WO2009093693A1

WO2009093693A1 - Image generation device, image generation method, and program

Info

Publication number: WO2009093693A1
Application number: PCT/JP2009/051084
Authority: WO
Inventors: Osamu Toyama; Koichi Fujiwara; Takuya Kawano
Original assignee: Konica Minolta Holdings, Inc.
Priority date: 2008-01-25
Filing date: 2009-01-23
Publication date: 2009-07-30
Also published as: JPWO2009093693A1; JP5029702B2

Abstract

Provided are an image generation device, an image generation method and a program by which only a substantial difference between two moving images captured by photographing the identical object at different times can be extracted from the two moving images. The image generation device comprises a phase detection means which detects the phase of the periodical movement of an object relative to each of the two moving images obtained by photographing the identical object at the different times and an interpolated image creation means which captures two phase-matched moving images in which the phases of still images constituting the two moving images are matched to each other by interpolating at least either of the two moving images in time-series.

Description

Image generating apparatus, image generating method, and program

The present invention relates to an image generation technique that can accurately extract a difference between two moving images having partial differences.

In recent years, it has become indispensable to take a chest image of a human body in a normal health checkup in order to help discover many diseases including lung diseases. By observing respiratory motion images obtained by chest imaging in time series, it is possible to clarify the influence of the disease.

In addition, in order to detect a diseased part that has progressed in an affected area, a difference image between time-series radiation images is created, and a diagnosis support is proposed by observing the created difference image simultaneously with the time-series radiation image. Yes.

However, when simply comparing the respiratory motion image captured in the past with the currently captured respiratory motion image, it is difficult to compare if there is a phase shift, and if the time difference between them is taken, the respiratory phase will match. Therefore, there is a possibility that artifacts, which are image noises generated by image processing, occur in the time difference information.

Therefore, in the conventional technique, when a difference in a respiratory moving image captured during a plurality of respiratory cycles separated over time is obtained and a change over time is extracted, a respiratory phase that approximates the respiratory phase of a reference image at a certain point in time is calculated. Artifacts are reduced by determining a reference image at another point in time and performing difference processing between the two (for example, Patent Document 1).

JP 2005-151099 A

However, in the prior art, a comparison is made between a reference image at a certain time point and a reference image at another time point having a respiration phase that approximates the respiration phase of the reference image. Since it is not always done, an artifact may appear in the difference image.

The present invention has been made in view of the above problems, and can generate an image that can extract only a substantial difference between two moving images obtained by photographing the same object at different times. Is to provide technology.

In order to solve the above-described problem, the image generation apparatus according to the first aspect is obtained by photographing the same object at different times, each of which includes two time-series sets of still images. For each moving image, phase detection means for detecting the phase of the periodic movement of the object, and at least one of the two moving images is interpolated in time series, so that the still images constituting each of the moving images Interpolated image creating means for obtaining two phase-matched moving images whose phases are matched with each other.

The image generation device according to the second aspect is the image generation device according to the first aspect, wherein the two moving images have a range including a specific part of a human or animal body as the object. The phase is determined from the temporal variation state of the specific image region corresponding to the specific part.

Further, the image generation device according to the third aspect is the image generation device according to the second aspect, and the phase is obtained from a temporal variation state of a geometric size of the specific image region.

The image generation device according to the fourth aspect is the image generation device according to the second or third aspect, wherein the specific image region is a lung field region that moves by breathing with a respiratory cycle as a cycle, or A heart region that is moved by a heartbeat with a heartbeat cycle as a period.

The image generation device according to the fifth aspect is the image generation device according to any one of the first to fourth aspects, and the interpolation image creation means includes each of the two moving images. When the number of still images is different, the moving image with the smaller number of still images is used as the reference moving image, and the moving image with the larger number of still images is used as the reference moving image. By generating an interpolated still image corresponding to each of the reference phases by interpolation of a still image included in the reference moving image using the phase of each of the still images as a reference phase, Generate an interpolated video.

