JP6640522B2 - Image processing apparatus and X-ray diagnostic apparatus - Google Patents

Description

  Embodiments of the present invention relate to an image processing apparatus and an X-ray diagnostic apparatus.

  2. Description of the Related Art Conventionally, in an X-ray diagnostic apparatus, an intravascular intervention treatment using a contrast agent containing, for example, iodine as a main component has been performed. In the intravascular intervention treatment, the contrast agent concentration in the subject may be estimated from an X-ray image collected by an X-ray diagnostic apparatus. For example, it is known that assessing the perfusion of a contrast agent flowing into tissue during a procedure for interventional treatment of the coronary artery in ischemic heart disease can improve the prognosis. Attempts to measure perfusion with angiographic images have been proposed.

  Here, in the X-ray diagnostic apparatus, the luminance value of the two-dimensional image and the contrast agent concentration do not show a proportional relationship due to scattered radiation, beam hardening, or the like. Therefore, in order to accurately measure perfusion in a two-dimensional angiographic image, it is necessary to perform correction so that the luminance value and the contrast agent concentration are proportional. As such a correction method, for example, a method of performing calibration in advance at the time of acquiring a contrast image, a method of performing correction using a phantom, and the like are known. However, in the above-described conventional technology, complicated calibration is required in advance, or a phantom needs to be prepared, which is troublesome, and furthermore, a correction process is not performed on a collected contrast image. It was difficult.

JP 2008-136800 A JP 2012-115651 A JP-A-2015-142719

  It is an object of the present invention to provide an image processing apparatus and an X-ray diagnostic apparatus which can easily correct a contrast image.

An image processing device according to an embodiment includes an acquisition unit and a correction unit. The acquisition unit, based on each of the two or more contrast agent densities, a plurality of luminance values in the contrast image corresponding to each of the densities , and the thickness of the contrast agent in the projection direction of the contrast agent, Correction information of the brightness value of the contrast image according to the scattered radiation at the time of collection and the body thickness of the subject is acquired. The correction unit corrects the contrast image using the correction information. The acquisition unit is a curve indicating the relationship between the brightness value and the density and thickness of the contrast agent in the contrast image, the plurality of brightness values corresponding to the respective densities and the respective densities and the thickness of the contrast agent. The correction unit that calculates the scattered radiation and the body thickness when the relationship is satisfied, and obtains a correction curve based on the calculated scattered radiation and a curve corresponding to the body thickness, the pixel in the contrast image using the correction curve Is corrected.

FIG. 1 is a diagram illustrating an example of the configuration of the X-ray diagnostic apparatus according to the first embodiment. FIG. 2 is a diagram for explaining an outline of the processing of the X-ray diagnostic apparatus according to the first embodiment. FIG. 3 is a diagram for describing X-rays according to the first embodiment. FIG. 4 is a diagram for explaining a process of estimating a correction curve using a single-density contrast agent according to the first embodiment. FIG. 5 is a diagram for explaining a process of estimating a correction curve using a single-density contrast agent according to the first embodiment. FIG. 6 is a diagram for explaining a process of estimating a correction curve using a single-contrast contrast agent according to the first embodiment. FIG. 7 is a diagram schematically illustrating processing by the correction function according to the first embodiment. FIG. 8 is a diagram illustrating an example of a case where the correction processing according to the first embodiment is performed. FIG. 9 is a diagram illustrating an example of a process performed by the calculation function according to the first embodiment. FIG. 10A is a diagram for explaining a contrast agent injected by the injector according to the first embodiment. FIG. 10B is a diagram for explaining the contrast agent injected by the injector according to the first embodiment. FIG. 11A is a diagram illustrating an example of a change in the contrast agent concentration according to the first embodiment. FIG. 11B is a diagram illustrating an example of a change in contrast agent concentration according to the first embodiment. FIG. 12 is a diagram for explaining a process of calculating a correction curve using a plurality of density contrast agents according to the first embodiment. FIG. 13 is a flowchart illustrating a procedure of a correction process using a correction curve estimated with a single-density contrast agent according to the first embodiment. FIG. 14 is a flowchart illustrating a procedure of a correction process using a correction curve estimated by a plurality of contrast agents according to the first embodiment. FIG. 15 is a diagram schematically illustrating information stored by the storage circuit according to the second embodiment. FIG. 16 is a diagram illustrating an example of a process performed by the acquisition function according to the third embodiment.

(First embodiment)
FIG. 1 is a diagram illustrating an example of a configuration of the X-ray diagnostic apparatus 100 according to the first embodiment. As shown in FIG. 1, the X-ray diagnostic apparatus 100 according to the first embodiment includes a high-voltage generator 11, an X-ray tube 12, a collimator 13, a top 14, a C-arm 15, an X-ray And a detector 16. Further, the X-ray diagnostic apparatus 100 according to the first embodiment includes a C-arm rotation / movement mechanism 17, a couchtop movement mechanism 18, a C-arm / couchtop mechanism control circuit 19, an aperture control circuit 20, A circuit 21, an input circuit 22, and a display 23 are provided. The X-ray diagnostic apparatus 100 according to the first embodiment includes an image data generation circuit 24, a storage circuit 25, and an image processing circuit 26. The X-ray diagnostic apparatus 100 is connected to the injector 30. In the X-ray diagnostic apparatus 100, as shown in FIG. 1, the respective circuits are interconnected, and various electric signals are transmitted and received between the circuits, and electric signals are transmitted and received with the injector 30.

  The injector 30 is a device for injecting a contrast agent from a catheter inserted into the subject P. Here, the injection of the contrast agent from the injector 30 is executed according to an injection instruction received via the processing circuit 21 described later. Specifically, the injector 30 executes a contrast agent injection instruction according to a contrast agent injection condition including an injection start instruction, an injection stop instruction, and an injection speed received from the processing circuit 21 described later. In addition, the injector 30 can also execute injection start and injection stop according to an injection instruction directly input to the injector 30 by the operator. Further, the injector 30 can inject the contrast agent while changing the concentration. For example, the injector 30 changes the concentration of the contrast agent by injecting different concentrations of the contrast agent, or adds water so that the concentration of the contrast agent of a single concentration becomes a predetermined dilution ratio. Or the concentration of the agent can be varied.

  In the X-ray diagnostic apparatus 100 shown in FIG. 1, each processing function is stored in the storage circuit 25 in the form of a program executable by a computer. The C-arm / top mechanism control circuit 19, the aperture control circuit 20, the processing circuit 21, the image data generation circuit 24, and the image processing circuit 26 correspond to each program by reading and executing the program from the storage circuit 25. It is a processor that implements functions. In other words, each circuit in a state where each program is read has a function corresponding to the read program.

  The term “processor” used in the above description may be, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or an application specific integrated circuit (ASIC), a programmable logic device (ASIC). For example, it means a circuit such as a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA). The processor realizes functions by reading and executing a program stored in the storage circuit. Instead of storing the program in the storage circuit, the program may be directly incorporated in the circuit of the processor. In this case, the processor realizes a function by reading and executing a program incorporated in the circuit. Note that each processor of the present embodiment is not limited to the case where each processor is configured as a single circuit, but may be configured as one processor by combining a plurality of independent circuits to realize its function. Good.

  The high voltage generator 11 generates a high voltage under the control of the processing circuit 21 and supplies the generated high voltage to the X-ray tube 12. The X-ray tube 12 generates X-rays using a high voltage supplied from the high voltage generator 11.

  The collimator 13 narrows down the X-rays generated by the X-ray tube 12 so as to be selectively irradiated on the region of interest of the subject P under the control of the aperture control circuit 20. For example, the collimator 13 has four slidable diaphragm blades. The collimator 13 slides these diaphragm blades under the control of the diaphragm control unit 20, thereby narrowing down the X-rays generated by the X-ray tube 12 and irradiating the X-ray to the subject P. The top plate 14 is a bed on which the subject P is placed, and is arranged on a bed (not shown). Note that the subject P is not included in the X-ray diagnostic apparatus 100.

  The X-ray detector 16 detects X-rays transmitted through the subject P. For example, the X-ray detector 16 has detection elements arranged in a matrix. Each detection element converts the X-ray transmitted through the subject P into an electric signal, accumulates the electric signal, and transmits the accumulated electric signal to the image data generation circuit 24.

