JP2015097591A - Image processing device, and control method and program of image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing device that enables a structure inserted into a blood vessel of a subject to be clearly visible in an X-ray fluoroscopic image.SOLUTION: An image processing device includes: an image acquisition part for acquiring an X-ray image group of a subject; a generation part for generating a blood vessel route image of the subject on the basis of a first X-ray image group acquired by the image acquisition part; and an emphasis processing part for emphasizing a structure in the blood vessel of the subject in each frame of a second X-ray image group acquired by the image acquisition part on the basis of the blood vessel route image.

Description

  The present invention relates to an image processing apparatus, a control method for the image processing apparatus, and a program, and more particularly to an image processing technique that emphasizes a device such as a guide wire inserted into a subject in a fluoroscopic image obtained by an X-ray fluoroscopic apparatus.

  Due to recent advances in digital technology, it has become common to apply digital processing to images even in the medical field. Instead of conventional X-ray imaging using X-ray diagnostic film, the spread of two-dimensional X-ray sensors that output X-ray images as digital images has advanced, and edge emphasis on digital images output by two-dimensional X-ray sensors has progressed. Digital image processing such as processing is very important.

  Furthermore, an X-ray fluoroscopic apparatus that generates an X-ray image as a moving image by irradiating X-ray pulses at a predetermined cycle is used for, for example, interventional treatment (endovascular treatment) or angiographic examination. In these treatments and examinations, a device is inserted into a blood vessel such that a catheter is inserted into a subject using a guide wire.

  In the X-ray fluoroscopy by the X-ray fluoroscopy device, it is expected that the intravascular insertion device is clearly depicted. However, an intravascular insertion device is generally extremely thin, has a low X-ray absorption rate, and furthermore, X-ray fluoroscopy is performed under a low dose, so that clear visualization is difficult.

  On the other hand, in Patent Document 1 and Patent Document 2, an angiographic image is acquired before a device is inserted into a blood vessel, and this is displayed as a blood vessel route image (road map image) superimposed on an X-ray fluoroscopic image. A roadmap process is disclosed. The roadmap process allows the operator to insert the device into the blood vessel while confirming the superimposed blood vessel route, so the operator can grasp the positional relationship between the intravascular insertion device and the blood vessel route. It becomes easy.

JP 2012-81179 A Japanese Patent Laid-Open No. 4-364777

  However, according to the roadmap processing described in Patent Document 1 and Patent Document 2, although it is easy to grasp the positional relationship between the intravascular insertion device and the blood vessel path tube, the intravascular insertion device is clearly identified in the X-ray fluoroscopic image. It cannot be drawn. That is, in X-ray fluoroscopy performed under a low dose, an intravascular insertion device (structure) such as a guide wire inserted into a blood vessel is generally thin and has a low X-ray absorption rate. There is a problem that there is.

  In view of the above problems, an object of the present invention is to make a structure inserted into a blood vessel clearly visible in an X-ray fluoroscopic image.

An image processing apparatus according to the present invention that achieves the above object is as follows.
Image acquisition means for acquiring an X-ray image group of a subject;
Generating means for generating a blood vessel route image of the subject based on the first X-ray image group acquired by the image acquiring means;
Enhancement processing means for enhancing structures in the blood vessels of the subject in each frame of the second X-ray image group acquired by the image acquisition means based on the blood vessel route image;
It is characterized by providing.

  According to the present invention, a structure to be inserted into a blood vessel can be clearly seen in an X-ray fluoroscopic image.

1 is a diagram illustrating a configuration example of an X-ray imaging system according to a first embodiment. 3 is a flowchart showing a procedure of processing performed by the X-ray imaging system according to the first embodiment. 5 is a flowchart illustrating a procedure of blood vessel route image generation processing performed by the image processing apparatus according to the first embodiment. 5 is a flowchart showing a procedure of blood vessel route enhancement processing performed by the image processing apparatus according to the first embodiment. 10 is a flowchart illustrating a procedure of blood vessel route enhancement processing performed by the image processing apparatus according to the second embodiment. The figure explaining the emphasis processing operator used in the emphasis processing concerning a 2nd embodiment. The figure which shows an example of the computer system which can implement | achieve this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
In the first embodiment, a method for improving the visibility of an intravascular insertion device (structure) such as a guide wire inserted during interventional treatment will be described. In the present embodiment, based on the blood vessel route image obtained from the first X-ray image group acquired at different timings, the enhancement process of the new second X-ray image group acquired thereafter is performed. An example of selectively emphasizing the intravascular insertion device (structure) will be described.

