JP2014117307A - Radiation image processor, radiation image processing method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extract an irradiation field area from a radiation image with high accuracy.SOLUTION: A radiation image processor 3 includes a control part (setting means, calculation means, and determination means) 31 setting an area designation frame for designating an area in a radiation image based on radiation image data, calculating energy defined as a difference amount between an inner evaluation value calculated from inner radiation image data of the area designation frame and an outer evaluation value calculated from outer radiation image data of the area designation frame at a plurality of points on the radiation image while moving the area designation frame set in the radiation image, setting a size and a position of the area designation frame on the basis of the value of the calculated energy in the case that the total sum of the calculated energy at the plurality of points on the radiation image satisfies a preset predetermined condition, and determining an area included by the area designation frame as an irradiation field inclusion area.

Description

  The present invention relates to a radiation image processing apparatus, a radiation image processing method, and a program.

Conventionally, as a technique for extracting an irradiation field region of a radiographic image obtained by imaging a diagnosis target region, for example, Patent Literature 1 discloses a method in which a radiographic image is divided into small regions, and a region having a high signal dispersion value in the small region. A technique for extracting an irradiation field region by considering that it includes a boundary between the irradiation field region and the irradiation field stop (the contour of the irradiation field region) is disclosed.
In general, such a technique for extracting an irradiation field region of a radiographic image is based on the assumption that a diagnosis target region is set to be the center of an X-ray detector, and is caused by, for example, the shape of a human body. For a radiographic image having a plurality of straight line portions or the like, it is determined that an edge outside the image is an irradiation field edge.

Japanese Patent No. 3239186

By the way, in recent years, in a relatively small medical facility or the like, there is a tendency that all diagnostic target parts are imaged by one size X-ray detector such as a large FPD (Flat Panel Detector).
However, when imaging all the diagnostic target parts with one size X-ray detector, depending on the diagnostic target part, it may not be set to be the center of the X-ray detector, and the accurate irradiation field cannot be determined. there were. When accurate irradiation field determination cannot be performed, there arises a problem that appropriate image processing conditions cannot be set as a result.
Here, FIG. 15A shows an example of a radiographic image taken without setting the irradiation field at the center, and FIG. 15B shows an example of a histogram of signal values obtained from this image. In FIG. 15B, the horizontal axis represents the signal value (pixel signal value), and the vertical axis represents the frequency (number of pixels) of each signal value.
As shown in FIG. 15 (a), when the radiation field is captured at one end portion of the radiographic image, the area outside the irradiation field is large. Therefore, as shown in FIG. 15 (b), the signal value from this image In the histogram, the frequency of the signal value corresponding to the irradiation field region becomes too high, and it becomes difficult to analyze the histogram for calculating the gradation processing condition, resulting in a gradation processing condition that cannot be diagnosed.

  An object of the present invention is to provide a radiation image processing apparatus, a radiation image processing method, and a program capable of accurately extracting an irradiation field region from a radiation image.

The invention described in claim 1
A radiographic image processing apparatus that performs image processing on radiographic image data obtained by radiographing a region to be diagnosed as a subject,
Setting means for setting a region designation frame for designating a region for a radiation image based on the radiation image data;
While moving the region designation frame set for the radiographic image, at a plurality of points on the radiographic image, the inner evaluation value obtained from the radiation image data inside the region designation frame and the region designation frame A calculation means for calculating energy defined as a difference amount of the outer evaluation value obtained from the outer radiation image data;
When the sum of energy at a plurality of points on the radiographic image calculated by the calculating means satisfies a predetermined condition set in advance, the size of the region designation frame based on the value of energy calculated by the calculating means Determining means for setting the position and determining the region included in the region designation frame as an irradiation field inclusion region;
It is characterized by providing.

The invention according to claim 2 is the radiographic image processing apparatus according to claim 1,
The inner evaluation value is a statistical value reflecting an average radiation dose in the radiation image data inside the area designation frame.

The invention according to claim 3 is the radiographic image processing apparatus according to claim 2,
The area designation frame is rectangular,
The statistical value reflecting the average dose of radiation is an average value of a luminance signal corresponding to the radiation dose.

Moreover, invention of Claim 4 is set in the radiographic image processing apparatus as described in any one of Claims 1-3,
The outer evaluation value is a statistical value reflecting a dose in a region where the radiation dose in the radiographic image data is relatively high in the region outside the region designation frame.

The invention according to claim 5 is the radiographic image processing apparatus according to claim 4,
The area designation frame is rectangular,
The statistical value reflecting the dose in a region where the radiation dose is relatively high is a maximum value or a minimum value of a luminance signal corresponding to the radiation dose.

Moreover, invention of Claim 6 is a radiographic image processing apparatus as described in any one of Claims 1-5,
The setting means includes
If the sum of energy at a plurality of points on the radiographic image calculated by the calculation means does not satisfy the predetermined condition, change the size of the region specification frame, set a region specification frame of a new size,
The computing means is
The energy is calculated at a plurality of points on the radiographic image while moving the area specifying frame of the new size with respect to the radiographic image.

The invention according to claim 7 is the radiographic image processing apparatus according to claim 6,
The determining means includes
When the sum of energy at a plurality of points on the radiographic image calculated by the calculation means does not satisfy the predetermined condition, and the setting of the area designation frame of the new size by the setting means is not made,
The entire radiation image is determined as an irradiation field inclusion region.

Moreover, invention of Claim 8 is a radiographic image processing apparatus as described in any one of Claims 1-7,
Irradiation field recognition means for recognizing the irradiation field by detecting the edge of the irradiation field for the irradiation field inclusion region determined by the determination means is further provided.

The invention according to claim 9 is
A radiographic image processing method for radiographic image data obtained by radiographing a region to be diagnosed as a subject,
A setting step for setting a region designation frame for designating a region for a radiation image based on the radiation image data;
While moving the region designation frame set for the radiographic image, at a plurality of points on the radiographic image, the inner evaluation value obtained from the radiation image data inside the region designation frame and the region designation frame A calculation step of calculating energy defined as a difference amount of the outer evaluation value obtained from the outer radiation image data;
When the sum of energy at a plurality of points on the radiographic image calculated by the calculation step satisfies a predetermined condition set in advance, the size of the region designation frame based on the value of energy calculated by the calculation step Determining the position, and determining the region included in the region designation frame as an irradiation field inclusion region,
It is characterized by having.

The program of the invention according to claim 10 is:
A computer that performs image processing on radiographic image data obtained by radiographing a diagnostic target part as a subject,
Means for setting a region designation frame for designating a region for a radiation image based on the radiation image data;
While moving the region designation frame set for the radiographic image, at a plurality of points on the radiographic image, the inner evaluation value obtained from the radiation image data inside the region designation frame and the region designation frame Means for calculating energy defined as a difference amount of an outer evaluation value obtained from outer radiation image data;
When the calculated sum of energy at a plurality of points on the radiation image satisfies a predetermined condition set in advance, the size and position of the region designation frame are set based on the calculated energy value, and the region Means for determining an area included in the designated frame as an irradiation field included area;
To function as.

  According to the present invention, it is possible to accurately extract an irradiation field region from a radiographic image.

It is a block diagram which shows the system configuration | structure of the system in a facility in embodiment of this invention. It is a block diagram which shows the functional structure of the radiographic image processing apparatus of FIG. It is a figure which shows an example of the image information table of image DB of FIG. It is a figure which shows an example of the viewer screen displayed on the display part of FIG. It is a figure which shows the flowchart of an irradiation field inclusion area | region setting process. It is an example which shows the state which set the rectangle on the original image. It is a figure for demonstrating the preferable calculation method of an inner side evaluation value. It is a figure for demonstrating the preferable calculation method of an outer side evaluation value. It is a figure for demonstrating an inner side evaluation value and an outer side evaluation value. It is a figure for demonstrating an inner side evaluation value, an outer side evaluation value, and energy. It is an example which plotted energy. It is a figure for demonstrating the setting method of the size and position of a rectangle. It is a figure for demonstrating the setting method of the size and position of a rectangle when there is no irradiation field area | region. It is a figure for demonstrating the effect of an irradiation field inclusion area | region setting process. It is a figure for demonstrating the conventional problem.

  Embodiments of the present invention will be described below with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

[Configuration of in-facility system 1]
FIG. 1 is a block diagram showing a system configuration of an in-facility system 1 to which the radiation image processing apparatus 3 according to the present embodiment is applied.
The in-facility system 1 is a small-scale diagnosis system applied to a relatively small-scale medical facility such as a practitioner or a clinic.

As shown in FIG. 1, the in-facility system 1 includes a modality 2, a radiation image processing device 3, a receiving device 4, an imager 5, a general-purpose printer 6, and a client PC (Personal Computer) 7.
Each device constituting the in-facility system 1 is connected to a communication network (hereinafter simply referred to as “network”) 8 such as a LAN (Local Area Network) via a switching hub (not shown), for example.
Of these, the radiation image processing apparatus 3 is preferably a WS (workstation) provided in an examination room where a doctor is resident. The WS that operates as the radiation image processing apparatus 3 may control the activation of the modality, the processing conditions, and the like.

  In general, DICOM (Digital Image and Communications in Medicine) standard is used as a communication method in a hospital, and DICOM MWM (Modality Worklist Management) and DICOM MPPS (DICOM MPPS) are used for communication between devices connected to a LAN. Modality Performed Procedure Step) is used. Note that the communication method applicable to this embodiment is not limited to this.

[Device configuration of each device of the in-facility system 1]
Hereinafter, each apparatus which comprises the in-facility system 1 is demonstrated.

Modality 2 captures a radiographic image or the like of a patient's diagnosis target region, converts the captured image into digital data, and generates digital data of a medical image such as a radiographic image used for diagnostic interpretation Device.
In the present embodiment, the modality 2 is a DR (Digital Radiography) apparatus configured to include an X-ray imaging apparatus, an FPD (Flat Panel Detector), and the like.
The FPD is an X-ray detector that converts X-ray energy irradiated through a subject into an electric signal and acquires an X-ray transmission image.

  In the present embodiment, the modality 2 has a function of assigning image attribute information such as UID, imaging date / time, examination ID, and examination site to each radiation image in a format conforming to the DICOM standard. That is, a radiation image is input from the modality 2 to the radiation image processing apparatus 3 in a state where these pieces of image attribute information are given. The UID is a unique ID for specifying a radiation image in the in-facility system 1.

The modality 2 includes an input unit (not shown) such as a keyboard having character input keys, numeric input keys, and the like, and patient information for specifying a patient to be imaged is input from the input unit. . Patient information broadly includes, for example, information specifying a patient such as patient ID, patient name (kanji), patient name (kana), patient name (ASCII), gender, date of birth, and age.
Note that it is not necessary to input all of these in the modality 2, and only a part of the patient information may be input. In addition, when the modality 2 has a specification for inputting only the patient ID as patient information, the input unit of the modality 2 may be a numeric keypad, for example.

  The image attribute information and the patient information are incidental information attached to the radiation image generated by the modality 2. The modality 2 generates a radiographic image in a DICOM file format conforming to the DICOM standard, and transmits the generated radiographic image to the radiographic image processing device 3 via the network 8. At this time, the DICOM file is composed of an image portion and a header portion. Image data of the radiographic image is written in the image portion, and supplementary information related to the radiographic image is written in the header portion.

The radiographic image processing apparatus 3 is installed in an examination room, for example.
The radiological image processing apparatus 3 associates the radiographic image generated by the modality 2 with the patient information and stores it in the image DB (database) 331 and stores it in the storage unit 33, or the doctor displays the image or the like and interprets the interpretation. Or a device having a higher definition than a monitor (display unit) used in a general PC.

FIG. 2 is a block diagram showing a functional configuration of the radiation image processing apparatus 3.
As shown in FIG. 2, the radiation image processing apparatus 3 includes a control unit 31, a RAM (Random Access Memory) 32, a storage unit 33, an operation unit 34, a display unit 35, a communication unit 36, a media drive 37, and the like. Each part is connected by a bus 38.

  The control unit 31 includes a CPU (Central Processing Unit) (not shown) and the like, reads various programs such as a system program and a processing program stored in the storage unit 33, expands them in the RAM 32, and will be described later according to the expanded programs. Various processes including a diagnostic image creation process are executed.

The RAM 32 is a work area that temporarily stores various programs, input or output data, parameters, and the like that can be executed by the control unit 31 read from the storage unit 33 in various processes controlled by the control unit 31. Function.
The RAM 32 stores the patient information list received from the receiving device 4.

  The storage unit 33 includes an HDD (Hard Disk Drive), a semiconductor nonvolatile memory, or the like. In addition to storing various programs as described above, the storage unit 33 stores image processing parameters (gradation curves used for gradation processing) used to adjust a radiographic image to an image quality suitable for diagnosis. The defined look-up table and the like are stored.

The storage unit 33 includes an image DB 331, an area designation frame storage unit 332, and the like.
The image DB 331 is a database for storing various images.
Examples of the various images include a radiation image (also referred to as an original image) transmitted from the modality 2, a diagnostic image generated from the original image, and a thumbnail image generated from the original image.
Here, the original image is stored in the image DB 331 in a state where image processing is not performed on the radiation image received from the modality 2. The diagnostic image is an image used when a doctor performs interpretation diagnosis or informed consent for a patient, and the original image is subjected to predetermined image processing (for example, diagnostic image creation processing described later). It is an image of a state. The diagnostic image can be overwritten with an image-processed image when further image processing is performed by a doctor's operation.

  The image DB 331 has an image information table 331a for storing various information related to images stored in the image DB 331.

FIG. 3 shows an example of the image information table 331a.
As shown in FIG. 3, the image information table 331a includes a “record number” field, a “UID” field, an “imaging date” field, an “examination ID” field, an “examination site” field, a “patient ID” field,. A “original image” field, a “diagnosis image” field, a “thumbnail image” field, and the like. In the image information table 331a, information on these fields is stored in association with each other as one record.
The “original image” field is a field for storing information indicating the file storage location of the original image. The “diagnostic image” field stores information indicating a file storage location of the diagnostic image. The “thumbnail image” field is a field for storing information indicating the file storage location of the thumbnail image.
When an image is stored in the image DB 331, each information is also stored in the image information table 331a.
Based on the information stored in the image information table 331a, the original image, the diagnostic image, and the thumbnail image are associated with the patient information and the UID for identifying the image, and the patient information, the imaging date, etc. can be searched as key information. It becomes.

The area designation frame storage unit 332 stores an area designation frame for designating an area of a predetermined size for the original image in the irradiation field inclusion area setting process described later. The region designation frame is, for example, a plurality of types (for example, 18 types) of rectangular frames (hereinafter, referred to as rectangles R (R ₁ , R ₂ ...)). Their sizes (areas) are different from each other.

  The operation unit 34 includes a keyboard having cursor keys, numeric input keys, various function keys, and the like, and a pointing device such as a mouse. The operation unit 34 outputs, to the control unit 31, a key depression signal or a mouse operation signal that has been depressed with the keyboard.

  The display unit 35 includes, for example, a monitor such as a CRT (Cathode Ray Tube) or an LCD (Liquid Crystal Display). The display unit 35 displays various screens according to instructions of display signals input from the control unit 31.

FIG. 4 is a diagram illustrating an example of the viewer screen 351 displayed on the display unit 35.
The viewer screen 351 is a patient to be diagnosed by the operation unit 34 from the patient list screen displayed on the display unit 35 by the predetermined operation of the operation unit 34 (the screen on which the patient information list transmitted from the receiving device 4 is displayed). For example, it is used to display a diagnostic image when a doctor performs interpretation diagnosis or informed consent for a patient.

  On the viewer screen 351, as shown in FIG. 4, for example, an image display field 351a for displaying an image, an image capture button 351b, various tool buttons 351d, a print button 351e, a patient display field 351f, a thumbnail display field 351g. A display image selection field 351h and the like are provided.

  The image display column 351a is a column for displaying an original image, a diagnostic image, a past image of the same patient, and the like captured from the modality 2.

  The image capture button 351b is a button for instructing to capture an original image transmitted from the modality 2 as an image of a patient who is currently a diagnosis target (a patient displayed in the patient display field 351f). When the image capture button 351b is pressed, the modality 2 is displayed until the image capture button 351b is pressed next to cancel capture or the viewer screen 351 is closed or transitions to another screen. The original image received from is captured as an image of the patient currently being diagnosed.

The various tool buttons 351d are buttons for performing image processing such as density contrast adjustment processing and image quality adjustment processing on the displayed radiation image, for example. When a button of a desired item of the tool button 351d is pressed, an input field, a button, a toolbar, or the like corresponding to the item is displayed. When an input to the displayed input field or an operation of a button or a toolbar is performed by the operation unit 34, processing corresponding to the operation is performed on the displayed image. For example, when the density contrast button is pressed, a slide bar for density adjustment, a slide bar for contrast adjustment, and the like are displayed. When the slide bar is operated by the operation unit 34, the control unit 31 sets the density and contrast according to the operation. The image displayed in the image display field 351a is adjusted.
When a doctor interprets a diagnostic image displayed in the image display field 351a of the viewer screen 351 and makes a diagnosis, the doctor can operate the tool button 351d to adjust the image quality to a desired level.

  The print button 351e is a button for instructing to print the selected image from the general-purpose printer 6.

  The patient display column 351f is a column for displaying patient information of a patient currently selected as a diagnosis target.

  The thumbnail display field 351g is a field for displaying a thumbnail image of a radiation image (including images taken in the past) of the same patient in order to select a radiation image to be displayed in the image display field 351a.

  The display image selection column 351h is a column for selecting the classification (for example, by date, by modality, etc.) of images to be displayed in the thumbnail display column 351g.

  The communication unit 36 is configured by a network interface or the like, and transmits / receives data to / from an external device connected to the network 8 via a switching hub.

  The media drive 37 is configured such that a portable recording medium M such as a CD-R (Compact Disk Recordable), a DVD-R (Digital Versatile Disk Recordable), or an MO (Magnet Optical) disk is detachable. A device that reads or writes data from and to M.

  The reception device 4 is a computer device for performing registration, accounting, insurance score calculation, etc. of patients who come to the hospital. , A display unit configured by a CRT, an LCD, and the like, a communication unit (none of which is shown) that controls communication with each device connected to the network 8, and the like. When receiving a reception input screen is instructed from the input unit, the reception device 4 displays a reception input screen (not shown) (not shown) on the display unit in cooperation with the CPU and the program stored in the storage unit. . When reception information (reception number, patient name, etc.) is input by the input unit via this reception input screen, a patient information list of the received patients is created (updated) and stored in the storage unit, and the communication unit It transmits to the image display device 3 as appropriate.

  The imager 5 records a latent image by laser exposure on a transmission type recording medium (film) based on the radiation image transmitted from the image display device 3, and visualizes the latent image by thermal phenomenon processing. Printer.

  The general-purpose printer 6 is a printer that records an image on a reflective recording medium (paper medium, sticker, or the like) by an inkjet method or a laser method.

  The client PC 7 is, for example, a computer device that displays a radiation image transmitted from the radiation image processing device 3.

[Flow of inspection using in-facility system 1]
Next, examination flows (1) to (5) in the medical facility where the in-facility system 1 is installed will be described.
(1) First, a patient is accepted at the reception. The received patient information of the patient is input by the receiving device 4, and a patient information list including this patient information is transmitted to the radiation image processing device 3. In the radiation image processing apparatus 3, the patient information list transmitted from the reception apparatus 4 is stored in the RAM 32.
(2) Next, in the examination room, examinations and necessary examination decisions are made. The examination is performed by an inquiry, a patient's past medical record, browsing of images and reports, and the like.
(3) Next, in the imaging room, X-ray imaging of the affected part (imaging target site) of the patient is performed by the modality 2. Here, as will be described later, the radiological image processing apparatus 3 is capable of creating a diagnostic image suitable for interpretation regardless of the size of the imaging target region of the patient as the subject. Therefore, the modality 2 can perform shooting under fixed shooting conditions without performing individual adjustments during shooting.
(4) After X-ray imaging, an original image obtained by imaging is taken into the radiation image processing apparatus 3, and a diagnostic image creation process described later is performed and output.
(5) Diagnosis and treatment are performed based on the output diagnostic image.

[Operation of Radiation Image Processing Device 3]
Next, the operation of the radiation image processing apparatus 3 will be described.

The radiation image processing apparatus 3 in the present embodiment executes diagnostic image creation processing.
In the modality 2, no particular adjustment is performed at the time of each shooting, and shooting is performed under fixed shooting conditions. Therefore, the original image varies depending on the variation of the irradiation X-ray dose due to the difference in the affected part (imaging target part) of the patient or the change in the apparatus characteristics of the modality 2. However, if there are variations in the images to be interpreted, stable interpretation diagnosis cannot be performed. Therefore, in the radiation image processing apparatus 3, in order to stably output an image suitable for interpretation, diagnostic image creation processing is executed, and image processing is performed on the original image to satisfy a predetermined standard. Create diagnostic images. The doctor can confirm whether the imaging has been successful (whether re-imaging is necessary) by displaying a diagnostic image in the image display field 351a of the viewer screen 351 and observing it.

Hereinafter, the diagnostic image creation process will be described in detail.
As a premise of such diagnostic image creation processing, the viewer screen 351 for the patient to be diagnosed is displayed on the display unit 35, and the image capture button 351 b of the viewer screen 351 is pressed by the operation unit 34, and the modality 2 is displayed. The original image obtained by the imaging performed in this way is captured, associated with the patient information of the patient selected on the patient list screen, and stored in the image DB 331.

  Specifically, as the diagnostic image creation processing, irradiation field inclusion region setting processing, irradiation field recognition processing, gradation conversion processing, and the like are executed.

<Irradiation field inclusion area setting process>
The irradiation field inclusion area setting process is executed on the input original image.
The irradiation field refers to an area where X-rays have reached through the subject. In the irradiation field inclusion area setting process, an approximate area including the irradiation field in the original image is determined.
This is because the position of the irradiation field in the original image is not necessarily the center of the image when imaging various affected parts (imaging target part) of a patient using one type of fixed-size FPD, This is done in view of the various sizes of the irradiation field. After recognizing the general area including the irradiation field in the original image, various image processing (irradiation field recognition processing, gradation conversion processing) is performed thereafter. Etc.) can be performed appropriately.

FIG. 5 shows a flowchart of the irradiation field inclusion region setting process.
The irradiation field inclusion region setting process is executed in cooperation with the control unit 31 and the program stored in the storage unit 33.
The control unit 31 functions as a setting unit, a calculation unit, and a determination unit by executing the irradiation field inclusion region setting process.

First, in step S1, the control unit 31 sets a rectangle R having a predetermined size in the original image.
Specifically, the control unit 31 still includes the irradiation field inclusion region for the image among the plurality of types of rectangles R (R ₁ , R ₂ ...) Stored in the region designation frame storage unit 332 of the storage unit 33. A rectangle R that is not used in the setting process and has the smallest size (area) is selected and set to the start position on the original image (see the solid line portion in FIG. 6).
The start position is an arbitrary position on the original image where the rectangle R is initially set when the irradiation field inclusion region setting process is executed. For example, the position where the upper left corner of the rectangle overlaps the upper left corner of the original image, etc. It is.

  Next, in step S2, the control unit 31 moves the rectangle R set in step S1 on the original image (see the two-dot chain line portion in FIG. 6), and at a plurality of points on the original image, the rectangle R Energy defined as a difference amount between the inner evaluation value obtained from the radiation image data inside R and the outer evaluation value obtained from the radiation image data outside the rectangle R is calculated.

Here, when the i-th rectangle among a plurality of types of rectangles R is R _i and the position of the rectangle on the original image is r = (x, y), the above-described difference amount (energy E (R _i , r )) Is expressed by the following equation (1).

At this time, the inner evaluation value (I (R _i , r)) is a statistic that reflects the average dose of radiation in the radiographic image data inside the rectangle R. Specifically, the radiation dose inside the rectangle R Is the average value of the luminance signal corresponding to.
When the inner evaluation value is the average value of the luminance signal corresponding to the radiation dose inside the rectangle R, a known moving average filter (also referred to as an averaging filter or a smoothing filter) process or the like can be applied. Can be speeded up.

Here, the moving average filter process will be described. The moving average filter processing is a method of averaging the luminance values using the luminance values around the target pixel to obtain the luminance value of the processed image.
For example, as shown in FIG. 7A, in the case of a moving average filter having a kernel size of 5 × 5, 5 × 5 luminance values around the pixel of interest are summed, and the total luminance value is calculated as the number of pixels. This process is executed for all the pixels while raster scanning the process of dividing by (5 × 5 = 25).
At this time, when the process moves to the adjacent pixel, as shown in FIG. 7B, the calculation process of the sum of the brightness values has a portion overlapping the calculation process of the sum of the brightness values of the previous pixels. Therefore, when processing with the previous pixel, the total luminance value is retained, and the luminance value for the leftmost column of the previous kernel is subtracted from the total luminance value of the previous pixel, and the next kernel When the luminance values for the rightmost column are added, the total value of the luminance values in the next kernel can be obtained.
Therefore, in the above example, 25 total additions of the luminance values in the kernel were added, and the processing can be performed with a total of 10 calculations of 5 subtractions and 5 additions. Become. Note that this effect increases as the kernel size increases.
Furthermore, if the configuration is such that the total value of the luminance values for one line of the image is held, the same processing can be executed in the vertical direction, so that higher speed can be expected.
Of course, it is possible to calculate the average value without applying the above moving average filter processing.

Further, the outer evaluation value (O (R _i , r)) is a statistic that reflects a dose in a region where the radiation dose in the radiographic image data outside the rectangle R is relatively higher than other regions in the entire region. Specifically, it is the maximum value of the luminance signal corresponding to the radiation dose outside the rectangle R.
In addition, when the outer evaluation value is the maximum value of the luminance signal corresponding to the radiation dose outside the rectangle R, the following method can be applied, so that the processing can be speeded up.
First, as shown in FIG. 8A, the original image is scanned in the vertical direction to obtain the maximum value of the luminance value, and this is performed for each predetermined column (for example, a column for each pixel). Ask for a profile. Further, the original image is scanned in the horizontal direction to obtain the maximum value of the luminance value, and this is performed for each predetermined row (for example, row for each pixel) to obtain the maximum value profile.
Thereafter, as shown in FIG. 8B, after removing the portion where the rectangle R exists from the obtained profile, the maximum value of the remaining profile value is obtained. This is the maximum value of the luminance signal outside the rectangle R. It is.

As shown in FIG. 9, the inner evaluation value becomes higher as the ratio of the irradiation field P1 in the rectangle R is higher, and the outer evaluation value is lowest when there is no irradiation field P1 region outside the rectangle R. Value.
Therefore, as shown in FIG. 10A, when the difference between the inner evaluation value and the outer evaluation value is 0 or more, there is a high possibility that the rectangle R surrounds the irradiation field P1, and FIG. As shown, when the difference between the inner evaluation value and the outer evaluation value is lower than 0, there is a high possibility that the rectangle R does not surround the irradiation field P1.

When the rectangle R is set at the start position on the original image in step S1, the control unit 31 first calculates the energy E (R _i , r) as described above at the position, and then calculates the rectangle R. A predetermined distance is moved, and energy E (R _i , r) is calculated in the same manner at the position after the movement. The control unit 31 repeats this operation, and calculates energy E (R _i , r) at a plurality of points on the original image while moving the rectangle R over the entire surface of the original image.

FIG. 11 shows an example in which the energy E (R _i , r) obtained at a plurality of points on the original image is plotted.
FIG. 11 shows an example of a three-dimensional profile obtained when the rectangle R includes the irradiation field P1 in the central portion of the original image. Since the energy E (R _i , r) is a difference amount between the inner evaluation value and the outer evaluation value, when there is a position where the rectangle R includes the irradiation field P1, as shown in FIG. 11, the energy E (R A profile showing a strong peak of _i , r) can be obtained.

Next, in step S3, the control unit 31 obtains the sum of the energy E (R _i , r) obtained at a plurality of points on the original image in step 2 and sums the energy E (R _i , r). Is greater than or equal to a preset threshold value.
The threshold value is a value set in advance in consideration of the radiation intensity at the time of image capturing.
Further, in obtaining the sum of the energy E (R _i , r), the minimum value of energy is set to zero.

And when it is judged that the sum total of energy is more than a preset threshold value (step S3: YES), in following step S4, the control part 31 of energy E ( _Ri , r) calculated by said step S2 is carried out. The size and position of the rectangle R are set based on the values, the irradiation field inclusion region that includes the irradiation field is determined, and the present process is terminated.

  Here, as a method of setting the size and position of the rectangle R, for example, either a method of setting by energy weighted average or a method of setting from the maximum energy value can be used.

なお、かかる方法の利点としては、例えば以下の点が挙げられる。
本処理においては、オリジナル画像に対して矩形Ｒの小さいものから順にエネルギーを演算していくため、エネルギー総和がほぼ閾値であるにも関わらず閾値を越えない矩形Ｒがあった場合に、次のサイズの矩形Ｒを用いた演算が実行される。このとき、上記のように重み付け平均をとることで、エネルギー総和が閾値をぎりぎりで越えない矩形Ｒのサイズが考慮された矩形Ｒのサイズを設定することができる。また、矩形Ｒの中央部がちょうど照射野の中央部に位置するように矩形Ｒの位置を設定することができる。
制御部３１は、このようにしてサイズ及び位置の設定された矩形Ｒにより包含されるオリジナル画像上の領域を、照射野包含領域として決定する。 First, a method of setting by energy weighted average will be described.
FIG. 12A shows an example of a graph obtained when the position of the rectangle R on the original image is the horizontal axis and the energy obtained at each position is the vertical axis. In addition, when referring to such a graph, a region where all peaks are added (the hatched portion in FIG. 12A) indicates the sum of energy E (R _i , r).
As shown in FIG. 12A, when the sum of the energy E (R _i , r) exceeds the threshold, the control unit 31 determines that the value of the energy E (R _i , r) is in accordance with the following equation (2). Weighting is performed so that larger rectangles are more important, and the size of the rectangle R is set by taking the average of the sizes of the rectangle R used in the processing so far. Further, according to the following formula (3), weighting is performed so that the position where the value of the energy E (R _i , r) is larger is emphasized, and the average of the positions of the rectangle R used in the processing so far is taken to obtain the rectangle. Set the position of R.

In addition, the following points are mentioned as an advantage of this method, for example.
In this process, energy is calculated in order from the smallest rectangle R with respect to the original image. Therefore, when there is a rectangle R that does not exceed the threshold even though the energy sum is almost the threshold, An operation using the size rectangle R is executed. At this time, by taking the weighted average as described above, it is possible to set the size of the rectangle R in consideration of the size of the rectangle R whose energy sum does not exceed the threshold. Further, the position of the rectangle R can be set so that the center portion of the rectangle R is located exactly at the center portion of the irradiation field.
The control unit 31 determines an area on the original image that is included by the rectangle R having the size and position set as the irradiation field inclusion area.

かかる方法の利点としては、矩形Ｒのサイズ及び位置の設定のために行う演算処理が簡単であるため、処理を高速化できる点が挙げられる。
制御部３１は、このようにしてサイズ及び位置の設定された矩形Ｒにより包含されるオリジナル画像上の領域を、照射野包含領域として決定する。 Next, a method for setting from the maximum energy value will be described.
FIG. 12B shows an example of a graph obtained when the position of the rectangle R on the original image is the horizontal axis and the energy obtained at each position is the vertical axis. In addition, when referring to such a graph, a region where all peaks are added (the hatched portion in FIG. 12B) indicates the sum of energy E (R _i , r).
As shown in FIG. 12B, when the sum of the energy E (R _i , r) exceeds the threshold, the control unit 31 determines that the value of the energy E (R _i , r) is in accordance with the following equation (4). The size of the rectangle R is set by the rectangle R indicating the maximum value (that is, the rectangle R in which the value of the energy E (R _i , r) indicates the maximum value among the rectangles R used in the processing so far) The position of the rectangle R is set according to the position where the rectangle R shows the maximum value.

An advantage of such a method is that the arithmetic processing performed for setting the size and position of the rectangle R is simple, so that the processing speed can be increased.
The control unit 31 determines an area on the original image that is included by the rectangle R having the size and position set as the irradiation field inclusion area.

  If it is determined in step S3 that the total energy is not equal to or greater than a preset threshold value (step S3: NO), the control unit 31 stores the area designation frame storage unit 332 in the storage unit 33 in the subsequent step S5. It is determined whether or not there is a rectangle R (another rectangle candidate) that has not yet been used in the main irradiation field inclusion region setting process. If it is determined that there is a rectangle R (step S5: YES), the process returns to step S1. Repeat the subsequent steps.

  On the other hand, when it is determined that there is no rectangle (step S5: NO), in the subsequent step S6, the control unit 31 sets the rectangle R to the entire screen (that is, sets the entire screen as the irradiation field inclusion region), The process ends.

Here, FIG. 13 shows an example of an image having no irradiation field.
As shown in FIG. 13, the energy sum does not exceed the threshold value in an image without an irradiation field. Accordingly, in step S3, the energy calculation using all types of rectangles R stored in the region designation frame storage unit 332 is completed without the total energy exceeding the threshold value. At this time, the control unit 31 sets the entire image as an irradiation field inclusion region. That is, the control unit 31 recognizes that the image having no irradiation field is a full irradiation field, and does not set the irradiation field inclusion region in the original image.

Thus, according to the irradiation field inclusion region setting process, it is possible to determine the approximate region including the irradiation field in the original image.
Here, FIG. 14A shows an example of a radiographic image taken without setting the irradiation field at the center, and FIG. 14B shows a case where the irradiation field inclusion region setting process is performed on this image. An example of the histogram of the signal value obtained is shown. In FIG. 14B, the horizontal axis represents a signal value (pixel signal value), and the vertical axis represents the frequency (number of pixels) of each signal value.
As shown in FIG. 14A, when the irradiation field inclusion region P2 surrounding the irradiation field P1 is set even when the irradiation field P1 is biased at one end of the original image, as shown in FIG. The frequency peak corresponding to the outdoor region can be reduced. That is, in the irradiation field inclusion region setting process, even when the irradiation field P1 is biased at one end of the original image, the bias of the irradiation field position can be eliminated in a pseudo manner.

<Irradiation field recognition processing>
The irradiation field recognition process is applied to the irradiation field inclusion region set as described above.
In this irradiation field recognition process, the irradiation field area in the irradiation field inclusion area set as described above is further discriminated from the irradiation field outside area (an area other than the irradiation field). This is effective when the above-described irradiation field inclusion region setting process is executed for a relatively small number of points on the original image. That is, from the viewpoint of processing speed, when the irradiation field inclusion region setting process is executed at relatively few points on the original image, it is conceivable that the irradiation field inclusion region becomes larger than the irradiation field. Therefore, the irradiation field inclusion region can be brought close to the irradiation field by further executing the irradiation field recognition process on such an irradiation field inclusion region.
The control unit 31 functions as irradiation field recognition means by executing irradiation field recognition processing.

  Any known method of irradiation field recognition may be employed. For example, as disclosed in Japanese Patent Application Laid-Open No. 5-7579, an original image is divided into a plurality of small areas, a variance value is obtained for each divided area, and an irradiation field area is determined based on the obtained variance value. Also good. Usually, since the reaching X-ray dose is substantially uniform in the irradiation field region, the dispersion value of the small region becomes small. On the other hand, in a small region including the edge of the irradiation field region, a portion having a large arrival X-ray dose (outside the irradiation field region) and a portion (irradiation field region) in which the arrival X-ray dose is somewhat reduced by the subject are mixed, and thus the variance value is growing. Therefore, assuming that an edge is included in a small region having a variance value greater than a certain value, the region surrounded by such a small region is determined as an irradiation field region.

<Area of interest setting and reference signal value setting>
When the irradiation field inclusion region (or irradiation field region) is thus determined, a region of interest (hereinafter referred to as ROI: Region Of Interest) is set from this region. At this time, the reference signal value is set together with the ROI setting.

  For example, the ROI can be specified based on the signal value profile by sequentially scanning the horizontal direction and the vertical direction of the original image to create a signal value profile in each direction. Further, the ROI may be specified by pattern matching, and any method may be applied.

  Then, a histogram of the signal values of the specified ROI region is created, and the signal values having a predetermined frequency from the maximum value side and the minimum value side in the histogram are determined as the maximum reference value H and the minimum reference value L, respectively. To do. The maximum reference value H and the minimum reference value L are used as reference values when the signal value range of the original image is converted into the signal value range (maximum value SH, minimum value SL) in the diagnostic image.

<Tone conversion processing>
Further, after the above processing is completed, gradation conversion processing is applied.
The gradation conversion process is a process for adjusting the density and contrast of the original image. When a doctor diagnoses the presence or absence of a human body structure disease by interpretation of an X-ray image, the presence or absence of the disease is determined based on the density and contrast (gradation) of the structure on the X-ray image. Therefore, by adjusting the density and contrast suitable for interpretation, a doctor's disease detection operation can be supported.

The gradation conversion processing is performed in two stages: (1) normalization processing and (2) conversion processing using a basic LUT (lookup table), and finally a signal value range predetermined as a diagnostic image, Gradation conversion is performed so as to obtain gradation characteristics.
Conventionally, since a screen / film method has been adopted for photographing, input signal (reading signal) conversion processing is performed with a target of gradation characteristics (contrast) cultivated by the screen / film method. The gradation characteristic obtained by the screen / film system is an S-shaped curve. In the gradation conversion processing, an LUT indicating this gradation characteristic is prepared as a basic LUT for each part, and after performing individual signal adjustment on the original image by normalization processing, the signal value is calculated using this basic LUT. Perform conversion.

  Thus, a diagnostic image is created by performing the above-described various image processes on the original image.

As described above, according to the present embodiment, the radiographic image processing device 3 sets the rectangle R that designates a region for the original image based on the radiographic image data, and the rectangle R set for the original image. Is defined as the difference between the inner evaluation value obtained from the radiation image data inside the rectangle R and the outer evaluation value obtained from the radiation image data outside the rectangle R at a plurality of points on the original image. When the energy is calculated and the sum of the energy at a plurality of points on the calculated original image satisfies a predetermined condition set in advance, the size and position of the rectangle R are set based on the calculated energy value, A control unit 31 is provided that determines an area included in the rectangle R as an irradiation field included area.
For this reason, for each original image, a rectangle R having a size and a position corresponding to the irradiation field of the original image is set, and an area surrounded by the rectangle R on the original image is an irradiation field inclusion region including the irradiation field. Will be determined.
Therefore, an appropriate irradiation field area can be extracted from the radiation image.

Further, according to the present embodiment, the inner evaluation value is a statistical value that reflects the average radiation dose in the radiographic image data inside the rectangle R.
For this reason, the inner evaluation value can be a value reflecting the radiation amount of the entire inner side of the rectangle R.

Further, according to the present embodiment, the statistical value reflecting the average radiation dose is the average value of the luminance signal corresponding to the radiation dose.
For this reason, since the moving average filter process etc. which are the speed-up techniques of a well-known image filter process can be applied, a high-speed calculation is attained.

Further, according to the present embodiment, the outer evaluation value is a statistical value that reflects the dose in a region where the radiation dose in the radiographic image data is relatively high in the region outside the rectangle R.
For this reason, when there is an irradiation field deviating from the rectangle R, the outer evaluation value can be a value reflecting the dose of radiation corresponding to the irradiation field deviating from the rectangle R. Therefore, the outer evaluation value can be set to a value with higher probability.

Further, according to the present embodiment, the statistical value reflecting the dose in the region where the radiation dose is relatively high is the maximum value of the luminance signal corresponding to the radiation dose.
For this reason, since it is only necessary to obtain the maximum value of the luminance signal corresponding to the radiation dose from the area outside the rectangle R, high-speed calculation is possible.

In addition, according to the present embodiment, the control unit 31 changes the size of the rectangle R when the total sum of the energy at the plurality of points on the original image does not satisfy the predetermined condition, so that a new size rectangle is obtained. R is set, and then energy is calculated at a plurality of points on the original image while moving the area designation frame of a new size with respect to the original image.
For this reason, an appropriate irradiation field inclusion region can be determined for an original image whose irradiation field size is not certain.

Further, according to the present embodiment, the control unit 31 does not satisfy the predetermined condition for the sum of the energy at the plurality of points on the calculated original image, and the area designation frame of a new size is not set. The entire original image is determined as the irradiation field inclusion region.
For this reason, it is possible to prevent the irradiation field inclusion region from being set for the original image having no irradiation field.

In addition, according to the present embodiment, the control unit 31 performs a process of recognizing an irradiation field by further detecting an edge of the irradiation field for the determined irradiation field inclusion region.
For this reason, when the irradiation field inclusion region is larger than the irradiation field, the irradiation field in the irradiation field inclusion region can be further extracted.

In the above embodiment, the area designation frame for designating an area of a predetermined size has been described as a rectangular shape, but an area having an arbitrary shape other than a rectangle can be set. For example, it may be circular or elliptical.
Moreover, in the said embodiment, although 18 types of rectangles used for an irradiation field inclusion area | region setting process were demonstrated, the type of rectangle is not limited to this.

  Further, in the above embodiment, the case where the irradiation field recognition process and the gradation conversion process are performed after the irradiation field inclusion region setting process has been described as an example, but the irradiation field recognition process and the gradation conversion process are not necessarily executed. There is no need, and only one of them may be executed.

  Further, in the above embodiment, in obtaining the outer evaluation value, the luminance signal corresponding to the radiation dose is used as a statistical value reflecting the dose in the region where the radiation dose in the radiation image data outside the rectangle R is relatively high. Although the maximum value is used, when the black and white of the image is inverted, the minimum value of the luminance signal is used.

In the above embodiment, the inner evaluation value and the outer evaluation value are statistical values reflecting the average radiation dose inside and outside the rectangle, but the inner evaluation value and the outer evaluation value are rectangular. It is also possible to use an evaluation value that reflects the dose variation on the inside and outside.
Here, the evaluation value reflecting the dose change amount inside the rectangle is, for example, a value obtained by calculating the strength of the edge based on the difference between adjacent pixels in the rectangle and calculating the total value thereof. The value is the inner evaluation value. The evaluation value reflecting the dose change amount outside the rectangle is a value obtained by calculating the strength of the edge based on the difference between adjacent pixels outside the rectangle and calculating the sum of these values. The evaluation value.

DESCRIPTION OF SYMBOLS 1 In-facility system 2 Modality 3 Radiation image processing apparatus 31 Control part (a setting means, a calculation means, a determination means, an irradiation field recognition means)
32 RAM
33 storage unit 331 image DB
332 area designation frame storage unit R rectangle (area designation frame)
34 Operation unit 35 Display unit 36 Communication unit 37 Media drive 38 Bus 4 Reception device 5 Imager 6 General-purpose printer 7 Client PC

Claims (10)

A radiographic image processing apparatus that performs image processing on radiographic image data obtained by radiographing a region to be diagnosed as a subject,
Setting means for setting a region designation frame for designating a region for a radiation image based on the radiation image data;
While moving the region designation frame set for the radiographic image, at a plurality of points on the radiographic image, the inner evaluation value obtained from the radiation image data inside the region designation frame and the region designation frame A calculation means for calculating energy defined as a difference amount of the outer evaluation value obtained from the outer radiation image data;
When the sum of energy at a plurality of points on the radiographic image calculated by the calculating means satisfies a predetermined condition set in advance, the size of the region designation frame based on the value of energy calculated by the calculating means Determining means for setting the position and determining the region included in the region designation frame as an irradiation field inclusion region;
A radiographic image processing apparatus comprising:   The radiographic image processing apparatus according to claim 1, wherein the inner evaluation value is a statistical value that reflects an average radiation dose in radiographic image data inside the region designation frame. The area designation frame is rectangular,
The radiation image processing apparatus according to claim 2, wherein the statistical value reflecting the average dose of radiation is an average value of a luminance signal corresponding to the radiation dose.   4. The outer evaluation value is a statistical value that reflects a dose in a region where a radiation dose in radiation image data is relatively high in a region outside the region designation frame. The radiographic image processing apparatus as described in any one of Claims. The area designation frame is rectangular,
The radiographic image processing apparatus according to claim 4, wherein the statistical value reflecting a dose in a region where the radiation dose is relatively high is a maximum value or a minimum value of a luminance signal corresponding to the radiation dose. The setting means includes
If the sum of energy at a plurality of points on the radiographic image calculated by the calculation means does not satisfy the predetermined condition, change the size of the region specification frame, set a region specification frame of a new size,
The computing means is
The energy is calculated at a plurality of points on the radiographic image while moving the area designation frame of the new size with respect to the radiographic image. The radiation image processing apparatus described. The determining means includes
When the sum of energy at a plurality of points on the radiographic image calculated by the calculation means does not satisfy the predetermined condition, and the setting of the area designation frame of the new size by the setting means is not made,
The radiographic image processing apparatus according to claim 6, wherein the entire radiographic image is determined as an irradiation field inclusion region.   8. An irradiation field recognition means for recognizing an irradiation field by detecting an edge of the irradiation field with respect to the irradiation field inclusion region determined by the determination means. The radiation image processing apparatus according to item. A radiographic image processing method for radiographic image data obtained by radiographing a region to be diagnosed as a subject,
A setting step for setting a region designation frame for designating a region for a radiation image based on the radiation image data;
While moving the region designation frame set for the radiographic image, at a plurality of points on the radiographic image, the inner evaluation value obtained from the radiation image data inside the region designation frame and the region designation frame A calculation step of calculating energy defined as a difference amount of the outer evaluation value obtained from the outer radiation image data;
When the sum of energy at a plurality of points on the radiographic image calculated by the calculation step satisfies a predetermined condition set in advance, the size of the region designation frame based on the value of energy calculated by the calculation step Determining the position, and determining the region included in the region designation frame as an irradiation field inclusion region,
A radiation image processing method comprising: A computer that performs image processing on radiographic image data obtained by radiographing a diagnostic target part as a subject,
Means for setting a region designation frame for designating a region for a radiation image based on the radiation image data;
While moving the region designation frame set for the radiographic image, at a plurality of points on the radiographic image, the inner evaluation value obtained from the radiation image data inside the region designation frame and the region designation frame Means for calculating energy defined as a difference amount of an outer evaluation value obtained from outer radiation image data;
When the calculated sum of energy at a plurality of points on the radiation image satisfies a predetermined condition set in advance, the size and position of the region designation frame are set based on the calculated energy value, and the region Means for determining an area included in the designated frame as an irradiation field included area;
Program to function as.

Images