The image generation device according to the sixth aspect is the image generation device according to the fifth aspect, in which the generated interpolated moving image and the reference moving image have still corresponding phases. Further, a temporal difference image creating means for generating a time-series set of difference still images by taking the difference is provided.

An image generation device according to a seventh aspect is the image generation device according to the fifth aspect, wherein the first moving image is obtained by taking a difference between two still images that are temporally adjacent to each other in the reference moving image. A phase array corresponding to the set of the first differential still images is obtained by taking a difference between the interpolation still images included in the interpolation moving image and a means for generating a time-series set of differential still images. Means for generating a time-series set of second differential still images, and taking a difference for each still image for the set of the first and second differential still images while corresponding to each other's phase, There is further provided inter-frame temporal difference image creation means for generating a time-series set of third difference still images and thereby obtaining a difference moving image.

The program according to the eighth aspect is a program that, when executed by a computer, causes the computer to function as the image generation apparatus according to any one of the first to seventh aspects.

The image generation method according to the ninth aspect is an image generation method, which is obtained by photographing the same object at different times, each of which is constituted by a time-series set of still images. For each of the moving images, for each of the two moving images, a phase detection step for detecting the phase of the periodic movement of the object, and at least one of the two moving images is interpolated in time series The interpolated image creation step of obtaining two phase-matched moving images in which the phases of the still images constituting each of them are matched with each other.

According to the image generation device according to the first aspect, the image generation device interpolates at least one of the two moving images in a time series, thereby matching the phases of the still images constituting each of the two. Since two phase-matching moving images can be obtained, phase shifts can be eliminated, and two moving images obtained by photographing the same object at different times can be substantively between them based on changes over time. It is possible to extract only the differences.

According to the image generation device according to the second aspect, the phases of the two moving images are determined from the temporal variation state of the specific image region corresponding to the specific part of the human or animal body. Only substantial differences based on changes over time in specific parts of the body can be extracted.

According to the image generating apparatus according to the third aspect, the phase is obtained from the temporal variation state of the geometric size of the specific image area. Therefore, the phase is determined by measuring the geometric size of the specific image area. It can be easily obtained.

According to the image generating apparatus according to the fourth aspect, the specific image region is a lung field region that moves by breathing with a breathing cycle as a cycle or a heart region that moves by heartbeat with a heartbeat cycle as a cycle. Only substantial differences based on changes over time in the region or heart region can be extracted.

According to the image generating apparatus of the fifth aspect, the interpolation image creating means is included in the reference moving image with the smaller number of still images when the number of still images constituting the two moving images is different. Since the phase of each still image is used as a reference phase, the number of still images is large, and an interpolation still image corresponding to each of the reference phases is generated by interpolation of still images included in a reference moving image with a short shooting time interval. Compared to the reverse case, an accurate interpolated moving image with fewer interpolation errors can be created.

According to the image generating apparatus of the sixth aspect, the interphase moving image generated by the temporal difference image generating means and the reference moving image take a difference between still images having phases corresponding to each other, so that the phases match. Artifacts generated by taking the difference between still images that have not been taken can be reduced, and an image can be displayed, and a portion that changes over time (for example, a diseased portion of a diseased portion that has progressed) can be prominently detected.

According to the image generation device according to the seventh aspect, the difference between two still images that are temporally adjacent in the reference moving image and the two differences between the interpolated still images included in the interpolated moving image having the corresponding phase arrangement And then taking the difference between them to create an inter-frame temporal difference image, so compare the time-varying portion in the reference video with the time-varying portion in the reference video When performing, the artifacts caused by the phase shift can be reduced.

According to the program according to the eighth aspect, it is possible to obtain the same effect as that of the image generation apparatus according to the first to seventh aspects.

According to the image generation method according to the ninth aspect, the same effect as that of the image generation apparatus according to the first aspect can be obtained.