<1. Configuration of X-ray imaging system>
First, a configuration example of an X-ray imaging system according to the present embodiment will be described with reference to FIG. The X-ray imaging system 100 includes an X-ray generation unit 101, a two-dimensional X-ray sensor 104, a preprocessing unit 105, an image storage unit 106, an operation unit 107, an image processing device 108, and a display unit 109. I have.

  The X-ray generator 101 can generate 3 to 30 X-ray pulses per second. The two-dimensional X-ray sensor 104 receives the X-ray 103 transmitted through the subject 102 and generates an X-ray image frame by frame in synchronization with the pulse. That is, the two-dimensional X-ray sensor 104 functions as an imaging unit that captures a moving image of the subject 102 irradiated with X-rays.

  The preprocessing unit 105 performs preprocessing on each frame of the moving image output from the two-dimensional X-ray sensor 104. The image storage unit 106 stores at least one frame of the preprocessed moving image or the result of image processing. The operation unit 107 receives an operation instruction input from the user.

  The image processing apparatus 108 acquires a captured X-ray image and performs image processing on the X-ray image. The image processing apparatus 108 includes a vascular route image generation unit 110 and a vascular route enhancement processing unit 111. The blood vessel route image generation unit 110 generates a blood vessel route image from at least one frame of the moving image output from the preprocessing unit 105. The blood vessel route enhancement processing unit 111 performs enhancement processing based on the blood vessel route image on the moving image output from the preprocessing unit 105.

  Here, the image processing apparatus 108 exemplifies a configuration including a blood vessel route image generation unit 110 and a blood vessel route enhancement processing unit 111, but an image acquisition unit (not illustrated) that acquires an image from the two-dimensional X-ray sensor 104, Other processing units such as the preprocessing unit 105 and the image storage unit 106 may be included. The display unit 109 displays an X-ray image. These processing units are assumed to be connected via the bus 112.

<2. Overview of enhancement processing to improve visibility of intravascular devices>
Next, with reference to the flowchart of FIG. 2, a procedure of processing by the X-ray imaging system 100 according to the present embodiment will be described. In step S <b> 201, the X-ray imaging system 100 starts first X-ray fluoroscopy in response to a fluoroscopic start instruction from the user via the operation unit 107 and acquires a first X-ray fluoroscopic image. In the first X-ray fluoroscopy, the X-ray generation unit 101 generates an X-ray pulse in accordance with the X-ray fluoroscopy conditions predetermined by the user, and the two-dimensional X-ray sensor 104 detects the X-ray pulse. An image is generated frame by frame. Subsequently, the preprocessing unit 105 performs predetermined preprocessing on each frame of the X-ray image in consideration of the characteristics of the two-dimensional X-ray sensor 104. Then, after the image processing apparatus 108 performs display image processing such as noise suppression and enhancement processing, the display unit 109 displays a moving image as an X-ray fluoroscopic image.

  This first fluoroscopy is performed while injecting a contrast medium before inserting a device such as a guide wire to be emphasized to collect an angiographic image and generate a blood vessel path image. Is to be done. Therefore, the user observes the X-ray fluoroscopic image displayed on the display unit 109 and continues the fluoroscopy while visually confirming the contrast state. After confirming the timing when the contrast medium has spread in the blood vessel, the user performs the X-ray through the operation unit 107. The radiographic system 100 is instructed to end fluoroscopy.

  In step S <b> 202, the X-ray imaging system 100 generates a blood vessel route image by the blood vessel route image generation unit 110 from the first X-ray fluoroscopic image obtained by the first X-ray fluoroscopy, and stores it in the image storage unit 106. . This blood vessel route image represents a blood vessel region into which a guide wire is inserted in the subsequent intervention treatment.

  The generation of the blood vessel route image by the blood vessel route image generation unit 110 may be performed in real time during the first X-ray fluoroscopy in Step S201, or during the first X-ray fluoroscopy, the first storage to the image storage unit 106 is performed. Alternatively, only the X-ray fluoroscopic image may be stored, and the first X-ray fluoroscopic image may be read from the image storage unit 106 after the first X-ray fluoroscopic image is completed. Details of the processing in step S202 will be described later with reference to FIG.

  In step S <b> 203, the X-ray imaging system 100 starts a second X-ray fluoroscope in response to a fluoroscopic start instruction from the user via the operation unit 107 and acquires a second X-ray fluoroscopic image. In the second X-ray fluoroscopy, the X-ray generation unit 101, the two-dimensional X-ray sensor 104, and the preprocessing unit 105 operate in the same manner as the first X-ray fluoroscopy, and generate X-ray images frame by frame. This second X-ray fluoroscopy is performed while inserting a device such as a guide wire for the interventional treatment and confirming the position of the device.

