JP2009165604A - X-ray diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray diagnostic apparatus capable of obtaining an X-ray image with stable contrast, regardless of the body thickness of a subject. <P>SOLUTION: An image processing means 3 includes: a diagnosis density range extracting means 31 for extracting a diagnosis density range for desired displaying at a prescribed density, regardless of the body thickness of the subject, based on a histogram (an input value histogram) corresponding to the input value of image data; an extension processing means 32 for obtaining an extension histogram corresponding to a conversion value where the diagnostic density range extracted by the diagnosis density range extracting means 31 is extended; an emphasis density range extracting means 33 for extracting the input value corresponding to an emphasis density range for desired displaying at the prescribed density, regardless of the body thickness of the subject, from the extension histogram obtained by the extension processing means 32; and a gradation processing means 34 for performing outputting, so as to allow the input value corresponding to the emphasis density range extracted by the emphasis density range extracting means 33 to be a prescribed gradation output value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an X-ray diagnostic apparatus that acquires an internal state of a subject as an X-ray image using X-rays. In particular, the present invention relates to an X-ray diagnostic apparatus capable of obtaining an X-ray image having a substantially constant and stable contrast regardless of a difference in body thickness of an object and an X-ray intensity.

  In the medical field or the like, an X-ray diagnostic apparatus that acquires an internal state of a subject as an X-ray image using X-rays is known. In particular, an X-ray diagnostic apparatus used for diagnosing a human body in the medical field targets various parts such as a chest, an abdomen, a head, and a limb. Usually, image processing is performed to convert image data obtained by photographing these photographing objects into an X-ray image having a gradation width that allows easy observation. As such image processing, for example, techniques described in Patent Documents 1 and 2 are known.

JP 2002-344807 A JP 2007-143952 A

  However, each subject to be photographed varies in body thickness depending on age, sex, physique, and the like. In the techniques described in Patent Documents 1 and 2, the X-ray image is affected by the difference in body thickness of the subject. A specific region of interest could not be displayed with a constant contrast. For this reason, the contrast of the region of interest is not stable, which may make interpretation difficult.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an X-ray diagnostic apparatus capable of displaying a region of interest as a stable contrast X-ray image regardless of the body thickness of the subject. .

The X-ray diagnostic apparatus of the present invention includes an X-ray irradiation means for irradiating a subject with X-rays, an X-ray detection means for detecting X-rays as an electrical signal (input value) corresponding to the intensity, and the X-ray detection. An X-ray diagnostic apparatus comprising: image processing means for creating an X-ray image based on image data detected by the means; and display means for displaying the X-ray image,
The image processing means includes a diagnostic density range extracting means for extracting a diagnostic density range based on an input value histogram corresponding to an input value of the image data, and a diagnostic density range extracted by the diagnostic density range extracting means is expanded. An expansion processing unit that obtains an expansion histogram corresponding to the converted value, an enhancement density range extraction unit that extracts an input value corresponding to the enhancement density range from the expansion histogram obtained by the expansion processing unit, and the enhancement density range extraction Gradation processing means for outputting an input value corresponding to the emphasized density range extracted by the means so as to become a predetermined gradation output value.

  Here, the diagnostic density range is a range of input values desired to be displayed at a predetermined density regardless of the body thickness of the subject among a plurality of input values constituting the image data. Further, the emphasized concentration range is a range of conversion values that are desired to be displayed at a predetermined concentration regardless of the body thickness of the subject among a plurality of conversion values obtained by converting the input values of the diagnostic concentration range.

  The expansion processing means includes an expansion conversion table generating unit that generates an expansion conversion table for expanding and converting and outputting the diagnostic density range, and a conversion for converting and outputting an input value by the expansion conversion table to obtain a conversion value histogram You may provide a value output part and the interpolation part which interpolates the said conversion value histogram and obtains an expansion | extension histogram.

  The enhancement density range extraction means converts an enhancement density range by an enhancement feature quantity extraction unit that identifies an enhancement density range from the extension histogram obtained by the interpolation unit, and an extension conversion table created by the extension conversion table creation unit. An inverse conversion unit that inversely converts a value into an input value.