  The C arm 15 holds the X-ray tube 12, the collimator 13, and the X-ray detector 16. The X-ray tube 12, the collimator 13, and the X-ray detector 16 are arranged to face each other with the subject P interposed therebetween by the C-arm 15. Although FIG. 1 illustrates an example in which the X-ray diagnostic apparatus 1 is a single plane, the embodiment is not limited to this and may be a biplane.

  The C-arm rotation / movement mechanism 17 is a mechanism for rotating and moving the C-arm 15, and the couchtop movement mechanism 18 is a mechanism for moving the couchtop 14. The C arm / top mechanism control circuit 19 controls the rotation and movement of the C arm 15 and the movement of the top 14 by controlling the C arm rotation / movement mechanism 17 and the top movement mechanism 18 under the control of the processing circuit 21. Coordinate movement. The aperture control circuit 20 controls the irradiation range of the X-ray irradiated on the subject P by adjusting the opening of the aperture blade of the collimator 13 under the control of the processing circuit 21.

  The image data generation circuit 24 generates image data using the electric signal converted from the X-rays by the X-ray detector 16 and stores the generated image data in the storage circuit 25. For example, the image data generation circuit 24 performs current / voltage conversion, A (Analog) / D (Digital) conversion, and parallel / serial conversion on the electric signal received from the X-ray detector 16 to generate image data. I do. For example, the image data generation circuit 24 generates image data (mask image) captured in a state where the contrast agent is not injected and image data (contrast image) captured in a state where the contrast agent is injected. I do. Then, the image data generation circuit 24 stores the generated mask image and contrast image in the storage circuit 25. Here, the image data generation circuit 24 can also generate a plurality of contrast images captured while changing the concentration of the contrast agent injected into the same subject, and store the plurality of contrast images in the storage circuit 25.

  The storage circuit 25 receives and stores the image data generated by the image data generation circuit 24. For example, the storage circuit 25 stores image data of the subject P before and after the contrast agent is administered. The storage circuit 25 stores programs corresponding to various functions that are read and executed by the respective circuits illustrated in FIG. For example, the storage circuit 25 stores a program corresponding to the acquisition function 211, a program corresponding to the correction function 212, and a program corresponding to the calculation function 213, which are read and executed by the processing circuit 21.

  The image processing circuit 26 performs various types of image processing on the image data stored in the storage circuit 25. For example, the image processing circuit 26 reads out the mask image and the contrast image stored in the storage circuit 25 and performs subtraction (Log sub) to generate a difference image. Here, the image processing circuit 26 can also generate a plurality of difference images by subtracting each of the plurality of contrast images and the mask image captured in a state where contrast agents having different densities are injected.

  The input circuit 22 is realized by a trackball, a switch button, a mouse, a keyboard, and the like for setting a predetermined area (for example, a catheter area) and the like. The input circuit 22 is connected to the processing circuit 21, converts an input operation received from an operator into an electric signal, and outputs the electric signal to the processing circuit 21.

  The display 23 displays a GUI (Graphical User Interface) for receiving an instruction from the operator, a difference image generated by the image processing circuit 26, and the like.

  The processing circuit 21 controls the operation of the entire X-ray diagnostic apparatus 100. The processing circuit 21 executes various processing by reading out programs corresponding to various processing functions for controlling the entire apparatus from the storage circuit 25 and executing the programs. For example, the processing circuit 21 controls the high-voltage generator 11 in accordance with the operator's instruction transferred from the input circuit 22, adjusts the voltage supplied to the X-ray tube 12, and irradiates the subject P with light. X-ray dose and ON / OFF. Further, for example, the processing circuit 21 controls the C-arm / top mechanism control circuit 19 in accordance with an operator's instruction, and adjusts the rotation and movement of the C-arm 15 and the movement of the top 14. Further, for example, the processing circuit 21 controls the aperture control circuit 20 in accordance with an operator's instruction, and adjusts the aperture of the aperture blade of the collimator 13 to irradiate the subject P with X-rays. Control the range.

  Further, the processing circuit 21 controls the image data generation processing by the image data generation circuit 24, the image processing by the image processing circuit 26, or the analysis processing according to the instruction of the operator. Further, the processing circuit 21 controls the display 23 to display a GUI for receiving an operator's instruction, an image stored in the storage circuit 25, and the like. Further, the processing circuit 21 controls the injection timing of the contrast agent by transmitting a contrast agent injection start and end signal to the injector 30. Here, the processing circuit 21 controls the concentration of the contrast agent injected into the subject by transmitting a signal for changing the concentration of the contrast agent to the injector 30.

  The example of the configuration of the X-ray diagnostic apparatus 100 has been described above. With such a configuration, the X-ray diagnostic apparatus 100 according to the present embodiment makes it possible to easily correct a contrast image by processing performed by the processing circuit 21 described in detail below. As described above, in a two-dimensional contrast image, since the brightness value of the image and the contrast agent concentration do not show a proportional relationship, for example, when an attempt is made to accurately measure perfusion, the brightness value and the contrast agent concentration are different. It is required to make a proportional correction. Therefore, in the present embodiment, in order to facilitate correction of a contrast image, correction using only a contrast image is performed without performing correction using complicated calibration or correction using a phantom in the related art.

  Specifically, the X-ray diagnostic apparatus 100 according to the first embodiment uses the contrast agent concentration and the contrast agent density in the two-dimensional contrast image in the contrast image using the brightness value in a region where the density and the thickness of the contrast agent are known. A correction curve indicating the relationship with the luminance value is estimated, and the luminance value of each pixel in the contrast image is corrected using the estimated correction curve. FIG. 2 is a diagram for explaining the outline of the processing of the X-ray diagnostic apparatus 100 according to the first embodiment. For example, a two-dimensional contrast image often includes a catheter as shown in FIG. Then, the concentration of the contrast agent and the size of the catheter used when collecting the contrast image are known. That is, the brightness value of the catheter region in the contrast image is a value based on the contrast agent whose thickness for the catheter is not reduced in the projection direction.

  Therefore, for example, as shown in FIG. 2, the X-ray diagnostic apparatus 100 uses a catheter in which a contrast agent has a known density (eg, 370 mg / ml) and a known thickness (eg, 3 mm) in a contrast image (difference image). The signal strength (brightness value) of the area is measured, and a correction curve is estimated by simulation from the relationship between the measured signal strength (brightness value) and the density and thickness of the contrast agent. For example, as shown in FIG. 2, the X-ray diagnostic apparatus 100 displays the measured signal on a graph in which the horizontal axis is “contrast agent density × thickness” and the vertical axis is “signal intensity (brightness value) of difference image”. The intensity is plotted, and a curve passing through the plotted points is estimated as a correction curve. Here, the curve indicating the relationship between the signal intensity and the contrast agent concentration and thickness in the contrast image (difference image) depends on the X-ray quality and scattered radiation. That is, if the X-ray quality and scattered radiation at the time of capturing the difference image can be estimated, a correction curve in the difference image can be determined from the measured signal intensity and the concentration and thickness of the contrast agent.

  The X-ray diagnostic apparatus 100 according to the first embodiment uses a luminance value measured in a difference image captured in a state where a single concentration of a contrast agent is injected and a concentration and a thickness of the contrast agent to obtain an X-ray A correction curve can be estimated by performing a simulation while changing the conditions regarding the radiation quality and the scattered radiation. Further, the X-ray diagnostic apparatus 100 compares the X-ray quality and scattered radiation by using the measured luminance value and the contrast agent concentration and thickness in a plurality of difference images captured by changing the concentration of the contrast agent. The calculated correction curve can be calculated based on the calculated X-ray quality and scattered radiation. Note that details of estimation of a correction curve based on a difference image captured in a state where a single concentration of the contrast agent is injected and calculation of a correction curve based on a plurality of difference images captured by changing the concentration of the contrast agent will be described. Will be described later.

  The X-ray diagnostic apparatus 100 corrects the luminance value of each pixel in the contrast image by using the estimated correction curve. For example, the X-ray diagnostic apparatus 100 calculates the value of “contrast agent density × thickness” corresponding to the luminance value of each pixel in the contrast image using the correction curve, and calculates the luminance value of each pixel. By doing so, the contrast image is corrected. Hereinafter, details of the above-described embodiment will be described. In the X-ray diagnostic apparatus 100 according to the first embodiment, the processing circuit 21 reads out programs corresponding to the acquisition function 211, the correction function 212, and the calculation function 213 shown in FIG. Then, the above-described contrast image correction processing is performed. Note that the acquisition function 211, the correction function 212, and the calculation function 213 illustrated in FIG. 1 correspond to the acquisition unit, the correction unit, and the calculation unit in the claims, respectively.

