ray image taken of a subject from a first direction, the imaging distance of the first X-ray image, the body thickness of the subject, and the position of the subject's heart in the direction of the body thickness. The measurement unit measures the imaging size of the heart in the first X-ray image. The calculation unit calculates an index related to the length of the heart based on the imaging distance, body thickness, position of the heart, and the imaging size of the heart in the first X-ray image. The acquisition unit acquires the index in the first X-ray image. The calculation unit converts the index in the first X-ray image into an index in a second X-ray image, assuming that the image was taken from a second direction, which is a different direction from the first direction.

Description

Technical Field

[0001] The embodiments disclosed in this specification and the drawings relate to an X-ray diagnostic apparatus and a medical image processing apparatus.

Background Art

[0002] Chest X-ray imaging is an imaging diagnosis that is the first choice in the diagnosis of heart failure, and is an essential examination in an aging society where the number of heart failure patients is on the increase. Usually, X-ray imaging is performed from a distance of about 2 m from the back side of the patient. However, in the case of a patient whose condition is poor due to heart failure or the like and who has difficulty in standing for imaging, X-ray imaging may be performed from the front side at a distance of about 1 m in the supine position or while sitting in a wheelchair.

[0003] At this time, due to the fact that the heart and the X-ray tube are close to each other and the heart is located closer to the front of the human body, an X-ray image of the heart that is larger than the actual size is obtained. Even when doctors look at these X-ray images, it is difficult to determine whether the heart enlargement is due to heart failure or how different it is from the actual size of the heart.

[0004] Also, conventionally, doctors have determined whether there is heart enlargement based on the cardiothoracic ratio (the ratio of the width of the heart to the width of the chest) in X-ray images obtained by irradiation from the back side. However, when an X-ray image is obtained by irradiation from the front side as described above, the cardiothoracic ratio is different from that of an X-ray image obtained by irradiation from the back side, so the same determination as in the conventional case cannot be made. This is because the depth positions from the body surface of the heart and the chest are different, and the cardiothoracic ratio changes when the X-ray irradiation direction changes.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] One of the problems that the embodiments disclosed herein and in the drawings aim to solve is to estimate an index relating to the length of the heart, regardless of imaging conditions. However, the problems that the embodiments disclosed herein and in the drawings aim to solve are not limited to the above problem. Problems corresponding to the effects of each configuration shown in each embodiment described later can also be positioned as other problems. [Means for solving the problem]

[0007] The X-ray diagnostic apparatus according to the embodiment comprises an acquisition unit, a measurement unit, and a calculation unit. The acquisition unit acquires a first X-ray image of a subject taken from a first direction, the imaging distance of the first X-ray image, the body thickness of the subject, and the position of the subject's heart in the direction of body thickness. The measurement unit measures the imaging size of the heart in the first X-ray image. The calculation unit calculates an index relating to the length of the heart based on the imaging distance, body thickness, position of the heart, and imaging size of the heart in the first X-ray image. The acquisition unit acquires the index in the first X-ray image. The calculation unit converts the index in the first X-ray image into an index in a second X-ray image, assuming that the image was taken from a second direction, which is a different direction from the first direction. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a block diagram showing the configuration of an X-ray diagnostic apparatus according to the first embodiment. [Figure 2] Figure 2 is a block diagram showing the functions of the X-ray diagnostic apparatus according to the first embodiment. [Figure 3] Figure 3 shows the external appearance of the X-ray diagnostic apparatus according to the first embodiment. [Figure 4] Figure 4 is a diagram illustrating the cardiothoracic ratio. [Figure 5] Figure 5 shows the data necessary to calculate the actual size of the heart from a cross-sectional view of a subject lying on their back and from APX-ray images. [Figure 6] Figure 6 shows an example of a measurement method according to the first embodiment. [Figure 7]Figure 7 is a flowchart showing the processing of the X-ray diagnostic apparatus according to the second embodiment. [Figure 8] Figure 8 shows an example of the display screen of the display according to the second embodiment. [Figure 9] Figure 9 shows an example of the display screen of the display according to the third embodiment. [Figure 10] Figure 10 is a flowchart showing the processing of the X-ray diagnostic apparatus according to the fourth embodiment. [Figure 11] Figure 11 shows an example of an X-ray image according to the fourth embodiment. [Modes for carrying out the invention]

[0009] The embodiments of the X-ray diagnostic apparatus and the medical image processing apparatus will be described in detail below with reference to the drawings.

[0010] [First Embodiment] Figure 1 is a block diagram showing the configuration of the X-ray diagnostic apparatus 1 according to the first embodiment. Figure 2 is a block diagram showing the functions of the X-ray diagnostic apparatus 1. Figure 3 is a diagram showing the external appearance of the X-ray diagnostic apparatus 1. The X-ray diagnostic apparatus 1 comprises an imaging device 10 and a main console 70. The X-ray diagnostic apparatus 1 is a device that includes the imaging device 10, etc., and, under the control of the main console 70, performs X-ray imaging on a subject (e.g., a patient) P to acquire an X-ray image. For example, the X-ray diagnostic apparatus 1 includes a simple X-ray imaging device (e.g., a radiographer). The following describes the case where the X-ray diagnostic apparatus 1 is a simple X-ray imaging device.

[0011] The X-ray diagnostic device 1 performs X-ray imaging on the subject P and acquires one X-ray image. Here, the X-ray imaging is performed for the purpose of generating an X-ray image to be used for diagnosis.

[0012] The imaging device 10 includes a high-voltage generator 11, an X-ray generator 12, an X-ray detector 13, a standing examination table 9, a standing detector unit 16, a lying examination table 14, a lying detector unit 15, a ceiling rail 17, a trolley 18, a support column 19, and an imaging controller 21.

