JP3165530B2 - Radiation image reading condition determination method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiographic image reading method for obtaining reading conditions and image processing conditions based on an image signal representing a radiographic image including a desired subject image and a direct radiation portion directly irradiated with radiation. The present invention relates to a method and an apparatus for determining conditions and / or image processing conditions.

[0002]

2. Description of the Related Art A recorded radiographic image is read to obtain an image signal, and the image signal is subjected to appropriate image processing.
Reproduction and recording of images are performed in various fields. For example, an X-ray image is recorded using an X-ray film having a low gamma value designed to be compatible with the subsequent image processing, and the X-ray image is read from the film on which the X-ray image is recorded, and is converted into an electric signal. After converting and subjecting the electric signal (image signal) to image processing, the electric signal (image signal) is reproduced as a visible image in a copy photograph or the like, thereby obtaining a reproduced image having excellent image quality performance such as contrast, sharpness, and graininess. (See Japanese Patent Publication No. 61-5193).

[0003] Further, the applicant of the present invention has proposed that radiation (X-ray, α
Radiation, β-rays, γ-rays, electron beams, ultraviolet rays, etc.), a part of this radiation energy is accumulated, and then, when irradiated with excitation light such as visible light, the accumulated light shows stimulable emission according to the accumulated energy. Using stimulable phosphor (stimulable phosphor)
The radiation image information of a subject such as a human body is temporarily recorded on a sheet-shaped stimulable phosphor, and the stimulable phosphor sheet is scanned with an excitation light such as a laser beam to generate stimulated emission light. A radiation image recording / reproducing system has already been proposed in which the emitted light is photoelectrically read to obtain an image signal, and a radiation image of the subject is output as a visible image to a recording material such as a photographic material or a CRT based on the image data. (JP-A-55-12429, JP-A-56-11395, JP-A-55-163472, and JP-A-56-1)
04645, 55-116340, etc.).

[0004] This system has the practical advantage of being able to record images over a very wide radiation exposure area compared to conventional radiographic systems using silver halide photography. That is, in the case of the stimulable phosphor, it has been recognized that the amount of emitted light that is stimulated by excitation after accumulation is proportional to the radiation exposure amount over an extremely wide range. Even if fluctuates considerably, the amount of the stimulating 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 materials such as photographic photosensitive materials using
By outputting a radiation image as a visible image on a display device such as a CRT, it is possible to obtain a radiation image that is not affected by a change in radiation exposure.

[0005] In the above system, before the image signal is obtained by reading under the optimum reading conditions in accordance with the dose of the radiation applied to the stimulable phosphor sheet or the like, the stimulable phosphor sheet is previously irradiated with a low-level light beam. Perform a pre-read to scan and read the outline of the radiation image recorded on this sheet, analyze the pre-read image signal obtained by this pre-read,
After that, there is a system configured to scan the sheet by irradiating the sheet with a high-level light beam and read the radiation image under optimum reading conditions to obtain an image signal to perform a main reading.

Here, the reading condition is a general term for various conditions that affect the relationship between the amount of stimulated emission light in reading and the output of the reading device. It means the scale factor or the power of the excitation light in reading.

[0007] The high level / low level of the light beam means the magnitude of the energy of the light beam applied per unit area of the sheet or the energy of the photostimulated light emitted from the sheet, respectively. When it depends on the wavelength of the light beam (has a wavelength sensitivity distribution), the weight of the energy of the light beam irradiated per unit area of the sheet is weighted by the wavelength sensitivity. In other words, the method of changing the level of the light beam includes a method of using light beams of different wavelengths, a method of changing the intensity of a light beam emitted from a laser light source or the like, and inserting and removing an ND filter or the like on an optical path of the light beam. Known methods such as a method of changing the intensity of the light beam, a method of changing the scanning density by changing the beam diameter of the light beam, and a method of changing the scanning speed The method of people can be used.

The above-mentioned calculation for obtaining reading conditions and / or image processing conditions (hereinafter referred to as reading conditions, etc.) based on the image signals (including the pre-read image signals) involves statistically processing a large number of radiation images in advance. The algorithm is determined based on the results (see, for example, JP-A-60-185944 and JP-A-61-280163).

