JPH06308637A - Radiation image reading method - Google Patents

Abstract

PURPOSE:To determine the reading conditions, etc., meeting a radiation dose by detecting a photographing error and a setting error of reading conditions and/or image processing conditions with good accuracy even in the case of a fluctuation in the radiation dose at the time of photographing in the radiation image reading method. CONSTITUTION:A reference range is first determined by subtracting prescribed widths L1, L2 from the max. value Smax 0 of the image signal indicating the radiation image having the direct radiation part irradiated with direct radiations and calculating the lower limit value Skmin and upper limit value Skmax of the reference range. Whether the sensitivity central value Skm of the reading conditions and/or image processing conditions obtd. in accordance with the image signal exists within the reference value or not is decided. The reading conditions, etc., are decided to be normal if the value exists in the range. The reading conditions, etc., meeting the image signal are determined by using the predetermined reading conditions, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reading condition and / or a reading condition for obtaining an image signal based on an image signal representing a radiation image.
Alternatively, the present invention relates to a radiation image reading method for obtaining image processing conditions when performing image processing on an image signal.

[0002]

2. Description of the Related Art An image signal is obtained by reading a recorded radiation image, and after subjecting this image signal 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 suitable for the subsequent image processing,
The X-ray image is read from the film on which the X-ray image is recorded, converted into an electric signal, and the electric signal (image signal) is subjected to image processing, and then reproduced as a visible image on a copy photograph or the like to obtain a contrast. , Reproduced images with good image quality performance such as sharpness and graininess are being obtained (see Japanese Patent Publication No. 61-5193).

In addition, the applicant of the present invention has proposed radiation (X-ray,
When irradiated with α-rays, β-rays, γ-rays, electron rays, ultraviolet rays, etc.), a part of this radiation energy is accumulated, and when excitation light such as visible light is subsequently irradiated, stimulated luminescence is displayed according to the accumulated energy. By using a stimulable phosphor (stimulable phosphor), the radiation image information of a subject such as a human body is once recorded on a sheet-shaped stimulable phosphor, and this stimulable phosphor sheet is excited by a laser beam or the like. Scan to generate stimulated emission light, photoelectrically read the obtained stimulated emission light to obtain an image signal,
A radiation image recording / reproducing system for outputting a radiation image of a subject as a visible image on a recording material such as a photographic light-sensitive material or a CRT based on this image data has already been proposed (JP-A-55-12429, JP-A-56-56). No. 11395, No. 55-163472,
56-104645, 55-116340, etc.).

This system has the practical advantage of being able to record images over a very wide radiation exposure area as compared to conventional radiographic systems using silver halide photography. 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,
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 variations in radiation exposure dose.

In the above system, the stimulable phosphor sheet is previously irradiated with a low-level light beam before the image signal is obtained by reading the stimulable phosphor sheet under optimum reading conditions according to the dose of radiation applied to the stimulable phosphor sheet. Scan ahead to read the outline of the radiation image recorded on this sheet,
The pre-reading image signal obtained by this pre-reading is analyzed, and then the sheet is irradiated with a high-level light beam and scanned,
There is a system configured to perform a main reading in which an image signal is obtained by reading the radiation image under optimum reading conditions.

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. For example, the reading gain that determines the input / output relationship, It means the scale factor or the power of the excitation light in reading.

Further, the high level / low level of the light beam means the large / small amount of energy of the light beam irradiated per unit area of the sheet, or the energy of stimulated emission light emitted from the sheet, respectively. When it depends on the wavelength of the light beam (has a wavelength sensitivity distribution), the large / small of the weighting energy after the energy of the light beam irradiated per unit area of the sheet is weighted by the wavelength sensitivity. As a method of changing the level of the light beam, a method of using a light beam of a different wavelength, a method of changing the intensity of the light beam emitted from a laser light source, etc., an ND filter or the like is inserted or removed on the optical path of the light beam. By changing the beam intensity of the light beam, changing the beam density of the light beam to change the scanning density, changing the scanning speed, etc. The method of people can be used.

