JPH06304160A - Method for recognizing picture photographing position - Google Patents

Abstract

PURPOSE:To provide the method for recognizing picture photographing position capable of discriminating the photographing position at ease. CONSTITUTION:An arithmetic element obtains a picture signal Smax showing the maximum value from a picture signal Si inputted to a picture processor. A subject is the soft part of the neck of the human and the front picture is the one as the result irradiating the subject with the X-ray more powerful than the side picture. Thus, in the extracted part of the front picture, the picture signal Smax showing the detected maximum value is the value higher than the picture signal Smax showing the maximum value detected in the extracted section of the side picture. The picture signal Smax being the maximum value and the threshold value K which is set based on the other sample are compared. When the picture signal Smax is higher than or equal to the threshold value K, the picture is judged to be the front picture. When the picture signal Smax is lower than the threshold value, the picture is judged to be the side picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of recognizing a body position of an image, and more particularly to a method of automatically determining a body position of an image such as a radiation image.

[0002]

2. Description of the Related Art Radiation (X rays, α rays,
When β-rays, γ-rays, electron beams, ultraviolet rays, etc.) are irradiated, a part of this radiation energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, It is known that phosphors exhibit stimulated emission, and phosphors exhibiting such properties are called stimulable phosphors (stimulable phosphors). Using this stimulable phosphor, the radiation image information of a subject such as a human body is once recorded on a stimulable phosphor sheet, and the stimulable phosphor sheet is scanned with excitation light such as laser light to stimulate emission. An image signal is obtained by photoelectrically reading the obtained stimulated emission light by generating light, and based on this image signal, a radiation image of the subject is visible on a recording material such as a photographic light-sensitive material or a display device such as a CRT. The present applicant has already proposed a radiation image information recording / reproducing system for outputting as a radiographic image (for example, Japanese Patent Laid-Open Nos. 55-12429 and 56-11395). This system is a conventional radiographic system using silver salt photography. It has the practical advantage of being able to record images over a very wide radiation exposure area. That is, in the stimulable phosphor, it has been recognized that the amount of emitted light stimulated by excitation after storage is proportional to the radiation exposure dose over a very wide range, and therefore the radiation exposure dose varies depending on various imaging conditions. Even if it fluctuates significantly, the amount of stimulated emission light emitted from the stimulable phosphor sheet is read by the photoelectric conversion means with the reading gain set to an appropriate value and converted into an electric signal. Recording material such as photographic light-sensitive material, CRT
By outputting the radiation image as a visible image on a display device such as the above, it is possible to obtain a radiation image that is not affected by variations in the radiation exposure amount.

By the way, in order to obtain an output image excellent in observation and interpretation suitability from a signalized image, including the system described above, a recording pattern of the recorded image information or a recording pattern determined by a photographing method or the like is used. In some cases, the image is grasped prior to the output of a visible image for observation and interpretation, and image processing such as gradation processing is performed according to the contrast of the recording pattern.

A method disclosed in Japanese Patent Laid-Open No. 58-67240 is known as a method of grasping the recorded information of an image before outputting a visible image.

However, if the image processing conditions are determined by the above-mentioned method, when the same subject is photographed in different photographing positions, the density of the region of interest in the subject may change in each reproduced image. For example, in the case of capturing a radiographic image, when the same subject is imaged from the front and the non-region of interest overlapping the region of interest and the non-region of interest overlapping from the side region of the region of interest are different, However, the amount of recorded light varies depending on the difference in the radiation transmittance of the non-interested region, which causes a change in the conditions for image processing performed thereafter.

In order to solve the above-mentioned problems, conventionally, when reading a radiation image information from a stimulable phosphor sheet, it is necessary to read the position of the subject on the sheet one by one. Alternatively, it is inputted to the image processing apparatus, and the above-mentioned reading condition and / or image processing condition is set according to the inputted photographing body position information. However, it is very troublesome to input the above-mentioned image-taking position information every time each stimulable phosphor sheet is read, and it is easy to mistakenly input the image-taking position information.

Therefore, the applicant of the present application has developed a method capable of automatically discriminating the photographing position of an image recorded on the above-mentioned stimulable phosphor sheet or the like, and has already applied for a patent (Japanese Patent Laid-Open No. 63-63). -262128 publication). This method creates a cumulative histogram of the image signal that carries the transparent image of the subject,
The rate of change of a predetermined portion of the cumulative histogram is obtained, and the imaged posture of the image is determined based on the value of the rate of change.