[0013] The high-voltage generator 11 generates a high voltage to be applied between the anode and the cathode in order to accelerate thermoelectrons generated from the cathode of the X-ray tube, and outputs the high voltage to the X-ray tube. The X-ray generation unit 12 includes an X-ray tube that irradiates the subject P with X-rays, and an X-ray collimator that directs the X-rays only to the region of interest of the subject P.

[0014] The X-ray tube generates X-rays. Specifically, the X-ray tube is a vacuum tube that holds a cathode that generates thermoelectrons and an anode that receives the thermoelectrons flying from the cathode and generates X-rays. The X-ray tube is connected to the high-voltage generator 11 via a high-voltage cable. A tube voltage is applied between the cathode and the anode by the high-voltage generator 11. Due to the application of the tube voltage, thermoelectrons fly from the cathode toward the anode. When thermoelectrons fly from the cathode toward the anode, a tube current flows. Due to the application of the high voltage from the high-voltage generator 11 and the supply of the filament current, thermoelectrons fly from the cathode toward the anode, and when the thermoelectrons collide with the anode, X-rays are generated.

[0015] The X-ray collimator is located between the X-ray tube and the X-ray detector 13 and is composed of a lead plate as a metal plate. The X-ray collimator narrows down the X-rays generated by the X-ray tube so that they irradiate only the region of interest of the subject P by shielding the X-rays outside the opening area.

[0016] The X-ray detector 13 detects the X-rays that have passed through the subject P. As such an X-ray detector 13, one that directly converts X-rays into electric charges and one that converts X-rays into light and then into electric charges can be used. Here, the former will be described as an example, but the latter may also be used. That is, the X-ray detector 13 includes, for example, a planar FPD (Flat Panel Detector) that converts the X-rays that have passed through the subject P into electric charges and accumulates them, and a gate driver that generates drive pulses for reading out the electric charges accumulated in the FPD. The accumulated electric charges are sequentially read out by the drive pulses supplied by the gate driver.

[0017] The standing examination table ⑨ is arranged vertically at a position facing the X-ray generation unit 12. The standing position detector unit 16 is supported by the standing position examination table 9 and arranged so as to be able to detect X-rays from the X-ray tube. The standing position detector unit 16 is changed in height along the standing position examination table 9 in accordance with the change in height of the X-ray generation unit 12 under the control of the processing circuit 74 of the main console 70.

[0018] The standing position detector unit 16 includes a standing position bucky 16a capable of housing the X-ray detector 13 and a standing position output circuit 16b including an A / D (Analog to digital) conversion circuit and the like. In FIG. 3, the standing position bucky 16a of the standing position detector unit 16 is shown in a state of housing the X-ray detector 13, but there may be a case where the lying position bucky 15a of the lying position detector unit 15 described later houses the X-ray detector 13. A grid (not shown) for removing scattered rays is provided on the front surface of the standing position bucky 16a.

[0019] The standing position bucky 16a has a shape such that the X-ray detector 13 can be detachably housed therein. Further, the standing position bucky 16a is provided at a position where it can detect the X-rays irradiated from the X-ray tube by the X-ray detector 13 housed therein. When the X-ray detector 13 is housed in the standing position bucky 16a, the X-ray detector 13 functions as a standing position detector, detects the transmitted X-rays from the standing subject P by simple radiography, and outputs them as an image signal to the standing position output circuit 16b.

[0020] The A / D conversion circuit of the standing position output circuit 16b inputs the analog signal (video signal) output from the X-ray detector 13 housed in the standing position bucky 16a and converts it into a digital image signal.

[0021] The lying position examination table 14 is arranged horizontally so that the subject P can be placed thereon and is arranged so as to be able to detect X-rays from the X-ray tube. The lying position examination table 14 slides the top plate 53 provided at the upper part under the control of the processing circuit 74 of the main console 70. The top plate 53 is a plate on which the subject P is placed.

[0022] The supine detector unit 15 is supported by the supine examination table 14. The supine detector unit 15 comprises a supine buckie 15a capable of housing the X-ray detector 13, and a supine output circuit 15b including an A / D conversion circuit, etc. A grid (not shown) for removing scattered radiation is provided on the front of the supine buckie 15a.

[0023] The supine Bucky 15a has a shape that allows the X-ray detector 13 to be detachably housed inside it. The supine Bucky 15a is positioned so that the X-rays irradiated from the X-ray tube can be detected by the X-ray detector 13 housed inside it. When the X-ray detector 13 is housed in the supine Bucky 15a, the X-ray detector 13 functions as a supine detector and detects transmitted X-rays from a supine subject P by simple radiography and outputs the image signal to the supine output circuit 15b.

[0024] The A / D conversion circuit of the supine output circuit 15b receives the analog signal (video signal) output from the X-ray detector 13 housed in the supine Bucky 15a and converts it into a digital image signal.

[0025] The ceiling rail 17 is laid on ceiling C. The trolley section 18 supports the X-ray generator 12 via the support column section 19. The trolley section 18 is engaged with the ceiling rail 17 so that it can move along the ceiling rail 17. The trolley section 18 allows the X-ray generator 12 to move between the side of the standing examination table 9 and the side of the lying examination table 14 under the control of the processing circuit 74 of the main console 70. That is, the trolley section 18 can change the distance between the X-ray tube (X-ray focus) and the X-ray detector 13 housed in the standing Bucky 16a. The trolley section 18 may be installed so that it can move horizontally in the direction along the ceiling rail 17 and in the direction perpendicular thereto.

[0026] The support column 19 is supported by the trolley 18 and rotatably supports the X-ray generating unit 12 at its lower end in both vertical and horizontal directions. The support column 19 is extendable and retractable in the vertical direction under the control of the processing circuit 74 of the main console 70. In other words, the support column 19 can change the distance between the X-ray tube and the X-ray detector 13 housed in the supine Bucky 15a.