  The gradation processing means includes a gradation conversion table creating unit that creates a gradation conversion table so that an input value corresponding to the emphasized density range becomes a predetermined gradation output value; A gradation conversion unit that converts and outputs an input value corresponding to the range to a predetermined gradation output value.

[About extraction of diagnostic concentration range]
A region important for interpretation is only a part of the image data. For example, it is assumed that, in X-ray image data, a specific organ of a subject is displayed with a substantially constant contrast regardless of the body thickness. In that case, the diagnostic concentration range extracting means specifies the input value range corresponding to the specific organ of the subject as the diagnostic concentration range from the created input value histogram. As a configuration for specifying the diagnostic concentration range, there are typically the following three configurations.

  First, the first configuration is a configuration in which a fixed value determined in advance according to the imaging region of the subject is used as the diagnostic concentration range. For example, since the head has little thickness variation due to the gender and physique of the subject, the diagnostic concentration range does not vary greatly depending on the subject, and the distance between the X-ray generation means and the X-ray detection means or during irradiation The diagnostic concentration range can be predicted from the X-ray dose.

  In the second configuration, an input value feature amount is extracted from the input value histogram, and a predetermined range including the input value feature amount is specified as the diagnostic concentration range. Examples of the input value feature amount include an input value having the maximum frequency in the input value histogram, an input value corresponding to an average value or a median value of the frequencies, and the like. A range having a predetermined width centered on the input value feature amount or a range having a predetermined width having the input value feature amount as an end point can be specified as the diagnostic concentration range.

  In the third configuration, the input value histogram is converted into a cumulative histogram, and in this cumulative histogram, a range of input values corresponding to a predetermined cumulative frequency range determined in advance according to the imaging region of the subject is set as the diagnostic concentration. It is the structure specified as a range. For example, when the imaging region is the lumbar spine, the predetermined cumulative frequency range is obtained empirically depending on the imaging region of the subject, such as a range of 10% to 70%.

[About expansion processing]
The expansion conversion table is used to temporarily convert an input value into a conversion value. During this conversion, the diagnostic density range is expanded to clarify the contrast of the diagnostic density range. This expansion conversion table is created to expand a portion of image data to be viewed with a certain contrast, and the expansion conversion table generation unit inputs an input value so that the specified diagnostic density range is expanded. A decompression conversion table that defines the correspondence between the value and the conversion value is created. For example, as described in an embodiment described later, the expansion conversion table is created so that the width of each conversion value is sufficiently wider than the width of the input value corresponding to the end point of the diagnostic concentration range.

[Specification of emphasized concentration range]
The emphasized density range extracting means is a means for specifying the input value from the converted value density range (emphasized density range) once converted when the input value range to be displayed on the display means as the output value having a predetermined gradation width is specified. It is. The emphasized density range extracting means first expands / interpolates the input value histogram, and specifies the emphasized density range in the expanded / interpolated conversion value histogram. As the configuration for specifying the emphasized density range, there are typically the following two configurations.

  First, the first configuration is a configuration in which a conversion value feature amount is extracted from a conversion value histogram, and a predetermined range including the conversion value feature amount is used as an emphasized density range. Examples of the conversion value feature amount include a conversion value having the maximum frequency in the conversion value histogram, a conversion value corresponding to an average value or a median value of the frequencies, and the like. Then, a range of a predetermined width centered on the converted value feature value or a range of a predetermined width having the converted value feature value as an end point can be specified as the emphasized density range.

  In the second configuration, the conversion value histogram is converted into a cumulative histogram, and in this cumulative histogram, a range of conversion values corresponding to a predetermined cumulative frequency range determined in advance according to the imaging region of the subject is emphasized concentration range. It is the structure specified as. The predetermined cumulative frequency range is obtained empirically according to the imaging region of the subject, for example, when the imaging region is the lumbar spine, the range is 10% to 90%.

