WO2020012520A1

WO2020012520A1 - Medical x-ray image processing device and x-ray imaging device

Info

Publication number: WO2020012520A1
Application number: PCT/JP2018/025842
Authority: WO
Inventors: 淳也山本
Original assignee: 株式会社島津製作所
Priority date: 2018-07-09
Filing date: 2018-07-09
Publication date: 2020-01-16
Also published as: JP7115545B2; JPWO2020012520A1

Abstract

This medical X-ray image processing device (1) is provided with an X-ray image processing unit (9b) that associates multiple absorption coefficients (A1, B1, C1) of respective feature sections (A, B, C) in an X-ray image (R) stored in a phantom information storage unit (9a) with multiple pixel values (X, Y, Z) of respective feature sections (A, B, C) in an X-ray image (R) in which an object (20) is captured together with a phantom (30).

Description

Medical X-ray image processing apparatus and X-ray image photographing apparatus

The present invention relates to a medical X-ray image processing device and an X-ray image photographing device.

Conventionally, a medical X-ray image processing apparatus and an X-ray image capturing apparatus for acquiring an X-ray image of a subject are known. Such a medical X-ray image processing apparatus and X-ray image radiographing apparatus are disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-311922.

The X-ray imaging apparatus described in Japanese Patent Application Laid-Open No. 2006-31922 discloses an X-ray generation apparatus that generates X-rays for irradiating a subject, and an X-ray generation apparatus that is arranged to face the X-ray generation apparatus and transmits X-rays transmitted through the subject. An X-ray detection unit that detects and converts the image data into image data. An X-ray imaging apparatus includes a correction processing unit that obtains corrected image data by performing various types of correction processing on image data, and an automatic gradation processing unit that obtains output image data by automatically performing gradation conversion on the corrected image data. And an image processing apparatus including: Here, the automatic gradation processing unit has a storage unit that stores a plurality of basic gradation conversion characteristics that are desirable gradation conversion functions.

The automatic gradation processing unit in the X-ray imaging apparatus described in Japanese Patent Application Laid-Open No. 2006-311922 is configured to select an appropriate basic gradation conversion characteristic from among the plurality of basic gradation conversion characteristics stored in the storage unit. It is configured to acquire a gradation conversion characteristic. Specifically, the automatic gradation processing unit obtains a feature amount such as a maximum value, a minimum value, and an average value of pixel values in the feature region set in the corrected image data, and determines that an error from the feature amount is minimum. It is configured to acquire the following basic gradation conversion characteristics.

JP 2006-311922 A

However, in the X-ray imaging apparatus described in Japanese Patent Application Laid-Open No. 2006-311922, since the basic gradation conversion characteristic is obtained based on the pixel value of the characteristic region in the corrected image data, the X-ray dose is reduced. A change in the position of the X-ray generator or a change in the position of the X-ray generator causes a problem that the feature amount (reference) in the corrected image data (X-ray image) at the time of acquiring the basic gradation conversion characteristics is changed. is there. As a result, a high-precision reconstructed image cannot be obtained, for example, when reconstructing a plurality of images, due to a difference in reference between a plurality of captured images.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a method for changing the dose of an X-ray or changing the position of an X-ray generator. To provide a medical X-ray image processing apparatus and an X-ray image capturing apparatus capable of preventing a reference in an X-ray image from being changed.

In order to achieve the above object, a medical X-ray image processing apparatus according to a first aspect of the present invention includes a plurality of reference portions corresponding to a plurality of reference portions of a phantom including a plurality of reference portions having different X-ray absorption coefficients. A phantom information storage unit that stores an absorption coefficient; a plurality of absorption coefficients of each of a plurality of reference units in the X-ray image stored in the phantom information storage unit; And an X-ray image processing unit that associates each of the plurality of pixel values of the reference unit with the X-ray image processing unit. Note that the pixel value in the present invention is a broad concept including not only a general pixel value, but also a pixel value converted by a log conversion and a pixel value converted by a conversion coefficient such as a sigmoid curve. is there.

In the medical X-ray image processing apparatus according to the first aspect of the present invention, as described above, the X-ray image processing unit includes a plurality of reference units in the X-ray image stored in the phantom information storage unit. The absorption coefficient is configured to correspond to each of the plurality of pixel values of the plurality of reference portions of the phantom in the X-ray image of the subject captured with the phantom. As a result, since the respective absorption coefficients of the plurality of reference portions of the phantom in the X-ray image correspond to the plurality of pixel values, the dose of X-rays changes and the position of the X-ray generator changes. However, for example, when correcting the pixel value in the X-ray image, the reference in the X-ray image can be prevented from being changed. As a result, a high-precision reconstructed image can be obtained, for example, when reconstructing a plurality of images due to a difference in reference between the plurality of images.

In the medical X-ray image processing apparatus according to the first aspect, preferably, the X-ray image processing unit corrects each of the plurality of pixel values corresponding to the plurality of absorption coefficients to a plurality of target pixel values. It is configured. With this configuration, the pixel value in the X-ray image is corrected to the target pixel value by using the mutual relationship between the plurality of target pixel values set for each of the plurality of reference portions of the phantom. In this case, not only a plurality of target pixel values corresponding to a plurality of absorption coefficients but also a target pixel value of a pixel value in an X-ray image can be set.

In the medical X-ray image processing apparatus including an X-ray image processing unit that corrects the plurality of pixel values to a target pixel value, preferably, the X-ray image processing unit includes a plurality of absorption coefficients corresponding to a plurality of reference units of a phantom. And a plurality of target pixel values corresponding to each of the plurality of absorption coefficients, based on a target pixel value function set by a relationship between the plurality of target pixel values and a plurality of target pixel values corresponding to each of the plurality of absorption coefficients. It is configured to correct to the corresponding target pixel value on the value function. With this configuration, a plurality of target pixel values can be handled as a target pixel value function associated with a plurality of absorption coefficients, so that information on a plurality of target pixel values can be easily obtained.

