X-ray image processing device, X-ray diagnostic device, method and program

Abstract

To improve the reproducibility of measurement of an index for evaluating the state of a subject.SOLUTION: An X-ray image processing apparatus of an embodiment includes a first acquisition part, a second acquisition part, a gain correction part, and an image generation part. The first acquisition part acquires a first X-ray image including a subject. The second acquisition part acquires a first measured values pertaining to the X-ray conditions of the first X-ray image, a second X-ray image without the subject, and a second measured values pertaining to the X-ray conditions of the second X-ray image. The gain correction part corrects the first X-ray image on the basis of the first measured value, the second X-ray image, and the second measured value. The image generation part generates an evaluation image to evaluate the state of the subject on the basis of the corrected image, which is the first X-ray image corrected by the gain correction part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The embodiments disclosed in the present specification and drawings relate to an X-ray image processing apparatus, an X-ray diagnostic apparatus, a method, and a program. [Background technology]

[0002] Dual-energy X-ray absorptiometry (DXA) is a well-known technique for generating evaluation images to assess the bone condition of a subject. DXA generates bone images that differentiate bones based on image data of the subject captured using X-rays of two different energies, and measures indices for assessing the bone condition of the subject, such as bone mineral density (BMD), based on the generated bone images.

[0003] Bone mineral density is an index used to diagnose osteoporosis and determine the effectiveness of therapeutic drugs, so highly reproducible measurements are required for such diagnosis and evaluation. However, X-ray generators have statistical output errors, making it difficult to achieve high-precision reproducibility in measuring indices used to evaluate the condition of a subject. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-245117 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-200071 [Patent Document 3] Japanese Patent Application Publication No. 2019-126581 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-169068 Summary of the Invention [Problem to be solved by the invention]

[0005] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to improve the reproducibility of measurements of indicators for evaluating the state of a subject. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0006] An X-ray image processing apparatus according to an embodiment includes a first acquisition unit, a second acquisition unit, a gain correction unit, and an image generation unit. The first acquisition unit acquires a first X-ray image including a subject. The second acquisition unit acquires first actual measurement values ​​related to X-ray conditions for the first X-ray image, a second X-ray image not including the subject, and second actual measurement values ​​related to X-ray conditions for the second X-ray image. The gain correction unit corrects the first X-ray image based on the first actual measurement values, the second X-ray image, and the second actual measurement values. The image generation unit generates an evaluation image for evaluating the state of the subject based on a corrected image, which is the first X-ray image corrected by the gain correction unit. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of an X-ray diagnostic apparatus according to the first embodiment. [Figure 2] FIG. 2 is a flowchart showing a series of processes performed by the medical information processing system 1 according to the first embodiment. [Figure 3A] FIG. 3A is a diagram showing an example of a high-energy object image according to the first embodiment. [Figure 3B] FIG. 3B is a diagram showing an example of a low-energy object image according to the first embodiment. [Figure 3C] FIG. 3C is a diagram showing an example of a bone image according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of the region extraction process according to the first embodiment. [Figure 5A]FIG. 5A is a diagram for explaining the bone mineral density calculation process according to the first embodiment. [Figure 5B] FIG. 5B is a diagram for explaining the bone mineral density calculation process according to the first embodiment. [Figure 5C] FIG. 5C is a diagram for explaining the bone mineral density calculation process according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing the results of the reproducibility evaluation according to the first embodiment. [Figure 7] FIG. 7 is a diagram showing the linear approximation results of the relationship between the number of years of medication and the amount of change in bone mineral density according to the first embodiment. [Figure 8] FIG. 8 is a block diagram showing an example of the configuration of an X-ray diagnostic apparatus according to the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0009] (First embodiment) The configuration of an X-ray diagnostic apparatus 10 will be described with reference to Fig. 1. As shown in Fig. 1, the X-ray diagnostic apparatus 10 includes an X-ray high voltage device 101, an X-ray tube 102, an X-ray aperture 103, a grid 104, an X-ray detector 105, an input interface 106, a display 107, a memory 108, a communication interface 109, and a processing circuit 110.

[0010] The X-ray high voltage generator 101 applies a high voltage to the X-ray tube 102. The X-ray high voltage generator 101 also includes a voltage sensor and a current sensor, and measures the tube voltage actually applied to the X-ray tube 102, the tube current supplied to the X-ray tube 102, and the pulse width. The X-ray tube 102 is a vacuum tube equipped with a cathode having a filament and an anode having a target. The X-ray tube 102 emits thermal electrons from the filament toward the target by the high voltage applied from the X-ray high voltage generator 101, and generates X-rays by causing the thermal electrons to collide with the target.

[0011] The X-ray aperture 103 has aperture blades made of an X-ray shielding material such as lead or tungsten, and an additional filter. The aperture blades are slidably disposed to narrow down the X-rays generated by the X-ray tube 102. The X-rays generated by the X-ray tube 102 are narrowed down by an aperture formed by, for example, four aperture blades. The additional filter changes the radiation quality of the transmitted X-rays depending on its material and thickness, with the aim of reducing the radiation dose to the subject P and improving the quality of the X-ray image, thereby reducing soft ray components that are easily absorbed by the subject P and high-energy components that cause a decrease in the contrast of the X-ray image. The additional filter also changes the X-ray dose and irradiation range depending on its material, thickness, position, etc., and attenuates the X-rays so that the X-rays irradiated from the X-ray tube 102 to the subject P have a predetermined distribution.