  Here, in the following embodiment, first, a correction curve is estimated based on a difference image captured in a state where a single concentration of a contrast agent is injected, and a contrast image is corrected using the estimated correction curve. Then, an example of calculating a correction curve based on a plurality of difference images captured by changing the density of the contrast agent will be described.

  When estimating the correction curve based on the difference image captured in a state where a single concentration of the contrast agent is injected, the acquisition function 211 performs the processing of the contrast agent in a predetermined region in the contrast image collected using the contrast agent. Based on the density and the thickness of the contrast agent in the projection direction, correction information of the brightness value of the contrast image according to the scattered radiation at the time of collection of the contrast image and the body thickness of the subject is acquired. Specifically, the acquisition function 211 performs the processing when the curve indicating the relationship between the luminance value in the contrast image and the concentration and the thickness of the contrast agent satisfies the relationship between the luminance value and the concentration and the thickness of the contrast agent in a predetermined region. The scattered radiation and the body thickness are estimated, and a correction curve is obtained based on a curve corresponding to the estimated scattered radiation and the body thickness.

  As described above, the curve indicating the relationship between the luminance value of the difference image and the density and thickness of the contrast agent indicates various ways of bending depending on the quality of the difference image and the scattered radiation. Here, the subject in an actual clinical situation is a human body tissue and a contrast agent. Therefore, factors depending on the radiation quality can be regarded as the tube voltage of the X-ray tube and the body thickness of the subject. The scattered radiation changes depending on the distance between the subject and the X-ray detector. From the above, it is assumed that the curve showing the relationship between the concentration and the thickness of the contrast agent bends depending on the tube voltage, the body thickness, and the function of the scattered ray content (the ratio of scattered rays to direct rays). Can be. This will be described with reference to the following equations (1) to (3) and FIG.

FIG. 3 is a diagram for describing X-rays according to the first embodiment. In FIG. 3, the left side shows X-rays at the time of acquiring a mask image, and the right side shows X-rays at the time of acquiring a contrast image. For example, as shown in FIG. 3, when the X-ray emitted from the X-ray tube 12 is “I ₀ ”, the luminance value of the pixel corresponding to the blood vessel through which the contrast medium flows in the mask image is “I ₀ ”. This is based on the X-rays that have passed through the subject P and the scattered rays when “I ₀ ” has passed through the subject. That, X-rays reaching the X-ray detector 16 in a subject a contrast agent is not injected into the blood vessel "I _B" can be expressed as the following equation (1).

Here, “μ” in equation (1) indicates a linear attenuation coefficient, “L” indicates an X-ray transmission length (thickness), and “α” indicates a scattered radiation content. The subscript “b” indicates “body”, “w” indicates “water”, and “c” indicates “contrast”. For example, X-rays "I _B", as shown in equation (1), the body thickness of the subject and the linear attenuation coefficient "mu _b" in the body of the subject "L _b", and, vascular water (blood) The linear attenuation coefficient “μ _w ”, the “I ₀ ” affected by the blood vessel (contrast agent) thickness “L _c ”, and the scattered radiation “α × I ₀ × exp (−μ _b L _b )” It will be the sum. Here, blood is considered to have the same absorption characteristics as water.

Further, as shown in FIG. 3, the brightness value of the pixel corresponding to the blood vessel through which the contrast medium flows in the contrast image is “I ₀ ” with the X-rays transmitted through the subject P including the blood vessel into which the contrast medium has flowed. , “I ₀ ” and scattered radiation when passing through the inside P of the subject. That is, the X-ray “I _c ” that has reached the X-ray detector 16 in the subject P in which the contrast agent has been injected into the blood vessel can be represented by the following equation (2).

Here, “μ” in Expression (2) indicates a linear attenuation coefficient, “L” indicates an X-ray transmission length (thickness), and “α” indicates a scattered radiation content. The subscript “b” indicates “body”, and “c” indicates “contrast”. For example, as shown in equation (2), the X-ray “I _c ” is a linear attenuation coefficient “μ _b ” in the body of the subject, a body thickness “L _b ” of the subject, and a linear attenuation coefficient in the contrast agent. The sum of “μ _c ”, “I ₀ ” affected by the blood vessel (contrast agent) thickness “L _c ”, and scattered radiation “α × I ₀ × exp (−μ _b L _b )” Become.

  Then, when the difference image obtained by performing the log sub on the mask image and the contrast image is represented by using Expressions (1) and (2), the difference image can be represented by Expression (3) below. Here, “τ” in the equation (3) indicates a mass attenuation coefficient, and “ρ” indicates a concentration. That is, in equation (3), the linear attenuation coefficient “μ” is replaced with the mass attenuation coefficient “τ” and the concentration “ρ”.

As shown in Expression (3), when Expressions (1) and (2) are logarithmically converted and differentiated, the signal value (luminance value) “S” of the image is represented by the mass attenuation coefficient, the density, the thickness of the contrast agent, and It is determined by the scattered ray content. Here, since the mass attenuation coefficient “τ” in the equation (3) depends on the spectrum (energy) of the X-ray, the tube voltage of the X-ray tube and the body thickness of the subject are related. For example, irradiated from the X-ray tube 12 in FIG. 3 the spectrum of the "I _0" are those corresponding to the tube voltage, the spectrum of the "I _0" depending on whether it is to what extent the body thickness of the subject P Change is changing.

Here, when the luminance value in a region (for example, a catheter region or the like) where the concentration and the thickness of the contrast agent are known in the actually collected difference image is applied to Expression (3), the scattered radiation content rate at the time of collecting the difference image Only the body thickness of the subject becomes unknown. For example, in equation (3), the tube voltage related to “τ” is the tube voltage at the time of acquisition, and the concentration of the contrast agent “ρ _c ” is the concentration of the contrast agent injected into the catheter (before being diluted by blood). , The thickness of the contrast agent “L _c ” is the inner diameter of the catheter, and the concentration of water (blood) “ρ _w ” can be regarded as, for example, “1”. That is, the unknown factors in the equation (3) are the body thickness of the subject related to “τ” and the scattered radiation content rate “α”.

  Therefore, when estimating a correction curve based on a difference image captured in a state where a single concentration of the contrast agent is injected, the X-ray diagnostic apparatus 100 uses the region (where the concentration and the thickness of the contrast agent are known in the difference image) For example, the luminance value of the catheter region) is measured, the body thickness and the scattered radiation content satisfying the expression (3) are estimated with the measured luminance value, and the estimated body thickness and the scattered radiation content are used as the target. A correction curve indicating the relationship between the luminance value and the contrast agent density and thickness in the difference image of (1) is estimated. As described above, the unknown factors in the equation (3) are the body thickness of the subject and the scattered radiation content. That is, by determining the value of one factor, the value of the other factor is determined. In other words, the combination of the two factors that satisfy Expression (3) includes a value corresponding to a curve indicating the relationship between the luminance value and the contrast agent density and thickness in the actual difference image.

  Therefore, the X-ray diagnostic apparatus 100 extracts a combination of the body thickness and the scattered radiation content that satisfies the expression (3), and acquires a correction curve from a curve corresponding to the extracted combination. For example, the acquisition function 211 applies the brightness value of the catheter region and the known contrast agent concentration and thickness to Expression (3), extracts a plurality of combinations of the body thickness and the scattered radiation content, and sets the correction curve. get. Hereinafter, the processing of the acquisition function 211 when estimating a correction curve based on a difference image captured in a state where a contrast agent having a single density is injected will be described with reference to FIGS. 4 to 6. 4 to 6 are diagrams for explaining the correction curve estimation processing using a single-contrast contrast agent according to the first embodiment. 4 to 6, an example will be described in which a correction curve for correcting a luminance value of another region such as an artery is acquired using a luminance value of a catheter region.

  For example, when estimating a correction curve based on a difference image captured in a state where a single concentration of a contrast agent is injected, the acquisition function 211 performs, as shown in FIG. 4, a catheter region designated on the difference image. The luminance value in the region of interest R1 set to is measured. The region of interest R1 is set, for example, by the operator via the input circuit 22. Here, the acquisition function 211 is based on the luminance value at the position where the signal of the contrast agent is maximized in a predetermined region (region where the concentration and thickness of the contrast agent are known) and the scattered radiation and the subject at the time of acquiring the contrast image. And estimate the body thickness. For example, the acquisition function 211 measures the signal intensities of a plurality of pixels along the center of the catheter in the region of interest R1, and uses the highest value among the measured signal intensities.