In addition, regardless of whether the system performs the prefetching or the system that does not perform the prefetching, the obtained image signal (including the prefetched image signal) is analyzed, and the optimum image when the image processing is performed on the image signal is performed. There is also a system that determines processing conditions. The method of determining the optimum image processing condition based on this image signal is not limited to the system using the stimulable phosphor sheet, and an image signal is obtained from a radiation image recorded on a recording sheet such as a conventional X-ray film. It is also applied to the system.

The calculation for obtaining the reading condition and / or the image processing condition based on the image signal (including the pre-read image signal) (hereinafter, referred to as EDR) is a photographing part of the subject (the head when the subject is a human body). A large number of image signals obtained from each of a large number of radiographic images classified according to imaging conditions such as a chest, abdomen, etc.), an imaging method (normal imaging, contrast imaging, magnified imaging, etc.) are statistically processed. From the results, the algorithm is determined for each photographing condition, and EDR is widely performed automatically.

However, since the EDR algorithm is determined on the basis of the result of statistical processing as described above, even if the algorithm is determined for each imaging condition, it is applied to all radiation images. Not compatible. When EDR is incompatible, when a visible image is reproduced and output based on the image signal obtained from the radiation image,
There is a problem that a visible image with inappropriate density and contrast is output that is unbearable for observation. In the worst case, the output visible image does not include the necessary image information, and There is also a problem that it is necessary to start over from photography, which wastes time, and when the subject is a human body, the radiation dose to the human body is doubled by another photography.

An example of the case where the above problems occur will be described below.

One of the conditions to be taken into consideration when determining the EDR algorithm is that unnecessary portions recorded on the recording sheet at the time of photographing, for example, only scattered radiation or the object is not transmitted (transmitted or reflected). That is, the portion where the radiation is directly applied to the recording sheet is removed, and the image signal corresponding to the necessary radiation image is distinguished from the unnecessary image signal.

FIGS. 5 and 6 respectively show the pre-read image signal Sp.
It is a figure which shows the histogram of. These figures are for the system for pre-reading using the stimulable phosphor sheet described above.

FIG. 5 shows an example of a histogram obtained from a radiation image suitable for EDR, which occupies most (for example, 99.5%) of many radiation images.

In the pre-reading, the pre-reading image signal Sp, which is obtained by reading the stimulated emission light emitted from the stimulable phosphor sheet in the pre-reading, and which is proportional to the logarithm of the amount of the stimulated emission light, is plotted on the horizontal axis. The frequency of appearance of each value of the signal Sp is plotted on the vertical axis (upper), and further, the image signal obtained by the main reading, which is proportional to the logarithmic value of the light amount of stimulated emission light, is plotted on the lower vertical axis. At this time, the histogram obtained from the preread image signal Sp is composed of three peaks A, B, and C as shown in the figure, and the part corresponding to the necessary radiation image is the part of the peak B. At this time, in order to find the mountain B, for example, a search is performed in the direction in which the value of the preread image signal Sp increases from the position of the minimum value S _L of the preread image signal Sp at the threshold value T (two-dot chain line in the figure. Find the second rising point a and the next falling point b. When the maximum value and the minimum value of the range sandwiched between these two points a and b are Smax (corresponding to point b) and Smin (corresponding to point a), the image information included in this range becomes a visible output image. The reading conditions in the main reading are set so that the reproduction is properly performed. That is, Smax and Smin in the preread image signal Sp are
The reading condition of the main reading is such that the maximum image signal Qmax and the minimum image signal Qmin corresponding to the maximum density Dmax and the minimum density Dmin of the proper density range in the visible output image are obtained in the main reading, that is, along the straight line G in the figure. Is determined.

In this way, the reading conditions for the main reading are set correctly for almost the majority of radiation images, but in this case, the correct reading conditions cannot be found in rare cases.

FIG. 6 is a diagram showing a histogram obtained from a radiation image obtained by photographing a subject (for example, the chest of a human body) similar to that shown in FIG. 5 under the same photographing condition.