  In step S204, the X-ray imaging system 100 enhances each frame of the X-ray image obtained in real time by the second X-ray fluoroscopy by the blood vessel route enhancement processing unit 111, and generates a processing result. This enhancement process selectively enhances an intravascular insertion device such as a guide wire based on the blood vessel route image stored in the image storage unit 106 in step S202. Details of the processing in step S204 will be described later with reference to FIG.

  The above is the outline of the enhancement processing for improving the visibility of the intravascular insertion device. The image obtained by the enhancement process is displayed on the display unit 109 as a second X-ray fluoroscopic image after being subjected to a display process by the image processing apparatus 108 as in the first X-ray fluoroscopy. The user performs treatment or examination while observing the second X-ray fluoroscopic image.

<3. Details of Processing in Step S202>
Next, an example of a blood vessel route image generation process performed in step S202 by the blood vessel route image generation unit 110 included in the image processing apparatus 108 will be described with reference to the flowchart of FIG. Various methods can be applied to the generation of the blood vessel route image, and the blood vessel route image may be generated by a method other than the processing shown in FIG. Here, the description will be made on the assumption that the first X-ray fluoroscopy is completed and all the first X-ray fluoroscopic images are stored in the image storage unit 106.

  In step S301, the blood vessel route image generation unit 110 selects one frame of the first X-ray fluoroscopic image stored in the image storage unit 106 as a mask image. This mask image is an image before contrast is performed. For example, the first frame from which the contrast medium immediately after the start of fluoroscopy has not yet appeared may be used as a mask image. Further, a plurality of frames in which the contrast agent does not appear in the image may be synthesized by an averaging process, and may be generated and used as a single mask image with reduced noise.

  In step S302, the blood vessel route image generation unit 110 performs live image processing on at least two frames other than the frame selected as the mask image in step S301 among the first X-ray fluoroscopic images stored in the image storage unit 106. Select as a group. The live image group is preferably a frame in which a contrast agent appears in the image. For example, the image may be analyzed to detect the presence or absence of a contrast agent, and a frame in which the contrast agent appears in the image may be selected. Alternatively, a frame other than the mask image may be used as a live image group regardless of the presence or absence of a contrast agent. In the following description, it is assumed that each frame of the live image group has an angiographic region at a different position.

  In step S303, the blood vessel route image generation unit 110 generates a subtraction image group by performing an inter-image difference process on the mask image from each frame of the live image group selected in step S302. In the inter-image difference processing, the mask image is M, the t frame of the live image group is Lt, the t frame of the subtraction image group is St, and the pixel value of the coordinates (x, y) of each image is M (x, If y), Lt (x, y), and St (x, y), they can be expressed as shown in Equation (1).

  Here, it is assumed that the angiographic region in which the live image is drawn is represented by a lower pixel value than the region that is not the angiographic region. In this case, the subtraction image is an image in which the pixel value of the region where there is no movement between the live image and the mask image is zero, and the negative value is displayed in the angiographic region. If each frame of the live image group has an angiographic region at a different position, the subtraction image group also has an image having a negative value pixel that is an angiographic region at a position where each frame is different.

  In step S304, the vascular route image generation unit 110 performs a minimum value projection process on the subtraction image group generated in step S303 to generate one vascular route image. In the minimum value projection processing, the number of frames of the subtraction image group is T, the t frame of the subtraction image group is St (that is, 1 ≦ t ≦ T), the blood vessel route image is R, and the coordinates (x, y) of each image Assuming that the pixel values of St (x, y) and R (x, y) are expressed as equation (2).

  In Expression (2), Min (X | Y) represents a function that outputs the minimum value of the set of X that satisfies the condition Y. That is, the minimum value projection processing indicates that the minimum value of the pixel value set of the coordinates (x, y) of the subtraction image group is obtained and set as the value of the corresponding coordinates (x, y) of the blood vessel route image.

  As described above, the subtraction image group is an image having negative value pixels that are angiographic regions at different positions in each frame. Therefore, the minimum value projection process is a process of integrating angiographic regions having subtraction image groups at different positions into one image and generating it as a blood vessel route image. Thus, each process of the flowchart of FIG. 3 is completed.

  Although the case where the subtraction image group has an angiographic region with a negative value has been described here, if the angiographic region has a positive value, the maximum value projection process for obtaining the maximum value is used in the same manner. A blood vessel route image can be acquired.