  FIG. 5 shows the relationship between the cross-section of the catheter and the signal based on the contrast agent in the catheter. For example, when X-rays are applied to a cylindrical catheter, as shown in FIG. 5, the X-rays are applied not only to the thickest portion of the catheter but also to the thinner portion. . At this time, the signal based on the contrast agent indicates a signal intensity having a peak at the thickest part. That is, by measuring the signal intensity of the pixel corresponding to the center of the catheter, the thickness of the contrast agent becomes the inner diameter of the catheter, and the luminance value at the thickest part can be measured. Furthermore, since the thickest part in the catheter does not always coincide with the pixel, the acquisition function 211 measures the signal intensity for a plurality of pixels along the center of the catheter in the region of interest R1, and obtains the highest signal. Use values. That is, the acquisition function 211 applies the luminance value corresponding to the highest signal intensity to the expression (3) to estimate the scattered radiation content and the body thickness. Note that the concentration of the contrast agent and the inner diameter of the catheter may be input by the operator via the input circuit 22, but may be obtained from management information using a barcode, for example. You may. At present, contrast agents and catheters used in interventional treatment and the like are often managed using barcodes, and the acquisition function 211 obtains the concentration of the contrast agent currently used and the inner diameter of the catheter from this management information. Can also be obtained.

  As described above, when the brightness value of the catheter region in the difference image, the contrast agent concentration, and the thickness are obtained, the obtaining function 211 applies the obtained value to the above equation (3). Then, the acquisition function 211 extracts a combination of the scattered radiation content and the body thickness satisfying the relationship between the acquired luminance value, the contrast agent concentration, and the thickness in Expression (3), and from the curve corresponding to the extracted combination. Get the correction curve. For example, as shown in FIG. 6A, the acquisition function 211 shows “signal intensity (brightness value)” on the vertical axis and “contrast agent density × thickness (mg / ml × cm)” on the horizontal axis. The obtained values are plotted on the indicated graph, and a curve passing through the plotted points is extracted.

For example, if the concentration of the contrast agent is “370 (mg / ml)”, the inner diameter of the catheter is “2 mm”, and the signal intensity on the difference image is “0.257”, the acquisition function 211 as shown in FIG. 6 (a), satisfying the relationship of formula (3) (scattered radiation content, body thickness) a combination of _{(α1, L b 1),} (α2, L b 2), (α3, L _b 3), to extract the (α4, L _b 4) and (α5, L _b 5). Then, the acquisition function 211 applies the extracted combination of (scattered radiation content rate, body thickness) to the equation (3), and changes the value of “contrast agent concentration × thickness” to obtain a curve corresponding to each combination. To get. For example, the acquisition function 211 changes the value of “contrast agent concentration × thickness” by applying (α1, L _b 1) to equation (3), thereby obtaining (α1, L) shown in FIG. _b Obtain the curve of 1). Similarly, the acquisition function 211 acquires a curve for each combination.

Then, the acquisition function 211 acquires a correction curve based on the acquired curve. Here, the acquisition function 211 estimates the scattered radiation and the body thickness to be clinically possible values, and acquires a correction curve based on the curve corresponding to the estimated scattered radiation and the body thickness. For example, the acquisition function 211, as shown in FIG. 6 (B), (scattered radiation content, body thickness) a combination of _{(α1, L b 1),} (α2, L b 2), (α3, L b 3), corresponding to the combination of (alpha 4, L _b 4) and (.alpha.5, among L _b 5), the actual value that can be taken as the body thickness of the subject "10cm", "20cm" and "30cm" The candidate curve to be extracted is extracted. Then, the obtaining function 211 obtains a correction curve as shown in FIG. 6C by averaging the extracted candidate curves, for example.

As an example, the acquisition function 211 corresponds to (α, L _b ) = (0.82, 10 cm), (0.66, 20 cm), (0.53, 30 cm) shown in FIG. A quintic function “ρ _c × L _c = 2317 × S ⁵ −2912 × S ⁴ + 1610 × S ³ −134 × S ² +255” obtained by averaging the candidate curves to be obtained is acquired as a correction curve.

  Returning to FIG. 1, the correction function 212 corrects the contrast image using the correction information acquired by the acquisition function 211. Specifically, the correction function 212 corrects the luminance value of the pixel in the contrast image using the correction curve. FIG. 7 is a diagram schematically illustrating processing by the correction function 212 according to the first embodiment.

  For example, as shown in FIG. 7, the correction function 212 calculates a corresponding value of “density × thickness” by applying a luminance value (signal intensity) of a pixel in an artery to a correction curve. Then, the correction function 212 corrects the value in the pixel of the artery by replacing the luminance value in the artery with the calculated value. As a result, the luminance value in the difference image can be corrected to a value that accurately reflects “contrast agent density × thickness”, and for example, perfusion measurement in interventional treatment can be performed with high accuracy.

  Here, the correction function 212 can perform a correction process on an arbitrary region in the difference image. For example, the correction function 212 can correct the entire image by replacing the luminance values of all the pixels in the difference image with the values of “density × thickness”. Further, the correction function 212 can partially correct the image by replacing the luminance value of the pixel in a predetermined area in the difference image with a value of “density × thickness”. The predetermined area in the difference image includes, for example, an area (a blood vessel, a tissue, or the like) into which a contrast agent flows.

  As described above, by correcting the luminance value of the difference image, measurement of perfusion in interventional treatment and the like can be performed with high accuracy. FIG. 8 is a diagram illustrating an example of a case where the correction processing according to the first embodiment is performed. FIG. 8 shows a case where the luminance value of each pixel in the X-ray image (frame) collected over time after the injection of the contrast agent is corrected by the above-described correction. FIG. 8 shows a TDC (Time Density Curve) of a predetermined pixel before and after correction in which a horizontal axis indicates a frame and a vertical axis indicates a signal intensity. As shown in FIG. 8, by performing the correction, the range of the signal intensity of TDC is widened, and the difference in the contrast agent concentration can be reflected by the difference in the signal intensity.

  As described above, the X-ray diagnostic apparatus 100 according to the first embodiment performs the correction process of the luminance value and the contrast agent concentration using only the difference image. Here, when the inner diameter of the catheter is used as the thickness of the contrast agent, it is required that the longitudinal direction of the catheter is orthogonal to the X-ray irradiation direction (image projection direction). That is, when the catheter is not orthogonal (inclined) to the projection direction, the thickness of the contrast agent is not the inner diameter of the catheter but the thickness in the inclined projection direction.

  Therefore, in the X-ray diagnostic apparatus 100 according to the first embodiment, the calculation function 213 determines whether the catheter is tilted, and calculates the thickness of the contrast agent in the projection direction when the catheter is tilted. . Specifically, the calculation function 213 calculates the thickness of the contrast agent in the projection direction based on the angle between the longitudinal direction of the catheter and the projection direction. FIG. 9 is a diagram illustrating an example of a process performed by the calculation function 213 according to the first embodiment. For example, when the catheter having an inner diameter of “2 mm” shown in FIG. 9A is inclined by “45 °” with respect to the X-ray irradiation direction (projection direction) as shown in FIG. 9B. The calculation function 213 calculates the catheter thickness “2√2” in a direction parallel to the projection direction, and sets the calculated “2√2” as the thickness of the contrast agent.

  Here, the angle between the longitudinal direction of the catheter and the projection direction (the inclination of the catheter) can be calculated by biplane imaging or by using a distance marker attached to the catheter. For example, by biplane imaging, in addition to a difference image collected from a target direction, a difference image is collected from a direction orthogonal thereto. The calculation function 213 measures the inclination of the catheter in the vertical direction (or the horizontal direction) included in the difference image collected from the orthogonal direction, and calculates the inclination of the catheter in the difference image collected from the target direction. And

Alternatively, the calculation function 213 calculates the inclination of the catheter based on a change in the distance marker attached to the catheter at a predetermined interval. For example, when using a catheter with markers at “10 mm” intervals, the calculation function 213 determines that the catheter is not tilted when the interval between the distance markers included in the mask image is an interval corresponding to “10 mm”. Is determined. On the other hand, when the interval between the distance markers included in the mask image is not the interval corresponding to “10 mm”, the calculation function 213 determines that the catheter is tilted, and calculates the tilt of the catheter. As an example, when the interval between the distance markers included in the mask image is an interval corresponding to “8 mm”, the calculation function 213 calculates the inclination of the catheter “θ” = “cos ⁻¹ 8/10”. .

