JPS6215536A - Determining method for readout condition of radiation image information - Google Patents

Abstract

PURPOSE:To determine optimum readout condition by recognizing the size of a closed curve formed by connecting aimed points obtained so far in order as an irradiation field when the aimed points are searched for successively and the 1st aimed point is reached, and determining primary readout condition on the basis of preread image information in the irradiation field. CONSTITUTION:Digital data are obtained at respective positions on a sheet and differentiated to form a differential image and the contour of the irradiation field is detected on the basis of the differential image. One of presence positions of the irradiation field is detected as the 1st aimed point and the contour of the irradiation field is traced from the 1st aimed point to recognize the irradiation field. In this tracing, the position which has the largest differential value among peripheral positions adjoining to the 1st aimed point is searched for as the 2nd aimed point and then the position having the largest differential value among peripheral positions adjoining to the 1st aimed point except said aimed point (1st aimed point) is searched for as the 3rd aimed point. Thus when the position adjoining to the 1st aimed point is searched for as a new aimed point, the aimed points obtained so far are connected to form the closed curve, whose inside area is recognized as the irradiation field.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a method for determining reading conditions for radiation image information used in a radiation image information diary playback system using storage f11 phosphor used for medical diagnosis, etc. Regarding.

(Technical cost of invention and prior art) Certain types of phosphors are exposed to radiation (X-rays, α-rays, β-rays.

When irradiated with γ-rays, electron beams, ultraviolet rays, etc., a part of this ray energy is accumulated in the phosphor, and when the phosphor is irradiated with excitation light such as visible light, the energy is accumulated. It is known that phosphors exhibit stimulated luminescence depending on energy, and phosphors exhibiting this property are called stimulable phosphors.

Using this accumulation ↑tt phosphor, radiation image information of a subject such as a human body is recorded on a sheet-shaped accumulation phosphor, and then this stimulable phosphor sheet is exposed to excitation light such as a laser beam. Scan and generate photostimulated light [! 'Then, read this stimulated luminescent light photoelectrically.
The applicant has proposed a radiation image information recording and reproducing system that outputs the radiation image of the subject as a visible image to a recording material such as a photographic light-sensitive material or to a display device such as a CRT based on this image signal. 1985-12429 bow, 56-113958-1).

One aspect of the radiation image information recording and reproducing system described above includes:
A stimulable phosphor sheet, in which radiation image information of a subject is stored and recorded using the h-ray-1 energy level as a medium, is used as excitation light.J, Reno! = scanning, and by this scanning, the stimulated luminescence light emitted from the sheet is read by a photoelectric reading means to obtain an electrical image signal 8 for reproducing a visible image for diagnosis. Therefore, in advance, the above-mentioned Sea 1 to
scan to read the outline of the image information accumulated and recorded on this sheet. The main reading is performed according to the main reading, and the image signal q'd by this main reading is input to the image processing means, and the image processing means obtains an output image suitable for the diagnostic purpose according to the imaging site, imaging method, etc. A system is known that processes an image signal on a computer and reproduces this image signal as a visible output image on a photosensitive and optical system. It is disclosed in Japanese Unexamined Patent Publication No. 58-67240.

Here, the reading conditions are a general term for various conditions that affect the relationship between the photostimulation and the amount of light emitted during reading and the output of the reading device, for example, the relationship between input and output. It refers to the read gain (sensitivity), scale factor (latitude), or power of excitation light used for 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 surface during pre-reading is lower than the excitation light used for main reading. It means smaller than the edge. A method of lowering the level of the excitation light of the pre-reading than the excitation light of the main reading, a method of reducing the output of the excitation light source such as a laser light source, and a method of lowering the output of the excitation light source such as a laser light source, and a method of reducing the excitation light emitted from the light source in the next optical path. Attenuation due to ND fill, AOM, etc. 1! In addition, there is a method in which the light source for pre-reading and the light source for main reading are separately set, and the output of the former is reduced by the output of the latter. How to make the diameter appear as a human, how to make the scanning speed of the excitation light a human,
Examples include a method of transferring stray electricity of the stimulable phosphor sheet 1 to a person.