[0012] The grid 104 removes scattered rays (secondary X-rays) generated when the subject P is irradiated with X-rays, and is detachably provided at a position between the top plate on which the subject P is placed and the X-ray detector 105. The grid 104 is made of an X-ray shielding material such as lead or tungsten, and is formed in a lattice shape. The grid 104 may be a single grid, a cross grid, a honeycomb grid, or the like. A single grid is a grid in which lattices are formed parallel to one direction. A cross grid is a grid in which lattices are formed so as to intersect. A honeycomb grid is a grid in which lattices are formed in a honeycomb shape (hexagonal).

[0013] The X-ray detector 105 is composed of, for example, an X-ray flat panel detector (FPD). The X-ray detector 105 detects X-rays irradiated from the X-ray tube 102 and transmitted through the subject P and grid 104. The X-ray detector 105 supplies a detection signal corresponding to the detected X-ray dose to the processing circuit 110. The X-ray detector 105 may have a structure in which two types of phosphors with different X-ray absorption sensitivities, such as CsI (cesium iodide) and GOS (gadolinium oxide sulfur), are stacked. This makes it possible to collect X-ray images of two types of energy (dual energy) with a single X-ray irradiation. The X-ray detector 105 may be either an indirect conversion type or a direct conversion type.

[0014] The input interface 106 is composed of, for example, a mouse, keyboard, trackball, switches, buttons, joystick, a touchpad that performs input operations by touching the operation surface, a touchscreen that integrates a display screen and a touchpad, a non-contact input circuit using an optical sensor, a voice input circuit, etc. The input interface 106 accepts various input operations from the user and supplies electrical signals corresponding to the accepted input operations to the processing circuit 110.

[0015] The display 107 is configured by a display device such as a liquid crystal display, a CRT (Cathode Ray Tube) display, etc. The display 107 displays various information supplied from the processing circuit 110.

[0016] The memory 108 is configured by, for example, a storage device such as a semiconductor memory element such as a RAM (Random Access Memory) or a flash memory, a hard disk, an optical disk, etc. The memory 108 stores various information supplied from the processing circuitry 110. The memory 108 also stores programs executed by the processing circuitry 110.

[0017] The communication interface 109 is configured by, for example, a network card, a network adapter, etc. Under the control of the processing circuit 110, the communication interface 109 transmits and receives various information to and from external devices connected via a network.

[0018] The processing circuitry 110 is configured with an arithmetic processing device such as a CPU (Central Processing Unit), an MPU (Micro-processing unit), etc. The processing circuitry 110 controls each part of the X-ray diagnostic apparatus 10, thereby controlling the entire X-ray diagnostic apparatus 10.

[0019] Furthermore, the processing circuit 110 reads and executes programs stored in the memory 108, thereby functioning as an acquisition function 110a, a gain correction function 110b, an image generation function 110c, and an index measurement function 110d. The acquisition function 110a is an example of a first acquisition unit and a second acquisition unit. The gain correction function 110b is an example of a gain correction unit. The image generation function 110c is an example of an image generation unit. The index measurement function 110d is an example of an index measurement unit.

[0020] The X-ray diagnostic apparatus 10 configured as described above generates, for example, a bone image as an evaluation image for evaluating the condition of the subject P. Based on the generated bone image, the X-ray diagnostic apparatus 10 measures an index for evaluating the condition of the bones of the subject P, such as bone mineral density (BMD).

[0021] Here, the X-rays emitted from the X-ray tube 102 have statistical output errors. For example, even when the same X-ray conditions are set, it is difficult to achieve high-precision output reproducibility from the X-ray high voltage generator 101 (control limit of the X-ray high voltage generator 101). The X-ray diagnostic apparatus 10 improves the reproducibility of measurement of indices for evaluating the state of the subject P by performing processing to reduce statistically occurring output errors.

[0022] Hereinafter, the processing executed by the X-ray diagnostic apparatus 10 will be described with reference to FIG. 2. The acquisition function 110a captures a gain image, which is an X-ray image without a subject P (step S101). For example, the acquisition function 110a captures a 140 kV high energy gain image (I HG ) and 80 kV low-energy gain images (I LG The acquisition function 110a stores each captured energy gain image in the memory 108.

[0023] Furthermore, the acquisition function 110a stores the actual measurement values ​​relating to the X-ray conditions when capturing the gain images in the memory 108. Specifically, the X-ray high voltage device 101 stores the tube voltage (V HG ), the tube current actually supplied to the X-ray tube 102 (A HG ) and pulse width (T HG The acquisition function 110a acquires the results measured by the X-ray high voltage device 101 and stores them in the memory 108.

[0024] The acquisition function 110a also captures an object image, which is an X-ray image having the object P (step S102). For example, the acquisition function 110a captures a 140 kV high-energy object image (high-energy image I shown in FIG. 3A ) with the object P placed on the X-ray path between the X-ray tube 102 and the X-ray detector 105. H ) and a low-energy subject image at 80 kV (low-energy image I shown in Figure 3B). L The acquisition function 110a stores each captured image of the subject P in the memory 108. The subject P may be a patient or a phantom for calibration.

[0025] Furthermore, the acquisition function 110a stores the actual measurement values ​​related to the X-ray conditions when capturing the subject image in the memory 108. Specifically, the X-ray high voltage device 101 stores the tube voltage (V HG ), the tube current (A HG) and pulse width (T HG The acquisition function 110a acquires the results measured by the X-ray high voltage device 101 and stores them in the memory 108.

[0026] If the X-ray detector 105 has a structure in which two types of phosphors with different X-ray absorption sensitivities are stacked, the acquisition function 110a can collect high-energy and low-energy gain images and high-energy and low-energy subject images with a single X-ray irradiation. When imaging is performed using a stacked detector, it is preferable not to provide an additional filter to the X-ray detector 105. This is because providing such an additional filter reduces the room for radiation hardening and reduces energy separation ability.

