JP5556413B2 - Dynamic image processing apparatus and program - Google Patents

Description

The present invention relates to a dynamic state image processing apparatus and a program.

  In contrast to the conventional still image and diagnosis of radiation using a film / screen or photostimulable phosphor plate, a dynamic image of the region to be examined is taken using a semiconductor image sensor such as an FPD (flat panel detector), Attempts have been made to apply it to diagnosis. Specifically, by utilizing the responsiveness of reading / erasing of image data of the semiconductor image sensor, pulsed radiation is continuously irradiated from the radiation source in accordance with the reading / erasing timing of the semiconductor image sensor. Take multiple shots per second to capture the dynamics of the area to be examined. By sequentially displaying a series of a plurality of images acquired by imaging, a doctor can recognize a series of movements of a region to be examined.

  Various techniques for displaying dynamic images in an easy-to-view manner have also been proposed. For example, Patent Document 1 describes a technique for generating a difference image indicating a difference in pixel values between a plurality of frame images constituting a dynamic image and sequentially switching and displaying the generated difference images.

  Patent Document 2 describes a technique for performing imaging using radiation of a plurality of different energies in order to reduce the image component of the bone portion reflected in the lung field dynamic image.

JP 2004-31434 A JP 2003-298939 A

  According to the technique described in Patent Literature 1, it is possible to extract a signal change in the lung field at each timing during breathing. However, the signal change is a mixture of the signal change caused by the density change of the alveoli due to the expansion and contraction of the lung field and the signal change due to the movement of the structure in the lung field, and is represented by the former signal change. It was difficult to detect the local ventilation status in the lung field.

  For example, during inspiration, the lung field expands and the density of tissue in the lung field such as the alveoli decreases, so that the amount of radiation (X-ray) transmission increases and the signal value in the lung field in the chest dynamic image increases. On the other hand, during exhalation, the lung field shrinks and the density of tissue in the lung field such as the alveoli increases, so that the amount of radiation transmission decreases and the signal value in the lung field of the chest dynamic image decreases. Usually, the ribs and clavicles move upward during inspiration and move downward during expiration. From these behaviors, in the difference image between frames, the signal change due to the movement of the ribs and clavicles is superimposed on the density change of the lung field tissue, and the signal at the lower edge of the ribs and clavicles against the signal change due to the density change of the lung field tissue The change is emphasized, and the signal change is reversed at the upper edge of the rib / clavicle. The signal change due to the movement of these structures hinders the detection and diagnosis of the local ventilation state represented by the density change of the lung tissue.

  Further, the technique described in Patent Document 2 requires a complicated mechanism such as switching the tube voltage alternately, which increases the cost of the photographing apparatus.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a chest dynamic image that allows easy observation of changes in density of lung tissue without removing signal changes due to movement of structures such as bones without using a complicated apparatus configuration. That is.

In order to solve the above-described problem, a dynamic image processing apparatus according to claim 1 is provided.
A structure extraction means for extracting a structure region indicating a predetermined structure from each of a plurality of frame images indicating the dynamics of the chest;
A lung that extracts a lung field region from each of the plurality of frame images and uses the region other than the structure region in the extracted lung field region to perform alignment of the lung field region between the plurality of frame images. Field alignment means;
In the image after alignment of the lung field region, a structure movement amount calculation means for calculating the movement amount of the structure between adjacent frame images;
An inter-frame difference image generating means for generating an inter-frame difference image by taking a difference of signal values of corresponding pixels between temporally adjacent frame images after the lung field alignment;
Signal change amount estimation for estimating a signal change amount due to movement of the structure by generating a difference image between the image obtained by moving the structure region by the movement amount of the structure and the original structure region Means,
When the estimated signal change amount exceeds a predetermined threshold, the signal value of the region corresponding to the extracted structure region in the inter-frame difference image is replaced with the signal value of surrounding pixels, Alternatively, correction means for correcting by subtracting the estimated value of the signal change amount due to the movement of the structure ,
Is provided.

The invention according to claim 2 is the invention according to claim 1,
The apparatus further comprises means for reducing a spatial signal change of the extracted structure region in the plurality of frame images.

The invention according to claim 3 is the invention according to claim 1 or 2,
Display means for displaying the corrected inter-frame difference image as a moving image or a still image.

The invention according to claim 4 is the invention according to claim 3,
A region where the sign of the signal value of the surroundings is reversed is extracted from the corrected inter-frame difference image, and the respiratory function of the lung field region is based on the ratio of the extracted region to the lung field region. A determination means for determining whether or not it is normal;
The display means also displays the determination result by the determination means.

