JPS63133761A - Irradiation field recognizing method and image processing condition deciding method - Google Patents

Abstract

PURPOSE:To decide a space sandwiched with a differential value over +Th and a differential value less than -Th as an irradiation field. by finding a difference between adjacent picture data from read picture information, and comparing the differential picture with a prescribed threshold value Th. CONSTITUTION:The picture information accumulated and recorded on a cumulative phosphor sheet 10 by pre-reading from the sheet 10 is read. At this time, when photography is performed by applying rectangular irradiation field diaphragm, the levels of picture data in the irradiation field 12 and the irradiation field 14 are different, therefore, pulsewise signals at a part where it changes from out of the irradiation field to the irradiation field, and a part where it changes from the irradiation field to the out of the irradiation field as shown in figure can be obtained. Therefore, the prescribed threshold value Th is set, and by comparing the differential picture data with the threshold value Th, the differential value over the +Th (point where it changes from the out of the irradiation field to the irradiation field), and the differential value less than the -Th (point where it changes from the irradiation field to the out of the irradiation field) are decided, and the part sandwiched with those tow points is decided as the irradiation field in a direction of an X-axis.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention recognizes the irradiation field when radiation image information is recorded on a recording medium such as a stimulable phosphor sheet by aperture irradiation field. The present invention relates to a method and a method of determining image processing conditions when processing image information read from the recording medium, using the irradiation field recognition method. (Prior art) When a certain type of phosphor is irradiated with one ray (X-ray, α-ray, β-ray, γ-ray, electron beam, ultraviolet light, etc.), part of this radiation energy is absorbed into the phosphor. It is known that when this phosphor is irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy. called phosphor. Using this stimulable phosphor, radiation image information of a subject such as a human body is recorded on a -H sheet of stimulable phosphor, and then the stimulable phosphor sheet is scanned with excitation light such as a laser beam. generates stimulated luminescence light, photoelectrically reads this stimulated luminescence light to obtain an image signal, performs image processing on this image signal, and creates a radiation image of the subject based on the image signal subjected to image processing. The present applicant has already proposed a radiation image information recording and reproducing system that outputs a visible image to a recording material such as a photographic light-sensitive material and a display device such as a CRT. (JP-A-55-12429, JP-A-56-11395, etc.) In addition, in the above system, in order to improve the suitability for observing and interpreting visible images, when reading the stimulated luminescence light photoelectrically, the individual It is desirable to perform the reading based on optimal reading conditions determined according to the shadow image, and from this point of view, as one aspect of the above system, a stimulable phosphor in which radiation image information of the subject is stored and recorded is used. Prior to "main reading", the sheet is scanned with excitation light and the stimulated luminescence light emitted from the sheet is read by a photoelectric reading means to obtain an electrical image signal for reproducing a diagnostic visible image. , "Pre-reading" is performed in advance by scanning the sheet with excitation light at a lower level than the excitation light used for this main reading and reading the outline of the image information accumulated and recorded on this sheet, and the image information obtained by this pre-reading is performed. The reading conditions for performing the actual reading of the ship's log are determined based on the reading conditions, the actual reading is performed according to these reading conditions, the image signal obtained from this actual reading is input to the image processing means, and the image processing means determines the area to be imaged and the area to be imaged. There are known systems that process image signals to obtain output images suitable for diagnostic purposes depending on the method, etc., and reproduce these image signals as visible output images on photographic light-sensitive materials. This is disclosed in Japanese Patent Laid-Open No. 58-67240, which was filed earlier and has already been published. The reading conditions here refer to the relationship between the input and output of the reading means, for example, in the above case, the input (light amount of stimulated luminescence light) and output (electrical image signal level) of the photoelectric reading means.