In a medical X-ray image processing apparatus including an X-ray image processing unit that sets a relationship between a plurality of target pixel values corresponding to each of the plurality of absorption coefficients as a target pixel value function, preferably the X-ray image processing unit Pixel value correction for correcting a plurality of pixel values corresponding to a plurality of absorption coefficients to a plurality of target pixel values on a target pixel value function each time an X-ray image of a subject taken with a phantom is obtained It is configured to get a table. With this configuration, each time an X-ray image is acquired, a corresponding X-ray image pixel value correction table is acquired, thereby acquiring a plurality of X-ray images having the same reference pixel value corrected. Therefore, when reconstructing a plurality of X-ray images, a highly accurate reconstructed image can be easily obtained.

In a medical X-ray image processing apparatus including an X-ray image processing unit that obtains the pixel value correction table, preferably, when the X-ray image processing unit obtains a plurality of X-ray images by performing a plurality of X-ray imagings, Each time a plurality of X-ray images are obtained, a pixel value correction table is acquired, and each of the plurality of X-ray images is corrected based on the pixel value correction table corresponding to each of the plurality of X-ray images. Is configured. With such a configuration, even if each of the plurality of X-ray images is corrected by the pixel value correction table acquired each time each of the plurality of X-ray images is obtained, the pixel value correction table is stored in the plurality of phantoms. Are obtained by the pixel values associated with the plurality of absorption coefficients of each of the reference portions, so that a plurality of X-ray images with the same reference correction can be obtained. Accordingly, for example, even when a plurality of X-ray images are reconstructed to obtain a reconstructed image, it is possible to suppress an artifact (virtual image) from occurring in the reconstructed image.

In a medical X-ray image processing apparatus including an X-ray image processing unit that sets a relationship between a plurality of target pixel values corresponding to each of the plurality of absorption coefficients as a target pixel value function, preferably the X-ray image processing unit , Estimated pixel value information of the X-ray image estimated based on the plurality of absorption coefficients of each of the plurality of reference portions of the phantom in the X-ray image and the plurality of pixel values corresponding to each of the plurality of absorption coefficients. Is configured to acquire a pixel value correction table based on According to this configuration, an accurate pixel value correction table can be obtained based on the estimated pixel value information, so that the pixel values in the X-ray image based on the pixel value correction table can be accurately corrected.

In this case, preferably, a display unit is further provided, and the X-ray image processing unit is configured to display both the target pixel value function and the estimated pixel value information on the display unit. With this configuration, the user can easily visually recognize the difference between the target pixel value function and the estimated pixel value information.

In the medical X-ray image processing apparatus including the X-ray image processing unit that corrects the plurality of pixel values to the target pixel value, preferably, the X-ray image processing unit includes a plurality of reference units stored in the phantom information storage unit. An X-ray in which a plurality of pixel values are corrected to a plurality of target pixel values based on correspondence information in which each of the plurality of absorption coefficients is associated with each of a plurality of pixel values of a plurality of reference portions in the X-ray image The configuration of the image processing performed on the image is changed, or the setting of the image processing performed on the X-ray image before correction is changed. With this configuration, it is possible to appropriately set the image processing before or after the correction performed on the X-ray image.

An X-ray imaging apparatus according to a second aspect of the present invention includes an X-ray source, a detector that detects X-rays emitted from the X-ray source, and an X-ray intensity distribution based on the X-ray intensity distribution detected by the detector. An image processing unit for acquiring an image, wherein the image processing unit stores a plurality of absorption coefficients respectively corresponding to a plurality of reference portions of the phantom including a plurality of reference portions having different X-ray absorption coefficients. Part, a plurality of absorption coefficients of each of a plurality of reference parts in the X-ray image stored in the phantom information storage unit, and a plurality of each of the plurality of reference parts in the X-ray image of the subject photographed with the phantom. An X-ray image processing unit for associating the pixel value with the pixel value.

In the X-ray imaging apparatus according to the second aspect of the present invention, as described above, the X-ray image processing unit performs the plurality of absorptions of the plurality of reference units in the X-ray image stored in the phantom information storage unit. The coefficient is configured to correspond to each of a plurality of pixel values of a plurality of reference portions of the phantom in the X-ray image obtained by capturing the subject together with the phantom. As a result, since the respective absorption coefficients of the plurality of reference portions of the phantom in the X-ray image correspond to the plurality of pixel values, the dose of X-rays changes and the position of the X-ray generator changes. However, for example, when correcting the pixel value in the X-ray image, the reference in the X-ray image can be prevented from being changed. As a result, a high-precision reconstructed image can be obtained, for example, when reconstructing a plurality of images due to a difference in reference between the plurality of images.

According to the present invention, as described above, even if the X-ray dose changes or the position of the X-ray generator changes, it is possible to prevent the reference in the X-ray image from being changed. A medical X-ray image processing device and an X-ray image capturing device can be provided.

FIG. 1 is a schematic diagram illustrating an overall configuration of an X-ray image capturing apparatus and an image browsing apparatus according to an embodiment. FIG. 1 is a block diagram illustrating an overall configuration of a medical X-ray image processing apparatus and an image browsing apparatus according to an embodiment. FIG. 3A is a perspective view showing a phantom including characteristic portions A, B, and C. FIG. FIG. 3B is a table showing absorption coefficients and sizes of phantom structure data. FIG. 4A is a table showing the absorption coefficients and target pixel values of the characteristic parts A, B, and C of the phantom. FIG. 4B is a graph showing a target pixel value function. FIG. 2 is a schematic diagram illustrating an X-ray image captured by the X-ray image capturing apparatus according to the embodiment. FIG. 6A is a table showing pixel value information of characteristic portions A, B, and C in the X-ray image. FIG. 6B is a table showing estimated pixel values of characteristic portions A, B, and C in the X-ray image. FIG. 6C is a graph showing estimated pixel value information in an X-ray image. 5 is a graph showing a target pixel value function and estimated pixel value information generated in the image browsing device according to the embodiment. FIG. 8A is a table showing a pixel value correction table. FIG. 8B is a graph showing a pixel value correction table. 5 is a flowchart illustrating an X-ray image processing flow in the image browsing device according to the present embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the configurations of the X-ray image photographing apparatus 1 and the image browsing apparatus 9 will be described with reference to FIGS.

