JP3919799B2 - Radiographic image processing apparatus, radiographic image apparatus, radiographic image system, program, computer-readable storage medium, and radiographic image processing method - Google Patents

Description

  The present invention relates to a radiographic image processing apparatus, a radiographic image apparatus, a radiographic image system, a program, a computer-readable storage medium, and a radiographic image processing method for processing a radiographic image taken with respiration.

  In recent years, a system for taking a radiographic image of a subject using a semiconductor image sensor having a large area has been developed. This system has a practical advantage that an image can be recorded over a very wide range of radiation exposure compared to a conventional radiographic system using silver salt photography. That is, X-rays with a very wide dynamic range are read as electrical signals using photoelectric conversion means, and the electrical signals are further converted into digital signals. By processing this digital signal and outputting the radiation image as a visible image to a recording material such as a photographic photosensitive material or a display device such as a CRT, a good radiation image can be obtained even if the radiation exposure varies to some extent. It is done.

  In imaging using a semiconductor image sensor, respiratory dynamic imaging in which the lungs are imaged while breathing is expected to provide new pathological information in place of conventional image diagnosis centered on still images. This respiratory dynamic imaging means taking an image from a state where the lung is fully inflated to a state where the lung is sufficiently contracted as a moving image, preferably from the expansion phase and the contraction phase of the lung. It is preferable to photograph one cycle of respiration as a moving image.

  In the case of taking a chest still image, the patient stands still with the chin resting on the chin rest, and a chest image is taken during that time. However, when taking pictures with breathing, it is difficult for the patient to keep the chin resting on the chin rest, especially in the case of a patient who is sick and weak, without placing the chin on the chin rest. It is possible to shoot.

  In such pulmonary dynamic imaging, patient motion may occur. That is, there is a sufficient possibility that the position of the thorax in the sensor region varies. When diagnosis is performed by sequentially switching and displaying images taken in this manner, since the thorax moves between the images, the lesion also moves and is difficult to diagnose.

  Considering the application of computer diagnostic support (CAD) technology to such dynamic images, tracking errors due to thoracic movement tend to occur when a lesion is tracked and its dynamic change is extracted. Become.

  The present invention solves such problems and can provide a radiological image processing device, a radiographic image device, a radiographic image system, a program, a computer-readable storage medium, and a radiographic image processing capable of obtaining a chest dynamic image suitable for diagnosis. It aims to provide a method.

  According to a first aspect of the present invention for achieving the above object, an input means for inputting a chest dynamic image composed of a plurality of chest radiographic images indicating respiratory dynamics of a subject's chest in a respiratory state, and input by the input means. Region recognition means for recognizing a predetermined anatomical region in each chest radiographic image constituting the chest dynamic image, and based on the anatomical region recognized by the region recognition means, The radiation image processing apparatus includes an alignment unit that performs alignment.

  2. The radiographic image processing apparatus according to claim 1, further comprising display means for displaying a chest dynamic image composed of the chest radiographic images after alignment by the alignment means. It is.

  According to a third aspect of the present invention, the image processing apparatus further includes image analysis means for performing an analysis process for assisting image diagnosis on a chest dynamic image composed of the chest radiographic images after alignment by the alignment means. The radiation image processing apparatus according to claim 1.

  According to a fourth aspect of the present invention, in the radiological image processing apparatus according to any one of claims 1 to 3, wherein the anatomical region includes a lung field region.

  The radiographic image processing apparatus according to claim 4, wherein the alignment unit performs alignment of each chest radiographic image based on a predetermined reference region in the lung field region. is there.

  According to a sixth aspect of the present invention, there is provided a radiographic image device comprising the elements constituting the radiographic image processing device according to any one of the first to fifth aspects.

  A seventh invention is a radiographic image system in which a plurality of devices are communicably connected to each other, and each component constituting the radiographic image processing device according to any one of claims 1 to 5 is provided. This is a radiation image system.

  An eighth invention is a program for causing a computer to function as predetermined means, and the predetermined means includes each means constituting the radiographic image processing apparatus according to any one of claims 1 to 5. It is a program characterized by including.