1 is a block diagram showing a configuration common to each embodiment applied to an image generation device 1. FIG. It is a graph which shows the relationship between a respiratory cycle and lung field size. It is a figure which shows the function structure implement | achieved by the image generation apparatus 1 which is 1st Embodiment. It is a figure which shows the example of the time series still image which comprises each of a reference moving image and a reference | standard moving image. It is a figure which shows an image coordinate system. It is a graph which shows the relationship between phase (theta) and lung field length. It is a figure which shows the principle of the warping which can be utilized in preparation of an interpolation still image. It is the figure which showed the corresponding reference moving image. It is a figure which shows the specific example in the case of producing the produced interpolation image. It is a figure which shows the function structure implement | achieved by the image generation apparatus 50 which is 2nd Embodiment. It is a figure which shows the specific example of a time difference image. It is a figure which shows the function structure implement | achieved by the image generation apparatus 100 which is 3rd Embodiment. It is a figure which shows the specific example of an inter-frame difference image and an inter-frame time difference image.

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

<Overall configuration of image acquisition system>
FIG. 1 is a block diagram showing a configuration common to each embodiment in which the present invention is applied to an image generation apparatus 1 capable of generating a diagnostic image of a specific part (for example, a lung) of a patient in cooperation with a medical imaging apparatus. It is.

As shown in FIG. 1, the image generating apparatus 1 has a general computer configuration in which a CPU 21, a RAM 22, and a ROM 23 are connected to a bus line 10. Connected to the bus line 10 are a display unit 3 for displaying images and the like, an operation unit 4 including a keyboard and a mouse for receiving input from a user, an input unit 5 for inputting data, and a fixed disk 24 for storing various data. Has been.

The CPU 21 operates based on the program PG transferred from the fixed disk 24 to the RAM 22, determines the operation of the entire image generation apparatus 1, gives a command to the entire image generation apparatus 1, and further displays on the display unit 3 described later. Give instructions. The CPU 21 creates an interpolation image, a temporal difference image, and the like as means for realizing each function described later.

The display unit 3 is composed of a liquid crystal display, for example, and visually outputs moving image data generated by the CPU 21.

The operation unit 4 includes a keyboard, a touch panel, a mouse, and the like, and transmits various command signals to the CPU 21 in accordance with various user operations.

The input unit 5 inputs image data. The input unit 5 may receive image data on-line by connecting a medical image photographing device, and further input data by reading data from a portable storage medium such as a DVD or reading by a scanner. Is possible. Alternatively, an image obtained by photographing a person who is a subject of photographing (photographing subject) is stored in a file server or the like connected via a network, and the image of the subject subject of photographing is selected from a plurality of stored image data. Data may be retrieved and read. The input image data is stored in a storage device such as the fixed disk 24 or the RAM 22.

The medical imaging apparatus is constituted by, for example, an X-ray imaging apparatus or the like, and images a predetermined part included in the imaging subject person's internal body. The X-ray imaging apparatus performs imaging by exposing a subject to be imaged from an X-ray generation source. The exposed X-rays pass through the chest of the subject, the intensity distribution is detected, the detected X-rays are converted into analog electrical signals, and the analog electrical signals are converted into digital signals by A / D conversion. Then, it is stored on the storage device of the X-ray imaging apparatus as a moving image consisting of a plurality of still images in time series. The image stored in the storage device is transferred to the input unit 5 as necessary.

In the following first to third embodiments, an X-ray image is used as a radiation image.

<First Embodiment>
In the first embodiment, for the same patient, X-ray moving images obtained by imaging lung field regions of one respiratory cycle or more at different times (for example, moving images taken in the previous month and the latest images) A moving image photographed in the inspection) is input to the image generating apparatus 1. The image generation apparatus 1 creates an interpolated moving image for at least one of the two moving images that have been input and the respiratory phase information derived therefrom.

FIG. 2 is a graph showing the relationship between the respiratory cycle and lung size. Strictly speaking, the size of the lung field corresponds to the “volume” of the lung field, but in two-dimensional X-ray imaging, it is expressed by the “(projection) area” of the photographed lung field. The horizontal axis of the graph represents the respiratory cycle, the vertical axis of the graph represents the lung field size, and shows how the lung field size changes in a plurality of respiratory cycles.