[0027] Furthermore, the order in which steps S101 and S102 are performed is arbitrary. Furthermore, step S101 can be omitted as appropriate. For example, gain images may be captured periodically. That is, the acquisition function 110a periodically captures gain images and stores them in the memory 108. Then, instead of performing step S101, the acquisition function 110a may appropriately acquire the gain images stored in the memory 108.

[0028] For example, the high-energy image I shown in Figure 3A H , and the low-energy image I shown in Fig. 3B. L are respectively expressed by the following formulas (1) and (2).

[0029]

number

[0030]

number

[0031] I H0 and I L0are high-energy images and low-energy images obtained when the imaging in step S102 is performed without the subject P present, and are the ...1 is performed without the subject P present. HG , I LG ) is different from μ HA and μ LA are the mass attenuation coefficients of soft tissue at high and low energies, respectively. HB and μ LB are the mass attenuation coefficients of bone at high and low energies, respectively. Also, σ A is the density of the soft tissue, σ B is the bone density. The mass attenuation coefficient is expressed as, for example, "cm 2 / g". Density is expressed in units of, for example, "g / cm 2 " is expressed in units of ".

[0032] I HG The high energy gain image, I LG is a low-energy gain image, the high-energy image and the low-energy image after gain correction are expressed by the following equations (3) and (4), respectively.

[0033]

number

[0034]

number

[0035] Here, if the X-ray conditions set in step S101 and step S102 are the same, theoretically the exposure dose is the same. H0 =I HG " "I L0 =I LG However, due to the control limit of the X-ray high voltage generator 101, a statistical error occurs in the measured values ​​relating to the X-ray conditions between step S101 and step S102, and "I H0 ≠I HG " "I L0 ≠ILG "

[0036] Generally, the imaging dose is proportional to the measured tube current A and pulse width T. In addition, since the tube voltage V and the imaging dose have a nonlinear relationship, this relationship is expressed as a function F(V), and by correcting the above formulas (3) and (4) with the measured value, the following formulas (5) and (6) are obtained.

[0037]

number

[0038]

number

[0039] The subscript "HG" refers to the time when a high-energy gain image is captured in step S101. The subscript "LG" refers to the time when a low-energy gain image is captured in step S101. The subscript "H0" refers to the time when a high-energy object image is captured in step S102. The subscript "L0" refers to the time when a low-energy object image is captured in step S102.

[0040] The gain correction function 110b performs gain correction for each of the high-energy and low-energy object images using equations (5) and (6) (step S103). That is, the gain correction function 110b performs gain correction for the object image based on the actual measurement values ​​related to the X-ray conditions of the object image, the gain image, and the actual measurement values ​​related to the X-ray conditions of the gain image.

[0041] More specifically, the gain correction function 110b calculates the high-energy image I H Actual measured values ​​(A H0 , T H0 , V H0 ) and high energy gain image I HG and high energy gain image I HG Actual measured values ​​(A HG , T HG , VHG ) and based on the high-energy image I H Perform gain correction.

[0042] The gain correction function 110b corrects the low energy image I L Actual measured values ​​(A L0 , T L0 , V L0 ) and low energy gain image I LG and low energy gain image I LG Actual measured values ​​(A LG , T LG , V LG ) and based on the low-energy image I L Perform gain correction.

[0043] Note that the function F(V) in equations (5) and (6) depends on the entire system, including the X-ray high voltage generator 101, the X-ray tube 102, the X-ray aperture 103, and the grid 104. Therefore, it is preferable to measure the tube voltage dependency of pixel values ​​in advance using the X-ray detector 105 and approximate the function F(V) using a lookup table or a polynomial function. Alternatively, the relationship between the actually measured tube current A, pulse width T, and tube voltage V and the pixel values ​​measured using the X-ray detector 105 may be used as an overall function F(V), and the gain correction may be performed by approximating the function using a lookup table or a polynomial function.

[0044] In this way, the gain correction function 110b reduces the difference in X-ray sensitivity between the detection elements in the X-ray detector 105 and the statistically occurring output error of the X-ray tube 102, and can more accurately cancel out the bias in the dose and distribution of X-rays irradiated from the X-ray tube 102.

[0045] The image generating function 110c performs logarithmic subtraction between the high-energy image and the low-energy image that have been gain-corrected in step S103 to generate the bone image I shown in FIG. 3C. B (Step S104). B are examples of an image representing a target region of the subject P and an evaluation image for evaluating the condition of the subject P.

[0046] Specifically, the image generating function 110c performs logarithmic transformation on the equations (5) and (6). That is, the image generating function 110c performs logarithmic transformation on the object image after gain correction for each energy. The image generating function 110c adds "μ LA / μ HA ” and subtracted from the other subject image. As a result, the image generating function 110c generates the bone image I shown in Equation (7) and FIG. 3C. B Generate "μ LA / μ HA is an example of a predetermined coefficient, and the pixel values ​​of a portion consisting only of soft tissue in the subject P (for example, portions 501 and 502 in FIG. 5A) are expressed as the pixel values ​​of the bone image I shown in FIG. 3C. B It is set to be "0" when the

[0047]

number

[0048] The index measurement function 110d uses the bone image I shown in FIG. B From the image, a bone region for measuring an index for evaluating the bone condition of the subject P, such as bone mineral density (BMD), is extracted (step S105). For example, the index measurement function 110d extracts the bone region by receiving an operation to select the bone region from the user via the input interface 106. An example of bone region extraction is shown in FIG. 4. FIG. 4 shows a case where L1 to L4 are selected as the analysis region for the spine, and the hip joint is selected as the analysis region for the femur.

