JP2009172190A - Image generating apparatus, program, and image generating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique to acquire images of a region with motions in which fluctuation components caused by elements other than the region are removed. <P>SOLUTION: An image generating apparatus acquires a first moving image representing a captured state in which a prescribed region constituting an inside of an animal keeps changing the shape and a second moving image representing a captured state in which the prescribed region stops changing the shape. Next, the image generating apparatus detects a phase of periodic movements of a heart of the animal when a plurality of first frame images included in the first moving image are respectively photographed and a phase of the periodic movements of the heart when a plurality of second frame images included in the second moving image are respectively photographed. Then, for the combination of the first frame image and the second frame image photographed when the phases of the periodic movements of the heart agree, the image generating apparatus generates a fluctuation component image by correcting the second region in a manner that the second representing region the prescribed captured region of the second frame image agrees with the first region representing the prescribed captured region of the first frame image and generates a difference image between the first frame image and the fluctuation component image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image generation technique.

  In the medical field, various examinations and diagnoses are performed by photographing an affected part included in a built-in structure or a skeleton using an X-ray or the like. In recent years, it has become possible to relatively easily acquire a moving image that captures the motion of an affected area using X-rays or the like by applying digital technology.

  An example of an organ that is effective for diagnosing the movement of the affected area is, for example, a lung whose shape changes greatly due to respiration. For example, the lungs tend to have a significantly reduced movement of expansion and contraction in areas with disease. For this reason, the doctor can make a diagnosis by recognizing the behavior of the lung through the moving image.

  Also, as a technique for analyzing the motion of the affected area, a difference between temporally adjacent X-ray images using a plurality of images (X-ray images) photographed using X-rays continuously in time series. A technique for acquiring (difference image) has been proposed (for example, Patent Document 1). In addition, a technique for removing a noise component from an X-ray image has been proposed (for example, Non-Patent Document 1).

JP 2004-31434 A "Evaluation of Pulmonary Function Using Breathing Chest Radiography With a Dynamic Flat Panel Detector", Rie Tanaka et al., Investigative Radiology, vol.41 (10) p735-745, October 2006.

  However, in the technique of the above-mentioned Patent Document 1, a temporal change in blood flow due to the pulsation of the heart is superimposed on a moving image capturing the lung, and the local brightness of the moving image capturing the lung is blood. Since it changes according to flow fluctuations, it becomes difficult to distinguish the features of the lung from other features.

  In the technique of Non-Patent Document 1, attention is paid to a change in a pixel value with respect to time for each pixel of interest in a moving image (chest X-ray moving image) obtained by imaging a chest using X-rays. By removing the high-frequency component in, we are trying to eliminate the fluctuation component due to blood flow.

  However, since the region of the subject (lung field region) fluctuates due to breathing, the possibility that the same lung field region appears in the same pixel in a plurality of frames of the chest X-ray moving image is low. For this reason, when the high-frequency component is simply removed from the same pixel, not only the fluctuation component due to blood flow but also other fluctuation components, that is, the fluctuation component of the lung due to respiration tend to be removed. In other words, it is difficult to visually distinguish the features of the lung from other features with high accuracy.

  Such a problem is not only in the case of acquiring an image that captures the lung using X-rays, but also under a condition in which a variation component due to an element other than the predetermined part is superimposed on the feature of the predetermined part using various techniques. Generally, when acquiring an image related to a predetermined part, it is common.

  This invention is made | formed in view of the said subject, and it aims at providing the technique which acquires the image which removed the fluctuation | variation component resulting from other than the site | part about the site | part from which the shape changes.

  In order to solve the above-mentioned problem, the invention of claim 1 is an image generation device, wherein a first acquisition is performed for acquiring a first moving image capturing a state in which a shape of a predetermined part constituting an interior of an animal changes. Means, second acquisition means for acquiring a second moving image capturing a state in which the change in the shape of the predetermined portion has stopped, and timings at which a plurality of first frame images included in the first moving image are respectively captured. Detection of detecting the phase of the periodic movement of the heart of the animal at the time and the phase of the periodic movement of the heart at the timing when each of the plurality of second frame images included in the second moving image is taken And a combination of the first frame image and the second frame image captured at a timing at which the phases of the periodic movements of the heart substantially coincide with each other according to a detection result by the detection unit. For the combination of the recognizing means and the second region, the second region capturing the predetermined portion of the second frame image matches the first region capturing the predetermined portion of the first frame image. A first generation unit that corrects a region to generate a fluctuation component image, and a second generation unit that generates a difference image between the first frame image and the fluctuation component image for the combination. .

  The invention according to claim 2 is the image generation apparatus according to claim 1, wherein the recognizing unit substantially matches the phase of the periodic movement of the heart according to the detection result by the detecting unit. Recognizing each of a plurality of combinations of the first frame image and the second frame image taken at the timing, the first generation means captures the predetermined part of the first frame image for each of the combinations The second region is corrected to generate a variation component image so that the second region obtained by capturing the predetermined part of the second frame image matches the first region, and the second generation unit includes: A difference image between the first frame image and the fluctuation component image is generated for each of the combinations.

  The invention of claim 3 is the image generation apparatus according to claim 1 or 2, wherein the predetermined part includes a lung.

  According to a fourth aspect of the present invention, there is provided the image generating apparatus according to any one of the first to third aspects, wherein the first generating unit matches the second region with the first region. As described above, the variation component image is generated by correcting only the second region.