Here, the breathing cycle (cycle) is a breathing exercise that includes a single exhalation mode and an inhalation mode, and the inspiratory mode is a mode that inhales the breath, and the lung region in the thorax accordingly Becomes larger and the diaphragm is pushed down. The exhalation mode is a mode for exhaling, and as the lung area increases, the diaphragm increases. The phase represents a relative position in one cycle in a periodic motion by exhalation and inspiration.

In terms of a general expression, when the time (period) of one respiratory cycle is T and the elapsed time is t, the phase θ is
θ = F (t: T) Formula (A)
Can be expressed as

As an example, the phase θ is a (periodic) linear function of time t:
θ = t / T−int (t / T) (formula (B))
Can be expressed as The symbol int indicates the integer part of the argument.

Further, if it is defined that the time t is reset to 0 at the end of each cycle, θ = t ... Formula (C)
It can also be determined by

The phase θ in the case of the formula (B) has a value in the range of 0 to 1, and the phase θ in the case of the formula (C) has a value in the range of 0 to T.

Furthermore, when the lung field size is expressed by the parameter P and the maximum value is expressed by P0, θ = G (P / P0) using the periodic function G having the period T. Equation (D)
Can also determine the phase θ. The periodic function G is, for example, an arc sine function having a period T. This is a definition using the fact that the parameter P periodically changes depending on the respiratory cycle, but the parameter P is a periodic function (period T) of time t.
P = P (t: T) ... Formula (E)
In this case as well, a function of time t can be used as a surrogate index of the phase θ.

When the motion periods T = T1 and T2 of the two moving images to be compared are the same, the normalization factor T can be omitted and the time t can be used as a proxy index for the phase θ. In the example described later, the phase θ is expressed in units of time t on the assumption that the periods T1 and T2 are the same. When the periods T1 and T2 are different, time variables t1 and t2 normalized by the periods T1 and T2, respectively:
t1 = t / T1,
t2 = t / T2,
Is a proxy index for the phases θ1 and θ2 of the two moving images, “the same phase” means that the phase index t1 in the first moving image and the phase index t2 in the second moving image are Will have the same value. Thus, when the time of one respiratory cycle of two moving images is different, the time axis is normalized and adjusted.

Also, for the period, for example, the maximum value of each lung field size is obtained, and the time interval from the maximum value to the maximum value is defined as one period.

FIG. 3 is a diagram illustrating a functional configuration realized by the image generation apparatus 1 according to the first embodiment.

The image acquisition unit 211 includes a standard moving image acquisition unit 212 and a reference moving image acquisition unit 213, and acquires a moving image input from the input unit 5 and stored in the storage unit 219 such as the fixed disk 24 or the RAM 22. To do.

The reference moving image acquisition unit 212 acquires the reference moving image, and then outputs the reference moving image to the phase detection unit 214. Further, the reference moving image acquisition unit 213 acquires the reference moving image, and then outputs the reference moving image to the phase detection unit 214 and the interpolation image generation unit 215.

Here, the standard moving image and the reference moving image are different from the reference moving image at two different time points (for example, a moving image taken in the examination one month ago and a moving picture taken in the most recent examination). Of the X-ray images taken in, the one with the smaller number of images taken in one breathing cycle is the reference moving image, and the one with the larger number of images taken in one breathing cycle is taken as the reference moving image. By interpolating a reference moving image having a large number of images as an object of interpolation, an interpolation error is reduced, and an accurate interpolating moving image can be created. However, if the number of images taken at two different time points is the same, the moving image at either time point may be defined as the reference moving image. The reference moving image is input to the reference moving image acquisition unit 212, and the reference moving image is input to the reference moving image acquisition unit 213.

FIG. 4 is a diagram illustrating an example of a time-series still image constituting each of the reference moving image and the standard moving image. The horizontal axis indicates the passage of time, and the value obtained by dividing the elapsed time t (horizontal axis) by the period T as described above is an index of the phase.