[0049] The index measurement function 110d may also automatically extract bone regions using segmentation processing. Segmentation processing methods include the watershed method, graph cut, and graph cut. The index measurement function 110d may also automatically extract bone regions using machine learning techniques such as Unet and PSPnet. When extracting bone regions through user operations, the extracted bone regions may differ for each user, or even for the same user, each time the user performs an operation. However, by having the index measurement function 110d automatically extract bone regions, the reproducibility of bone region extraction and the bone density calculation process described below can be improved.

[0050] The index measurement function 110d calculates the bone density of the bone region extracted in step S105 (step S106). Specifically, the index measurement function 110d calculates the bone density of the bone region extracted in step S105 (step S106). Specifically, the index measurement function 110d calculates the bone density of the bone image I using the calibration phantom shown in FIG. B The pixel value of the bone density (g / cm 2 In FIG. 5B, simulated bones 504, 505, and 506 are embedded inside acrylic 503. The bone density of each of the simulated bones 504, 505, and 506 is, for example, converted to "0.5 g / cm 2 ", 1.0g / cm 2 ", "1.5g / cm 2 If this calibration phantom is photographed under the same conditions as the subject P and a bone image of equation (7) is generated, a calibration curve 507 of the relationship between bone density and pixel value shown in FIG. 5C can be obtained from the bone image. From this calibration curve, the bone image I of the subject P can be calculated. B The pixel value of the bone density (g / cm 2 " can be converted into

[0051] Furthermore, the mass attenuation coefficient μ depends on the energy of X-rays. As is clear from equation (7), the calibration curve 507 changes due to fluctuations in the tube voltage for high-energy imaging and the tube voltage for low-energy imaging. Therefore, calibration curves corresponding to multiple tube voltages, such as calibration curves 508 and 509, may be acquired in advance and approximated using a lookup table or a polynomial function. Applying a calibration curve corresponding to the actual measured value of the tube voltage enables more accurate calculation of bone density. That is, the index measurement function 110d acquires a calibration curve corresponding to the tube voltage associated with the X-ray conditions of the first X-ray image having the subject, and measures the index (bone density) based on the acquired calibration curve and the evaluation image, thereby improving the measurement accuracy of the index.

[0052] The results of the bone density calculation process performed by the index measurement function 110d can be displayed on the display 107. For example, the display 107 can display the calculated bone density (g / cm 2 Alternatively, the X-ray diagnostic apparatus 10 may transmit the result of the bone density calculation process to another device via the network NW. In this case, the result of the bone density calculation process is displayed on the other device and provided to a user such as a doctor.

[0053] As described above, according to the first embodiment, the acquisition function 110a acquires a subject image (first X-ray image), which is an X-ray image including the subject P. The acquisition function 110a also acquires actual measurement values ​​(first actual measurement values) related to the X-ray conditions of the subject image, a gain image (second X-ray image), which is an X-ray image not including the subject P, and actual measurement values ​​(second actual measurement values) related to the X-ray conditions of the gain image. The gain correction function 110b corrects the first X-ray image based on the first actual measurement values, the second X-ray image, and the second actual measurement values. The image generation function 110c generates an evaluation image for evaluating the condition of the subject P based on a corrected image, which is the first X-ray image corrected by the gain correction function 110b. As a result, the X-ray diagnostic apparatus 10 according to the first embodiment can reduce the influence of X-ray output errors to improve the accuracy of gain correction, and ultimately improve the reproducibility of measurements of indices for evaluating the condition of the subject (e.g., bone density).

[0054] Figure 6 shows the results of a reproducibility evaluation of bone density calculated by the series of processes in Figure 2. In this evaluation, the high-energy tube voltage was set to "140 kV," the low-energy tube voltage to "80 kV," and a copper plate with a thickness of "0.5 mm" was used as the additional filter for the X-ray aperture 103. In addition, in this evaluation, the measurement target was a geometric phantom similar to that in Figure 5B. As shown in Figure 6, without the correction in step S103, the standard deviation was "2.35%," whereas with the correction in step S103, a reproducibility of "standard deviation = 2.35%" was achieved.

[0055] Figure 7 shows the linear approximation results for the relationship between years of medication and change in bone mineral density, using the osteoporosis drug denosumab as an example. Figure 7 shows that when the reproducibility of bone mineral density measurements is 1%, a significant change is recognized in 0.9 years, whereas when the reproducibility is 2%, it takes 1.8 years, and when the reproducibility is 3%, it takes 2.7 years. In this way, improving the accuracy of bone mineral density calculation processing and increasing reproducibility enables earlier assessment of drug efficacy.

[0056] In this embodiment, an example in which gain correction is performed on X-ray images of two types of energy has been described, but gain correction can also be performed on X-ray images of one type of energy or three or more types of energy in the same way.

[0057] Furthermore, in the present embodiment, an example has been described in which actual measured values ​​of the tube voltage, tube current, and pulse width are used. However, a combination of any two of the tube voltage, tube current, and pulse width, or only any one of the tube voltage, tube current, and pulse width may be used.

[0058] (Second embodiment) In the above-described embodiment, the tube current is measured when the gain image and the subject image are acquired, and at least one of the gain image and the subject image is corrected based on the measurement result.

[0059] Here, the measured value of the tube current may fluctuate over time due to transient phenomena within one pulse. Among transient phenomena, overshoot is merely an apparent change in the tube current in the measurement and does not actually exist. Furthermore, the value is also affected by the state of the device. For these reasons, the influence of transient phenomena cannot be completely eliminated by using a measured value at a single point in time, an average value of measured values ​​at multiple points in time, or an integrated value over a specified interval, and therefore an accurate actual measured value of the tube current cannot necessarily be obtained.