(Configuration of X-ray imaging apparatus)
As shown in FIG. 1, the X-ray imaging apparatus 1 irradiates the subject 20 and the phantom 30 lying on the imaging table 3 with X-rays, and detects the X-rays transmitted through the subject 20 to thereby detect the subject 20 and the phantom 30. It is configured to shoot. The X-ray imaging apparatus 1 includes an imaging table 3, an X-ray source 4, a detector 5, an imaging system position changing mechanism 6, an imaging apparatus control unit 7, and a medical X-ray image processing apparatus 8. In the X-ray imaging apparatus 1, the length direction of the imaging table 3 is defined as an X direction, one of which is defined as an X1 direction, and the other is defined as an X2 direction. In the horizontal direction, a direction perpendicular to the X direction is defined as a Y direction, one of which is defined as a Y1 direction, and the other is defined as a Y2 direction. A direction perpendicular to the X direction and the Y direction is defined as a Z direction (vertical direction), one of which is defined as a Z1 direction (upward direction), and the other is defined as a Z2 direction (downward direction).

The X-ray source 4 is configured to irradiate the detector 5 with X-rays generated by applying a high voltage.

The detector 5 is configured to detect X-rays, convert the detected X-rays into electric signals, and read the converted electric signals as image signals. The detector 5 is, for example, an FPD (Flat @ Panel @ Detector). The detector 5 has a plurality of conversion elements (not shown) and pixel electrodes (not shown) arranged on the plurality of conversion elements. The plurality of conversion elements are arranged at a predetermined cycle (pixel pitch) such that the arrangement direction of the pixels matches the Y direction and the X direction. The plurality of pixel electrodes are arranged at a predetermined cycle (pixel pitch) such that the arrangement direction of the pixels matches the Y direction and the X direction. Further, the detector 5 is configured to output the acquired image signal to the medical X-ray image processing device 8.

The imaging system position changing mechanism 6 is configured to change the relative position between the X-ray source 4 and the detector 5 and the angle of the X-ray source 4 based on a signal from the imaging device control unit 7. The imaging system position changing mechanism 6 includes an X-ray source holding unit 6a that rotatably holds the X-ray source 4. Further, the imaging system position changing mechanism 6 includes an X-ray source moving unit 6b that moves the X-ray source holding unit 6a in the X direction. The X-ray source holding unit 6a holds the X-ray source 4 at one end so as to be rotatable, and the other end is movably held by the X-ray source moving unit 6b. The X-ray source holding unit 6a is configured such that, at one end, the X-ray source 4 is rotatable around an axis in the X direction. That is, the X-ray source holding unit 6a is configured to be able to change the irradiation angle of the X-ray source 4 by a signal from the imaging device control unit 7. Further, the X-ray source holding unit 6a is configured to be able to expand and contract in the Z direction. Therefore, the X-ray source holding unit 6a is configured to be able to change the position of the X-ray source 4 in the Z direction. The X-ray source moving unit 6b is configured to move the X-ray source holding unit 6a in the X direction according to a signal from the imaging device control unit 7.

The imaging device controller 7 is configured to perform X-ray imaging by irradiating the detector 5 with X-rays from the X-ray source 4. The imaging device control unit 7 is configured to change the relative position of the imaging system with respect to the subject 20 by moving the X-ray source 4 via the imaging system position changing mechanism 6. The imaging device control unit 7 includes, for example, a processor such as a CPU (Central Processing Unit). Note that the imaging system includes an X-ray source 4, a detector 5, and an imaging system position changing mechanism 6 that changes a relative position between the X-ray source 4 and the detector 5.

The medical X-ray image processing device 8 is configured to generate an X-ray image R (see FIG. 5) based on the image signal output from the detector 5. Further, the medical X-ray image processing device 8 is configured to acquire the position information of the characteristic portions A, B, and C (see FIG. 5) appearing in the plurality of X-ray images R. Further, the medical X-ray image processing device 8 is configured to generate a reconstructed image obtained by reconstructing a plurality of X-ray images R into one image. Here, the medical X-ray image processing apparatus 8 includes, for example, a processor such as a CPU, a GPU (Graphics Processing Unit), or an FPGA (Field-Programmable Gate Array) configured for image processing. The characteristic portions A, B, and C are examples of the “reference portion” in the claims.

Specifically, as shown in FIG. 2, the medical X-ray image processing device 8 includes an image acquisition unit 8a, an X-ray image generation unit 8b, a position information acquisition unit 8c, a reconstructed image generation unit 8d, A control unit 8e. The image acquisition unit 8a, the X-ray image generation unit 8b, the position information acquisition unit 8c, the reconstructed image generation unit 8d, and the control unit 8e are each a processing module (processor) of a processor such as an FPGA of the medical X-ray image processing device 8. ).

The image acquisition unit 8a is configured to acquire image signals of the subject 20 and the phantom 30 detected by the detector 5, and output the acquired image signals of the subject 20 and the phantom 30 to the X-ray image generation unit 8b. I have. That is, the image acquisition unit 8a has a function as an input / output device.

The X-ray image generation unit 8b is configured to generate an X-ray original image of the subject 20 and the phantom 30 based on the intensity distribution of the image signals of the subject 20 and the phantom 30 output from the image acquisition unit 8a. . Further, the X-ray image generation unit 8b corrects the pixel value of the X-ray original image by performing log conversion or the like on the X-ray original image and generates the X-ray image R. Then, the X-ray image generation unit 8b performs well-known image processing (for example, offset correction, gain correction, gradation correction, and the like) accompanying the imaging of the X-ray image R, and then performs the window level of the X-ray image R. And the window width is adjusted.

The position information acquisition unit 8c obtains position information in the X-ray image R of a plurality of characteristic parts A, B, and C provided on the phantom 30 arranged at a position where the phantom 30 is located along with the region of interest ROI (see FIG. 1) of the subject 20. Is configured to retrieve. The position information acquisition unit 8c is configured to acquire the position information of a plurality of characteristic portions A, B, and C by performing image recognition processing.

The reconstructed image generator 8d is configured to generate a reconstructed image in which a plurality of X-ray images R are reconstructed into one image. Specifically, the X-ray imaging apparatus 1 reconstructs a plurality of X-ray images R acquired by irradiating the subject 20 with X-rays from a plurality of different angles (for example, a shift addition method). By doing so, a reconstructed image is obtained.

The control unit 8e is configured to transmit a signal for the imaging device control unit 7 to perform X-ray imaging.