  The invention according to claim 5 is the image generating apparatus according to any one of claims 1 to 4, wherein the detection means uses the change in electricity that controls the movement of the heart. It is characterized by detecting the phase of the periodic movement of the heart.

  The invention according to claim 6 is the image generation apparatus according to any one of claims 1 to 4, wherein the first and second moving images each capture a region including the heart. The detecting means detects the phase of the periodic movement of the heart based on a change in the shape of the heart captured by the first and second moving images.

  According to a seventh aspect of the invention, there is provided a program for causing the image generation device to function as the image generation device according to any one of the first to sixth aspects when executed by a computer included in the image generation device. is there.

  The invention according to claim 8 is an image generation method, wherein a first acquisition step of acquiring a first moving image capturing a state in which a shape of a predetermined part constituting an interior of an animal changes, and the predetermined part A second acquisition step of acquiring a second moving image capturing a state in which a change in shape is stopped, and a cycle of the animal's heart at a timing when each of the plurality of first frame images included in the first moving image is captured; A detecting step for detecting a phase of a typical motion and a phase of a periodic motion of the heart at a timing when each of a plurality of second frame images included in the second moving image is taken, and in the detecting step A recognition step for recognizing a combination of the first frame image and the second frame image captured at a timing at which the phases of the periodic movements of the heart substantially coincide with each other according to a detection result; The second region is corrected so that the second region capturing the predetermined part of the second frame image matches the first region capturing the predetermined part of the first frame image. A first generation step of generating a fluctuation component image, and a second generation step of generating a difference image between the first frame image and the fluctuation component image for the combination are provided.

  According to any of the first to eighth aspects of the invention, an image obtained by removing a fluctuation component caused by a part other than the part of the part whose shape changes is acquired.

  According to the fourth aspect of the invention, the calculation speed can be increased by reducing the calculation amount.

  According to the fifth aspect of the present invention, the phase of the periodic movement of the heart at the timing when the frame image is taken can be detected with high accuracy.

  According to the sixth aspect of the present invention, the periodic motion of the heart at the timing when the frame image is taken with a simple configuration is detected.

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

<Overall configuration of image acquisition system>
FIG. 1A is a diagram illustrating the overall configuration of the image acquisition system 1 according to the embodiment of the present invention, and FIG. 1B is a block diagram illustrating the configuration of the image acquisition system 1.

  As shown in FIG. 1A, the image acquisition system 1 mainly includes an image generation device 2, a medical image photographing device 5, and an electrocardiograph 6.

  As shown in FIG. 1B, the image generating apparatus 2 has a general computer configuration in which a CPU 21, a RAM 22, and a ROM 23 are connected to a bus line 100. In addition, the bus line 100 includes a display unit 3 for displaying an image, an operation unit 4 including a keyboard and a mouse for receiving input from a user, and a fixed disk 24 for storing various data as appropriate. It is connected through, for example.

  The bus line 100 is further connected to a medical imaging device 5 and an electrocardiograph 6 via a transmission cable interface (I / F). The image data received from the medical imaging device 5 (hereinafter also referred to as “image”) and the information received from the electrocardiograph 6 can be stored in the fixed disk 24 under the control of the CPU 21. .

  The program PG shown in FIG. 1B is stored in the fixed disk 24. Various functions as the image generation device 2 are realized by the CPU 21 operating according to the program PG.

  The medical image photographing device 5 is configured by, for example, an X-ray photographing device or the like, and photographs a predetermined part included in a person (photographing subject) that is a subject of photographing. The electrocardiograph 6 detects a change in electricity that controls the movement of the heart. For example, in response to a control signal from the CPU 21, the electrocardiograph 6 detects a change in electricity that controls the movement of the heart in parallel with the photographing operation by the medical image photographing device 5.

<Functional configuration of image generation apparatus>
FIG. 2 is a diagram illustrating a functional configuration realized by the image generation apparatus 2 by the CPU 21 operating according to the program PG, together with other configurations. 2, the imaging control unit 211, the measurement control unit 212, the image acquisition unit 213, the electrocardiogram acquisition unit 214, the phase detection unit 215, the corresponding image recognition unit 216, the fluctuation component image generation unit 217, and the difference image generation unit. 218 and the storage control unit 219 indicate functions realized by the CPU 21 and the like.

  For example, in response to an input signal from the operation unit 4, the imaging control unit 211 controls the start and end timing of moving image capturing of a predetermined part by the medical image capturing apparatus 5.

  The measurement control unit 212 controls the electrocardiograph 6 to detect a change in electricity that controls the movement of the heart of the imaging subject when the medical imaging device 5 captures a moving image of the imaging subject. Note that the measurement control unit 212 acquires a signal indicating the start and end timing of moving image shooting from the shooting control unit 211.

  The image acquisition unit 213 acquires a moving image captured by the medical image capturing device 5. The image acquisition unit 213 includes a first image acquisition unit 213a and a second image acquisition unit 213b. Each image acquired by the image acquisition unit 213 is stored in the fixed disk 24, and then an image obtained by each image processing is temporarily stored in the RAM 22 or stored in the fixed disk 24 as appropriate.