[0060] Therefore, in steps S101 and S102 shown in FIG. 2, the tube current may be measured in a time series manner. That is, the first actual measurement value and the second actual measurement value described above may be waveform data of the tube current. Then, the gain correction function 110b analyzes the waveform data of the tube current to estimate the value of the tube current to be used in the gain correction in step S103. This allows the gain correction function 110b to take into account the influence of transient phenomena and acquire an appropriate tube current value to be used in the gain correction. Note that, for example, a simulation method or a method using a trained model based on machine learning can be used to estimate the actual measurement value of the tube current.

[0061] The acquisition function 110a may also acquire the results of the waveform analysis and tube current estimation in real time in parallel with the X-ray irradiation, and perform AEC (Auto Exposure Control) control based on the estimated value of the tube current, thereby improving the reproducibility of the X-ray output and further improving the accuracy of the analysis processing based on the X-ray image.

[0062] (Third embodiment) Another method for eliminating the influence of the transient phenomenon described in the second embodiment will be described. For example, the X-ray diagnostic apparatus 10 acquires a plurality of gain images by changing the tube current setting value in capturing the gain images in step S101. These gain images are stored in, for example, the memory 108. Note that the gain images captured in advance for each tube current setting value are also referred to as preliminary gain images.

[0063] Thereafter, when the subject image is captured in step S102, gain correction function 110b selects and acquires an appropriate gain image from a plurality of gain images captured in advance. Specifically, gain correction function 110b selects, from a plurality of gain images with different tube current setting values, the one that is closest to the measured tube current value when the subject image is captured, and uses the selected gain image for gain correction in S103. Alternatively, gain correction function 110b may perform interpolation processing using a plurality of gain images with different tube current setting values ​​to generate a gain image corresponding to the measured tube current value when the subject image is captured, and use the generated gain image for gain correction in S103.

[0064] Alternatively, the gain correction function 110b may measure the tube current in a time series manner and select an appropriate gain image based on the degree of coincidence of the waveforms. That is, the gain correction function 110b may compare the waveform of the tube current when each of the multiple gain images is captured with the waveform of the tube current when the subject image is captured, select the gain image having the closest waveform, and use it for the gain correction in S103. In this case, multiple gain images may be collected for each set value of the tube current.

[0065] According to the third embodiment, gain correction processing that takes into account transient phenomena of tube currents can be performed with simpler implementation. Furthermore, when a gain image is selected based on the degree of waveform coincidence, appropriate gain correction is possible even when the reproducibility of the tube current waveform is low. Consequently, the accuracy of analysis processing based on X-ray images can be improved.

[0066] (Fourth embodiment) Another method for eliminating the influence of the transient phenomenon described in the second and third embodiments will be described below. The gain correction function 110b calculates a measured value of the tube current based on data from the area dosimeter, the actual measured value of the tube voltage, and the actual measured value of the pulse width.

[0067] That is, when capturing the gain image and the subject image, the X-ray diagnostic apparatus 10 measures the irradiated dose using an area dosimeter. The irradiation dose can be expressed as a function according to the tube current, tube voltage, and pulse width, and the gain correction function 110b can back-calculate the measured value of the tube current based on the area dosimeter data, the actual measured value of the tube voltage, and the actual measured value of the pulse width. This method also performs gain correction while eliminating the influence of transient phenomena in the tube current, thereby improving the accuracy of analysis processing based on the X-ray images.

[0068] (Fifth embodiment) In the above-described embodiment, the bone image of Fig. 3C has been described as an example of an evaluation image for evaluating the condition of the subject P. However, the embodiment is not limited to this, and various modifications are possible regarding the target region of the evaluation image generated by the image generation function 110c.

[0069] For example, the X-ray diagnostic apparatus 10 may be a mammography apparatus equipped with a compression plate or the like for compressing the breast of the subject P, and may generate breast images for evaluating the condition of the breast of the subject P. In this case, as in the above embodiment, the acquisition function 110a acquires a subject image (first X-ray image) that is an X-ray image including the subject P. The X-ray image is an MLO (Mediolateral-Oblique) image or a CC (Cranio-Caudal) image. As in the above embodiment, the acquisition function 110a also acquires actual measurement values ​​(first actual measurement values) related to the X-ray conditions of the subject image, a gain image (second X-ray image) that is an X-ray image not including the subject P, and actual measurement values ​​(second actual measurement values) related to the X-ray conditions of the gain image. As in the above embodiment, the gain correction function 110b corrects the first X-ray image based on the first actual measurement values, the second X-ray image, and the second actual measurement values. The image generating function 110c generates an evaluation image (here, a breast image) for evaluating the state of the mammary glands of the subject P based on the corrected image, which is the first X-ray image corrected by the gain correcting function 110b.

[0070] The index measurement function 110d executes an analysis process based on the mammary gland image to calculate breast density (BD). For example, the index measurement function 110d sets a first region corresponding to the breast and a second region where the mammary gland is present in the mammary gland image, and calculates breast density by dividing the area of ​​the second region by the area of ​​the first region.

[0071] 2 is executed in the X-ray diagnostic apparatus 10, these processes may be executed in a device other than the X-ray diagnostic apparatus 10. For example, the processes of steps S103 to S106 may be executed in an X-ray image processing apparatus 30 shown in FIG.

[0072] 8, an X-ray diagnostic apparatus 10 and an X-ray image processing apparatus 30 are connected to each other via a network NW. The X-ray diagnostic apparatus 10 acquires the above-mentioned first X-ray image, first actual measurement values, second X-ray image, second actual measurement values, etc., and transmits them to the X-ray image processing apparatus 30 via the network NW.

[0073] Note that various information may be transmitted from the X-ray diagnostic apparatus 10 to the X-ray image processing device 30 via another device. As an example, the X-ray diagnostic apparatus 10 transmits the acquired X-ray images and actual measurement values ​​to an image storage device such as a PACS (Picture Archiving and Communication System) for storage. In this case, the X-ray image processing device 30 can acquire the X-ray images and actual measurement values ​​from the image storage device.