[0027] The imaging controller 21, under the control of the processing circuit 74, moves the trolley section 18 horizontally via a motor (not shown) and extends and retracts the support column section 19 to set the imaging position, and irradiates X-rays from the X-ray tube via the high-voltage generator 11.

[0028] The X-ray diagnostic device 1 implements functions 741 to 749, which will be described later, using Figure 2. It is also possible that all of functions 741 to 749 are implemented by the main console 70 of the X-ray diagnostic device 1. Unless otherwise specified, the following description will focus on the case where all of functions 741 to 749 are implemented by the main console 70 (as shown in Figure 2).

[0029] The main console 70 includes memory 71, a display (also called a "system monitor") 72, an input interface 73, and a processing circuit 74. The main console 70 is an example of a medical image processing device.

[0030] The memory 71 comprises a memory unit that records electrical information, such as an HDD (Hard Disk Drive), and peripheral circuits such as a memory controller and memory interface associated with the memory unit. For example, the memory 71 stores a program executed by the processing circuit 74, X-ray images generated by the processing circuit 74, data used in the processing of the processing circuit 74, various tables, data during processing, and data after processing.

[0031] The display 72 displays various information, including X-ray images. The display 72 outputs, for example, X-ray images generated by the processing circuit 74, and a GUI (Graphical User Interface) for receiving various operations from the operator. For example, the display 72 is a liquid crystal display or a CRT (Cathode Ray Tube) display. The display 72 may also be a desktop type, or it may consist of a tablet terminal that can wirelessly communicate with the main console 70. The display 72 is an example of a display unit.

[0032] The input interface 73 receives predetermined information in response to operations performed by a user, such as a physician or technician, on the display 72. The input interface 73 can be implemented, for example, by a trackball for specifying the positions of the right and left ends of the heart, switch buttons, a mouse, a keyboard, a touchpad for input operations by touching the operating surface, or a touch panel display that integrates a display screen and a touchpad. The input interface 73 is connected to the processing circuit 74 and converts the input operations received from the operator into electrical signals and outputs them to the processing circuit 74. The input interface 73 may also consist of a tablet terminal or the like that can communicate wirelessly with the main console 70. The input interface 73 is an example of an input unit.

[0033] The processing circuit 74 is a processor that, by calling and executing a program in the memory 71, realizes the following functions, as shown in Figure 2: system control function 741, drive control function 742, shooting control function 743, image processing function 744, memory control function 745, display control function 746, data acquisition function 747, size measurement function 748, and index calculation function 749. Alternatively, the processing circuit 74 may be configured by combining multiple independent processors, with each processor executing a program to realize each function.

[0034] The system control function 741 includes, for example, a function that stores command signals from the operator input through the input interface 73, and information such as various initial setting conditions, and then transmits this information to each processing function of the processing circuit 74.

[0035] The drive control function 742 includes, for example, a function that controls the drive of the top plate 53 using information about the drive of the top plate 53 input from the input interface 73.

[0036] In addition to tilting the top plate 53, the drive control function 742 may also change the height of the top plate 53.

[0037] The imaging control function 743 includes, for example, a function that reads information from the system control function 741 and controls X-ray conditions such as tube voltage, tube current, and irradiation time in the high-voltage generator 11. The X-ray conditions may include the product of tube current and irradiation time (mAs).

[0038] The image processing function 744 includes the function of performing image processing on image data stored in memory 71 and storing the processed image data back in memory 71.

[0039] The memory control function 745 includes the function of storing various data in the memory 71 or reading data from the memory 71.

[0040] The display control function 746 includes, for example, a function to read signals from the system control function 741, acquire desired X-ray image data from the memory 71, and display it on the display 72.

[0041] The data acquisition function 747 includes the function of acquiring an APX image of the subject P taken from the AP (Anterior Posterior) direction, the imaging distance (SID, explained in Figure 5) of the APX image, the body thickness of the subject P, and the position of the subject P's heart in the direction of the body thickness. The AP direction is the imaging direction from the front to the back of the subject P, and is an example of the first direction. On the other hand, the PA (Posterior Anterior) direction is the imaging direction from the back to the front of the subject P, and is an example of the second direction. The APX image is an example of the first X-ray image.

[0042] The size measurement function 748 includes a function to measure the imaging size of the heart in APX images.

[0043] The index calculation function 749 includes a function to calculate an index related to the actual size of the heart, which is the actual size of the heart, based on the imaging distance of the APX-ray image, the body thickness of the subject P, the position of the heart, and the imaging size of the heart in the APX-ray image. The actual size of the heart is an example of the length of the heart.

[0044] Figure 4 is a diagram illustrating the cardiothoracic ratio. The cardiothoracic ratio is an indicator used to determine whether or not a patient has heart failure from a chest X-ray image. The cardiothoracic ratio is also called the cardiothoracic ratio or CTR (Cardio-Thoracic Ratio). As shown in Figure 4, the cardiothoracic ratio is the ratio of the width of the heart to the width of the chest, and is calculated using the following formula 1. Cardiothoracic ratio [%] = Width of the heart / Width of the rib cage × 100 ... Equation 1

[0045] Incidentally, heart failure is a disease in which the pumping function of the human heart deteriorates, causing shortness of breath and edema, gradually worsening the condition and shortening life. When the pumping function of the heart deteriorates, the heart enlarges (cardiomegaly). The cardiothoracic ratio is useful in determining cardiomegaly. Cardiomegaly is a finding when the cardiothoracic ratio in a chest X-ray image in the PA direction is 50% or more. The normal value for this cardiothoracic ratio is less than 50%. Furthermore, the cardiothoracic ratio is useful not only for heart failure and chronic heart failure, but also for confirming the effectiveness of fluid removal in dialysis treatment.