It is a general term for various conditions that affect the relationship between
This refers to the scale factor (latitude) or the power of excitation light during reading. In addition, the fact that the excitation light used for pre-reading is at a lower level than the excitation light used for main reading means that the effective energy of the excitation light that the stimulable phosphor sheet receives per unit area during pre-reading is equal to that during main reading. means smaller than. In this way, by grasping the outline of the image information stored on the sheet before the actual reading and performing the actual reading according to the reading conditions determined based on the outline of this image information, it is possible to It is possible to eliminate inconveniences caused by fluctuations in the range of radiation energy levels accumulated and recorded on the sheet due to fluctuations in radiation exposure, etc., and to always obtain visible images with excellent suitability for observation and interpretation. (Problems to be Solved by the Invention) However, in the above system, it is necessary to prevent radiation from being irradiated to areas that are not necessary for human diagnosis, or to prevent radiation from being applied to areas that are unnecessary for diagnosis. Scattered rays enter areas necessary for diagnosis, reducing contrast resolution, so to prevent this, the M-ray irradiation field may be narrowed down when recording radiation image information (when in the shadow). When imaging is performed with the irradiation field narrowed down to For example, it would be convenient to know where the irradiation field contour line is. This is because, for example, the above-mentioned stimulable phosphor sheet can be read in advance, and based on the image information obtained by this pre-reading, the actual reading can be performed. This is because when trying to determine the conditions, when the irradiation field is narrowed down, it is preferable to determine the reading conditions based only on the pre-read image information within the irradiation field range from Sea 1 to above. A detailed explanation is as follows.That is, as a specific method for determining the reading conditions for main reading based on the image information obtained by the pre-reading,
For example, a histogram of the image information (image signal level) obtained by pre-reading is obtained, and from this histogram, the maximum image signal level PmaX and the minimum image signal level Pm1 of the desired image information range in this histogram are calculated.
n is calculated, and Pmax and Pm1n are the maximum density □ max of the appropriate density range in the visible output image, respectively.
and the maximum signal level Q m of the desired input signal range in the image processing means determined by the minimum density [) min
The present applicant has filed an application for a method of determining reading conditions for main reading so as to correspond to ax and minimum signal level Qmin (Japanese Patent Application Laid-open No. 156055/1983).
When imaging is performed by narrowing down the radiation irradiation field as described above, the scattered radiation generated from the subject in the irradiation field usually enters the irradiation field on the stimulable phosphor sheet, and the highly sensitive stimulable phosphor sheet Since the sheet also accumulates and records these scattered rays, the image information (image signal level) obtained by pre-reading
The histogram will also include the image signal level based on this scattered ray. Since the image signal level outside the irradiation field on the sheet based on this scattered radiation may be higher than the image signal level within the irradiation field, it is necessary to distinguish between the image signal levels inside and outside the irradiation field from the obtained histogram. It is difficult. Therefore, when calculating Pmax and Pm1n from the histogram and determining the reading conditions from the histogram as described above, the minimum value of the image signal level within the irradiation field should be pmin, but the image signal level due to scattered radiation outside the irradiation field is The minimum value is Pm1n
There may be cases where this is the case. In this way, when the minimum value of the image signal level outside the irradiation field is set to pmin, that value is generally lower than the minimum value of the image signal level within the irradiation field. Therefore, the density of the image in the area necessary for diagnosis becomes too high, and as a result, the contrast decreases, making it difficult to make a satisfactory diagnosis. In other words, when shooting with a narrowed irradiation field, scattered rays generated from the subject will enter the irradiated field above the sheet, and the pre-read image information will include information based on these scattered rays. Even if reading conditions are determined based on such pre-read image information, it is difficult to determine the optimal reading conditions, and as a result, visible images with excellent observation and interpretation aptitude @
It becomes difficult to do so. Therefore, when trying to determine the reading conditions based on the pre-read image information using the above method, if the irradiation field is being photographed with the irradiation field aperture, the irradiation field is accurately recognized and the pre-read image information within the irradiation field is used. It is desirable to determine it based on the above and eliminate the adverse effects caused by the scattered radiation outside the irradiation field. The above is an explanation of the necessity of irradiation field recognition when determining the reading conditions for imaging using a stimulable phosphor sheet. This may become necessary due to various circumstances when radiation image information is recorded using field aperture. How to use: In the above system, image processing is performed on the read image signal as described above. This image processing is generally performed on each individual image based on image processing conditions determined based on the area to be imaged and the imaging method so that an output image suitable for the diagnostic purpose can be obtained. For example, it is conceivable to make a decision based on the image information obtained by the above-mentioned pre-reading or actual reading, rather than the above-mentioned imaging site/shading method, or based on both of that image information and the above-mentioned imaging site/imaging method. However, when imaging is performed with the irradiation field apertured, even if the image processing conditions are determined based on the pre-read or main-read image information, as mentioned above, the image information contains scattered radiation outside the irradiation field. information (noise) is included, so it is difficult to obtain image processing conditions that are as favorable as one might expect if they were initially determined based on the image information. When determining the image processing conditions based on the irradiation field aperture, the decision is made simply based on the read image information itself. It is desirable to make a decision based on little image information.The problem in determining such image processing conditions is not limited to the case of imaging using the stimulable phosphor sheet mentioned above, but also generally when the recording medium has an irradiation field aperture. This may occur when radiation image information is recorded over a period of time.The above-mentioned image processing conditions are a general term for various conditions that affect the relationship between input and output in the image processing means. means, for example, gradation processing conditions, spatial frequency processing conditions, etc. In view of the above-mentioned circumstances, the first object of the present invention is to apply a rectangular irradiation field to a recording medium such as a stimulable phosphor sheet to It is an object of the present invention to provide a method for recognizing an irradiation field when image information is recorded.A second object of the present invention is to provide a method for recognizing an irradiation field when image information is recorded. The object of the present invention is to provide a method for determining image processing conditions based on image information with less noise, excluding scattered radiation information in the irradiation field, when radiation image information is recorded with irradiation field aperture. (Problem In order to achieve the above object, the irradiation field recognition method according to the first aspect of the present invention uses a stimulable phosphor sheet or the like on which radiation image information is photographed with the irradiation field apertured. Reading image information from a recording medium, determining image data at each position on the recording medium from the read image information, and calculating differences between the image data, for example, differences between adjacent image data, from this image data. Processing is performed to create a difference image consisting of difference values, a predetermined threshold value Th is prepared, and predetermined processing is performed on the difference image or the difference image.