[0074] For example, as shown in FIG. 1, the X-ray image processing device 30 includes an input interface 31, a display 32, a memory 33, a communication interface 34, and a processing circuit 35.

[0075] The input interface 31 can be configured in the same manner as the above-described input interface 106. For example, the input interface 31 receives various input operations from a user of the X-ray image processing apparatus 30, converts the received input operations into electrical signals, and outputs the electrical signals to the processing circuitry 35.

[0076] The display 32 can be configured in the same manner as the above-described display 107. For example, under the control of the processing circuitry 35, the display 32 displays an X-ray image, processing results by the processing circuitry 35, a GUI for receiving various instructions and settings from the user, and the like.

[0077] The memory 33 can be configured in the same manner as the above-described memory 108. For example, the memory 33 stores X-ray images, processing results by the processing circuitry 110, programs executed by the processing circuitry 110, and the like.

[0078] The communication interface 34 can be configured in the same manner as the above-described communication interface 109. For example, the communication interface 34 performs information communication between the X-ray diagnostic apparatus 10 and the X-ray image processing apparatus 30 by connecting to a network NW.

[0079] The processing circuitry 35 is composed of an arithmetic processing device such as a CPU, an MPU, etc., and controls each part of the X-ray image processing device 30, thereby controlling the entire X-ray image processing device 30. The processing circuitry 35 also reads and executes programs stored in the memory 33, thereby functioning as an acquisition function 35a, a gain correction function 35b, an image generation function 35c, and an index measurement function 35d.

[0080] The acquisition function 35a is an example of a first acquisition unit and a second acquisition unit. The acquisition function 35a acquires various pieces of information, such as the first X-ray image, the first measured value, the second X-ray image, and the second measured value, from the X-ray diagnostic apparatus 10 via the network NW.

[0081] The gain correction function 35b is a function similar to the gain correction function 110b described above, and corrects the first X-ray image based on the first actual measurement value, the second X-ray image, and the second actual measurement value, and obtains a corrected image of the first X-ray image. The image generation function 35c is a function similar to the image generation function 110c described above, and generates an evaluation image for evaluating the condition of the subject P based on the corrected image. The index measurement function 35d is a function similar to the index measurement function 110d described above, and measures an index for evaluating the condition of the subject P based on the evaluation image generated by the image generation function 35c.

[0082] 8, each processing function is stored in the form of a program executable by a computer in memory 33. Processing circuitry 35 is a processor that realizes the function corresponding to each program by reading and executing the program from memory 33. In other words, the processing circuitry 35 in a state in which a program has been read has the function corresponding to the read program.

[0083] 8, the acquisition function 35a, gain correction function 35b, image generation function 35c, and index measurement function 35d are realized by a single processing circuit 35. However, the processing circuit 35 may be configured by combining multiple independent processors, and each processor may execute a program to realize the functions. Furthermore, each processing function of the processing circuit 35 may be realized by being appropriately distributed or integrated into a single or multiple processing circuits.

[0084] The processing circuitry 35 may also realize its functions by using a processor of an external device connected via a network NW. For example, the processing circuitry 35 reads and executes a program corresponding to each function from the memory 33, and realizes each function shown in Fig. 8 by using a group of servers (cloud) connected to the X-ray image processing device 30 via the network NW as a computing resource.

[0085] The term "processor" used in the above description refers to a circuit such as a CPU, a graphics processing unit (GPU), an application specific integrated circuit (ASIC), or a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), or a field programmable gate array (FPGA)). When the processor is a CPU, for example, the processor realizes its function by reading and executing a program stored in a memory circuit. On the other hand, when the processor is an ASIC, for example, instead of storing a program in a memory circuit, the function is directly incorporated into the processor circuit as a logic circuit. Note that each processor in the embodiments is not limited to being configured as a single circuit, but may be configured as a single processor by combining multiple independent circuits to realize its function. Furthermore, multiple components in each figure may be integrated into a single processor to realize its function.

[0086] In addition, the above description assumes that a single memory 33 stores a program corresponding to each processing function of the processing circuit 35. Also, the description assumes that a single memory 108 stores a program corresponding to each processing function of the processing circuit 110. However, the embodiment is not limited to this. For example, a configuration may be adopted in which multiple memories 33 are distributed and the processing circuit 35 reads the corresponding program from each individual memory 33. Similarly, a configuration may be adopted in which multiple memories 108 are distributed and the processing circuit 110 reads the corresponding program from each individual memory 108. Furthermore, instead of storing a program in the memory 33 or the memory 108, a configuration may be adopted in which the program is directly embedded in the circuit of the processor. In this case, the processor realizes its function by reading and executing the program embedded in the circuit.

[0087] The components of each device according to the above-described embodiments are conceptual and functionally independent, and are not necessarily physically configured as shown in the drawings. In other words, the specific form of distribution and integration of each device is not limited to that shown in the drawings, and all or part of each device can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc. Furthermore, all or any part of the processing functions 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 using wired logic.

[0088] The methods described in the above embodiments can be realized by executing a prepared program on a computer such as a personal computer or a workstation. This program can be distributed via a network such as the Internet. The medical image processing program can also be recorded on a non-transitory computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, or DVD, and executed by being read from the recording medium by a computer.

[0089] According to at least one of the embodiments described above, the accuracy of gain correction can be improved.