As shown in FIG. 3, the phantom 30 has a plurality of characteristic portions A, B, and C having different absorption coefficients. Here, the characteristic portions B and C are arranged inside the characteristic portion A. The absorption coefficient A1 of the characteristic portion A is made of a resin or the like having a value (for example, 100) having a smaller absorption coefficient than the characteristic portions B and C. The absorption coefficient B1 of the characteristic portion B is a heavy metal (gold, lead, tungsten, iron, copper, or the like) having a larger absorption coefficient than the characteristic portion A and a smaller absorption coefficient (eg, 800) than the characteristic portion C. ). The absorption coefficient C1 of the characteristic portion C is made of a heavy metal (for example, gold, lead, tungsten, iron, or copper) having a larger absorption coefficient (for example, 1000) than the characteristic portion B. The characteristic portion A has a larger size (for example, 50 [cm ³ ]) than the characteristic portions B and C. The characteristic portion B and the characteristic portion C have the same size (for example, 4 [cm ³ ]).

特徴 Thus, the characteristic portions A, B, and C are composed of X-ray absorbers having different absorption coefficients A1, B1, and C1 for absorbing X-rays. Thereby, when the phantom 30 is imaged, the doses of the X-rays absorbed by the characteristic portions A, B, and C are different, so that the characteristic portions A, B, and C can be detected in the X-ray image R. . In the phantom 30, the values of the absorption coefficients A1, B1, and C1 and the sizes of the characteristic portions A, B, and C described above are stored in the image viewing device 9 as phantom structure data 12a.

(Image viewing device)
As shown in FIGS. 1 and 2, the X-ray imaging apparatus 1 is provided in a separate room from the X-ray imaging room, and includes an image browsing apparatus 9 for browsing the X-ray image R and the reconstructed image. ing. The image browsing device 9 has the same function as the above-described medical X-ray image processing device 8 in that an X-ray image R is generated and a reconstructed image is formed. The image browsing device 9 is configured to acquire pixel value information of characteristic portions A, B, and C appearing in a plurality of X-ray images R. Further, the image browsing device 9 is configured to generate a reconstructed image obtained by reconstructing a plurality of X-ray images R into one image. The image browsing device 9 includes, for example, a processor such as a CPU, a GPU, or an FPGA configured for image processing. The image browsing device 9 includes an image acquisition unit 9a, a position information acquisition unit 9b, a reconstructed image generation unit 9c, a phantom information storage unit 9d, an X-ray image processing unit 9e, and a display unit 9f. The image acquisition unit 9a, the position information acquisition unit 9b, and the reconstructed image generation unit 9c are each configured as a processing module (processing processor) in a processor such as an FPGA of the image browsing device 9. The image browsing device 9 is an example of the “medical X-ray image processing device” in the claims.

The image browsing device 9 is communicably connected to the medical X-ray image processing device 8. Thereby, the image browsing device 9 acquires the X-ray image R generated by the medical X-ray image processing device 8.

The image browsing device 9 of the present embodiment is configured to convert the pixel value information of the subject 20 in the X-ray image R into desired pixel value information using a pixel value correction table. In the image browsing device 9, the image acquisition unit 9a, the position information acquisition unit 9b, and the reconstructed image generation unit 9c have the same configuration as that of the medical X-ray image processing device 8 described above. The configuration different from that described above will be described in detail below.

Specifically, the image browsing device 9 includes a phantom information storage unit 9d, an X-ray image processing unit 9e, and a display unit 9f.

<Phantom information storage unit>
The phantom information storage unit 9d mainly includes a processor such as the CPU 11, and a storage unit 12 such as an HDD (Hard Disc Drive) and a memory. In the phantom information storage unit 9d, the phantom structure data 12a is stored in the storage unit 12. That is, the phantom information storage unit 9d stores the plurality of absorption coefficients A1, B1, and C1 corresponding to the plurality of characteristic parts A, B, and C of the phantom 30 in the storage unit 12, respectively. Here, the plurality of absorption coefficients A1, B1, and C1 are stored in the storage unit 12 of the phantom information storage unit 9d when the user inputs. The phantom information storage unit 9d stores a plurality of sizes corresponding to the plurality of characteristic portions A, B, and C of the phantom 30 in the storage unit 12, respectively. Here, the plurality of sizes are stored in the storage unit 12 of the phantom information storage unit 9d when the user inputs. Note that the absorption coefficients A1, B1, and C1 may be stored in advance as set values. A plurality of sizes corresponding to each of the plurality of characteristic portions A, B, and C may be stored in advance as setting values.

<X-ray image processing unit>
The X-ray image processing unit 9e mainly includes a processor such as a CPU 13, and a storage unit 14 such as a HDD (Hard Disc Drive) and a memory. The storage unit 14 of the X-ray image processing unit 9e stores target pixel value function data 14a and X-ray image processing data 14b.

<Target pixel value function data>
As shown in FIGS. 4A and 4B, the target pixel value function data 14a includes a plurality of absorption coefficients A1, B1, and C1 set for a plurality of characteristic portions A, B, and C of the phantom 30. , A function (target pixel value function) indicating a relationship with a plurality of target pixel values Ta, Tb, Tc set corresponding to each of the plurality of absorption coefficients A1, B1, C1. The target pixel value function passes through coordinates Ax1 indicated by the value of the absorption coefficient A1 of the characteristic portion A and the target pixel value Ta of the characteristic portion A set by the user. The target pixel value function passes through coordinates Ax2 indicated by the value of the absorption coefficient B1 of the characteristic portion B and the target pixel value Tb of the characteristic portion B set by the user. The target pixel value function passes through coordinates Ax3 indicated by the value of the absorption coefficient C1 of the characteristic portion C and the target pixel value Tc of the characteristic portion C set by the user. As described above, the target pixel value function is a function passing through the coordinates Ax1, Ax2, and Ax3, and is a linear function passing through the coordinates Ax1, Ax2, and Ax3 in the example shown in FIG.

<X-ray image processing data>
The X-ray image processing unit 9e converts the pixel values of the X-ray image R including the phantom 30 including the characteristic portions A, B, and C and the subject (for example, the right hand) 20 illustrated in FIG. , Is configured to perform a process of correcting to a target pixel value on a target pixel value function. Here, the X-ray image processing unit 9e acquires the X-ray image R generated by the medical X-ray image processing device 8 via the image acquisition unit 8a.

