JP5049257B2 - Image processing apparatus and method, and program - Google Patents

Description

  The present invention relates to a radiation image processing apparatus, method, and program for removing an afterimage from a radiation image detected by a radiation image detector.

2. Description of the Related Art Conventionally, a subject is diagnosed using a radiation image by detecting the amount of radiation that has been exposed to the subject and transmitted through the subject as a radiation image. A radiation image detector is used as an apparatus for acquiring this radiation image. In the radiation image detector described above, an afterimage component may remain, and the image quality may deteriorate due to the afterimage component. Therefore, various afterimage noise removal processes have been proposed (see, for example, Patent Document 1). In Patent Document 1, afterimage data is generated by applying shading correction, thinning processing, average reduction processing, and median filter processing to afterimage data, and afterimage correction is performed by removing this afterimage component from the radiation image. It has been proposed.
JP 2005-283798 A

  When afterimage correction data is created by performing median filter processing on an afterimage component as in Patent Document 1, noise in a non-edge region can be suppressed while the edge region of the afterimage correction data is preserved as it is. However, the median filter processing with a short filter length cannot sufficiently suppress the noise of the afterimage, and there is a problem that the noise of the original image increases when the afterimage correction is performed. On the other hand, when the filter length is long, there is a problem that it takes a long processing time, and a thin afterimage component is removed and cannot be corrected.

  Therefore, an object of the present invention is to provide a radiographic image processing apparatus, method, and program capable of suppressing noise degradation while removing afterimages by afterimage removal processing.

  The radiographic image processing apparatus of the present invention includes an afterimage detection unit that detects an afterimage included in a radiographic image detected by irradiating a subject, and an afterimage that has been subjected to smoothing processing on the afterimage detected by the afterimage detection unit Smoothing means for generating a smoothed image, edge extraction means for extracting an edge area of an afterimage detected by the afterimage detection means as an afterimage edge area, and from an afterimage edge area extracted by the edge extraction means to a non-edge area Correction data generating means for generating afterimage correction data by weighting and adding the afterimage smoothed image smoothed by the smoothing means and the afterimage so that the weighting to the afterimage smoothed image increases, and the correction data And an afterimage removing means for removing the afterimage correction data generated by the generating means from the radiation image. Is shall.

  The radiographic image processing method of the present invention detects an afterimage included in a radiographic image detected when a subject is irradiated with radiation, and generates an afterimage smoothed image obtained by performing a smoothing process on the detected afterimage. In addition, the afterimage edge area indicating the edge area of the afterimage is extracted, and the afterimage smoothed image and the afterimage are weighted so that the weighting of the afterimage smoothed image increases from the extracted afterimage edge area toward the non-edge area. The afterimage correction data is generated by addition, and the generated afterimage correction data is removed from the radiation image.

  The radiological image processing program of the present invention detects an afterimage included in a radiographic image detected when a subject is irradiated with radiation, and performs a smoothing process on the detected afterimage. Afterimage smoothed images and afterimages are extracted so that the afterimage edge region indicating the edge region of the afterimage image is extracted and the weighting of the afterimage smoothed image increases from the extracted afterimage edge region toward the non-edge region. Afterimage correction data is generated by weighting and adding, and the generated afterimage correction data is removed from the radiation image.

  Here, the radiographic image only needs to be detected when the subject is irradiated with radiation. For example, the radiographic image may be detected using a phosphor storage sheet, or a two-dimensional radiation detector (FPD). ) May be used.

  The correction data generation means may be any means that generates afterimage correction data by changing the ratio between the afterimage smoothed image and the afterimage, and adding the afterimage edge area from the end of the afterimage edge area. It is desirable that the transition area to be set is set and the weighting coefficient is set to be smaller from the end of the afterimage edge area to the outside in the set transition area.

  Further, the afterimage detecting means is not limited to any method as long as it detects an afterimage component included in the radiation image, for example, an afterimage from a signal component read from the radiation image detector immediately before photographing the subject by the radiation image detector. Images can be acquired.