  Then, the calculation function 213 calculates the thickness of the contrast agent using the calculated inclination (angle) of the catheter. The acquisition function 211 acquires a correction curve by applying the thickness of the contrast agent calculated by the calculation function 213 to the above-described equation (3).

  As described above, the X-ray diagnostic apparatus 100 estimates a correction curve based on a difference image captured in a state where a single concentration of a contrast agent is injected, and uses the estimated correction curve to determine a luminance value of the difference image. Can be corrected. Here, when estimating a correction curve based on a difference image captured in a state where a single concentration of a contrast medium is injected, as described above, the body thickness and the scattered radiation of the subject satisfying the expression (3) are used. A combination with the content is extracted, and a correction curve is obtained from a curve corresponding to the extracted combination. However, by using a plurality of difference images taken in a state where the concentration of the contrast agent is changed, the body thickness and the scattered radiation content of the subject can be determined, and the determined body thickness and the scattered radiation content can be determined. A correction curve can be obtained from the ratio.

  That is, in a plurality of difference images based on different contrast agent concentrations, the luminance value at the same position is measured, and the measured luminance value and each contrast agent concentration and thickness are determined by a factor unknown in equation (3). The body thickness and the scattered radiation content of a certain subject are calculated, and a correction curve can be calculated using the calculated body thickness and the scattered radiation content of the subject. The X-ray diagnostic apparatus 100 according to the first embodiment changes the concentration of a contrast agent injected into a subject, and acquires a difference image at a different contrast agent concentration. Then, the X-ray diagnostic apparatus 100 acquires a correction curve from the acquired plural difference images and corrects the luminance value of the difference image. Hereinafter, an example of calculating a correction curve based on a plurality of difference images captured by changing the density of the contrast agent will be described.

  When calculating a correction curve based on a plurality of difference images captured by changing the concentration of the contrast agent, the X-ray diagnostic apparatus 100 first controls the injector 30 to change the contrast agent concentration. Specifically, the processing circuit 21 controls the concentration of the contrast agent injected into the subject by transmitting a signal for changing the contrast agent concentration to the injector 30. Here, the injector 30 changes the concentration of the contrast agent by injecting different concentrations of the contrast agent, or adds water so as to have a predetermined dilution ratio with respect to the single concentration of the contrast agent. For example, the concentration of the contrast agent can be changed.

  FIG. 10A and FIG. 10B are diagrams for explaining the contrast agent injected by the injector 30 according to the first embodiment. For example, as shown in FIG. 10A, the injector 30 is connected to a bottle of a contrast agent having a concentration of “300 (mg / ml)” and a bottle of a contrast agent having a concentration of “150 (mg / ml)”. The contrast agent concentration is changed by switching the contrast agent to be injected according to the received signal. For example, the processing circuit 21 controls to inject a contrast agent having a concentration of “300 (mg / ml)” first, and controls to inject a contrast agent having a concentration of “150 (mg / ml)” after a few seconds. .

  Further, for example, as shown in FIG. 10B, the injector 30 is connected to a bottle of a contrast agent having a concentration of “300 (mg / ml)” and a bottle of water (saline), and to a signal received from the processing circuit 21. Accordingly, the contrast medium concentration is changed by diluting the contrast medium with water. For example, the processing circuit 21 controls to inject the contrast agent having a concentration of “300 (mg / ml)” first, and after a few seconds, the contrast agent diluted with “contrast agent: water = 1: 1” (concentration “150”) (Mg / ml) "contrast medium). Here, the dilution of the contrast agent is performed, for example, by flowing the same amount of the contrast agent and water from the bottle of the contrast agent and the bottle of water, respectively, and stirring the mixture.

  Here, the concentration of the contrast agent injected via the catheter can be arbitrarily changed. FIGS. 11A and 11B are diagrams illustrating an example of a change in the contrast agent concentration according to the first embodiment. 11A and 11B, the vertical axis shows the contrast agent concentration at the catheter position, and the horizontal axis shows time. For example, as illustrated in FIG. 11A, the processing circuit 21 changes the contrast agent concentration at the catheter position at a concentration of “300 (mg / ml)” for a certain period of time, and then changes the concentration of the contrast agent at a concentration of “150 (mg / ml)”. The transition can be controlled. Further, for example, as shown in FIG. 11B, the processing circuit 21 gradually reduces the contrast agent concentration at the catheter position from the concentration “300 (mg / ml)” to the concentration “150 (mg / ml)”. Can be controlled as follows.

  As described above, the processing circuit 21 controls the injector 30 to change the concentration of the contrast agent injected into the subject. Then, the X-ray diagnostic apparatus 100 captures an X-ray image with time while changing the concentration of the contrast agent, and collects a plurality of difference images. To give an example, for example, the processing circuit 21 first injects a physiological saline solution into the catheter to capture a mask image, and thereafter, a contrast agent having a concentration of “300 (mg / ml)” and a concentration of “150 (mg) / Ml) "is injected stepwise and contrast images at each concentration are taken. Then, the processing circuit 21 generates a plurality of difference images by subtracting each of the captured contrast images and the mask image.

  Here, the processing circuit 21 can store the plurality of difference images generated by the image processing circuit 26 in association with the injection information. For example, the processing circuit 21 injects the physiological saline solution, the contrast medium is injected and the concentration of “300 (mg / ml)” is injected, and the concentration is “150 (mg / ml). )) Is stored in the header of DICOM (Digital Imaging and Communication in Medicine) and stored in the storage circuit 25. Here, for example, when performing the measurement of perfusion in interventional treatment, after injecting a physiological saline solution, injecting a high-contrast contrast agent and collecting Perfusion data, a low-concentration solution is obtained in the last about 1 second. Inject contrast agent. At this time, the imaging may be performed for the thin contrast agent until it flows out to the tip of the catheter, and the imaging may be terminated when the thin contrast agent enters the blood vessel.

  As described above, when the difference images based on the contrast agents having the plurality of densities are respectively collected, the acquisition function 211 determines the respective concentrations of the contrast agents having a plurality of luminance values corresponding to the two or more contrast agent concentrations in the contrast image. Based on the thickness of the contrast agent in the projection direction, scattered radiation at the time of acquiring the contrast image and correction information of the luminance value of the contrast image according to the body thickness of the subject are acquired. For example, the acquisition function 211 acquires a contrast image based on each concentration of the contrast agent in a predetermined area and the thickness of the contrast agent in the projection direction in each of the contrast images acquired using two or more concentrations of the contrast agent. The correction information of the brightness value of the contrast image according to the scattering light at the time and the body thickness of the subject is acquired. That is, the acquisition function 211 is such that the curve indicating the relationship between the brightness value in the contrast image and the density and thickness of the contrast agent indicates the relationship between each brightness value and the concentration and thickness of the contrast agent in a predetermined region of each contrast image. The scattered radiation and the body thickness when satisfied are calculated, and a correction curve is acquired based on the calculated scattered radiation and the curve corresponding to the body thickness.

  For example, the acquisition function 211 measures the brightness value at the same position in a plurality of difference images based on different contrast agent concentrations, and determines the unknown value in Expression (3) from the measured brightness value and each contrast agent concentration and thickness. The body thickness of the subject and the scattered radiation content, which are the factors, are calculated, and a correction curve is calculated using the calculated body thickness of the subject and the scattered radiation content. Here, the acquisition function 211 can acquire the density of the contrast agent in each difference image collected by the image processing circuit 26, for example, from the injection information stored in the DICOM header.

  FIG. 12 is a diagram for explaining a process of calculating a correction curve using a plurality of density contrast agents according to the first embodiment. Here, in FIG. 12, a difference image captured in a state where a contrast agent having a concentration of “300 (mg / ml)” is injected into the catheter, and a contrast agent having a concentration of “150 (mg / ml)” are injected into the catheter. A case where a correction curve is calculated from a difference image captured in this state will be described. For example, as illustrated in FIG. 12, the acquisition function 211 may be configured to obtain a brightness value in the region of interest R <b> 1 of the catheter of a difference image captured in a state where a contrast agent having a concentration of “300 (mg / ml)” is injected into the catheter. A luminance value at the same position (region of interest R1 of the catheter) of the difference image captured in a state where “150 (mg / ml)” of the contrast agent is injected into the catheter is measured.