The X-ray image processing unit 9e uses the X-ray image processing data 14b to generate the plurality of absorption coefficients A1, B1, and C1 of the plurality of characteristic portions A, B, and C in the X-ray image R, as shown in FIG. And a plurality of pixel values X, Y, and Z of each of the plurality of characteristic portions A, B, and C in the X-ray image R. Specifically, the X-ray image processing unit 9e specifies each position of the plurality of characteristic portions A, B, and C in the X-ray image R by the position information It is configured to acquire the pixel value of the specified location. Accordingly, the X-ray image processing unit 9e acquires a plurality of pixel values X, Y, and Z of each of the plurality of characteristic portions A, B, and C in the X-ray image R. Here, the plurality of pixel values X, Y, and Z are, for example, 90, 120, and 130, respectively.

As shown in FIG. 6B, the X-ray image processing unit 9e uses the X-ray image processing data 14b to generate a plurality of absorption coefficients A1, B1, C1, and a plurality of absorption coefficients A1, B1, C1, respectively. Is configured to obtain estimated pixel value information estimated based on a plurality of pixel values X, Y, and Z corresponding to. Specifically, the X-ray image processing unit 9e performs a known estimation process based on the X-ray image processing data 14b, and thereby obtains another pixel corresponding to an absorption coefficient other than the plurality of absorption coefficients A1, B1, and C1. Estimate the value. Then, the plurality of absorption coefficients A1, B1, C1, and other absorption coefficients, and the plurality of pixel values X, Y, Z, and other pixels corresponding to the plurality of absorption coefficients A1, B1, C1, and other absorption coefficients, respectively. A table in which values are associated with each other is estimated pixel value information (estimated pixel value table). That is, the estimated pixel value information is a look-up table indicating an absorption coefficient and a pixel value corresponding to the absorption coefficient.

Here, the estimated pixel value information displayed on the graph with the absorption coefficient on the horizontal axis and the pixel value on the vertical axis is the value of the absorption coefficient and the pixel value such that the curve shown in FIG. 6C is obtained. Suppose It should be noted that the estimated pixel value information is not necessarily the values of the absorption coefficient and the pixel value indicating a curve as shown in FIG.

As shown in FIGS. 7 and 8, the X-ray image processing unit 9e converts a plurality of pixel values X, Y, and Z corresponding to a plurality of characteristic portions A, B, and C into a plurality of target pixel values Ta, It is configured to correct to Tb and Tc. Specifically, each time the X-ray image processing unit 9e acquires the X-ray image R from the medical X-ray image processing device 8, the X-ray image processing unit 9e sets a plurality of pixel values X corresponding to a plurality of absorption coefficients A1, B1, and C1, Each of Y and Z is configured to acquire a pixel value correction table that is corrected to a plurality of target pixel values Ta, Tb, and Tc.

As shown in FIG. 8A, the pixel value correction table includes a plurality of estimated pixel values of the estimated pixel value information and a plurality of target pixel values on the target pixel value function corresponding to the plurality of estimated pixel values of the estimated pixel value information. Pixel value. For example, the pixel value correction table has 90 as the estimated pixel value in the characteristic portion A, and has 50 as the target pixel value corresponding to the estimated pixel value. For example, the pixel value correction table has 120 as an estimated pixel value in the characteristic portion B, and has 115 as a target pixel value corresponding to the estimated pixel value. For example, the pixel value correction table has 130 as the estimated pixel value in the characteristic portion C, and has 130 as the target pixel value corresponding to the estimated pixel value.

Further, the X-ray image processing unit 9e is configured to associate the plurality of estimated pixel values included in the estimated pixel value information with the plurality of target pixel values on the target pixel value function by the X-ray image processing data 14b. Have been. Specifically, the X-ray image processing unit 9e is configured to cause the pixel values other than the plurality of absorption coefficients A1, B1, and C1 to correspond to the target pixel values, respectively, using the pixel value correction table. . Thereby, the X-ray image processing unit 9e can correct the estimated pixel value corresponding to the subject 20 in the X-ray image R to the target pixel value based on the pixel value correction table. For example, the pixel value correction table has 110 as the estimated pixel value in the portion D of the subject 20, and has 80 as the target pixel value corresponding to the estimated pixel value.

Thus, the pixel value correction table associates the plurality of pixel values M, X, Y, Z and other estimated pixel values with the plurality of pixel values N, Ta, Tb, TC and other target pixel values. It is a table. That is, the pixel value correction table is a lookup table indicating the estimated pixel values and the target pixel values corresponding to the estimated pixel values. Thus, the X-ray image processing unit 9e can correct the estimated pixel value included in the estimated pixel value information to the target pixel value on the target pixel value function by using the X-ray image processing data 14b.

Here, the pixel value correction table displayed on a graph in which the estimated pixel value is set on the horizontal axis and the target pixel value is set on the vertical axis is such that the estimated pixel value and the target pixel value become a straight line shown in FIG. Is assumed. It should be noted that the pixel value correction table is not necessarily the value of the estimated pixel value and the target pixel value indicating a straight line as shown in FIG.

Further, the X-ray image processing unit 9e performs a known image process (for example, gradation correction) on the X-ray image R whose estimated pixel value has been corrected to the target pixel value according to the conversion of the X-ray image R. After that, the window level and the window width of the X-ray image R are adjusted. At this time, the X-ray image processing unit 9e determines the pixel values X, Y, and Z in the X-ray image R based on correspondence information that associates the plurality of absorption coefficients A1, B1, and C1 with the pixel values X, Y, and Z in the X-ray image R. The configuration of the image processing performed on the corrected X-ray image R in which Y and Z are corrected to the target pixel values Ta, Tb, and Tc is changed. Specifically, in the X-ray image processing unit 9e, the set value of the gradation correction and the like are changed according to the correspondence information so that the corrected X-ray image R is adjusted to an appropriate contrast.