  Although the case where there is no intervention by the user has been described as an example here, the user may interactively generate a blood vessel route image via the operation unit 107. For example, the user selects an image suitable as a mask image (for example, having no angiographic region and having a small positional deviation from the live image group) from the first fluoroscopic images stored in the image storage unit 106. May be. Similarly, the user may select an image suitable as a live image (for example, a clear angiographic region is present and the positional deviation from the mask image is small) from the first X-ray fluoroscopic image. Further, the alignment may be performed so as to reduce the positional deviation between the mask image and the live image group.

  Further, before the minimum value projection processing, noise suppression or enhancement processing degree change may be performed on the subtraction image group so that a desired blood vessel route image can be acquired. Or you may perform the noise suppression with respect to the blood vessel route image after a minimum value projection process, and the change of the degree of an emphasis process.

  In addition, here, the first X-ray fluoroscopic image is assumed to be stored in the image storage unit 106 after the first X-ray fluoroscopic process. However, the above-described processing is performed during the first X-ray fluoroscopic process. You may go in real time. In that case, a subtraction image is acquired in real time using any one of the frames before the contrast agent of the image acquired in real time during the first X-ray fluoroscopy as a mask image and the frame after acquiring the mask image as a live image. . Then, the subtraction image of the first frame is stored in the image storage unit 106 as it is as a blood vessel route image. In the second and subsequent frames, a minimum value projection process is performed between the subtraction image generated in real time and the blood vessel route image stored in the image storage unit 106, and the result is used as a new blood vessel route image as the image storage unit 106. Repeat the replacement with the blood vessel path image held by.

  In this case, since the blood vessel route image being created can be drawn on the display unit 109 in real time, the user only needs to end the first X-ray fluoroscopy after confirming that an appropriate blood vessel route image has been obtained.

  In addition, although a method for acquiring a blood vessel route image by acquiring a subtraction image group and performing minimum value projection has been described here, this process may be omitted. For example, when the angiographic region can be clearly depicted in one frame of the subtraction image, one subtraction image that does not perform the minimum value projection may be used as the blood vessel route image. For this subtraction image, the user may confirm the acquired X-ray fluoroscopic image and select an appropriate frame from the confirmed X-ray fluoroscopic image. Further, a blood vessel route image may be generated by selecting a subtraction image based on the inflow state of the contrast medium into the subject. For example, a function of analyzing a contrast medium inflow state into a subject and selecting a subtraction image in which the inflow state satisfies a predetermined condition may be provided.

  This contrast agent inflow state can be defined by, for example, extracting an angiographic region by threshold processing and using the area or pixel value of the angiographic region. As the predetermined condition, for example, a condition that a frame having the largest area of the angiographic region is acquired can be used.

<4. Details of Processing in Step S204>
Next, an example of enhancement processing for each frame of the second X-ray fluoroscopic image performed by the blood vessel route enhancement processing unit 111 included in the image processing apparatus 108 in step S204 will be described with reference to the flowchart of FIG.

  In step S401, the blood vessel route enhancement processing unit 111 reads the blood vessel route image stored in the image storage unit 106, and separates the blood vessel route region in the blood vessel route image from the background region other than the blood vessel route region. A blood vessel route region extraction process is performed.

  This processing can be realized by threshold processing, for example. The threshold processing is R for the blood vessel route image, R (x, y) for the pixel value of the coordinates (x, y), T for the predetermined threshold, B for the binary image as an output, and the coordinates (x, y). If the pixel value of B is B (x, y), it can be expressed as in equation (3).

  Here, the blood vessel route image R is created by the method described in the flowchart of FIG. 3, and it is assumed that the negative value is the blood vessel route. Accordingly, the pixel value B (x, y) of the binary image B is a blood vessel route region image that represents 1 if the coordinates (x, y) is a blood vessel route region and 0 if the coordinate is a background region. The threshold T is zero in an ideal case where there is no subject movement and noise, but since there is actually subject movement and noise, if an appropriate value is determined and used so that the influence of noise and subject movement can be reduced. Good.

  It is desirable that the blood vessel route image is one connected region of the band-like structure. For this, binarization is performed after noise reduction processing, isolated points and holes are removed by morphological operation after binarization processing, connected regions are identified by labeling processing, and regions other than the largest area are removed Various image segmentation techniques can be used.

  In step S402, the blood vessel route enhancement processing unit 111 performs selective enhancement processing on the region corresponding to the blood vessel route region represented by the binary image generated in step S401 in each frame of the second X-ray fluoroscopic image. In this process, different enhancement processing is performed on each region in each frame of the second X-ray image group corresponding to the blood vessel route region and the background region.