  According to the radiological image processing apparatus, method, and program of the present invention, an afterimage that is included in a radiographic image that is detected when a subject is irradiated with radiation is detected, and a smoothing process is performed on the detected afterimage. The afterimage smoothed image is generated so that the afterimage edge region indicating the edge region of the afterimage image is generated and the weighting of the afterimage smoothed image increases from the extracted afterimage edge region toward the non-edge region. Afterimage correction data is generated by weighting and adding the afterimage and the generated afterimage correction data is removed from the radiation image, so that the effect of the afterimage correction is gradually changed from the edge region toward the non-edge region. Therefore, afterimage removal processing is performed when only smoothed afterimage correction data is used. While performing reliably afterimage removed prevent the remaining edges, abrupt change in image quality in the edge region and the non-edge region can be suppressed.

  The correction data generation unit sets a transition area having a predetermined pixel width from the end of the afterimage edge area, and weights the afterimage smoothed image from the end of the afterimage edge area to the outside in the set transition area. When using only the smoothed afterimage correction data, the boundary between the edge region and the non-edge region is prevented while preventing the afterimage edge from remaining and reliably removing afterimages. In this case, it is possible to prevent the image quality from being deteriorated due to the abrupt change in image processing.

  Further, if the afterimage detection means detects from a signal read from the radiation image detector immediately before photographing the subject by the radiation image detector, the afterimage component included in the radiation image can be detected with high accuracy. .

  Embodiments of the radiation image apparatus of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic view showing a preferred embodiment of a radiation image processing apparatus 1 of the present invention. The configuration of the radiographic image processing apparatus 1 as shown in FIG. 1 is realized by executing a radiographic image processing program read into the auxiliary storage device on a computer (for example, a personal computer). The radiation image processing program is stored in an information storage medium such as a CD-ROM, or distributed via a network such as the Internet and installed in a computer.

  The radiation image processing apparatus 1 includes an image acquisition unit 10, an afterimage detection unit 20, a smoothing unit 30, an edge extraction unit 40, a correction data generation unit 50, and an afterimage removal unit 60. The image acquisition unit 10 acquires, as digital data, a radiation image P detected using a stimulable phosphor sheet, a solid state detector (FPD), or the like by, for example, chest imaging or a mammography apparatus.

  The afterimage detection means 20 detects an afterimage image AP included in the radiation image P detected when the subject is irradiated with radiation. For example, the dark image when the dark image is read immediately before photographing is acquired as the afterimage AP. That is, the afterimage detection means 20 is included as a function of the image acquisition means 10.

  The smoothing means 30 performs a smoothing process on the afterimage image AP detected by the afterimage detection means 20. Here, the smoothing means 30 smoothes the afterimage image AP by filter processing using, for example, a median filter or the like.

  The edge extraction means 40 extracts the edge area of the afterimage image AP detected by the afterimage detection means 20 as the afterimage edge area EP. For example, the edge extraction unit 40 generates a difference image by calculating a difference value between adjacent pixels for each pixel of the afterimage image AP, and a pixel whose difference magnitude is less than a threshold is not an edge candidate pixel in the difference image. The value is set to 0, and then the number of connected pixels other than 0 is checked. The edge extraction method is not limited to the edge extraction method described above, and a known edge detection processing method may be used.

The correction data generation means 50 changes the ratio between the afterimage smoothed image SP smoothed by the smoothing means 30 and the afterimage image AP from the afterimage edge component EP generated by the edge extraction means 40 toward the non-edge region. Are added to generate afterimage correction data CP. Specifically, the correction data generation means 50 weights and averages the afterimage image AP and the afterimage smoothed image SP, and the afterimage correction is performed by the following equation (1) as a weighting coefficient α (0 ≦ α ≦ 1). Data CP is calculated.
CP = α × AP + (1−α) × SP (1)
In the above formula (1), as the weighting coefficient α increases, the ratio of the afterimage image AP increases and the edge remains. On the other hand, the smaller the weighting coefficient α, the larger the ratio of the afterimage smoothed image SP and the weaker the edge.

  Here, the weighting coefficient α is set so as to decrease from the edge region to the non-edge region in the afterimage edge region EP. Specifically, as shown in FIG. 2, the correction data generating means 50 sets the transition region TR for the set number of pixels around the edge region of the afterimage edge region EP. Then, the weighting coefficient α is set so as to decrease from the edge region toward the non-edge region in the transition region TR. For example, as shown in FIG. 3, α = 1 is set for the afterimage edge area EP, and α = 0.9 is set for the pixels adjacent to the afterimage edge area EP, so that the distance from the afterimage edge area EP increases. Set so that α becomes smaller. That is, the afterimage image AP becomes the afterimage correction data CP for the pixel with α = 1, and the afterimage is calculated for the pixel with α = 0.7 by calculating (0.7 × afterimage image AP + 0.3 × afterimage smoothed image SP). Let it be correction data CP. Further, α = 0 in a region outside the transition region TR, and the afterimage smoothed image SP is used as the afterimage correction data CP.

  The afterimage removing unit 60 performs correction for removing the afterimage correction data CP generated by the correction data generating unit 50 from the radiation image P. At this time, the afterimage removing means 60 performs afterimage correction by multiplying the afterimage correction data CP by a predetermined afterimage correction coefficient and subtracting it from the radiation image P.

As described above, when the afterimage correction data CP is generated, the afterimage correction data CP is generated by providing the transition region TR in which the ratio of the afterimage component smoothed from the edge region to the non-edge region increases. When only the afterimage correction data is used, it is possible to prevent a problem that the edge of the afterimage remains, and to suppress a sudden change in image quality between the edge region and the non-edge region.
That is, since the afterimage image AP includes a noise component as in the case of the radiation image P, if the afterimage correction is performed using the afterimage image AP itself, the noise of the radiation image P is deteriorated. Therefore, it is necessary to perform noise removal processing on the afterimage image AP, and the afterimage image AP is smoothed. However, the edge component in the afterimage smoothed image SP that has been subjected to the smoothing process is in a blurred state. When the afterimage correction is performed using the afterimage smoothed image SP itself, the afterimage edge component is converted into the radiation image P. It remains in the interior, and sufficient afterimage removal processing cannot be performed. Therefore, when the afterimage correction data CP is generated as described above, the afterimage edge region EP is extracted so that the afterimage edge region EP remains in the afterimage correction data CP (α = 1.0).

  On the other hand, in the afterimage correction data CP, when the image data of the afterimage smooth image SP described above is used for the non-afterimage edge region using the image data of the afterimage image AP for the afterimage edge region EP, Image processing changes abruptly at the boundary with the edge region. Therefore, when the afterimage removal process is performed using the afterimage correction data CP, as a result, the image quality of the radiation image P also changes abruptly between the edge region and the non-edge region. Therefore, as described above, the afterimage correction data CP is created by providing the transition region TR in which the ratio of the afterimage component smoothed from the edge region to the non-edge region is increased around the afterimage edge region EP, thereby creating the afterimage correction data CP. When only the afterimage correction data thus used is used, it is possible to prevent a problem that the edge of the afterimage remains, and to suppress a sudden change in image quality between the edge region and the non-edge region.

  FIG. 4 is a flowchart showing a preferred embodiment of the radiographic image processing method of the present invention. The radiographic image processing method will be described with reference to FIGS. First, an afterimage image AP is detected in advance before the radiation image P, and then the radiation image P is acquired (step ST1). Next, an afterimage smoothing component SP obtained by smoothing the afterimage image AP is generated by the smoothing means 30 (step ST2), and an afterimage edge region EP is extracted from the afterimage image AP (step ST3). Thereafter, the afterimage smoothing component SP and the afterimage image AP are weighted and added by the correction data generating means 50 based on the afterimage edge region EP to create afterimage correction data CP (see step ST4, FIG. 2 and FIG. 3). Then, the afterimage removal means 60 subtracts the afterimage correction data CP from the radiation image P, thereby generating a corrected radiation image P10 (step ST5).

  According to the above-described embodiment, the afterimage smoothed image SP obtained by detecting the afterimage AP included in the radiation image P detected when the subject is irradiated with radiation and smoothing the detected afterimage AP. Is generated, and an afterimage edge area EP indicating an edge area of the afterimage image AP is extracted, and a weight (1-α) is applied to the afterimage smoothed image SP from the edge area toward the non-edge area based on the extracted afterimage edge area EP. ) To increase the afterimage smoothed image SP and the afterimage image AP by weighting and adding the afterimage correction data CP, and removing the generated afterimage correction data CP from the radiation image P, the edge region EP Afterimage removal processing that gradually changes the effect of afterimage correction from the non-edge region to the non-edge region is performed. In an edge portion and a non-edge portion can be prevented the degradation of the image quality of rapidly quality changes.

  Further, the correction data generation means 50 sets a transition region TR having a predetermined pixel width from the end of the afterimage edge region EP, and the weighting coefficient α from the end of the afterimage edge region EP toward the outside in the set transition region TR. Is set to a small value, a transition region TR in which the edge region gradually weakens from the edge of the edge region toward the non-edge region is provided, so that only afterimage correction data that has been smoothed is used. In addition to preventing the problem of remaining edges, it is possible to prevent image quality deterioration due to abrupt image processing change at the boundary between the edge region and the non-edge region.

  Further, if the afterimage detection means 20 detects from the signal read from the radiation image detector immediately before the subject is imaged by the radiation image detector, the afterimage component included in the radiation image P can be detected with high accuracy. Can do. In the above-described embodiment, the edge is detected from the afterimage correction data. However, the afterimage may be corrected by detecting the edge from the previous photographed image that causes the afterimage. By doing so, it is possible to detect the edge with higher accuracy than detecting the edge from the afterimage correction data having a low density.

  The embodiment of the present invention is not limited to the above embodiment. For example, the edge extraction means 40 is not limited to the method described above when extracting an edge region while removing noise. For example, as in JP-A-5-328106, edge detection may be performed by pattern matching. Good.

The block diagram which shows preferable embodiment of the radiographic image processing apparatus of this invention FIG. 2 is a schematic diagram showing an example of a transition region set around an afterimage edge region in the correction data generation unit of FIG. Schematic diagram showing an example of the weighting coefficients of the edge region and the transition region set in the correction data generation means of FIG. The flowchart which shows preferable embodiment of the radiographic image processing method of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiation image processing apparatus 10 Image acquisition means 20 Afterimage detection means 30 Smoothing means 40 Edge extraction means 50 Correction data generation means 60 Afterimage removal means AP Afterimage image CP Afterimage correction data EP Afterimage edge area P Radiation image SP Afterimage smoothed image TR Transition area

Claims (5)

An afterimage detecting means for detecting an afterimage included in a radiation image detected by irradiating a subject with radiation;
Smoothing means for applying a smoothing process to the afterimage detected by the afterimage detection means to generate an afterimage smoothed image;
Edge extraction means for extracting an edge area of the afterimage detected by the afterimage detection means as an afterimage edge area;
Afterimage correction is performed by weighting and adding the afterimage smoothed image and the afterimage so that the afterimage smoothed image is extracted from the afterimage edge region extracted by the edge extraction unit toward the non-edge region. Correction data generating means for generating data;
A radiographic image processing apparatus comprising: an afterimage removal unit that removes the afterimage correction data generated by the correction data generation unit from the radiographic image.   The correction data generation means sets a transition region having a predetermined pixel width from an end of the afterimage edge region, and the afterimage smoothed image is set outward from the end of the afterimage edge region in the set transition region. The radiation image processing apparatus according to claim 1, wherein the weighting is set to be large.   The said afterimage detection means acquires the dark image read from this radiographic image detector just before image | photographing the said object with a radiographic image detector as said afterimage. Radiation image processing device. Detect afterimages included in the radiation image detected when the subject is irradiated with radiation,
Generating an afterimage smoothed image obtained by performing a smoothing process on the detected afterimage, and extracting an afterimage edge region indicating an edge region of the afterimage,
Afterimage-corrected data is generated by weighted addition of the afterimage-smoothed image and the afterimage, so that the weighting of the afterimage-smoothed image increases from the extracted afterimage edge region toward the non-edge region,
The radiographic image processing method, wherein the generated afterimage correction data is removed from the radiographic image. On the computer,
Detect afterimages included in the radiation image detected when the subject is irradiated with radiation,
Generating an afterimage smoothed image obtained by performing a smoothing process on the detected afterimage, and extracting an afterimage edge region indicating an edge region of the afterimage,
Afterimage-corrected data is generated by weighted addition of the afterimage-smoothed image and the afterimage, so that the weighting of the afterimage-smoothed image increases from the extracted afterimage edge region toward the non-edge region,
A radiation image processing program, wherein the generated afterimage correction data is removed from the radiation image.

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