[0046] When performing cardiac X-ray imaging, the subject P is usually photographed from the PA direction. However, in the case of patients in poor condition, imaging may be performed from the AP direction while the patient is lying down, sitting in a wheelchair, or using a portable (mobile X-ray) device. When imaging from the AP direction, i.e., from the front of the subject P, the heart appears larger in the X-ray image than when imaging from the back. This is because, in the case of portable or lying-down imaging, the X-ray tube is closer to the subject P, so the heart is closer to the tube. Also, because the heart is located closer to the front of the subject P, imaging from the front of the subject P causes the heart to be further away from the surface of the X-ray detector 13 than when imaging from the back. Therefore, it is useful to calculate the actual size of the heart from the image size according to the difference in imaging direction. By calculating the actual size of the heart, it becomes possible to convert between the image size from the PA direction and the image size from the AP direction. For example, the data acquisition function 747 may acquire the cardiothoracic ratio in the APX image. Furthermore, the index calculation function 749 may convert the cardiothoracic ratio in the APX image to the cardiothoracic ratio in the PAX image based on the actual size of the heart and the actual size of the thoracic cage.

[0047] Figure 5 shows the data necessary to calculate the actual size of the heart from a cross-sectional view of subject P lying on their back (supine position) and APX-ray images. Figure 5(a) shows the case where subject P's back is in contact with the surface of the X-ray detector 13. Figure 5(b) shows the case where subject P's back is in contact with the upper surface of the tabletop 53, and the lower surface of the tabletop 53 is in contact with the surface of the X-ray detector 13.

[0048] The X-ray tube focus F is the X-ray source of the X-ray generation unit 12. X-rays are irradiated from the X-ray tube focus F toward the subject P from the AP direction, passing through the subject P and reaching the surface of the X-ray detector 13. SID (X-ray Source to Image receptor Distance) is the distance between the X-ray tube focus F and the surface of the X-ray detector 13, i.e., the imaging distance. Body thickness T is the height of the subject P's chest. Heart depth position H is the distance from the anterior (chest) side of the subject P's body surface to the protruding position of the heart. Table plate thickness L is the thickness of the table plate 53, or in other words, the distance between the subject P's back and the surface of the X-ray detector 13. The data acquisition function 747 acquires these values ​​from the memory 71 or the input interface 73.

[0049] Body thickness T may be input by, for example, the user measuring the chest height of the subject P and using the input interface 73 of the main console 70. A laser rangefinder, measuring tape, or an image of the subject P can be used to measure the chest height. The memory control function 745 may store the chest height of the subject P obtained through the input interface 73 in the memory 71. The data acquisition function 747 may read the chest height of the subject P from the memory 71. In other words, the data acquisition function 747 obtains body thickness T from the measured result of the subject P or from an image. The image is a tomographic image obtained from X-ray CT or MRI.

[0050] The protrusion of the heart consists of the right and left sides. The depth position H of the right and left sides of the heart can be estimated by various methods. First, body thickness T can be measured using a laser rangefinder, etc. Next, the depth position H can be estimated using statistical data related to the heart. For example, the depth position H of the right side of the heart is about 1 / 3 of the body thickness T, and the depth position H of the left side of the heart is about 1 / 6 of the body thickness T. More precise values ​​can be obtained from the average value of the apical position of the heart in Japanese people or from the diastolic pattern in heart failure. Furthermore, the depth position H can also be estimated using past examination data such as CT (Computed Tomography) of the subject P. Past examination data such as CT is an example of medical image data. In addition, the depth position H can be obtained from information of other modalities (e.g., ultrasound diagnostic equipment) obtained before X-ray imaging. In the case of a patient with heart failure, past data is important and useful because it is possible that X-rays have been taken many times. The depth position of the thoracic cage can also be estimated by various methods.

[0051] SOD (Source Object Distance) is the distance from the focal point F of the X-ray tube to the heart. The index calculation function 749 calculates SOD from the data acquired by the data acquisition function 747 and calculates the ratio of SOD to SID. This ratio makes it possible to calculate the actual size of the heart from the imaging size of the heart in the APX image. Furthermore, if the SID and SOD are known when the subject P is imaged from the PA direction, the index calculation function 749 calculates the ratio of SID to SOD. This ratio makes it possible to calculate the imaging size of the heart in the PAX image from the actual size of the heart. This applies not only to the size of the heart but also to the size of the rib cage.

[0052] When the back of the subject P is in contact with the surface of the X-ray detector 13, SOD is calculated by the following equation 2, as shown in Figure 5(a). SOD = SID-(TH)...Equation 2

[0053] When the back of subject P is in contact with the upper surface of the tabletop 53, according to Figure 5(b), SOD is calculated by the following formula 3. SOD = SID - (T - H + L) ... Equation 3

[0054] In the following explanation, subject P is lying face up on the tabletop 53, and the X-ray image is an APXY image of subject P taken from the AP direction.

[0055] The measurement method according to the first embodiment will be described below. Here, it is known that the imaging direction of the subject P is the AP direction, and the imaging size of the heart and thoracic cavity is measured in the APX image. Knowing the imaging direction means, for example, that it is clearly stated in the supplementary information of the X-ray image, that it is obvious from the orientation of the heart even if it is not in the supplementary information, or that the photographer who took the X-ray from the AP direction processes it immediately afterward.

[0056] Figure 6 shows an example of a measurement method according to the first embodiment. Figure 6(a) shows an example screen display of the depth position of the left heart, right heart, and thoracic cavity. Figure 6(b) shows an example screen display of the width of the left heart, right heart, and thoracic cavity. Both screen examples are displayed on, for example, the display 72.