<Display>
The display unit 9f includes an image display device such as a liquid crystal monitor, and is configured to display a screen based on the image output of the X-ray image processing unit 9e. Specifically, the display unit 9f displays the X-ray image R and the reconstructed image. Further, both the target pixel value function and the estimated pixel value information are displayed on the display unit 9f in a state as shown in FIG. That is, the display unit 9f displays the target pixel value function as a solid line and the estimated pixel value information as a dotted line on the graph. In the display unit 9f, the absorption coefficients A1, B1, C1, and D1 and the target pixel values Ta, Tb, and Tc are displayed as character data on a graph. On the display unit 9f, the pixel values X, Y, and Z included in the estimated pixel value information are displayed as character data on the graph. The display unit 9f displays the pixel value M before correction and the pixel value N after correction included in the estimated pixel value information as character data.

In the display unit 9f, the target pixel value function and the estimated pixel value information are displayed on a graph, but the target pixel value function and the estimated pixel value information are displayed on the screen using only straight lines and curves. There may be. The display unit 9f displays the target pixel value function as a straight line and the estimated pixel value information as a curve, but displays the target pixel value function as a straight line and displays the estimated pixel value information as a histogram. Is also good.

(Generation of reconstructed image)
Unlike the medical X-ray image processing device 8, the image browsing device 9 is configured to acquire a reconstructed image based on a plurality of X-ray images R corrected by the pixel value correction table. Here, in the image browsing device 9, a plurality of X-ray images R are required in order to generate a reconstructed image in which the reconstructed image generating unit 9c reconstructs the plurality of X-ray images R into one image. In this case, the X-ray image processing unit 9e performs an optimal pixel value correction for each of the plurality of X-ray images R so that each pixel value of the plurality of X-ray images R becomes a pixel value according to the target pixel value. Configured to apply a table. Specifically, the X-ray image processing unit 9e irradiates the phantom 30 and the subject 20 with X-rays from a plurality of different angles, thereby obtaining a plurality of X-ray images R each time. It is configured to acquire a pixel value correction table corresponding to each of the X-ray images R. Then, the X-ray image processing unit 9e is configured to correct each of the plurality of X-ray images R based on the pixel value correction table corresponding to each of the plurality of X-ray images R.

That is, in the X-ray image processing unit 9e, the target pixel values Ta, Tb, and Tc correspond to the plurality of absorption coefficients A1, B1, and C1 of the plurality of characteristic portions A, B, and C for each of the plurality of X-ray images R. Thus, a target pixel value function is obtained. In the X-ray image processing unit 9e, for each of the plurality of X-ray images R, the plurality of absorption coefficients A1, B1, and C1 of the plurality of characteristic portions A, B, and C are added to the pixel values X, Y, Estimated pixel value information is acquired in association with Z. The X-ray image processing unit 9e acquires a pixel value correction table for correcting the estimated pixel value included in the estimated pixel value information to a target pixel value on a target pixel value function for each of the plurality of X-ray images R. The X-ray image processing unit 9e corrects all the estimated pixel values included in the estimated pixel value information by using the pixel value correction table for each of the plurality of X-ray images R, so that the X-ray image processing unit 9e complies with a certain target pixel value (reference). The obtained X-ray image R is obtained.

This makes it possible to obtain a reconstructed image by reconstructing a plurality of X-ray images R in accordance with a fixed target pixel value. It is possible to suppress the occurrence of an artifact due to a change in the value.

(Flowchart of X-ray image processing flow)
Next, a flowchart of an X-ray image processing flow by the X-ray image processing unit 9e of the present embodiment will be described with reference to FIG. Note that the flowchart also describes a processing flow until the X-ray image processing unit 9e acquires the X-ray image R. Therefore, each process of the flowchart is performed by the X-ray image generation unit 8b of the medical X-ray image processing device 8 and the X-ray image processing unit 9e of the image browsing device 9.

Steps S1 to S5 are processes performed in the medical X-ray image processing apparatus 8.

In step S1, the X-ray image generation unit 8b obtains an original X-ray image of the phantom 30 and the subject 20 by X-ray detection via the image obtaining unit 8a. In step S2, the X-ray image generation unit 8b performs log conversion on the X-ray original image. In step S3, the X-ray image generation unit 8b acquires an X-ray image R by image processing in the X-ray image generation unit 8b. The X-ray image generation unit 8b performs, for example, gain correction, offset correction, and gradation correction as image processing. In step S4, the X-ray image processing unit 9e sets the window level and the window width of the X-ray image R. In step S5, the X-ray image generation unit 8b outputs the X-ray image R generated by the X-ray image generation unit 8b to the image viewing device 9.

Steps S6 to S18 are processes performed in the image browsing device 9.

In step S6, the X-ray image processing unit 9e acquires the pixel values of the plurality of characteristic portions A, B, and C of the phantom 30 from the acquired X-ray image R. In step S7, the X-ray image processing unit 9e acquires the absorption coefficients A1, B1, and C1 of the plurality of characteristic parts A, B, and C of the phantom 30 from the phantom information storage unit 9d. In step S8, the X-ray image processing unit 9e acquires target pixel value information corresponding to the absorption coefficient of the phantom 30. That is, in the X-ray image processing unit 9e, desired target pixel value information is set for each of the absorption coefficients A1, B1, and C1 of the plurality of characteristic portions A, B, and C of the phantom 30. In step S9, the X-ray image processing unit 9e acquires a target pixel value function based on the absorption coefficients A1, B1, C1, and the target pixel values Ta, Tb, Tc corresponding to the absorption coefficients A1, B1, C1.

In step S10, the X-ray image processing unit 9e acquires correspondence information in which the absorption coefficients A1, B1, and C1 of the phantom 30 correspond to the pixel values X, Y, and Z in the X-ray image R. The correspondence information includes the absorption coefficients A1, B1, and C1 of the characteristic portions A, B, and C of the phantom 30, and the pixel values X, of the characteristic portions A, B, and C of the phantom 30 in the X-ray image R, respectively. Y and Z are the corresponding data. In step S11, the X-ray image processing unit 9e determines in the X-ray image R from the absorption coefficients A1, B1, and C1 and the pixel values X, Y, and Z in the X-ray image R corresponding to the absorption coefficients A1, B1, and C1. Estimated pixel value information obtained by estimating all pixel values is obtained. That is, the estimated pixel value information is a pixel value estimated from the pixel values X, Y, and Z in the X-ray image R corresponding to the absorption coefficients A1, B1, and C1 by performing a known estimation process. In step S12, in the X-ray image processing unit 9e, the X-ray image processing unit 9e acquires a pixel value correction table for correcting a pixel value included in the estimated pixel value information into a pixel value on a target pixel value function.