[Inverse transformation]
The inverse conversion unit inversely converts at least a conversion value in the emphasized density range to an input value among conversion values obtained by expanding / interpolating the input value. In reverse conversion, the extension conversion table created by the extension conversion table creation unit is used.

[Creation of gradation conversion table]
The gradation conversion table is for converting an input value into an output value for actual display on the display means. In the present invention, an input corresponding to the specified emphasized density range by the gradation conversion table creation unit. A gradation conversion table is created so that values are converted into output values within a predetermined range.

[Other configurations]
The X-ray diagnostic apparatus of the present invention includes a direct line component removing unit that removes an input value (direct line component) based on an X-ray directly incident on the X-ray detecting unit from the X-ray irradiation unit. Preferably it is. The direct line component consists of an input value having a very large intensity due to the X-ray that has reached the X-ray detection means without passing through the subject, and is not directly involved in the diagnosis of the subject. Therefore, specifying the diagnostic density range including the direct line component can be a factor that makes the contrast of the final X-ray image unstable. Therefore, an X-ray image with more stable contrast can be obtained by removing the direct line component from the image data by the direct line component removing means.

  The X-ray diagnostic apparatus according to the present invention also includes an X-ray diaphragm means for limiting an X-ray irradiation area, and an input value (diaphragm component) in the detection element excluded from the irradiation area by the X-ray diaphragm means. It is preferable to include a diaphragm component removing unit that removes from the data. The diaphragm component is substantially composed of an input value having very small intensity, since the X-ray does not reach the X-ray detection means, and is not directly related to the diagnosis of the subject. This may cause image instability. Therefore, an X-ray image having a more stable contrast can be obtained by using an X-ray diagnostic apparatus including a diaphragm component removing unit.

  According to the X-ray diagnostic apparatus of the present invention, it is possible to display a region of interest as an X-ray image having a stable contrast regardless of the body thickness difference of the subject.

  The X-ray diagnostic apparatus according to the embodiment of the present invention will be described in detail below.

  As shown in FIG. 1, for example, the X-ray diagnostic apparatus 10 of the present embodiment includes an X-ray irradiation unit 1 that irradiates a subject M with X-rays, and the X-rays as electrical signals (input values) corresponding to the intensity. X-ray detection means 2 having a plurality of detection elements to be detected, image processing means 3 for creating an X-ray image based on image data consisting of a plurality of input values having various intensities detected by each detection element, A display means 4 for displaying the created X-ray image and a control means 5 for comprehensively controlling these means are provided. X-rays irradiated from the X-ray irradiation unit 1 pass through the subject M and enter the X-ray detection unit 2, and image data corresponding to the incident amount is output to the image processing unit 3. The image data is displayed on the display unit 4 as an X-ray image of the subject M by image processing by the image processing unit 3.

  By the way, image data (that is, input values) is converted into output values using a gradation conversion table so that a tissue of particular interest can be displayed with a predetermined gradation width among imaging regions (here, lumbar vertebrae) in a subject. To be done. The gradation conversion table is represented by a graph that protrudes toward the origin at the lower right with the horizontal axis as the input value and the vertical axis as the output value. Here, among the image data, the image data of the region other than the region of interest does not substantially contribute to the diagnosis of the subject. Therefore, the output value having a predetermined gradation width including the input value in the region other than the region of interest is included. When converted to, the contrast of the X-ray image becomes unstable. Therefore, the X-ray diagnostic apparatus 10 of the present invention uses the image processing unit 3 to create a gradation conversion table in which an optimum input value range is associated with an output value range having a predetermined gradation width, thereby stabilizing the contrast. An X-ray image capable of performing an accurate diagnosis on the subject can be obtained.

  The X-ray diagnostic apparatus 10 will be described in more detail. Although not shown, the X-ray irradiating means 1 has an X-ray tube that generates X-rays upon receiving power from a high-voltage generator, The specimen M is irradiated with X-rays. The X-ray irradiation means 1 is provided with an X-ray diaphragm means for adjusting the X-ray irradiation area, an additional filter for absorbing soft rays, and the like.