[0057] Figure 6(a) shows an image illustrating a cross-section of subject P in the height and body thickness directions. The vertical lines indicating the depth positions of the left heart, right heart, and thoracic cage are all different. The data acquisition function 747 may acquire the depth position of each part, and the display control function 746 may display the vertical lines indicating the depth position of each part according to the acquired depth position. The image processing function 744 may create a general schematic diagram of the chest from image data such as X-ray CT images or X-ray images of subject P taken in the past, or it may create a general schematic diagram of the chest estimated from the body thickness T of subject P. Alternatively, the user may adjust the position of the vertical lines displayed on the display 72 by operating the input interface 73 while referring to the image showing the cross-section of subject P. The depth position of each part is determined by the position of each vertical line displayed on this screen. Therefore, the data acquisition function 747 acquires the depth positions of the heart and thoracic cage in the body thickness direction of subject P. Alternatively, the display control function 746 may not display a cross-sectional image of the chest, and the index calculation function 749 may directly obtain the depth position of each part from the data acquisition function 747 and use the depth position of each part for the index calculation.

[0058] Figure 6(b) shows an APX-ray image of the chest of subject P. A vertical line is drawn near the horizontal center to indicate the starting point of the measuring tape. The starting point of the measuring tape passes through the incident point (the intersection of the perpendicular line from the tube focal point F to the X-ray detector 13 and the surface of the X-ray detector 13). The user operates the input interface 73 to extend the measuring tape horizontally from the starting point and stops it at what is thought to be the left heart, right heart, and the ends of the rib cage (the most protruding parts). The user may also simply specify these positions.

[0059] The user may also select the left heart, right heart, and thoracic cage from the options shown in the upper right window. In this case, depths are set for each of these locations on the APX image, and the measure on the APX image is calculated based on the corresponding depth. The image processing function 744 may also search for boundaries from the APX image even if the user does not manipulate the measure. If the user selects other options such as the liver or kidney, the measure is calculated based on the depth corresponding to those organs when the measure is set. The image processing function 744 may also extract the contours of these organs.

[0060] Once the positions of the left and right hearts in the APX image are identified, the size measurement function 748 measures the imaging size of the heart (or left and right hearts) in the APX image. Once the position of the thorax in the APX image is identified, the size measurement function 748 measures the imaging size of the thorax in the APX image.

[0061] The index calculation function 749 calculates the actual size of the heart (or left and right heart) based on the SID of the APX-ray image, the body thickness of the subject P, the depth position of the heart, and the imaging size of the heart (or left and right heart) in the APX-ray image. Next, the index calculation function 749 calculates the actual size of the thoracic cage based on the SID of the APX-ray image, the body thickness of the subject P, the depth position of the thoracic cage, and the imaging size of the thoracic cage in the APX-ray image. The actual size of the thoracic cage is an example of the length of the thoracic cage. Then, the index calculation function 749 calculates the estimated cardiothoracic ratio, which is the ratio of the actual size of the heart to the actual size of the thoracic cage. The estimated cardiothoracic ratio is an example of an index related to the length of the heart, and is also an example of the first cardiothoracic ratio.

[0062] The index calculation function 749 calculates the imaging size of the heart in the PAX image based on the SID of the PAX image (assuming it was acquired from the PA direction, which is a different direction from the AP direction), the body thickness of the subject P, and the depth position and actual size of the heart. Next, the index calculation function 749 calculates the imaging size of the thoracic cage in the PAX image based on the SID of the PAX image, the body thickness of the subject P, and the depth position and actual size of the thoracic cage. Finally, the index calculation function 749 calculates the PA-corrected cardiothoracic ratio, which is the ratio of the imaging size of the heart to the imaging size of the thoracic cage in the PAX image. The PA-corrected cardiothoracic ratio is an example of a second cardiothoracic ratio.

[0063] As shown in the lower right window of Figure 6(b), the display control function 746 displays the actual sizes of the right heart, left heart, and thoracic cage, as well as the estimated cardiothoracic ratio and PA-corrected cardiothoracic ratio, on the display 72 as estimated values ​​for the heart and thoracic cage. The display control function 746 may also display either the estimated cardiothoracic ratio or the PA-corrected cardiothoracic ratio.

[0064] [Effects of the First Embodiment] According to the first embodiment, the actual cardiothoracic ratio of subject P can be estimated while taking into account that the X-ray image differs depending on the imaging conditions, including the imaging direction (PA direction, AP direction) and body position (standing, supine). Not only the heart, but also the actual size of organs (liver, kidneys, etc.) that are biased towards the anterior or posterior side of subject P can be estimated from the X-ray image.

[0065] Not only can the estimated cardiothoracic ratio of the heart be calculated from APX images, and then the PA-corrected cardiothoracic ratio, but the reverse approach is also possible. That is, the estimated cardiothoracic ratio of the heart can be calculated from PAX images, and then the AP-corrected cardiothoracic ratio can be calculated.

[0066] Since the actual size of the heart is determined, it is easy to compare the X-ray image taken at that time with past X-ray images taken under different imaging conditions. Furthermore, even if past data does not contain information on the body thickness of the subject P, making it impossible to determine the exact actual size of the heart, comparisons can still be made using statistical data.

[0067] [Second Embodiment] In the second embodiment, a method for calculating the cardiothoracic ratio while checking a reference image (cross-sectional image) will be described.

[0068] Figure 7 is a flowchart showing the processing of the X-ray diagnostic apparatus 1 according to the second embodiment. Figure 8 is a diagram showing an example of the display screen of the display 72 according to the second embodiment. Hereinafter, the measurement process according to the second embodiment will be described with reference to Figure 7 and Figure 8.

[0069] In step S1, the data acquisition function 747 of the processing circuit 74 acquires the APX-ray image, the SID of the APX-ray image, the body thickness T of the subject P, the top plate thickness L, and a reference image. The display control function 746 displays the acquired APX-ray image and reference image on the display 72. The reference image is an image showing a cross-section of the subject P's chest, and is either a schematic diagram or a CT image with thickness. The reference image is a VFF (View From Foot) image, that is, an image taken from the feet to the head of the subject P. At this time, as shown in Figure 8, the user specifies points J and K as the width of the subject P's rib cage in the APX-ray image displayed on the display 72.