[0008]

By the way, when a front image and a side image of the same subject are respectively photographed, in order to record the side dose image and the amount of radiation that is normally irradiated to record the front image. The magnitude of the dose of the radiation to be irradiated on is set to a different value. This is to improve the observation / interpretation performance for the region of interest because the radiation transmission dose distribution varies depending on the imaged body position of the subject.

As described above, for an image in which it is recognized in advance that the radiation dose to be irradiated differs depending on the photographing position, a histogram is created for the image signal values of all the pixels forming the image. When I made it and decided the posture, I didn't take advantage of the characteristics of the shooting conditions,
It is not possible to shorten the time required for the complicated arithmetic processing for recognizing the body position.

The present invention has been made in view of the above circumstances, and for images having different radiation doses irradiated depending on the photographing position, the history of the difference in the radiation doses at the time of photographing is utilized, An object of the present invention is to provide a method for recognizing a shooting position of an image, which can easily determine the shooting position.

[0011]

A method for recognizing a body position of an image according to the present invention discriminates the body position by utilizing the characteristic at the time of photographing that the radiation dose applied to a subject is different depending on the body position. Is.

That is, as described in claim 1, the amount of radiation emitted to record a front image of a subject and the amount of radiation emitted to record a side image of the subject are A method of recognizing a shooting position of an image recorded with different values set, in which a size corresponding to a radiation dose is applied from the image thus recorded to all pixels constituting the image. The image signal having the value of is read for each pixel, the maximum value of the values of these image signals is obtained, the maximum value is compared with the preset threshold value, and based on this comparison, It is characterized by determining whether the image is a front image or a side image.

Here, the maximum value of the value of the image signal is detected in a so-called blank portion when the radiation is directly applied to the image recording medium without passing through the subject.

The threshold value is a value set for each of various objects, and for example, as a result of irradiating a proper dose of radiation for each imaging position of the object, the above-mentioned image is recorded from the image of the object. The maximum value of the signal values is obtained, the maximum value of the image signal values obtained from the front image of the subject is S ₁ max, and the maximum value of the image signal values obtained from the side image is S ₂ max ( However, S ₂ max <S ₁ max)
If the threshold value is K, this threshold value K is S ₂ ma
It is a value set so that x <K <S ₁ max.

[0015]

Since the recorded image has accumulated and recorded the energy of the intensity corresponding to the radiation dose irradiated at the time of recording, conversely, the energy of the recorded image is read to irradiate the image. The amount of radiation delivered can be estimated. In particular, since the above-mentioned stimulable phosphor has a wide latitude, it is possible to easily obtain the magnitude of the applied radiation dose.

In the image-capturing body position recognition method of the present invention, the amount of radiation applied to the subject when recording the front image differs from the amount of radiation applied to the subject when recording the side image. By using this, it is possible to determine whether the image is a front image or a side image.

That is, the maximum value of the image signal obtained by reading one of the front image and the side image obtained by changing the photographing position from the same subject is measured in advance as a reference image. Whether the image is a front image depending on whether it is greater than a threshold value set to a value between the maximum value of the image signal in the front image and the maximum value of the image signal in the side image It is possible to determine whether it is a side image.

As described above, according to the image-capturing body position recognizing method of the present invention, the difference in the image-capturing conditions is applied to an image in which it is recognized in advance that the radiation dose to be irradiated differs depending on the image-capturing body position. By effectively using, it is not necessary to perform a complicated calculation process, and thus it is possible to easily recognize the photographing body position.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of an example of a radiation imaging apparatus. The radiation 12 is emitted from the radiation source 11 of the radiation imaging apparatus 10 toward the subject 13, and the radiation that has passed through the subject 13 is applied to the stimulable phosphor sheet 14, whereby the subject
The transmitted radiation image of 13 is accumulated and recorded on the stimulable phosphor sheet 14. This radiation imaging apparatus 10 is capable of arbitrarily setting the dose of the radiation 12 to be irradiated by the operation of the operator, and it is desirable that the subject 13 be changed in the dose of the radiation 12 to be irradiated according to its imaging position. is there. Such subjects include, for example, the pharynx, larynx, legs, abdomen, and lumbar region (pelvis) of the human body. Of these, the lumbar region is irradiated with radiation 12 for recording side images. The dose value of is set to be larger than the dose value of the radiation 12 irradiated to record the front image,
For other parts, the dose value of the radiation 12 irradiated to record the front image is set to be larger than the dose value of the radiation 12 irradiated to record the side image.
In this embodiment, the subject 13 is the soft part of the neck of the human body (pharyngeal larynx), and when the front image is taken, a large dose of radiation is irradiated from the radiation source 11 to the subject 13, while
When capturing a side image, the subject 13 is irradiated with a small dose of radiation from the radiation source 11, and the stimulable phosphor sheet
In 14, the radiographic images of the subject 13 for each body position are stored and recorded.

FIG. 2 is a perspective view showing an example of a radiographic image reading apparatus, and FIG. 3 shows a subject 13 (in the figure, a cervical soft part (pharyngeal larynx) of a human body) stored and recorded in a stimulable phosphor sheet 14. (Shown) is a radiation image, (A) is a front image,
(B) is a diagram showing a side image.

An image is taken by the radiation imaging apparatus shown in FIG. 1, and the stimulable phosphor sheet 14 on which the radiation image is recorded is set at a predetermined position of the reading section 20.

When the stimulable phosphor sheet 14 is set at a predetermined position of the reading section 20, the sheet 14 is conveyed (sub-scanned) in the arrow Y direction by the endless belt 22 driven by the motor 21. On the other hand, a light beam 24 emitted from a laser light source 23 is reflected and deflected by a rotating polygon mirror 26 driven by a motor 25 and rotating at a high speed in the direction of an arrow, and passes through a focusing lens 27 such as an fθ lens, and then an optical path by a mirror 28. Instead, the light is incident on the sheet 14 and the main scanning is performed in the arrow X direction that is substantially perpendicular to the sub-scanning direction (arrow Y direction). From the position where the excitation light 24 of the sheet 14 is irradiated, the stimulated emission light 29 of a light amount corresponding to the radiation image information stored and recorded is diverged,
The stimulated emission light 29 is guided by a light guide 30 and photoelectrically detected by a photomultiplier (photomultiplier tube) 31. The light guide 30 is made by molding a light guide material such as an acrylic plate, and has a linear incident end surface.
30a is arranged so as to extend along the main scanning line on the stimulable phosphor sheet 14, and the light receiving surface of the photomultiplier 31 is coupled to the emission end surface 30b formed in an annular shape. The stimulated emission light 29 entering the light guide 30 from the incident end face 30a is
In FIG. 1, the photomultiplier 31 travels through the inside of the light guide 30 by repeating total reflection and is emitted from the emission end face 30b.
The photostimulated luminescent light 29 representing the radiation image is converted into an electric signal by the photomultiplier 31.

The analog output signal S0 output from the photomultiplier 31 is logarithmically amplified by the logarithmic amplifier 32 and digitized by the A / D converter 33, whereby the image signal Si is obtained and the image processing device 40 Entered in. This image processing device 40 is a C for reproducing and displaying a visible image.
An RT display 41, a main body 42 having a CPU, an internal memory, an interface and the like built therein, a floppy disk drive 43 in which a floppy disk is loaded and driven,
And a keyboard 44 for inputting information necessary for this radiation image reading apparatus.

The internal memory of the image processing device 40 is provided with a computing element that performs the following functions. That is, of the input pixel signals Si indicating these pixels over all the pixels forming the image (for convenience of explanation, the value of this image signal Si is also called Si), the image signal S having the maximum value
max is extracted, and the magnitudes of the extracted image signal Smax indicating the maximum value and a preset threshold value K are compared. As a result of this comparison, the maximum value image signal Smax is greater than the threshold value K. If they are equal to or larger than each other, it is determined that this image is a front image, and the first image processing condition in the subsequent image processing is selected. On the other hand, if the threshold value K is larger than the maximum value image signal Smax, this image is a side image. It is determined that the image is an image, and the second image processing condition in the subsequent image processing is selected.

For example, regarding the soft part of the neck (pharynx and larynx) shown in FIG. 3, the front image is recorded with the region of interest (pharynx) overlapping the cervical spine, while the lateral image shows only the region of interest (pharynx). Will be recorded. Therefore, the imaging conditions for imaging the soft part of the neck (pharynx and larynx) are usually larger (stronger) in both the amount of radiation and the energy irradiated when a front image is taken than when a side image is taken. Is.
That is, the maximum value of the signal indicating the intensity of the irradiated radiation amount / energy obtained from the recorded front image is
It is generally higher than that obtained from lateral images.