  The X-ray detection means 2 is composed of a plurality of detection elements, and in each detection element, X-rays are converted into an electrical signal (input value) corresponding to the incident amount and output to the image processing means 3. As the X-ray detection means, for example, a flat panel detector (FPD) or an imaging plate (IP) can be used. In particular, the FPD can automatically perform operations from detection of transmitted X-rays to output of input values to the image processing means. In addition, a combination of an image intensifier and a video camera can be used as X-ray detection means.

  The image processing means 3 includes direct line component removal means (not shown) for removing an input value (direct line component) based on X-rays directly incident on the X-ray detection means 2 from the X-ray irradiation means 1, and X A diaphragm component removing means (not shown) for removing an input value (aperture component) in the detection element excluded from the irradiation area by the line diaphragm means from the image data. Basically, as shown in FIG. 2, for example, based on a histogram corresponding to the input value of the image data (input value histogram), a diagnostic concentration range to be displayed at a predetermined concentration regardless of the body thickness of the subject. Obtained by the decompression processing unit 32, the decompression processing unit 32 for obtaining a decompression histogram corresponding to the converted value obtained by decompressing the diagnostic concentration range extracted by the diagnostic concentration range extraction unit 31, and the decompression processing unit 32. From the expanded histogram, an emphasized concentration range extracting unit 33 that extracts an input value corresponding to an emphasized concentration range to be displayed at a predetermined concentration regardless of the body thickness of the subject, and the enhancement extracted by the enhanced concentration range extracting unit 33. Gradation processing means 34 for outputting an input value corresponding to the density range to a predetermined gradation output value.

  The diagnostic density range extraction unit 31 includes a histogram creation unit 311 that creates an input value histogram and a diagnostic feature amount extraction unit 312 that identifies a diagnostic density range from the input value histogram. The expansion processing means 32 includes an expansion conversion table generating unit 321 that generates an expansion conversion table for expanding and converting the diagnostic density range, and a conversion value for converting and outputting an input value using the expansion conversion table to obtain a conversion value histogram. An output unit 322 and an interpolation unit 323 that obtains a stretched histogram by interpolating the conversion value histogram are provided.

  The enhancement density range extraction unit 33 uses the enhancement feature amount extraction unit 331 that identifies the enhancement density range from the extension histogram obtained by the interpolation unit 323, and the extension conversion table created by the extension conversion table creation unit 321. And an inverse conversion unit 332 for inversely converting the converted value into the input value. The gradation processing unit 34 includes a gradation conversion table creating unit 341 that creates a gradation conversion table in which an input value corresponding to the emphasized density range becomes a predetermined gradation output value, and the emphasized density range using the gradation conversion table. A gradation conversion unit 342 that converts and outputs an input value corresponding to the above to a predetermined gradation output value.

  The diagnostic feature quantity extraction unit 312 converts the input value histogram created by the histogram creation unit 311 into a cumulative histogram, and within this cumulative histogram, a predetermined cumulative frequency range determined in advance according to the imaging region of the subject. The corresponding input value range is specified as the diagnostic concentration range. The enhancement feature amount extraction unit 331 extracts a conversion value feature amount from the conversion value histogram obtained by the conversion value output unit 322, and specifies a predetermined range including the conversion value feature amount as an enhancement concentration range. The enhancement feature quantity extraction unit 331 converts the conversion value histogram obtained by the conversion value output unit 322 into a cumulative histogram, and within this cumulative histogram, a predetermined cumulative frequency range determined in advance according to the imaging region of the subject is obtained. The range of the corresponding conversion value is specified as the emphasized density range.

  The image processing procedure in the image processing means 3 will be described based on the flowchart shown in FIG. The step number in the flowchart is abbreviated as S1.