[0070] In step S2, the image processing function 744 draws triangles A and B, which indicate the width of the thoracic cage, at the surface position of the X-ray detector 13 below the reference image. More specifically, the image processing function 744 draws triangles A and B, which indicate the orthogonal points, by drawing straight lines perpendicular to the line segment representing the surface of the X-ray detector 13 from points J and K, which are designated as the width of the thoracic cage.

[0071] In step S3, the image processing function 744 identifies points Q and R at the center height of the body thickness T of the reference image, indicating the position of the maximum rib cage protrusion. For example, the image processing function 744 extracts the geometric features indicated by the maximum rib cage protrusion near the center height of the reference image and identifies the two positions with these features as points Q and R.

[0072] In step S4, the image processing function 744 adjusts the size of the reference image so that the focal point F, point Q indicating the position of the rib cage protrusion, and triangle A are in a straight line, and that the focal point F, point R indicating the position of the rib cage protrusion, and triangle B are in a straight line. More specifically, since the focal point F and triangles A and B are fixed, the image processing function 744 enlarges or reduces the reference image with respect to the center point so that point Q lies on line segment FA and point R lies on line segment FB.

[0073] In step S5, the image processing function 744 draws a line segment connecting the tube focal point F and the X-ray incident point I. The X-ray incident point I is the center of the APX-ray image and is the intersection point of the perpendicular line drawn from the tube focal point F to the surface of the X-ray detector 13 and the surface itself.

[0074] In step S6, the image processing function 744 draws scales on the reference image. As shown in the reference image of Figure 8, a solid line indicating a scale of one-third of the body thickness T and a dashed line indicating a scale of one-ninth of the body thickness T are displayed. The reference image may also display lines with units that are easy for the user to understand, for example, lines indicating a scale of one-sixth of the body thickness T or lines indicating scales with a width of 1 cm.

[0075] Here, as shown in Figure 8, the user specifies points M and N as the width of the heart of subject P in the APX image displayed on the display 72.

[0076] In step S7, the image processing function 744 draws triangles C and D, which indicate the width of the heart, at the surface location of the X-ray detector 13 below the reference image. More specifically, the image processing function 744 draws triangles C and D, which indicate the orthogonal points, by drawing straight lines perpendicular to the line segments representing the surface of the X-ray detector 13 from points M and N, which are designated as the width of the heart.

[0077] In step S8, the image processing function 744 identifies points S and U in the reference image that indicate the position of the cardiac protrusion, based on the focal point F, triangles C and D, and the height position of the heart. More specifically, the image processing function 744 identifies the intersection of line segment FC and a line at a height of one-third of the body thickness T from the front of the subject P as the right heart S in the reference image. The image processing function 744 identifies the intersection of line segment FD and a line at a height of one-sixth of the body thickness T from the front of the subject P as point U, indicating the left heart in the reference image.

[0078] In step S9, the size measurement function 748 measures the actual size of the thoracic cage in the left-right direction from points Q and R, which indicate the position of the thoracic cage protrusion after adjusting the size of the reference image in step S4. Next, the size measurement function 748 measures the actual size of the heart in the left-right direction from points S and U, which indicate the position of the heart protrusion identified in step S8. Then, the index calculation function 749 calculates the actual estimated cardiothoracic ratio from the actual size of the thoracic cage and the actual size of the heart. The index calculation function 749 further calculates the PA-corrected cardiothoracic ratio. The display control function 746 displays the calculated estimated cardiothoracic ratio and PA-corrected cardiothoracic ratio on the display 72. The display control function 746 may display either the estimated cardiothoracic ratio or the PA-corrected cardiothoracic ratio.

[0079] The user can move point S along line segment FC. The user can also move point U along line segment FD. Each time, the estimated cardiothoracic ratio is recalculated and redisplayed. That is, the display control function 746 displays the estimated cardiothoracic ratio on the display 72 along with the APX image. The size measurement function 748 obtains the positions of the right and left ends of the heart in the APX image from the input interface 73. The index calculation function 749 calculates the estimated cardiothoracic ratio based on the positions of the right and left ends of the heart. The display control function 746 updates the estimated cardiothoracic ratio and displays it on the display 72. The size measurement function 748 may also use image processing or the like to identify the positions of the right and left ends of the heart in the APX image, and measure the imaging size of the heart based on the positions of the right and left ends of the heart.

[0080] According to this system, when a user changes the position of the heart protrusion in a reference image, the estimated cardiothoracic ratio is updated and displayed. Therefore, the position of the heart protrusion can be adjusted according to the different heart shapes of each individual. This can improve the accuracy of the estimated cardiothoracic ratio.

[0081] Furthermore, the index calculation function 749 may adjust the depth position of the heart (points S and U) so that the PA-corrected cardiothoracic ratio becomes a value indicating cardiomegaly. At this time, the display control function 746 displays the depth position of the heart on the display 72. In practice, the image of the heart is moved to a depth position in the reference image where the PA-corrected cardiothoracic ratio becomes 50%, which is the position at which heart failure is determined. At this time, the user can check whether or not it is heart failure by referring to the position of the heart in the transverse image of subject P. For example, if the position of the heart after moving deviates from the statistical data, the user can determine that "such a position of the heart is impossible, so it is not cardiomegaly." Alternatively, the index calculation function 749 may determine whether or not it is cardiomegaly based on the result of comparing the depth position of the heart adjusted so that the PA-corrected cardiothoracic ratio becomes a value indicating cardiomegaly with statistical data on the heart.

