JPH0677569B2 - Image rollover determination method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a method for determining whether the orientation of an image formed by an image signal carrying a radiation transmission image of a human body is normal or is overturned by 90 °. Regarding

(Prior Art) When a certain kind of phosphor is irradiated with radiation (X-ray, α-ray, β-ray, γ-ray, electron beam, ultraviolet ray, etc.), a part of this radiation energy is accumulated in the phosphor, It is known that when a phosphor is irradiated with excitation light such as visible light, the phosphor exhibits stimulated emission depending on the stored energy, and a phosphor having such a property is called a stimulable phosphor. .

Using this stimulable phosphor, the radiation image information of the human body is once recorded on a sheet-shaped stimulable phosphor, and then this stimulable phosphor sheet is scanned with excitation light such as laser light to stimulate emission. An image signal is obtained by photoelectrically reading this stimulated emission light by generating light, and the image signal is subjected to image processing. Based on the image signal subjected to this image processing, a radiation image of the subject is taken as a photographic light-sensitive material, etc. The present applicant has already proposed a radiographic image information recording / reproducing system for outputting a visible image on a recording material of CRT or a display device such as a CRT (Japanese Patent Laid-Open No. 55-12).
No. 429, No. 56-11395, etc.).

In the above system, for example, when recording (photographing) the radiation image information of the chest of the human body on the stimulable phosphor sheet, the radiographing is usually performed so that the vertical direction of the sheet is the vertical direction of the human body, and then the sheet is taken. Even after the image signal is read from the image, the image formed by the image signal is handled in the vertical direction of the sheet as the vertical direction of the image.

However, in some cases, the image is taken with the sheet oriented horizontally, that is, with the vertical direction of the sheet being the left-right direction of the human body. In that case, the image signal is read after the image signal is read. In the image displayed, the vertical direction of the image is the left-right direction of the human body.

(Problems to be Solved by the Invention) However, in the above system, image processing is performed on an image signal and a visible image is output to image reproducing means such as a CRT. At this time, various algorithms related to image processing are usually set assuming that the vertical direction of the image is the vertical direction of the human body, or the vertical direction of the visible image is the vertical direction of the human body. Since the output process is set to output the image, if the vertical direction of the image is the left-right direction of the human body, the fact is input to the image processing means or the image reproducing means to change the image processing algorithm. Alternatively, it is necessary to change the output process so that the vertical direction in the visible image is the vertical direction of the human body, which requires the image to be in the normal position in the system (usually It is necessary to determine whether the state in which the human body is vertically aligned is the normal position) or the roll position is 90 ° rotated from the normal position.

In view of the above circumstances, an object of the present invention is to provide an image rollover judging method capable of judging whether the image is in a normal position or a rollover position.

(Means for Solving Problems) In order to achieve the above-mentioned object, an image rollover judging method according to the present invention has a feature that, in order to achieve the above-mentioned object, the image signal level in the vertical direction and the horizontal direction of the image signal from the image signal that carries a transparent image of the human body. It is characterized in that a distribution is obtained, a feature amount representing each distribution is calculated from each distribution, and both feature amounts are compared to determine whether or not the image is overturned.

The image signal level distributions in the vertical direction and the horizontal direction of the image are typically called a so-called profile, an image signal level distribution in one pixel row extending in the vertical direction and the horizontal direction of the image, and a so-called projection. That is, the vertical distribution of the total value of the image signal levels in each pixel column extending in the horizontal direction and the horizontal distribution of the total value of the image signal levels in each pixel column extending in the vertical direction. It is not limited to them.

As the feature amount, a variance value of the image signal level distribution or a value indicating the symmetry of the image signal level distribution can be used, but other feature amounts representing the image signal level distribution may be used.

Further, the image signal that carries the transparent image is not necessarily the original image signal that constitutes the transparent original image, but the differential image obtained by differentiating the original image or the image signal carrying the binarized binary image (differential value). And binary) are also included.

(Function) There are various kinds of bones in the human body, and these bones usually have a directionality that extends along the vertical direction of the human body. Also, bones in the human body are generally less permeable to radiation than other parts of the human body. Therefore, in the transmission image of the human body, there is generally a portion having a low image signal level corresponding to the bone portion extending in the vertical direction or the horizontal direction of the image.