In this way, prior to the main reading, we have grasped the outline of the image information stored on the sheet in advance at This eliminates inconveniences caused by fluctuations in the radiation energy level range accumulated and recorded on the sheet due to fluctuations in the subject or imaging area or fluctuations in the radiation energy level, etc., making it possible to always perform actual reading under desirable reading conditions. .

31. As a macroscopic method for determining the reading position during main reading based on the image information obtained from such pre-reading,
For example, if you calculate the histogram of the amount of stimulated luminescence in the look-ahead, you can carefully calculate the maximum amount of stimulated luminescence of the desired image information range from this histogram by 3 ma.
x and the minimum stimulated luminescent light silk 3 min, and this Sm
ax and S min are respectively l in the visible output image.
111 large signal level Q of the desired input signal range in the image processing means determined by the maximum density (1') max and minimum density (fl 11m1n)
The present applicant has filed an application for a method of determining reading conditions for main reading so as to correspond to the maximum and minimum signal levels of 010 (Japanese Patent Application No. 12658/1982).

On the other hand, in order to avoid irradiating radiation to areas that are not necessary for humane diagnosis, or if radiation is applied to areas that are unnecessary for diagnosis, scattered radiation will enter the areas necessary for diagnosis from that area, reducing contrast resolution. To prevent this, it is preferable to narrow down the radiation irradiation field when recording radiation image information. However, when the radiation field is narrowed down in this way, the stimulable phosphor sheet 1
- Scattered rays generated from the subject in the irradiation field enter the field of irradiation, and the highly sensitive phosphor sheet accumulates and records these scattered rays, so the histogram of the amount of stimulated luminescence obtained by looking ahead This includes the amount of stimulated luminescence based on this scattered radiation.

Based on this scattered radiation, the amount of stimulated luminescence outside the irradiation field on sheet 1 is sometimes larger than the amount of stimulated luminescence inside the irradiation field, so the obtained histogram shows that the amount of stimulated luminescence inside and outside the irradiation field It is difficult to make a distinction. Therefore, as mentioned above, from the histogram, Smax
, Sm1n, and when determining the reading conditions from this, the minimum value of the stimulated luminescence light amount in the Kiri irradiation field should be Sm1n, but the minimum value of the stimulated luminescence light amount due to the scattered radiation outside the irradiation field is Smin. There may be cases where this is done. In this way, the minimum value of the amount of stimulated luminescence outside the irradiation field is S si
If it is n, the value is generally lower than the minimum value of 5% of stimulated luminescence within the irradiation field, so in the main reading, scattered radiation unnecessary for diagnosis will be recorded in the low lI lean area, and therefore necessary for diagnosis. 11 of the image becomes too high, and as a result, the contrast decreases, making it difficult to make a satisfactory diagnosis.

That is, when shooting with a narrowed irradiation field, scattered radiation generated from the subject enters the irradiation field on the sheet,
The image information obtained by 1η by pre-reading includes information based on this scattered radiation, so even if the reading conditions are determined based on such pre-read image information, the optimal reading line n cannot be determined. As a result, it is difficult to obtain an IA image that is suitable for observation and interpretation.

(Object of the Invention) In view of the above-mentioned circumstances, the object of the present invention is to provide a method for determining reading conditions for main reading based on image information obtained by pre-reading. The object of the present invention is to provide a method that can eliminate the above-mentioned inconvenience caused by narrowing the irradiation field and determine optimal reading conditions.