[0082] [Third Embodiment] In the third embodiment, a method for calculating and displaying both estimated cardiothoracic ratios when it is unknown whether the imaging direction of subject P is AP or PA is described. The imaging direction being unknown may occur, for example, when the supplementary information in the X-ray image is questionable, when there was an input error during X-ray imaging, or when the internal organs are inverted.

[0083] Figure 9 shows an example of the display screen of the display 72 according to the third embodiment. Figure 9(a) shows an example of the display screen assuming that an X-ray image is acquired from the AP direction. Figure 9(b) shows an example of the display screen assuming that an X-ray image is acquired from the PA direction.

[0084] The configuration of the display screen and the procedure for calculating the estimated cardiothoracic ratio from the X-ray image are the same as in the second embodiment. The reference image in Figure 9(a) is an image taken from the feet to the head of the subject P. In Figure 9(a), since imaging from the AP direction is assumed, the upper part of the reference image is the front side of the subject P, so the heart is located about one-third of the way from the top of the transverse image. The reference image in Figure 9(b) is an image taken from the feet to the head of the subject P. In Figure 9(b), since imaging from the PA direction is assumed, the lower part of the reference image is the front side of the subject P, so the heart is located about one-third of the way from the bottom of the transverse image.

[0085] As shown in Figures 9(a) and 9(b), button BT is located on the upper left side of the reference image. The estimated cardiothoracic ratio is displayed on the upper right side of the reference image. Button BT is an operation button for switching the assumed imaging direction. When "AP" on button BT is clicked, the reference image switches to an image with the heart at the top, the estimated cardiothoracic ratio (e.g., 49%) is calculated, and its displayed value is updated. In addition, the PA-corrected cardiothoracic ratio and the AP cardiothoracic ratio may be displayed. When "PA" on button BT is clicked, the reference image switches to an image with the heart at the bottom, the estimated cardiothoracic ratio (e.g., 70%) is calculated, and its displayed value is updated. In addition, the AP-corrected cardiothoracic ratio and the PA cardiothoracic ratio may be displayed.

[0086] [Fourth Embodiment] In the fourth embodiment, a method for improving the accuracy of the actual size of the heart using a pencil beam and for accurately measuring the depth position of the heart will be described.

[0087] Figure 10 is a flowchart showing the processing of the X-ray diagnostic apparatus 1 according to the fourth embodiment. Figure 11 is a diagram showing an example of an X-ray image according to the fourth embodiment. Figure 11(a) is a schematic diagram showing the contours of the heart obtained by X-ray imaging and the actual heart. Figure 11(b) is a schematic diagram showing an X-ray image of a part of the heart obtained by a pencil beam. Figure 11(c) is a diagram showing a comparison of X-ray images obtained by the tube focus F and the pencil beam.

[0088] The measurement process according to the fourth embodiment will be described below, with reference to Figure 11, following Figure 10.

[0089] In step S11, the data acquisition function 747 of the processing circuit 74 acquires an APX-ray image of the subject P's chest taken from the AP direction.

[0090] In step S12, the user takes an image while moving the pencil beam from a position corresponding to the X-ray incident point I toward the apex of the heart. At this time, the pencil beam is moved in a straight line parallel to the surface of the X-ray detector 13. Here, the top plate 53 on which the subject P is placed may move, or the tube of the pencil beam may move. Furthermore, X-ray exposure may be performed only in the vicinity of the heart. In addition to the pencil beam, imaging may also be performed using a narrow fan beam.

[0091] In step S13, the data acquisition function 747 acquires the X-ray image captured by the pencil beam. As shown in Figure 11(b), the X-ray image captured by the pencil beam is elongated rectangular (band-shaped). The X-ray image captured by the pencil beam is an example of the first X-ray image.

[0092] In step S14, the size measurement function 748 identifies the area where the pixel count drops sharply as the apex, which is the boundary of the heart. The apex is one example of the location of the left edge of the heart.

[0093] If it is difficult to identify the boundaries of the heart due to fluid accumulation or other reasons, in step S12, the user widens the pencil beam to perform imaging. Since the only value that needs to be accurate is the length of the line passing through the center of the band-shaped image, distortion around the edges of the band-shaped image is acceptable.

[0094] In step S15, the size measurement function 748 measures the distance between the X-ray incident point I and the apex, which is the boundary of the heart. The size measurement function 748 may calculate this distance from the coordinates of the X-ray incident point I and the coordinates of the apex. Alternatively, the user may click two points (X-ray incident point I and apex) on the X-ray image acquired by the pencil beam. In this case, the size measurement function 748 measures the distance between the two points clicked by the user. As shown in Figure 11(a), the measured distance is not parallel to the right, so it is advisable to correct it to the distance projected onto the right axis. However, if the apex is captured on the APX image, instead of "correcting it to the distance projected onto the right axis," the amount of rightward movement of the top plate or tube may be obtained from the device that controls the movement of the top plate or tube and used.

[0095] In step S16, the size measurement function 748 determines the height position of the cardiac apex based on the distance between the X-ray incident point I and the cardiac apex. As shown in Figure 11(c), the positions of the tube focus F, the triangle D indicating the contour of the heart, and the X-ray incident point I are determined, so the height position of the cardiac apex can be determined from the distance between the X-ray incident point I and the cardiac apex.

[0096] In step S17, similar to steps S12-S14, the size measurement function 748 identifies the position of the right heart, which is the right-sided protrusion. The position of the right heart is an example of the position of the rightmost edge of the heart. The size measurement function 748 may measure the imaging size of the heart based on the positions of the right heart and the apex.

[0097] In step S18, similar to step S15, the size measuring function 748 measures the distance between the X-ray incidence point I and the right heart.

[0098] In step S19, the size measurement function 748 determines the height position of the right heart based on the distance between the X-ray incident point I and the right heart. As shown in Figure 11(c), the positions of the tube focus F, the triangle C indicating the contour of the heart, and the X-ray incident point I are determined, so the height position of the right heart can be determined from the distance between the X-ray incident point I and the right heart.