Therefore, if the distributions of image signal levels such as profiles and projections in the vertical and horizontal directions of the image are compared, the patterns of the distributions in both directions have clear differences, and by comparing the feature quantities representing those distributions, the bone part is compared. It is possible to know whether the extension is in the vertical direction or the horizontal direction of the image, that is, whether the vertical direction and the horizontal direction of the image are the vertical direction and the horizontal direction of the human body, respectively.

Further, as described above, even in a transmission image in which there is no bone portion clearly extending along the vertical direction of the human body, the image signal level distribution in the vertical direction of the human body in the transmission image of each part of the human body and that in the horizontal direction of the human body are Generally, the distribution patterns are greatly different, and the characteristics of these distribution patterns are almost fixed in each part of the human body. Therefore, the characteristics of those patterns or the difference between the two patterns are determined in advance, and the vertical image It is possible to know whether the vertical direction and the horizontal direction of the image are the vertical direction and the horizontal direction of the human body, respectively, by examining the feature quantities representing the image signal level distributions in the horizontal and horizontal directions.

(Advantageous Effects of Invention) A rollover determination method according to the present invention determines whether an image is in a normal position or a rollover position based on a difference between feature amounts representing image signal level distributions in the vertical and horizontal directions of the image. Based on the difference in the feature amount representing the image signal level distribution in the vertical and horizontal directions of the image as described above, it is necessary to know whether the vertical direction and the horizontal direction are the vertical direction or the horizontal direction of the human body. Therefore, if the normal position of the image is determined, the normal position of the image is when the vertical direction of the image is the vertical direction of the human body, or the normal position when the horizontal direction of the image is the vertical direction of the human body. It is possible to easily and accurately determine whether the image is in the normal position or the overturned position according to the determination.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The embodiment described below is an embodiment in which the method according to the present invention is applied to the radiation image information recording / reproducing system described above.

FIG. 1 (a) is a diagram showing a front photographed image of the chest of a human body, and FIG. 1 (b) is a diagram showing a horizontal projection which is one of the image signal level distributions in the vertical direction of the image.
FIG. 6C is a diagram showing a vertical projection which is one of the horizontal image signal level distributions in the image.

In the radiation image information recording system, the image signal that carries the transmission image is read from the stimulable phosphor sheet on which the front radiation transmission image of the chest of the human body is recorded, and this image signal is input to the rollover determination circuit. Whether or not the image is overturned is determined by the following method.

First, a horizontal projection, which is a vertical image signal level distribution of an input image (an image composed of image signals input to the horizontal rollover determination circuit), and a vertical projection, which is a horizontal image signal level distribution, are obtained.

Specifically, the pixel row Li extending in the horizontal direction is set over the entire length in the vertical direction of the image, and the total value of the image signal levels of all the pixels belonging to the pixel row is calculated for each of these pixel rows, and Distribution of the total image signal level in the vertical direction, that is, the horizontal projection shown in FIG. 1 (b) is obtained, and a pixel row Ti extending in the vertical direction is set over the entire horizontal length of the image, and each pixel row Is calculated, the total value of the image signal levels of all the pixels belonging to the pixel column is calculated, and the distribution of the image signal level total values in each pixel column in the horizontal direction, that is, the vertical projection shown in FIG.

In the front image 1 of the human chest shown in the figure, there is a thoracic vertebra 1a extending in the longitudinal direction at the center of the lateral direction of the image. Therefore, the horizontal projection (image signal level distribution in the vertical direction) in this case becomes a linear pattern of substantially the same level with little change over the entire length in the vertical direction as shown in FIG. As shown in FIG. 1 (c), the (horizontal image signal level distribution) has a central depression pattern in which the level greatly decreases at the lateral central position where the thoracic spine exists.

In other words, in the case of front chest imaging, the image signal level distribution in the direction in which the thoracic vertebra extends (longitudinal direction in the illustrated example) has a linear pattern of substantially the same level as shown in FIG. The image signal level distribution in a direction perpendicular to the horizontal direction (horizontal direction in the illustrated example) has a central depressed pattern in which the level greatly decreases at the center as shown in FIG. 1 (c).

