JP2009297077A - Image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an index expressing the action of a periodically active region of a subject. <P>SOLUTION: An image data storage part 11 stores data of a plurality of projected images on a region including the heart of the subject over a plurality of heartbeat periods. An image processing part 12 creates an integrated image based on the data of a plurality of projected images corresponding to the approximately same cardiac phase among the plurality of stored projected images. The image processing part 12 counts the number of first pixels having the pixel value exceeding a prescribed threshold of the created integrated image, and counts the number of second pixels having the pixel value exceeding the threshold of the projection image corresponding to the same cardiac phase as the created image. The ratio of the first pixel number to the second pixel number is output as the index expressing the action of the heart. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus that processes data of a plurality of projection images related to a subject collected continuously.

  Currently, using a cardiovascular X-ray diagnostic system, a coronary artery imaged with a contrast agent is imaged to diagnose a lesion. Applications such as ECG gate display and Coronary Tree that are installed in such systems use the fact that the heart's expansion and contraction movement has position periodicity, or that there is a moment when the movement of the heart is almost stationary. Is used.

In addition, as a well-known document relevant to this application, there exist the following, for example.
JP 2004-411 A JP 2004-121834 A JP 2004-313513 A

  However, in the application as described above, at present, the position cycle is uniformly set to, for example, RR 80% in the middle diastole. Strictly speaking, however, there are individual differences among patients, and thus the standard values as described above are not necessarily the optimal cardiac phase for all patients.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image processing apparatus that can provide an index representing the movement of a part of a subject that moves periodically.

In order to achieve the above object, the present invention takes the following measures.
The first aspect of the present invention corresponds to a storage unit that stores data of a plurality of projection images over a plurality of periods related to a periodically moving part, and corresponds to substantially the same phase among the plurality of stored projection images. An image generation unit that generates data of a single image based on data of a plurality of projection images, and a first pixel number of pixels having a pixel value exceeding a predetermined threshold for the generated single image A first counting unit that counts, a second counting unit that counts a second number of pixels having a pixel value that exceeds the threshold for a projection image corresponding to the same phase as the generated image, and the first An index generation unit configured to generate an index representing the movement of the part based on the number of pixels and the second number of pixels.

  Moreover, the 2nd aspect of this invention is a collection part which memorize | stores the data of the several projection image regarding the site | part which is continuously collected and periodically moved, and collection time among the said some stored projection images An image generation unit that generates data of a single image based on data of a plurality of continuous projection images, and a first pixel having a pixel value exceeding a predetermined threshold value for the generated single image. A first counting unit that counts the number of pixels, and a second counting unit that counts a second number of pixels having a pixel value exceeding the threshold for a projection image corresponding to the same collection time as the generated image; And an index generation unit that generates an index representing the movement of the part based on the first pixel number and the second pixel number.

  According to a third aspect of the present invention, there is provided a storage unit that stores data of a plurality of projection images over a plurality of cycles related to a region that moves periodically, and among the stored projection images, the collection time is the heartbeat cycle. An image generation unit that generates data of a single image based on the data of a plurality of discrete projection images according to the above, and for the generated single image, the first of pixels having a pixel value exceeding a predetermined threshold A first counting unit that counts the number of pixels, a second counting unit that counts a second number of pixels having a pixel value exceeding the threshold, with respect to a projection image corresponding to the same time as the generated image; An index generation unit configured to generate an index representing the motion of the heart based on the first pixel number and the second pixel number;

  As mentioned above, according to this invention, the image processing apparatus which can provide the parameter | index showing the motion of the site | part which exercise | moves periodically can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, taking as an example the case where an image processing apparatus according to the present invention is applied to an X-ray diagnostic apparatus. The X-ray diagnostic apparatus is a circulatory X-ray diagnostic apparatus, and here, it is assumed that a contrasted moving image of the coronary artery is captured.

  As shown in FIG. 1, the X-ray diagnostic apparatus has a C-arm device 5. The C arm device 5 includes a C arm 16, a floor or ceiling suspension support mechanism that supports the C arm 16 so as to be rotatable about three orthogonal axes, and a rotational drive source. The X-ray tube 1 is attached to one end of the C arm 16. The X-ray control unit 4 applies a tube voltage between the electrodes of the X-ray tube 1 in order to generate X-rays from the X-ray tube 1 according to the control of the system control unit 9, and the cathode filament of the X-ray tube 1 To supply a heating current. The X-ray detector 2 is attached to the other end of the C arm 16. The X-ray tube 1 and the X-ray detector 2 face each other with the subject P on the bed 3 interposed therebetween. The X-ray detector 2 is composed of, for example, a combination of an image intensifier and a TV camera. Alternatively, the X-ray detector 2 is composed of a flat panel detector (FPD: planar X-ray detector) having semiconductor detection elements arranged in a matrix. The C-arm movement control unit 6 supplies electric power to the drive source for rotating the C-arm 16 according to the control of the system control unit 9. Further, the bed moving mechanism 7 supplies power to the drive source for moving the bed 3 according to the control of the system control unit 9.

  In this X-ray diagnostic apparatus, an electrocardiograph 10 is equipped to measure the subject P and generate an electrocardiogram. The image data storage unit 11 stores data relating to a plurality of projection images generated by the X-ray detector 2 in association with cardiac phase data acquired by the system control unit 9 from the electrocardiogram. The cardiac phase is defined as a scale that defines each time point in the period from the R wave of the electrocardiogram to the next R wave. Typically, the period from the R wave to the next R wave is 100%. Normalize and indicate each point in the period in percent. That is, RR 0% indicates the moment when the R wave comes, and RR 100% indicates the moment when the next R wave comes.

  The plurality of projected images constitute a moving image, and are continuously imaged at a rate of, for example, 30 frames / second, that is, 30 images per second, preferably at least 3 heartbeat cycles. The electrocardiogram is measured in parallel with the imaging of the plurality of projection images, and the data of the plurality of projection images is stored in the image data storage unit 11 together with the data of the cardiac phase (%) specified by the system control unit 9. In the present embodiment, the image data storage unit 11 stores a plurality of frames of projected images obtained by continuously imaging a contrasted cardiac coronary artery over a plurality of heartbeats together with electrocardiogram data.

  The operation unit 8 is provided to transmit various commands from the user to the system control unit 9, and includes various input devices such as a keyboard and a mouse. The monitor 13 is configured by a CRT (cathode-ray tube), a liquid crystal display (LCD), or the like.

  Furthermore, in this embodiment, the image processing unit 12 is provided in order to provide an index representing the periodic movement of the heart. Here, the positional periodicity of the heart will be described with reference to FIG. In the upper diagram of FIG. 2, the horizontal axis represents time (frame) and the vertical axis represents the stenosis position of the heart over three heartbeats. The lower diagram of FIG. 2 displays the heart phases for each heartbeat in the upper diagram in an overlapping manner. A flat portion indicates a time when there is little movement, and this time is defined as a “still heart phase”. On the other hand, there is a time when all the lines overlap, and this time is defined as “a cardiac phase with good position reproducibility”. That is, it is a cardiac phase that is easy to repeat at the same position in the trajectory of the expansion and contraction motion of the heart.

  The image processing unit 12 generates an index representing the periodic movement of the heart by performing image processing on the projection image stored in the image data storage unit 11. FIG. 3 shows a basic operation procedure of the image processing unit 12. The image processing unit 12 reads a projection image from the image data storage unit 11 (step S1a), and extracts a plurality of frames according to a predetermined rule (step S2a). The number of pixels (pixels in the blood vessel region) having a pixel value exceeding a predetermined threshold for the extracted frame is counted (step S3a). In addition, the image processing unit 12 generates a single integrated image using the frame extracted in step S2a (step S4a), and the generated integrated image includes pixels having pixel values exceeding the threshold (on the integrated image). The number of pixels of the blood vessel region) is counted (step S5a). The image processing unit 12 calculates the ratio between the number of pixels in step S3a and the number of pixels obtained in S5a (step S6a). The image processing unit 12 provides the calculated ratio value as an index representing the relationship of the amount of motion with respect to the cardiac phase.

  In general, when a cardiovascular vessel is viewed in a projected image, the cardiovascular vessel becomes smaller during systole and becomes larger during diastole due to the heartbeat. That is, the image area occupied by the blood vessel area changes between the systole and the diastole. Therefore, in the method of counting the number of pixels of blood vessels, the value tends to be small in the systole and large in the diastole, and this influence makes the systole more likely to be the optimal cardiac phase, and is evaluated correctly. I can't.

  For example, in FIG. 4, the upper left is the original image in the systole, the upper right is the original image in the diastole, the lower left is the integrated image in the systole, and the lower row is the integrated image in the diastole. If the amount of motion is the same, the number of pixels in the integrated image increases by the number of hatched mesh pixels in the contraction period, but the number of pixels in the integrated image increases by the number of shaded mesh pixels in the expansion period. Obviously, the shaded mesh has a larger number of pixels, so even if it moves the same, the result is that the movement is larger in the expansion period. In contrast, in this embodiment, the ratio R (p) of the blood vessel area of the integrated image to the original blood vessel area for each cardiac phase is calculated as an index of heart motion, so the same index is used in both the systole and the diastole. It can be obtained.

  Hereinafter, specific processing contents of the image processing unit 12 will be described according to each embodiment.

(Example 1)
In the first embodiment, a method for quantitatively detecting a cardiac phase with the best position reproducibility from a contrast coronary artery moving image captured by a cardiovascular X-ray imaging system will be described.

FIG. 5 is a flowchart illustrating the operation procedure of the image processing unit 12 according to the first embodiment. 6A and 6B are diagrams showing the operation of FIG.
In FIG. 5, first, the image processing unit 12 reads out an image group stored in the image data storage unit 11 (step S1b). For example, it is assumed that this image group consists of 120 frames (30 fps × 4 seconds). In this image group, electrocardiogram data is stored as incidental information. The image processing unit 12 extracts one image for one heartbeat from the read image group based on the electrocardiogram signal, and uses this as the original image A (p) (step S2b). Here, p is a cardiac phase and takes a value of 0 ≦ p <100. The cardiac phase of 0% is the moment that coincides with the R wave, and the cardiac phase of 100% is the moment that coincides with the next R wave. For example, when p is set every 5% steps, 20 types of original images A, A0, A5, A10,..., A95 are obtained. Each image A (p) is composed of, for example, 4 frames (4 heartbeats).

  Since the original image A (p) also shows the lungs, bones and other organs in addition to the coronary artery, background difference processing is performed as necessary in order to remove them (step S3b). As an example of the background difference processing, there are two methods described later, and either or both of them can be implemented. In the first method, only high frequency components are left and low frequency components are differentiated. Specifically, a blurred image of the original image A is created, and a difference from the original image A is set as a high frequency image. In this method, a background structure having a large low frequency component such as a diaphragm can be removed. The second method is a method of subtracting a frame before angiography from each of the original images A (p). Specifically, the frame having the earliest time acquired at the same cardiac phase is subtracted. With this method, bones and the like that are immobile organs can be removed. In the image after the background difference, as shown in FIGS. 6A and 6B, the heart coronary artery is clearly displayed in white, and this image is referred to as a background difference image B (p). Each background difference image B (p) consists of 4 frames.

Next, the image processing unit 12 counts the number of pixels having a pixel value exceeding the threshold for the background difference image B (p) (step S4b). That is, the number of pixels in the area occupied by the coronary artery on the image is counted. As the threshold setting method, for example, there are a method of setting a predetermined value, a method of calculating from a histogram of an image, and a method of calculating from a variance of an image, and any method may be used. The threshold can also be zero. Further, since the background difference image B (p) includes a plurality of frames of images for each of the cardiac phases p, the maximum value is detected and this is designated as N _B (p). Alternatively, a representative image may be used and the number of pixels may be N _B (p).

  Next, the image processing unit 12 generates a maximum value projection image (MIP: Maximum Intensity Projection) (step S4b). Here, a description will be given using an image that has been subjected to the background difference process described above. In the image after background difference processing, the blood vessel portion is white and the background is black. In an image on which background difference processing has not been performed, the blood vessel portion is black and the background is white. In the case of processing with an image on which background difference processing has not been performed, it is assumed that black and white (or maximum / minimum) in the following description is reversed and read.

  Since the background difference image B (p) has a plurality of frames (here, 4 frames), the maximum value image (MIP) thereof is taken. As a method of taking MIP, there are a method of taking MIP of all frames, or a method of generating a MIP image of only a designated frame (Slab MIP). In general, MIP for all frames is sufficient. Let the image after MIP be a MIP image C (p). As shown in FIGS. 6A and 6B, the MIP image C (p) is an image in which a plurality of blood vessels appear. One MIP image C (p) is generated for each cardiac phase p.

Next, the image processing unit 12 counts the number of blood vessel pixels for the MIP image C (p) (step S6b). Using the same value as the threshold value of step S4b described above, the number of pixels having a pixel value exceeding the threshold value is counted from the MIP image C (p), and this is defined as N _C (p).

The image processing unit 12 calculates the ratio of N _B (p) to N _C (p) (step S7b). The ratio R (p) is obtained by R (p) = N _C (p) ÷ N _B (p), and is one value for each cardiac phase p. The ratio R (p) obtained here has a meaning as an index representing the motion of the heart. For example, if the extracted background difference image B (p) is two images, if there is no blood vessel movement between the two images, N _C = N _B and the ratio R (p) = 1. It becomes. If the movement of the blood vessel between these two images is very large, the image C shows that there are two blood vessels, and N _C (p) is equivalent to almost twice N _B (p). The ratio R (p) = 2. That is, the degree of movement can be determined by referring to the ratio R (p). In the first embodiment, the ratio R (p) is 1 or more, and it is empirically distributed in the range of 1 to 2 when the movement is very small, and distributed to about 2 to 3 when the movement is large. There are many. In addition, when disturbance components such as diaphragm movement enter, it is often 3 or more.

  The above-described processing from step S2b to S7b is performed for all the cardiac phases p (step S8b). In this way, the relationship of the ratio R (p) to the cardiac phase p is obtained as an index representing the heart motion (step S9b). Then, the value of the ratio R (p) with respect to the cardiac phase p is displayed on the graph (step S10b). Further, based on this graph, the cardiac phase p that makes the ratio R (p) the smallest is detected. At this time, since there are many cases where noise is added to the ratio R (p), the cardiac phase p that is minimized after the smoothing process such as spline interpolation may be detected.

  FIG. 7 shows a clinical example of Example 1. The horizontal axis indicates the cardiac phase (0 to 100%), and the vertical axis indicates the value of R (p). In this example, it is understood that the position reproducibility is the worst when the cardiac phase is 10% or 85%, and the position reproducibility is the best when RR is 45%.

  The cardiac phase P obtained by the above processing is output as “the cardiac phase with the best position reproducibility”. For example, if the image group B (P) is sequentially displayed on the screen using the image group B (P) corresponding to the obtained cardiac phase P, an ECG gated display is performed with the cardiac phase P.

  As described above, in the first embodiment, the ratio R (p) serving as an index representing the motion of the heart can be obtained, and the cardiac phase with the best position reproducibility can be specified. Using this property, for example, if the ratio R (P) in the optimal cardiac phase P is 2 or less, the subsequent process is executed. If R (p) is 2 or more, the subsequent process is not executed. In addition, it is possible to urge the operator to re-image the projected image. According to this method, it is possible to detect poor breath-holding.

  In Example 1, an MIP image was generated as an integrated image. Angiographic images that are imaged in a general routine are often recorded, for example, about 4 seconds of behavior. The first 1 second is imaged without any contrast agent, and the blood vessel is contrasted for 2 seconds. In many cases, the imaging is performed in a state where the contrast agent is deeply filled, and the last one second is captured in a state in which the contrast agent escapes from the blood vessel. When processing such as averaging is performed on such an input image, the value of the projection image C (p) changes depending on the behavior state of the contrast agent. For example, when using the averaging process, if the number of frames before injection of the contrast agent is large, the pixel value of the blood vessel in the averaged image becomes low. For this reason, it is extremely difficult to set a threshold value when counting the number of pixels in the subsequent stage. On the other hand, in the case of the MIP processing, the frame without the contrast agent injected has no effect on the post-MIP image, and therefore it does not matter how many frames are not contrasted. As described above, the MIP processing can maintain high robustness with respect to the angiographic image captured by the cardiovascular X-ray system, and is particularly useful in the case of an X-ray image.

(Example 2)
In the second embodiment, a technique for quantitatively detecting the most stationary cardiac phase from a contrast moving image of the cardiac coronary artery imaged by the cardiovascular X-ray imaging system will be described.
FIG. 8 is a flowchart illustrating an operation procedure of the image processing unit 12 according to the second embodiment. FIG. 9 is a diagram showing the operation of FIG.

  The image processing unit 12 reads out the image group stored in the image data storage unit 11 (step S1c). The image group stores electrocardiogram data as incidental information. Two frames that are adjacent in time are extracted from this image group, and this is used as the original image A (p). If there are N frames in the image group, the original image A (p) has N-1 images of 2 frames (step S2c).

Next, the image processing unit 12 performs background difference processing on the original image A (p) as necessary (step S3c). The background difference processing method uses the method described in the first embodiment. Let the image after background difference be background difference image B (p). For the background difference image B (p), the number of pixels having pixel values exceeding a predetermined threshold is counted (step S4c). As the threshold setting method, the method described in the first embodiment is used. The number of pixels counted from the background difference image B (p) is N _B (p).

A MIP image is created for the background difference image B (p) (step S5c). Since each of the images B (p) is an image of two frames, MIP of the two images is taken. Let the image after MIP be a MIP image C (p). Then, for the MIP image C (p), the number of pixels having a pixel value exceeding the threshold value is counted (step S6c). Here, it is assumed that the counted number of pixels is N _C (p). Next, the ratio R (p) between N _B (p) and N _C (p) is calculated (step S7c). The ratio R (p) = N _C (p) ÷ N _B (p).

  The processes in steps S2c to S7c so far are performed for all frames (step S8c). Since the cardiac phase in each frame is known, the relationship of the ratio R (p) to each cardiac phase p is obtained (step S9c). As shown in FIG. 10, in Example 1, since the number of frames to be extracted is always two, the ratio R (p) is always distributed in the range of 1-2. In addition, when there are data for a plurality of heartbeats, a relationship can be obtained for each heartbeat. In this case, finally, a plurality of data may be averaged and smoothed to form one data (step S10c).

  Hereinafter, the relationship of the ratio R (p) to the cardiac phase p is displayed as a graph as required by the application (step S11c). Further, the cardiac phase P that makes R (p) the smallest is detected, and this cardiac phase P is output as the “stationary cardiac phase” (step S11c).

  In the second embodiment, two frames that are adjacent in time are extracted. However, the present invention is not limited to two frames, and may be three or four frames.

(Example 3)
The third embodiment is a combination of the first embodiment and the second embodiment described above, and is a cardiac phase having a stationary heart phase and good position reproducibility (hereinafter referred to as a stationary cardiac phase having good position reproducibility). ) Will be described quantitatively.
FIG. 11 is a flowchart illustrating an operation procedure of the image processing unit 12 according to the third embodiment. FIG. 12 is a diagram showing the operation of FIG.

  The image processing unit 12 reads an image group stored in the image data storage unit 11 (step S1d). The image group stores electrocardiogram data as incidental information. From this group of images, a frame that falls within a certain window width with the same cardiac phase p for each heartbeat is extracted and used as an original image A (p) (step S2d). The window width can be arbitrarily set, for example, 100 msec. For example, when p is set every 5% steps, 20 types of original images A (p) A0, A5, A10,..., A95 are generated. The number of images in each original image A (p) depends on the window width. For example, if the window width is 66 msec for data collected for 5 heartbeats at 30 fps (interval of 33 msec), there are about 2 images in the window at each heartbeat, so 2 images x 5 heartbeats = 10 images Is the number of original images A (p).

Next, the image processing unit 12 performs background difference processing on the original image A (p) (step S3d). This method is performed as necessary, and may be the same as the method described in the first embodiment. The image group after the background difference is defined as a background difference image B (p). For the background difference image B (p), the number of pixels having pixel values exceeding a predetermined threshold is counted (step S4d). As the threshold setting method, the method described in the first embodiment is used. Since there are multiple images in the background difference image _B (p), the image processing unit detects the maximum value of the number of pixels counted from each background difference image B (p) and sets this as N _B (p) 12 generates a MIP image based on the background difference image B (p) (step S5d). Since the background difference image B (p) has a plurality of frames, the maximum value image (MIP) thereof is taken. Let the image after MIP be an image C (p). The MIP image C (p) is an image in which a plurality of blood vessels appear to overlap. The MIP image C (p) is one image for each cardiac phase p. Further, the number of pixels having a pixel value exceeding a predetermined threshold is counted for the generated MIP image C (p) (step S6d). Let the number of counted pixels be N _C (p).

  Next, the image processing unit 12 calculates the ratio of NC (p) and ND (p) (step S7d). The ratio R (p) = ND (p) ÷ NC (p). The ratio R (p) is one value for each cardiac phase p.

  The processes in steps S2d to S7d so far are performed for all cardiac phases p (step S8d). Thus, the relationship of the ratio R (p) with respect to each cardiac phase p is obtained (step S9d).

  Hereinafter, the relationship of the ratio R (p) to the cardiac phase p is displayed as a graph as required by the application (step S10d). Further, the cardiac phase P that makes R (p) the smallest is detected, and the cardiac phase obtained in this way is output as “a stationary cardiac phase with good position reproducibility” (step S11d). For example, a three-dimensional reconstruction process is performed using the original image A (P) corresponding to the cardiac phase P thus obtained.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Specific examples of modifications are as follows.

(Modification 1)
In all of the above Examples 1 to 3, the contrasted moving images of the cardiac coronary artery have been described. Here, a method of applying the present embodiment to the non-contrast image of the cardiac coronary artery will be described.

  FIG. 13 shows an operation procedure of the image processing unit 12 according to the first modification. For example, an image in which a guide wire (hereinafter referred to as a wire) is inserted into a coronary artery as shown in FIG. In this image, a thin object with a diameter of 0.014 inch is visible. Therefore, when processing is performed as in the first to third embodiments, the wire area appears to be double even if there is a slight movement, and the wire area appears to be double even if there is a large movement. This makes it impossible to detect the degree of movement.

  Therefore, for the original image before processing, the width of the wire is increased to, for example, the thickness of a blood vessel as shown in FIG. Specifically, as shown in FIG. 13, after the original image is read, a process of “thickening process (step S <b> 2 e)” is added. By doing this, even a guide wire looks thick like a blood vessel, so that the subsequent steps can obtain a desired result by the same processing as in the first to third embodiments.

(Modification 2)
In the first modification, the case where the guide wire is inserted into the blood vessel in the non-contrast image has been described. Here, the present embodiment is extended to an image in which the guide wire or the like is not inserted into the blood vessel in the non-contrast image. The method to apply is described.

  As the target image, an image obtained by capturing the heart is used, and as shown in FIG. 15, the edge of the heart is used instead of the blood vessel. The image processing unit 12 extracts an image from the image group stored in the image data storage unit 11 based on the electrocardiogram signal and sets it as an image group A (p). The case where the image group A (p) is composed of two images will be described below.

The image processing unit 12 counts the number of pixels having a luminance value higher than a predetermined threshold value. The threshold at this time is a threshold that can distinguish a lung region from other regions using a histogram or the like. This counts the area of the lung field. Since there are a plurality of image groups A (p), the values counted in the respective images are averaged to be N _A (p). Next, create a SUB image. Since the image A (p) is an image group of 2 frames, the natural logarithm difference between the two images is taken and the SUB image is defined as D (p). Next, the number of bright pixels of the SUB image D (p) is counted according to the threshold value, and the counted number of pixels is set to N _D (p). Then, the ratio R (p) between N _A (p) and N _D (p) is calculated by the ratio R (p) = N _D (p) ÷ N _A (p).

  According to this method, when the difference between images is large, the number of bright pixels in the image D (p) increases, and thus the value of the ratio R (p) increases. When the difference between the images is small, the number of bright pixels in the image D (p) is small, and thus the value of the ratio R (p) is small. In this way, a desired result can be obtained by the same processing as described above even in a non-contrast image in which a guide wire or the like is not inserted into a blood vessel.

(Modification 3)
In Example 1, MIP images of all frames of the extracted image group C (p) were created. In the modified example, a method of taking MIP for adjacent frames (adjacent heartbeats) instead of all frames will be described.

As shown in FIG. 16, the number of pixels in each blood vessel region of B (p) of the k-th heartbeat and B (p) of the (k + 1) -th heartbeat is counted, and the larger value is defined as N _B (p). Create a MIP image of B (p) of the kth heartbeat and B (p) of the k + 1th heartbeat, set this as C (p), count the number of pixels in the blood vessel region of C (p), and calculate N _C (p). Calculate the ratio of N _B (p) to N _C (p).

  When this is calculated for all cardiac phases, one graph is shown per heartbeat. Moreover, when this is calculated for the total heart rate, a plurality of graphs are shown. As a result, data of all heart beats may be displayed as they are, an average value thereof may be obtained, or a maximum value thereof may be displayed.

(Modification 4)
In Example 1 and Example 3, after extracting one image per heartbeat for a certain cardiac phase, motion correction is performed between the extracted images. The present embodiment may be applied to a motion-corrected image group, and the phase with the smallest motion may be selected.

(Modification 5)
In Examples 1 to 3, all the areas of the image are set as calculation areas. For example, when the original image is 512 × 512, the calculation target is all 512 × 512, but the present invention is not limited to this, and the calculation may be performed on a part of the image area. For example, the calculation may be made using only 512 × 256 in the upper half of the image. For example, in the case of the heart, if the upper half of the image is used, there is a merit that the influence of the movement of the diaphragm can be reduced. Thereby, the user can calculate a cardiac phase and a stationary cardiac phase with good position reproducibility for a region of particular interest.

(Additional example 1)
Examples 1 to 3 can be calculated and displayed in substantially real time. In this method, the amount of motion of the current frame with respect to the past frame in time is calculated. Therefore, as soon as the current frame is obtained, the calculation can be started to display the result in a graph in substantially real time. As a specific example, a case applied to the first embodiment will be described below.

  As shown in FIG. 17, it is assumed that the first frame of the acquired projection image is in the vicinity of the cardiac phase 70%. It is not possible to draw a graph from the first heartbeat image yet. The processing starts at the moment when the second heartbeat is entered and an image having a heart phase of around 70% is collected. Example 1 is executed from the two images of the first heartbeat near RR70% and the second heartbeat near RR70%, and the ratio R (70) is obtained. Once obtained, plot it on a graph. As shown at 171 in FIG. 17, only a point is drawn on the graph at this point.

  Next, image collection is continued and the next frame is collected. Assume that the cardiac phase of this frame is around RR75%. In the image processing, Example 1 is executed from two images, ie, an image in the vicinity of RR75% of the first heartbeat and an image in the vicinity of RR75% of the second heartbeat, and the ratio R (75) is obtained. When it is obtained, plot it on the previous graph. As indicated by 172 in FIG. 17, at this time point, two points are plotted on the graph. Moreover, you may draw the line which connects both. By sequentially executing the above processing, the number of points plotted on the graph substantially in real time increases. If this additional example is used, for example, the surgeon can see the plot in substantially real time during the operation, and can immediately make use of it for selection of the operation policy.

(Additional example 2)
Furthermore, the accuracy of the index can be increased by excluding projection images when there is an arrhythmia or while the bed is moving. For example, in Examples 1 to 3, when it is determined that there is an arrhythmia in the electrocardiogram, no image is extracted from the heartbeat including the arrhythmia. Thereby, it is possible to evaluate excluding abnormal cases. In the first to third embodiments, when bed movement is detected in the image data, the data is processed without being used. Since the couch movement is artificial for the operator, it is preferable to remove images captured during that time. Since the bed position can be acquired from the bed moving mechanism 7 by the system control unit 9, it may be stored in association with the projection image.

(Additional example 3)
In the third embodiment, the case where the window width is fixed to a certain value has been described. As an additional example, as shown in FIG. 18, the window width may be changed (expanded) in order, and the degree of change may be displayed on a graph. In this way, it is possible to know how much the reliability of the index can be maintained when the window width is widened. In the example of FIG. 18, when the window width is widened to 33 msec, 66 msec, 99 msec, and 123 msec, it can be seen that the accuracy decreases when 123 msec is reached.

(Additional example 4)
Using the cardiac phase and stationary cardiac phase with good position reproducibility detected by the above embodiments, one image is extracted for each heartbeat, and the extracted images are averaged. This improves the image quality.

(Additional example 5)
Using the cardiac phase and stationary cardiac phase with good position reproducibility detected by the above embodiments, one image is extracted for each heartbeat, and the extracted image is MIPed. This improves the image quality. This is used particularly when it is desired to improve the blood vessel image.

Furthermore, the following alternative methods can be applied.
In Examples 1 to 3, MIP images are used as an integrated image creation method. When the image is reversed in black and white, a minimum intensity projection image (MinIP) is used. In this method, MIP or MinIP is considered to be suitable, but an average image (average), a difference image (subtraction), and an intermediate value image (median) may also be used. In some cases, average and subtraction may be better.

  As the display in Examples 1 to 3, an example is shown in which the value of the ratio R (p) with respect to the cardiac phase p is displayed in a graph. Here, as shown in FIG. 19, a method of displaying a combination of the first and second embodiments is proposed. First, the graph 191 is obtained by performing the processing of the first embodiment. Second, the graph 192 is obtained by performing the processing of the second embodiment. The monitor 13 displays a graph 191 and a graph 192 side by side. According to this display method, it is possible to check a list of “heart phases with good position periodicity” and “stationary heart phases”. Of course, the third embodiment may be combined and displayed side by side.

  In the second embodiment, the relationship between the cardiac phase p and the ratio R (p) is obtained for each heartbeat. Therefore, in the graph display, as shown in FIG. 20, a method of displaying all relationships in a graph (FIG. 20A), a method of displaying only representative values (average values) in a graph (FIG. 20B), all And a method for displaying the representative value (average value) in a graph (FIG. 20C).

  Each function according to the present embodiment can also be realized by installing a program for executing the processing in a computer such as a workstation and expanding the program on a memory. At this time, a program capable of causing the computer to execute the technique is stored in a recording medium such as a magnetic disk (floppy (registered trademark) disk, hard disk, etc.), an optical disk (CD-ROM, DVD, etc.), or a semiconductor memory. It can also be distributed.

  In the embodiment described above, the cardiovascular X-ray image is used for the description in the above embodiment, but not limited to the X-ray image, to a medical image collected by another system such as a CT image, an MRI image, or an ultrasound image. It is possible to extend For example, since the 256CT has a surface detector, if the image is collected in a fixed state without being rotated, the present embodiment can be applied as it is.

  For example, if a detector having a certain surface such as 64CT or 256CT is used, a scan image is used to capture an image from the same angle once per rotation. Collecting them and executing this embodiment will give the desired results. (Note that scano is called scan projection radiograph, topogram, scanogram, surview, pilot scan, scout view, etc. by CT manufacturers.) Since scano is almost always executed before actual imaging, If the optimal cardiac phase is calculated using and is adapted to the main imaging, the exposure dose is not increased. It becomes easy to use the latest technology such as ECG modulation.

  In addition, the electrocardiogram signal is not always essential, and the phase of another periodic biological motion (for example, respiratory motion) can be used instead of the cardiac phase.

  In the above-described embodiment, the image processing apparatus has been described as a configuration integrated with the X-ray diagnostic apparatus. However, as an image processing apparatus including the image data storage unit 11, the image processing unit 12, and the monitor 13, they are separately independent. It can also be configured.

  In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure which shows one Embodiment of the X-ray diagnostic apparatus provided with the image processing apparatus which concerns on this invention. The figure for demonstrating the positional periodicity of the heart. 6 is a flowchart illustrating a basic operation procedure of the image processing unit. The figure which shows an example of the cardiovascular image in a systole and a diastole. 3 is a flowchart illustrating an operation procedure of an image processing unit according to the first exemplary embodiment. The figure which shows the operation | movement of FIG. The figure which shows the operation | movement of FIG. 1 is a diagram illustrating a clinical example of Example 1. FIG. 9 is a flowchart illustrating an operation procedure of an image processing unit according to the second embodiment. The figure which illustrated the operation | movement of FIG. The figure which shows the clinical example of Example 2. FIG. 10 is a flowchart illustrating an operation procedure of an image processing unit according to the third embodiment. The figure which shows the operation | movement of FIG. 9 is a flowchart showing a procedure of an operation of an image processing unit in Modification 1. The figure which shows a thick line process. The figure which shows operation | movement of the modification 2. The figure which shows operation | movement of the modification 3. The figure which shows operation | movement of the additional example 1. FIG. The figure which shows an example of the graph display in the additional example 3. FIG. FIG. 6 is a diagram illustrating an example of a graph display in the first and second embodiments. FIG. 10 is a diagram illustrating an example of a graph display in the second embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... X-ray tube, 2 ... X-ray detector, 3 ... Bed, 4 ... X-ray control part, 5 ... C arm apparatus, 6 ... C arm moving mechanism, 7 ... Bed moving mechanism, 8 ... Operation part, 9 ... System control unit, 10 ... electrocardiograph, 11 ... image data storage unit, 12 ... image processing unit, 13 ... monitor.

Claims (5)

A storage unit for storing data of a plurality of projection images over a plurality of periods related to a periodically moving part;
An image generation unit that generates data of a single image based on data of a plurality of projection images corresponding to substantially the same phase among the plurality of stored projection images;
A first counting unit that counts a first number of pixels having a pixel value exceeding a predetermined threshold for the generated single image;
A second counting unit that counts a second number of pixels having a pixel value exceeding the threshold with respect to a projection image corresponding to the same phase as the generated image;
An image processing apparatus comprising: an index generation unit configured to generate an index representing movement of the part based on the first pixel number and the second pixel number. A storage unit for storing data of a plurality of projection images related to a periodically collected region that is continuously collected;
An image generation unit that generates data of a single image based on data of a plurality of projection images with continuous collection times among the plurality of stored projection images;
A first counting unit that counts a first number of pixels having a pixel value exceeding a predetermined threshold for the generated single image;
A second counting unit that counts a second number of pixels having a pixel value exceeding the threshold for a projection image corresponding to the same collection time as the generated image;
An image processing apparatus comprising: an index generation unit configured to generate an index representing movement of the part based on the first pixel number and the second pixel number. A storage unit for storing data of a plurality of projection images over a plurality of periods related to a periodically moving part;
An image generation unit that generates data of a single image based on data of a plurality of projection images whose collection times are discrete according to the heartbeat period among the plurality of stored projection images;
A first counting unit that counts a first number of pixels having a pixel value exceeding a predetermined threshold for the generated single image;
A second counting unit that counts a second number of pixels having a pixel value exceeding the threshold for a projection image corresponding to the same time as the generated image;
An image processing apparatus comprising: an index generation unit configured to generate an index representing the motion of the heart based on the first pixel number and the second pixel number.   The image processing apparatus according to claim 1, wherein the index is a ratio between the first pixel number and the second pixel number.   The image processing apparatus according to claim 1, further comprising a display unit that displays a relationship between the generated index and phase in a graph.

Images