  The first image acquisition unit 213a captures a moving image (a state in which the shape of the lung changes due to breathing) in which the shape of the predetermined portion (here, the lung) that forms the inside of the subject to be photographed changes (here, the shape of the lung changes). Here, a respiratory lung moving image) is acquired. On the other hand, the second image acquisition unit 213b captures a moving image (a state in which the change in the shape of the lung is stopped by the stoppage of respiration) in which the change in the shape of the predetermined part (here, the lung) is stopped. Here, a lung moving image during breathing stop) is acquired.

  Note that the breathing lung moving image and the breathing stopped lung moving image are moving images obtained in response to the operation of the operation unit 4 by the user, and are predetermined at a predetermined frame rate (for example, 30 frames / second). It is the moving image which caught the state of the lung in a period (for example, 10 seconds).

  The electrocardiogram acquisition unit 214 acquires a so-called electrocardiogram based on the change in electricity that controls the movement of the heart detected by the electrocardiograph 6. Information relating to the electrocardiogram acquired by the electrocardiogram acquisition unit 214 is stored in the fixed disk 24. FIG. 3 is a schematic view illustrating a part of the electrocardiogram acquired by the electrocardiogram acquisition unit 214.

  Here, the respiratory lung motion image and the electrocardiogram (respiration center electrogram) related to the subject to be imaged when the respiratory lung motion image is captured are stored in association with the fixed disk 24 and the like while the breathing is stopped. The lung motion image and the electrocardiogram (respiration stop center electrogram) related to the subject to be imaged when the lung motion image during the breathing stop is photographed are associated and stored in the fixed disk 24 or the like.

  The phase detection unit 215 captures each frame image based on the electrocardiogram acquired by the electrocardiogram acquisition unit 214 and the timing at which each frame image constituting the breathing lung motion image and the breathing stop lung motion image is captured. The phase of the periodic motion (beat) of the subject's heart at the determined timing is detected. Here, each frame image is associated with the phase of the heart beat. The information associated here is appropriately stored in the RAM 22 or the fixed disk 24. The phase detection method at the time of shooting will be further described later.

  Based on the detection result by the phase detection unit 215, the corresponding image recognition unit 216 uses a plurality of frame images (respiratory breathing) constituting the respiratory motion lung motion image for the frame images (respiratory frame image) constituting the respiratory lung motion image. From the frame image during stoppage), one frame image during stoppage of breathing in which the phase of the heart beat at the captured timing is substantially the same is recognized. That is, a combination of a breathing frame image and a breathing-stop frame image in which the phases of the heart beat at the time of imaging are substantially matched is recognized.

  Here, with respect to a plurality of breathing frame images constituting the breathing lung motion image, a breathing-stop frame image in which the phases of the heart beats at the captured timing substantially coincide with each other is recognized. That is, a plurality of combinations of the breathing frame image and the breathing-stop frame image in which the phases of the heart beats at the time of imaging are substantially the same are recognized. The information recognized here is appropriately stored in the RAM 22 or the fixed disk 24. The frame image association method will be described later.

  The variation component image generation unit 217 captures a predetermined region of the breathing-stopped frame image (respiratory stop) with respect to a region (breathing lung field region) of the predetermined region (respiratory lung field region) of the breathing frame image. An image in which the breathing-stopped lung field region is corrected so as to match the middle lung field region) is generated. The image generated here is an image (variation component image) that captures fluctuation components other than the movement of the predetermined part (here, fluctuation components due to blood flow).

  Here, for each combination of the breathing frame image recognized by the corresponding image recognition unit 216 and the breathing stop frame image, the breathing of the breathing stop frame image is performed on the breathing lung field region of the breathing frame image. In order to match the stopped lung field region, the breathing stopped lung field region of the breathing stopped frame image is corrected, and a variation component image is generated.

  In addition, in order to generate each fluctuation component image, it is necessary to perform a complicated calculation described later. Therefore, considering the reduction of the calculation amount and the speeding up of the calculation, only the lung field region in which the predetermined part is stopped and the respiratory region is captured. It is preferable to generate a fluctuation component image in which is corrected. The fluctuation component image generated here is appropriately stored in the RAM 22 or the fixed disk 24. A method for generating the fluctuation component image will be described later.

  The difference image generation unit 218 is an image (difference image) indicating a difference between the breathing frame image and the fluctuation component image with respect to the combination of the breathing frame image and the fluctuation component image in which the phases of the heart beats at the time of imaging are substantially the same. ) Is generated. Here, a difference image is generated for each combination of the breathing frame image recognized by the corresponding image recognition unit 216 and the breathing stop frame image. That is, a moving image (difference moving image) that can reproduce the difference image in a moving image manner is generated.

  The storage control unit 219 controls processing for storing the images (difference images and difference moving images) generated by the difference image generation unit 218 in the fixed disk 24. The difference image and the difference moving image stored in the fixed disk 24 are appropriately and visually output on the display unit 3 based on the input from the operation unit 4.

<Phase detection method during shooting>
FIG. 3 is a diagram exemplifying an electrocardiogram showing a change in electricity that controls the movement of the heart acquired at the time of capturing a lung motion image while breathing is stopped. In FIG. 3, the horizontal axis indicates time, and the vertical axis indicates the magnitude (voltage) of the electric signal. Electricity including curves Pp, Rp, and Tp indicating the shapes of so-called P waves, R waves, and T waves, respectively. A curve showing the change in signal is shown.