  Then, the acquisition function 211 acquires two expressions in which the luminance value in each difference image and each concentration and thickness of the contrast agent are applied to the above-described expression (3), and an unknown factor is obtained from the acquired two expressions. The body thickness and the scattered radiation content of a certain subject are calculated. Thereby, the acquisition function 211 can determine the body thickness and the scattered radiation content of the subject when the difference image is collected, and calculate the correction curve according to the determined body thickness and the scattered radiation content of the subject. Can be obtained. That is, the acquisition function 211 can acquire a correction curve passing through two measured luminance values based on the determined body thickness and scattered radiation content of the subject, as shown in FIG.

  As a position (pixel) at which the luminance value is measured, a position at which the signal of the contrast agent is maximized is selected in a manner similar to the above-described processing. That is, the acquisition function 211 measures the luminance value at the position where the thickness of the contrast agent is maximum. When the inner diameter of the catheter is used as the thickness of the contrast agent, the calculation function 213 calculates the thickness of the contrast agent in the projection direction based on the angle between the longitudinal direction of the catheter and the projection direction, as in the above-described processing. Is calculated. The correction function 212 executes a correction process using a correction curve calculated by a plurality of contrast agents, similarly to a correction process using a correction curve estimated by a single concentration of a contrast agent. For example, the correction function 212 uses the correction curve shown in FIG. 12 to obtain the brightness value of the difference image captured in a state where the contrast agent having the concentration of “300 (mg / ml)” is injected into the catheter, or the density “150 ( mg / ml) of the difference image captured in a state where the contrast agent is injected into the catheter.

  Next, processing of the X-ray diagnostic apparatus 100 according to the first embodiment will be described with reference to FIGS. FIG. 13 is a flowchart illustrating a procedure of a correction process using a correction curve estimated with a single-density contrast agent according to the first embodiment. FIG. 14 is a flowchart illustrating a procedure of a correction process using a correction curve estimated by a plurality of contrast agents according to the first embodiment.

  Step S101 shown in FIG. 13 is a step executed by the input circuit 22. In step S101, the input circuit 22 receives an operation of setting a region (for example, a catheter region or the like) where the concentration and thickness of the contrast agent are known from the operator. Step S102 is a step in which the processing circuit 21 reads a program corresponding to the acquisition function 211 from the storage circuit 25 and executes the program. In step S102, the processing circuit 21 acquires the contrast agent concentration and the thickness in the region.

  Steps S103 and S104 are steps in which the processing circuit 21 reads a program corresponding to the calculation function 213 from the storage circuit 25 and executes the program. In step S103, the processing circuit 21 determines whether the catheter is tilted. Here, when it is determined that the catheter is tilted (Yes at Step S103), at Step S104, the processing circuit 21 corrects the thickness based on the angle. On the other hand, if it is determined that the catheter is not tilted (No at Step S103), the processing circuit 21 does not execute Step S104.

  Steps S105 and S106 are steps in which the processing circuit 21 reads a program corresponding to the acquisition function 211 from the storage circuit 25 and executes the program. In step S105, the processing circuit 21 estimates a candidate curve from the luminance value in the region, the contrast agent concentration, and the thickness. Then, in step S106, the processing circuit 21 derives a correction curve from the candidate curve by, for example, averaging the candidate curve.

  Step S107 is a step in which the processing circuit 21 reads a program corresponding to the correction function 212 from the storage circuit 25 and executes the program. In step S107, the processing circuit 21 corrects the contrast image using the correction curve.

  Step S201 shown in FIG. 14 is a step executed by the input circuit 22. In step S101, the input circuit 22 receives an operation of setting a region (for example, a catheter region or the like) where the concentration and thickness of the contrast agent are known from the operator. Step S202 is a step in which the processing circuit 21 reads a program corresponding to the acquisition function 211 from the storage circuit 25 and executes the program. In step S202, the processing circuit 21 acquires the contrast agent concentration and the thickness in the region.

  Steps S203 and S204 are steps in which the processing circuit 21 reads a program corresponding to the calculation function 213 from the storage circuit 25 and executes the program. In step S103, the processing circuit 21 determines whether the catheter is tilted. Here, when it is determined that the catheter is tilted (Yes at Step S203), at Step S204, the processing circuit 21 corrects the thickness based on the angle. On the other hand, when it is determined that the catheter is not tilted (No at Step S203), the processing circuit 21 does not execute Step S204.

  Steps S205 to S207 are steps in which the processing circuit 21 reads a program corresponding to the acquisition function 211 from the storage circuit 25 and executes the program. In step S205, the processing circuit 21 injects the first concentration of the contrast agent, and measures the luminance value in the region. Then, in step S206, the processing circuit 21 injects the second concentration of the contrast agent, and measures the luminance value in the region. Further, in step S207, the processing circuit 21 derives a correction curve based on the luminance value in the area of the first density contrast medium, the luminance value in the area of the second density contrast medium, and the thickness of the area. I do.

  Step S208 is a step in which the processing circuit 21 reads a program corresponding to the correction function 212 from the storage circuit 25 and executes the program. In step S208, the processing circuit 21 corrects the contrast image using the correction curve.

  As described above, according to the first embodiment, the acquisition function 211 determines the concentration of each of the contrast agent and the contrast agent in a predetermined region in each of the contrast images collected using the contrast agents having two or more concentrations. Based on the thickness in the projection direction, scattered radiation at the time of acquiring the contrast image and correction information of the luminance value of the contrast image corresponding to the body thickness of the subject are acquired. The correction function 212 corrects the contrast image using the correction information. Therefore, the X-ray diagnostic apparatus 100 according to the first embodiment can perform correction using only the contrast image, and can easily perform correction of the contrast image. Further, since the correction can be performed using only the contrast image, the correction can also be performed on the collected contrast image.

  Further, according to the first embodiment, the acquisition function 211 determines that the curve indicating the relationship between the luminance value in the contrast image and the density and thickness of the contrast agent is different from the luminance value and the contrast agent in a predetermined area of each contrast image. Is calculated in the case where the relationship between each of the density and the thickness is satisfied, and a correction curve is obtained based on a curve corresponding to the calculated scattered radiation and the body thickness. The correction function 212 corrects the luminance value of the pixel in the contrast image using the correction curve. Therefore, the X-ray diagnostic apparatus 100 according to the first embodiment performs the correction in consideration of the scattered radiation and the body thickness, which are factors that change the curve indicating the relationship between the brightness value of the contrast image, the contrast agent concentration, and the thickness. To be able to do.

  Further, according to the first embodiment, the acquisition function 211 is configured to determine the scattered radiation and the body thickness of the subject based on the brightness value at the position where the signal of the contrast agent is maximum in a predetermined area. Is estimated. Therefore, the X-ray diagnostic apparatus 100 according to the first embodiment can acquire a more accurate correction curve.

  In addition, for example, when a correction curve is estimated using a single concentration of a contrast agent, it is possible to perform correction using a highly accurate portion of the correction curve. For example, as shown in FIG. 6B, when a plurality of candidate curves indicating the relationship between the brightness value and the contrast agent concentration and the thickness in the difference image are extracted, the catheter brightness value and the contrast agent concentration and the thickness are extracted from the curve. A portion where “density × thickness” is low from the point where the relationship is plotted draws almost the same curve among a plurality of curves. On the other hand, a portion where “density × thickness” is high from the point where the relationship between the luminance value of the catheter and the contrast agent concentration and the thickness is plotted indicates a different curve between the curves.

  That is, when the correction curve is calculated by averaging the candidate curves, the error caused by averaging is lower in a portion lower than the point where the relationship between the catheter brightness value and the contrast agent concentration and the thickness is plotted, and the error is higher in the higher portion. Becomes larger. Therefore, when performing the correction processing, it is possible to perform the correction with higher accuracy by using a curve in a portion lower than the plotted point in the correction curve. Therefore, by plotting the first plotted point so that the signal intensity is higher, the portion of the correction curve lower than the plotted point is increased, and the contrast image can be corrected with higher accuracy.

  Further, according to the first embodiment, the predetermined area is an area of the catheter included in the contrast image, and the acquisition function 211 determines the concentration and thickness of the contrast agent in the predetermined area of each contrast image as a catheter. The concentration of the contrast agent to be injected with varying concentrations via the inner diameter of the catheter is used. Therefore, the X-ray diagnostic apparatus 100 according to the first embodiment makes it possible to easily obtain the concentration and thickness of the contrast agent.