As one of the conventionally employed algorithms, there is known a method of obtaining a histogram of an image signal and obtaining a reading condition based on the histogram. Regarding the method of obtaining the reading conditions based on this histogram, when this is subdivided, both the maximum value and the minimum value of the range required as image information are obtained from the histogram of the image signal, and the maximum value and the minimum value are sandwiched between the maximum value and the minimum value. For example, a method of determining reading conditions so that image information within the range can be accurately read in actual reading (see Japanese Patent Application Laid-Open No. 60-156055), only the maximum value is determined from the histogram, and a predetermined value is subtracted from the maximum value A method in which the minimum value is set as the minimum value, and the range between the maximum value and the minimum value is set as the range of the necessary image information (see Japanese Patent Application Laid-Open No. 60-185944). A method in which a value obtained by adding a predetermined value to a value is set as a maximum value, and a range sandwiched between the minimum value and the maximum value is set as a range of necessary image information (see JP-A-61-280163). To How are (see JP 63-233658), a method using a cumulative histogram (see JP-A-61-170730), a method of dividing the histogram into a plurality of small regions by discriminating reference (JP 63-262
For example, a method is known in which a necessary range of image information is obtained by using a number of methods, and the reading conditions are determined based on the obtained range.

[0010]

Although the above method is effective in many cases, it may cause inconvenience depending on the shooting condition of the subject. Hereinafter, this point will be described in detail using a radiation image of the shoulder joint as an example.

FIG. 1A and FIG. 1B are both radiographic images of the shoulder joint 5. In the image of FIG. 1B, the vertebral body 6 is also captured. In the image of FIG. 1A, there is a difference that the position of the subject at the time of photographing is not photographed because the position is shifted. On the other hand, FIG.
The histograms of the respective image signals carrying the radiation image of FIG. 1B are as shown in FIGS. 2A and 2B, respectively.

As shown in the figure, the shapes of both histograms are substantially the same, but since the above-mentioned difference exists between the two radiographic images, the existence range of the image signal bearing the shoulder joint, which is the region of interest, is shown. includes a respective _{K 1} part, _{K 2} parts in both histogram, it becomes different from each other. Therefore, when reading conditions for reproducing a radiographic image as shown in FIGS. 1A and 1B are determined based on each histogram, the density and contrast of the two reproduced radiographic images have the same histogram. Therefore, the same condition is calculated, and the density of the shoulder joint, which is the region of interest, becomes unstable.

This makes it difficult to observe the region of interest of the liver and kidney in the reconstructed radiographic image, or when comparing a plurality of radiographic images for observing the progress of an abnormal part, etc. May make a diagnosis.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has been described in a situation where the density of a specific region of interest easily changes among a plurality of reconstructed radiation images due to a shift in the position of a subject at the time of imaging. It is an object of the present invention to provide a method for determining a radiation image reading condition that ensures that a region of interest is always reproduced stably at an appropriate density.

[0015]

According to a first radiographic image reading condition and / or image processing condition determining method of the present invention, a radiographic image including a desired subject image and a direct radiation section directly irradiated with radiation is provided. The stored stimulable phosphor sheet is irradiated with excitation light and the stimulated emission light emitted from the stimulable phosphor sheet is read, based on a first image signal representing the radiation image obtained and read out. The stimulable phosphor sheet is again irradiated with excitation light, and the stimulated emission light emitted from the stimulable phosphor sheet is read to obtain a second image signal representing the radiation image and / or the reading conditions. In the radiation image reading condition and / or the image processing condition determination method for obtaining image processing conditions when performing image processing on each of the second image signals, the radiation image is obtained based on the first image signal. A first histogram for the body is obtained, an image signal value corresponding to a boundary between the direct radiation section and the subject image is obtained from the first histogram, and a predetermined value is set on the inner side of the subject image from the boundary. A region including a pixel located at a distance equal to or less than the value is defined as a main subject image region, a second histogram of the first image signal corresponding to the main subject image region is obtained, and the reading is performed based on the second histogram. A condition and / or an image processing condition is obtained.

Further, the first radiographic image processing condition determining method of the present invention is a method for determining a radiographic image from a recording sheet on which a radiographic image including a desired subject image and a direct radiation part directly irradiated with radiation is recorded. Based on an image signal representing the radiation image obtained by photoelectrically reading,
In a radiation image processing condition determining method for obtaining image processing conditions when performing image processing on the image signal, a first histogram for the entire radiation image is obtained based on the image signal, and the first histogram is obtained from the first histogram. Obtain an image signal value corresponding to a boundary between the radiation part and the subject image, and set a main subject image region to a region including pixels existing at a distance equal to or less than a predetermined value on the inner side of the subject image from the boundary. A second histogram of the image signal corresponding to the main subject image area is obtained, and the image processing condition is obtained based on the second histogram.