11 Scan the difference image in one direction to detect a predetermined section sandwiched between a difference value of +Th or more and a difference value of -Th or less on each scanning line, and calculate the sum of the predetermined sections on each scanning line. is characterized by recognizing it as an irradiation field. In order to achieve the above object, the method for determining image processing conditions according to the second aspect of the present invention collects image information from a recording medium such as a stimulable phosphor sheet on which radiation image information has been captured by applying irradiation field aperture. The image data at each position on the recording medium is obtained from the read image information, and this image data is subjected to difference processing to obtain the difference between the image data, for example, the difference between adjacent image data, and from the difference value. A difference image is created, a predetermined threshold value Th is prepared, and the difference image or a processed difference image obtained by performing a predetermined process on the difference image is scanned in one direction to obtain a value of +Th or more on each scanning line. A predetermined section sandwiched between the difference value and the difference value less than or equal to -Th is detected, the sum of the predetermined sections on each scanning line is recognized as the irradiation field, and the recognized section is detected from among the image information read from the recording medium. The image processing condition is determined based on image information within the irradiation field. Note that the term "recording medium" as used above refers to a medium capable of recording radiographic image information, and a specific example thereof includes the above-mentioned stimulable phosphor sheet, but is not necessarily limited thereto. In addition, the image information J read from a recording medium in the above refers to the image information recorded on the recording medium that is read by some method, for example, by pre-reading or main reading on the stimulable phosphor sheet mentioned above. It refers to the obtained image information, but is not necessarily limited thereto. Of course, the method of using the irradiation field recognized by the above method is not limited to any particular method. Furthermore, in the image processing condition determining method described above, it does not matter whether the image information for recognizing the irradiation field and the image information for determining the image processing conditions are the same. For example, the irradiation field may be recognized from the main reading image information and the image 4 & processing conditions may be determined based on the main reading image information within that irradiation field, or the irradiation field may be recognized from the pre-read image information and the pre-reading or main reading within that irradiation field may be determined. Image processing conditions may be determined based on image information. Furthermore, the above-mentioned "determining image processing conditions based on image information within the irradiation field" refers to cases in which the image processing conditions are determined based only on such image information, as well as cases in which such image information and information are combined, such as those described above. This meaning also includes cases where the decision is made based on the part to be photographed, the method of photographing, etc. Further, the above-mentioned image processing conditions may be determined in any manner as long as it is based on image information within the irradiation field, that is, by using the image information, and the specific method is not limited in any way. . Generally speaking, the image processing conditions to be determined are typically gradation processing conditions, but are not necessarily limited thereto. (Effects of the Invention) As described above, in the irradiation field recognition method according to the first invention, a difference image is created by performing differential processing on image data at each position on a recording medium, and the difference image is scanned in one direction. detecting a predetermined section sandwiched between a difference value of a predetermined threshold value +T11 or more and a difference value of -Th or less on each scanning line;
The sum total of each predetermined section is recognized as the irradiation field. Since the image data at each position on the recording medium corresponds to the magnitude of the energy of the radiation incident on the recording medium,
Image data in the field outside the irradiation field will generally be at a low doji level, and image data within the irradiation field will generally be at a high quantum level. Therefore, the difference value between the image data in the part where the irradiation field contour is located is much larger or smaller than the difference value in the part where the irradiation field contour is located, and the positions where this difference value is extremely large and extremely small are appropriately set. By performing detection using the threshold value Th, it is possible to detect the position of the irradiation field contour and, furthermore, the irradiation field section sandwiched at the same position. That is, the predetermined section on each scanning line in the present invention is an irradiation field section on each scanning line,