[0099] In step S20, the size measurement function 748 calculates the actual size of the heart by adding the distance measured in step S15 (length of the leftward dashed arrow in Figure 11(a)) and the distance measured in step S18 (length of the rightward solid arrow in Figure 11(a)). Next, the index calculation function 749 calculates the estimated cardiothoracic ratio from the actual size of the heart and the actual size of the thoracic cavity. The index calculation function 749 further calculates the AP-corrected cardiothoracic ratio. Then, the display control function 746 displays the calculated estimated cardiothoracic ratio and AP-corrected cardiothoracic ratio on the display 72. The actual size of the thoracic cavity is measured by the size measurement function 748, as in the first embodiment.

[0100] [Effects of the fourth embodiment] For example, by irradiating the surface of the X-ray detector 13 perpendicularly with a pencil beam, the position of the irradiated area, unaffected by the radial spread of the X-rays, can be determined, allowing the actual coordinates of the position to be measured to be obtained. Consequently, an imaging size approximately the same as the actual size of the heart can be obtained, eliminating the difference in the actual size of the heart due to differences in the depth position H of the heart. Furthermore, distortion of the X-ray image caused by the position (height) of the X-ray tube focal point F can be corrected.

[0101] According to at least one embodiment described above, an index relating to the length of the heart can be estimated regardless of imaging conditions.

[0102] Note that the display control function 746 is an example of a display control unit. The data acquisition function 747 is an example of a data acquisition unit. The size measurement function 748 is an example of a measurement unit. The index calculation function 749 is an example of a calculation unit.

[0103] While several embodiments have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be implemented in a variety of other forms, and various omissions, substitutions, modifications, and combinations of embodiments are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0104] 1...X-ray diagnostic equipment 53... Tabletop 70…Main Console 71…Memory 72…Display 73…Input Interface 746…Display control function 747...Data acquisition function 748... Size measurement function 749…Indicator calculation function P...Subject

Claims

1. An acquisition unit that acquires a first X-ray image of a subject taken from a first direction, the imaging distance of the first X-ray image, the body thickness of the subject, and the position of the subject's heart in the direction of the body thickness. A measuring unit for measuring the imaging size of the heart in the first X-ray image, A calculation unit calculates an index relating to the length of the heart based on the imaging distance, the body thickness, the position of the heart, and the imaging size of the heart in the first X-ray image. Equipped with, The acquisition unit acquires the index in the first X-ray image, The calculation unit converts the index in the first X-ray image into the index in a second X-ray image, assuming that the image was taken from a second direction which is different from the first direction. X-ray diagnostic equipment.

2. The acquisition unit acquires the position of the rib cage in the body thickness direction, The measurement unit measures the imaging size of the chest cavity in the first X-ray image, The calculation unit described above, Based on the imaging distance, the body thickness, the position of the thorax, and the imaging size of the thorax in the first X-ray image, the length of the thorax is calculated. The first cardiothoracic ratio, which is the ratio of the length of the heart to the length of the thoracic cage, is calculated. The X-ray diagnostic apparatus according to claim 1.

3. The calculation unit described above, Based on the imaging distance of the second X-ray image, the body thickness, the position and length of the heart, and the position and length of the thoracic cavity, the imaging size of the heart and the imaging size of the thoracic cavity in the second X-ray image are calculated. The second cardiothoracic ratio, which is the ratio of the imaging size of the heart to the imaging size of the thoracic cage in the second X-ray image, is calculated. The X-ray diagnostic apparatus according to claim 2.

4. The first direction is the direction from the front to the back of the subject, The second direction is the direction from the back to the front of the subject. The X-ray diagnostic apparatus according to claim 3.

5. The system further includes a display control unit that displays at least one of the first cardiothoracic ratio and the second cardiothoracic ratio on the display unit. The X-ray diagnostic apparatus according to claim 3.

6. The aforementioned measuring unit is Identify the positions of the right and left ends of the heart in the first X-ray image, The imaging size of the heart is measured based on the positions of the right and left ends of the heart. The X-ray diagnostic apparatus according to claim 1.

7. A display control unit that displays an index relating to the length of the heart together with the first X-ray image on the display unit, An input unit that inputs predetermined information in response to user operations on the display unit, Furthermore, The aforementioned measuring unit is The positions of the right and left ends of the heart in the first X-ray image are obtained from the input unit. The calculation unit described above, Based on the positions of the right and left ends of the heart, an index relating to the length of the heart is calculated. The display control unit, The index relating to the length of the heart is updated and displayed on the display unit. The X-ray diagnostic apparatus according to claim 6.

8. The acquisition unit is, The body thickness is obtained from the measured results of the subject or from an X-ray image of the subject. The X-ray diagnostic apparatus according to claim 1.

9. The acquisition unit is, The position of the heart is obtained from statistical data related to the heart or medical image data of the subject. The X-ray diagnostic apparatus according to claim 1.

10. The calculation unit described above, The position of the heart is adjusted so that the second cardiothoracic ratio indicates cardiomegaly. The system further includes a display control unit that displays the location of the heart on the display unit. The X-ray diagnostic apparatus according to claim 3.

11. Display unit and An acquisition unit that acquires a first X-ray image of a subject taken from a first direction, the imaging distance of the first X-ray image, the body thickness of the subject, and the position of the subject's heart in the direction of the body thickness. A measuring unit for measuring the imaging size of the heart in the first X-ray image, A calculation unit calculates an index relating to the length of the heart based on the imaging distance, the body thickness, the position of the heart, and the imaging size of the heart in the first X-ray image. A display control unit that causes the indicator relating to the length of the heart to be displayed on the display unit, A medical image processing device equipped with [a specific feature].

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