において In step S13, the X-ray image processing unit 9e displays the estimated pixel value information and the target pixel value function on the display unit 9f. This makes it easier for the user to determine the necessity of correcting the pixel values in the X-ray image R using the pixel value correction table by comparing the estimated pixel value information with the target pixel value function. In step S14, the X-ray image processing unit 9e corrects the pixel value of the subject 20 using the pixel value correction table.

In step S15, the X-ray image processing unit 9e changes the setting of the image processing in the X-ray image processing unit 9e based on the correspondence information described above. For example, in the X-ray image processing unit 9e, the set value of the gradation correction is changed according to the corresponding information so that the contrast is adjusted appropriately for the corrected X-ray image R. In step S16, the X-ray image processing unit 9e corrects the X-ray image R by image processing in the X-ray image processing unit 9e. In step S17, the X-ray image processing unit 9e sets the window level and the window width of the X-ray image R, and the X-ray image processing flow ends.

(Effect of this embodiment)
In the embodiment of the present invention, the following effects can be obtained.

In the present embodiment, as described above, the X-ray image processing unit 9e generates the plurality of absorption coefficients A1 of the plurality of characteristic portions A, B, and C in the X-ray image R stored in the phantom information storage unit 9d. , B1, C1 and a plurality of pixel values X, Y, Z of a plurality of characteristic portions A, B, C in an X-ray image R in which the subject 20 is photographed together with the phantom 30. ing. As a result, since the respective absorption coefficients A1, B1, and C1 of the plurality of characteristic portions A, B, and C in the X-ray image R correspond to the plurality of pixel values X, Y, and Z, the X-ray dose changes. For example, even when the position of the X-ray source 4 is changed, the reference in the X-ray image R when correcting the pixel value in the X-ray image R can be prevented from being changed. As a result, a high-precision reconstructed image can be obtained, for example, when reconstructing a plurality of images due to a difference in reference between the plurality of images.

Further, in the present embodiment, as described above, the X-ray image processing unit 9e is configured to correct a plurality of pixel values corresponding to a plurality of absorption coefficients to a plurality of target pixel values, respectively. . As a result, the pixel in the X-ray image R is utilized by utilizing the mutual relationship between the plurality of target pixel values Ta, Tb, and Tc set for each of the plurality of characteristic portions A, B, and C of the phantom 30. When correcting the values to the target pixel values, not only the target pixel values Ta, Tb, and Tc corresponding to the plurality of absorption coefficients A1, B1, and C1, but also the target pixel values of the pixel values in the X-ray image R Can be set.

Further, in the present embodiment, as described above, the X-ray image processing unit 9e includes a plurality of absorption coefficients A1, B1, C1 corresponding to a plurality of characteristic portions A, B, C of the phantom 30, and a plurality of characteristic portions. The configuration is such that a target pixel value function is set based on a relationship with a plurality of target pixel values Ta, Tb, and Tc corresponding to A, B, and C. The X-ray image processing unit 9e converts the plurality of pixel values X, Y, and Z of each of the plurality of characteristic portions A, B, and C in the X-ray image R into the target pixel value based on the set target pixel value function. The target pixel values Ta, Tb, and Tc on the function are corrected. Thereby, a plurality of target pixel values Ta, Tb, and Tc can be handled as a target pixel value function associated with a plurality of absorption coefficients A1, B1, and C1, and thus information on the plurality of target pixel values Ta, Tb, and Tc is obtained. Can be easily obtained.

In the present embodiment, as described above, the X-ray image processing unit 9e corresponds to the plurality of absorption coefficients A1, B1, and C1 each time the X-ray image R in which the subject 20 is captured together with the phantom 30 is acquired. It is configured to acquire a pixel value correction table for correcting the plurality of pixel values X, Y, and Z into a plurality of target pixel values Ta, Tb, and Tc on the target pixel value function, respectively. Accordingly, by acquiring the pixel value correction table of the corresponding X-ray image R every time the X-ray image R is acquired, it is possible to acquire a plurality of X-ray images R in which the same reference pixel value is corrected. Therefore, when reconstructing a plurality of X-ray images R, a highly accurate reconstructed image can be easily obtained.

Further, in the present embodiment, as described above, when acquiring a plurality of X-ray images R by performing a plurality of X-ray imagings, the X-ray image processing unit 9e performs each time the plurality of X-ray images R are obtained. First, a pixel value correction table is obtained. The X-ray image processing unit 9e is configured to correct each of the plurality of X-ray images R based on a pixel value correction table corresponding to each of the plurality of X-ray images R. Thereby, even if each of the plurality of X-ray images R is corrected by the pixel value correction table obtained each time each of the plurality of X-ray images R is obtained, the pixel value correction table is stored in the plurality of phantoms 30. Since the X-ray images are acquired by the pixel values associated with the plurality of absorption coefficients A1, B1, and C1 of the characteristic portions A, B, and C, a plurality of X-ray images R having the same reference correction are acquired. be able to. As a result, for example, even when a plurality of X-ray images R are reconstructed to acquire a reconstructed image, it is possible to suppress the occurrence of artifacts (virtual images) in the reconstructed image.

Further, in the present embodiment, as described above, the X-ray image processing unit 9e includes the plurality of absorption coefficients A1, B1, and C1 of the plurality of characteristic portions A, B, and C of the phantom 30 in the X-ray image R. A pixel value correction table based on the estimated pixel value information of the X-ray image R estimated based on the plurality of pixel values X, Y, and Z corresponding to the plurality of absorption coefficients A1, B1, and C1, respectively. Is configured to obtain According to this configuration, an accurate pixel value correction table can be obtained based on the estimated pixel value information, so that the pixel values in the X-ray image R based on the pixel value correction table can be accurately corrected.

In the present embodiment, as described above, the image browsing device 9 includes the display unit 9f. The X-ray image processor 9e is configured to display both the target pixel value function and the estimated pixel value information on the display 9f. This allows the user to easily visually recognize the difference between the target pixel value function and the estimated pixel value information.