(Structure of the Invention) In order to achieve the above object, the reading condition determination method according to the present invention calculates digital image data at each position on a stimulable phosphor sheet from image information obtained by pre-reading,
This digital image data is subjected to differential processing, and in the differential image made up of the obtained differential equations, first find an arbitrary position where the differential value is the maximum or a predetermined value or more, make this the first point of interest, and then Find the position with the maximum differential value from among the surrounding positions adjacent to this first point of interest, set this as the second point of interest, and then Divide the point of interest, that is, the first point of interest (search for the position with the maximum differential value among the positions, set this as the third point of interest, and then
The process of searching for points of interest is repeated to find new points of interest one after another, and when a position adjacent to the first point of interest is found as a new point of interest, that is, the points of interest are sequentially searched using the above method and the point of interest is searched for as the first point of interest. When it returns to the point, it recognizes the inside of the closed curve formed by sequentially connecting the points of interest up to that point as the irradiation field, and determines the reading conditions for main reading based on the pre-read image information within this irradiation field. Features.

Note that the above-mentioned [surrounding positions adjacent to the attention point] do not necessarily have to be all of the surrounding positions adjacent to the attention point. For example, if the contour of the irradiation field is known in advance, a part of the position may be determined according to the shape of the contour.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The embodiment described below uses a rectangular illumination field diaphragm as shown in FIG.
This is a method for determining the reading regulations of a stand for reading a stimulable phosphor sheet 12 that has a value of 0. Dimensions indicated in the diagram
↑ indicates the scanning direction when scanning 2 and pre-reading image information, and the y-axis indicates the sub-scanning direction.

First, the image information accumulated and recorded on the J storage f1 phosphor sheet 12 shown in FIG. 1 is read by performing the above-described pre-reading.

Reading the image information of the stimulable phosphor sheet 1-1.2h) by pre-reading means scanning the sheet 12 with 6n IR light in advance and converting the stimulated luminescence light emitted from the sheet 12 into a photoelectric conversion means (reading). -) means to input information consisting of an electrical signal corresponding to the amount of stimulated luminescence at each scanning point on the sheet 12 (that is, each image m, >in).

Next, digital image data at each position on the sheet is obtained from the image information read as described above. In obtaining this digital image data, it may be obtained directly from the image information read by the above-mentioned pre-reading, or it may be obtained by subjecting the image information to pre-processing such as spatial filter processing (1).

If you want to find it directly, for example, find the position on the sheet 1ii [! ii! The above-mentioned pre-read image information of pixels corresponding to each setting unit position may be digitized in units of 2 lines and used as digital image data at that position.

When calculating by performing preprocessing such as spatial filtering,
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 of the position may be calculated based on pre-read image information of a plurality of pixels corresponding to the position and the heel surrounding the position. good. Median filter processing can be cited as one of the latter calculation methods. This median filter processing consists of image information of a predetermined pixel (position) and its surrounding pixels (position), and the median value (quantization level) of the image information (quantization level).
(median value) as the image information of a predetermined pixel (position).

A general example of this median filter processing will be explained with reference to FIG. Figure 2 (a) is a diagram showing an original image 14 consisting of image information for pre-reading each pixel, and each square in the figure represents one pixel. show. FIG. 2(b) is a diagram showing a median filtered image 16 consisting of digital image data at each position obtained by performing the above median filtering on the image information of each pixel in the original image. In this specific example, the position is set in pixel units, so the processed image 16
Each position therein is also called a pixel. 1 Using a Y1 predetermined size mask, for example, a 3×3 1 size mask 18 having a width of 3 pixels in the vertical and horizontal directions,
The mask 18 is arranged in the original image -12=image 14 so that a predetermined pixel (the diagonally shaded pixel in the figure) is located in the center of the mask, and at that time, the nine pixels included in each mask are The median value of the image information is digitized and used as the digital image data of the predetermined pixel, and this processing is applied to all pixels in the original image 14 (however, it cannot be applied to pixels located at the outermost periphery, so (excluding pixels)
One piece of digital image data is then obtained for that pixel, and a median filtered image 16 consisting of this data is obtained.