The program of the invention described in claim 5 is:
Computer
A structure extraction means for extracting a structure region indicating a predetermined structure from each of a plurality of frame images indicating the dynamics of the chest;
A lung that extracts a lung field region from each of the plurality of frame images and uses the region other than the structure region in the extracted lung field region to perform alignment of the lung field region between the plurality of frame images. Field alignment means,
A structure movement amount calculating means for calculating a movement amount of the structure between adjacent frame images in the image after alignment of the lung field region;
An inter-frame difference image generating means for generating an inter-frame difference image by taking a difference between signal values of corresponding pixels between temporally adjacent frame images after the lung field alignment;
Signal change amount estimation for estimating a signal change amount due to movement of the structure by generating a difference image between the image obtained by moving the structure region by the movement amount of the structure and the original structure region means,
When the estimated signal change amount exceeds a predetermined threshold, the signal value of the region corresponding to the extracted structure region in the inter-frame difference image is replaced with the signal value of surrounding pixels, Or correction means for correcting by subtracting the estimated value of the signal change amount due to the movement of the structure ,
To function as.

  According to the present invention, it is possible to provide a chest dynamic image that makes it easy to observe changes in the density of lung field tissue, from which signal changes due to movement of structures such as bones have been removed, without using a complicated device configuration. .

It is a figure which shows the whole structure of the dynamic image diagnosis assistance system in embodiment of this invention. 3 is a flowchart illustrating a shooting control process executed by a control unit of the shooting console of FIG. 1. It is a flowchart which shows the image analysis process performed by the control part of the diagnostic console of FIG. It is a figure for demonstrating the process of estimation of the signal variation | change_quantity by the movement of the structure in step S15 of FIG. It is a figure for demonstrating the determination method of whether the signal value correction | amendment of a structure moving area | region is performed. (A) is a figure which shows the inter-frame difference image before signal value correction | amendment of a structure movement area | region, (b) is a figure which shows the inter-frame difference image after signal value correction | amendment of a structure movement area | region. It is a flowchart which shows the image analysis process B performed by the control part of the diagnostic console of FIG. 1 in 2nd Embodiment.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

[Configuration of Dynamic Image Diagnosis Support System 100]
First, the configuration will be described.
FIG. 1 shows the overall configuration of a dynamic image diagnosis support system 100 in the present embodiment.
As shown in FIG. 1, in the dynamic image diagnosis support system 100, an imaging device 1 and an imaging console 2 are connected by a communication cable or the like, and the imaging console 2 and the diagnostic console 3 are connected to a LAN (Local Area Network). ) Or the like via a communication network NT. Each device constituting the dynamic image diagnosis support system 100 conforms to the DICOM (Digital Image and Communications in Medicine) standard, and communication between the devices is performed according to DICOM.

[Configuration of the photographing apparatus 1]
The imaging apparatus 1 is an apparatus that images the dynamics of the chest with periodicity (cycle), such as pulmonary expansion and contraction morphological changes, heart pulsation, and the like accompanying respiratory motion. Dynamic imaging is performed by continuously irradiating a human chest with radiation such as X-rays to acquire a plurality of images (that is, continuous imaging). A series of images obtained by this continuous shooting is called a dynamic image. Each of the plurality of images constituting the dynamic image is called a frame image.
As shown in FIG. 1, the imaging apparatus 1 includes a radiation source 11, a radiation irradiation control device 12, a radiation detection unit 13, a reading control device 14, and the like.

The radiation source 11 is disposed at a position facing the radiation detection unit 13 across the subject M, and irradiates the subject M with radiation (X-rays) according to the control of the radiation irradiation control device 12.
The radiation irradiation control device 12 is connected to the imaging console 2 and controls the radiation source 11 based on the radiation irradiation conditions input from the imaging console 2 to perform radiation imaging. The radiation irradiation conditions input from the imaging console 2 are, for example, pulse rate, pulse width, pulse interval, imaging start / end timing, X-ray tube current value, X-ray tube voltage value, filter type during continuous irradiation. Etc. The pulse rate is the number of times of radiation irradiation per second, and matches the frame rate described later. The pulse width is a radiation irradiation time per one irradiation. The pulse interval is the time from the start of one radiation irradiation to the start of the next radiation irradiation in continuous imaging, and coincides with a frame interval described later.

  The radiation detection unit 13 is configured by a semiconductor image sensor such as an FPD. The FPD has, for example, a glass substrate or the like, detects radiation that has been irradiated from the radiation source 11 and transmitted through at least the subject M at a predetermined position on the substrate according to its intensity, and detects the detected radiation as an electrical signal. A plurality of pixels to be converted and stored are arranged in a matrix. Each pixel includes a switching unit such as a TFT (Thin Film Transistor).

  The reading control device 14 is connected to the imaging console 2. The reading control device 14 controls the switching unit of each pixel of the radiation detection unit 13 based on the image reading condition input from the imaging console 2 to switch the reading of the electrical signal accumulated in each pixel. Then, the image data is acquired by reading the electrical signal accumulated in the radiation detection unit 13. This image data is a frame image. Then, the reading control device 14 outputs the acquired frame image to the photographing console 2. The image reading conditions are, for example, a frame rate, a frame interval, a pixel size, an image size (matrix size), and the like. The frame rate is the number of frame images acquired per second and matches the pulse rate. The frame interval is the time from the start of one frame image acquisition operation to the start of the next frame image acquisition operation in continuous shooting, and coincides with the pulse interval.

  Here, the radiation irradiation control device 12 and the reading control device 14 are connected to each other, and exchange synchronization signals to synchronize the radiation irradiation operation and the image reading operation.