  FIG. 4 is a schematic view illustrating a part of the breathing-stopped frame images constituting the breathing-stopping lung moving image. FIGS. 4A to 4C show the times Is1 to Is3 shown in FIG. The frame images during the breathing stop respectively taken at are shown. 4 (a) to 4 (c), hatched hatching is added to the lung field region during respiratory stop.

  FIG. 5 is a diagram exemplifying an electrocardiogram showing a change in electricity controlling the movement of the heart acquired at the time of capturing a lung moving image during breathing. In FIG. 5, similarly to FIG. 3, the horizontal axis indicates time, and the vertical axis indicates the magnitude (voltage) of the electric signal, and curves Pp, R, and T indicate the shapes of the so-called P wave, R wave, and T wave, respectively. Curves showing changes in electrical signals including Rp and Tp are shown.

  FIG. 6 is a schematic view illustrating a part of the breathing frame images constituting the breathing lung motion image. In FIGS. 6A to 6C, the times Im1 to Im3 shown in FIG. A captured frame image is shown. 6 (a) to 6 (c), sandy hatching is added to the breathing lung field region.

  In the present embodiment, based on the characteristic shape of the electrocardiogram (for example, the shape of P, R, T wave, etc.), the period and phase of the heart beat are recognized, and each respiratory stop frame image and each respiratory frame The phase of the heart beat when the image is taken is detected.

<Frame image association method>
7 and 8 are diagrams for explaining a frame image association method.

  As shown in FIGS. 7 and 8, each breathing frame image is associated with a breathing-stop frame image in which the phase of the heart beat at the time of imaging is substantially the same. For example, a breathing-stop frame image (FIG. 8 (a)) and a breathing frame image (FIG. 8 (d)) taken at times Is1 and Im1 having the same heart beat phase are associated with each other, and the heart The breathing-stop frame image (FIG. 8 (b)) and the breathing frame image (FIG. 8 (e)) taken at times Is2 and Im2 having the same pulsation phase are associated with each other, and the heart beat The breathing-stop frame images (FIG. 8 (c)) and the breathing-frame images (FIG. 8 (f)) taken at times Is3 and Im3 having the same phase are associated with each other.

<Method for generating fluctuation component image>
9 to 12 are diagrams for explaining a method of generating a fluctuation component image.

  Here, for example, as shown in FIG. 9, the breathing-stopped lung field region (hatched area) of the breathing-stopped frame image (FIG. 9A) is the breathing-stopping frame image (FIG. 9C). A fluctuation component image (FIG. 9B) is generated by correcting the shape to match the breathing lung field region (sandy hatched portion). That is, the difference between the breathing lung field region and the breathing stop lung field region between the two images is corrected.

  Various known methods can be adopted as a method for correcting the shift between the two images, for example, conversion of a set of line segments (for example, Feature-based image metamorphosis, ACM SIGGRAPH Computer Graphics archive). , Volume 26, Issue 2, July 1992, p35-42, etc.), other methods (see, for example, JP-A-63-278183, etc.) and the like can be employed.

  Hereinafter, a method of using a set of line segment conversion will be described in detail. Here, a predetermined point (for example, the upper left point) of each frame image is a reference point (for example, the origin), the right direction is the X axis direction, the lower direction is the Y axis direction, and the coordinate value for each pixel is It will change one by one.

  First, as schematically shown in FIGS. 10 (a) and 10 (b), there are a large number of lung field regions that are to be corrected and breathing lung field regions corresponding to the lung field regions that are breathing stopped. For example, about 200 feature points (for example, points with black circles in FIG. 10) are detected. Examples of the feature points include an inflection point, a sharp point, a point having a predetermined gradation, and the like of the lung field during breathing stop and the lung field during breathing. Note that various known techniques can be adopted as a technique for extracting the respiratory lung area and respiratory lung area outline. For example, an image obtained using X-rays (an X-ray image) ) For determining the contour of the lung field from the characteristics of the change in concentration (see, for example, JP-A-63-240832), other methods (for example, see JP-A-2-250180, etc.), etc. Can be adopted.

  Next, the correspondence between an arbitrary point X in the lung field during breathing stop and an arbitrary point X ′ in the lung field during breathing is obtained. Here, the correspondence relationship between the point X and the point X ′ is recognized for all the pixels in the lung field during breathing stop.

  Here, as shown in FIG. 11, two points P and Q included in the feature points of the lung field during respiratory arrest detected as described above, and the feature points of the lung field during breathing detected as described above. Attention is paid to two points P ′ and Q ′ corresponding to the two points P and Q.

  FIG. 12 is a diagram for explaining how to obtain the correspondence between the point X and the point X ′.

  In FIG. 12A, the vector from the point P ′ to the point Q ′ (P′Q ′ vector) and the point C ′ to the point X ′ that coincides with the perpendicular from the line segment P′Q ′ to the point X ′. A vector (C′X ′ vector) and a vector from the point P ′ to the point C ′ (P′C ′ vector) are shown. On the other hand, in FIG. 12B, a vector from the point P to the point Q (PQ vector), a vector from the point C to the point X that coincides with a perpendicular from the line segment PQ to the point X (CX vector), and a point P A vector from point to point C (PC vector) is shown.

  Here, when the P′Q ′ vector is converted into the PQ vector on the two-dimensional plane, the ratio between the P′Q ′ vector, the C′X ′ vector, and the P′C ′ vector, the PQ vector, and the CX vector It is assumed that the point X ′ is converted to the point X so that the ratio between the vector and the PC vector is constant.