Note that if a 3×3 size mask is used, it is not possible to perform median filter processing on the outermost pixels as described above, so the processed image 16 is smaller than the original image 14 by one outermost pixel.
7, so for example, this outermost pixel portion 17
A quantization level O (zero) can be substituted as image data. The size of the mask is not limited to 3×3. In addition, in order to prevent the processing surface 918 from becoming smaller, for example, median filter processing may be performed on the assumption that there are pixels around the original image [4 that have the same quantization level as the outermost pixels of the original image]. . By performing the above median filter processing, it is possible to remove noise when the crystallization level is extremely high or low compared to surrounding pixels, and the advantage is that the irradiation field contour information is not blurred. There is.

Note that the above preprocessing is not limited to the median filter processing described above, but can be any spatial filter processing that has the characteristics of leaving necessary information such as the contour of the irradiation field and removing unnecessary information such as noise. Anything is fine.

After obtaining digital image data at each position of the sheet soil as described above, the image data is then subjected to differential processing to create a differential image consisting of differential values.

Differential processing may be performed using any method with 41 rows.

FIGS. 3(a) and 3(b) are diagrams each showing a processed image, and each square in the diagram represents one A11 position.

For example, as shown in FIG. 3(a), when differentiating the digital image data at a predetermined position 20 in the processed image 16, a mask 22 with a pixel size of 2×2 is used.
2 is arranged so that the predetermined position 20 is located in the upper left part of the mask 1, and digital image data at four positions included in the mask 22 are <a, b, C, d as shown in the figure. Do the following calculation and buy a' of A at the specified position? Differential processing may be performed by using a differential value at O and performing this differential value for each position. Further, instead of using the V-open equation, the following calculation may be performed to perform differential processing.

Of course, differential equations other than these may also be used.

Furthermore, although the above example is a first-order differential process, Fig. 3(b)
As shown in the figure, a mask 24 with a pixel size of 3 x 3 is used, the mask is arranged so that a predetermined position B26 is located in the center of the mask, and the digital image data of the nine positions included in the mask are transferred as shown in the figure. Like<a.

b, c, d, e, f, g, h, i, and perform the following calculation to make e' the differential value at a predetermined position 26. good.

Next, as described above, the contour of the irradiation field is detected based on the differential image. The above digital image data corresponds to the magnitude of 1 nergini of the radiation incident on the sheet, so the image data outside the irradiation field generally has a low quantum,
level, and the image data within the irradiation field generally has a quantum level that is one higher. Therefore, the differential value of the image data at the position where the irradiation field contour exists is generally at a larger quantum level than the differential value of the image data at other positions.

Therefore, in the differential image, the position where the differential value is maximum or the position where the differential value is greater than or equal to the predetermined standard when the predetermined value is appropriately set can be recognized as the irradiation field contour, and 1. Since the irradiation field contour is formed by one closed curve, the irradiation field contour exists. When focusing on one position, there is always a position where an irradiation field contour exists among the surrounding Φ positions adjacent to the position, and the differential value of the first position is higher than the differential value of other adjacent surrounding positions. In other words, it can be said that the irradiation field contour exists at the position where the differential value is the largest, at least among the adjacent surrounding positions.

The method according to the present invention is based on the above-mentioned fact, and searches out and tracks the positions where the irradiation field contour exists in the differential image one after another, thereby detecting the irradiation field contour. The tracking process consists of two stages: a detection stage of the first point of interest competing at the same starting point, and a tracking stage of tracing the contour existing position from the first point of interest.

First, the differential image is scanned to find an arbitrary position where the differential value is the maximum or is greater than or equal to a predetermined value and is set as the first point of interest.

As mentioned above, the differential values of the five positions where the irradiation field contour exists are larger than those of the other positions. Therefore, if an appropriately set predetermined value is used, the position where the differential value is greater than or equal to the predetermined 1 is the irradiation field. It can be determined that this is the position where the contour exists, and of course, the position where the differential value is maximum can also be determined to be the position where the irradiation field contour exists. Therefore, first, one of the irradiation field contour existing positions is determined by the method described above.
one point is detected, and that position is set as the 1st nth point.