Comparing FIG. 5 with FIG. 6, peaks B'and C'are similar to peaks B and C, respectively, but peak A'is different from peak A, and two peaks A ₁ 'and A ₂ '. It is divided into

When the above-mentioned method is applied to the histogram of FIG. 6, the pre-read image signal Sp at a predetermined threshold value T is obtained.
Is searched in the direction in which the value of the pre-reading image signal Sp increases from the position of the minimum value S _L ′, and the second rising point a ′ and the next falling point b ′ are found. However, the range sandwiched between these two points a'and b'is far from the range corresponding to the required radiation image (corresponding to the mountain B '). When this is converted into a straight line G'and main reading is performed to obtain an image signal, this image signal does not include necessary image information at all, and a visible image is reproduced and output based on this image signal. However, the output image is completely meaningless. In this case, for example, the person who is the subject must be called to the hospital again, and the photographing must be performed again.

Further, in such a case, in order to avoid meaningless reproduction output and re-photographing of a visible image, Japanese Patent Laid-Open No. 1-238648 by the present applicant has taken the following means. Is disclosed.

That is, when the reading condition (straight line G ') obtained as shown in FIG. 5 is compared with the standard reading condition and is too far from the standard reading condition, the minimum of the entire preread image signal Sp. The value S _L ′ is the minimum signal Q during actual reading
min, the maximum value S _M ′ of the whole is the maximum signal Qma during actual reading
In order to obtain x, that is, the line G ″ in FIG. 6 is converted and the main reading is performed to obtain an image signal.
In this way, if the reading conditions are set so that a wide range of stimulated emission light is read in the main reading, it is possible to avoid the extreme situation in which the necessary image information is not obtained at all, but in the end the visible image with poor image quality performance. Often you can only get it.

Regarding the deterioration of the image quality performance, FIG.
Will be described with reference to. Since the reading condition corresponding to the straight line G ′ in FIG. 6 is far from the standard, it is assumed that the reading condition is set so as to correspond to the straight line G ″ so that information of a wide light amount range can be obtained for safety. with such read conditions are established, the image signal obtained from the image information required (corresponding to mountain B ') is in the narrow range sandwiched and Q _1, Q _2, and Qmin that can be used as an image signal Only a part of the range sandwiched by Qmax will be used, and the resolution of the necessary image signal will decrease correspondingly, and as a result, the density resolution of the finally reproduced and output visible image will decrease.
The range between Q ₁ and Q ₂ is Qmax as a whole.
However, if a visible image is reproduced and output as it is, an image with a high overall density will be obtained.

In view of the above circumstances, the applicant of the present invention seeks appropriate reading conditions and the like even when it is determined that the automatically obtained reading conditions and the like are far from standard ones. A radiation image reading device capable of doing so has already been proposed (Japanese Patent Laid-Open No. 2-269333).

This device sets the appropriate sensitivity range of the image to Sk.
_STD ± ΔSk, and an appropriate contrast range of the image is defined by Gp _STD ± ΔGp, and the two defined ranges are stored in the storage means, and the obtained reading condition and / or image processing is performed. It is determined whether or not the condition is within the two ranges stored in the storage means, and if it is determined that the condition is out of the range, a new reading condition and / or image reading condition are replaced in place of the new reading condition and / or image processing condition. And / or is configured to set image processing conditions.

By the way, for example, even when the power of the photographing apparatus is in the OFF state at the time of photographing, it is possible to check using the above-mentioned technique.

However, according to the above-mentioned technique, whether or not an abnormality has occurred is determined by whether or not the reading condition and / or the image processing condition are within a predetermined range. It also includes condition setting mistakes.

Further, according to the above-mentioned technique, the comparison judgment is performed in the two ranges of sensitivity and contrast,
There has been a demand for a method that can be more easily known in the case of the above-mentioned photographing error.

Therefore, the applicant of the present application defines a reference range of the level of the image signal, compares the read image signal with the reference range, and as a result of this comparison, judges that the image signal is outside the reference range. If an error occurs, a warning indicating that an abnormality has occurred is issued, so that it is possible to easily know whether or not the image signal is obtained due to a shooting error or the like without judging whether or not there is a condition setting error by EDR. A radiation image reading method capable of performing the above has been proposed (JP-A-4-324488).