[Removal of diaphragm component (S1)]
A range of input values (aperture component) that could hardly be detected by the X-ray detection unit 2 from the entire input value range in the input value histogram by the aperture component removing unit (not shown) provided in the image processing unit 3. Remove. This diaphragm component is shielded by the X-ray diaphragm means inserted between the X-ray tube and the X-ray detection means 2 despite being irradiated from the X-ray tube toward the subject, and the X-ray detection means 2 is an input value component corresponding to X-rays that are hardly incident on 2. The removal of the aperture component can be performed using a known method, for example, a method of calculating from the positional relationship between the aperture position and the X-ray detection means 2.

[Removal of direct line components (S2)]
Direct line component removal means (not shown) provided in the image processing means 3 removes input value components (direct line components) attributed to the direct lines from the input values in the form of histograms. A direct ray is an X-ray incident on the X-ray detection unit 2 from the X-ray irradiation unit 1 without passing through the subject. The removal of the direct line component is a known method, for example, a method of obtaining the minimum value (threshold value) of the input value caused by the direct line from the X-ray irradiation conditions, and deleting the input value above the threshold, or the acquired detection This can be implemented by using a method of obtaining a threshold value from the feature amount of data and deleting an input value that is equal to or greater than a threshold value.

[Histogram of input values (S3)]
The diagnostic density range extraction means 31 creates a histogram of the image data (input value) input to the histogram creation unit 311 to create an input value histogram. The input value histogram in this step is a graph in which the horizontal axis corresponds to the input value and the vertical axis corresponds to the number (frequency) of pixels corresponding to the input value.

  An input value histogram that has undergone the above steps 1 to 3 is shown, for example, in FIG. As can be seen from FIG. 4, although the input values can take various intensities, the input values are concentrated in a very narrow intensity range. For this reason, if the input value is converted into the output value by the gradation conversion table creation unit 341 in such a state, it is difficult to display with a stable contrast for each tissue. Therefore, gradation conversion is performed after the following processing is performed. I have to.

[Cumulative histogram processing (S4)]
The diagnostic density range extraction means 31 creates a cumulative histogram from the input value histogram. In this cumulative histogram, for example, as shown in FIG. 5, the horizontal axis indicates the input value, and the vertical axis indicates the cumulative frequency. That is, the sum of appearance frequencies is calculated from the lower input value, and when the input value reaches the maximum value, the cumulative frequency becomes 100%.

[Specification of diagnostic concentration range (S5)]
The diagnostic concentration range extraction means 31 (diagnostic feature amount extraction unit 312) specifies a range of input values (diagnostic concentration range) corresponding to a tissue to be diagnosed with a clear contrast. Specifically, the first input value A and the second input value B that are input values corresponding to a predetermined cumulative frequency value are specified. In the present embodiment, the interval between the first input value A and the second input value B is regarded as a diagnostic concentration range. As the cumulative frequency value for specifying the diagnostic concentration range, a value corresponding to the imaging region of the subject obtained empirically from the accumulation of past data can be used. In the case of photographing the lumbar spine as in this embodiment, for example, 10% and 70%.

  As another method for specifying the diagnostic concentration range, an input value feature amount is extracted from the input value histogram created through steps 1 to 3, and the diagnosis concentration range is specified based on the input value feature amount. Good. For example, a predetermined range centering on the input value corresponding to the maximum frequency is specified as the diagnostic concentration range. Further, since the thickness of the head of the imaging target does not change so much depending on the subject, a fixed value can be used as the diagnostic concentration range. When the diagnostic concentration range is specified by these methods, it is not necessary to create a cumulative histogram, and thus step 4 described above can be omitted.

[Creation of conversion table (S6)]
In step 6, the extension conversion table creation unit 321 creates a conversion table to be used for histogram extension described later. The conversion table is used to convert the input value into a converted value once, expand the diagnostic density range at the time of conversion, and clarify the contrast between the input values within the diagnostic density range. In step 6, the expansion conversion table creation unit 321 creates a conversion table that specifically determines which input value corresponds to which conversion value. For example, as shown in FIG. 6, two control points P and Q are set at positions serving as inflection points of the curve indicating the conversion table, and each control point P and Q is an end point of the expansion range in the conversion value. It corresponds. Then, a conversion table is created so that the two control points P and Q correspond to the first input value A and the second input value B which are the end points of the diagnostic concentration range.

[Extension of Input Value Histogram (S7)]
The emphasized density range extracting means 33 converts all input values into converted values using the conversion table of FIG. 6, and creates an expanded histogram shown in FIG. This stretched histogram is a graph in which the horizontal axis represents the conversion value and the vertical axis represents the frequency.

[Interpolation of stretched histogram (S8)]
In the expanded histogram created in step 7, as shown in FIG. 7, the diagnostic density range is extended, the other ranges are compressed, and the diagnostic density range is discrete. Therefore, the expansion processing means 32 (interpolation unit 323) interpolates the expansion histogram to create an interpolation histogram as shown in FIG. The interpolation of the stretched histogram can be performed using a known method. For example, linear interpolation may be performed between discrete stretched histograms, adjacent data may be interpolated with either one of the data, or the interpolation target value may be predicted from surrounding data. You may interpolate nonlinearly. The created interpolation histogram is temporarily stored in the storage means.

[Cumulative histogram processing of interpolation histogram (S9)]
The interpolation feature histogram is converted into a cumulative histogram by the enhancement feature quantity extraction unit 331 (see FIG. 9). In this cumulative histogram, the horizontal axis represents the converted value, and the vertical axis represents the cumulative frequency.

[Specification of Enhanced Density Range (S10)]
In the cumulative histogram created in step 9, the emphasized feature amount extraction unit 331 specifies the first conversion value C and the second conversion value D, which are conversion values corresponding to a predetermined cumulative frequency value. In the apparatus of the present embodiment, the emphasized density range is between the first conversion value C and the second conversion value D. As the cumulative frequency value for specifying these conversion values C and D, a value corresponding to the imaging region of the subject obtained empirically from the accumulation of past data can be used, as in this embodiment. For example, when photographing the lumbar spine, it may be 10% and 90%.

  It should be noted that in the specification of the emphasized density range, the emphasized density range may be specified based on the converted value feature amount extracted from the interpolation histogram, as in another method for specifying the diagnostic density range. For example, a predetermined range centering on the converted value feature amount corresponding to the maximum frequency is specified as the emphasized density range. In this case, step 9 for converting the interpolation histogram into a cumulative histogram can be omitted.

[Inverse conversion of converted value to input value (S11)]
The inverse conversion unit 332 performs inverse conversion on the interpolation histogram created in step 8 using the conversion table created in step 6. During this inverse conversion, the third input value X and the fourth input value Y corresponding to the converted values C and D acquired in step 10 are acquired (see FIG. 6).

[Creation of gradation conversion table (S12)]
A gradation conversion table creating unit 341 creates a gradation conversion table for converting input values to output values. As shown in FIG. 10, the gradation conversion table is for displaying a tissue to be diagnosed of a subject with a predetermined gradation width. In this embodiment, the gradation conversion table creation unit 341 creates a gradation conversion table that specifically determines which input value corresponds to which output value. For example, as shown in FIG. 10, two control points R and S corresponding to an output range of a predetermined gradation width are set on a curve indicating a gradation conversion table. Then, a conversion table is created so that the two control points R and S correspond to the third input value X and the fourth input value Y. Note that, for R and S out of the range, R and the maximum value of the output value may be connected to S and the maximum value of the input value.

[Convert Input Value to Output Value (S13)]
Finally, the image processing means converts an input value into an output value using the gradation conversion table created in step 12, and displays the X-ray image by outputting it to the display means.

  According to the X-ray diagnostic apparatus of the present invention that performs image processing according to the flowchart described above, an X-ray image with a stable contrast can be displayed regardless of the difference in body thickness of each subject to be imaged. It should be noted that the present invention is not limited to the embodiment, and can be freely improved, changed, etc. as necessary without departing from the gist of the invention.

  The X-ray diagnostic apparatus of the present invention can be used for taking an X-ray image of a subject and diagnosing the subject using the X-ray image.