  At this time, the following expressions (1) to (3) are established between the point X and the point X ′.

  Note that u represents a scalar obtained by dividing (normalizing) the length of the line segment PC by the length of the line segment PQ, v represents the distance from the straight line PQ to the point X, and X ′ represents the coordinates of the point X ′. Is shown. Further, (X−P) represents a coordinate change value obtained by subtracting the coordinate value of the point P from the coordinate value of the point X, that is, a vector (PX vector) from the point P to the point X, and (Q−P) represents A coordinate change value obtained by subtracting the value of the coordinate of the point P from the value of the coordinate of the point Q, that is, a PQ vector, Per (QP) is perpendicular to the PQ vector and is equal in magnitude and in the same direction as the CX vector Per (Q′−P ′) is a vector perpendicular to and equal in magnitude to the P′Q ′ vector and facing the same direction as the C′X ′ vector, and P ′ is a point The coordinates of P ′ are shown.

  Therefore, for the right side of the above equation (1), the numerator indicates the inner product of the PX vector and the PQ vector, and the denominator indicates the square of the size of the PQ vector (the square of the length of the line segment PQ). Yes. Regarding the right side of the above equation (2), the numerator indicates the inner product of the PX vector and Per (Q−P), and the denominator indicates the size of the PQ vector (the length of the line segment PQ). Further, the denominator of the third term on the right side of the above equation (3) indicates the size of the P′Q ′ vector (the length of the line segment PQ).

  Here, any two of the many feature points are set as points P and Q for the lung field during breathing stop, and two points corresponding to the two points P and Q are set for the lung field during breathing. P ′ and Q ′ are set. Many relations between the point X and the point X ′ are obtained with respect to an arbitrary point X in the lung field region during the breathing stop. However, the relationship between the point X and the point X ′ obtained for the setting of the points P and Q (and the points P ′ and Q ′) does not completely match. Therefore, a weighted average is used to obtain the relationship between the point X ′ and the point X as shown by the following equations (4) to (6) for each point X. In addition, as the weighted average, for example, weighting considering the size of the PQ vector, the detection accuracy of the points P and Q, the positional relationship between the PQ vector and the point X, and the like may be used.

Here, n points P and Q are set, and in the above equations (4) to (6), among the combinations of n points P and Q, the i-th point P and Q are respectively points P. _i and Q _i are indicated. X _i ′ is a coordinate obtained by the above equation (3) with respect to a vector from the point P _i to Q _i (P _i Q _i vector). Furthermore, a, b, and p are constants, and by changing the values of a, b, and p as appropriate, the manner of deformation of the lung field region during respiratory arrest is adjusted. As for the above equation (4), X ′ represents the coordinate of the point X ′, X represents the coordinate of the point X, ω _i represents the weight defined by the above equations (5) and (6), (X _i ′ −X) represents a vector (XX _i ′ vector) from the point X to the point X _i ′.

As shown in the above equation (5), the weight ω _i is obtained by dividing the b-th power of the vector (P _i Q _i vector) from the point P _i to the point Q _i by (a + DIST _i ) and raising it to the p-th power. . It should be noted that the condition represented by the above equation (6), u <0, is a condition where the point X is positioned on a perpendicular to the extension line on the P side of the line segment PQ, and 0 ≦ u ≦ 1, the point X is a line U <1 is a condition where the point X is located above the perpendicular to the extension line on the Q side of the line segment PQ.

As shown in the above equation (4), the coordinate of the point X ′ corresponding to the point X is obtained by adding the weighted average of the XX _i ′ vector of the second term on the right side to the coordinate of the point X.

  When the relationship between the point X and the point X ′ obtained by the above formulas (1) to (6) is obtained for all pixels in the lung field during respiratory arrest, the lung field during breathing is It is corrected to match the area. Such correction of the shift between the two images is an image process for performing non-linear enlargement and reduction of the image region, and can be referred to as a process for performing non-linear scaling, for example.

<Difference image generation>
FIG. 13 is a schematic diagram for explaining generation of a difference image.

  As shown in FIG. 13, for the combination of the breathing frame image (FIG. 13 (a)) and the fluctuation component image (FIG. 13 (b)) in which the phases of the pulsation of the heart at the time of imaging are substantially coincident, A difference image (FIG. 13C) between the image and the fluctuation component image is generated. Such a difference image is generated for each breathing frame image constituting the breathing lung moving image, thereby obtaining a moving image that captures the motion of a predetermined part from which the influence of blood flow has been removed. Note that the lung contour in the variation component image may be adjusted as appropriate so that the lung contour in the difference image is not obscured.

  As described above, in the image acquisition system 1 according to the embodiment of the present invention, a fluctuation component (here, a fluctuation component due to blood flow) caused by a part other than the predetermined part with respect to the predetermined part (here, the lung) whose shape changes. An image from which is removed is acquired. For this reason, it is possible to distinguish and visually recognize the feature of the predetermined part whose shape changes and the other feature, and the diagnosis can be easily performed. In particular, diagnosis is further facilitated by obtaining a moving image from which a fluctuation component caused by a part other than a predetermined part is removed.

<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 embodiment, the phase of the heart beat at the time of capturing each frame image is detected by detecting the change in electricity that controls the movement of the heart. However, the present invention is not limited to this. . For example, a configuration in which the phase of the heart beat at the time of capturing each frame image is detected by image processing using an image that captures an area including the heart, such as a breathing lung motion image and a breathing stop lung motion image May be adopted. Hereinafter, a specific example will be described.