[Configuration of the shooting console 2]
The imaging console 2 outputs radiation irradiation conditions and image reading conditions to the imaging apparatus 1 to control radiation imaging and radiographic image reading operations by the imaging apparatus 1, and also captures dynamic images acquired by the imaging apparatus 1. Displayed for confirmation of whether the image is suitable for confirmation of positioning or diagnosis.
As shown in FIG. 1, the imaging console 2 includes a control unit 21, a storage unit 22, an operation unit 23, a display unit 24, and a communication unit 25, and each unit is connected by a bus 26.

The control unit 21 includes a CPU (Central Processing Unit) and a RAM (Random Access Memory).
) Etc. The CPU of the control unit 21 reads the system program and various processing programs stored in the storage unit 22 in accordance with the operation of the operation unit 23, expands them in the RAM, and performs shooting control processing described later according to the expanded programs. Various processes including the beginning are executed to centrally control the operation of each part of the imaging console 2 and the radiation irradiation operation and the reading operation of the imaging apparatus 1.

  The storage unit 22 is configured by a nonvolatile semiconductor memory, a hard disk, or the like. The storage unit 22 stores various programs executed by the control unit 21 and data such as parameters necessary for execution of processing by the programs or processing results. For example, the storage unit 22 stores a shooting control processing program for executing the shooting control process shown in FIG. In addition, the storage unit 22 stores radiation irradiation conditions and image reading conditions in association with the examination target region. Various programs are stored in the form of readable program code, and the control unit 21 sequentially executes operations according to the program code.

  The operation unit 23 includes a keyboard having a cursor key, numeric input keys, various function keys, and the like, and a pointing device such as a mouse. The control unit 23 controls an instruction signal input by key operation or mouse operation on the keyboard. To 21. In addition, the operation unit 23 may include a touch panel on the display screen of the display unit 24. In this case, the operation unit 23 outputs an instruction signal input via the touch panel to the control unit 21.

  The display unit 24 is configured by a monitor such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube), and displays an input instruction, data, or the like from the operation unit 23 in accordance with an instruction of a display signal input from the control unit 21. To do.

  The communication unit 25 includes a LAN adapter, a modem, a TA (Terminal Adapter), and the like, and controls data transmission / reception with each device connected to the communication network NT.

[Configuration of diagnostic console 3]
Diagnostic console 3 obtains the dynamic image from the imaging console 2, a dynamic state image processing device for the physician to image diagnosis by displaying the acquired dynamic image.
As shown in FIG. 1, the diagnostic console 3 includes a control unit 31, a storage unit 32, an operation unit 33, a display unit 34, and a communication unit 35, and each unit is connected by a bus 36.

  The control unit 31 includes a CPU, a RAM, and the like. The CPU of the control unit 31 reads out the system program and various processing programs stored in the storage unit 32 in accordance with the operation of the operation unit 33 and expands them in the RAM, and performs image analysis described later according to the expanded programs. Various processes including the process are executed to centrally control the operation of each part of the diagnostic console 3. The control unit 31 functions as a structure extraction unit, a lung field alignment unit, an inter-frame difference image generation unit, a signal change amount estimation unit, a correction unit, and a determination unit by executing image analysis processing.

  The storage unit 32 is configured by a nonvolatile semiconductor memory, a hard disk, or the like. The storage unit 32 stores data such as parameters necessary for execution of processing or data such as processing results by various programs and programs including an image analysis processing program for executing image analysis processing by the control unit 31. These various programs are stored in the form of readable program codes, and the control unit 31 sequentially executes operations according to the program codes.

  The operation unit 33 includes a keyboard having cursor keys, numeric input keys, various function keys, and the like, and a pointing device such as a mouse. The control unit 33 controls an instruction signal input by key operation or mouse operation on the keyboard. To 31. The operation unit 33 may include a touch panel on the display screen of the display unit 34, and in this case, an instruction signal input via the touch panel is output to the control unit 31.

  The display unit 34 as a display unit is configured by a monitor such as an LCD or a CRT, and displays an input instruction, data, or the like from the operation unit 33 in accordance with an instruction of a display signal input from the control unit 31.

  The communication unit 35 includes a LAN adapter, a modem, a TA, and the like, and controls data transmission / reception with each device connected to the communication network NT.

[Operation of Dynamic Image Diagnosis Support System 100]
Next, the operation in the dynamic image diagnosis support system 100 will be described.

(Operation of the photographing apparatus 1 and the photographing console 2)
First, the photographing operation by the photographing apparatus 1 and the photographing console 2 will be described.
FIG. 2 shows photographing control processing executed in the control unit 21 of the photographing console 2. The photographing control process is executed in cooperation with the photographing control processing program stored in the control unit 21 and the storage unit 22.

  First, the operation unit 23 of the imaging console 2 is operated by the imaging engineer, and patient information (patient name, height, weight, age, sex, etc.) of the imaging target (subject M) is input (step S1).

  Next, the radiation irradiation conditions are read from the storage unit 22 and set in the radiation irradiation control device 12, and the image reading conditions are read from the storage unit 22 and set in the reading control device 14 (step S2).

  Next, a radiation irradiation instruction by the operation of the operation unit 23 is waited (step S3). During this time, the radiographer positions the patient. Specifically, the subject M is arranged so that the chest front (or back) of the subject M faces the radiation source 11. When the positioning is completed, the imaging technician operates the operation unit 23 to instruct radiation irradiation.

  When a radiation irradiation instruction is input by the operation unit 23 (step S3; YES), a photographing start instruction is output to the radiation irradiation control device 12 and the reading control device 14, and dynamic photographing is started (step S4). That is, radiation is emitted from the radiation source 11 at a pulse interval set in the radiation irradiation control device 12, and a frame image is acquired by the radiation detection unit 13. When a predetermined time has elapsed from the start of dynamic imaging, the control unit 21 outputs an instruction to end imaging to the radiation irradiation control device 12 and the reading control device 14, and the imaging operation is stopped.

  Frame images acquired by shooting are sequentially input to the shooting console 2, stored in the storage unit 22 in association with numbers indicating the shooting order (step S5), and displayed on the display unit 24 (step S6). . The imaging engineer confirms the positioning and the like based on the displayed dynamic image, and determines whether an image suitable for diagnosis is acquired by imaging (imaging OK) or re-imaging is necessary (imaging NG). Then, the operation unit 23 is operated to input a determination result.

  When a determination result indicating photographing OK is input by a predetermined operation of the operation unit 23 (step S7; YES), an identification ID for identifying a dynamic image or each of a series of frame images acquired by dynamic photographing is displayed. Information such as patient information, examination target region, radiation irradiation condition, image reading condition, number indicating the imaging order is attached (for example, written in the header area of the image data in DICOM format) and diagnosed via the communication unit 25 Is transmitted to the console 3 (step S8). Then, this process ends. On the other hand, when a determination result indicating photographing NG is input by a predetermined operation of the operation unit 23 (step S7; NO), a series of frame images stored in the storage unit 22 is deleted (step S9), and this processing is performed. finish.

(Operation of diagnostic console 3)
Next, the operation in the diagnostic console 3 will be described.
When the diagnostic console 3 receives a series of frame images of the dynamic image from the imaging console 2 via the communication unit 35, it cooperates with the control unit 31 and the image analysis processing program stored in the storage unit 32. As a result, the image analysis processing shown in FIG. 3 is executed.

  Here, not only the lung field but also structures such as bones (clavicle, ribs, scapula, etc.), heart wall, diaphragm, etc. are reflected in the dynamic image obtained by photographing the front of the chest. When these structures move due to breathing motion or the like, the signal value of the image changes due to the movement. However, changes in signal values (signal changes) due to the movement of these structures hinder the detection and diagnosis of ventilation states represented by changes in the density of lung tissue. Therefore, in the image analysis process, a signal change due to the movement of the structure is estimated from the dynamic image, the influence is removed, and the quality of the display and the respiratory function is determined.

In the image analysis process, first, a structure extraction process is executed, and a structure area is extracted from each frame image (step S11).
In the following description, an example in which the structure is a clavicle and a rib (referred to as clavicle / rib) will be described. Extraction of the clavicle / rib as a structure can be performed by, for example, a method using edge extraction, a method using multiresolution decomposition and edge enhancement, a method using a neural network learned from an energy subtraction image, or the like.

  In the method based on edge extraction, as described in publicly known document 1, first, an edge image is generated for each frame image by using an edge extraction filter such as a Robinson operator, and an arc shape is detected from the edge image. The rib shape is detected by finding an arc-shaped line that seems to be a rib using, for example. Also, a clavicle shape is detected by finding a straight portion that seems to be a clavicle using a Hough transform that detects a straight line. Based on the detected clavicle / rib shape, the clavicle / rib region is identified (Publication 1: “Edge extraction of main shadow of chest X-ray image using Hough transform and line shape”) Journal D-II Vol.J77-D-II No.7 pp1375-1381).

  In the technique based on multi-resolution decomposition and edge enhancement, as described in the known document 2, first, each frame image is decomposed into resolution levels by multi-resolution decomposition, and edge components in horizontal / vertical / diagonal directions are obtained for each resolution level. Generate an image. Then, a portion exceeding a predetermined threshold in the horizontal component image of a predetermined resolution level is detected as a clavicle / rib shape, and a clavicle / rib region is specified based on the detected clavicle / rib shape. For each resolution level, an image that selectively enhances the circular / linear pattern is created by calculating the maximum eigenvalue of the Hessian matrix, and the circular / linear pattern-enhanced image having a predetermined resolution level is generated as a clavicle / rib. It can also be detected as a shape. (Refer to publicly known document 2: “Construction of a filter bank for detecting circular and linear patterns in medical images”, IEICE Transactions D-II Vol. J87-D-II No. 1 pp175-185).

  In the method using the neural network learned from the energy subtraction image, as described in the known document 3, the chest image acquired in advance and the bone image extracted by energy subtraction corresponding to this chest image (only the clavicle / rib) A database of a plurality of pairs with extracted images) is learned in advance using a neural network as teacher data. The chest image of each frame is input to the learned neural network, and the clavicle / rib region is specified based on the obtained bone image of the output (refer to Japanese Unexamined Patent Application Publication No. 2005-20338).

Next, alignment in the lung field region between the frame images is performed (step S12).
In step S12, alignment in the lung field region is performed by local matching processing and warping processing.

In the local matching process, first, a lung field region is extracted from an arbitrary frame image in a series of frame images (here, the imaging order is the first frame image, referred to as a reference image). A region other than the clavicle / rib region extracted by the structure extraction process is divided into small regions of 0.4 to 0.6 cm in the vertical direction and 0.4 to 2 cm in the horizontal direction. Note that the lung field region extraction method may be any method. For example, a threshold value is obtained by discriminant analysis from a histogram of signal values of each pixel of the reference image, and a region having a signal higher than this threshold value is first extracted as a lung field region candidate. Next, edge detection is performed in the vicinity of the boundary of the first extracted lung field region candidate, and the boundary of the lung field region can be extracted by extracting along the boundary the point where the edge is maximum in a small region near the boundary. it can.
Next, P1 is a frame image having the first shooting order, and P2 is a frame image adjacent to the frame image (a frame image having a shooting order is adjacent (that is, a temporally adjacent frame image; the same applies hereinafter)). A search area for each small area of P1 is set. Here, the search area of P2 has the same center point (x, y) and the horizontal and vertical widths are larger than those of the small area of P1, where the coordinates of the center point in each small area are (x, y). (For example, 1.5 times). Then, for each area of P1, a position having the highest matching degree in the search range of P2 is obtained, thereby calculating a corresponding position on P2 for each of the small areas of P1. As the matching degree, the least square method or the cross correlation coefficient is used as an index.
Next, P2 is newly regarded as P1, and the next frame image whose shooting order is P2 is regarded as new P2, and the corresponding position of P2 in each small region of P1 is calculated. By repeating the above processing, it is possible to determine which position in each adjacent frame image each small region of each frame image corresponds to. The obtained processing result is stored in the RAM of the control unit 31.

Note that the local matching process may be performed on the frame image itself, or may be performed on an image extracted (emphasized) by a gradient filter or the like.
Furthermore, local matching processing may be performed on an image in which lung blood vessel shadows are emphasized or extracted. As a technique for emphasizing pulmonary blood vessel shadows, as described in the above-mentioned well-known document 2, resolution corresponding to pulmonary blood vessels from an image obtained by selectively emphasizing a circular / linear pattern for each resolution level after multi-resolution decomposition. By extracting the level image, an image in which the lung blood vessel shadow is enhanced can be obtained. Further, as described in, for example, publicly known document 4, a tree-like figure model that can be deformed such as stretching, merging, and dividing in consideration of the shape of the blood vessel shadow is used as a model of the blood vessel structure. Pulmonary blood vessel shadows can be extracted by using a method for extracting a morphological structure (Prior Art 4: “Automatic extraction procedure of blood vessel shadows from chest X-ray images using Deformable Model” MEDICAL IMAGING TECHNOLOGY Vol.17 No. 5, see September 1999). At this time, the division of the small region may be performed by dividing the reference image at equal intervals or by dividing the reference image into rectangular regions having a central characteristic point such as an extracted pulmonary blood vessel branch point.

Next, a warping process is performed. Specifically, P1 is the frame image with the first shooting order, and P2 is the frame image adjacent to the shooting order, and the corresponding position of each small region between the adjacent frame images calculated by the local matching process is set. Based on this, a shift vector from P1 to P2 is calculated for each small region. Next, the calculated shift vector is fitted with a polynomial, and the shift vector of each pixel in each small region is calculated using this polynomial. Then, warping processing is performed based on the calculated shift vector of each pixel, and the position of each pixel in each small area of P2 is shifted to the position of the corresponding pixel in the frame image of P1. Next, the warping process P2 is newly regarded as P1, and the next frame image whose shooting order is P2 is regarded as a new P2, and the above process is performed. By sequentially repeating the above processing from adjacent frame images in the early shooting order, the positions of the small areas of all the frame images can be made to substantially coincide with the reference image.
In addition, since the clavicle / rib region moves differently from the lung field region, it is excluded from the objects of local matching and warping as described above.

Next, returning to FIG. 3, the moving amount of the structure is calculated (step S13).
For example, in the reference image after the warping process, the clavicle / rib region of the reference image calculated in step S11 is divided into several small regions, for example, one piece or one piece is further divided into a plurality of pieces. For each small region, for example, the corresponding position between adjacent frame images is calculated using the local matching process described above. Then, based on the calculated corresponding position, a shift vector representing how much and in which direction the frame images have moved is calculated for each small region in the clavicle / rib region. This shift vector is the amount of movement of the structure. The corresponding position and shift vector of each small area are stored in the RAM of the control unit 31.

  Next, an inter-frame difference that takes a signal value difference in pixel units between adjacent frame images after the warping process is performed, and an inter-frame difference image is generated (step S14). A signal change (increase / decrease or change in signal value) between frame images can be obtained by the inter-frame difference image.

Next, the signal change amount due to the movement of the structure is estimated (step S15).
For example, when the frame images adjacent to each other after the warping processing are the frame N and the frame N + 1, as shown in FIG. 4, each small region obtained by dividing the clavicle / rib region of the frame N is calculated in step S13. A frame N + 1 ′ shifted by the shift vector is generated, and the signal value of the corresponding pixel in frame N is subtracted from the signal value of each pixel in frame N + 1 ′. This difference value can be regarded as an estimated value of the signal change amount due to the movement of the structure. For example, an area with a difference value of 0 can be estimated as an area where there is no movement of a structure, and an area where the difference value is greater than a predetermined threshold can be estimated as an area where the structure has moved. . When the difference value is larger than 0 and smaller than the threshold value, there is a movement of the structure, but the signal change amount is small, and the influence is small enough to be ignored, or the possibility of noise is large. Here, the threshold value is a value obtained experimentally and empirically.

Next, signal value correction of the structure moving area is performed (step S16). Here, first, in each pixel in the small region obtained by dividing the clavicle / rib region, the signal change amount calculated in step S15 is compared with a predetermined threshold value. As shown in FIG. 5, when the calculated signal change amount exceeds a predetermined threshold value, the signal value of the pixel in the corresponding region of the inter-frame difference image is replaced with the signal value of the surrounding pixels. For example, with respect to a block of N pixels × N pixels (N is an odd number, for example, 5, 11, etc.) centered on the pixel to be replaced, the average of the pixels excluding the pixels to be replaced therein A value is obtained, and the signal value of the central pixel is replaced with the obtained average value. Replacement is performed from the pixel whose replacement target pixel is a total of a predetermined number or less in the block centering on the replacement target pixel, and then the replacement is sequentially repeated until all the replacement target pixels are replaced.
Alternatively, the signal change due to the movement of the structure is corrected by subtracting the estimated value of the signal change amount due to the movement of the structure (taking the difference) from the inter-frame difference image.
The inter-frame difference image after correction is divided into small blocks of S pixels × S pixels (S is any one of 1 to 20) in order to remove the influence of noise, and an average value is obtained for each small block. The signal values of the pixels in the block may be replaced with average values.

  FIG. 6A shows an example of an inter-frame image before signal value correction. In FIG. 6A, a region indicated by dark shading indicates a region where the signal change (the sign of the difference value) is reversed from the surroundings. Of the regions where the signal changes are reversed from the surroundings, the regions R1 and R2 are regions where the signal changes due to the movement of the clavicle are superimposed. Thus, when signal changes that are not caused by density changes in the lung field tissue are mixed in the inter-frame difference image, it becomes an obstacle to detection and diagnosis of the local abnormal ventilation state represented by the density change in the lung field tissue. . Therefore, by the processing in steps S11 to S16, the signal change region such as R1, R2 due to the movement of the structure is specified, and the signal value in the region is corrected so as to be substantially equal to the surroundings. As a result, as shown in FIG. 6B, it is possible to provide the doctor with an image that can easily grasp the local abnormal ventilation state represented by the density change in the lung tissue.

When the correction of the signal value is completed, the diagnosis support information is displayed on the display unit 34 based on the inter-frame difference image in which the signal change due to the movement of the structure is corrected (step S17).
In step S17, as diagnosis support information, for example, a region where the signal value is negative (region where the signal value decreases between frames) in the inter-frame difference image after correction of the signal change due to the movement of the structure is predetermined. A moving image is displayed in which the region where the signal value is positive (the region where the signal value increases between frames) is displayed in a different color (for example, green). Further, the display color is adjusted so that the saturation increases as the absolute value of the signal value increases.

In a healthy person without a disease, the tissue density in the lung field increases during exhalation, so that the amount of X-ray transmission decreases and the signal value decreases. Therefore, the lung field is displayed in orange. Further, during inspiration, the density in the lung field decreases, so the amount of X-ray transmission increases and the signal value increases. Therefore, the lung field is displayed in green.
On the other hand, in a patient with a disease such as emphysema, the signal change (sign of difference value) with the surroundings is reversed in a portion where a cyst is present or a portion where emphysema is strong. Therefore, when the above display is performed, a green region is displayed during expiration, and an orange region is displayed during inspiration. That is, the display is as shown in FIG.

In this way, by observing a moving image colored based on the inter-frame difference image, the doctor can detect the disease from the size of the region where the signal change (the sign of the difference value) is reversed from the surrounding lung field region, For example, the progress of pulmonary emphysema can be grasped, and information such as the speed of breathing, the ratio of expiration time to inspiration time, and the timing of signal change switching between upper and lower lung fields can be simultaneously displayed. It can be found from the moving image, and the accuracy of diagnosis can be further improved. In particular, since the signal displayed by the movement of the structure is removed from the image displayed in step S17 as described above, the doctor can easily recognize the local abnormal ventilation state represented by the density change in the lung field tissue. Can grasp.
Note that the moving images of the original images that are not colored may be displayed in parallel with the reproduction timing synchronized so that the movement of the diaphragm or the like can be easily grasped.

  Further, in the above-described warping process, the entire frame image is not matched with the reference image, and warping is performed only between adjacent frames. Between the warped adjacent frame images, the structure movement amount calculation, the frame is performed as described above. Image created by performing difference image creation, signal change estimation due to structure movement, signal value correction of structure movement region, and coloring based on signal value (difference signal value) of each pixel of inter-frame difference image after this correction May be overlaid on each frame image of the original image before warping and displayed as a moving image.

  Moreover, it may replace with the said moving image display, and may display the still image which colored the frame image of the predetermined timing on the said reference with the said moving image display. Alternatively, an image obtained by taking the AND and OR of the signal change inversion region for all frame images may be generated and displayed as a still image. By displaying still images in this way, doctors can grasp the medical condition in a short time without being constrained to stare at the images continuously during playback as in the case of moving images, improving diagnostic efficiency. Can be made.

  Further, in step S17, not only the still image but also the following analysis and determination may be performed, and the result may be displayed side by side with the still image. That is, in the still image to be displayed, the signal change inversion region is extracted, the ratio of the signal change inversion region to the lung field region (= signal change inversion region / lung field region [%]) is calculated, and the calculation result is converted into a still image. You may display in parallel. Further, the ratio of the signal change inversion region is compared with a predetermined threshold, and based on whether or not the predetermined threshold is exceeded, it is determined whether the respiratory function in the lung field region is normal or abnormal, and the determination result is It may be displayed together. In the case of abnormalities, for example, classification and evaluation are performed in five stages of pulmonary emphysema severity I to IV according to the degree of deviation from the threshold and abnormal location (position, distribution, shape), etc., and the results of the evaluation are stationary. The image may be displayed side by side with the image. In addition, when displaying a moving image, the above analysis and determination are performed using a frame image at a predetermined timing or an image obtained by ANDing or ORing a signal change inversion region with respect to all frame images, and the determination result is obtained. It is good also as displaying together with a moving image.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.
Since the configuration of the second embodiment is the same as that described with reference to FIG. 1 in the first embodiment, the description is incorporated herein. In the second embodiment, since the contents of the image analysis process in the diagnostic console 3 are different from those in the first embodiment, the image analysis process will be described below.

  When the diagnostic console 3 receives a series of frame images of the dynamic image from the imaging console 2 via the communication unit 35, it cooperates with the control unit 31 and the image analysis processing program stored in the storage unit 32. Accordingly, the image analysis process (referred to as image analysis process B) shown in FIG. 7 is executed.

  In the image analysis process B, as shown in FIG. 7, the structure of step S24 as means for reducing the spatial signal change of the extracted structure region is compared with the image analysis process described in the first embodiment. Material attenuation processing is added.

  In the image analysis process B, first, the processes of steps S21 to S23 in FIG. 7 are executed. Since the process of step S21-step S23 is the same as that of what was demonstrated by step S11-step S13 of FIG. 3, description is used.

Next, a structure attenuation process for attenuating a spatial signal change caused by the structure extracted in step S21 is executed from each frame image after warping (step S24).
In the structure attenuation process, for example, as described in the above-mentioned publicly known document 2, an image in which the signal change of the bone part is reduced by attenuating (reducing) the horizontal edge component corresponding to the clavicle / rib. Generate. Specifically, it is possible to generate an image from which shadows due to the clavicle / rib are removed by reconstructing the horizontal edge component value extracted by multi-resolution decomposition as zero.
In addition, as described in the above-mentioned known document 3, an image obtained by removing only the bone portion (clavicle / rib) obtained by the neural network is subtracted from the original image to generate an image in which the shadow of the bone portion is removed. can do. At this time, alignment and warping in the lung field may be performed after the structure attenuation processing using this neural network.

  Next, interframe difference processing is performed between adjacent frames after the structure attenuation processing (step S25). Next, a signal change amount due to the movement of the structure is estimated (step S26). The process of step S26 is the same process as step S15 of FIG.

  Next, the moving region of the structure is corrected (step S27). Here, the signal change amount estimated in step S26 exceeds the predetermined threshold, and the signal value of the pixel in the region where the signal value (absolute value) of the inter-frame difference image exceeds the predetermined threshold is further calculated. Replace with signal values of peripheral pixels. The specific method for replacing the signal value is the same as that described in step S16 in FIG.

  Then, the diagnosis support information is displayed on the display unit 34 based on the inter-frame difference image in which the signal change amount due to the movement of the structure is corrected (step S28). The display mode of the diagnosis support information is the same as that described in step S17 in FIG.

  In the second embodiment, the spatial signal change due to the structure is reduced in advance, but in both the first embodiment and the second embodiment, the movement of the structure is performed. Thus, it is possible to provide diagnosis support information that allows the doctor to easily grasp the local abnormal ventilation state represented by the density change in the lung tissue, from which the signal change due to the above has been removed.

  As described above, according to the diagnostic console 3, the control unit 31 extracts a structure region indicating a predetermined structure from each of a plurality of frame images indicating the dynamics of the chest, and the above-described adjacent frame images are described above. Based on the extracted signal value in the structure area, the signal change amount due to the movement of the structure between the frames is estimated. In addition, a lung field region is extracted from each of the plurality of frame images, the lung field region is aligned between the plurality of frame images, and the difference between the signal values of the corresponding pixels between temporally adjacent frame images is obtained. Thus, an inter-frame difference image is generated. When the estimated signal change amount between frames exceeds a predetermined threshold value, the signal value of the region corresponding to the extracted structure region in the inter-frame difference image is corrected, and the corrected frame The difference image is displayed on the display unit 34 as a moving image or a still image.

  Accordingly, it is possible to provide a doctor with a chest dynamic image that allows easy observation of changes in the density of lung field tissue in which signal changes due to movement of structures such as bones are removed by image processing without using a complicated apparatus configuration. it can. As a result, it is possible to improve diagnostic efficiency and diagnostic accuracy.

  Further, a region where the sign of the signal value with the surroundings is reversed from the corrected inter-frame difference image, and the respiratory function of the lung field region based on the ratio of the extracted region to the lung field region By determining whether or not is normal and displaying the determination result on the display unit 34, it is possible to provide the doctor with more useful information for diagnosis.

In addition, the description content in the said embodiment is a suitable example of this invention, and is not limited to this.
For example, in the above embodiment, the case where the clavicle / rib is a structure has been described as an example, but the present invention is not limited to this.
In addition, for example, in the above-described form, an example is described in which an inter-frame difference image is generated between adjacent frames. However, the inter-frame difference image is generated not only between adjacent frames but also between two frames separated by a plurality of frames. The above-described processing after the structure movement amount calculation may be performed between two frames separated by a plurality of frames.

For example, in the above description, an example in which a hard disk, a semiconductor non-volatile memory, or the like is used as a computer-readable medium of the program according to the present invention is disclosed, but the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. Further, a carrier wave is also applied as a medium for providing program data according to the present invention via a communication line.

  In addition, the detailed configuration and detailed operation of each device constituting the dynamic image diagnosis support system 100 can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 Dynamic image diagnosis support system 1 Imaging device 11 Radiation source 12 Radiation irradiation control device 13 Radiation detection part 14 Reading control device 2 Imaging console 21 Control part 22 Storage part 23 Operation part 24 Display part 25 Communication part 26 Bus 3 Diagnosis console 31 Control Unit 32 Storage Unit 33 Operation Unit 34 Display Unit 35 Communication Unit 36 Bus

Claims (5)

A structure extraction means for extracting a structure region indicating a predetermined structure from each of a plurality of frame images indicating the dynamics of the chest;
A lung that extracts a lung field region from each of the plurality of frame images and uses the region other than the structure region in the extracted lung field region to perform alignment of the lung field region between the plurality of frame images. Field alignment means;
In the image after alignment of the lung field region, a structure movement amount calculation means for calculating the movement amount of the structure between adjacent frame images;
An inter-frame difference image generating means for generating an inter-frame difference image by taking a difference of signal values of corresponding pixels between temporally adjacent frame images after the lung field alignment;
Signal change amount estimation for estimating a signal change amount due to movement of the structure by generating a difference image between the image obtained by moving the structure region by the movement amount of the structure and the original structure region Means,
When the estimated signal change amount exceeds a predetermined threshold, the signal value of the region corresponding to the extracted structure region in the inter-frame difference image is replaced with the signal value of surrounding pixels, Alternatively, correction means for correcting by subtracting the estimated value of the signal change amount due to the movement of the structure ,
A dynamic image processing apparatus comprising:   The dynamic image processing apparatus according to claim 1, further comprising means for reducing a spatial signal change of the extracted structure region in the plurality of frame images.   The dynamic image processing apparatus according to claim 1, further comprising display means for displaying the corrected inter-frame difference image as a moving image or a still image. A region where the sign of the signal value of the surroundings is reversed is extracted from the corrected inter-frame difference image, and the respiratory function of the lung field region is based on the ratio of the extracted region to the lung field region. A determination means for determining whether or not it is normal;
The dynamic image processing apparatus according to claim 3, wherein the display unit also displays a determination result by the determination unit. Computer
A structure extraction means for extracting a structure region indicating a predetermined structure from each of a plurality of frame images indicating the dynamics of the chest;
A lung that extracts a lung field region from each of the plurality of frame images and uses the region other than the structure region in the extracted lung field region to perform alignment of the lung field region between the plurality of frame images. Field alignment means,
A structure movement amount calculating means for calculating a movement amount of the structure between adjacent frame images in the image after alignment of the lung field region;
An inter-frame difference image generating means for generating an inter-frame difference image by taking a difference between signal values of corresponding pixels between temporally adjacent frame images after the lung field alignment;
Signal change amount estimation for estimating a signal change amount due to movement of the structure by generating a difference image between the image obtained by moving the structure region by the movement amount of the structure and the original structure region means,
When the estimated signal change amount exceeds a predetermined threshold, the signal value of the region corresponding to the extracted structure region in the inter-frame difference image is replaced with the signal value of surrounding pixels, Or correction means for correcting by subtracting the estimated value of the signal change amount due to the movement of the structure ,
Program to function as.

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