[0029]

SUMMARY OF THE INVENTION
In the method disclosed in the 4-324488 publication, since the reference range of the level of the set image signal is fixed, for example, when a radiographic image is captured at various radiation doses depending on the imaging site, the dose varies. Depending on the dose, the level of the image signal did not fall within the above-mentioned reference range depending on the dose, and although the image signal was obtained by normal imaging, there was an abnormality in the obtained image signal. It was decided that the reading conditions and /
Alternatively, the image processing condition may not be obtained.

In view of the above-mentioned circumstances, the present invention detects a radiation dose or a radiation dose at the time of capturing a radiation image, and detects a radiation dose or a setting error of the reading condition and / or the image processing condition to detect the radiation dose. It is an object of the present invention to provide a radiation image reading method capable of obtaining reading conditions and / or image processing conditions according to the above.

[0031]

According to a first radiation image reading method of the present invention, the stimulable phosphor sheet on which a radiation image including a direct radiation portion directly irradiated with radiation is recorded is irradiated with excitation light. Based on a first image signal representing the radiation image obtained by reading the stimulated emission light emitted from the stimulable phosphor sheet, the stimulable phosphor sheet is irradiated with excitation light again based on the first image signal. Reading conditions for obtaining the second image signal representing the radiation image by reading the stimulated emission light emitted from the body sheet and / or image processing for performing image processing on the obtained second image signal In the radiation image reading method for obtaining the condition, the maximum value Smax0 of the first image signal is obtained, and the predetermined first predetermined width L1 and second predetermined width L2 are respectively subtracted from the maximum value Smax0. Yo , The lower limit value Skmin and the upper limit value Skmax of the reference range of the first image signal are calculated, the reference range of the first image signal between the lower limit value Skmin and the upper limit value Skmax is determined, and the reading is performed. It is judged whether or not the condition and / or the sensitivity center value of the image processing condition exists in the reference range, and the reading condition and / or the image processing is performed only when the sensitivity center value exists in the reference range. The condition is characterized by determining that the condition is normal.

Further, the second radiographic image reading method according to the present invention is based on an image signal representing a radiographic image including a direct radiation portion directly irradiated with radiation, and image processing when performing image processing on the image signal. In the radiation image reading method for obtaining the condition, the maximum value Smax0 of the image signal is obtained, and the predetermined first predetermined width L1 and second predetermined width L2 are respectively subtracted from the maximum value Smax0 to obtain the image The lower limit value Skmin and the upper limit value Skmax of the signal are calculated to obtain the reference range of the image signal between the lower limit value Skmin and the upper limit value Skmax, and the sensitivity center value of the image processing condition exists in the reference range. The image processing condition is determined to be normal only when the sensitivity center value exists in the reference range.

Further, in the radiation image reading method according to the present invention, after it is determined that the reading condition and / or the image processing condition is not normal, the sensitivity center value is further moved between the reference ranges, The reading condition and / or the image processing condition may be obtained based on the moved sensitivity center value, and the reading condition and / or the image processing condition set in advance may be the reading condition and / or the image reading condition. The image processing condition may be set. Further, based on the first image signal or the image signal, the reading condition and / or the image signal may be based on a range from the maximum value Smax0 of the first image signal or the image signal to a value smaller than the maximum value Smax0 by a predetermined value. The image processing condition may be obtained, or a warning that an abnormality has occurred may be issued.

[0034]

In the radiation image reading method according to the present invention, as described above, the maximum value Smax0 of the first image signal is obtained, and the first predetermined width L1 and the second predetermined width which are predetermined with reference to this value are used. The reference range of the first image signal is obtained by subtracting L2 from the maximum value Smax0,
It is determined whether or not the sensitivity center value of the reading condition and / or the image processing condition is within this reference range. As described above, the reference range of the image signal is obtained with the maximum value of the image signal as a reference, so that even when the image is captured at various doses and the level of the image signal varies depending on the region to be imaged. , It is possible to determine whether the center value of the sensitivity of the image signal is within the reference range, depending on the level of the image signal.
It is possible to accurately detect the mistake.

Further, when the sensitivity center value does not exist in the reference range, the sensitivity center value is moved between the reference ranges, or a normal reading condition and / or image processing condition is used. Since the reading condition and / or the image processing condition are obtained, it is possible to sufficiently deal with the case where there is a photographing error or a setting error of the reading condition and / or the image processing condition.