  As an example of enhancement processing, here, frequency enhancement processing is performed in which an image is decomposed into a plurality of band-limited images at different frequencies, adjusted differently for each band-limited image, and then synthesized to generate a single enhanced image. explain. Specifically, the second X-ray image frame is decomposed into a plurality of band-limited images at different frequencies, and each band-limited image has a different emphasis on each region of the band-limited image corresponding to the vascular route region and the background region. Based on the plurality of band-limited images subjected to the enhancement process, the structure in the blood vessel of the subject in each frame of the second X-ray image group is enhanced.

  There are various methods for decomposing an image into a plurality of band-limited images, such as Laplacian pyramid decomposition, wavelet transform, and unsharp mask. For example, in the method using an unsharp mask, the original image is Sorg, the blurred image is Sus, the band-limited image is H, the pixel values of the respective coordinates (x, y) are Sorg (x, y), and Sus (x, y ), H (x, y), it can be expressed as in equation (4).

Expression (4) is a case where one band limited image is generated from the original image. A method for generating a plurality of band component images representing different frequencies is as follows. Different frequencies are represented by level lv, and a plurality of band limited images having different frequencies from high frequency (lv = 1) to low frequency (lv = lvMax) are represented by {H _lv | lv = 1, 2,. . . , LvMax}. At this time, the band-limited image H _lv at an arbitrary level lv can be expressed as in Expression (5).

Here, {Sus _lv | lv = 0, 1, 2,. . . , LvMax} are a plurality of blurred images having different frequencies, and the blurred image Sus _{0 with} lv = 0 is equal to the original image Sorg. From Expression (5), the relationship between the original image Sorg and the band limited image H _lv can be expressed as Expression (6).

Equation (6) is obtained by adding all of the decomposed band-limited images H _lv (hereinafter, high-frequency images) and the blurred image SuS _lvMax (hereinafter, low-frequency images) having the lowest frequency to obtain the original image Sorg. Indicates that it can be reconfigured.

As described above, the frequency enhancement processing is performed using the coefficients {α _lv | lv = 1, 2,. . . , LvMax} can be expressed as in equation (7). Here, Senh is an image subjected to frequency enhancement processing.

If the enhancement coefficient α _lv on the right side is set to 1 at all levels, it can be confirmed that the right side coincides with the right side of Expression (6) and is equal to the original image Sorg. When the enhancement coefficient α _lv is larger than 1, the corresponding high-frequency image is enhanced, and when it is smaller than 1, the high-frequency image is suppressed. That is, the user can generate images with various frequency enhancements or suppressions according to preference by setting different values of the enhancement coefficient α _lv for each frequency level lv.

  When the above-described enhancement processing is used, the selective enhancement processing in step S402 can be expressed as, for example, Expression (8).

Here, β _lv is an enhancement coefficient different from the enhancement coefficient α _lv . That is, the selective emphasis process in the present embodiment performs the emphasis process on each frame of the second X-ray fluoroscopic image according to the blood vessel route region image that is a binary image. The blood vessel route region image is information that cannot be obtained from the second X-ray fluoroscopic image. In the region of B (x, y) = 1, the enhancement coefficient α _lv is set, and B (x, y) = 0 indicating the background region. By using the emphasis coefficient β _lv in this area, different emphasis processing can be performed for each area. For example, when it is desired to emphasize a device such as a guide wire in a blood vessel, the corresponding enhancement degree α _lv may be set large, thereby enabling selective enhancement of the blood vessel insertion device. Thus, the processes in the flowchart of FIG. 4 are completed.

  Although the case where there is no intervention by the user has been described here, the user may interactively generate or correct the blood vessel route region image from the blood vessel route image via the operation unit 107. In addition, when the subject movement occurs after the generation of the blood vessel route region image and before the start of the second fluoroscopy, a function of performing alignment so that the blood vessel insertion device and the blood vessel route image overlap each other may be provided.

  Further, an expansion / contraction process for expanding or contracting the blood vessel route region image, which is a binary image, with a predetermined pixel width may be performed. For example, if the blood vessel route region is widened by dilation processing, it is possible to cope with robustness even when there is a positional shift between the blood vessel route image and the second X-ray fluoroscopic image. Further, if the contraction process is performed, it is possible to control the emphasis area range by narrowing the emphasis area.