That is, the first radiographic image processing condition determination method is not limited to an image read from a stimulable phosphor sheet, but is intended for a wide range of image signals.

A first radiographic image reading condition and / or image processing condition determining apparatus according to the present invention is for implementing the above-described first radiographic image reading condition and / or image processing condition determining method. In the basic radiation image reading condition and / or image processing condition determination device that implements the above-described first radiation image reading condition and / or image processing condition determination method, the entire radiation image is determined based on the first image signal. A first histogram calculating means for obtaining a first histogram of the image signal value; an image signal value calculating means for obtaining an image signal value corresponding to a boundary between the direct radiation part and the subject image from the first histogram;
Main subject image region setting means for setting a region including a pixel present at a distance equal to or less than a predetermined value inside the subject image from the boundary line as a main subject image region, the first subject image region corresponding to the main subject image region A second histogram calculating means for calculating a second histogram of the image signal, and a reading condition determining means for obtaining the reading condition based on the second histogram.

Further, a first radiographic image processing condition determining apparatus of the present invention is for implementing the above-described first radiographic image processing condition determining method. In a basic radiation image processing condition determining apparatus to be implemented, a first histogram for obtaining a first histogram for the entire radiation image based on the image signal is obtained.
Histogram generating means, histogram analyzing means for obtaining an image signal value corresponding to a boundary between the direct radiation part and the subject image from the first histogram, a predetermined value or less from the boundary to the inside of the subject image Main subject image region setting means for setting a region including a pixel existing at a distance of the main subject image region as a main subject image region; second histogram creating means for obtaining a second histogram of the image signal corresponding to the main subject image region; An image processing condition determining means for obtaining the image processing condition based on the second histogram is provided.

That is, according to the present invention, by setting the main subject image area as described above, the area which affects the density of the region of interest is excluded, and the density of the region of interest is stabilized and made appropriate. It is characterized by the following.

It should be noted that a region including a pixel located at a distance less than a predetermined value from the boundary line to the inside of the subject image includes a region of interest and excludes an inconvenient region that affects the density of the region of interest. It means area. For example, as shown in FIG. 6B, this area can be set by creating a curve at a predetermined distance from the boundary line 10 as the aperture line 7 '.

According to a second method for determining a radiological image reading condition and / or an image processing condition of the present invention, a stimulable fluorescent light on which a radiation image including a desired subject image and a direct radiation part directly irradiated with radiation is recorded. The body sheet is irradiated with excitation light to read the stimulated emission light emitted from the stimulable phosphor sheet, and the stimulable phosphor sheet is again applied to the stimulable phosphor sheet based on the first image signal representing the radiation image. A reading condition for obtaining a second image signal representing the radiation image by reading the stimulated emission light emitted from the stimulable phosphor sheet by irradiating the excitation light sheet and / or the obtained respective second images In a radiological image reading condition and / or an image processing condition determining method for obtaining an image processing condition when performing image processing on a signal, a radiographic image processing method for the entire radiographic image is performed based on the first image signal. Is obtained, an image signal value corresponding to a boundary between the direct radiation part and the subject image is obtained from the first histogram, and an area within a minimum circumscribed rectangle of the boundary is defined as a main subject image area. A second histogram of the first image signal corresponding to the main subject image area is obtained, and the reading condition and / or the image processing condition are obtained based on the second histogram.

Further, a second method for determining a radiation image processing condition according to the present invention is a method for determining a radiation image from a recording sheet on which a radiation image including a desired subject image and a direct radiation part directly irradiated with radiation is recorded. Based on an image signal representing the radiation image obtained by photoelectrically reading, based on the image signal, in a radiation image processing condition determination method for determining image processing conditions when performing image processing on the image signal, A first histogram for the entire radiation image is obtained, and an image signal value corresponding to a boundary between the direct radiation part and the subject image is obtained from the first histogram, and an area within a minimum circumscribed rectangle of the boundary is obtained. As a main subject image area, a second histogram of the image signal corresponding to the main subject image area is obtained, and based on the second histogram, It is characterized in obtaining the image processing conditions.