Referring to FIG. 3, the phase detection unit 214 detects the upper end of the lung field region in each of the reference moving image and the reference moving image calculated from the image coordinate system of the input image (the coordinate system fixed to the imaging screen). The size of the lung field region (the left and right contours of the chest in FIG. 4) is represented by the length from the bottom to the bottom, and the phase of each still image is detected from the time T of one respiratory cycle, and this phase is interpolated. The data is output to the image creation unit 215. The phase may be detected using either the left or right lung field, and the phase may be specified by the average value of both individual phases.

FIG. 5 is a diagram showing an image coordinate system. In FIG. 5, the image coordinate system of the input image has the upper left corner as the origin (0, 0), and the horizontal direction (X direction) and the lower direction (Y direction) are respectively positive directions (+). To do.

In the present embodiment, as described above, based on the change in the time of one respiratory cycle of the reference moving image and the reference moving image and the length from the upper end to the lower end of the lung field region (hereinafter referred to as “lung field length”), The phase of the moving image and the reference moving image is determined.

FIG. 6 is a graph showing the relationship between the phase θ (time t normalized by the period T) and the lung field length, and how the lung field length changes as the phase (time) changes. Is shown. The horizontal axis of the graph represents one respiratory cycle, and the vertical axis of the graph represents a lung field size expressed in lung field length. Moreover, the double-directional arrow (solid line) shown beside the lung image shown in FIG. 6 shows the lung field length. Here, the numerical value on the horizontal axis represents the time t that has elapsed since the start of the respiratory cycle, and the real time unit is 1/30 (second). From the waveform data shown in FIG. 6, the phase at each time point can be defined. However, when the time of one breathing cycle of the standard moving image and the reference moving image is different, the time axis is first normalized and adjusted.

The method for determining the top of the lung field (lung top) and the bottom of the lung field (lung bottom) is "Image" feature analysis and computer-aided diagnosis: Accurate determination of ribcage boundary in chest radiographs ", Xin-Wei Xu and Kunio Doi, Medical Physics, Volume 22 (5), May 1995, pp.617-626. Etc.) can be used.

In addition, it is possible to extract the contour of the lung field in order to determine the upper end and lower end of the lung field region, for example, to set the minimum value of the Y coordinate value of the obtained contour as the upper end and the maximum value as the lower end. is there.

The contour extraction of the lung field can be performed using a method disclosed in, for example, Japanese Patent Laid-Open No. 63-240832.

Also, it is possible to detect the phase of the reference moving image based on the area of the lung field region. The lung field area can be obtained by extracting the contour of the lung field and defining the number of pixels in the region surrounded by the contour as the lung field region. In this way, the phase θ can be easily obtained by measuring the geometric size such as the length and area of the specific image region.

That is, the period T is determined from the difference between two times at which the lung field size becomes maximum, and the phase θ can be determined using the period T and the time t. As described above, there are various methods for defining the phase. In any case, within one respiratory cycle T, the waveform of the lung field size is a monovalent function with respect to the phase θ. One state is uniquely identified.

With reference to FIG. 3, the interpolation image creation unit 215 uses the phase of each still image included in the reference moving image as a reference phase by a technique such as warping, for example, and generates a still image corresponding to the phase from the reference moving image. An interpolated still image is generated. The phase of the still images constituting the standard moving image and the reference moving image are matched with each other by arranging the generated series of interpolated still images in time series to form a moving image (interpolated moving image). Specifically, it becomes possible to obtain two phase-matching moving images having the same phase. The created phase matching moving image is stored in the storage unit 219 such as the fixed disk 24 or the RAM 22.