  A ninth invention is a computer-readable storage medium characterized by storing the program according to the eighth aspect.

  A tenth aspect of the invention configures an input step of inputting a chest dynamic image composed of a plurality of chest radiographic images indicating respiratory dynamics of a subject's chest in a respiratory state, and the chest dynamic image input in the input step A region recognizing step for recognizing a predetermined anatomical region in each chest radiographic image, and an alignment step for aligning each chest radiographic image based on the anatomical region recognized in the region recognizing step; A radiation image processing method characterized by comprising:

  According to the present invention, it is possible to provide a radiographic image processing apparatus, a radiographic image apparatus, a radiographic image system, a program, a computer-readable storage medium, and a radiographic image processing method capable of obtaining a chest dynamic image suitable for diagnosis. it can.

  A preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings (FIGS. 1 to 10). FIG. 1 shows the configuration of a system according to this embodiment. In FIG. 1, reference numeral 4 denotes a two-dimensional sensor composed of an amorphous semiconductor and a fluorescent screen. The pixel size is 160 μ × 160 μ and the number of pixels is 2688 × 2688. Here, the sensor 4 is used for standing position photography and is attached to a stand 5.

  The X-ray tube 2 is supported on the ceiling by the ceiling suspension means 3 and is movable according to the patient's physique. X-rays emitted from the X-ray tube 2 pass through the patient and reach the sensor 4. X-rays are converted into visible light by a fluorescent screen, and the visible light is converted into image data using an amorphous semiconductor. The shooting timing is instructed from the shooting instruction means 9 by a shooting engineer or the like. Based on the instruction, the system control unit 8 controls the X-ray control unit 2 and the sensor driving unit 11 to acquire an X-ray image.

  The patient's respiratory cycle consists of an inspiratory mode and an expiratory mode. The inhalation mode is a mode in which the patient inhales, and accordingly, the area of the lung field in the thorax is enlarged and the diaphragm is pushed down. The exhalation mode is a mode in which the patient exhales, and accordingly, the lung field area becomes smaller and the diaphragm rises.

  The breathing cycle refers to one cycle of breathing motion including one exhalation mode and inhalation mode. During an X-ray exposure period based on an instruction from the imaging instruction means 9 by an operator such as an imaging engineer, a plurality of images during the respiratory cycle are collected. The upper part of FIG. 2 shows three representative images taken during the respiratory cycle. As described above, the rib cage moves with breathing.

  That is, it is not always easy for the patient to breathe without moving the rib cage when taking a breathing video. In this embodiment, since X-ray pulses are emitted three times per second and an image corresponding to the pulse X-rays is captured, the inspiration mode is 5 seconds, the expiration mode is 5 seconds, and a total of 10 When a second respiratory cycle is imaged, the number of images obtained is 30.

  FIG. 2 shows three images during the expiration mode. The broken line in the figure is a line for specifying the thorax position of the first image. The image obtained by shifting (moving) the image so that the thorax touches this broken line is shown in the lower part of FIG. It is three images shown.

  FIG. 2 conceptually shows body motion correction as an object of the present invention.

  The captured image is transmitted to the image processing unit 12 via the sensor driving unit 11. The image processing unit 12 analyzes the image to perform thorax alignment by shifting the acquired image, and the image storage unit 13 stores the aligned image. The image processing means 12 is configured by using a computer, and the image storage means 13 is configured by a memory or a magnetic disk of the computer.

  The stored image is sequentially displayed as a moving image by the image display unit 14 based on an instruction from an instruction unit (not shown) operated by the operator. Each of the above means is connected to the system control means 8 via the system bus 7. The system control means 8 controls the driving timing and data flow of each means described above. The system control means 8 can be composed of a computer that operates according to a computer program.

  The image processing steps executed by the image processing means 12 will be described with reference to FIG.

  Assuming that approximately 30 images (hereinafter referred to as N images) are taken over a period including the breathing cycle as shown in FIG. 2, N images are input to the image processing means 12 (step 31). Lung field region extraction processing is executed for each image (step 32).

