JP2007007307A - Image-processing method and medical image-processing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To construct an image of a subject without deterioration of the image by correct alignment of a plurality of X-ray images. <P>SOLUTION: In a control device 20, alignment is conducted so that image-overlapped parts of each X-ray image are concordant in a condition that extension or reduction interpolation processing is performed so that each X-ray image with different magnification put from an image-generating device 10 are concordant. Furthermore, barycenters on the image-overlapped parts are determined, and barycenters in the original X-ray images untreated by the extension or reduction interpolation processing which corresponds to the determined barycenters, are also determined. Subsequently, each X-ray image is aligned in accordance with the barycenters determined in the original X-ray image so as to correspond to the subject and is composed connecting together, in order to form one image of the subject. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing method for an X-ray image obtained by X-ray imaging and a medical image processing system for processing data of the X-ray image.

Conventionally, when performing X-ray imaging of a large subject, a long cassette using a plurality of phosphor sheets is used as shown in FIG. In order to capture all areas to be imaged without omission, this long cassette is housed in a casing with the end portions of the phosphor sheets partially overlapped and fixed in position. After imaging, the X-ray image recorded on each phosphor sheet is read and processed, and the image portions corresponding to the overlapping areas of the phosphor sheet are overlapped and connected to form one subject image. (For example, refer patent documents 1 and 2).
Japanese Patent Laid-Open No. 2002-301055 JP 2002-214747 A

  However, since the phosphor sheets are stacked, the distances to the X-ray sources of the phosphor sheets are different. For example, when the respective phosphor sheets L1 to L3 are arranged in a positional relationship as shown in FIG. 3, as shown in FIG. 4, the phosphor sheet L1 arranged on the X-ray source side and the rear surface thereof are arranged. The distances from the X-ray source are different between the phosphor sheets L2 and L3. Therefore, an X-ray image by the phosphor sheet L1 closer to the X-ray source (this is referred to as X-ray image A) and an X-ray image by the phosphor sheets L2 and L3 far from the X-ray source (this is an X-ray image) X and X-ray images B and C are slightly enlarged.

Here, when the distance from the X-ray source to the phosphor sheet L1 is H1, and the distance between the phosphor sheet L1 and the phosphor sheets L2 and L3 is H2, the imaging magnification of the X-ray image A is used as a reference. The magnification n of the imaging magnification of the X-ray images B and C can be obtained by the following equation.
n = (H1 + H2) / H1

  For example, when H2 = 2 (mm) and H1 = 1.5 to 2.0 (m), the enlargement ratio n is in the range of 1.1000 to 1.0013, and the X-ray images B and C are X-ray images. Compared with A, it is enlarged by about 0.1 to 0.13%. The enlargement ratio n increases as the distance from the X-ray source is shorter.

  That is, when photographing is performed using a long cassette, the images of the portions where the phosphor sheets overlap do not completely match. Therefore, in the alignment when combining the X-ray images A to C individually read from the phosphor sheets L1 to L3, the X-ray image A is enlarged to match the X-ray images B and C, or X-rays It is desirable to reduce the images B and C according to the X-ray image A.

  However, from the viewpoint of diagnostic accuracy, a subject image composed of an X-ray image subjected to such enlargement interpolation processing or reduction interpolation processing is not preferable because the image deteriorates.

  An object of the present invention is to accurately align a plurality of X-ray images to form one subject image without image degradation.

The invention described in claim 1
An X-ray image of one subject is recorded across a plurality of phosphor sheets with end portions partially overlapped, and the X-ray images are individually read from each of the plurality of phosphor sheets. In the image processing method of connecting the X-ray images after aligning the read X-ray images in correspondence with the subject,
An image obtained by performing an enlargement interpolation process or a reduction interpolation process on the X-ray image when the read X-ray image is aligned is used, and the X-ray image is used when connecting the X-ray images. And

The invention according to claim 2 is the image processing method according to claim 1,
The X-ray image is subjected to enlargement interpolation processing or reduction interpolation processing so that the X-ray images have the same imaging magnification.