A second radiation image reading condition and / or image processing condition determining apparatus according to the present invention is for implementing the above-described second radiation image reading condition and / or image processing condition determining method. In the basic radiation image reading condition and / or image processing condition determination device that implements the above-described second radiation image reading condition and / or image processing condition determination method, the entire radiation image is determined based on the first image signal. A first histogram creating means for finding a first histogram of the histogram, a histogram analyzing means for finding an image signal value corresponding to a boundary between the direct radiation part and the subject image from the first histogram, a minimum of the boundary Main subject image area setting means for setting an area within the circumscribed rectangle as a main subject image area, corresponding to the main subject image area A second histogram creating means for obtaining a second histogram of the first image signal; and a reading condition and / or image processing condition determining means for obtaining the reading condition and / or the image processing condition based on the second histogram. It is characterized by having.

A second radiation image processing condition determining apparatus according to the present invention is for implementing the above-described second radiation image processing condition determining method. In a basic radiation image processing condition determining apparatus to be implemented, a first histogram for obtaining a first histogram for the entire radiation image based on the image signal is obtained.
Histogram generating means, histogram analyzing means for obtaining an image signal value corresponding to a boundary between the direct radiation part and the subject image from the first histogram, and defining an area within a minimum circumscribed rectangle of the boundary as a main subject image area Means for setting the main subject image area, second histogram creating means for obtaining a second histogram of the image signal corresponding to the main subject image area, and obtaining the image processing condition based on the second histogram. An image processing condition determining means is provided.

The area within the minimum circumscribed rectangle of the boundary is the smallest rectangle circumscribing the boundary 10 as shown in FIG.

[0027]

According to the method for determining a radiation image reading condition and / or an image processing condition of the present invention, a main subject image region is set based on a first histogram, and a second histogram corresponding to the main subject image region is obtained. Since the final determination of the reading conditions and the like is performed based on the second histogram, even if there is a variation in the positioning at the time of photographing, the reading conditions and / or the image that can always obtain a good density image can be obtained. Image processing conditions can be determined.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

Here, an example will be described in which the above-described stimulable phosphor sheet is used and an X-ray image of a shoulder joint of a human body is taken as a region of interest.

FIG. 3 is a schematic view of an example of the X-ray imaging apparatus. An X-ray 3 from an X-ray source 2 of the X-ray imaging apparatus 1
The X-rays 3a transmitted to the shoulder 4a of the human body and transmitted through the human body 4 are irradiated to the stimulable phosphor sheet 11, so that the transmitted X-ray image of the shoulder 4a of the human body is applied to the stimulable phosphor sheet 11. It is stored and recorded.

FIGS. 1A and 1B are views schematically showing an example of the shoulder X-ray image stored and recorded on the stimulable phosphor sheet 11 as described above. .

Next, an example of an X-ray image reading apparatus including a computer system to which the method for determining a radiation image reading condition according to the embodiment of the present invention is applied will be described in detail.

FIG. 4 is a perspective view showing an example of an X-ray image reading apparatus and an example of a computer system including a radiation image reading condition determining apparatus according to an embodiment of the present invention. This system uses the above-described stimulable phosphor sheet to perform pre-reading.

In an X-ray imaging apparatus (not shown), an X-ray image of the subject is stored and recorded on the stimulable phosphor sheet. The stimulable phosphor sheet 11 on which the X-ray image is recorded is first scanned by a weak light beam to emit only a part of the radiation energy stored in the sheet 11 and read by the pre-reading means 100 for pre-reading. Set to position. The stimulable phosphor sheet 11 set at this predetermined position is conveyed (sub-scanning) in the direction of arrow Y by sheet conveying means 13 such as an endless belt driven by a motor 12. On the other hand, the weak light beam 15 emitted from the laser light source 14 is reflected and deflected by the rotating polygon mirror 16 driven by the motor 23 and rotated at high speed in the direction of the arrow, passes through the focusing lens 17 such as an fθ lens, Is changed, and the light is incident on the sheet 11 and is main-scanned in an arrow X direction substantially perpendicular to the sub-scanning direction (arrow Y direction). From the portion of the sheet 11 to which the light beam 15 has been irradiated, a stimulating luminescent light 19 of a light amount corresponding to the accumulated and recorded radiation image information is diverged, and the stimulating luminescent light 19 is guided by a light guide 20. , Are photoelectrically detected by a photomultiplier (photomultiplier tube) 21. The light guide 20 is formed by molding a light-guiding material such as an acrylic plate, and is arranged such that a linear incident end face 20a extends along a main scanning line on the stimulable phosphor sheet 11. The light receiving surface of the photomultiplier 21 is connected to the emission end face 20b formed in an annular shape. The stimulated emission light 19 entering the light guide 20 from the incident end face 20a is
The light is emitted from the emission end face 20b and received by the photomultiplier 21, and the amount of photostimulated light 19 representing the radiation image is determined by the photomultiplier 21.
Is converted into an electric signal.

The analog output signal S output from the photomultiplier 21 is logarithmically amplified by a logarithmic amplifier 26,
It is digitized by the A / D converter 27, and a pre-read image signal Sp is obtained. The signal level of the pre-read image signal Sp is proportional to the logarithm of the amount of stimulated emission light emitted from each pixel of the sheet 11.

In the pre-reading, the reading conditions, that is, the voltage value applied to the photomultiplier 21 and the amplification factor of the logarithmic amplifier 26 are set so that the radiation energy stored in the stimulable phosphor sheet 11 can be read over a wide area. Etc. are defined.

The obtained pre-read image signal Sp is input to the computer system 40. This computer system
Numeral 40 denotes an example of the radiation image reading condition determining apparatus of the present invention, which includes a main body 41 having a built-in CPU and an internal memory, a drive section 42 into which a floppy disk as an auxiliary memory is inserted and driven, an operator Is composed of a keyboard 43 for inputting necessary instructions and the like to the computer system 40, and a CRT display 44 for displaying necessary information.

In the computer system 40, a first histogram is obtained on the basis of the input pre-read image signal Sp, and a main subject image area including a portion of interest of the subject is set based on the first histogram. A second histogram of the pre-read image signal Sp corresponding to the main subject image area is obtained, and a reading condition at the time of main reading, that is, a sensitivity Sk and a latitude Gp at the time of main reading are obtained based on the second histogram. The voltage value applied to the photomultiplier 21 ', the amplification factor of the logarithmic amplifier 26', and the like are controlled in accordance with the obtained sensitivity Sk and latitude Gp.

Here, the latitude Gp corresponds to the light amount ratio of the strongest stimulated emission light to the weakest stimulated emission light which is converted into an image signal at the time of main reading.
The sensitivity Sk is a photoelectric conversion rate that determines a level of an image signal of a predetermined amount of stimulated emission light.

The stimulable phosphor sheet 11 'for which pre-reading has been completed.
Is set at a predetermined position of the main reading means 100 ', the sheet 11' is scanned by a light beam 15 'stronger than the light beam used for the pre-reading, and an image signal is obtained according to the reading conditions determined as described above. However, since the configuration of the main reading means 100 'is substantially the same as the configuration of the above-mentioned pre-reading means 100, components corresponding to each component of the pre-reading means 100 include
The numbers used in 0 are shown with dashes, and the description is omitted.

The A / D converter image signals S _Q obtained by being digitized at 27 'is again inputted to the computer system 40. Appropriate image processing on the image signal S _Q is a computer system 40 within are subjected, the image signal subjected to the image processing is sent to a not-shown reproducing apparatus,
An X-ray image based on the image signal is reproduced and displayed in the reproducing device.

FIG. 5A is a diagram schematically showing an example of a shoulder X-ray image stored and recorded on the stimulable phosphor sheet 11.
FIG. 5B is a diagram showing a state where the main subject image area is set in FIG. 5A according to the present invention. Similarly, FIG.
(a) is the shoulder X stored and recorded on the stimulable phosphor sheet 11.
FIG. 6B is a diagram schematically illustrating an example of a line image, and FIG. 6B is a diagram illustrating a state in which a main subject image area is set in FIG. 6A according to the present invention. As can be seen from these figures, the main subject image area is set by the aperture lines 7 and 7 ', whereby FIG. 5 (b) excludes the vertebral body 6 of FIG. 5 (a) and FIG. 6 (b) Excludes the lung field 50 in FIG. 6 (a).