[0090] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0091] With respect to the above embodiment, the following supplementary notes are disclosed as one aspect and optional features of the invention. (Appendix 1) a first acquisition unit that acquires a first X-ray image having an object; a second acquisition unit that acquires first measured values ​​related to X-ray conditions of the first X-ray image, a second X-ray image not including the subject, and second measured values ​​related to X-ray conditions of the second X-ray image; a gain correction unit that corrects the first X-ray image based on the first actual measurement value, the second X-ray image, and the second actual measurement value; an image generating unit that generates an evaluation image for evaluating a state of the subject based on the corrected image corrected by the gain correcting unit; An X-ray image processing device comprising: (Appendix 2) The gain correction unit correcting the first X-ray image corresponding to the higher energy of the X-rays of two different energies based on the first measured value, the second X-ray image, and the second measured value; correcting the first X-ray image corresponding to the lower energy of the X-rays of the two types of energy based on the first measured value, the second X-ray image, and the second measured value; acquiring a first corrected image corresponding to the high-energy X-rays and a second corrected image corresponding to the low-energy X-rays; The image generating section may generate the evaluation image based on the first corrected image and the second corrected image. (Appendix 3) The image generation unit may perform a logarithmic transformation of the first corrected image and the second corrected image, multiply one of the logarithmically transformed corrected images by a predetermined coefficient, and generate the evaluation image based on the corrected image multiplied by the coefficient and the other logarithmically transformed corrected image. (Appendix 4) The first measured value and the second measured value may be waveform data of a tube current. (Appendix 5) the X-ray image without a subject and the measured values ​​related to the X-ray conditions of the X-ray image are stored in a memory in association with each of a plurality of energies; The second acquisition unit may acquire the second X-ray image and the second measured values ​​from the memory in accordance with X-ray conditions set for the subject. (Appendix 6) The image generating apparatus may further include an index measuring unit that measures an index for evaluating a state of the subject based on the evaluation image generated by the image generating unit. (Appendix 7) The index measurement unit may acquire a calibration curve according to a tube voltage related to an X-ray condition of the first X-ray image, and measure the index based on the acquired calibration curve and the evaluation image. (Appendix 8) a first acquisition unit that acquires a first X-ray image having an object; a second acquisition unit that acquires first measured values ​​related to X-ray conditions of the first X-ray image, a second X-ray image not including the subject, and second measured values ​​related to X-ray conditions of the second X-ray image; a gain correction unit that corrects the first X-ray image based on the first actual measurement value, the second X-ray image, and the second actual measurement value; an image generating unit that generates an evaluation image for evaluating a state of the subject based on a corrected image that is the first X-ray image corrected by the gain correcting unit; An X-ray diagnostic device comprising: (Appendix 9) acquiring a first x-ray image having the subject; acquiring a first measured value related to the X-ray conditions of the first X-ray image, a second X-ray image not including the subject, and a second measured value related to the X-ray conditions of the second X-ray image; correcting the first X-ray image based on the first actual measurement value, the second X-ray image, and the second actual measurement value; generating an evaluation image for evaluating the state of the subject based on the corrected image, which is the first X-ray image; A method comprising: (Appendix 10) acquiring a first x-ray image having the subject; acquiring a first measured value related to the X-ray conditions of the first X-ray image, a second X-ray image not including the subject, and a second measured value related to the X-ray conditions of the second X-ray image; correcting the first X-ray image based on the first actual measurement value, the second X-ray image, and the second actual measurement value; generating an evaluation image for evaluating the state of the subject based on the corrected image, which is the corrected first X-ray image; A program that causes a computer to perform each process. (Appendix 11) The image generating section may generate, as the evaluation image, a bone image representing a bone of the subject. (Appendix 12) The index measurement unit may execute the analysis process based on the bone image and calculate bone density. (Appendix 13) The image generating section may generate, as the evaluation image, a mammary gland image representing a mammary gland of the subject. (Appendix 14) The index measurement unit may execute the analysis process based on the mammary gland image and calculate mammary gland density. (Appendix 15) The X-ray conditions may include a measured value of at least one of a tube voltage, a tube current, and a pulse width. (Appendix 16) The gain correction unit may calculate a measured value of a tube current as the X-ray condition based on data from an area dosimeter, an actual measured value of a tube voltage, and an actual measured value of a pulse width. (Appendix 17) The gain correction unit may select the gain image from a plurality of preliminary gain images captured for each set value of tube current, in accordance with the X-ray conditions under which the subject image was captured. [Explanation of symbols]

[0092] 1 Medical information processing system 10 X-ray diagnostic equipment 110 Processing circuit 110a Acquisition function 110b Gain correction function 110c image generation function 110d indicator measurement function 30 X-ray image processing device 35 Processing circuit 35a Acquisition function 35b Gain correction function 35c Image generation function 35d index measurement function

Claims

1. a first acquisition unit configured to acquire a first X-ray image having an object; a second acquisition unit that acquires first actual measurement values ​​related to X-ray conditions of the first X-ray image, a second X-ray image not including the subject, and second actual measurement values ​​related to X-ray conditions of the second X-ray image; correcting the first X-ray image corresponding to the high energy of the X-rays of two different energies based on the first actual measurement value, the second X-ray image, and the second actual measurement value; correcting the first X-ray image corresponding to the lower energy of the X-rays of the two types of energy based on the first actual measurement value, the second X-ray image, and the second actual measurement value; a gain correction unit that acquires corrected images that are the corrected first X-ray image, the first corrected image corresponding to the high-energy X-ray and the second corrected image corresponding to the low-energy X-ray; an image generating unit that generates an evaluation image for evaluating a state of the subject based on the first corrected image and the second corrected image; An X-ray image processing device comprising:

2. 2. The X-ray image processing apparatus according to claim 1, wherein the image generation unit performs logarithmic transformation on the first corrected image and the second corrected image, multiplies one of the logarithmically transformed corrected images by a predetermined coefficient, and generates the evaluation image based on the corrected image multiplied by the coefficient and the other logarithmically transformed corrected image.