The invention according to claim 3 is the image processing method according to claim 2,
The imaging magnification of the X-ray image is the same as the imaging magnification of the X-ray image of the phosphor sheet disposed in the center among the plurality of phosphor sheets.

The invention according to claim 4 is the image processing method according to claim 2,
The imaging magnification of the X-ray image is the same as the imaging magnification of the X-ray image of the phosphor sheet closest to the subject among the plurality of phosphor sheets.

The invention according to claim 5 is the image processing method according to any one of claims 2 to 4,
Alignment is performed so that overlapping image portions of the respective X-ray images having the same imaging magnification by the enlargement interpolation process or the reduction interpolation process coincide, and the connection of the X-ray images is performed based on the result of the alignment. It is characterized by performing.

The invention according to claim 6 is a medical image processing system,
An X-ray image of one subject is recorded across a plurality of phosphor sheets with end portions partially overlapped, and the X-ray images are individually read from each of the plurality of phosphor sheets. After the read X-ray images are aligned with each other in correspondence with the subject, when the X-ray images are connected,
An image obtained by performing an enlargement interpolation process or a reduction interpolation process on the X-ray image when the read X-ray image is aligned is used, and the X-ray image is used when connecting the X-ray images. And

The invention described in claim 7 is the medical image processing system according to claim 6,
The X-ray image is subjected to enlargement interpolation processing or reduction interpolation processing so that the X-ray images have the same imaging magnification.

The invention according to claim 8 is the medical image processing system according to claim 7,
The imaging magnification of the X-ray image is the same as the imaging magnification of the X-ray image of the phosphor sheet disposed in the center among the plurality of phosphor sheets.

The invention according to claim 9 is the medical image processing system according to claim 7,
The imaging magnification of the X-ray image is the same as the imaging magnification of the X-ray image of the phosphor sheet closest to the subject among the plurality of phosphor sheets.

The invention according to claim 10 is the medical image processing system according to any one of claims 7 to 9,
Alignment is performed so that overlapping image portions of the respective X-ray images having the same imaging magnification by the enlargement interpolation process or the reduction interpolation process match, and the connection of the X-ray images is performed based on the result of the alignment. It is characterized by performing.

  According to the first, second, fifth, sixth, seventh, and tenth aspects of the invention, it is possible to accurately perform alignment, and it is possible to construct a subject image from an X-ray image without image deterioration, which is favorable. It is possible to provide a doctor with a subject image with high image quality.

  According to the third and eighth aspects of the present invention, the phosphor sheet arranged in the center is always overlapped with the X-ray image of the other phosphor sheet at one end or both ends. By adjusting the imaging magnification with reference to the X-ray image of the sheet, alignment can be facilitated.

  According to the fourth and ninth aspects of the present invention, since the X-ray image of the phosphor sheet closest to the subject is close to the actual size (actual size) of the subject, the imaging magnification is adjusted based on the X-ray image. By doing so, it is possible to perform alignment at a photographing magnification close to the actual size.

First, the configuration will be described.
FIG. 1 shows a system configuration of the medical image processing system 1.
This medical image processing system 1 performs examination imaging of a subject (patient), performs various image processing on a medical image obtained by imaging, and outputs it to a monitor or film to provide the medical image to a doctor. It is.

  As illustrated in FIG. 1, the medical image processing system 1 includes an image generation device 10, a control device 20, an image interpretation terminal 30, and a film output device 40. The devices 10 to 40 are connected via a communication network N. The DICOM (Digital Imaging and Communication in Medicine) standard is applied to the communication network N.

Hereafter, each component apparatus 10-40 is demonstrated.
The image generation apparatus 10 generates digital data of an X-ray image (medical image) of a subject. The image generation device 10 is not only equipped with a data generation function such as an FPD (Flat Panel Detector), a cassette-dedicated reader, a film digitizer, but also a CR (Computed Radiography) with an imaging function and a data generation function, Various modalities such as CT (Computed Tomography) and MRI (Magnetic Resonance Imaging) are also included. In this embodiment, an example of a reading apparatus dedicated to a cassette related to X-ray imaging will be described as the image generating apparatus 10.