Note that a moving image in which the still image density of the reference moving image alone is improved is obtained by merging the created series of interpolated still images and the original still images constituting the reference moving image in time order. It is also possible to save it. In this case, the phases of all the still images of the two phase matching moving images (the reference moving image and the merged reference moving image) are not matched. If the phase of an arbitrary still image included in one of the phase-matching moving images corresponding to the reference moving image is specified, the still image corresponding to that phase exists in the other phase-matching moving image, but the opposite is true. Is not necessarily true (subset relationship). Therefore, in comparison with the state before the interpolation that there is no still image having a phase matching between the two moving images (between the standard moving image and the reference moving image), the two phase-matching moving images also in this case It can be said that it has phase consistency.

FIG. 7 is a diagram illustrating the principle of warping that can be used in the creation of the above-described interpolated still image, taking a square deformation as an example. In warping, an original image representing a base shape and a final image representing a final shape are prepared, and first, each point of the base shape of the original image and the final shape of the final image are associated with each other. . For example, the base shape point Astart is associated with the final shape point Aend. When the feature points (coordinate values) of the associated points Astart and Aend are (Axstart, Aystart) and (Axend, Ayend), the feature points corresponding to the vertices Ai of the intermediate image that is the image being deformed ( Let s be the deformation ratio of Axi, Ayi). This can be represented by equation (1).

S is determined by using Equation (2) with θstart and θend as the phases of the original image and the final image sandwiching θi, respectively, where θi is the phase of the intermediate image that is an image in the middle of deformation.

Therefore, warping can be performed by changing (increasing) s with time. Similar processing is performed for Bstart and Bend, Cstart and Cend, and Dstart and Dend described in the original image and the final image. FIG. 7 shows an intermediate image when s = 0.3 as an example. When creating an interpolation image, s is determined with θstart and θend being the phases of two temporally adjacent reference images for which an interpolation image is to be created, and θi being the phase of the corresponding reference image.

FIG. 8 is a diagram showing a corresponding reference moving image, in which the phase shown in FIG. 6 is associated with the image in FIG. The horizontal axis shows the passage of time. Here, 1 in the phase: 1 represents the time elapsed from the start of the respiratory cycle, and the unit is 1/30 (second). Hereinafter, the phase is similarly expressed.

FIG. 9 is a diagram showing a specific example in the case of creating the created interpolation image. FIG. 9 shows an interpolated image having the phase of the image of the reference moving image [1] in FIG. The horizontal axis shows the passage of time. As shown in FIG. 9, the interpolated image having the phase of the still image of the reference moving image [1] is created using the reference moving images (1) and (2) in FIG. in this case,
s = (4-1) / (5-1) = 0.75
As a result, an interpolated image having a phase of 4 is created and associated with the phase of the still image of the reference moving image [1].

Also, the interpolation image creation unit 215 can create an interpolation image by a technique such as morphing.

The interpolated moving image is obtained by arranging the series of interpolated images obtained in this way in time series.

According to the present embodiment, the image generation apparatus can obtain two phase-matched moving images in which the phases of the still images constituting the two moving images are matched, so that the phase shift can be eliminated at different times. Only substantial differences between them can be extracted from two moving images obtained by photographing the same object (same patient) based on the temporal change of a specific part (lung field).

In particular, a moving image with few still images is used as a standard moving image, and a moving image with many still images is used as a reference moving image, and is interpolated. The time interval is short and the interpolation accuracy is high.

Second Embodiment
In the second embodiment, the above-described temporal difference image is created from the interpolated moving image and the reference moving image. That is, a difference still image is generated by taking a difference between still images having phases corresponding to each other between the generated interpolated moving image and the reference moving image.

FIG. 10 is a diagram illustrating a functional configuration realized by the image generation apparatus 50 according to the second embodiment.

A part of the functional configuration of the second embodiment is similar to that of FIG. 3 described above, and the configuration of the present embodiment is given the same reference numerals as the corresponding configuration in FIG. Only the description is omitted, and the description of the same configuration is omitted. In particular, the configuration and operation until an interpolated moving image that matches the phase of a still image constituting the reference moving image is the same as in the first embodiment.