3. 3. The X-ray image processing apparatus according to claim 1, wherein the first measured value and the second measured value are waveform data of tube current.

4. the X-ray image without a subject and actual measurement values ​​related to the X-ray conditions for the X-ray image are stored in a memory in association with each of a plurality of energies; 4. The X-ray image processing apparatus according to claim 1, wherein the second acquisition unit acquires the second X-ray image and the second measured value from the memory according to X-ray conditions set for the subject.

5. 5. The X-ray image processing apparatus according to claim 1, further comprising an index measurement unit that measures an index for evaluating a state of the subject based on the evaluation image generated by the image generation unit.

6. 6. The X-ray image processing apparatus according to claim 5, wherein the index measurement unit acquires a calibration curve according to a tube voltage related to the X-ray conditions of the first X-ray image, and measures the index based on the acquired calibration curve and the evaluation image.

7. a first acquisition unit configured to acquire a first X-ray image having an object; a second acquisition unit that acquires first actual measurement values ​​related to X-ray conditions of the first X-ray image, a second X-ray image not including the subject, and second actual measurement values ​​related to X-ray conditions of the second X-ray image; correcting the first X-ray image corresponding to the high energy of the X-rays of two different energies based on the first actual measurement value, the second X-ray image, and the second actual measurement value; correcting the first X-ray image corresponding to the lower energy of the X-rays of the two types of energy based on the first actual measurement value, the second X-ray image, and the second actual measurement value; a gain correction unit that acquires corrected images that are the corrected first X-ray image, the first corrected image corresponding to the high-energy X-ray and the second corrected image corresponding to the low-energy X-ray; an image generating unit that generates an evaluation image for evaluating a state of the subject based on the first corrected image and the second corrected image; An X-ray diagnostic apparatus comprising:

8. acquiring a first x-ray image having an object; acquiring a first measured value related to an X-ray condition of the first X-ray image, a second X-ray image not including the subject, and a second measured value related to the X-ray condition of the second X-ray image; correcting the first X-ray image corresponding to the high energy of the X-rays of two different energies based on the first actual measurement value, the second X-ray image, and the second actual measurement value; correcting the first X-ray image corresponding to the lower energy of the X-rays of the two types of energy based on the first actual measurement value, the second X-ray image, and the second actual measurement value; obtaining corrected images, the corrected first X-ray image being a first corrected image corresponding to the high-energy X-rays and a second corrected image corresponding to the low-energy X-rays; generating an evaluation image for evaluating the state of the subject based on the first corrected image and the second corrected image; A method comprising:

9. acquiring a first x-ray image having an object; acquiring a first measured value related to an X-ray condition of the first X-ray image, a second X-ray image not including the subject, and a second measured value related to the X-ray condition of the second X-ray image; correcting the first X-ray image corresponding to the high energy of the X-rays of two different energies based on the first actual measurement value, the second X-ray image, and the second actual measurement value; correcting the first X-ray image corresponding to the lower energy of the X-rays of the two types of energy based on the first actual measurement value, the second X-ray image, and the second actual measurement value; obtaining corrected images, the corrected first X-ray image being a first corrected image corresponding to the high-energy X-rays and a second corrected image corresponding to the low-energy X-rays; generating an evaluation image for evaluating the state of the subject based on the first corrected image and the second corrected image; A program that causes a computer to perform each process.

10. A first acquisition unit that acquires a first X-ray image having a subject; a second acquisition unit that acquires first actual measurement values ​​related to X-ray conditions of the first X-ray image, a second X-ray image not including the subject, and second actual measurement values ​​related to X-ray conditions of the second X-ray image, the first actual measurement values ​​and the second actual measurement values ​​being waveform data of tube current; a gain correction unit that corrects the first X-ray image based on the first actual measurement value, the second X-ray image, and the second actual measurement value; an image generating unit that generates an evaluation image for evaluating a state of the subject based on the corrected image, which is the first X-ray image corrected by the gain correcting unit; An X-ray image processing device comprising:

11. A first acquisition unit that acquires a first X-ray image having a subject; a second acquisition unit that acquires first actual measurement values ​​related to X-ray conditions of the first X-ray image, a second X-ray image not including the subject, and second actual measurement values ​​related to X-ray conditions of the second X-ray image, the first actual measurement values ​​and the second actual measurement values ​​being waveform data of tube current; a gain correction unit that corrects the first X-ray image based on the first actual measurement value, the second X-ray image, and the second actual measurement value, and obtains a corrected image of the first X-ray image; an image generating unit that generates an evaluation image for evaluating a state of the subject based on the corrected image; An X-ray diagnostic apparatus comprising:

12. A method for obtaining a first X-ray image having a subject; acquiring a first actual measurement value related to an X-ray condition of the first X-ray image, a second X-ray image not including the subject, and a second actual measurement value related to the X-ray condition of the second X-ray image, the first actual measurement value and the second actual measurement value being waveform data of a tube current; correcting the first X-ray image based on the first actual measurement value, the second X-ray image, and the second actual measurement value; generating an evaluation image for evaluating the state of the subject based on the corrected image, which is the first X-ray image; A method comprising:

13. A method for obtaining a first X-ray image having a subject; acquiring a first actual measurement value related to an X-ray condition of the first X-ray image, a second X-ray image not including the subject, and a second actual measurement value related to the X-ray condition of the second X-ray image, the first actual measurement value and the second actual measurement value being waveform data of a tube current; correcting the first X-ray image based on the first actual measurement value, the second X-ray image, and the second actual measurement value; generating an evaluation image for evaluating the state of the subject based on the corrected image, which is the first X-ray image; A program that causes a computer to perform each process.

Images