[0036]

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

FIG. 1 is a perspective view showing an example of a radiation image reading apparatus for carrying out the radiation image reading method of the present invention. This example is a system for prefetching using a stimulable phosphor sheet.

The stimulable phosphor sheet 20 on which a radiation image is recorded is pre-read by a pre-reading means 40 for pre-reading by scanning with a weak light beam to release only a part of the radiation energy accumulated on the sheet 20. Is set to. The stimulable phosphor sheet 20 set at this predetermined position is a motor
A sheet conveying unit 42 such as an endless belt driven by 41 conveys (sub-scan) in the direction of arrow Y. On the other hand, a weak light beam 44 emitted from the laser light source 43 is reflected and deflected by a rotary polygon mirror 46 driven by a motor 45 and rotating at a high speed in the arrow direction, and a focusing lens such as an fθ lens.
After passing through 47, the optical path is changed by the mirror 48 to enter the sheet 20, and the main scanning is performed in the arrow X direction substantially perpendicular to the sub-scanning direction (arrow Y direction). From the portion of the sheet 20 irradiated with the excitation light 44, stimulated emission light 49 of a light amount corresponding to the accumulated and recorded radiation image information is emitted, and the stimulated emission light 49 is guided by the light guide 50. , Photomultiplier (photomultiplier tube) 51 for photoelectric detection. The light guide 50 is formed by molding a light guide material such as an acrylic plate, and is arranged so that the linear incident end face 50a extends along the main scanning line on the stimulable phosphor sheet 20. The light receiving surface of the photomultiplier 51 is coupled to the exit end surface 50b formed in an annular shape. The stimulated emission light 49 that has entered the light guide 50 from the incident end face 50a is generated by the light guide 50.
The photomultiplier 51 receives the photomultiplier 51 by emitting the light from the exit end face 50b by repeating total reflection inside the photomultiplier 51, and the photomultiplier 51 converts the photostimulated luminescent light 49 into an electric signal.

The analog output signal S output from the photomultiplier 51 is logarithmically amplified by the logarithmic amplifier 52,
The pre-read image signal Sp is digitized by the A / D converter 53.
Is obtained.

In the above-mentioned pre-reading, the photomultiplier is used so that the radiation energy accumulated in the stimulable phosphor sheet 20 can be read over a wide area.
Reading conditions such as the voltage value applied to the 51 and the amplification factor of the amplifier 52 are defined.

The read-ahead image signal Sp thus obtained is input to the computer system 70. This computer system
Reference numeral 70 denotes a device having a judgment function, which is a feature of the present invention. The main body 72 has a built-in CPU and internal memory, the drive unit 73 into which a floppy disk as an auxiliary memory is inserted and driven, and the operator 80 The computer system 70 includes a keyboard 71 for inputting necessary instructions and the like and a CRT display 74 for displaying reading conditions and other necessary information described later.

On the basis of the pre-read image signal Sp input to the computer system 70, the reading conditions in the main reading described later, that is, the sensitivity Sk and the latitude Gp in the main reading are obtained, and the obtained sensitivities Sk and latitude are obtained. According to Gp, for example photomultiplier 51 '
The voltage value to be applied to, the amplification factor of the logarithmic amplifier 52 ', and the like are controlled.

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

The method of obtaining the reading conditions (sensitivity Sk and latitude L) has already been described with reference to FIG. 5, and therefore the description thereof is omitted here.

The computer system 70 also includes
The first predetermined width L1 and the second predetermined width L2 at the image signal level depending on the imaging region and / or the imaging method.
Is stored in advance.

First, from the pre-read image signal Sp obtained by reading the image recorded on the stimulable phosphor sheet, a histogram is obtained by taking the image signal level on the horizontal axis and the frequency on the vertical axis. FIG. 2 is a diagram showing a histogram obtained from the preread image signal Sp. As shown in FIG. 2, when the histogram 1 is obtained, the maximum value Sma of the histogram 1
x0 is required. Next, the first predetermined width L1 and the second predetermined width L2 are subtracted from the maximum value Smax0 to obtain the lower limit value Skmin and the upper limit value Skm of the reference range of the prefetch image signal Sp.
ax is required. That is, the calculation Skmin = Skmax0-L1 (1) Skmax = Skmax0-L2 (2) is performed.