  In general, a subject may have a very narrow blood vessel region due to blood vessel stenosis. In this case, in the blood vessel route region image, the blood vessel route region that should be extracted as the originally connected structure is drawn in the middle. If this discontinuous region is very small, it may be connected by the segmentation technique applied in step S401, but in order to cope with the discontinuous region being large, the discontinuous contrasted blood vessel region is interpolated based on anatomical knowledge. A function may be provided. In addition, a portion of the contrasted blood vessel region that has been interrupted by correcting 0 pixel of the blood vessel route region image to 1 pixel according to a user operation via the operation unit 107 may be interpolated.

  Further, a road map function may be provided in which the image processing apparatus 108 displays the blood vessel route image as a road map image on the display unit 109 so as to be superimposed on the second X-ray fluoroscopic image. When displaying a blood vessel route image superimposed on a fluoroscopic image, the blood vessel insertion device and the blood vessel route are displayed after rendering the structure of the subject, and different emphasis processing is applied to the blood vessel route region and other regions. You may go. In addition, the blood vessel route image may be superimposed and displayed after subtracting the mask image from the X-ray fluoroscopic image. In this case, the structure of the subject is removed by the difference between the mask images, and an image in which only the blood vessel insertion device and the blood vessel path are depicted can be obtained, and further, region-specific enhancement processing can be performed. The display switching may be configured to be changeable by the user via the operation unit 107.

  As described above, in this embodiment, the second X-ray image group is enhanced based on the blood vessel route image obtained from the first X-ray image group acquired at different timings. And selectively highlighting the intravascular insertion device. This makes it possible to improve the visibility of the blood vessel insertion device during X-ray fluoroscopy performed by inserting a device such as a guide wire.

(Second Embodiment)
In the first embodiment, the method of selectively performing the enhancement process based on whether the target pixel in the image is a vascular route area has been described. However, the enhancement process taking into account the shape of the vascular route area and the shape of the vascular insertion device May be performed. This shape consideration utilizes the fact that the blood vessel path is usually a band-like structure and that the blood vessel insertion device is a linear structure inserted along this band-like structure.

  In the second embodiment, a method will be described in which the traveling direction of the blood vessel path is obtained for each pixel of the strip-shaped blood vessel path region and the linear structure along the traveling direction is emphasized. The configurations of the X-ray imaging system 100 and the image processing apparatus 108 according to the present embodiment are the same as those described with reference to FIG. 1 in the first embodiment. The procedure of the entire process of the X-ray imaging system 100 is the same as that in FIG. 2, and the procedure of the blood vessel route image generation process performed by the blood vessel route image generation unit 110 of the image processing apparatus 108 is also the same as that in FIG. Is omitted. In the present embodiment, the content of the blood vessel route enhancement processing performed by the blood vessel route enhancement processing unit 111 of the image processing apparatus 108 described with reference to FIG. 4 in the first embodiment is different.

  Hereinafter, with reference to the flowchart of FIG. 5, enhancement for each frame of the second X-ray fluoroscopic image performed by the blood vessel route enhancement processing unit 111 of the image processing apparatus 108 according to the second embodiment in step S <b> 204 of FIG. 2. Details of the processing will be described.

  In step S501, the blood vessel route enhancement processing unit 111 reads the blood vessel route image stored in the image storage unit 106, and the blood vessel is obtained as a binary image obtained by separating the blood vessel route region in the blood vessel route image and the other background region. A route area image is generated. Since this process is the same as step S401 in the first embodiment, a description thereof will be omitted.

  In step S502, the vascular route enhancement processing unit 111 sets an enhancement direction for each pixel in the vascular route represented by the binary image generated in step S501. This emphasis direction is set for selectively emphasizing the linear structure extending in the traveling direction of the blood vessel path. The enhancement direction may be defined by an angle, for example, with the upper left coordinate of the image as the origin, the x-axis direction as 0 degrees, and the y-axis direction as 90 degrees.

  The emphasis direction is the running direction of the blood vessel. For example, a center line having a width of 1 pixel is obtained from a blood vessel path region given as a region having a width of 2 pixels or more by thinning processing, and the direction of the thin line is used. Can do. This thinning process is not particularly described here because various algorithms have been proposed such that if the pixel value arrangement in the vicinity of the target pixel is a predetermined pattern, the thin line structure is left or the background area is removed.

The coordinates of the pixels belonging to the obtained center line are set to (x, y), and the coordinates (x ₁ , y ₁ ), (x ₂ , Assuming y ₂ ), an angle D (x, y) representing the traveling direction of the center line in the pixel (x, y) can be expressed as in Expression (9).

  For blood vessel route region pixels other than the center line, the emphasis direction can be set by giving the same angle D (x, y) to the pixels existing in the direction perpendicularly crossing the pixel (x, y) belonging to the center line. it can.