The temporal difference image creation unit 216 of the image generation device 50 takes the difference between the still images having the same phase with respect to the still images constituting the reference moving image and the interpolated moving image, and calculates the time series of the difference still images. A temporal difference image is created as an array or a moving image. The created temporal difference image is stored in the storage unit 219 such as the fixed disk 24 or the RAM 22.

FIG. 11 is a diagram showing a specific example of a time-difference image. The horizontal axis shows the passage of time. As shown in FIG. 11, the temporal difference image creation unit 216 obtains a difference between the lung field areas of the reference image having the same phase and the interpolated moving image for each pixel, and creates a temporal difference image.

The reason for processing only the lung field is to clarify the effects of the disease during breathing in the lung field, and the possibility of artifacts increases when processing other than the lung field is included. is there. Another reason is that no respiratory illness appears outside the lung field area, and that processing time is wasted if image data outside the lung field is processed.

According to the second embodiment, the interpolated moving image generated by the temporal difference image creating means and the reference moving image take a difference between still images having phases corresponding to each other. An image generated by taking the difference can be reduced, and an image can be displayed. For example, a lesion part of an affected part that has progressed over time can be noticeably detected.

<Third Embodiment>
Also in the third embodiment, the same configuration and operation as in the first embodiment are obtained until a series of still images constituting the interpolated moving image is obtained. In the third embodiment, an inter-frame temporal difference image is further created from the interpolated moving image and the reference moving image. That is, the difference between two still images temporally adjacent to each other in the reference moving image and the difference between two still images of the interpolated moving image corresponding to the phase of these two adjacent still images are taken, and the difference between them is further calculated. And an inter-frame temporal difference image is obtained.

FIG. 12 is a diagram illustrating a functional configuration realized by the image generation apparatus 100 according to the third embodiment.

A part of the functional configuration of the third embodiment is similar to that of FIG. 3 described above, and the configuration of this embodiment is given the same reference numerals as the corresponding configuration in FIG. Only the description is omitted, and the description of the same configuration is omitted.

The inter-frame difference image creation unit 217 calculates an inter-frame difference image obtained by taking a difference between temporally adjacent frames of the reference moving image and an inter-frame difference frame obtained by taking a difference between temporally adjacent interpolation frames of the interpolated moving image. Create a difference image.

The inter-frame time difference image creation unit 218 takes the difference between the above-mentioned inter-frame difference image and the inter-frame difference image lung field, and creates an inter-frame time difference image. That is, the difference between the lung image areas of the reference image and the interpolated moving image between two identical phases is obtained, and an inter-frame temporal difference image is created. Each created inter-frame temporal difference image is stored in the storage unit 219 such as the fixed disk 24 or the RAM 22 as a time-series series of still images or one moving image.

FIG. 13 is a diagram showing a specific example of an inter-frame difference image and an inter-frame time difference image. The horizontal axis shows the passage of time. As illustrated in FIG. 13, the inter-frame difference image is created from the difference (1) and the difference (2), and the inter-frame difference image is created from the difference (3) and the difference (4). Further, the inter-frame temporal difference image is created by calculating the difference (5) and the difference (6).

As described above, according to the third embodiment, the difference between two still images that are temporally adjacent to each other in the reference moving image, and the two differences between the interpolated still images included in the interpolated moving image having the corresponding phase arrangement, And taking the difference between them to create a time-difference image between frames, so that only two specific imaging periods (eg, lung field) that change dynamically within one respiratory cycle It is possible to detect the difference in image between the current examination), in which the phase shift is eliminated and the artifact can be deleted, for example, the position where the lesion is present is detected more prominently. be able to.

<Modification>
As mentioned above, although embodiment of this invention was described, this invention is not limited to the thing of the content demonstrated above.

For example, in the above-described embodiment, the case where the image generation apparatus has a configuration independent of the X-ray imaging apparatus has been described. However, each unit of the image generation apparatus may be realized by a computer provided in the X-ray imaging apparatus itself.