Next, n traces of the irradiation field contour are made from this first point of interest to recognize the irradiation field. This jrj trace first searches for the position where the differential value is maximum among the surrounding positions adjacent to the first point of interest, sets this as the second point, and then
The position with the maximum differential value is searched among the positions of the circumference III adjacent to the point of interest, excluding the previous point of interest (the first point of interest), and this is set as the third point of interest. This is done by repeating the process of searching for pouring points and finding new points of interest one after another. Then, when a position adjacent to the first point of interest is found as a new pouring point, the previous H-point is connected and the inside of the curve is recognized as the irradiation field.

The above tracking can be carried out 2) using a mask as shown in FIGS. 4 and 5, for example.

The mask shown in FIG. 4 is a 3×3 pixel + fiz mask. For example, when tracking a rectangular irradiation field outline as shown in FIG. 6, the differential image 28 is ni [
The mask is placed so that the first point of interest △ on the irradiation field contour obtained as shown in Figure 4 is located at the center of the mask (the shaded area in Figure 4). Ii'l alJ in the mask? The position with the largest differential value among (
(excluding the first attention point 8) to the next pouring point, that is, the second attention point B
Then, as shown in Figure 6(b), the second 'rt f'
Move the mask so that point I B is located in the center of the mask, and find the position with the highest differential value among the positions in this mask (excluding the first and second points of interest △ and B, which are the previous points of interest). next?
↑The eye point, that is, the 3d eye point C, is set as the 4H eye point as shown in Figure 6 (C), and the 5th attention point F as shown in Figure 6 (d >), and new attention is sequentially set. Find the point, 6th
As shown in Figure (e), the position adjacent to the 1st n 1st point 8 is the new nth
The inside of the closed curve 30 connecting the point △ to the nth sex [] is recognized as Teru@glP10. Note that the arrow l in Figure 6
Shows the tracking direction of the JL beam.

1 mask shown in Fig. 5 covers all surrounding pixels (8 pixels) adjacent to the pixel of interest ~ 1)
However, some of the surrounding pixels (4
It is configured to cover only pixels (pixels),
This mask can be used by changing its orientation depending on the tracking direction. Note that the arrows in FIG. 4 indicate the tracking directions when using each mask.

A case will be described in which a rectangular irradiation field is created using this mask.

First, if the differential image is scanned to find the position where the differential Iff is maximum and that position is set as the first point of interest, as shown in Fig. 7<a>, the first note 1"I r: , +△ ×, one position ■ adjacent to the y-axis direction.

TI, III, [Find the position where the differential value is maximum in V, and move from the first attention point A to the position of the child's differential value n people (
] to start tracking. In the case shown, place tf'? Assuming that l has the maximum differential value, tracking begins toward that position (J) and to the left.

In this case, the tracking direction is to the left, so the tracking direction shown in Fig. 5 (
Using a mask oriented as shown in a), apply the first t to the diagonally shaded part of the mask as shown in FIG. 7(b).
Arrange so that the t'th point △ exists, find the position with the largest differential value among the positions in the mask (excluding the first point of interest A), and set it as the next second point of interest B, Next, move the mask and place this second point of interest B on the diagonal line part of the mask.
In that state, find the position with the largest differential value among the positions in the mask (excluding the previous points of interest 1st and 2nd points A and B) and move it to the next 3rd point. Select points of interest and repeat this process to find new points of interest. Therefore, as shown in Fig. 7(b), until the position of the upper left corner reaches the spout point C, the tracking direction is to the left, so part b in the mask is always the position of the maximum differential value. , to that extent, the detection of the point of interest is continued using the mask shown in FIG. 5(a). However, the position C of the upper left part]
When we search for the point of interest, the lower part d has the maximum differential value. In this way, in the mask of Figure 5(a), d
When the differential value reaches the maximum, detection of subsequent points of interest is continued using the mask shown in FIG. 5(b).

That is, the next target jiE is detected by positioning the target point in the diagonally shaded area of the mask in FIG. 5(b) in the manner shown in FIG. 7(C). Then, until the position of the lower left corner becomes the point of interest F, the tracking direction is downward, so one part in the mask always has the maximum differential value, and to that extent, this fifth,
Continue detecting the point of interest using the mask shown in Figure (b). Then, when the position of the lower left corner becomes the point of interest F, the differential value becomes maximum at the d part in the mask. Using a mask, detect the point of interest in the same way as described in -E. When the position of the lower right corner becomes the point of interest G, the d section of the mask will have the maximum differential value, so As shown in Fig. 7(e), continue detecting the point of interest in the same manner as above using the mask of Fig. 5(d), and when the position of the upper right corner becomes the point of interest 1, the next step is to use the mask again in the same way. Since the differential value is maximum at the d part of
Continue detecting the point of interest in the same manner as above using the mask of The inside is recognized as the irradiation field 10. Note that the arrow in the figure indicates the tracking direction.

In the above example, the position of the maximum differential value in the differential image is
Although we have described the case where the point of interest is set as the first point of interest, if any point whose differential value is equal to or greater than a predetermined value is set as the first point of interest, tracking may be performed in the same manner as described above. However, when using the mask shown in Figure 5, the mask used depends on the direction of tracking, so it is necessary to determine the tracking direction. As shown in (1), the scanning direction (direction of arrow J) when searching for the first point of interest A may be set as the tracking direction, and the mask in the direction A may be used initially.

After determining the irradiation field as described above, the reading conditions for the main reading are determined based only on the image information within this irradiation field among the image information obtained by pre-reading. These reading conditions can be determined in various ways based on the image information within the irradiation field, but for example, as described above, a histogram of the exhaustion light amount within the irradiation field is created, and from this histogram, a predetermined maximum The amount of emitted light S max and the minimum stimulated emitted light interval S min are determined, and these 3max, 3
Based on m1n, it is possible to determine the ≠ taking condition.

Note that the determination of reading conditions is not limited to the case where the reading conditions are determined based only on the pre-read image information within the irradiation field.
The determination can also be made by taking into account the part of the subject to be imaged, such as the chest or abdomen, and the imaging method, such as simple, contrast, tomographic, or magnified imaging.

- After determining the irradiation field as described in F and determining the reading conditions for the main reading based on the image information within this irradiation field, the main reading is performed according to the determined reading conditions. As disclosed in Japanese Patent Application Laid-Open No. 120346/1982, it is preferable to limit the reading area to the determined 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.

Note that when O (zero) is assigned to the outermost pixel portion 11 in the processed image 16 as shown in FIG. 2(b), even if the irradiation field is narrowed inside the stimulable phosphor sheet. However, the differential value at the pixel at the outermost circumferential portion, which should essentially be the contour of the radiation field, becomes large, and that pixel portion is detected as the contour of the radiation field. Furthermore, if 0 (zero) is not assigned to the outermost pixel portion in the processed image as described above, a similar result can be obtained by performing differential processing assuming that O (zero) exists around it.

Although the above embodiment deals with the case of a rectangular irradiation field, the present invention is also applicable to the case of a circle or other non-rectangular irradiation field.

Further, in the above embodiment, one stimulable phosphor sheet 12
We have dealt with the case where one irradiation field 10 exists above the
For example, the present invention is also applicable to so-called divided imaging in which one sheet is divided into two sections and each section is imaged with an irradiation field aperture applied. Immediately,
Even in the case of divided imaging, if each section is considered as one sheet, one irradiation field will exist on that one sheet. Therefore, by obtaining information in advance that it is divided imaging, the present invention can be applied to each of the sections. It is sufficient to apply it to each category.