In the computer system 40, a first histogram of the X-ray image is obtained based on the pre-read image signal Sp, and the direct irradiation unit 8 directly irradiated with radiation and the subject image 9 are obtained from the first histogram. The image signal value corresponding to the boundary line 10 is determined (see FIGS. 5A and 5B). Next, an area including a pixel within a predetermined distance from the boundary line 10 within the irradiation field is set as a main subject image area by the aperture lines 7 and 7 '(particularly, surrounded by the aperture line 7 in FIG. 5B). A second histogram of the pre-read image signal Sp corresponding to the main subject image area is obtained, and based on the second histogram, the final determination of the reading conditions in the main reading is performed. Do.

As described above, the basic concept of the configuration in which the first histogram is obtained based on the pre-read image signal Sp by the computer system 40 and finally the reading condition is determined based on the second histogram. Is shown in a block diagram in FIG.

That is, as shown in FIG. 7, the basic configuration of the reading condition determining apparatus according to the present invention is such that the above-described radiation image reading condition determining apparatus creates a first histogram from the pre-read image signal Sp. 1 histogram creating means 61 and a histogram analyzing means 62 for calculating an image signal value corresponding to a boundary line from the first histogram.
And a main subject image area setting means 63 for setting a main subject image area including a region of interest from a boundary line indicated by the signal value;
A second histogram creating means 64 for creating a second histogram from only the pixels of the main subject image area, and a reading condition determining means 65 for outputting reading conditions based on the second histogram are provided. The reading condition is finally determined by the reading condition determining means 65.

In the above embodiment, the sensitivity Sk of the image signal and the reciprocal of the latitude Gp are adopted as the read conditions. However, the read conditions may be other values as long as they correspond to the sensitivity and the scale factor. It goes without saying that it is good.

In the above embodiment, the pre-reading means 100 and the main reading means 100 'are configured separately, but as described above, the pre-reading means 100 and the main reading means 100' are substantially the same. For this reason, the pre-reading means 100 and the main reading means 100 'may be integrally used. In this case, after pre-reading, the stimulable phosphor sheet 11 may be backed once and then scanned again to perform main reading.

When the pre-reading means and the main-reading means are used together, it is necessary to switch the light beam intensity between the pre-reading and the main-reading. Various methods can be used, such as a method of switching the number.

[0049] In the above embodiment has described a method for determining the reading condition during the real reading a computer system 40, by the computer system 40 determines the image processing conditions for performing image processing on the image signal S _Q You can also.

That is, the method for determining the reading conditions by the computer 40 using the first and second histograms is as follows.
The present invention can also be applied to determination of image processing conditions when performing various types of image processing on an image signal. In this case, at the time of actual reading, reading is performed under predetermined reading conditions regardless of the pre-read image signal Sp, and the computer system 40 may determine image processing conditions based on the pre-read image signal Sp. Further, the computer system 40 may determine both the reading conditions and the image processing conditions.

Further, in the above embodiment, the present invention is applied to a radiation image reading method for performing pre-reading, but the present invention is also applicable to a radiation image reading method for performing reading equivalent to main reading without pre-reading. is there. In this case, according to the method of the embodiment of the present invention, a first histogram is obtained from an image signal read and obtained by an appropriate method, and a main subject image area is set therefrom. A corresponding second histogram is determined, and an appropriate image processing condition is determined by the computer system based on the second histogram.

Further, the above embodiment for determining the image processing conditions is based on the premise that an image recorded on the stimulable phosphor sheet is read. Not in addition to the conventional X
Of course, the present invention can be applied to a case where an image such as a medical image recorded on a line film is read by an appropriate method and subjected to image processing.

Incidentally, in the radiographic imaging widely used for medical diagnosis and the like, the radiographic imaging is divided into two or four divisions in which a plurality of images are stored and recorded on one stimulable phosphor sheet, or the subject is photographed. In some cases, radiographing is performed with an irradiation field stop that prevents unnecessary parts from being irradiated with radiation. In that case, before creating the first histogram, the division pattern or the irradiation field is recognized from the read image signal, and the first histogram is created only from the pixels within the recognized division pattern or the irradiation field. .

The optimum image processing conditions obtained in this way are input to an image processing apparatus, and the image processing apparatus performs image processing such as gradation processing on the input image signal under the optimum image processing conditions. Will be applied.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an X-ray image of a shoulder joint.

FIG. 2 is a graph showing a schematic pattern of a histogram of an image signal carrying the X-ray image shown in FIG. 1;

FIG. 3 is a schematic diagram of an example of an X-ray imaging apparatus.