In the present embodiment, as described above, the X-ray image processing unit 9e corrects the plurality of pixel values X, Y, and Z into the plurality of target pixel values Ta, Tb, and Tc based on the correspondence information. The configuration of the image processing performed on the line image R is changed. Accordingly, image processing performed on the corrected X-ray image R can be appropriately performed.

(Modification)
It should be noted that the embodiments disclosed this time are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description of the embodiments, and includes all modifications (modifications) within the meaning and scope equivalent to the terms of the claims.

For example, in the present embodiment, an example has been described in which the target pixel value function is a linear function passing through the coordinates Ax1, Ax2, and Ax3, but the present invention is not limited to this. In the present invention, the target pixel value function may be a quadratic function, a cubic function, or the like.

Also, in the above-described embodiment, the example in which the subject 20 is the right hand has been described, but the present invention is not limited to this. In the present invention, the subject may be a left hand, a leg, a chest, an abdomen, or the like.

Further, in the present embodiment, the X-ray image processing unit 9e determines the plurality of absorption coefficients A1, B1, and C1 based on the correspondence information that associates the pixel values X, Y, and Z in the X-ray image R with each other. , The example in which the setting of the image processing performed on the X-ray image R in which the pixel values X, Y, and Z are corrected to the target pixel values Ta, Tb, and Tc is changed. It is not limited to this. In the present invention, the setting of the image processing performed on the X-ray image before being corrected by the pixel value correction table in the medical X-ray image processing apparatus may be changed.

Although the image browsing device 9 includes the X-ray image processing unit 9e in the present embodiment, the present invention is not limited to this. In the present invention, the medical X-ray image processing device may include the X-ray image processing unit.

In the present embodiment, the medical X-ray image processing device 8 and the image browsing device 9 are each configured to perform image processing on the X-ray image R, but the present invention is not limited to this. Not limited. In the present invention, only one of the medical X-ray image processing device and the image browsing device may perform the image processing on the X-ray image.

Further, in the present embodiment, for convenience of explanation, an example has been described in which the control processing of the X-ray image processing unit 9e is described using a flow-driven flowchart in which processing is sequentially performed along a processing flow. The invention is not limited to this. In the present invention, the control processing of the X-ray image processing unit 9e may be performed by event-driven (event-driven) processing that executes processing in event units. In this case, it may be performed in a completely event-driven manner, or may be performed in a combination of event-driven and flow-driven.

1 X-ray imaging apparatus 8 Medical X-ray image processing apparatus (image processing unit)
Reference Signs List 9 image browsing device 9d phantom information storage unit 9e X-ray image processing unit 9f display unit 20 subject 30 phantom A, B, C characteristic part (plural reference parts)
A1, B1, C1 Absorption coefficient R X-ray image Ta, Tb, Tc Target pixel value X, Y, Z pixel value

Claims

A phantom information storage unit that stores a plurality of absorption coefficients corresponding to each of the plurality of reference portions of the phantom including a plurality of reference portions having different X-ray absorption coefficients;
The plurality of absorption coefficients of each of the plurality of reference portions in the X-ray image stored in the phantom information storage unit, and each of the plurality of reference portions in the X-ray image of an object photographed with the phantom A medical X-ray image processing apparatus comprising: an X-ray image processing unit that associates a plurality of pixel values with each other.
The medical X-ray according to claim 1, wherein the X-ray image processing unit is configured to correct each of the plurality of pixel values corresponding to the plurality of absorption coefficients to a plurality of target pixel values. Image processing device.
The X-ray image processing unit includes a target set by a relationship between the plurality of absorption coefficients corresponding to the plurality of reference units of the phantom and the plurality of target pixel values corresponding to each of the plurality of absorption coefficients. The apparatus is configured to correct each of the plurality of pixel values of each of the plurality of reference portions in the X-ray image to a corresponding target pixel value on the target pixel value function based on a pixel value function. Item 3. The medical X-ray image processing apparatus according to item 2.
Each time the X-ray image processing unit acquires the X-ray image in which the subject is photographed together with the phantom, the plurality of pixel values corresponding to the plurality of absorption coefficients are respectively referred to as the target pixel value function. 4. The medical X-ray image processing apparatus according to claim 3, wherein the apparatus is configured to acquire a pixel value correction table for correcting the plurality of target pixel values.
The X-ray image processing unit, when acquiring a plurality of the X-ray images by a plurality of X-ray imaging, each time each of the plurality of X-ray images is obtained, acquires the pixel value correction table, The medical X-ray image processing apparatus according to claim 4, wherein the medical X-ray image processing apparatus is configured to correct each of the plurality of X-ray images based on the pixel value correction table corresponding to each of the plurality of X-ray images.
The X-ray image processing unit is based on the plurality of absorption coefficients of each of the plurality of reference units of the phantom in the X-ray image, and the plurality of pixel values corresponding to each of the plurality of absorption coefficients. The medical X-ray image processing apparatus according to claim 4, wherein the pixel value correction table is acquired based on estimated pixel value information of the X-ray image estimated by the X-ray image.
Further comprising a display unit,
The medical X-ray image processing apparatus according to claim 6, wherein the X-ray image processing unit is configured to display both the target pixel value function and the estimated pixel value information on the display unit.
The X-ray image processing unit, the plurality of absorption coefficients of each of the plurality of reference units stored in the phantom information storage unit, and the plurality of pixels of each of the plurality of reference units in the X-ray image The setting of image processing to be performed on the X-ray image in which the plurality of pixel values have been corrected to the plurality of target pixel values, based on the correspondence information in which the X values are corrected, or The medical X-ray image processing apparatus according to any one of claims 2 to 7, wherein a setting of image processing performed on the line image is changed.
An X-ray source,
A detector for detecting X-rays emitted from the X-ray source;
An image processing unit that acquires an X-ray image from the intensity distribution of the X-rays detected by the detector,
The image processing unit includes: a phantom information storage unit that stores a plurality of absorption coefficients corresponding to each of the plurality of reference units of the phantom including a plurality of reference units having different X-ray absorption coefficients; and the phantom information storage unit. The plurality of absorption coefficients of each of the plurality of reference portions in the stored X-ray image, and the plurality of pixel values of each of the plurality of reference portions in the X-ray image of the subject captured with the phantom. An X-ray image capturing apparatus, comprising: