JP2017018417A - X-ray imaging apparatus and medical image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray imaging apparatus capable of reducing an arithmetic load of image processing in frequency enhancement processing of X-ray imaging or the like and performing high-speed processing.SOLUTION: An image processing section 130 of the X-ray imaging apparatus includes a frequency enhancement processing part 133 for performing, to an X-ray signal, processing of enhancing a specific frequency component. The frequency enhancement processing part 133 creates a range summation table using the X-ray signal, and creates a blur image signal of one or a plurality of frequency bands using the range summation table. The frequency enhancement processing part 133 performs dynamic range compression and the frequency enhancement using both of the blur image signal and the X-ray signal. The number of blur image signals to be created and the frequency bands are determined according to a site of an examination object.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image processing technique for medical images such as X-ray images, and more particularly to a technique for speeding up dynamic range compression and frequency enhancement processing.

  The X-ray imaging apparatus obtains an X-ray signal of the subject by irradiating the subject with X-rays and detecting the X-ray transmitted through the subject with an X-ray detector. By performing image processing on the X-ray signal, an X-ray image (still image) or a fluoroscopic image (moving image) displayed on the display device can be obtained.

  Basic image processing for X-ray signals includes gamma correction and brightness adjustment, and dynamic range compression and frequency enhancement. Dynamic range compression is a technique for extracting a low-frequency component of an X-ray signal and correcting the X signal based on the extracted information, and frequency enhancement is performed at a predetermined frequency according to the fineness of the structure of the part of interest. This is a technique for rendering components with high contrast. By using these techniques, a higher-quality X-ray image can be obtained. In both dynamic range compression and frequency enhancement, a blurred image signal called a blurred mask or a non-sharp mask signal is used.

  For example, in Patent Document 1, a multi-resolution blur image signal having different frequency response characteristics is created for an image signal (X-ray signal) representing an original image, and a plurality of frequencies are generated from the blur image signal and the original image. A method of frequency enhancement processing is disclosed in which a band limited image signal that is a signal for each band is calculated, and a band-limited image signal multiplied by a predetermined coefficient (enhancement coefficient) is added. Further, the technique of Patent Document 1 describes that a blurred image signal is created using filtering by a low-pass filter (LPF). Specifically, a multi-resolution blurred image signal having the same size as the original image is obtained by repeating the LPF processing a plurality of times and performing an interpolation operation on the obtained filtered image signal.

Japanese Patent No. 3816151

  In general, a medical imaging apparatus such as an X-ray imaging apparatus may perform continuous imaging and display an obtained image as a moving image on a display device. In the X-ray imaging apparatus, such continuous imaging is called fluoroscopy, and real-time fluoroscopic image display can be obtained by imaging and displaying at a high frame rate.

  In the fluoroscopic image, when the frequency enhancement processing using the multi-resolution blurred image signal described above is performed in order to improve the image quality, the time required for obtaining the blurred image signal becomes long, and thus the real-time property is impaired. Therefore, it is difficult to adopt dynamic range compression and frequency enhancement in perspective that emphasizes real-time characteristics, and image quality must be sacrificed.

  An object of the present invention is to provide an image processing technique capable of performing frequency enhancement processing even for an image that requires high-speed processing such as a fluoroscopic image. Also, it is an object to provide an image processing technology that can simultaneously perform dynamic range compression and frequency enhancement processing that have been performed separately for normal X-ray images at the same time, thereby reducing the burden of image processing. To do.

  In order to solve the above-described problem, the present invention does not create a blur image signal for each of a plurality of frequencies, but creates one range sum table, and from the range sum table, only a blur image signal of a necessary frequency is generated. The time required to create a plurality of blurred image signals is shortened.

  That is, the X-ray imaging apparatus of the present invention includes an X-ray source that irradiates X-rays, an X-ray detector that is disposed to face the X-ray source and detects X-rays that have passed through an inspection object, and the X detection. An image processing unit that processes an X-ray signal output from the scanner and creates an X-ray image, and the image processing unit uses the X-ray signal to generate an X-ray having a specific frequency in the X-ray image. A frequency enhancement processing unit for enhancing an image, wherein the frequency enhancement processing unit uses the X-ray signal to create a range summation table, and uses the range summation table to create one or more A mask creation unit that creates a blurred image signal of frequency, and performs frequency enhancement using the X-ray signal and the blurred image signal.

  According to the present invention, only a blurred image signal having a frequency required according to a region to be inspected or a purpose of diagnosis is generated and the frequency enhancement processing is performed. Therefore, the burden of the image processing is reduced and the frequency enhancement processing is reduced. When the image is a moving image such as a perspective image, the frame rate can be greatly improved. In addition, when there is a margin in the still image or the frame rate, the image quality can be improved by increasing the types of blurred image signals to be created.

  Also, by using the created blurred image signal for dynamic range compression processing, dynamic range compression and frequency enhancement processing can be performed at the same time, and an image with good image quality can be provided in a short image processing time.

The figure which shows the whole outline of the X-ray imaging device Functional block diagram of the image processing unit Flow showing operation of image processing unit of first embodiment The figure explaining the creation process of the range total table (SAT) Diagram explaining properties of range summation table Functional block diagram of the image processing unit of the second embodiment Flow showing operation of image processing unit of second embodiment Flow showing operation of image processing unit of third embodiment The figure which shows the example of a display screen in 3rd embodiment (modification)

Hereinafter, embodiments in which the present invention is applied to an X-ray imaging apparatus will be described.
An X-ray imaging apparatus according to the present embodiment includes an X-ray source that irradiates X-rays, an X-ray detector that is disposed opposite to the X-ray source and detects X-rays that have passed through an inspection target, and an X-ray detector An image processing unit that processes an X-ray signal output from the image processing unit and generates an X-ray image. The image processing unit includes a frequency enhancement processing unit that enhances an X-ray image of a specific frequency in the X-ray image using the X-ray signal, and the frequency enhancement processing unit uses the X-ray signal to A table creation unit that creates a sum table, and a mask creation unit that creates a blur image signal of one or more frequencies using the range sum table, and uses the X-ray signal and the blur image signal Frequency emphasis.

  FIG. 1 shows an overall outline of an example of an X-ray imaging apparatus to which the present invention is applied. The X imaging apparatus includes a top plate 106 on which the subject 100 is placed, an X-ray source 102 that irradiates the subject 100 with X-rays, an aperture device 104 that sets an X-ray irradiation area for the subject 100, and power to the X-ray source 102. An X-ray detector 110 for detecting X-rays transmitted through the subject 100, and an X-ray output from the X-ray detector 110. The image processing unit 130 that performs image processing on the signal and outputs an X-ray image, the display unit 160 that displays the X-ray image, the operations of the high voltage generation unit 108, the image processing unit 130, and the display unit 160 described above. A control unit 120 for controlling, an operation unit 170 for inputting an instruction required by an operator (inspector) to the control unit 120, and an image storage unit 180 for storing an X-ray image output from the image processing unit 130. It is equipped with a.

  The X-ray source 102 includes, for example, an X-ray tube such as a rotating anode X-ray tube and a supporting device thereof, and generates X-rays upon receiving power supply from the high voltage generator 108. The tube current and tube voltage supplied to the X-ray tube can be adjusted by the operator sending a command to the control unit 120 via the operation unit 170 and controlling the high voltage generation unit 108. The X-ray source 102 may include an X-ray filter that selectively transmits X-rays having specific energy.

  The aperture device 104 has a plurality of X-ray shielding lead plates that shield the X-rays emitted from the X-ray source 102, and the opening position and area are changed by moving each of the plurality of lead plates, and the subject The X-ray irradiation area for 100 is determined.

  The X-ray detector 110 is a device that has a structure in which a plurality of detection elements for detecting X-rays are arranged in a two-dimensional array, and outputs an X-ray signal corresponding to the X-ray dose incident on each detection element. . Specifically, an FPD (Flat Panel Detector) or the like is used. The X-ray signal output from the X-ray detector 110 by one X-ray irradiation on the subject corresponds to one X-ray image, and is original image data having the number of pixels determined by the size of the two-dimensional array. In the case of a fluoroscopic FPD, for example, the image data has a size of 1024 × 1024.

  The image processing unit 130 performs image processing on the X-ray signal output from the X-ray detection unit 110, and outputs an image-processed X-ray image. Image processing performed by the image processing unit 130 includes gamma conversion, gradation conversion, image enlargement / reduction, and the like. The image processing unit 130 according to the present embodiment, in addition to these processes, performs dynamic range compression, Perform frequency enhancement. The function of the image processing unit 130 for realizing the image processing will be described in detail later, but can be realized by software. In that case, the X-ray signal output from the X-ray detection unit 110 is converted into a digital signal by an A / D conversion circuit (not shown) and input to the image processing unit 130. Note that some of the functions of the image processing unit 130 may be replaced with software, and may be configured with an analog circuit such as an ASIC (application specific integrated circuit) or an FPGA (field-programmable gate array).

  The image storage unit 180 stores the X-ray image output from the image processing unit 130, information attached to the X-ray image, and the like. The display unit 160 inputs the X-ray image output from the image processing unit 130 or reads and displays the X-ray image from the image storage unit 180, and includes a display device such as a CRT or a liquid crystal display. When the display unit 160 is a display device with a touch panel, some or all of the functions of the operation unit 170 can be provided.

  The operation unit 170 includes one or more input devices such as a keyboard, a touch panel, and a mouse, receives an operation by an operator, and sends a signal corresponding to the operation to the control unit 120.

  The control unit 120 controls each unit constituting the above-described X-ray imaging apparatus, and includes a CPU and an internal storage device associated therewith. Specifically, the control of each unit includes the control of the high voltage generation unit 108, the control of the display unit 160, etc., all of which can be realized by software installed in the CPU.

  FIG. 2 is a functional block diagram showing a configuration example when the image processing unit 130 and the control unit 120 are configured by software. In this configuration example, the control unit 120 includes a main control unit 121, an imaging control unit 123, and a display control unit 125. The imaging control unit 123 is a function for controlling the high voltage generation unit 108 and controls imaging conditions (tube current, tube voltage), imaging timing, and the like. The display control unit 125 is a function for controlling display on the display unit 160. The display control unit 125 controls the image processing unit 130 to change the size of the X-ray image, change the file format, etc. for display on the display unit 160. Display control of characters and annotation images displayed superimposed on the X-ray image, that is, control of display position, display size, and the like is performed. The character or annotation image may be stored in advance in the image storage unit 180, for example, or can be created from information stored in the image storage unit 180 as supplementary information of the X-ray image.

  As shown in FIG. 2, the image processing unit 130 temporarily stores the X-ray signal input from the X-ray detector 110, and emphasizes the X-ray signal of a specific frequency among the input X-ray signals. A frequency enhancement processing unit 133 that outputs an X-ray signal, a mask creation unit 135 that creates a blurred image signal used by the frequency enhancement processing unit 133, and a range summation table for the mask creation unit 135 to create a blur image signal The table creation unit 137 is provided. The image processing unit 130 can further include a dynamic range compression processing unit 134 that performs dynamic range compression of a predetermined frequency component, a gamma correction unit 132 that performs gamma correction on an X-ray signal, and the like. The image processing unit 130 according to the present embodiment has a configuration in which the frequency enhancement processing unit 133 performs frequency enhancement processing and simultaneously performs dynamic range compression processing, and the dynamic range compression processing unit 134 is described as part of the frequency enhancement processing unit 133. Has been.

  The frequency emphasis processing unit 133 performs processing for emphasizing a predetermined frequency component of the X-ray signal including a plurality of frequency components. The frequency component to be emphasized can be set by the inspector via the operation unit 170, and can be automatically set by determining the part to be imaged.

Specifically, the frequency enhancement process is a process of creating a frequency enhanced image by calculation using the following equation (1) when the frequency component included in the X-ray signal is Fn and the enhancement degree is αn. .
Frequency-enhanced image = original image + Σα _n × frequency component Fn (1)
In the formula, “n” of Fn and αn is an integer from 1 to N, where N is the number of frequency components included (hereinafter the same). Further, the frequency component Fn of Expression (1) is obtained by multiplying the original image (input X-ray signal) by a blurred image signal having a predetermined frequency.

The dynamic range compression processing unit 134 performs a dynamic range compression while applying a correction coefficient to an X-ray signal in a predetermined frequency region according to an examination site and maintaining contrast in the frequency region. A correction coefficient corresponding to a predetermined frequency region is calculated from a blurred image signal having a predetermined frequency. Specifically, when a blurred image signal having a predetermined frequency is BM, the correction coefficient f is a BM function f (BM) as expressed by, for example, Expression (2).
f = a × BM + b (2)
In equation (1), a and b are adjustable constants that can each include a negative value.

  The mask creating unit 135 creates a blurred image signal used for dynamic range compression processing and a blurred image signal used when the frequency enhancement processing unit 133 calculates frequency components. The enhancement frequency may be received by the image processing unit 130 via the operation unit (input unit) 170, or when a region to be imaged is determined, a predetermined enhancement frequency may be selected accordingly. .

  The blurred image signal is also called a blurred mask. When expressed by two-dimensional image data corresponding to an X-ray image, the image data is divided into small areas (masks), and a simple average value of pixels in the small areas is calculated. It is a simple average filter that uses pixel values in a small area. The mask size is determined by the number of pixels in the vertical and horizontal directions of the small area, and the frequency component varies depending on the size of the mask. The blurred image signal is likely to include a higher frequency component as the mask size is smaller, and more likely to include a lower frequency component as the mask size is larger. The larger the mask size, the longer it takes to create it. If the frequency emphasis processing unit 133 tries to prepare a blur mask for all of a plurality of settable frequency components, the burden of mask creation becomes very large.

  The mask creation unit 135 uses a range sum table (SAT: Summed Area Table, hereinafter referred to as SAT) created by the table creation unit 137 according to the set frequency component, and outputs a blurred image signal corresponding to the frequency. Create on demand. The structure of the SAT created by the table creation unit 137 will be described in each embodiment of the image processing unit described below.

<First embodiment>
Based on the above configuration, a first embodiment of the processing procedure of the image processing unit of the X-ray imaging apparatus will be described. FIG. 3 shows the flow of processing.

  First, when examination is started, X-rays irradiated from the X-ray source 102 and transmitted through the subject 100 are detected by the X-ray detector 110 and output as X-ray signals. The image processing unit 130 inputs this X-ray signal as X image data (S301).

  The table creation unit 137 of the image processing unit 130 creates a SAT using the input X-ray image data (original image data) (S302). The SAT creation procedure will be described with reference to FIG. Here, in order to simplify the description, a case where the SAT 200 is created based on an image having 8 pixels per side is shown. Also, the pixel value of the original image (input X-ray signal) 210 will be described as “1”.

  First, the pixel values of the original image 210 are sequentially added in the row direction (from the left to the right in the figure), and a row direction total table 230 is obtained in which the sum total is the value of the pixel. For example, in the row direction total table 230, the pixel value of the second pixel from the left is “1 + 1 = 2”, the pixel value of the third pixel is “2 + 1 = 3”, and the pixel value of the rightmost pixel is This is the sum of the pixel values in that row (“4” in the example of FIG. 4). Next, the row direction total table 230 obtained in this way is sequentially added in the column direction (from top to bottom in the figure), and a column direction total table 250 having the sum as a value of the pixel is obtained. For example, in the column direction total table 250, since the pixel values in the second column from the left in the row direction total table 230 are all “2”, “2”, “2 + 2 = 4” in order from the upper pixel. , “2 + 2 + 2 = 6”,... “2 × 8 = 16”.

  Thus, the table 250 that is the result of performing the summation in the row direction and the summation in the column direction for each pixel is the SAT 200. Note that FIG. 4 shows a case where the row direction total table is first created and then the column direction total table is created. However, in the opposite case, the sum in the row direction is added to the column direction total table. The table created by the execution becomes SAT200.

  When the SAT 200 cuts out a region 201 of a predetermined size (region shown by gray surrounded by a dotted line in the figure) as shown in FIG. The average value is equal to the average value of all the pixels in the region 201. In addition, the pixel value of the region D located at the lower right among the regions A to D obtained by dividing the predetermined region into four parts is determined from the sum of the pixel value of the region D and the pixel value of the region A at the upper left of the region D Is obtained by subtracting the sum of the pixel values of regions B and C adjacent to the upper and left sides. This is a property of the SAT that holds regardless of the size of the area. By using this property of the SAT 200, it is possible to create a blurred image signal having an arbitrary mask size (filter size in terms of frequency).

Specifically, the blurred image signal B _M can be calculated using the following equation (3), where SAT is S _sat and the filter size for creating the blurred image signal is M.

  The mask creation unit 135 creates an arbitrary number of blurred image signals by varying the filter size M in Expression (3) according to the frequency band (S303).

  The dynamic range compression unit processing unit 134 uses the predetermined blurred image signal created by the mask creation unit 135 to create the dynamic range compression table (correction coefficient) f using, for example, Equation (1) described above (S304). ).

  The frequency enhancement processing unit 133 performs frequency enhancement processing using the blurred image signal created by the mask creation unit 135 and the dynamic range compression table (S305).

Here, when the filter sizes of the plurality of blurred image signals created by the mask creating unit 135 are M1 and M2 (M1> M2), the blurred image signals B _M1 (i, j) and B _M2 (i, j) Can be obtained by B _M1 (i, j) −B _M2 (i, j). Therefore, assuming that the filter size to be divided into multiple frequency bands is M1 to Mn, the enhancement coefficient of each frequency band is β1 to βn-1, and the dynamic range compression table (correction coefficient) is f, multifrequency processing and dynamic range compression The output image D (i, j) obtained by the processing can be obtained by the following equation (4).

  The image data that has been subjected to dynamic range compression processing and frequency enhancement processing in this way is output from the image processing unit 130 as output image data and displayed on the display unit 160 (S306).

  According to this embodiment, it is possible to perform frequency enhancement processing together with dynamic range compression by SAT without creating a multi-resolution blurred image signal, and it is possible to greatly reduce the calculation cost for creating output image data. Also, once the SAT is created, a blurred image signal with an arbitrary frequency band and filter size can be created. Therefore, frequency enhancement is performed according to the part that the operator wants to observe without increasing the calculation cost. It is also possible to change the processing contents.

  The present embodiment can be applied not only to X-ray images shot in a single shot, but also to continuous shot images that need to process several frames in one second, and perspective imaging that displays a moving image at a predetermined frame rate. The processing time can be shortened and the frame rate can be improved. As an example, in the case of a fluoroscopic image having a size of input image data of about 1024 × 1024, the conventional filtering processing requires about 33 mS for processing one image, and an image display frame rate of 30 sps (frame / second) or more is realized. However, according to the present embodiment, it is possible to display a fluoroscopic image at a frame rate of 30 to 60 sps if the sizes are comparable.

<Second embodiment>
The present embodiment is characterized in that the frequency processing unit can vary the number of frequency bands to be divided depending on the part under examination. That is, the mask creation unit of the frequency processing unit creates a blurred image signal having a frequency corresponding to the part. The blurred image signal having a frequency corresponding to the part can be determined with reference to, for example, a predetermined relationship between the part to be examined and the enhancement frequency. The relationship between the part and the frequency may be stored as a reference table, for example, or the number of frequency bands may be determined in advance for each part code of X-ray imaging. It is also possible for the operator to specify the number of frequency bands to be divided according to the imaging region.

  The part code is a code indicating an imaging part such as the chest, head, abdomen, leg, etc. Generally, in an X-ray imaging apparatus, an imaging condition and an imaging mode suitable for each part are selected according to the part code. . The frequency band of the blurred image signal or the reference table can be stored as information attached to such a part code, for example. The storage device for storing such information may be the image storage unit 180 shown in FIG. 2 or a storage device including other external devices.

  A configuration example of the image processing unit 130 of the present embodiment is shown in FIG. In FIG. 6, elements common to the functional block diagram shown in FIG. 2 are denoted by the same reference numerals, and redundant description is omitted. The image processing unit 130 of this embodiment includes a storage unit 131 that temporarily stores an input X-ray signal (original image), and a frequency enhancement processing unit that performs frequency enhancement processing on the X-ray signal and performs dynamic range compression processing. 133, a dynamic range compression processing unit 134, a mask creation unit 135 that creates a blurred image signal, a table creation unit 137 that creates a SAT, and a site determination unit 139 that determines the site of the original image. The mask creation unit 135 varies the number of blurred image signals to be created (number of frequency bands) according to the site determined by the site determination unit 139.

  Hereinafter, with reference to FIG. 7, the processing procedure of the image processing unit of the present embodiment will be described.

  After the start of imaging, the image processing unit 130 inputs X-ray image data from the X-ray detector 110 (S401). The table creation unit 137 creates a SAT using the X-ray image data and stores it in the storage unit 133 (S402). On the other hand, when a part code is added as supplementary information to the X-ray image data, part determination unit 139 reads the part code. Alternatively, when a part code is input via the operation unit 170 during imaging, the information is received from the control unit 120.

  The mask creation unit 135 changes the number of frequency bands to be divided according to the part determined by the part determination unit 139 (S403). Specifically, for example, a basic frequency band is set by default, and usually a blurred image signal of the basic frequency band and a blurred image signal used for dynamic range compression are created (S404). In the case of a part code indicating a part including a fine structure, a high frequency band is finely designated in the frequency band to be divided (S405). In addition, for a portion where a rough structural change only needs to be recognized, the number of frequency bands of the blurred image signal used for frequency enhancement processing is reduced (S406).

  The mask creation unit 135 creates a blurred image signal in the set frequency band in accordance with Expression (3). Thereafter, the frequency enhancement processing unit 133 creates and outputs an output image signal according to the equation (4) using the blurred image signal created by the mask creation unit 135 (S407), and displays the image (S408). ) Is the same as in the first embodiment.

  In the above description, the case where the part determination unit 139 determines the part code and changes the content of the frequency emphasis process has been described. However, the operator can select a desired one via the operation unit 170 according to the structure of the part to be visually recognized. It is also possible to specify the frequency band in detail. In that case, the part determination unit 139 receives the designation from the operation unit 170 and changes the processing content of the mask creation unit 135 accordingly.

  In general, the image quality required for an X-ray image or a fluoroscopic image differs depending on the part to be examined, but according to the present embodiment, the degree of emphasis can be changed according to the part, so that an image with the required image quality can be displayed.

<Third embodiment>
The image processing unit of the present embodiment is characterized in that the real-time property from shooting to image display and the priority between the frame rate and the image quality of the displayed image can be selected for a fluoroscopic image. That is, the image processing unit of the present embodiment adjusts the number of frequency bands according to the frame rate of the fluoroscopic image and / or the number of pixels of the fluoroscopic image.

  Although this embodiment can also be applied to both a photographed image and a fluoroscopic image, the operation of the image processing unit of the present embodiment will be described below with reference to FIG. The configuration of the image processing unit of the present embodiment is substantially the same as the functional block diagram shown in FIG. 2 or 6 except that it has a processing time calculation / determination function. This will be described using the elements shown in the figure.

  First, when imaging is started and X-ray image data is input (S501), the image processing unit 130 executes steps S302 to S305 shown in FIG. 3, and performs frequency enhancement processing and dynamic range compression processing by SAT addition processing ( S502). The frequency emphasis process at this time may be a process using a reference frequency band and a blurred image signal of the number of bands set as defaults, or may be set according to a part as performed in the second embodiment. Frequency enhancement processing may be used.

  The image processing unit 130 counts the time (processing time) required to process one image (processing time calculation function), and determines whether or not it is within an allowable range (determination function) (S503). The processing time of one image is mainly the time required for SAT creation and blur image creation using the SAT. The allowable range is the frame interval when the frame rate of the fluoroscopic image is set.

  If the processing time is within the allowable range, the fluoroscopy is continued with the frequency enhancement processing content and the frame rate as they are, and the fluoroscopic image is displayed as a moving image on the display unit 160 (S507).

  On the other hand, if the processing time exceeds the allowable range, the processing is performed according to the priority information between the frame rate and the image quality set via the operation unit 170 (S504). The priority setting is set by the operator by selecting either “image quality” or “real time” on the screen 900 of the display unit 160 for setting the imaging conditions and the like as shown in FIG. Can do.

  Here, when “image quality priority” is set, the control unit 120 controls the X-ray source (high voltage generation unit 108) to reduce the X-ray irradiation rate and reduce the number of captured images per hour. (S505). That is, the processing content in the image processing unit 130 is not changed, and the perspective image is displayed on the display unit 160 at a reduced frame rate (S507). If “image quality priority” is not set, or if “real-time priority” is set, the frequency band in the frequency enhancement process is decreased (S506). Thereby, the frame rate of the fluoroscopic image displayed on the display unit 160 is maintained (S507).

  Note that the priority is not an alternative between real time and image quality, but it is also possible to provide a stage for each and adjust the X-ray irradiation rate or the number of frequency bands according to each stage.

  For example, in the case of image quality priority I, the X-ray irradiation rate is reduced without changing the number of frequency bands, and in the case of image quality priority II with higher image quality, the frequency band is increased. Reduce the irradiation rate together. In the case of real-time priority I, the frequency band is reduced without changing the frame rate. In the case of real-time priority II having a higher priority than that, both the frame rate is increased and the frequency band is reduced. .

  According to this embodiment, in X-ray fluoroscopy that requires real-time display compared to a captured image, for example, when a catheter is being operated during an examination, the display of the fluoroscopic image is delayed, and the operator's intention If there is a possibility of passing through the current stop position and destroying structures inside the body, reducing the number of bands avoids time delay due to image processing delay, maintains the rate, and displays It is possible to ensure real-time performance.

  When priority is given to image quality, the number of bands may be maintained to reduce the perspective rate. The priority setting by the operator may be performed before the start of imaging or during imaging.

<Modification 1>
In the third embodiment, the processing time of an actually captured image is calculated and it is determined whether or not it is within an allowable range. However, the processing time can be calculated by simulation if the image size of the actually captured image is known. It is. In that case, imaging conditions or image processing conditions can be set and imaging can be started in consideration of the priority between the image and the real-time property with respect to the reference setting such as the frame rate.

<Modification 2>
In the third embodiment, on the premise that the frame rate and frequency enhancement processing conditions are set as the initial conditions, the imaging conditions or the image processing conditions are changed in consideration of the priority of the image quality or real-time characteristics by the operator. However, in this modification, the operator sets an arbitrary frame rate on the screen 900 of FIG. 9, for example, and determines the number of frequency bands from the processing time of one image determined by the set frame rate.

  Since the frame rate and the processing time have an inverse relationship, when the frame rate is determined, the processing time allowed under the frame rate condition is calculated. On the other hand, the processing time is approximately [SAT creation time + blur image signal creation time], and [blur image signal creation time] is proportional to the number of frequency bands (the number of blur image signals to be created). Therefore, if [SAT creation time] and [one blur image signal creation time] are known, the number of frequency bands can be calculated.

  According to this modified example, when the operator sets an arbitrary frame rate, it is possible to acquire an image with the highest image quality within the range of the frame rate.

  As described above, the embodiment in which the present invention is applied to the X-ray imaging apparatus has been described. However, the present invention is characterized in that the image processing unit creates a SAT for creating a blurred image signal and performs a frequency enhancement process using the SAT. Therefore, the present invention can be applied to medical imaging apparatuses and medical image processing apparatuses other than X-ray imaging apparatuses. Accordingly, the configuration of the present invention is not limited to the embodiments shown in the respective embodiments and drawings, and those in which some elements are omitted and elements not shown in the drawings are also included in the present invention. . The means for realizing the image processing function can be variously changed in software or hardware. Furthermore, each embodiment and modification which were mentioned above can be combined suitably.

DESCRIPTION OF SYMBOLS 102 ... X-ray source, 104 ... Aperture device, 106 ... Top plate, 108 ... High voltage generation part, 110 ... X-ray detector, 120 ... Control part, 121 ... Shooting control unit, 123 ... display control unit, 130 ... image processing unit, 131 ... storage unit, 133 ... frequency enhancement processing unit, 134 ... dynamic range processing unit, 135 ... Mask creation unit, 137 ... table creation unit, 160 ... display unit, 170 ... operation unit (input unit), 180 ... image storage unit, 200 ... range summation table (SAT).

Claims (8)

An X-ray source that irradiates X-rays, an X-ray detector that is arranged opposite to the X-ray source and detects X-rays that have passed through the inspection object, and an X-ray signal output from the X detector is processed And an image processing unit for creating an X-ray image,
The image processing unit includes a frequency enhancement processing unit that performs a process of enhancing a specific frequency component on the X-ray signal,
The frequency enhancement processing unit includes a table creation unit that creates a range sum table using the X-ray signal, and a mask creation unit that creates a blurred image signal of one or more frequencies using the range sum table. , And performing frequency enhancement using the X-ray signal and the blurred image signal. The X-ray imaging apparatus according to claim 1,
The frequency enhancement processing unit further includes a dynamic range compression processing unit that compresses the dynamic range of the X-ray signal using the blurred image signal, and performs dynamic range compression simultaneously with frequency enhancement. Imaging device. The X-ray imaging apparatus according to claim 1 or 2,
The X-ray imaging apparatus, wherein the mask creating unit creates a blurred image signal in a frequency band corresponding to the part based on a relationship between a part to be inspected and an emphasis frequency. In the X-ray imaging device according to any one of claims 1 to 3,
It further includes an input unit that receives an input of a region to be examined or an emphasis frequency,
The X-ray imaging apparatus, wherein the mask creating unit creates the blurred image signal in accordance with the inspection target region or the emphasis frequency received by the input unit. In the X-ray imaging device according to any one of claims 1 to 4,
A control unit that controls operations of the X-ray source, the X-ray detector, and the image processing unit, and acquires a fluoroscopic image at a predetermined frame rate;
The X-ray imaging apparatus, wherein the mask creating unit adjusts the number of blurred image signals to be created according to a frame rate of the fluoroscopic image and / or a number of pixels of the fluoroscopic image. The X-ray imaging apparatus according to claim 5,
An input unit that receives an input of a frame rate of the fluoroscopic image;
The X-ray imaging apparatus, wherein the control unit controls imaging at a frame rate received by the input unit. A medical image processing apparatus for processing a medical image acquired by a medical imaging apparatus,
A frequency enhancement processing unit that performs frequency enhancement processing on the original image signal of the medical image;
The frequency enhancement processing unit includes a table creation unit that creates a range sum table using the original image signal, and a mask creation unit that creates a blur image signal of one or more frequencies using the range sum table. , And performing frequency enhancement using the original image signal and the blurred image signal. The medical image processing apparatus according to claim 7,
The medical image processing apparatus, wherein the medical image is a still image or a fluoroscopic image captured by an X-ray imaging apparatus.

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