Therefore, according to the present invention, which recognizes the sum of such predetermined sections on each scanning line as the irradiation field, it is possible to accurately recognize the irradiation field. As described above, the method for determining image processing conditions according to the second invention recognizes an irradiation field by the irradiation field recognition method according to the first invention, and performs image processing based on image information within the recognized irradiation field. It determines the conditions. If you find the irradiation field and extract only the image information within that irradiation field, the extracted image information will be the image information read from the entire recording medium excluding the image information due to scattered radiation outside the irradiation field. It can be said that it is true image information that does not include line noise. Therefore, according to the present invention, image processing conditions can be determined based on true image information that does not include such scattered radiation noise, and as a result, more appropriate image processing conditions can be determined. I can do it. (Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, an embodiment of the irradiation field recognition method according to the first invention will be described. In the embodiment described below, as shown in FIG. The present invention is applied to the rectangular irradiation field 12.The X-axis and Y-axis in FIG. In this case, the field aperture is applied so that each side of the rectangular irradiation field outline is parallel to each side of the sheet 10, so the xm and Y axes are set along two adjacent sides of the sheet 10. In this embodiment, first, the image information stored and recorded on the stimulable phosphor sheet 10 shown in FIG. 1 is read by performing the above-described pre-reading. Reading image information from the stimulable phosphor C!~10 by pre-reading means reading the stimulated luminescence light emitted from the sheet 10 by scanning the sheet 10 with the pre-read excitation light, and reading the stimulated luminescence light emitted from the sheet 10 with a photoelectric conversion means. This means obtaining information consisting of electrical signals corresponding to the amount of stimulated luminescence light for each scanning point (that is, each pixel). Next, digital image data at each position on the sheet is obtained from the image information read as described above. In order to obtain this digital image data, it may be obtained directly from the above-mentioned pre-reading (thus, the image information read), or it may be obtained by subjecting the image information to pre-processing such as spatial filter processing. To obtain this, for example, the position on the sheet may be set in pixel units, and the pre-read image information of the pixels corresponding to each position may be digitized and used as digital image data at that position. Spatial filter processing, etc. When calculating by pre-processing,
For example, a plurality of pixels in a certain relationship are set together as one position, and based on the pre-read image information of the pixels included in this position, for example, they are averaged to calculate the digital image data of the position. Alternatively, the position on the sheet may be set in units of pixels, and the digital image data at the position may be calculated based on pre-read image information of a plurality of pixels corresponding to the position and surrounding positions. . In this embodiment, positions on the sheet are set pixel by pixel, and pre-read image information of pixels corresponding to each position is digitized as digital image data at that position. Figure 2 is an enlarged view of part A of the stimulable phosphor sheet in Figure 1. Each square in the figure represents one pixel (position), and the f (1,
1>, f (1, 2>, ...... is each pixel (1,
1>, (1, 2>, ...) The above image information is digitized. After obtaining the digital image data at each position as described above, next, the difference is added to the image data. Processing is performed to create a difference image consisting of difference values.The above-mentioned difference processing is performed at a predetermined position based on the difference between digital image data in a predetermined relationship, such as adjacent or nearby digital image data. It refers to the process of finding the difference value of
This refers to the process of determining a difference value using a difference operator as shown in > to (f). The difference processing using the operator shown in FIG. 3(a) subtracts the digital image data at adjacent positions in the X-axis direction and uses the result as a difference value. For example, in FIG. 4> digital image data f (
3, 4> to position (3, 3> digital image data f
(3, 3> is subtracted and the result is used as the difference value of the position (3, 3>). In addition, the difference processing using the operator shown in FIG. For example, in FIG. 2, the digital image data at positions on both sides of the direction are subtracted and the result is used as the difference value for the predetermined position.