Here, the threshold value K is an image signal obtained from the front image of another sample when the neck soft part (pharyngeal larynx) is recorded with an optimum radiation dose for obtaining the front image. And the maximum value S ₁ max of the image signal obtained from the lateral image when the soft part of the neck (pharyngeal larynx) of the human body is recorded with the optimum radiation dose for obtaining the lateral image. It is a value set so as to satisfy S ₁ max>K> S ₂ max based on ₂ max (where S ₁ max> S ₂ max) and is stored in advance in this arithmetic element.

FIG. 4 is a diagram showing a flowchart of the arithmetic element in the above memory.

The operation of this arithmetic element will be described in detail below with reference to FIGS. 3 and 4. When the image signal Si is input to the image processing device 40, the image signal Si is first stored in the image signal memory and sequentially output therefrom, and the image signal Smax having the maximum value is extracted. As shown in FIG. 3, the extracted image signal Smax is obtained by irradiating the stimulable phosphor sheet 14 with the radiation 12 without passing through the subject 13.
It exists in the so-called blank part.

As described above, the subject 13 is the soft part of the neck of the human body (pharyngeal larynx), and the front image is an image obtained by irradiating the subject 13 with radiation having a larger dose than the side image. The image signal Smax showing the maximum value detected in the blank portion of the front image shown in FIG.
The value is larger than the image signal Smax indicating the maximum value detected in the blank portion of the side image shown in (B).

Next, the image signal Smax, which is the maximum value,
When the image signal Smax is greater than or equal to the threshold value K, it is determined that this image is a front image, and in the subsequent image processing, the front Select the first image processing condition suitable for the image,
On the other hand, when the image signal Smax is smaller than the threshold value, it is determined that this image is the side image, and the second image processing condition suitable for the side image is selected in the subsequent image processing.

When it is determined that the image stored and recorded is the front side image processing, the first image processing condition suitable for the front side image is selected in the subsequent image processing, and the side image processing is determined. In this case, the second image processing condition suitable for the side image is selected and the appropriate image processing is performed.

After that, the image signal subjected to the appropriate image processing is sent to an image reproducing device (not shown) and is used for reproducing the radiation image.

As described above, according to the image-capturing body position recognizing method of the present embodiment, the difference in the image-capturing conditions for the images in which it is previously recognized that the radiation dose to be irradiated differs depending on the image-capturing body position. By effectively using, it is not necessary to perform complicated calculation processing, and therefore the imaged posture of the image can be easily recognized.

Whether the photographed image is a front image,
Even if the subsequent image processing method is different depending on whether the image is a side image, the shooting position of the image can be automatically recognized according to the shooting position recognition method of the present invention. It is possible to automate the switching of the subsequent processing method based on the above.

In this embodiment, the image information read from the image information recorded on the stimulable phosphor sheet by using the radiation image reading device is used as a photographing position in a so-called CR (Computed Radiography) system. Although the recognition method has been described, the image capturing body position recognition method of the present invention is not limited to the image described in the above-mentioned embodiment, and if the history indicating the radiation dose applied to the subject is recorded, the image The present invention can also be applied to various types of images such as image information obtained by converting the image into a signal from a recorded film or the like, or an image recorded from the beginning by being signalized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a radiation imaging apparatus.

FIG. 2 is a perspective view showing an example of a radiation image reading apparatus.

FIG. 3 is a front view image and FIG. 3B is a side view image showing a radiation image of a cervical soft part (pharyngeal larynx) of a human body stored and recorded on a stimulable phosphor sheet.

FIG. 4 is a diagram showing a flowchart of a computing element.

[Explanation of symbols]

 10 Radiography device 14 Storage phosphor sheet 23 Laser light source 24 Laser light 29 Photostimulated emission light 40 Image processing device 44 Keyboard

Claims (1)

[Claims] 1. The magnitude of the dose of radiation applied to record a front image of a subject and the magnitude of the dose of radiation applied to record a side image of the subject are set to different values and recorded. From each image, an image signal having a value having a magnitude corresponding to the irradiated radiation amount is read for each pixel over all the pixels forming the image, the maximum value of the value of the image signal is calculated, and the maximum value is calculated. A method for recognizing an imaged posture of an image, which compares a value with a preset threshold value, and determines whether the image is a front image or a side image based on the comparison.