  In step S503, the blood vessel route enhancement processing unit 111 performs enhancement processing based on the enhancement direction for each pixel set in step S502. For example, a 5 × 5 size matrix shown in FIG. 6 represents an enhancement processing operator O (i, j) used for enhancement processing for a thin line structure running in the y-axis direction (90 degrees) of the image. The value E (x, y) of the coordinates (x, y) of the enhancement processing result E in which the enhancement processing operator O is applied to the pixel of the coordinates (x, y) of the image I is expressed as in Expression (10). Can do.

  This emphasis processing operator O (i, j) has a characteristic of performing strong emphasis processing on a thin line structure traveling in the y-axis direction. In order to emphasize a thin line structure traveling in a different direction, image coordinates may be rotated and applied so as to correspond to this enhancement processing operator in accordance with the enhancement direction set in step S502. For example, if the direction set for the coordinates (x, y) is θ (= D (x, y)), the direction set for the pixel according to the equation (11) corresponds to the direction of the enhancement processing operator. be able to. That is, the enhancement processing operator is applied to the corresponding pixel in each frame of the second X-ray image based on the traveling direction of the blood vessel route.

  The enhancement processing result E may be used as an output image as it is, but the enhancement processing result E can also be used as a detection result of the thin line structure. For example, the following threshold processing may be performed using a predetermined threshold T.

  At this time, B (x, y) is a binary image having a value of 1 if the coordinate (x, y) is a thin line structure and 0 if the coordinate is a background region. If the selective emphasis processing of Expression (8) is performed using this binary image, it is possible to perform appropriate emphasis processing that further restricts the emphasis target.

  As described above, in the present embodiment, in the case of X-ray fluoroscopy performed by inserting a device such as a guide wire, the shape of the angiographic region indicated by the previously acquired blood vessel path image is used to form a band-like shape. The traveling direction of the blood vessel route is obtained for each pixel in the blood vessel route region, and the linear structure along the traveling direction is emphasized. Thereby, the visibility of the blood vessel insertion device can be improved.

(Third embodiment)
Each processing unit illustrated in FIG. 1 may be configured by dedicated hardware, but the functional configuration of the hardware may be realized by software. In this case, the function of each processing unit shown in FIG. 1 can be realized by installing software in the information processing apparatus and using the arithmetic function of the information processing apparatus for an image processing method by executing the software. By executing the software, for example, a preprocessing step and an image processing step are executed for each frame of the moving image output from the two-dimensional X-ray sensor 104.

[Information processing equipment]
FIG. 7 is a block diagram illustrating the hardware configuration of the information processing apparatus and the configuration of its peripheral devices. The information processing apparatus 1000 is connected to the imaging apparatus 2000 and is configured to be capable of data communication with each other.

  The CPU 1010 can perform overall control of the information processing apparatus 1000 using programs and data stored in the RAM 1020 and the ROM 1030, and can execute arithmetic processing related to image processing that is determined in advance by executing the program. .

  The RAM 1020 has an area for temporarily storing programs and data loaded from the magneto-optical disk 1060 and the hard disk 1050. Further, the RAM 1020 includes an area for temporarily storing image data such as a mask image and a live image based on an X-ray fluoroscopic image acquired from the imaging apparatus 2000, a subtraction image, and a blood vessel route image. The RAM 1020 also includes a work area used when the CPU 1010 executes various processes. The ROM 1030 stores setting data of the information processing apparatus 1000, a boot program, and the like.

  The hard disk 1050 holds an OS (operating system) and programs and data for causing the CPU 1010 included in the computer to execute each process performed by each processing unit illustrated in FIG. These are appropriately loaded into the RAM 1020 in accordance with the control by the CPU 1010 and are processed by the CPU 1010 (computer). In addition, the image data of the mask image, the live image, and the subtraction image can be stored in the hard disk 1050.

  The magneto-optical disk 1060 is an example of an information storage medium, and a part or all of programs and data stored in the hard disk 1050 can be stored in the magneto-optical disk 1060.

  The mouse 1070 and the keyboard 1080 are operated by an operator of the information processing apparatus 1000, and various operations such as image processing adjustment, blood vessel path image correction, and alignment blood vessel path enhancement processing adjustment via the operation unit 107 are performed. An instruction can be input to the CPU 1010.

  The printer 1090 can print out the image displayed on the display unit 109 on a recording medium.

  The display device 1100 includes a CRT, a liquid crystal screen, and the like, and can display a processing result by the CPU 1010 using an image, text, or the like. For example, an image processed by each processing unit shown in FIG. 1 and finally outputted from the display unit 109 can be displayed. In this case, the display unit 109 functions as a display control unit for displaying an image on the display device 1100. The bus 1040 connects the processing units in the information processing apparatus 1000 and enables data transmission / reception between the units.