Digital image data f (3,4> to @(3,
The digital image data f (3, 2) in 2) is subtracted and the result is used as the difference value at the position (3, 3>).The difference processing using the operator shown in Figure 3(C) is as follows:
The digital image data at adjacent positions in the Y-axis direction are subtracted and the result is used as the difference value. For example, in FIG. 2, the digital image data at position @(4,3>
, 3> to the digital image data f at position (3, 3)
(3, 3> is subtracted and the result is used as the difference value of the position (3, 3>). Difference processing using the operator shown in Figure 3(d) is performed on both sides of a predetermined position in the Y direction. For example, in FIG. 2, digital image data f(4,3> at position (4,3>) is subtracted from the digital image data at positions f(4,3> to , 3> is subtracted from the digital image data f (2, 3>) and the result is used as the difference value at the position (3°3).The difference processing using the operator shown in Fig. 3(e) is , is a process that is performed by simultaneously using the operator in FIG. 3 (a >) and the operator in FIG. 3 (C). For example, in FIG.
, 4> to position (3, 3> digital image data f
Add the result of subtracting (3,3>) and the result of subtracting the digital image data f (3°3) of position (4,3) from the digital image data f (4,3>) of position (4,3). The combined value is the difference value at the position (3, 3>).The difference processing using the operator shown in Figure 3(f) is as follows:
This process is performed by simultaneously using the operator in FIG. 3(b) and the operator in FIG. 3(d). For example, in FIG. 2, the digital image data f (3, 4) at position (3, 4)
, 4> to place @ (3, 2> digital image data f
Add the result of subtracting (3,2>) and the result of subtracting the digital image data f (2゜3) of position (2,3>) from the digital image data f (4,3) of position (4,3>). The sum is the difference value for the position (3, 3>).The above difference value may be obtained for all of the above positions, or it may be obtained for some appropriately selected positions. Good. In this embodiment, the operator shown in FIG. 3(a) is used to find the difference values at all the positions, and a difference image is created from the difference values. The difference image created as described above or the processed difference image obtained by performing appropriate processing on the difference image is scanned in one direction to determine the difference values of +Hh or more and -Th or less on each scanning line. A predetermined section sandwiched between the difference values is detected. In this embodiment, a method is adopted in which the predetermined section is detected using the above-mentioned processed difference image. That is, in this embodiment, the above-mentioned The difference values thus obtained are subjected to threshold processing using the predetermined threshold Th, and the difference values greater than +Th are +1, the difference values less than -1 are -1, and the other differences are The value, that is, the difference value smaller than +Th<-Th is encoded as O,
The threshold-processed difference image consisting of the threshold-processed difference values encoded in this way is scanned in the X-axis direction, and if a combination of +1 and -1 is found on each scanning line, the +1
The section between and -1 is detected as a predetermined section on the scanning line. Figure 4 shows the digital image data on the arbitrary line 9JX in the X-axis direction in Figure 1, and Figure 5 shows the difference between the digital image data in Figure 4 and the difference operator shown in Figure 3 (a). A diagram showing the difference value obtained by the processing and how the difference value is subjected to the ternarization threshold processing as described above. FIG. 6 shows such threshold processing performed on all lines in the X-axis direction. , and is a diagram showing a threshold-processed difference image consisting of threshold-processed difference values (-1° 0, +1) that are multiplied by 1q as a result. However, in Fig. 6, the threshold-processed difference values +1 and -1 are simply displayed as e and e, and the parts where neither e nor e are displayed are the parts where the threshold-processed difference value is O. It is. Since the digital image data at each position on the stimulable phosphor sheet corresponds to the energy amplitude of the radiation incident on the sheet, the image data of the field irradiation area 14 generally has a low quantum level, as shown in FIG. Therefore, the irradiation field 12
The image data within is generally at a high quantum level. Therefore, as shown in Figure 5, the difference value between the image data in the part where the irradiation field contour is located is much larger or smaller than the difference value in other parts, and the difference value is extremely large or very small. Threshold value Th with the position set appropriately
(It is possible to detect the position of the irradiation field contour, and furthermore, the irradiation field section sandwiched by the open position.) Therefore, by scanning the above-mentioned difference image in the X-axis direction, as shown in FIG. As shown in each scanning line LX!, LXz, LX:
l,...LX: . ......Detecting a predetermined section (shaded area in the figure) between a position where the difference value on LXn is ±Th or more and a position where it is less than -Th means that the difference value on each scanning line is detected. This means detecting the irradiation field section. In addition, in FIG. 6, scanning lines LX+ and LXz
Since it is located in the outside irradiation area 14, naturally there is no difference value greater than +1'-h or less than -Th on this line. Furthermore, even if the line is located on the irradiation field 12, like the line LXi in the figure, in some cases there may not be a combination of a position where the difference value is +Th or more and a position where the difference value is -Th or less. In this case, it is treated as if the predetermined section was not detected from that scanning line. Even when the same threshold processing as above is performed using the difference operator shown in FIG. 3(b), a difference image similar to that of the present example shown in FIG. The predetermined section can be detected by scanning this differential image in the same way as in the case of . When the difference operator shown in FIG. 3(c)ld) is used, a difference image as shown in FIG. (the section indicated by the double-headed arrow in the figure) may be detected. When using the difference operators shown in Fig. 3(e) and (f), a difference image as shown in Fig. 8 is obtained, and in this case, scanning is performed in one direction, either the X-axis direction or the Y-axis direction. Then, a predetermined section in each scanning line can be detected (in the figure, a double-headed arrow is shown indicating a predetermined section detected by scanning in the X-axis direction). In short, the above embodiment performs threshold processing on the difference image to encode all of the difference values so that it is possible to distinguish between the difference values greater than or equal to Th, the difference values less than or equal to -Th, and the difference values in the fraction thereof. , the thresholded difference value (+
1.0. -1> to detect a predetermined section by scanning a threshold-processed difference image consisting of Threshold processing is performed to encode only a part of the difference value, such as so-called half-threshold processing, in which the difference value is left as is, and the threshold processing is performed using the threshold-processed difference value obtained by this processing. The predetermined section may be detected by scanning the completed differential image. FIG. 9 is a threshold-processed difference image created by the same method as the embodiment shown in FIG. 3, and is a diagram showing a case where the irradiation field is circular. As can be easily understood from this figure,
The method according to the invention can also be applied to cases where the irradiation field is not rectangular. In addition, even in the case of so-called split shooting, in which one sheet is divided and each section is shot separately,
For example, it is also possible to apply the present invention to each division by obtaining information in advance that divisional imaging can be performed. In the method according to the present invention, the difference image is scanned in one direction to detect a predetermined section, but the scanning direction is not necessarily arbitrary, and as understood from the above embodiments, it depends on how the difference value is calculated. It will be decided accordingly. Further, the concept of a difference value and a difference process in the method according to the present invention also includes the concept of a differential value and a differential process, which are substantially the same as the above. The irradiation field recognized as described above can be used for various purposes. For example, it can of course be used to extract only the image information within the irradiation field from the pre-read image information as mentioned above and determine the reading conditions based on that, but it can also be used to extract only the image information within the irradiation field from the main reading image information as described below. In addition to extracting only the image information of the area and determining image processing conditions based on it, it can also be used to extract only the image information within the irradiation field from the pre-read image information and determining image processing conditions based on it. and for further purposes,
For example, the irradiation field is recognized from the pre-read image information, and when reading the actual image, it is possible to
As disclosed in No. 346, it can also be used to limit the reading area within the irradiation field. By thus limiting the reading area for the main reading within the irradiation field, noise components due to scattered radiation recorded outside the irradiation field of the stimulable phosphor sheet are not read, and an excellent final image can be obtained. Furthermore, by narrowing down the reading area, it is possible to shorten the reading time or increase the reading density. Of course, the recognition of the irradiation field in the present invention is not limited to the pre-read image information as in the above embodiments, but can also be performed based on other image information, for example, main-read image information. Next, an embodiment of the image processing condition determining method according to the second invention will be described. In the example described below, the irradiation field is recognized from the actual reading image information in a stimulable phosphor sheet that has been patterned by performing irradiation field aperture, and the image processing conditions are set based on the actual reading image information within the recognized irradiation field. The present invention is applied to determining one of the 'f@ tone processing conditions. In this embodiment, first, the above-mentioned stimulable phosphor sheets 1 to 1 are read to obtain image information. Obtaining image information by actual reading refers to scanning a stimulable phosphor sheet with pre-read excitation light and reading the stimulated luminescence light emitted from the sheet by the scanning with a photoelectric reading means. The obtained image information is information consisting of electrical signals corresponding to the amount of stimulated luminescence light for each scanning point, that is, each pixel, on the sheet. Next, digital image data at each position on the sheet is obtained from the image information obtained in this way, and a difference process is performed on this digital image data to obtain a difference between the image data, resulting in a difference image consisting of the difference values. , prepare a predetermined threshold Th, and scan the difference image or a processed difference image obtained by performing a predetermined process on the difference image in one direction to obtain a difference value of +Th or more on each scanning line. -T
A predetermined section sandwiched by a difference value of h or less is detected, and the sum of the predetermined sections on each scanning line is recognized as the irradiation field. Since this irradiation field recognition method is the same as the irradiation field recognition method of the first aspect of the present invention described above, a detailed detailed explanation thereof will be omitted. Next, gradation processing conditions are determined based on the image information within the recognized irradiation field among the main reading image information read from the Bts body. Any method may be used for this determination; for example, the following method may be used. In this method, a histogram of main reading image information (image signal level) within the irradiation field is obtained, and from this histogram, a maximum image signal level P max and a minimum image signal level p min of a desired image signal range to be added to this histogram are obtained, These Pmax and pmin are the maximum density D in the appropriate density range in the visible output image, respectively.
Maximum signal level R of the desired input signal range in the image reproduction means determined by max and minimum density Dmin
The gradation processing conditions are determined to correspond to the maximum signal level Rmin and the minimum signal level Rmin. This method will be described in detail below with reference to FIG. In addition, in FIG. 10, the histogram of the stimulated luminescent light before being read photoelectrically is not the histogram of the electrical image signal obtained by photoelectrically reading the stimulated luminescent light by the photoelectric reading means. However, since this stimulated luminescence light is converted into an electrical image signal according to the fixed and linear reading conditions shown in the figure, the stimulated luminescence light amount and image signal level are fixed. Therefore, the histogram of the stimulated luminescent light is substantially the same as the histogram of the image signal. Therefore, in the following explanation, the first
The explanation will be given by regarding the stimulated luminescence light histogram in FIG. 0 as an image signal histogram. In addition, the image information used for creating the histogram in this example is not necessarily limited to that read based on the linear reading conditions as described above, but in short, the image information used to create the histogram is not necessarily limited to that read based on the linear reading conditions as described above. For example, it may be image information read under non-linear reading conditions. First, the hiss of the reading image information (image signal) within the irradiation field]
・Determine Durham and determine the range of the desired image signal (range of stimulated luminescence light amount) from this histogram. The desired image signal range is determined from the histogram by referring to the shadow region and imaging method, since the histogram pattern varies to some extent depending on the shadow region and the imaging method. For example, the histogram for a chest eruption has a pattern like this in Figure 10, where J is the mediastinum, K is the heart, L is the lung field, M is the skin and soft tissue, and N is the outside of the subject. From this histogram, we can determine the maximum image signal level Pmax within the range of the desired image signal.
(the maximum amount of stimulated light emission 3max) and the minimum image signal level pmin (the minimum amount of stimulated light emission Sm1n) can be determined. For example, in the case of FIG. 10, if information on the skin and soft parts M and the outside of the subject N is unnecessary, then the image signal range J and KSL as shown in the figure is assumed to be unnecessary.
The range is from max to Pm1n. This p max
As a method for determining Pm1n and Pm1n, for example, certain threshold values Tr and T2 are determined depending on the desired image signal range, and
A possible method is to obtain Tt and T2, but any other method may be used to obtain it from the histogram. On the other hand, in a radiation image information recording and reproducing system, as mentioned above, an electrical image signal is usually obtained from stimulated luminescence light by a photoelectric reading means, and various signal processing, especially gradation processing, is performed on this signal by an image processing means. This signal is reproduced and recorded as a visible output image on a photographic material or the like by an image reproduction means. In this output image, there is a density range suitable for observation and interpretation, and generally this appropriate density range ([)max
~Dmin) is predetermined, and the reproduction conditions for the image reproduction means (conditions that determine the relationship between the input to the reproduction means and the output from the reproduction means) are also predetermined. 'Eclipse range (DIIlax~[
) min ) to the image reproducing means is uniquely determined according to the image reproducing conditions. Therefore, p max and p min obtained as above
is R max and Ri+i determined as above
The gradation processing conditions in the gradation processing are determined so as to correspond to n. Gradation processing is a process in which each image signal input to an image processing means (gradation processing means) is output after converting its level according to certain conditions, and these certain conditions are called gradation processing conditions. , usually represented by a nonlinear tone curve. The purpose of such gradation processing is to produce a preferable visible output image suitable for diagnostic purposes in accordance with contrast regions such as the head and chest, and the imaging method and shape conditions, such as simple and contrast-enhanced imaging. Therefore, in general, a basic form of nonlinear gradation processing conditions having the most preferable pattern for each patterning condition is determined in advance, and when gradation processing of each image is performed, the basic form of the nonlinear gradation processing condition is determined in advance. It is preferable to select an appropriate basic form of gradation processing conditions according to the projection conditions, and perform gradation processing using that basic form. In this embodiment as well, image 1! An appropriate one is selected from among the basic shapes of the gradation α conditions predetermined according to the imaging conditions of As shown in the second quadrant of the figure, by shifting it up and down or rotating it around a predetermined center point O, Pmax
, Pm1n, etc. correspond to Rmax, Rmin, and the gradation processing conditions to be used for positioning are determined. Note that the gradation processing conditions are not limited to the non-linear ones determined by the projection conditions as described above, but may also be linear ones. In that case, one predetermined straight line can be used as described above. As in the case, the gradation processing conditions to be used are determined by rotating or shifting and positioning so that Pmax, Pm1n, etc. correspond to Rmax, Rmin. The determination of the gradation processing conditions by this method is not based on the patterned part or the projection method as in the case of a musician, but is carried out only on the basis of image information within the irradiation field. As mentioned above, the gradation processing of the ray image information is performed on each 1lf
If the gradation processing is performed according to the gradation processing conditions set according to the shadow image (image information), for example, if the shadow image of each individual image is Even if the rJJl ray energy level range accumulated and recorded on each VRI shadowed sheet fluctuates due to fluctuations in the rJJl ray energy level range, the necessary subject image information can always be observed in any visible output image regardless of the fluctuations. This is convenient because it can be displayed in an appropriate density range suitable for image interpretation. Further, in this case, according to the present invention, since the determination can be made based on image information that does not include scattered radiation information noise, the desired image information range can be determined more accurately from the image information histogram, and as a result, the above-mentioned necessary subject image The effect of displaying information within the appropriate concentration range is more pronounced. This method of determining gradation processing conditions is particularly applicable to image information read based on reading conditions determined without considering fluctuations in the Group 94 energy level range recorded in individual VR shadows as described above. It is beneficial to use it when processing. The first and second inventions described above can be modified in various ways without departing from the gist thereof, and are not limited to the embodiments described above.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the stimulable phosphor sheet shaded by applying irradiation field aperture, Figure 2 is an enlarged view of section A in Figure 1 and is a diagram showing digital image data at each position, Figure 3 Figures (a) to (') are diagrams showing the difference operators, respectively. Figure 4 is the digital image 1 on line 9Jx in Figure 1.
Figure 5 is a diagram showing the difference values obtained by performing differential processing on the digital image data in Figure 4. Figures 6, 7, and 8 are diagrams showing the difference values calculated using different difference operators. Figure 9 shows the difference image created.
Figure 1 shows a difference image when the =1 field is circular, and Figure 10 is a diagram showing an example of a method for determining gradation processing conditions from a desired image information range. 10... Recording medium (stimulable phosphor sheet) 12...
Irradiation field Fig. 2 Fig. 3 (a) (b) (c) (d) (
e) (f) Figure 7 Figure 8 Figure 9

Claims (3)

[Claims] (1) A method for recognizing the irradiation field when radiation image information is recorded on the recording medium by applying an irradiation field aperture, the method comprising: determining each position on the recording medium from the image information read from the recording medium; Find the image data in , perform a difference process on this image data to find the difference between the image data to create a difference image consisting of the difference values, prepare a predetermined threshold Th, and use the difference image or the difference image. A processed difference image that has been subjected to a predetermined process is scanned in one direction to detect a predetermined section sandwiched between a difference value of +Th or more and a difference value of -Th or less on each scan line, and each of the scan lines An irradiation field recognition method characterized by recognizing the sum of a predetermined section above as an irradiation field. (2) A processed difference image obtained by performing predetermined processing on the difference image has a difference value of +Th or more and -Th with respect to the difference image.
The patent claim is characterized in that the image is a threshold-processed difference image that has been subjected to threshold processing to encode all or part of the difference values so that the following difference values can be distinguished from other difference values. The irradiation field recognition method described in Scope 1. (3) A method for determining image processing conditions for processing image information read from a recording medium on which radiation image information is recorded by applying irradiation field aperture, the method comprising: Image data at each position on the recording medium is obtained, and this image data is subjected to differential processing to determine the difference between the image data to create a differential image consisting of differential values, a predetermined threshold Th is prepared, and the +T on each scanning line by scanning the difference image or the processed difference image obtained by performing predetermined processing on the difference image in one direction.
A predetermined section sandwiched between a difference value of h or more and a difference value of -Th or less is detected, the sum of the predetermined sections on each scanning line is recognized as the irradiation field, and the image information read from the recording medium is A method for determining image processing conditions, characterized in that the image processing conditions are determined based on image information within the recognized irradiation field.