In the above embodiment, the phase of the still image included in the standard moving image is used as the standard phase, and the interpolated moving image that is a still image corresponding to the phase is generated from the reference moving image. To match the phase.

In the above embodiment, the two moving images that are the targets of the image processing and the display processing are the transmission images related to the internal structure of the human body using X-rays, but the present invention is not limited to this. For example, various moving images (that is, internal images) that capture the internal structure of the human body using MRI (Magnetic Resonance Magnetic Imaging), PET (Positron Emission Tomography), echo, or the like may be used.

In the above-described embodiment, the lung field has been described as an example. However, the present invention is not limited to this, and the heart region moving with a heartbeat can be targeted with a heartbeat cycle as a period, and various internal parts of a human or animal body can be used. The present invention can be applied to a moving image related to a structure. Furthermore, the present invention can also be applied to moving images related to various internal structures other than the human body obtained by using ultrasonic waves or various vibrations. That is, by applying the present invention to various structures other than medical uses, it is possible to easily diagnose and evaluate an internal structure in which the relative positional relationship between two or more portions changes.

It should be noted that the configurations described in the above embodiments and modifications may be replaced as appropriate as long as no contradiction arises.

These modifications can also achieve the same effects as in the above embodiment.

Claims

An image generation device,
A phase for detecting the phase of the periodic movement of the object for each of two moving images obtained by photographing the same object at different times, each of which is composed of a time-series set of still images. Detection means;
Interpolated image creating means for interpolating at least one of the two moving images in time series to obtain two phase-matched moving images in which the phases of the still images constituting each of them are matched with each other;
An image generation apparatus comprising:
The image generation apparatus according to claim 1,
The two moving images are obtained by photographing a range including a specific part of a human or animal body as the object,
The image generation apparatus according to claim 1, wherein the phase is determined from a temporal variation state of a specific image region corresponding to the specific part.
The image generation apparatus according to claim 2,
The image generation apparatus according to claim 1, wherein the phase is obtained from a temporal variation state of a geometric size of the specific image region.
The image generation apparatus according to claim 2 or 3, wherein
The image generating apparatus according to claim 1, wherein the specific image region is a lung field region that moves by breathing with a respiratory cycle as a cycle, or a heart region that moves by heartbeat with a heartbeat cycle as a cycle.
The image generation apparatus according to any one of claims 1 to 4,
The interpolation image creating means includes
When the number of still images constituting the two moving images is different, the moving image with the smaller number of still images is set as the reference moving image, and the moving image with the larger number of still images is set as the reference moving image. In this case, by using the phase of each still image included in the reference moving image as a reference phase, generating an interpolated still image corresponding to each of the reference phases by interpolation of the still image included in the reference moving image An image generating apparatus that generates an interpolated moving image as one of the phase matching moving images.
The image generation apparatus according to claim 5,
A temporal difference image creating means for generating a time-series set of difference still images by taking a difference between still images having mutually corresponding phases in the generated interpolated moving image and the reference moving image,
An image generating apparatus further comprising:
The image generation apparatus according to claim 5,
Means for generating a time-series set of first differential still images by taking a difference between two still images that are temporally adjacent in the reference moving image;
A time-series set of second differential still images having a phase array corresponding to the set of the first differential still images is generated by taking a difference of each two of the interpolated still images included in the interpolated moving image. Means,
A time-series set of third differential still images is generated by taking a difference for each still image for each set of the first and second differential still images while corresponding to each other's phase, thereby generating a difference Inter-frame temporal difference image creation means for obtaining a moving image;
An image generating apparatus further comprising:
By being executed by the computer,
A program that causes the computer to function as the image generation apparatus according to any one of claims 1 to 7.
An image generation method comprising:
For each of the two moving images obtained by photographing the same object at different times and each consisting of a time-series set of still images, the period of the object for each of the two moving images A phase detection process for detecting the phase of a typical movement;
Interpolating at least one of the two moving images in time series to obtain two phase-matching moving images in which the phases of the still images constituting each of them are mutually matched; and
An image generation method characterized by comprising: