JP2015093013A - Radiation image processing device, radiographic apparatus, and control methods, and programs thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent exposure more than necessary when a dosage is excessive, re-photographing due to an increase in noise when a dosage is insufficient, etc., and reduce ineffective exposure.SOLUTION: A radiation image processing device includes: a first correction processing part for performing dark correction and gain correction to a radiation image acquired by a radiation sensor; a calculation part for calculating a dosage index value on the basis of a pixel value of the radiation image corrected by the first correction processing part; a second correction processing part for performing gradation conversion processing for the radiation image corrected by the first correction processing part; and a display control part for causing the radiation image processed by the second correction processing part to be displayed on a display part. When the calculated dosage index value is out of a specific range, the display control part causes the radiation image which is processed by the first correction processing part and which is not processed by the second correction processing part to be displayed on the display part.

Description

  The present invention relates to a radiographic image processing apparatus, a radiographic apparatus, a control method thereof, and a program, and more particularly to a technique for providing a photographer with information for imaging with an appropriate radiation dose.

  In recent years, the use of digital images has progressed in the field of medical image diagnosis. Digital radiography (DR) devices that take X-ray images using sensors that convert radiation (X-rays) into indirect or direct electrical signals are compared to conventional X-ray photography devices that use silver halide photography. Images can be recorded over a very wide X-ray exposure area. Further, it has a practical advantage that the photographed image can be confirmed immediately.

  In the conventional X-ray photography apparatus, since the degree of blackening changes depending on the exposure amount of the film, the imaging conditions such as the tube voltage and the tube current are changed according to the imaging region to adjust the dose. In this case, an overdose or a shortage of dose appears directly in the output image as the degree of blackness, which is the photographic density, and the imaging technician has been required to be careful in adjusting the dose.

  On the other hand, in the DR apparatus, the X-ray dose reaching the sensor is not directly linked to the pixel value of the output image. A process for maintaining the pixel value of the output image within an appropriate range works by an automatic sensitivity correction function, which is one of digital image processing, in response to a change in dose, so that a stable output image can be obtained.

  This automatic sensitivity correction function is not only a merit of the DR apparatus but also a demerit that it is difficult to notice that the photographing engineer is photographing at an inappropriate dose. When the dose is insufficient, noise increases. When the dose is excessive, there is often no problem as a diagnostic image, but the amount of exposure is increased.

  On the other hand, in Patent Document 1, a deviation index value, which is a relative value between a dose index value that is a guide for imaging dose and a standard dose index value for imaging when the order of part information and the like is the same, is calculated. In addition, a display method has been proposed.

  According to this method, the radiographer can evaluate whether the X-ray dose is appropriate in the order based on the dose index value and the deviation index value.

JP 2009-268801 A

  However, in the technique of Patent Document 1, since the dose index value is displayed as a numerical value, there is a problem that it is difficult to intuitively determine whether the dose is appropriate.

  In view of the above problems, the present invention displays inappropriate dose in an easy-to-understand form and makes the radiographer aware of it, so that re-photographing due to excessive exposure due to excessive dose or increased noise due to insufficient dose The purpose is to prevent invalid exposure.

The radiation image processing apparatus according to the present invention for achieving the above object is
First correction processing means for performing dark correction and gain correction on the radiographic image obtained by the radiation sensor;
Calculating means for calculating a dose index value based on the pixel value of the radiation image corrected by the first correction processing means;
Second correction processing means for performing gradation conversion processing on the radiation image corrected by the first correction processing means;
Display control means for displaying the radiation image processed by the second correction processing means on the display unit,
The display control means is a radiographic image processed by the first correction processing means and processed by the second correction processing means when the calculated dose index value is out of a specific range. The radiographic image which is not displayed is displayed on a display part.

  According to the present invention, it is displayed in an easy-to-understand form that an image is being shot with an inappropriate dose, and the radiographer is made aware of it so that it can be re-exposed due to excessive exposure during overdose and noise increase due to insufficient dose. It can prevent shooting and reduce invalid exposure.

The block diagram which shows an example of a structure of a radiography system. The block diagram which shows the function structural example of the radiography apparatus which concerns on embodiment of this invention. The figure which shows an example of the warning information display by the radiography apparatus which concerns on 1st Embodiment. The flowchart which shows the procedure of the process which the radiography apparatus which concerns on 1st Embodiment implements. The figure for demonstrating the production | generation method of the image which does not perform sensitivity correction by the radiography apparatus which concerns on 1st Embodiment. The flowchart which shows the procedure of the process which the radiography apparatus which concerns on 2nd Embodiment implements. The figure which shows the relationship of the input-output pixel value of the look-up table used for the conversion process from the input pixel value of the gradation process by the radiography apparatus which concerns on 3rd Embodiment to an output pixel value.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
An example of the configuration of the radiation imaging system will be described with reference to FIG. The radiation generator 20 has a function of generating radiation. The radiation imaging apparatus 10 includes an imaging unit 101 and an imaging display control unit 102, converts radiation transmitted through the subject 30 into image data, and outputs the image data to the display unit 40. The display unit 40 is a liquid crystal display or the like, and displays an image output from the radiation imaging apparatus. The dosimeter 50 measures the radiation dose.

  An imaging unit 101 in the radiation imaging apparatus detects a transmitted radiation signal, converts it to an electrical signal, and outputs image data. The photographing display control unit 102 includes a CPU 1021, a memory 1022, a DISK 1023, a display control unit 1024, an input unit 1025, and a BUS 1026. The photographing display control unit 102 controls the photographing unit, generates display contents, and controls the display unit.

  A CPU 1021 in the photographing display control unit is a microprocessor, and performs arithmetic and logical determinations for photographing control processing, image processing, display information generation processing, and the like, and controls each device connected to the bus.

  The memory 1022 is a readable / writable random access memory, and is used as a main memory for temporarily storing various data from each device. The memory 1022 stores various work areas for storing data necessary for processing, a stack necessary for processing, and various data whose values are changed during processing.

  The DISK 1023 is a mass storage device and stores a large amount of data in a changeable manner. The DISK 1023 is composed of, for example, a hard disk. The control program executed by the CPU 1021 and various initial data may be stored in the DISK 1023. In this case, the control program and various initial data are loaded into the main memory shown in the memory 1022 as necessary and executed or referred to.

  The display control unit 1024 controls image display contents on the display unit. The input unit 1025 is a keyboard, a button, a touch panel, or the like, and an operator gives various input instructions. A BUS 1026 is a bus, and transfers an address signal and a control signal instructing each device to be controlled by the CPU 1021. Data transfer between devices is also performed.

  The imaging display control unit 102 is assumed to have a configuration in which control software is installed in a personal computer or the like, but a dedicated hardware unit may be used. In addition, the imaging unit 101 and the imaging display control unit 102 in the radiation imaging apparatus are configured separately. However, the imaging unit 101 is not limited to a separate unit, and a part of the functions of the imaging display control unit 102 is included in the imaging unit 101. Can also be built in.

  With reference to FIG. 2, a functional configuration example of the radiation imaging apparatus according to the embodiment of the present invention will be described. The radiation imaging apparatus 10 includes an imaging unit 111, a dose index value acquisition unit 112, a dose index value determination unit 113, a warning information generation unit 114, an image processing unit 115, and a display control unit 116. The operation of each processing unit is executed and controlled by the CPU 1021 in FIG.

  The imaging unit 111 detects a radiation signal transmitted through the object, converts it into an electrical signal, and outputs image data. The dose index value acquisition unit 112 acquires a dose index value from the image data. As an example of the dose index value, there is an EI value that is an index of a value proportional to the irradiation dose on the surface of the imaging unit defined in IEC 62494-1. A method for obtaining the dose index value will be described later. Further, the dose index value may be calculated based on the pixel value of the radiographic image corrected by an image processing unit 115 described later functioning as the first correction processing unit.

  The dose index value determination unit 113 determines whether or not the dose index value acquired by the dose index value acquisition unit 112 is within an allowable range. It is determined whether or not the dose index value acquired by the dose index value acquisition unit 112 in the current imaging is a value within a predetermined allowable range set in advance.

  The warning information generation unit 114 generates warning information when the dose index value determination unit 113 determines that the dose index value is outside the allowable range. The image processing unit 115 performs digital image processing on the image data input from the imaging unit 111 and converts the image data into an image suitable for diagnosis. The display control unit 116 generates a screen to be presented to the user from the image processed by the image processing unit 115 and the warning information generated by the warning information generation unit 114, and displays the screen to be displayed on the display unit 40 in FIG. Control the state.

  Here, warning information generated by the warning information generation unit 114 will be described. This is information for warning the user when the dose index value determination unit 113 determines that the dose index value of the image taken this time is outside the range of the appropriate dose. A radiography apparatus such as a digital radiography (DR) apparatus normally has an automatic sensitivity correction function which is one of the image processing functions of the image processing unit 115 in order to output a stable image even if the dose changes to some extent. Thus, the process of keeping the pixel value of the output image within an appropriate range is performed. Normally, the display control unit 116 controls to display an image processed by enabling the automatic sensitivity correction function. Since this automatic sensitivity correction function works, it is difficult for the user to determine whether or not the dose is appropriate only by looking at the image.

  On the other hand, when the dose index value determination unit 113 determines that the dose index value of the image captured this time is outside the range of the appropriate dose, the image processing unit 115 does not perform the enhancement process. An image is generated, and the warning information generation unit 114 uses the first image as part of the warning information. Here, the enhancement processing (gradation processing, dynamic range compression processing, sharpening processing, MTF improvement processing) is processing for obtaining an image for diagnosing each imaging region, and changes processing depending on the imaging region. is there. Dark correction, gain correction, and defect correction are processes for correcting the characteristics of the radiation sensor, and are processes that do not depend on an imaging region or irradiation conditions.

  The image processing unit 115 performs darkness conversion and gain correction on the radiation image obtained by the radiation sensor, and performs gradation conversion processing on the radiation image corrected by the first correction processing unit. It has a function as a second correction processing unit to be performed.

  The display control unit 116 causes the display unit to display the radiation image processed by the image processing unit 115 functioning as a second correction processing unit. When the calculated dose index value is out of the specific range, the display control unit 116 is a radiographic image processed by the image processing unit 115 functioning as the first correction processing unit and the second correction processing. The display unit displays a radiographic image that has not been processed by the image processing unit 115 functioning as a unit.

  Although the radiation imaging apparatus 10 has been described above, the radiation imaging apparatus 10 may be configured as a radiation image processing apparatus by removing the imaging unit.

  FIG. 3 shows an example of warning information display generated by the warning information generation unit 114. In addition to the character information that informs the user that the dose index value is outside the allowable range, a first image that does not perform the enhancement process is displayed. Specifically, as shown in FIG. 2, text information 301 such as “Warning” and “Dose index value exceeds allowable range”, and the dose index acquired by the dose index value acquisition unit 112 in the current imaging. Value 302, information 303 indicating the preset upper and lower dose limits, an image 304 when the enhancement process is not performed, and an image like the image 304 when the automatic enhancement process is not performed Is displayed. Note that it is not necessary to display all of these pieces of information, and any information including at least the image 304 may be displayed.

  Next, a method of using image data obtained from the imaging unit 111 will be described as an example of a method of acquiring a dose index value acquired by the dose index value acquisition unit 112 of FIG. In the acquired image data, a region of interest that is an important part for image diagnosis by a doctor is specified. Regardless of the type of image, this region of interest can be selected by selecting the central part of the image, changing the region of interest according to the part of the image, or analyzing the irradiation region and subject region from the image data. There is a method to specify. For example, as a method of changing the region of interest depending on the part of the image, in the case of a front chest image, the positions of the right lung and left lung are set as the region of interest.

  Next, the transmitted dose is calculated from the pixel value of the image data of the region of interest. In this case, the transmitted dose is not necessarily an absolute value and may be an index value correlated with the transmitted dose. For example, the transmission dose is calculated based on the average value of the image data of the region of interest, and this is used as the dose index value. The method for acquiring the dose index value from the image data has been described above. However, the dose index value may be acquired from the dosimeter 50 shown in FIG.

  Next, with reference to the flowchart of FIG. 4, the procedure of the process which the radiography apparatus which concerns on 1st Embodiment implements is demonstrated. In step S <b> 401, the dose index value determination unit 113 acquires the dose index value of the currently captured image from the dose index value acquisition unit 112.

  In step S402, the dose index value determination unit 113 compares the upper limit value of the allowable range of the dose index value set in advance with the dose index value in the current imaging, and the current dose index value is larger. It is determined whether or not. If it is determined that the current dose index value is greater than the upper limit value, the process proceeds to step S404. On the other hand, if it is determined that the current dose index value is less than or equal to the upper limit value, the process proceeds to step S403.

  In step S403, the dose index value determination unit 113 compares the lower limit value of the allowable range of the dose index value set in advance with the dose index value of the current imaging, and determines whether the current dose index value is smaller. Determine whether or not. If it is determined that the current dose index value is smaller than the lower limit value, the process proceeds to step S404. On the other hand, if it is determined that the current dose index value is greater than or equal to the lower limit value, the process ends.

  The process proceeds to step S404 after the determination processing in step S402 and step S403 is when it is determined that the dose index value of the current imaging is out of the allowable range, and warning information is displayed in the following steps.

  In step S404, the image processing unit 115 acquires information indicating that the dose index value is out of the allowable range from the dose index value determination unit 113, and generates a first image that is not subjected to the enhancement process. Details of an image generation method without performing sensitivity correction will be described later with reference to FIG.

  In step S405, the warning information generation unit 114 uses the first image that is not subjected to the enhancement processing generated in step S404 as part of the warning information, and displays it through the display control unit 116. An example is the image 304 in FIG. Furthermore, at least any of the character information 301, the dose index value 302, the information 303 indicating the upper and lower dose limits set in advance, and the character information 305 described in FIG. 3 may be displayed. Thus, the processes in the flowchart of FIG. 4 are completed.

  Here, with reference to FIG. 5, details of an image generation method that does not perform enhancement processing will be described. In general, the image processing unit 115 first performs preprocessing such as offset correction processing and gain correction processing in order to correct various characteristics of the DR sensor. Next, the image is analyzed, and analysis information such as a subject area is acquired. Thereafter, using the analysis information, QA processing such as frequency enhancement processing, dynamic range compression processing, and gradation conversion processing is performed on the preprocessed image data.

  FIG. 5A is an example of a distribution of pixel values of a portion determined to be an effective subject by the analysis processing. In normal DR image processing, when many effective pixel values are distributed within a certain range of input pixel values as shown in FIG. 5A, many output pixels are included in the input pixel value range. Process to assign a value.

  FIG. 5B is a diagram showing the relationship between input and output pixel values of a lookup table used for conversion processing for assigning output pixel values to input pixel values when gradation processing is performed as sensitivity correction. . When there is a distribution of input pixel values as shown in FIG. 5A, in order to assign many output pixel values to the distributed pixel values, the slope of that portion is set as shown by the broken line 502. Enlarge.

  On the other hand, as one example of processing when the enhancement processing is not performed, linear conversion processing that does not consider the input pixel value distribution is performed as indicated by the solid line 501.

  As another example of the processing that does not perform the enhancement processing, there is conversion processing that approximates film characteristics in a radiographic apparatus. Reference numeral 503 in FIG. 5C denotes a look-up table simulating the change in blackness depending on the exposure amount of the film, and an image close to the film is generated using this table for gradation processing.

  When there is a possibility that the dose index value may be inappropriate by the series of processes of FIGS. 4 and 5, the first image without sensitivity correction is displayed as warning information. The image without sensitivity correction becomes an image close to the image taken with a conventional radiographic apparatus, and the excess or deficiency of the dose appears directly in the image. Encouraging effect is increased.

  As described above, according to the radiation imaging apparatus according to the present embodiment, it is possible to display that the imaging is performed with an inappropriate dose as warning information in a form that is easy to understand, and to make the imaging engineer aware. Therefore, it is possible to prevent unnecessary exposure at the time of excessive dose and re-imaging due to noise increase at the time of insufficient dose, thereby reducing invalid exposure.

  In this embodiment, the radiation imaging apparatus has been described. However, when a dose index value is acquired from radiographic image data and the dose index value is out of the allowable range, the first image without sensitivity correction is displayed as warning information. The present embodiment may be applied to an information processing apparatus that displays as

(Second Embodiment)
In the second embodiment, an example will be described in which an image that is not subjected to enhancement processing is displayed for a certain period when the dose index value is determined to be outside the allowable range. Hereinafter, the difference from the first embodiment will be mainly described. The configuration of the radiation imaging apparatus according to this embodiment is the same as the configuration described with reference to FIGS.

  With reference to the flowchart of FIG. 6, the procedure of the process which the radiography apparatus which concerns on 2nd Embodiment implements is demonstrated.

  Since each process of step S601-step S604 is the same as each process of step S401-step S404 of FIG. 4, detailed description is abbreviate | omitted.

  If it is determined in step S602 and step S603 that the dose index value of the current imaging is outside the allowable range, the process proceeds to step 604. On the other hand, if it is determined that the dose index value is within the allowable range, the process proceeds to step S606.

  A series of steps S606 and S607 are normal DR image processing and image display steps when the dose is appropriate.

  In step S606, the image processing unit 115 performs image processing including enhancement processing, and generates a display image (second image). In step S607, the display control unit 116 displays the image and ends the process.

  On the other hand, a series of steps S604, S605, and S607 is a step of image processing and image display when there is a possibility that the dose is inappropriate. In step S604, the image processing unit 115 acquires information indicating that the dose index value is out of the allowable range from the dose index value determination unit 113, and generates a first image that is not subjected to enhancement processing. In addition, an image (second image) subjected to enhancement processing is also generated.

  In step S605, the display control unit 116 displays the first image generated in step 604 that is not subjected to the enhancement process for a certain period. Thereafter, in step S607, the display control unit 116 displays the image that has been subjected to the enhancement processing.

  As described above, when there is a possibility that the dose index value is inappropriate, an image without sensitivity correction is displayed for a certain period. The image without sensitivity correction becomes an image close to the image taken with a conventional radiographic apparatus, and the excess or deficiency of the dose appears directly in the image. Encouraging effect is increased.

  According to the radiation imaging apparatus according to the present embodiment described above, it can be displayed in a form that makes it easy to understand that imaging is being performed with an inappropriate dose, and the imaging technician can be made aware. Therefore, it is possible to prevent unnecessary exposure at the time of excessive dose and re-imaging due to noise increase at the time of insufficient dose, thereby reducing invalid exposure.

(Third embodiment)
In the third embodiment, an example will be described in which when the dose index value cannot be acquired, the inclination of the lookup table of the input / output pixel conversion process of the gradation process of the image that is not subjected to the enhancement process is reduced. Hereinafter, the difference from the first embodiment will be mainly described. The configuration of the radiation imaging apparatus according to this embodiment is the same as the configuration described with reference to FIGS.

  FIG. 7 is a diagram illustrating a relationship between input and output pixel values of a lookup table used for conversion processing from input pixel values to output pixel values when gradation processing is performed. It is assumed that the inclination is normally as indicated by a solid line 701. If the dose index value cannot be acquired, the slope is reduced as indicated by the broken line 702. Even when the dose analysis value cannot be obtained, such as when the subject analysis fails, it is possible to collect a wide range of input pixel values near the median with high visibility, which can cause excessive or insufficient doses. An image that can be easily determined can be provided. That is, when the dose index value is not acquired, in the input / output pixel conversion process for the image data, conversion is performed so that the input pixel value falls within a certain output pixel value range.

  As described above, according to the radiation imaging apparatus according to the present embodiment, it is possible to display that the imaging is performed with an inappropriate dose in a form that is easy to visually recognize, and to make the imaging engineer aware. Therefore, it is possible to prevent unnecessary exposure at the time of overdose and re-imaging due to noise increase at the time of shortage of dose, and to reduce invalid exposure.

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (10)

First correction processing means for performing dark correction and gain correction on the radiographic image obtained by the radiation sensor;
Calculating means for calculating a dose index value based on the pixel value of the radiation image corrected by the first correction processing means;
Second correction processing means for performing gradation conversion processing on the radiation image corrected by the first correction processing means;
Display control means for displaying the radiation image processed by the second correction processing means on the display unit,
The display control means is a radiographic image processed by the first correction processing means and processed by the second correction processing means when the calculated dose index value is out of a specific range. A radiographic image processing apparatus that displays a radiographic image not displayed on a display unit. Photographing means for detecting radiation transmitted through the subject and acquiring image data;
Image processing means for performing image processing on the image data;
An acquisition means for acquiring a dose index value;
Determining means for determining whether or not the dose index value is within an allowable range;
Display means for generating a first image without performing enhancement processing on the image data when the dose index value is determined to be outside an allowable range, and displaying the first image as warning information. Radiography equipment.   The display means further displays, as the warning information, the dose index value, character information indicating that the dose index value is out of an allowable range, and information indicating an upper limit value and a lower limit value of a preset dose. The radiation imaging apparatus according to claim 2.   The radiation imaging apparatus according to claim 2, wherein the display unit displays the first image as the warning information for a certain period.   3. The image processing unit according to claim 2, wherein when the dose index value is determined to be within an allowable range, the image processing unit performs enhancement processing on the image data to generate a second image. 5. The radiographic apparatus according to any one of 4 above.   When the dose index value is not acquired by the acquisition unit, the image processing unit performs conversion so that the input pixel value falls within a fixed output pixel value range in the input / output pixel conversion process for the image data. The radiation imaging apparatus according to any one of claims 2 to 4, wherein the radiation imaging apparatus is characterized in that: A method for controlling a radiation image processing apparatus, comprising:
A first correction processing step in which a first correction processing unit performs dark correction and gain correction on the radiation image obtained by the radiation sensor;
A calculating step for calculating a dose index value based on the pixel value of the radiation image corrected by the first correction processing step;
A second correction processing step, wherein the second correction processing means performs a gradation conversion process on the radiation image corrected by the first correction processing step;
A display control means for displaying the radiation image processed in the second correction processing step on the display unit,
In the display control step, when the calculated dose index value is out of a specific range, the radiation image processed by the first correction processing step and processed by the second correction processing step. A method for controlling a radiographic image processing apparatus, comprising: displaying a radiographic image not displayed on a display unit. A method for controlling a radiation imaging apparatus, comprising:
An imaging means that detects radiation transmitted through the subject and acquires image data;
An image processing means for performing image processing on the image data;
An acquisition means for acquiring a dose index value;
A step of determining whether or not the dose index value is within an allowable range;
A display unit that generates a first image without performing enhancement processing on the image data when the dose index value is determined to be out of an allowable range, and displays the first image as warning information. A control method for a radiation imaging apparatus.   The program for making a computer perform each process of the control method of the radiographic image processing apparatus of Claim 7.   The program for making a computer perform each process of the control method of the radiography apparatus of Claim 8.

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