  Further, according to the first embodiment, the calculation function 213 calculates the thickness of the contrast agent in the projection direction based on the angle between the longitudinal direction of the catheter and the projection direction. The acquisition function 211 uses the thickness of the contrast agent calculated by the calculation function 213 as the thickness of the contrast agent in a predetermined area. Therefore, the X-ray diagnostic apparatus 100 according to the first embodiment enables accurate correction processing even when the catheter is tilted.

  Further, according to the first embodiment, the calculation function 213 determines whether the longitudinal direction and the projection direction of the catheter are based on a contrast image of the catheter collected from at least two directions or a distance marker provided on the catheter. Calculate the angle to make. Therefore, the X-ray diagnostic apparatus 100 according to the first embodiment makes it possible to easily calculate the inclination of the catheter.

(Second embodiment)
In the above-described embodiment, a case has been described in which the scattered radiation content rate and the body thickness are estimated from the luminance value and the concentration and the thickness of the contrast agent to obtain a correction curve. In the second embodiment, a case will be described in which a correction curve is stored in advance, and a correction curve is selected from the luminance value and the density and thickness of the contrast agent. Note that the X-ray diagnostic apparatus 100 according to the second embodiment is different from the X-ray diagnostic apparatus 100 according to the first embodiment in that the information stored by the storage circuit 25 and the processing content by the acquisition function 211 are different. different. Hereinafter, these will be described.

  FIG. 15 is a diagram schematically illustrating information stored in the storage circuit 25 according to the second embodiment. For example, as shown in FIG. 15, the storage circuit 25 stores correction curves (or candidate curves) calculated using various concentrations of contrast agents. For example, as the contrast agent shown in FIG. 15, those having a constant thickness and various concentrations are prepared. Then, by imaging the contrast medium under various conditions, a correction curve set as shown in FIG. 15 is obtained, and the storage circuit 25 stores the obtained correction curve set. For example, a correction curve is obtained by variously changing conditions such as a tube voltage and a thickness of a subject, and stored in the storage circuit 25.

  The acquisition function 211 is a method for obtaining a luminance value and a contrast in a predetermined region from among a plurality of curves indicating the relationship between the luminance value in the contrast image and the concentration and the thickness of the contrast agent preset for each condition of the scattered radiation and the body thickness. A curve satisfying the relationship between the agent concentration and the thickness is extracted, and a correction curve is obtained based on the extracted curve. For example, when the brightness value of the catheter region, the contrast agent concentration, and the thickness are obtained, a curve satisfying the obtained values is obtained from the correction curve set. Here, when a plurality of curves are obtained, the obtained curves may be averaged.

  As described above, according to the second embodiment, the acquisition function 211 includes a plurality of functions indicating the relationship between the brightness value and the concentration and the thickness of the contrast agent in the contrast image set in advance for each condition of the scattered radiation and the body thickness. Out of the curves, a curve that satisfies the relationship between the luminance value and the density and thickness of the contrast agent in a predetermined area is extracted, and a correction curve is obtained based on the extracted curve. The correction function 212 corrects the luminance value of the pixel in the contrast image using the correction curve. Therefore, the X-ray diagnostic apparatus 100 according to the second embodiment makes it possible to execute correction of a contrast image by simple processing.

(Third embodiment)
In the above-described embodiment, the catheter region is used as the region where the concentration and the thickness of the contrast agent are known, and by further changing the contrast agent concentration in the catheter, a plurality of brightness values corresponding to two or more contrast agent concentrations are obtained. The case of acquisition has been described. In the third embodiment, a case will be described in which a plurality of luminance values corresponding to two or more contrast agent densities are acquired by another method. The X-ray diagnostic apparatus 100 according to the third embodiment differs from the X-ray diagnostic apparatuses 100 according to the first and second embodiments in the processing performed by the acquisition function 211. Hereinafter, this will be described.

  For example, the acquisition function 211 is based on a luminance value in a contrast image of a medical device indicating a signal corresponding to a known contrast agent concentration and thickness in the contrast image, and based on the scattered radiation at the time of collection of the contrast image and the body thickness of the subject. The correction information of the luminance value of the contrast image according to the acquired information is acquired. For example, the acquisition function 211 can acquire correction information based on a brightness value of a marker provided on the catheter, a device inserted into the aorta, and the like, in addition to the contrast agent in the catheter. Here, a marker provided in the catheter and a device to be inserted into the aorta are associated with a predetermined contrast agent concentration and thickness in advance. That is, the marker and the like are provided so as to have the same density (shade) as the predetermined contrast agent concentration and have a predetermined thickness. Thereby, the marker provided in the catheter and the medical device inserted into the aorta have a known contrast agent concentration and thickness, and the correction curve indicating the relationship between the luminance value and the contrast agent concentration and the thickness in the contrast image. It can be used for calculation.

  The calculation of the correction curve using the marker provided on the catheter or the medical device inserted into the aorta may be performed when used together with the above-described contrast agent in the catheter, or when used alone. There may be. That is, one of a plurality of brightness values corresponding to two or more contrast agent concentrations may be obtained from a contrast agent in a catheter, and the other may be obtained from a marker or the like, and may correspond to two or more contrast agent concentrations All the plurality of luminance values to be obtained may be obtained from a marker or the like. FIG. 16 is a diagram illustrating an example of a process performed by the acquisition function 211 according to the third embodiment. FIG. 16 shows an example in which two brightness values corresponding to two contrast agent concentrations are acquired from a marker attached to a catheter.

  For example, as shown in FIG. 16, a catheter is provided with a marker 1 and a marker 2. Here, the markers 1 and 2 are provided so as to have the same density (shade) as the known contrast agent concentration. For example, the marker 1 is provided so as to have the same concentration as the first contrast agent concentration, and the marker 2 is so provided as to have the same concentration as the second contrast agent concentration which is higher than the first contrast agent concentration. Provided. Further, the markers 1 and 2 are provided with a predetermined thickness. When a procedure is performed using a catheter to which the markers 1 and 2 are attached and a contrast image is collected, the acquisition function 211 acquires each contrast agent concentration and thickness corresponding to the markers 1 and 2 respectively. . Then, the acquisition function 211 acquires a correction curve using the acquired contrast agent concentrations and thicknesses and the luminance values of the markers 1 and 2 in the contrast image.

  As described above, the X-ray diagnostic apparatus 100 according to the present embodiment can also correct a contrast image without using a contrast agent concentration in a catheter. Note that the acquisition function 211 can also acquire correction information based on the luminance value of the contrast agent in another catheter inserted in a different location from the first inserted catheter. That is, a plurality of brightness values corresponding to two or more contrast medium concentrations can be obtained by injecting different concentrations of contrast medium from different catheters without changing the contrast medium concentration in the same catheter. it can.

(Fourth embodiment)
The first to third embodiments have been described above, but may be implemented in various different forms other than the first to third embodiments described above.

  In the first embodiment described above, the case where the catheter region is used as the region where the contrast agent concentration and the thickness are known has been described as an example. However, the embodiment is not limited to this. For example, a case where three-dimensional image data is used may be used. For example, when performing interventional treatment, three-dimensional image data is often acquired in advance. Therefore, the thickness can be obtained from the three-dimensional image data, and the obtained thickness can be used. For example, the target blood vessel included in the image data acquired in advance using the contrast agent and the blood vessel in the difference image are aligned and overlapped, and the thickness of the blood vessel in the projection direction in the difference image is set to the three-dimensional image. By using the measurement, the thickness of the contrast agent in the difference image can be obtained. Here, the concentration before dilution may be used as the concentration of the contrast agent by injecting the contrast agent at the position where the thickness of the blood vessel is measured.

  In the first embodiment described above, a case has been described in which the density information of each contrast agent in a plurality of difference images is acquired from the injection information stored in the DICOM header. However, the embodiment is not limited to this. For example, a case where the timing at which the density of the contrast agent changes based on the luminance value of the difference image may be determined. Specifically, the acquisition function 211 acquires only the information of the density of the injected contrast agent, and determines the density of the contrast agent in each difference image based on a change in the luminance value of the difference image. For example, the obtaining function 211 obtains a luminance value in a predetermined region with time, and sets each of the luminance values before and after the obtained luminance value changes beyond a predetermined threshold value to a luminance based on a contrast agent having a different density. Judge as a value.