(Effects of the Invention) As described in 1, the method according to the present invention recognizes the irradiation field from the pre-read image information, and determines the main reading line f1 within this terutana field based on the pre-read image information. In order to recognize the above-mentioned irradiation field, a differential image is created based on the pre-read image information, an arbitrary point in this image where the differential value is the maximum or a predetermined value or more is set as the first point of interest, and this 1d eye point is set as the first point of interest. Find the position with the maximum differential value among the surrounding positions that are adjacent to and cover it, and make this the new second point of interest.After that, find new points of interest one after another in the same way, and find the position that is adjacent to the first point of interest. When a new point of interest is found, the area inside the closed curve connecting the previous points of interest is recognized as the irradiation field.

As described above, in the mechanical differential fractionation, the differential value at the position where the irradiation field contour exists is larger than that at other positions. Therefore, the above-mentioned first point of interest, which is a unique position of f1 with a maximum differential value or a predetermined value set appropriately, is a position on the irradiation field contour, and surrounding objects adjacent to this first point of interest are positions on the irradiation field contour. The position of the maximum differential value in η is set as the second point of interest, and repeating this method to find new points of interest one after another means sequentially tracking the positions on the irradiation field contour. Ru.

Therefore, according to the method according to the present invention, it is possible to accurately recognize the irradiation field, and even when the 61 fields are narrowed down before bundling, the scattered rays applied to the irradiation field on the sheet Since the reading condition f1 is determined based only on the effective image information within the field of view 1, the optimum reading condition can always be determined.

[Brief explanation of the drawing]

Figure 1 shows the phosphor sheet; Figure 2 (a) shows the original image consisting of pre-read image information for each pixel; Figure 2 (b) is a diagram showing a processed image obtained by median filtering the original image, and Figures 3 (a) and (b) are diagrams each showing the position in the processed image and the mask used when performing differential processing. , Figures 4 and 5 (a) to (d) are diagrams showing the master used when searching for new points of interest, and Figure 6 (a).
) to (e) are shown in Fig. 4. An explanatory diagram of how to find new points of interest using the M7 screen, and Fig. 7 (a) to (()
) is an explanatory diagram of a method for finding new points of interest using the masks shown in FIGS. 5(a) to (d).・・・Original image 16...place
Image 28...Differential image 30...Closed curve 0 ■ 0 Shizu no No. 71 (d) (e) 2nd 2nd F - Shin d (CJ) (C) (f) 28 Gu

Claims (1)

[Claims] By irradiating excitation light onto a stimulable phosphor sheet in which radiation image information is accumulated and recorded with irradiation field aperture,
The radiation image information stored and recorded on the stimulable phosphor sheet is emitted as stimulated luminescence light, and this stimulated luminescence light is read photoelectrically to obtain an electrical image signal for outputting a visible image. Prior to this, pre-reading is performed to read the radiation image information accumulated and recorded on the stimulable phosphor sheet using excitation light with an energy lower than that of the excitation light used in the main reading, and the information obtained by this pre-reading is performed. In the method for determining reading conditions for radiation image information in which reading conditions for the main reading are determined based on image information, digital image data at each position on the stimulable phosphor sheet is obtained from the image information obtained by the pre-reading, and Digital image data is subjected to differential processing, and in a differential image consisting of the obtained differential values, an arbitrary position where the differential value is the maximum or a predetermined value or more is selected as the first point of interest,
Next, search for the position with the maximum differential value from among the surrounding positions adjacent to this first point of interest and set this as the second point of interest, and then Search for the position with the maximum differential value from among the positions excluding the previous point of interest, define this as the third point of interest, and then repeat the process of searching for this third point of interest to find new points of interest one after another.
When a position adjacent to the first point of interest is found as a new point of interest, the inside of the closed curve connecting the previous points of interest is recognized as the irradiation field, and the image information obtained by the pre-reading within this irradiation field is used. A method for determining reading conditions for radiation image information, characterized in that reading conditions for the main reading are determined based on the main reading.