  FIG. 14A is a diagram illustrating the overall configuration of an image acquisition system 1A according to a modification of the present invention, and FIG. 14B is a block diagram illustrating the configuration of the image acquisition system 1A.

  In the image acquisition system 1A, the electrocardiograph 6 is removed from the image acquisition system 1 shown in FIGS. 1A and 1B, the program PG is changed to the program PGA, and the image generation device 2 is changed to the image generation device 2A. It has the structure changed into. 14 (a) and 14 (b), the same components as those shown in FIGS. 1 (a) and 1 (b) are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 15 is a diagram illustrating a functional configuration realized by the image generation apparatus 2A according to the modification together with other configurations by the CPU 21 operating according to the program PGA. The functional configuration shown in FIG. 15 is obtained by deleting the measurement control unit 212 and the electrocardiogram acquisition unit 214 from the functional configuration shown in FIG. 2 and changing the phase detection unit 215 to the phase detection unit 215A. In FIG. 15, parts similar to those in the configuration shown in FIG.

  Hereinafter, the phase detection unit 215A, which is a different part from the image generation device 2 according to the above-described embodiment, will be described regarding the functional configuration of the image generation device 2A according to the modification.

  The phase detection unit 215A calculates the phase of the heart beat at the timing when each breathing frame image and each breathing-stop frame image is captured by image processing using the breathing lung motion image and the breathing-stopping lung motion image. To detect. Here, each frame image is associated with the phase of the heart beat. The information associated here is appropriately stored in the RAM 22 or the fixed disk 24.

  Here, a phase detection method during photographing according to a modification will be described.

  Here, as shown in FIG. 16, for each breathing frame image and each breathing-stop frame image, a predetermined point (for example, the upper left point) is set as a reference point (for example, the origin), the right direction is set as the X axis direction, and It is assumed that the direction is the Y-axis direction, and the coordinate value changes by one for each pixel.

  FIG. 17 is a schematic view illustrating the change in the lateral width of the heart captured in the lung motion image during breathing stop. 17A to 17C illustrate a state in which the lateral width of the heart increases from w1 to w3 in the process of expanding the heart.

  Here, it is used that the heart is captured together with the lung, which is a predetermined region to be imaged, in the breathing lung motion image and the breathing stop lung motion image. Specifically, by detecting fluctuations in the lateral width of the heart in the breathing lung motion image and the breathing stop lung motion image, the heart at the timing when each breathing frame image and each breathing stop frame image was taken. The phase of the beat is detected. For example, the width of the heart may be detected as the phase of the heart beat.

  As a technique for detecting the width of the heart from each breathing frame image and each breathing-stop frame image, for example, a technique of detecting the outline of the heart and the like can be mentioned. As a method for detecting the outline of the heart, various known methods can be employed. For example, using a model (heart model) indicating the shape of the heart, a feature point in the X-ray image, Techniques for detecting the outline of the heart by matching with the feature points of the heart model (for example, "Image feature analysis and computer-aided diagnosis in digital radiography: Automated analysis of sizes of heart and lung in chest images", Nobuyuki Nakamori et al., Medical Physics, Volume 17, Issue 3, May, 1990, pp.342-350.

  FIG. 18 is a schematic view illustrating the relationship between the time taken and the lateral width of the heart for a plurality of breathing-stopped frame images constituting the breathing-stopping lung moving image. In FIG. 18, the horizontal axis indicates time, the vertical axis indicates the width of the heart, and the value of the width of the heart from which a circle is detected is illustrated.

Here, if the lateral width of the heart captured at time t is Hw _t , the lateral width of the heart captured at time t + 1 is Hw _{t + 1,} and (Hw _{t + 1} −Hw _t ) ≧ 0 holds, When the breathing-stop frame image captured at time t is classified when the heart is dilated, and (Hw _{t + 1} −Hw _t ) <0 holds, the breath-stop frame image captured at time t is the heart Classified at the time of contraction.

  FIG. 19 is a schematic view exemplifying a state in which a plurality of breathing-stopped frame images constituting a breathing-stopping lung moving image are classified into a heart expansion time and a contraction time. In FIG. 19, a circle indicating the lateral width of the heart related to each frame image during respiratory arrest classified at the time of expansion is hatched with hatching, and the lateral width of the heart related to each frame image during respiratory arrest classified at the time of contraction is shown. The circles are hatched with sand, and a period Pe during expansion and a period Pc during contraction are shown. More specifically, circles p1, p2, p5, p6, p10, and p11 are hatched, and circles p3, p4, p7 to p9, p12, and p13 are sanded.

  Next, the plurality of frame images during respiratory arrest classified at the time of expansion are rearranged in the order of expansion of the lateral width of the heart, and the frame images during respiratory arrest classified at the time of contraction are rearranged in the order of contraction of the lateral width of the heart.

  FIG. 20 is a diagram illustrating a state where a plurality of breathing-stop frame images are rearranged in the expansion order and the contraction order.

  In FIG. 20, among circles p1 to p13 shown in FIG. 19, circles p1, p2, p5, p6, p10, and p11 with hatching are in descending order of the width of the heart (circles p1, p5). , P10, p6, p11, p2) and the circles p3, p4, p7 to p9, p12, p13 with sandy hatching are in descending order of the width of the heart (circles p7, p3, p12). , P13, p8, p4, and p9).

  FIG. 21 is a schematic view illustrating the relationship between the time taken and the lateral width of the heart for a plurality of respiratory frame images constituting the respiratory lung motion image. The width of the heart associated with each breathing frame image is obtained from each breathing frame image by a method similar to the method of obtaining the heart width from each breathing stop frame image.

  In FIG. 21, the circle indicates the value of the width of the heart, and as in FIG. 19, the circle indicating the width of the heart related to each breathing frame image classified at the time of expansion is hatched with diagonal lines. The circle indicating the width of the heart associated with each breathing frame image classified at the time of contraction is hatched with sand, and the period Pe during expansion and the period Pc during contraction are shown. More specifically, circles q1, q2, q5, q6, q10, and q11 are hatched, and circles q3, q4, q7 to q9, q12, and q13 are sanded. The method for classifying each breathing frame image is the same as the method for classifying each breathing-stop frame image.

  Then, for each breathing frame image classified into expansion and contraction as shown in FIG. 21, a breathing-stop frame image in which each breathing frame image and the phase of the heartbeat at the time of imaging substantially coincide with each other. , From a plurality of breathing-stop frame images as shown in FIG. Here, a frame image during breathing stop corresponding to the frame image during breathing is recognized based on three types of information: a classification state during expansion, a classification state during contraction, and the lateral width of the heart.

  Specifically, for each breathing frame image classified at the time of expansion, as shown in FIG. 20, a plurality of frame images during breathing stop classified at the time of expansion and arranged in the order of decreasing width of the heart are used. The breathing-stop frame image having the closest width is recognized. On the other hand, for each breathing frame image classified at the time of contraction, as shown in FIG. 20, the width of the heart is determined from a plurality of frame images during breathing stop sorted at the time of contraction and arranged in descending order. The closest breathing-stop frame image is recognized. For example, a breathing stop frame image related to the circle mark p6 is recognized for the breathing frame image related to the circle mark q2, and a breathing stop related to the circle mark p7 is compared to the breathing frame image related to the circle mark q7. The frame image is recognized, and the breathing-stop frame image related to the circle p13 is recognized for the breathing frame image related to the circle q13.

  In FIG. 18 to FIG. 21, the number of frame images taken during one cycle of the heart beat is reduced for the purpose of preventing the complication of the illustration. The number of frame images taken during one cycle is large (for example, about 25). For this reason, if the pulmonary motion image during breathing and the pulmonary motion image during breathing stop are captured for several cycles of heart pulsation, the heart pulsation of all the breathing frame images constituting the pulmonary motion image during breathing is captured. A breathing-stop frame image having substantially the same phase is recognized.

  As described above, according to the configuration in which the phase of the heart beat at the time of capturing each frame image is detected by the image processing using the breathing lung motion image and the breathing stop lung motion image, the electrocardiograph 6 and the like The periodic movement of the heart at the time of capturing each frame image is detected with a simple configuration without providing a special configuration.

  However, in the configuration in which the phase of the heart beat at the time of capturing each frame image is detected by image processing using the breathing lung moving image and the breathing stopped lung moving image, a so-called frame rate for capturing the moving image is set. In a relatively small case, it tends to be difficult to accurately recognize the maximum expansion and contraction of the heart. For this reason, from the viewpoint of accurately detecting the phase of the periodic movement of the heart at the time of capturing each frame image, as shown in the above embodiment, a change in electricity that controls the movement of the heart is detected. Thus, it is preferable to detect the phase of the heart beat when each frame image is captured.

  It should be noted that the phase of the pulsation of the heart is determined only by the lateral width of the heart, which is classified and rearranged into the time of expansion and the time of contraction of the plurality of frame images during the breathing stop constituting the lung motion image during the breathing stop This is to avoid a problem that makes it impossible to distinguish between expansion and contraction.

  In the above embodiment, the differential moving image is generated, but the present invention is not limited to this. For example, with respect to one breathing frame image, one breathing stop frame image whose heart beat phases substantially coincide is recognized, and based on the one breathing frame image and one breathing stop frame image. One difference frame image may be generated. Even in such a configuration, an image obtained by removing a fluctuation component due to a part other than the predetermined part is obtained for the predetermined part whose shape changes. However, from the viewpoint of making a better diagnosis by visually recognizing the movement of a predetermined part, it is preferable to generate a differential moving image as in the above embodiment.

  In the above embodiment, the predetermined region to be imaged is the lung, but is not limited thereto. For example, the predetermined part to be imaged may be a part whose shape changes such as a key or a line. In other words, the image of the predetermined part affected by the fluctuation component caused by the part other than the predetermined part such as the blood flow flowing through the blood vessel located around the predetermined part may be acquired simply by photographing the predetermined part. Any part may be used.

  In the above embodiment, the predetermined part included in the person is the object to be imaged. However, the present invention is not limited to this, and the object to be imaged may be a part constituting the inside of an animal in general.

  In the above embodiment, an image of a predetermined part is acquired by imaging using X-rays, but the present invention is not limited to this. For example, a transmission image of a predetermined site may be acquired using nuclear magnetic resonance imaging (MRI) or the like.

It is a figure which illustrates the whole structure of the image acquisition system which concerns on embodiment of this invention. It is a block diagram which shows the function structure of the image generation apparatus which concerns on embodiment of this invention. It is a schematic diagram which illustrates a part of electrocardiogram. It is a schematic diagram which illustrates the frame image during a breathing stop. It is a schematic diagram which illustrates a part of electrocardiogram. It is a schematic diagram which illustrates a breathing frame image. It is a figure for demonstrating the matching method of a frame image. It is a figure for demonstrating the matching method of a frame image. It is a figure for demonstrating the production | generation method of a fluctuation | variation component image. It is a figure for demonstrating the production | generation method of a fluctuation | variation component image. It is a figure for demonstrating the production | generation method of a fluctuation | variation component image. It is a figure for demonstrating the production | generation method of a fluctuation | variation component image. It is a schematic diagram for demonstrating the production | generation of a difference image. It is a figure which illustrates the whole structure of the image acquisition system which concerns on the modification of this invention. It is a block diagram which shows the function structure of the image generation apparatus which concerns on the modification of this invention. It is a figure which illustrates the setting state of the coordinate axis with respect to an image. It is a schematic diagram which illustrates the fluctuation | variation of the lateral width of the heart. It is a schematic diagram which illustrates the fluctuation | variation cycle of the width of the heart which concerns on the pulmonary moving image during a respiration stop. It is a schematic diagram which illustrates the fluctuation | variation cycle of the width of the heart which concerns on the pulmonary moving image during a respiration stop. It is the figure which rearranged the frame image during a breathing stop into expansion order and contraction order. It is a schematic diagram which illustrates the fluctuation | variation cycle of the width of the heart which concerns on the pulmonary moving image during a breath.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A Image acquisition system 2,2A Image generation apparatus 5 Medical imaging device 6 Electrocardiograph 21 CPU
22 RAM
23 ROM
211 imaging control unit 212 measurement control unit 213 image acquisition unit 213a first image acquisition unit 213b second image acquisition unit 214 electrocardiogram acquisition unit 215, 215A phase detection unit 216 corresponding image recognition unit 217 fluctuation component image generation unit 218 differential image generation unit 219 Storage control unit PG, PGA program

Claims (8)

First acquisition means for acquiring a first moving image that captures a state in which the shape of a predetermined part constituting the interior of the animal changes;
Second acquisition means for acquiring a second moving image that captures a state in which the change in shape of the predetermined portion has stopped;
The phase of the cyclic motion of the animal's heart at the timing when each of the plurality of first frame images included in the first moving image is captured, and each of the plurality of second frame images included in the second moving image. Detecting means for detecting a phase of the periodic movement of the heart at the timing of imaging;
Recognizing means for recognizing a combination of the first frame image and the second frame image taken at a timing at which the phases of the periodic movements of the heart substantially coincide with each other according to a detection result by the detecting means;
For the combination, the second region is corrected so that the second region capturing the predetermined part of the second frame image matches the first region capturing the predetermined part of the first frame image. First generating means for generating a fluctuation component image;
Second generation means for generating a difference image between the first frame image and the fluctuation component image for the combination;
An image generation apparatus comprising: The image generation apparatus according to claim 1,
The recognition means is
Recognizing a plurality of combinations of the first frame image and the second frame image captured at a timing at which the phases of the periodic movements of the heart substantially coincide with each other according to the detection result by the detection unit,
The first generating means;
For each of the combinations, the second region is corrected so that the second region capturing the predetermined portion of the second frame image matches the first region capturing the predetermined portion of the first frame image. To generate each fluctuation component image,
The second generation means comprises:
An image generation apparatus, wherein a difference image between the first frame image and the variation component image is generated for each combination. The image generation apparatus according to claim 1 or 2, wherein
The image generating apparatus, wherein the predetermined part includes a lung. An image generation apparatus according to any one of claims 1 to 3,
The first generating means;
An image generating apparatus, wherein the fluctuation component image is generated by correcting only the second area so that the second area matches the first area. An image generation apparatus according to any one of claims 1 to 4,
The detecting means;
An image generating apparatus, wherein a phase of a periodic movement of the heart is detected by using a change in electricity that controls the movement of the heart. An image generation apparatus according to any one of claims 1 to 4,
The first and second moving images are
Each is a moving image that captures the region including the heart,
The detecting means;
An image generating apparatus that detects a phase of a periodic motion of the heart based on a change in a shape of the heart captured by the first and second moving images.   A program for causing the image generation apparatus to function as the image generation apparatus according to any one of claims 1 to 6 when executed by a computer included in the image generation apparatus. A first acquisition step of acquiring a first moving image that captures a state in which the shape of a predetermined part constituting the interior of the animal changes;
A second acquisition step of acquiring a second moving image that captures a state in which the change in the shape of the predetermined part has stopped;
The phase of the cyclic motion of the animal's heart at the timing when each of the plurality of first frame images included in the first moving image is captured, and each of the plurality of second frame images included in the second moving image. A detection step for detecting a phase of the periodic movement of the heart at the time when the imaging was performed;
A recognition step of recognizing a combination of the first frame image and the second frame image taken at a timing at which the phases of the periodic movements of the heart substantially coincide with each other according to a detection result in the detection step;
For the combination, the second region is corrected so that the second region capturing the predetermined part of the second frame image matches the first region capturing the predetermined part of the first frame image. A first generation step of generating a fluctuation component image,
A second generation step of generating a difference image between the first frame image and the fluctuation component image for the combination;
An image generation method comprising:

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