FIG. 4 is a perspective view showing an example of an X-ray image reading apparatus and an example of a computer system for implementing the present invention.

FIG. 5 is an explanatory diagram showing an X-ray image of a shoulder joint.

FIG. 6 is an explanatory diagram showing an X-ray image of a shoulder joint.

FIG. 7 is a block diagram illustrating a basic concept of a method according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray imaging apparatus 2 X-ray source 5 Shoulder joint 11, 11 'Storable phosphor sheet 19, 19' Stimulated luminescence 21, 21 'Photomultiplier 26, 26' Logarithmic converter 27, 27 'A / D Converter 40 Computer system 61 First histogram calculating means 62 Image signal value calculating means 63 Main subject image area setting means 64 Second histogram calculating means 65 Reading condition determining means 100 Pre-reading means 100 'Main reading means

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03B 42/02 A61B 6/00 G06T 1/00 H04N 1/04

Claims (8)

(57) [Claims] 1. A stimulable phosphor sheet on which a radiation image including a desired subject image and a direct radiation part directly irradiated with radiation is recorded is irradiated with excitation light and emitted from the stimulable phosphor sheet. The stimulable phosphor sheet is again irradiated with excitation light based on a first image signal representing the radiation image obtained by reading the stimulable luminescence light, and the stimulable luminescence emitted from the stimulable phosphor sheet is emitted. A radiation image reading condition for obtaining a reading condition when reading light and obtaining a second image signal representing the radiation image and / or an image processing condition when performing image processing on the obtained second image signal; And / or in the image processing condition determining method, a first histogram for the entire radiographic image is obtained based on the first image signal, and the first radiograph and the direct radiographic part are obtained from the first histogram. An image signal value corresponding to a boundary line with the subject image is obtained, and an area including a pixel located at a distance equal to or less than a predetermined value inside the subject image from the boundary line is defined as a main subject image area. A second histogram of the first image signal corresponding to a region is obtained, and based on the second histogram, the reading condition and / or
Alternatively, a method for determining a radiation image reading condition and / or an image processing condition, wherein an image processing condition is obtained. 2. A radiation image obtained by photoelectrically reading the radiation image from a recording sheet on which a radiation image including a desired subject image and a direct radiation part directly irradiated with radiation is recorded. A radiation image processing condition determining method for determining an image processing condition when performing image processing on the image signal based on the image signal; determining a first histogram for the entire radiation image based on the image signal; An image signal value corresponding to a boundary between the direct radiation part and the subject image is obtained from the histogram of 1, and an area including a pixel existing at a distance equal to or less than a predetermined value from the boundary to the inside of the subject image is determined. Determining a second histogram of the image signal corresponding to the main subject image area; and determining the image based on the second histogram. Radiation image processing condition determining method characterized by determining the physical condition. 3. A stimulable phosphor sheet on which a radiation image including a desired subject image and a direct radiation part directly irradiated with radiation is recorded is irradiated with excitation light and emitted from the stimulable phosphor sheet. The stimulable phosphor sheet is again irradiated with excitation light based on a first image signal representing the radiation image obtained by reading the stimulable luminescence light, and the stimulable luminescence emitted from the stimulable phosphor sheet is emitted. A radiation image reading condition for obtaining a reading condition when reading light and obtaining a second image signal representing the radiation image and / or an image processing condition when performing image processing on the obtained second image signal; And / or an image processing condition determining device, wherein: a first histogram creating means for obtaining a first histogram for the entire radiation image based on the first image signal; Histogram analysis means for obtaining an image signal value corresponding to a boundary line between the direct radiation section and the subject image from a direct image, an area including pixels present at a distance equal to or less than a predetermined value from the boundary line to the inside of the subject image A main subject image area setting means for setting a main subject image area; a second histogram creating means for obtaining a second histogram of the first image signal corresponding to the main subject image area; A radiation image reading condition and / or image processing condition determining apparatus, comprising: reading condition and / or image processing condition determining means for obtaining the reading condition and / or image processing condition based on the reading condition and / or image processing condition. 4. A radiation image obtained by photoelectrically reading the radiation image from a recording sheet on which a radiation image including a desired subject image and a direct radiation part directly irradiated with radiation is recorded. A radiation image processing condition determining apparatus for determining an image processing condition when performing image processing on the image signal based on the image signal; a first histogram for obtaining a first histogram for the entire radiation image based on the image signal; Histogram creation means, Histogram analysis means for obtaining an image signal value corresponding to a boundary between the direct radiation part and the subject image from the first histogram, and a predetermined value equal to or less than a predetermined value inside the subject image from the boundary. Main subject image region setting means for setting a region including a pixel present at a distance as a main subject image region; A radiation image processing condition determination unit comprising: a second histogram creation unit that determines a second histogram of the image signal; and an image processing condition determination unit that determines the image processing condition based on the second histogram. apparatus. 5. A stimulable phosphor sheet on which a radiation image including a desired subject image and a direct radiation part directly irradiated with radiation is recorded is irradiated with excitation light and emitted from the stimulable phosphor sheet. The stimulable phosphor sheet is again irradiated with excitation light based on a first image signal representing the radiation image obtained by reading the stimulable luminescence light, and the stimulable luminescence emitted from the stimulable phosphor sheet is emitted. A radiation image reading condition for obtaining a reading condition when reading light and obtaining a second image signal representing the radiation image and / or an image processing condition when performing image processing on the obtained second image signal; And / or in the image processing condition determining method, a first histogram for the entire radiographic image is obtained based on the first image signal, and the first radiograph and the direct radiographic part are obtained from the first histogram. An image signal value corresponding to a boundary line with the subject image is obtained, an area within the minimum circumscribed rectangle of the boundary line is set as a main subject image area, and a second image signal of the first image signal corresponding to the main subject image area is obtained. Obtaining a histogram, and based on the second histogram, the reading condition and / or
Alternatively, a method for determining a radiation image reading condition and / or an image processing condition, wherein an image processing condition is obtained. 6. A radiation image obtained by photoelectrically reading a radiation image from a recording sheet on which a radiation image including a desired subject image and a direct radiation portion directly irradiated with radiation is recorded. A radiation image processing condition determining method for determining an image processing condition when performing image processing on the image signal based on the image signal; determining a first histogram for the entire radiation image based on the image signal; An image signal value corresponding to a boundary line between the direct radiation part and the subject image is obtained from the histogram of No. 1 and an area within a minimum circumscribed rectangle of the boundary line is set as a main subject image area. Radiation image processing, wherein a second histogram of the image signal is obtained, and the image processing condition is obtained based on the second histogram. Matter determination method. 7. A stimulable phosphor sheet on which a radiation image including a desired subject image and a direct radiation part directly irradiated with radiation is recorded is irradiated with excitation light and emitted from the stimulable phosphor sheet. The stimulable phosphor sheet is again irradiated with excitation light based on a first image signal representing the radiation image obtained by reading the stimulable luminescence light, and the stimulable luminescence emitted from the stimulable phosphor sheet is emitted. A radiation image reading condition for obtaining a reading condition when reading light and obtaining a second image signal representing the radiation image and / or an image processing condition when performing image processing on the obtained second image signal; And / or an image processing condition determining device, wherein: a first histogram creating means for obtaining a first histogram for the entire radiation image based on the first image signal; Histogram analysis means for obtaining an image signal value corresponding to a boundary between the direct radiation section and the subject image from a direct image system; main subject image area setting means for setting an area within a minimum circumscribed rectangle of the boundary as a main subject image area A second histogram creating means for obtaining a second histogram of the first image signal corresponding to the main subject image area; and a reading for obtaining the reading condition and / or the image processing condition based on the second histogram. A radiation image reading condition and / or image processing condition determining device, comprising a condition and / or image processing condition determining means. 8. A radiation image obtained by photoelectrically reading a radiation image from a recording sheet on which a radiation image including a desired subject image and a direct radiation portion directly irradiated with radiation is recorded. A radiation image processing condition determining apparatus for determining an image processing condition when performing image processing on the image signal based on the image signal; a first histogram for obtaining a first histogram for the entire radiation image based on the image signal; Histogram creating means, Histogram analyzing means for obtaining an image signal value corresponding to a boundary between the direct radiation part and the subject image from the first histogram, and defining an area within a minimum circumscribed rectangle of the boundary as a main subject image area Main subject image area setting means for setting, a second histogram for obtaining a second histogram of the image signal corresponding to the main subject image area Histogram creating means, and the radiation image processing condition determining apparatus comprising the image processing condition determining means for determining the image processing conditions based on the second histogram.