  In the lung field region extraction step 32, a lung field region is extracted from the chest front image. FIG. 4 shows a histogram of a typical chest front image. The histogram is composed of three peaks. Each mountain corresponds to a lung field region 81, an X-ray element missing region 82, and other regions 83 (mediastinum, heart, subdiaphragm region, etc.) as shown in FIG. In order to specify the lung field region, the image may be binarized based on whether or not the pixel value is between the threshold value 1 and the threshold value 2 shown in FIG.

  FIG. 5 shows a cumulative histogram for the histogram shown in FIG. 4 and a straight line obtained by linear regression of the cumulative histogram. Empirically, the pixel value at the intersection where the cumulative histogram intersects with the regression line indicates threshold value 1. Specifically, as shown in FIG. 6, an error (difference) between the cumulative histogram and its regression line is calculated, and the point at which the error crosses zero indicates threshold value 1.

  As described above, since the threshold value 1 is obtained, the histogram shown in FIG. 7 can be calculated by excluding the region showing the pixel value equal to or higher than the threshold value 1 from the image and calculating the histogram of the remaining region. Although illustration is omitted, when a difference between the cumulative histogram of the histogram of FIG. 7 and its regression line is calculated and a point at which the difference crosses zero is obtained, the pixel value at that point generally corresponds to the threshold value 2. If the input image of the chest is binarized so that the pixel value between the threshold value 1 and the threshold value 2 is 1 and the other pixel values are 0, the lung field region can be extracted. This binary image is called a lung field binary image.

  Next, the thorax position is determined based on the lung field binary image (step 31). This determination method is performed by calculating vertical and horizontal projections of the lung field binary image. As shown in FIG. 9, the projection of the lung field binary image shows a relatively steep rise distribution, so that the obtained projection is binarized by a predetermined value so that it is indicated by a broken line. It is possible to specify the thorax region.

  When the position of the thorax for each image is determined, each image is shifted (moved) to the reference thorax position (step 34). The shift is performed so that (1) the upper part of the lung (pulmonary apex) matches, and (2) the center matches to reduce the shift of the left and right regions of the rib cage. The thorax position that is the target of the shift may be a predetermined position, or may be the thorax position of the first image taken.

  In the image shift process 34, when the image is largely shifted, an image shortage may occur. In such a case, if a value is not written in an insufficient part of the image, when continuous image display is performed, an image with a different luminance is displayed on the background of a part of the image, which makes the image unsightly.

  As shown in the example of FIG. 10, in order to avoid this, it is possible to obtain an image with no sense of incongruity by filling the deficient portion of the image with the pixel values of the above-described X-ray element missing region. The pixel value of the background region is obtained in the above-described lung field region extraction step 32. Of course, the pixel value is not limited to the pixel value in the blank region, and an intermediate luminance value having a relatively low luminance may be used.

  As a different embodiment, it is conceivable to perform an analysis process such as a computer diagnosis support (CAD) technique on the image aligned in the above embodiment.

  The CAD technology is a technology that supports a diagnosis by a doctor by detecting a lesion candidate from an image or automatically measuring and displaying the size of a designated lesion. Conventionally, such CAD technology has been applied to a single still image or a plurality of still images taken over time, but has not been applied to a plurality of images accompanying breathing. .

  When detecting the lung nodule for each of multiple images with breathing, if the chest is aligned in advance, the shift between images of the nodule detected as possibly ill will be canceled. It becomes possible to do. However, the movement of the lesion accompanying breathing cannot be canceled.

  Regarding individual CAD techniques, prior art can be referred to, and therefore, although not described in detail here, different techniques are required depending on the purpose of diagnosis support. A chest image can be roughly classified into shadow diagnosis support and texture disease diagnosis support.

Support for shadow diagnosis requires a process that is used to detect calcification in breast images, tumors of the tumor, or tumors (MASS) in mammograms. Supporting texture disease diagnosis requires a process used to detect interstitial pneumonia found in chest images. For example, the following documents can be referred to for techniques and feature quantities used for texture disease diagnosis support.
Shigehiko Katsuragawa, et al .: Possibility of computer diagnosis support for interstitial diseases, Journal of Japanese Society of Medical Radiology, 50: 753-766, 1990.
Yasuo Sasaki, et al .: Quantitative evaluation by texture analysis of pneumoconiosis standard photographs, Japanese Society of Medical Radiology, 52: 1385-1393, 1992.

  As described above, according to the present embodiment, the alignment of the thorax is performed, and the movement due to the body movement of the lesioned part is canceled, so that diagnosis is easy. For the same reason, it is effective in improving the CAD analysis accuracy.

(Other embodiments)
The present invention is a system comprising a plurality of devices (for example, one or more image processing devices, one or more interfaces, one or more radiation imaging devices, one or more X-ray generation devices, etc.), or an image processing device Needless to say, the present invention can be applied to any configuration in which the radiation imaging apparatus is integrated.

  Another object of the present invention is to supply a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and a computer (CPU or MPU) of the system or apparatus. Needless to say, this can also be achieved by reading and executing the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the program code and the storage medium storing the program code constitute the present invention.

  As a storage medium for supplying the program code, a ROM, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, or the like is used. it can.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS or the like running on the computer based on an instruction of the program code performs actual processing. It goes without saying that the present invention is also configured when a part or all of the above is performed and the functions of the above-described embodiment are realized by the processing.

  Furthermore, after the program code read from the storage medium is written to a memory provided in an expansion function board inserted in the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the present invention is also configured when a CPU or the like provided in an expansion board, a function expansion unit or the like performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

  When the present invention is applied to the above-described program code and computer-readable storage medium, the program code is, for example, a program code corresponding to the flowchart shown in FIG. 3 described in the above-described embodiment, and The storage medium stores, for example, a program code corresponding to the flowchart.

System Configuration Conceptual illustration of thorax alignment Flow chart showing processing by image processing means 12 Histogram of chest front image Figure showing cumulative histogram and its regression line Error between cumulative histogram and its regression line Histogram of chest front image below threshold 1 Schematic diagram of chest front image Explanatory drawing of projection of lung field binary image Illustration of lack of images due to shift

Explanation of symbols

12 Image processing means

Claims (5)

A radiological image processing apparatus that dynamically displays a plurality of chest radiological image data generated by imaging the respiratory dynamics of a subject chest multiple times ,
Region recognition means for recognizing a ribcage region in each chest radiographic image data;
Alignment means for shifting the plurality of chest radiographic image data to a reference thorax position while keeping the shape of the thorax region in the shape at the time of imaging ;
An image display means for sequentially displaying the plurality of chest radiographic image data subjected to the alignment, and a radiographic image processing apparatus. In the alignment by the alignment unit, the apex region that is the upper part of the lung in the thoracic region recognized by the region recognition unit coincides with the pulmonary apex region of the reference thorax , and the central portion of the thoracic region coincides The radiographic image processing apparatus according to claim 1, wherein the plurality of chest radiographic image data are aligned. 2. The analysis processing unit according to claim 1, further comprising an analysis processing unit that detects a lesion candidate from a plurality of chest radiographic image data whose body motion is corrected by the alignment unit, and automatically measures the size of the detected lesion candidate . Radiation image processing device. X-ray generation means for generating X-rays;
A sensor for converting the X-rays into the chest radiation image data;
A radiographic image system in which the radiographic image processing apparatuses according to claim 1 are connected to be communicable with each other. A radiological image processing method for dynamically displaying a plurality of chest radiological image data generated by imaging the respiratory dynamics of a subject chest multiple times ,
A region recognition step for recognizing a thorax region in each chest radiographic image data;
An alignment step performed to shift the plurality of chest radiographic image data to a reference ribcage position in a state in which the shape of the ribcage region is maintained in the shape at the time of imaging ;
A radiation image processing method comprising: an image display step of sequentially displaying the plurality of chest radiation image data subjected to the alignment .

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