  The image generation device 10 executes a process of reading an X-ray image of a subject from a phosphor sheet stored in the cassette in accordance with the read instruction information input from the control device 20, and reads the read X-ray image. It transmits to the control apparatus 20 which instruct | indicated.

  The control device 20 can be connected to an RIS (Radiology Information System; information system for collectively managing radiology information) and HIS (Hospital Information System; information system for collectively managing hospital information), which are not shown. Imaging order information that is instruction information related to imaging is received from the information system. The imaging order information is issued upon receiving a request from a doctor, and is specified by the patient ID, name, gender and other patient information of the patient to be imaged, the examination ID for distinguishing the examination, and the examination. This includes inspection information relating to the inspection such as the imaging region and the imaging method.

  The control device 20 generates instruction information regarding the reading process in the image generation device 10 according to the photographing order information, and transmits the instruction information to the image generation device 10. Then, when the medical image read from the image generation device 10 is acquired, the imaging order information corresponding to the medical image is written in the header of the medical image, for example, and attached to the medical image, whereby the database of each medical image is obtained. And manage.

  The interpretation terminal 30 is a display device for a doctor to interpret a medical image, and includes a display unit such as an LCD (Liquid Crystal Display), and displays the medical image distributed by the control device 20 on the display unit.

  The film output device 40 is an output unit that outputs a medical image distributed by the control device 20 onto a film. The film output device 40 can output to a plurality of sizes of film, and outputs a medical image under a specified output condition of a specified size film according to the output control information received together with the medical image from the control device 20. .

Next, the control device 20 that performs the processing operation according to the present invention will be further described.
FIG. 2 is a diagram illustrating an internal configuration of the control device 20.
As shown in FIG. 2, the control device 20 includes a control unit 21, an operation unit 22, a display unit 23, a communication unit 24, a program memory 25, and an image memory 26.

  The control unit 21 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and the like, and comprehensively controls execution of processing by each unit in accordance with a control program stored in the program memory 25.

  The operation unit 22 is an operation unit configured to include a keyboard, a touch panel configured integrally with the display unit 23, a mouse, and the like, and generates operation signals corresponding to these operations and outputs them to the control unit 21. .

  The display unit 23 is a display unit including an LCD or the like, and displays various operation screens, processing results by the control unit 21, and the like according to display control of the control unit 21.

  The communication unit 24 includes a NIC (Network Interface Card), a modem, and the like, and transmits and receives data to and from an external device on the communication network N such as the image generation device 10 and the image interpretation terminal 30.

  The program memory 25 stores various control programs, parameters necessary for executing these programs, data processed by executing the programs, and the like.

  The image memory 26 is composed of a large-capacity memory, and stores X-ray images or composite images in a database.

Next, the operation of the medical image processing system 1 configured as described above will be described.
First, in the medical image processing system 1, radiographing order information issued in RIS, HIS, or the like is displayed on the control device 20, and X-ray imaging of a target patient is performed by an imaging operation of a technician according to the displayed radiographing order information. . In this embodiment, in order to perform imaging | photography about large parts, such as a leg part, suppose that the elongate cassette which has three fluorescent substance sheets which are a detector is used.

  The three phosphor sheets are housed in a cassette housing 5 as shown in FIG. 3 and used for photographing. In order to shoot without omission over the entire subject area, the phosphor sheets L1 to L3 are arranged so that the end portions thereof overlap with the other phosphor sheets L1 to L3 as shown in FIG. Although not shown, the cassette housing 2 is provided with holding means such as a holder for fixing the positions of the phosphor sheets L1 to L3 disposed therein.

FIG. 4 shows a view of the phosphor sheets L1 to L3 shown in FIG. 3 as viewed from the D1 direction. 4 corresponds to FIG. 3 as viewed from the direction D2.
As shown in FIG. 4, the phosphor sheet L1 is disposed at a position closest to the X-ray source, and the phosphor sheets L2 and L3 are disposed behind the phosphor sheet L1. The phosphor sheets L2 and L3 have the same distance to the X-ray source. Since the distance to the X-ray source is different between the phosphor sheet L1, L2 and L3, the imaging magnifications of the phosphor sheets L1 to L3 are different. Note that the imaging magnification refers to the ratio between the size of the image recorded on the phosphor sheet and the actual size of the subject. Since each of the phosphor sheets L1 to L3 is disposed on the back of the subject irradiated with X-rays, the imaging magnification of those X-ray images takes a value of at least 1 or more.

Here, when the distance from the X-ray source to the phosphor sheet L1 is H1, and the distance between the phosphor sheet L1 and the phosphor sheets L2 and L3 is H2, the phosphor sheet for the X-ray image of the phosphor sheet L1. The magnification n of the imaging magnification of the X-ray images of L2 and L3 is obtained by the following formula (1).
n = (H1 + H2) / H1 (1)
That is, the X-ray image recorded on the phosphor sheets L1 and the X-ray images recorded on the phosphor sheets L2 and L3 have a 1: n relationship, and the X-rays recorded on the phosphor sheets L2 and L3. The image is an image enlarged by n times with respect to the X-ray image recorded on the phosphor sheet L1.

  An engineer sets an imaging region of a subject on a cassette containing such three phosphor sheets, and performs X-ray imaging using an X-ray imaging apparatus. Then, after photographing, the phosphor sheets L <b> 1 to L <b> 3 are taken out from the cassette housing 2 and sequentially loaded into the image generation apparatus 10.

In the image generation apparatus 10, the X-ray image recorded on the phosphor sheets L1 to L3 is read, and digital data of the X-ray images read from the phosphor sheets L1 to L3 is generated. The three X-ray images are transmitted to the control device 20 after the image generation device 10 is attached with information related to image generation such as reading conditions.
For convenience of explanation, the X-ray image from the phosphor sheet L1 is A, the X-ray image from the phosphor sheet L2 is B, and the X-ray image from the phosphor sheet L3 is C.

In the control device 20, the X-ray images A to C transmitted from the image generation device 10 are once stored in the image memory 26, and then each X-ray image A to C is used to form one subject image. A connection process for connecting and synthesizing the line images A to C is performed.
Hereinafter, the connection process according to the present invention will be described with reference to FIG.

  In the connection process shown in FIG. 5, first, in order to make the X-ray images A to C have the same imaging magnification, the control unit 21 creates a processed image with the same magnification from the X-ray images A to C (step S1). ). Here, among the three phosphor sheets L1 to L3, the imaging magnifications of the other X-ray images B and C are adjusted based on the imaging magnification of the X-ray image A of the phosphor sheet L1 disposed in the center. At the time of imaging, the subject is generally set so that the portion important for the examination becomes the central portion. Therefore, the X-ray image A from the phosphor sheet L1 arranged at the center forms the subject image. For this reason, the entire image is often used. Further, the phosphor sheet L1 is overlapped with any of the other phosphor sheets L2 and L3. Therefore, by using the X-ray image A as a reference, alignment with the other X-ray images B and C is facilitated.

  FIG. 6A shows a state where the X-ray image B is subjected to reduction interpolation processing at a magnification 1 / n in accordance with the imaging magnification of the X-ray image A. The processed image BR generated by the reduction interpolation process has the same magnification as the X-ray image A. Note that the X-ray image C is processed in the same manner as the X-ray image B, and therefore is not shown in FIG. 6 (the same applies to FIGS. 8 and 9). In addition, here, a reduction interpolation process is performed in order to match the X-ray image A with the smallest imaging magnification. However, in order to match an X-ray image with a large imaging magnification, an enlarged interpolation process may be performed to create a processed image. .