[Imaging device]
Next, the imaging apparatus 2000 will be described. The imaging apparatus 2000 is an apparatus that can capture a moving image during inflow of a contrast medium, such as an X-ray fluoroscopic apparatus, and the captured image data is transmitted to the information processing apparatus 1000. Note that a plurality of image data may be collectively transmitted to the information processing apparatus 1000, or image data may be transmitted sequentially each time an image is captured.

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (17)

Image acquisition means for acquiring an X-ray image group of a subject;
Generating means for generating a blood vessel route image of the subject based on the first X-ray image group acquired by the image acquiring means;
Enhancement processing means for enhancing structures in the blood vessels of the subject in each frame of the second X-ray image group acquired by the image acquisition means based on the blood vessel route image;
An image processing apparatus comprising:   The generating means includes a mask image that is a frame before the contrast medium flows into the subject in the first X-ray image group and a live image group that is each frame after the contrast medium flows. The image processing apparatus according to claim 1, wherein difference processing is executed to generate a subtraction image group, and the blood vessel route image is generated based on the subtraction image group.   The image processing apparatus according to claim 2, wherein the generation unit generates the blood vessel route image based on a state of contrast medium flowing into the subject.   The image processing apparatus according to claim 2, wherein the generation unit generates a subtraction image selected by a user from the subtraction image group as the blood vessel route image.   3. The image according to claim 2, wherein the generation unit generates the blood vessel route image by combining a plurality of subtraction images having different inflow states of contrast medium into the subject in the subtraction image group. Processing equipment.   The said generation means uses the frame selected by the user among said 1st X-ray image groups as said mask image and said live image group, The any one of Claim 2 thru | or 5 characterized by the above-mentioned. Image processing apparatus. An extraction means for extracting a blood vessel route region and a background region other than the blood vessel route region from the blood vessel route image;
The enhancement processing means performs different enhancement processing on each region in each frame of the second X-ray image group corresponding to the blood vessel route region and the background region. The image processing apparatus according to any one of claims 6 to 6.   The image processing apparatus according to claim 7, further comprising an expansion / contraction unit that expands or contracts the blood vessel route region extracted by the extraction unit with a predetermined pixel width.   The image processing apparatus according to claim 7, further comprising an interpolation unit that connects and interpolates discontinuous portions of the blood vessel route region.   The image processing apparatus according to claim 9, wherein the interpolation unit joins discontinuous portions of the blood vessel route region according to a user operation. Further comprising decomposition means for decomposing the frame of the second X-ray image into a plurality of band-limited images at different frequencies;
The enhancement processing means includes
For each band-limited image, different enhancement processing is performed on each region of the band-limited image corresponding to the blood vessel route region and the background region,
The structure in the blood vessel of the subject in each frame of the second X-ray image group is emphasized based on the plurality of band-limited images on which the enhancement processing has been performed. The image processing apparatus according to any one of the above. It further comprises detection means for detecting the traveling direction of the blood vessel route from the blood vessel route image,
11. The enhancement processing unit emphasizes a structure in a blood vessel of the subject in each frame of the second X-ray image group existing along the traveling direction. The image processing apparatus according to item 1. A setting unit that extracts a center line of the blood vessel route region and sets a direction of the center line for each pixel belonging to the center line based on coordinates of adjacent pixels;
The image processing apparatus according to claim 12, wherein the detection unit detects a traveling direction of the blood vessel route based on a direction of the center line. The setting means sets a direction for each pixel belonging to the blood vessel route region based on a direction set for each pixel belonging to the center line,
The image processing apparatus according to claim 13, wherein the detection unit detects a traveling direction of the blood vessel route based on a direction set for each pixel belonging to the blood vessel route region.   15. The enhancement processing unit applies an enhancement processing operator to corresponding pixels in each frame of the second X-ray image based on a traveling direction of the blood vessel route. The image processing apparatus according to claim 1. A control method for an image processing apparatus comprising an image acquisition means for acquiring an X-ray image group of a subject,
A step of generating a blood vessel route image of the subject based on the first X-ray image group acquired by the image acquisition unit;
A step of enhancing a structure in the blood vessel of the subject in each frame of the second X-ray image group acquired by the image acquisition unit based on the blood vessel route image;
A control method for an image processing apparatus, comprising:   A program for causing a computer to execute each step of the control method for the image processing apparatus according to claim 16.

Images