The first predetermined width L1 and the second predetermined width L2 are preset according to the photographing menu such as the photographing region of the subject and the photographing method, and more specifically, the image. When the recording range of the signal is 4 digits, it is set as shown in Table 1 below.

[0048]

[Table 1]

Here, in Table 1 described above, the latitude is about 2.0 in the general parts (head, neck, chest, front of the pelvis), but in the side of the pelvis and the lumbar spine, X is
The amount of penetrating rays decreases, and the latitude spreads to around 2.5. On the other hand, in the imaging of the extremities, the amount of X-ray transmission increases and the latitude decreases to about 1.5.

When the lower limit value Skmin and the upper limit value Skmax are calculated as described above, the reference range between the lower limit value Skmin and the upper limit value Skmax is obtained. The reference range is indicated by the shaded area in FIG.

When the reference range is obtained in this way, it is determined whether or not the above-described central value Skm of the sensitivity Sk is within the reference range. That is, it is determined whether Skmin≤Skm≤Skmax (3).

If it is determined that the sensitivity center value Skm is within the reference range, it is determined that there is no photographing error, reading condition setting error, or abnormality in the stimulable phosphor sheet, and based on the preread image signal Sp. A signal for controlling the voltage applied to the photomultiplier 51 'of the main reading means 40', which will be described later, the amplification factor of the amplifier 52 ', etc. is output from the computer system 70 according to the read conditions, ie, the sensitivity Sk and the latitude Gp, obtained as described above. To be done.

On the other hand, when it is determined that the sensitivity center value Skm does not exist within the reference range, the computer system 70 sets the sensitivity center value Sk to the lower limit value Skmin and the upper limit value Skm.
The reading condition is set again by the sensitivity based on the sensitivity center value Skm after the movement within the reference range between ax and
The reading conditions control the voltage applied to the photomultiplier 51 'of the main reading means 40' described above.

When the reading conditions are set in this way,
The pre-reading stimulable phosphor sheet 20 'is the main reading means.
The sheet 20 'is set at a predetermined position of 40', and the sheet 20 'is scanned by the light beam 44' which is stronger than the light beam used for the pre-reading, and the image signal _SQ is obtained under the reading condition determined as described above. Since the configuration of the pre-reading means 40 ′ is substantially the same as the configuration of the pre-reading means 40, the components used in the pre-reading means 40 corresponding to the components are marked with a dash. The description is omitted.

The image signal S _Q obtained by being digitized by the A / D converter 53 ′ is sent to the image processing means 54. The image processing means 54 performs appropriate image processing on the image signal S _Q. The image signal subjected to the image processing is sent to the reproducing apparatus 100, and the radiation image based on the image signal is reproduced and displayed.

In the embodiment described with reference to FIG. 2,
Although the pre-reading unit 40 and the main reading unit 40 'are separately configured, the pre-reading unit 40 and the main reading unit 40' have substantially the same configuration as described above, and therefore the pre-reading unit 40 and the main reading unit 40 'are substantially the same. The means 40 'may be integrated and used together. In this case, after performing pre-reading by scanning with a weak light beam, the stimulable phosphor sheet 20 may be backed once, and then this time, scanning with a strong light beam may be performed to perform main reading.

When both the pre-reading means and the main reading means are used, it is necessary to switch the intensity of the light beam between the pre-reading and the main reading. As the switching method, as described above, the laser light source is used. To switch the light intensity itself, to switch the light intensity by inserting and removing an ND filter or the like in the optical path of the light beam, to change the beam diameter of the light beam, to the main scanning speed and the sub-scanning Various known methods such as a method of switching speeds can be used.

The present invention can also be applied to a system that does not perform prefetching. In this case, image processing conditions are required.

FIG. 3 is a diagram showing an embodiment in which the present invention is applied to a system without prefetching.

The analog image signal output from the image reading means 40A configured similarly to the above-mentioned main reading means 40 'is logarithmically amplified by the logarithmic amplifier 91 and digitized by the A / D converter 92, The image signal S _Q ′ is obtained.

Image signal S output from the A / D converter 92
_Q'is the computer system 70 'and the image processing means 54'.
Entered in and. This computer system 70 'is configured almost the same as the computer system 70 in the above-described embodiment (FIG. 2), and the components corresponding to the respective components of the computer system 70 shown in FIG.
The numbers that are the same as the numbers in FIG.

Similar to the system shown in FIG. 2, this system also determines whether or not the sensitivity center value Skm in the obtained image processing conditions is within the above-mentioned reference range, and the sensitivity center value Skm is within the reference range. If the sensitivity center value Skm does not exist in the reference range, the sensitivity center value Skm is moved to the reference range and the sensitivity center after the movement is detected. The final image processing condition is obtained based on the value Skm. The obtained image processing conditions are input to the image processing means 54 ', and the image processing means 54' outputs the image signal S _Q ′ based on the input image processing conditions.
Is subjected to image processing. The image signal subjected to the image processing is sent to the reproducing apparatus 100, and the radiation image based on the image signal is reproduced and displayed.

In the above-described embodiment, when it is determined that the sensitivity center value Skm does not exist within the reference range, the sensitivity center value Skm is moved to the reference range, and based on the reference range after the movement. Reading conditions and /
Alternatively, the reading and / or the image processing is performed using the image processing condition, but the present invention is not limited to this, and when it is determined that the sensitivity center value Skm does not exist within the reference range, The fixed sensitivity Skfix and latitude Gpfix that have been set may be used as the reading condition for the main reading and / or the image processing condition for performing the image processing.

[0064] Also, when the sensitivity center value Skm is determined not to exist within the reference range, the preliminary read-out image signals Sp, the maximum value Smax0 of the read image signal S _Q, a predetermined value smaller value from the maximum value Smax0 Based on the image signal over the range up to
The reading condition and / or the image processing condition may be obtained. This is a method called a maximum value recording method, and when it is determined that the sensitivity center value Skm does not exist within the reference range, the pre-read image signal Sp or the main read image signal S as shown in FIG. The histogram 2 of _Q is obtained, and the image signal value S smaller than the maximum value Smax0 of this histogram 2 by a predetermined value
In this method, m1 is determined, and the reading condition and / or the image processing condition is obtained based on the image signal in the range between the image signal value Sm1 and the maximum value Smax0. Since the details of the maximum value recording method are disclosed in Japanese Patent Laid-Open No. 60-185944, detailed description thereof will be omitted here.

Further, when it is determined that the sensitivity center value Skm does not exist within the reference range, a predetermined alarm sound is emitted from the above-mentioned computer system or an indication that an abnormality has occurred on the CRT is displayed. May be.

In this case, the operator discontinues the subsequent calculation using the EDR by an alarm sound or a display, and also checks the photographing section, the stimulable phosphor sheet, etc.,
The EDR will be calculated again.

In the above-described embodiment, the histogram of the image signal is obtained and it is determined whether the sensitivity center value Skm is within the reference range based on this histogram. It is not necessary to perform the determination by using the image signal, and the determination may be performed by directly using the image signal.

In the radiation image reading method according to the present invention, if the above-mentioned pre-reading is not performed, the radiation image is read from the recording sheet on which the radiation image is recorded to obtain an image signal, and the image signal is subjected to image processing. It can be applied to general radiation image reading devices.

[0069]

As described above in detail, in the radiation image reading method according to the present invention, the relative reference range corresponding to the magnitude of the image signal is set by the predetermined width which is set in advance. Regardless of the amount of radiation applied to a subject, it is possible to accurately detect an abnormality during shooting or a setting error in the reading condition and / or the image processing condition, and to read the condition and / or the image processing according to the image signal. Conditions can be set.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a radiation image reading apparatus for carrying out a radiation image reading method according to the present invention.

FIG. 2 is a diagram showing a histogram created in an apparatus for carrying out a radiation image reading method according to the present invention.

FIG. 3 is a perspective view showing another example of a radiation image reading apparatus for carrying out the radiation image reading method according to the present invention.

FIG. 4 is a diagram showing a histogram for explaining a maximum value recording method.

FIG. 5 is a diagram showing a histogram of a preread image signal.

FIG. 6 is another diagram showing a histogram of a preread image signal.

[Explanation of symbols]

 1, 2 Histogram 20 Accumulative phosphor sheet 40 Pre-reading means 40 'Main reading means 49,49' Photostimulated emission light 51,51 'Photomultiplier 52,52', 91 Logarithmic amplifier 53,53 ', 92 A / D converter 70,70 'Computer system 71,71' Keyboard 72,72 'Main body 73,73' Drive section 74,74 'CRT display 80 Operator 100 Playback device

Claims (10)

[Claims] 1. A stimulable luminescent light emitted from a stimulable phosphor sheet is read by irradiating a stimulable phosphor sheet, on which a radiation image including a direct radiation portion directly irradiated with radiation is recorded, with excitation light. The radiation image is obtained by irradiating the stimulable phosphor sheet again with excitation light based on the obtained first image signal representing the radiation image and reading the stimulated emission light emitted from the stimulable phosphor sheet. Conditions for obtaining the second image signal representing the image and / or the obtained second image signal.
In the radiation image reading method for obtaining the image processing condition when performing the image processing on the image signal, the maximum value Smax0 of the first image signal is obtained, and the predetermined first predetermined width L1 and the predetermined predetermined width L1 are obtained from the maximum value Smax0. By subtracting each of the second predetermined widths L2,
The lower limit value Skmin and the upper limit value Skmax of the reference range of the first image signal are calculated to obtain the reference range of the first image signal between the lower limit value Skmin and the upper limit value Skmax, and the reading condition And / or it is determined whether or not the sensitivity center value of the image processing condition exists in the reference range, and only when the sensitivity center value exists in the reference range, the reading condition and / or the image processing condition Is a normal radiation image reading method. 2. After the read condition and / or the image processing condition is not determined to be normal, the sensitivity center value is further moved between the reference ranges, and based on the moved sensitivity center value. The radiographic image reading method according to claim 1, wherein the reading condition and / or the image processing condition are obtained by the above. 3. The reading condition and / or the image processing condition is not determined to be normal, and the reading condition and / or the image processing condition set in advance are further set to the reading condition and / or the image processing condition. The radiation image reading method according to claim 1, wherein: 4. From the maximum value Smax0 of the first image signal to a value smaller than the maximum value Smax0 by a predetermined value after the reading condition and / or the image processing condition is not determined to be normal. The radiographic image reading method according to claim 1, wherein the reading condition and / or the image processing condition is obtained based on the first image signal over a range. 5. A warning that an abnormality has occurred is issued after the reading condition and / or the image processing condition is not determined to be normal.
The radiographic image reading method described. 6. A radiation image reading method for obtaining an image processing condition when performing image processing on the image signal based on an image signal representing a radiation image including a direct radiation portion directly irradiated with radiation, wherein the image signal By obtaining the maximum value Smax0 of the above, and subtracting the predetermined first predetermined width L1 and second predetermined width L2 from the maximum value Smax0, respectively.
The lower limit value Skmin and the upper limit value Skmax of the image signal are calculated to obtain a reference range of the image signal between the lower limit value Skmin and the upper limit value Skmax, and the sensitivity center value of the image processing condition is the reference range. The radiation image reading method is characterized in that the image processing condition is determined to be normal only when the sensitivity center value exists in the reference range. 7. After the image processing condition is not determined to be normal, the sensitivity center value is further moved between the reference ranges, and the image processing condition is changed based on the moved sensitivity center value. The radiation image reading method according to claim 6, which is obtained. 8. The radiation image reading method according to claim 6, wherein after the image processing condition is not determined to be normal, a preset image processing condition is set as the image processing condition. 9. After determining that the image processing condition is not normal, further based on the image signal ranging from the maximum value Smax0 of the image signal to a value smaller than the maximum value Smax0 by a predetermined value. The radiographic image reading method according to claim 6, wherein the image processing condition is obtained. 10. The radiographic image reading method according to claim 6, further comprising issuing a warning indicating that an abnormality has occurred after determining that the image processing condition is not normal.