Therefore, if the image signal level distributions in the vertical and horizontal directions of the image are obtained and it is determined which of the distribution patterns is the substantially straight type or the central depression type, the vertical direction of the image is the vertical direction of the human body or the horizontal direction. You can know if it is the direction.

The distribution pattern is discriminated by comparing the feature quantities representing those distributions. In this embodiment, the variance value σ ² of both distributions is used as the feature amount. That is, the variance value σ _L ² of the image signal level distribution in the vertical direction is compared with the variance value σ _T ² of the image signal level distribution in the horizontal direction,
It is determined that the one having the larger variance value is the central depression type pattern and the one having the smaller variance value is the linear pattern.

In the above description, the variance value σ ² is a total value X of image signal levels of each pixel column, and the average value of X is E (X).
Means the average value of (XE (X)) ² . Therefore, the variance value of the substantially linear pattern composed of the total values of almost the same level is much smaller than that of the central depression pattern composed of the total values of greatly different levels. It is possible to distinguish.

As described above, when it is determined whether the image signal level distribution in the vertical direction or the horizontal direction of the image is the substantially linear pattern or the central depressed pattern, the vertical direction of the image is the vertical direction of the human body in the horizontal direction. So you can see
Compare the result with the contents of the normal position of the image that has been set in advance (contents that indicate the normal position when the vertical direction of the image is the vertical direction of the human body or the normal position when the vertical direction of the image is the horizontal direction), It is determined whether the image is overturned.

The distribution pattern can be discriminated by a feature amount other than the variance value, for example, the difference between the maximum value and the minimum value.
That is, the difference between the maximum value and the minimum value (X _max -X _min ) is much larger in the central depression type than in the linear pattern, as is clear from FIGS. 1 (b) and (c). Since it becomes large, it is possible to make a distinction by comparing both differences.

FIG. 2 (a) is a view showing a laterally photographed image 2 of the chest of the human body, in which 2a indicates the thoracic spine and 2b indicates the lung field. Also, FIG. 2 (b) is a diagram showing a horizontal projection which is one of the image signal level distributions in the vertical direction of the image, and FIG. 2 (c) is 1 of the horizontal image signal level distribution in the image. It is a figure which shows the vertical direction projection which is one.

Even in the case of this side-captured image, the patterns of both projections are clearly different, and as in the case of the front-captured image, the lateral projection, which is the image signal level distribution in the vertical direction of the human body, is a substantially linear pattern of approximately the same level. The vertical projection, which is the image signal level distribution in the left-right direction of the human body, has a depressed pattern in which the level is greatly reduced at the position where the thoracic spine exists.
Therefore, just as in the case of the front-captured image, using the variance values (σ _L ² , σ _T ² ) of the patterns of both projections and the difference between the maximum value and the minimum value (X _max −X _min ), It is possible to determine whether the horizontal direction is the vertical direction or the horizontal direction of the human body, and it can be determined whether or not the image is overturned.

Further, in the case of a frontal photographed image, the thoracic spine is usually located at the center in the left-right direction of the human body in the image, whereas in the case of a laterally photographed image, it is usually located at a position displaced from the center. Therefore, in the case of a side view image, the pattern of the image signal level distribution in the horizontal direction of the human body does not have symmetry, as shown in FIG. 2 (c). Therefore, in the case of a side-captured image, a value indicating the symmetry of the patterns of both projections is used as the feature amount representing the image signal level distribution, and the vertical and horizontal directions of the image are the vertical direction of the human body or the horizontal direction. It is possible to determine whether it is the direction (the direction with less symmetry is the left-right direction of the human body).

Various values can be used as the value indicating the symmetry scale. For example, the center of the distribution (center of the direction of each distribution of the image, for example, in the case of the image signal level distribution in the vertical direction, the center of the vertical direction of the image, or It is possible to use the cumulative sum of the differences in the data (in this case, the total value X) at the same distance from the distribution center of gravity, etc., and it can be determined that the smaller the cumulative sum, the more symmetry. .

In the above-described embodiment, the horizontal projection and the vertical projection are used as the image signal level distribution in the vertical and horizontal directions of the image, but the present invention is not limited to this. For example, a vertical profile may be used as the vertical image signal level distribution, and a horizontal profile may be used as the horizontal image signal level distribution. Here, the vertical profile means the distribution of the image signal level in an appropriate one pixel column extending in the vertical direction of the image,
The lateral profile means an image signal level distribution in an appropriate one pixel column extending in the lateral direction of the image.
Alternatively, a plurality of such profiles may be selected and added together. Furthermore, a modification of the above-mentioned projection, for example, in the above projection, the total value of the image signal levels in each pixel column is used, but instead of the total value, an average value or a value obtained by uniformly multiplying the total value by a predetermined number, etc. You may use what was used.

Further, in the above embodiment, the image signal level distributions in the vertical and horizontal directions were directly obtained from the input image input to the determination circuit (hereinafter referred to as the original image). However, the original image is processed by appropriate processing. Of the thoracic vertebra in the case of the above-mentioned chest image, for example, an image obtained by raising the thoracic vertebrae, for example, a differential image subjected to differential processing or a binary image binarized with an appropriate threshold value, etc. May be obtained as a differential value and a binary distribution in the case of a binary image.

The differentiation process can be performed by various methods. For example, when the image signal levels of the pixels around the pixel of interest P are a to i as shown in FIG. 3, the differential value dp of the pixel of interest P is , Dp = | a + 2d + g-c-2f-i | + | a + 2d + c-g-2h-i |. As the threshold value, the median value of the profile of the pixel column can be used for each pixel column.

Furthermore, before obtaining the image signal level distribution directly from the original image, or before obtaining the differential image or the like from the original image, an appropriate preprocessing such as sub-sampling with a ratio of 2: 1 to the original image is performed, The subsequent data processing time may be shortened.

As described above in detail, the vertical image signal level distribution pattern and the horizontal image signal level distribution pattern of the human body in the transparent image of the human body are significantly different, and the characteristic difference is depending on the imaging site and the like. Since it can be known in advance, by examining the feature quantities that represent the image signal level distribution in the vertical and horizontal directions of the image, it is possible to know whether the vertical direction and the horizontal direction are the vertical direction or the horizontal direction of the human body. As a result, it is possible to determine whether or not the image is overturned.

The method according to the present invention can be modified in various ways without departing from the scope of the invention, and is not limited to the method described in the above embodiments.

[Brief description of drawings]

FIG. 1 (a) is a diagram showing a front chest image, FIG. 1 (b) is a diagram showing an example of the image signal level distribution in the vertical direction of the image, and FIG. 1 (c) is the horizontal direction of the image. FIG. 2 (a) is a diagram showing a chest side view image, FIG. 2 (b) is a diagram showing an example of the image signal level distribution of the image in the vertical direction, FIG. FIG. 2 (c) is a diagram showing an example of a horizontal image signal level distribution of the image, and FIG. 3 is a diagram showing an example of a differential operator. 1, 2 ... Transparent image of human body (chest)

Claims (5)

[Claims] 1. An image signal level distribution in a vertical direction and a horizontal direction of an image is obtained from an image signal which carries a transparent image of a human body,
An image rollover judging method characterized in that a feature quantity representing each distribution is calculated from each distribution and whether or not the image is overturned is judged by comparing the two feature quantities. 2. The image signal level distribution in the vertical and horizontal directions of the image is an image signal level distribution in one pixel row extending in the vertical and horizontal directions of the image. The method for determining the rollover of an image according to item 1. 3. The image signal level distribution in the vertical direction of the image is a distribution in the vertical direction of the total value of the image signal levels in each pixel column extending in the horizontal direction of the image, and the image in the horizontal direction of the image. The method according to claim 1, wherein the signal level distribution is a distribution in the horizontal direction of the total value of the image signal levels in each pixel column extending in the vertical direction of the image. . 4. The rollover of an image according to any one of claims 1 to 3, wherein the feature amount of the image signal level distribution is a variance value of the image signal level distribution. Judgment method. 5. The feature amount of the image signal level distribution is a value indicating the symmetry of the image signal level distribution, according to any one of claims 1 to 3. Image rollover determination method.