  In the above-described embodiment, the case where the X-ray diagnostic apparatus performs each process has been described as an example. However, the embodiment is not limited to this. It may be. In such a case, the storage circuit 25 and the processing circuit 21 described above are included in the image processing apparatus, and execute the respective processes described above.

  Each component of each device illustrated in the first embodiment is a functional concept and does not necessarily need to be physically configured as illustrated. That is, the specific form of distribution / integration of each device is not limited to the one shown in the figure, and all or a part thereof may be functionally or physically distributed / arbitrarily divided into arbitrary units according to various loads and usage conditions. Can be integrated and configured. Further, all or any part of each processing function performed by each device can be realized by a CPU and a program analyzed and executed by the CPU, or can be realized as hardware by wired logic.

  As described above, according to the X-ray diagnostic apparatus of at least one embodiment, it is possible to easily correct a contrast image.

  Although several embodiments of the present invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and changes 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 equivalents thereof.

21 processing circuit 25 storage circuit 100 X-ray diagnostic apparatus 211 acquisition function 212 correction function 213 calculation function

Claims (14)

Scattering during collection of the contrast image based on each of the two or more contrast agent concentrations, a plurality of brightness values in the contrast image corresponding to the respective concentrations , and the thickness of the contrast agent in the projection direction. An acquisition unit that acquires correction information of the luminance value of the contrast image according to the line and the body thickness of the subject,
Using the correction information, a correction unit that corrects the contrast image,
Equipped with a,
The acquisition unit is a curve indicating the relationship between the brightness value and the density and thickness of the contrast agent in the contrast image, the plurality of brightness values corresponding to the respective densities and the respective densities and the thickness of the contrast agent. Calculate the scattered radiation and body thickness when satisfying the relationship, to obtain a correction curve based on the calculated scattered radiation and a curve corresponding to the body thickness,
Wherein the correction unit is that to correct the luminance value of the pixel in the contrast image using the correction curve, the image processing apparatus. Scattering during collection of the contrast image based on each of the two or more contrast agent concentrations, a plurality of brightness values in the contrast image corresponding to the respective concentrations, and the thickness of the contrast agent in the projection direction. An acquisition unit that acquires correction information of the luminance value of the contrast image according to the line and the body thickness of the subject,
Using the correction information, a correction unit that corrects the contrast image,
With
The acquisition unit corresponds to each of the concentrations from among a plurality of curves indicating a relationship between the brightness value and the concentration and the thickness of the contrast agent in the contrast image preset for each condition of the scattered radiation and the body thickness. wherein the plurality of luminance value and the extracted curve that satisfies the relationship between the thickness of the concentration and the contrast agent to obtain a correction curve based on the extracted curve,
Wherein the correction unit corrects the luminance value of the pixel in the contrast image using the correction curve, images processing device. Scattering during collection of the contrast image based on each of the two or more contrast agent concentrations, a plurality of brightness values in the contrast image corresponding to the respective concentrations, and the thickness of the contrast agent in the projection direction. An acquisition unit that acquires correction information of the luminance value of the contrast image according to the line and the body thickness of the subject,
Using the correction information, a correction unit that corrects the contrast image,
With
The acquisition unit, based on each concentration of the contrast agent in a predetermined region in each of the contrast images collected using two or more concentrations of the contrast agent and the thickness of the contrast agent in the projection direction, the contrast image wherein acquiring the correction information of the luminance values of the contrast image corresponding to the body thickness of the scattered radiation and the object at the time of collection, images processing device. The acquisition unit, based on said predetermined area smell Te maximum preparative name Ru Luminance value, the calculated scattered radiation during the acquisition of the contrast image and the subject's body thickness Prefecture, images according to claim 3 Processing equipment. The obtaining unit obtains a luminance value in the predetermined area with time, and sets the luminance values before and after the obtained luminance value changes beyond a predetermined threshold value, based on the contrast agent having different densities. determined as determines that the obtained brightness value is contrast images were collected respectively with contrast agents with different concentrations before and after the time of change exceeds a predetermined threshold value, the image processing according to claim 3 or 4 apparatus. The predetermined area is an area of the catheter included in the contrast image,
The acquisition unit, as each concentration and thickness of the contrast agent in a predetermined region of each of the contrast images, using the concentration of each of the contrast agent to be injected by changing the concentration through the catheter and the inner diameter of the catheter, Item 6. The image processing device according to any one of Items 3 to 5 . The concentration of the contrast agent is changed by injecting different concentrations of the contrast agent into the catheter, or water is added so as to have a predetermined dilution ratio with respect to a single concentration of the contrast agent. The image processing apparatus according to claim 6 , wherein the density is changed by the change. The image processing device according to claim 7 , wherein the contrast agent is injected so as to be gradually thinned in the catheter. Based on an angle between the longitudinal direction of the catheter and the projection direction, further comprising a calculating unit that calculates the thickness of the contrast agent in the projection direction,
The acquisition unit, as the thickness of the contrast agent in the predetermined area, using the thickness of the contrast agent which is calculated by the calculation unit, the image processing apparatus according to any one of claims 6-8. The calculating unit, based on a contrast image of the catheter collected from at least two directions, or a distance marker provided on the catheter, calculates an angle between the longitudinal direction of the catheter and the projection direction. Item 10. The image processing device according to Item 9 . The acquisition unit is based on a luminance value in the contrast image of the medical device indicating a signal corresponding to a known contrast agent concentration and thickness in the contrast image, based on scattered radiation at the time of collection of the contrast image and body thickness of the subject. wherein acquiring the correction information of the luminance values of the contrast image corresponding to the image processing apparatus according to claim 1 or 2. A collection unit that collects a contrast image including a plurality of brightness values corresponding to two or more contrast agent concentrations,
At the time of collecting the contrast image, based on each of the two or more contrast agent concentrations, a plurality of brightness values in the contrast image corresponding to each of the concentrations, and the thickness of the contrast agent in the projection direction. An acquisition unit that acquires correction information of the luminance value of the contrast image according to the scattered radiation and the body thickness of the subject,
Using the correction information, a correction unit that corrects the contrast image,
Equipped with a,
The acquisition unit is a curve indicating the relationship between the brightness value and the density and thickness of the contrast agent in the contrast image, the plurality of brightness values corresponding to the respective densities and the respective densities and the thickness of the contrast agent. Calculate the scattered radiation and body thickness when satisfying the relationship, to obtain a correction curve based on the calculated scattered radiation and a curve corresponding to the body thickness,
Wherein the correction unit, the correction curve you correct the luminance value of the pixel in the contrast image using, X-rays diagnostic apparatus. A collection unit that collects a contrast image including a plurality of brightness values corresponding to two or more contrast agent concentrations,
At the time of collecting the contrast image, based on each of the two or more contrast agent concentrations, a plurality of brightness values in the contrast image corresponding to each of the concentrations, and the thickness of the contrast agent in the projection direction. An acquisition unit that acquires correction information of the luminance value of the contrast image according to the scattered radiation and the body thickness of the subject,
Using the correction information, a correction unit that corrects the contrast image,
With
The acquisition unit corresponds to each of the concentrations from among a plurality of curves indicating a relationship between the brightness value and the concentration and the thickness of the contrast agent in the contrast image preset for each condition of the scattered radiation and the body thickness. Extract a curve that satisfies the relationship between the plurality of brightness values and the respective concentrations and the thickness of the contrast agent to obtain a correction curve based on the extracted curve,
The X-ray diagnostic apparatus, wherein the correction unit corrects a luminance value of a pixel in the contrast image using the correction curve. An acquisition unit configured to acquire a plurality of contrast images using two or more concentrations of the contrast agent,
Each density of the two or more contrast agent densities, corresponding to each density, a plurality of brightness values in the contrast image, and based on the thickness of the contrast agent in the projection direction, at the time of collection of the contrast image An acquisition unit that acquires correction information of the luminance value of the contrast image according to the scattered radiation and the body thickness of the subject,
Using the correction information, a correction unit that corrects the contrast image,
With
The acquisition unit is configured to generate the contrast image based on each concentration of the contrast agent in a predetermined region in each of the contrast images collected using the two or more contrast agents and the thickness of the contrast agent in a projection direction. An X-ray diagnostic apparatus for acquiring correction information of a luminance value of the contrast image according to scattered radiation at the time of collection and a body thickness of a subject.