It is a schematic block diagram of the X-ray diagnostic apparatus of this invention. It is a block diagram of the image processing means. It is a flowchart about the image processing procedure of the detection signal acquired by the X-ray imaging. It is the schematic which shows the input value histogram. It is the schematic which shows the accumulation histogram about the same input value. It is the schematic which shows the conversion table. It is the schematic which shows the expansion | extension histogram. It is the schematic which shows the same interpolation histogram. It is the schematic which shows the accumulation histogram about the conversion value. It is the schematic which shows the same gradation conversion table.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray irradiation means 2 X-ray detection means 3 Image processing means 4 Display means 5 Control means 10 X-ray diagnostic apparatus M Subject 31 Diagnosis density range extraction means 32 Extension processing means 33 Enhancement density range extraction means 34 Tone processing means 311 Histogram creation unit 312 Diagnostic feature amount extraction unit 321 Extension conversion table creation unit 322 Conversion value output unit 323 Interpolation unit 331 Enhancement feature amount extraction unit 332 Inverse conversion unit 341 Tone conversion table creation unit 342 Tone conversion unit P, Q, R , S Control point A 1st input value B 2nd input value X
Third input value Y Fourth input value C First conversion value D Second conversion value

Claims (6)

Based on X-ray irradiation means for irradiating the subject with X-rays, X-ray detection means for detecting X-rays as electrical signals (input values) corresponding to the intensity, and image data detected by the X-ray detection means An X-ray diagnostic apparatus comprising: image processing means for creating an X-ray image; and display means for displaying the X-ray image,
The image processing means includes
A diagnostic concentration range extracting means for extracting a diagnostic concentration range based on an input value histogram corresponding to an input value of the image data;
Expansion processing means for obtaining an expansion histogram corresponding to a converted value obtained by extending the diagnostic concentration range extracted by the diagnostic concentration range extraction means;
An enhancement density range extraction means for extracting an input value corresponding to the enhancement density range from the extension histogram obtained by the extension processing means;
An X-ray diagnostic apparatus comprising: gradation processing means for outputting an input value corresponding to the emphasized density range extracted by the emphasized density range extracting means so as to become a predetermined gradation output value. The decompression processing means includes
An extension conversion table creating unit for creating an extension conversion table for extending the diagnostic concentration range and converting it;
A conversion value output unit that converts and outputs an input value by the extension conversion table to obtain a conversion value histogram;
The X-ray diagnostic apparatus according to claim 1, further comprising: an interpolation unit that interpolates the conversion value histogram to obtain an expanded histogram. The emphasized concentration range extracting means includes:
An emphasis feature amount extraction unit that identifies an emphasis density range from the expanded histogram obtained by the interpolation unit;
The X-ray diagnostic apparatus according to claim 2, further comprising: an inverse conversion unit configured to inversely convert a conversion value of the emphasized density range into an input value using the expansion conversion table generated by the expansion conversion table generation unit. The gradation processing means includes
A gradation conversion table creating unit that creates a gradation conversion table such that an input value corresponding to the emphasized density range becomes a predetermined gradation output value;
The X-ray diagnostic apparatus according to claim 1, further comprising: a gradation conversion unit that converts and outputs an input value corresponding to an emphasized density range to a predetermined gradation output value by the gradation conversion table.   4. The enhancement feature amount extraction unit according to claim 3, wherein the enhancement feature amount extraction unit extracts a conversion value feature amount from the conversion value histogram obtained by the conversion value output unit, and specifies a predetermined range including the conversion value feature amount as an enhancement concentration range. X-ray diagnostic equipment.   The enhancement feature amount extraction unit converts the conversion value histogram obtained by the conversion value output unit into a cumulative histogram, and in the cumulative histogram, a predetermined cumulative frequency range determined in advance according to the imaging region of the subject is obtained. The X-ray diagnostic apparatus according to claim 3, wherein a range of corresponding conversion values is specified as an emphasized concentration range.

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