Next, alignment of the X-ray image A and the processed images BR and CR is performed by the control unit 21.
Since the phosphor sheets L1 to L3 are partially overlapped, the respective X-ray images A to C should include overlapping image portions. Therefore, as shown in FIG. 6B, in the X-ray image A and the processed image BR, alignment is performed by the control unit 21 so that the overlapping image portions match (step S2).

The alignment method is not particularly limited. For example, as described in Japanese Patent Application Laid-Open No. 2000-257661, an overlapping region of the phosphor sheets L1 to L3 is detected in the X-ray image A, and an image portion corresponding to the overlapping region is detected. As a template, overlapping image portions may be detected by performing template matching in the processed images BR and CR, and alignment may be performed based on this.
Further, the alignment may be performed by detecting an image portion in which a difference in pixel values is minimum between the overlapped image portion detected in the X-ray image A and the processed images BR and CR.

  Furthermore, it is good also as a structure which can be visually aligned by manual operation of an engineer instead of performing alignment processing automatically. In this case, an operation screen as shown in FIG. 7 is displayed on the display unit 23, and images A, BR, and CR are displayed on the operation screen, and the images A, BR, and CR are superimposed and displayed. The image F is displayed. Then, the positions of the images A, BR, and CR constituting the connected image F are made movable through the operation unit 22, and the positions of the images A, BR, and CR are moved according to the movement operation by the operation unit 22. Position.

When the alignment is performed, as shown in FIG. 6C, the center of gravity of the overlapped image portion in each of the images A, BR, and CR is calculated by the control unit 21 (step S3). Here, the center of gravity of the X-ray image A and _{G A,} representing the position information X, the Y coordinates _G A (XA, YA). The X coordinate corresponds to the main scanning direction during image reading, and the Y coordinate corresponds to the sub scanning direction. Further, the centroids of the processed images BR and CR are G _BR and G _CR , respectively, and the position information is G _BR (XB, YB) and G _CR (XC, YC).

Next, as shown in FIG. 8, based on the obtained position information of the center of gravity G _BR and G _CR , the original X-ray images B and C not subjected to the reduction interpolation process correspond to the centers of gravity G _BR and G _CR . the center of gravity _G B to the position information of the _{G C} is determined (step S4). Since the processed images BR and CR are obtained by reducing and interpolating X-ray images B and C at a magnification of 1 / n, the gravity center positions of G _B and G _C are G _B (nXB, nYB), G _C ( nXC, nYC).

When the position of the center of gravity _G A ~G _C is determined in each X-ray image A through C, the control unit 21, so that each gravity center position of the center of gravity _{G A} and _{G B} are matched as shown in FIG. 9 (a) (In the case of the X-ray image C, the centroids G _A and G _C obtained from the overlapping portions of the X-ray images A and _C ) and the X-ray images A to C are arranged and aligned (step S5). Next, as shown in FIG. 9B, after the X-ray images B and C are trimmed and deleted with respect to the image portion overlapping with the X-ray image A, the X-ray images A to C are connected and synthesized. Then, one subject image is formed (step S6).

  The subject image created as described above is transmitted to the image interpretation terminal 30 or transmitted to the film output device 40 and subjected to interpretation by a doctor. Note that when the subject image is output by the film output device 40, it is considered that the size of the subject image exceeds the prescribed film size, so that each of the X-ray images A to C (X-ray images B and C is described) It is also possible to transmit every trimmed image). The subject image can be reconstructed by an engineer bonding the films on which the X-ray images A to C are output.

  As described above, according to the present embodiment, alignment is performed in a state where X-ray images having different imaging magnifications are once set to the same imaging magnification, and the X-ray images are aligned based on the result of the alignment. Do. As a result, a subject image can be constructed from the original X-ray image without image deterioration, and each X-ray image constituting the subject image can be accurately aligned.

  In the above description, the X-ray image read from each of the phosphor sheets L1 to L3 is configured to be aligned and connected in the control device 20, but may be performed in any of the components of the medical image processing system 1. It is also possible to newly provide a dedicated device for the processing.

  Moreover, although the example which applied the fluorescent substance sheet as a detector was demonstrated in the said embodiment, not only this but the present invention is applicable also when using other detectors, such as FPD (Flat Panel Detector). .

It is a figure which shows the system configuration | structure of a medical image processing system. It is a figure which shows the internal structure of the control apparatus of FIG. It is a figure which shows the internal perspective view of the cassette in which the some fluorescent substance sheet was accommodated. It is the figure which looked at the cassette of FIG. 3 from the different direction. It is a flowchart explaining the image processing performed by a control apparatus. It is a figure explaining the procedure which connects the X-ray image read from each fluorescent substance sheet, and comprises one subject image. It is a figure which shows the example of an operation screen for performing alignment operation of each X-ray image. It is a figure explaining the procedure which connects the X-ray image read from each fluorescent substance sheet, and comprises one subject image. It is a figure explaining the procedure which connects the X-ray image read from each fluorescent substance sheet, and comprises one subject image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Medical image processing system 10 Image generation apparatus 20 Control apparatus 21 Control part 22 Operation part 23 Display part 25 Program memory 30 Interpretation terminal 40 Film output apparatus L1-L3 Phosphor sheet

Claims (10)

An X-ray image of one subject is recorded over a plurality of detectors whose ends are partially overlapped, and the X-ray images are individually read from each of the plurality of detectors. In the image processing method of connecting the X-ray images after aligning the line images with each other in correspondence with the subject,
At the time of alignment of the read X-ray image, an image obtained by subjecting at least one of the X-ray images to enlargement interpolation processing or reduction interpolation processing is used, and when the X-ray images are connected, the X-ray image is used. An image processing method.   The image processing method according to claim 1, wherein an enlargement interpolation process or a reduction interpolation process is performed on the X-ray images so that the imaging magnifications of the X-ray images are the same.   3. The image processing method according to claim 2, wherein an imaging magnification of the X-ray image is the same as an imaging magnification of an X-ray image of a detector arranged in the center among the plurality of detectors. .   3. The image processing according to claim 2, wherein an imaging magnification of the X-ray image is the same as an imaging magnification of an X-ray image of a detector closest to the subject among the plurality of detectors. Method.   Alignment is performed so that overlapping image portions of the respective X-ray images having the same imaging magnification by the enlargement interpolation process or the reduction interpolation process coincide, and the connection of the X-ray images is performed based on the result of the alignment. The image processing method according to claim 2, wherein the image processing method is performed. An X-ray image of one subject is recorded over a plurality of detectors whose ends are partially overlapped, and the X-ray images are individually read from each of the plurality of detectors. After the line images are aligned with each other in correspondence with the subject, when the X-ray images are connected,
At the time of alignment of the read X-ray image, an image obtained by subjecting at least one of the X-ray images to enlargement interpolation processing or reduction interpolation processing is used, and when the X-ray images are connected, the X-ray image is used. A medical image processing system.   The medical image processing system according to claim 6, wherein enlargement interpolation processing or reduction interpolation processing is performed on the X-ray images so that the imaging magnifications of the X-ray images are the same.   The medical image processing according to claim 7, wherein an imaging magnification of the X-ray image is the same as an imaging magnification of an X-ray image of a detector arranged at a center among the plurality of detectors. system.   8. The medical image according to claim 7, wherein an imaging magnification of the X-ray image is the same as an imaging magnification of an X-ray image of a detector closest to the subject among the plurality of detectors. Processing system.   Alignment is performed so that overlapping image portions of the respective X-ray images having the same imaging magnification by the enlargement interpolation process or the reduction interpolation process coincide, and the connection of the X-ray images is performed based on the result of the alignment. The medical image processing system according to any one of claims 7 to 9, wherein:

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