JPS6215539A - Determining method for readout condition of radiation image information - Google Patents

Abstract

PURPOSE:To determine optimum readout condition by calculating a characteristic value from image data at a position where a differential value exceeds a specific value, connecting positions where image data is the same with the characteristic value and obtaining a contour line, and recognizing the area inside the contour line as an irradiation field. CONSTITUTION:A differential value delta at each position is calculated by primary differentiation to obtain digital image data TA, TC, and TD on a line Lxn at contour candidate points A, C, and D found by threshold value processing using the specific value T0, thereby calculating the characteristic value Th of those digital image data. Positions A'-D' where digital image data is equal to the characteristic value Th are found and positions A'-B' and C'-D' where digital image data is larger than the characteristic value Th are decided as the range of the irradiation field on the line Lxn. Then, irradiation field contour points on an optional (y)-axial line Lyn are also detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to the storage of radiographic image information used in medical diagnosis, etc. Regarding reading section 1'1 determination method θ.

(Technical fruits and vegetables of the invention and prior art) Certain phosphors emit m = rays (X-rays, α-rays, β-rays.

When irradiated with T-rays, electron beams, ultraviolet rays, etc., some of this radiation energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, it is accumulated. It is known that phosphors exhibit stimulated luminescence depending on the energy, such as ', -+ 'I'1. ' A phosphor exhibiting t4 is called a stimulable phosphor.

Using this stimulable phosphor, radiographic image information of a subject such as a human body is recorded on a -1 sheet of stimulable phosphor, and then the stimulable phosphor sheet is excited with 1 noser light, etc. The stimulated luminescence light is captured by scanning with light, and the stimulated luminescence light is read photoelectrically to obtain an image signal. 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 an OR. No. 56-11395, etc.

) As one aspect of the above-mentioned Kenkensen image information recording and reproducing system,
A stimulable phosphor sheet, in which the active line image information of the subject is stored and recorded using the active line energy level as a medium, is scanned with excitation light, and this scanning causes the emission from the above-mentioned sheets 1 to 1.
Reading the q-stimulated luminescence light with a photoelectric reading means to reproduce a visible image for diagnosis and obtain an electric image signal 1
Prior to the main reading J, "pre-reading" is performed in which the sheet is scanned with excitation light of a lower level than the excitation light used for this main reading to read the outline of the image information accumulated and recorded on this sheet, and by this pre-reading, The reading method when performing the book reading based on the obtained image information! 1, perform the actual reading according to the reading conditions, input the image signal obtained by this actual reading to an image processing means, and use the image processing means to determine the image signal suitable for the diagnostic purpose according to the surface shape part, the illumination method, etc. Systems are known that process an image signal so as to obtain an output image, and reproduce this image signal as a visible output image on a photographic light-sensitive material. Japanese Patent Publication No. 58-672
It is disclosed in Publication No. 40.

Here, the reading condition fl is a general term for various conditions that can affect the relationship between the amount of luminous R light emitted during reading and the output of the reading device, such as the reading gain that determines the relationship between human output. (sensitivity), Suf1-Ruf1kta (Rachiji code) or 1. Jl, the power of the excitation light during reading, etc. are changed in meaning.

In addition, if the excitation light used for pre-reading is 1 novel lower than the excitation light used for main reading, LJI, the effective JNel key of the excitation light received per medium area to the stimulable phosphor sea 1 during pre-reading. This means that it is smaller than when reading a book. Methods for making the pre-reading excitation light lower than the main reading excitation light include reducing the output of the excitation light source such as a laser light source, and using an ND filter, AOM, etc. in the optical path of the excitation light emitted from the light source. Attenuation methods, methods of providing a light source for pre-reading and a light source for main reading separately and making the output of the former smaller than the output of the latter, and furthermore methods of increasing the beam diameter of the excitation light ,
Examples include a method in which the scanning speed of the excitation light is set at a certain speed, a method in which the transport speed of the stimulable phosphor sheet is set at a certain speed, and the like.

In this way, prior to the actual reading, the outline of the image information stored on the sheet is grasped in advance, and by performing the actual reading in accordance with the reading conditions determined based on the outline of this image information, it is possible to Eliminate inconveniences caused by fluctuations in the range of radiation energy levels accumulated and recorded on the sheet, which are caused by fluctuations in energy levels or fluctuations in the amount of radiation exposure, etc.
Main reading can always be performed under desirable reading conditions.

IJ is a specific method for determining the reading line 1'1 during main reading based on the image information obtained by such pre-reading.
, for example, obtain a histogram of the amount of stimulated luminescence light in pre-reading, and use this histogram to determine the maximum stimulated luminescence light m S m in the desired image information range in this histogram.
ax and the minimum stimulable luminescent light shell 3m1n, and this S m
When aX and Sm1n are combined, the visible output image (maximum depth 10I of the appropriate density range) maX and minimum density □m
The maximum signal level Qmax and the minimum signal level Qmi114 of the desired human power signal 8 range in the image processing means determined by 'τ'114 correspond to the reading conditions '1-
A method for determining this has been filed by the present applicant (Japanese Patent Application No. 12658Q, 1982).

On the other hand, in order to avoid irradiating θ1 radiation to areas that are necessary for human diagnosis, or to irradiate radiation to areas that are unnecessary for diagnosis, scattered radiation will enter the areas necessary for diagnosis. To prevent this, it is often preferable to narrow down the radiation irradiation field when recording radiation image information (h1). However, when the third field of radiation is narrowed down in this way, 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 l~1 also accumulates and records this scattered ray, by reading it in advance, the amount of stimulated luminescence based on this scattered ray will also be included in the hist~g of the amount of stimulated luminescence to be sought. .

Since the amount of stimulated luminescence outside the irradiation field based on this scattered radiation is sometimes larger than the amount of stimulated luminescence inside the irradiated bone, the obtained histogram shows that the amount of stimulated luminescence inside and outside the irradiation field is It is difficult to distinguish the amount of light. Therefore, as mentioned above, 3 m from the rainbow stogram
When calculating ax', , s min and determining the reading conditions from this, the minimum value of the stimulated luminescence light amount within the 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 Sm1n. This may occur if the size is 5m1n. In this way, when the minimum value of the amount of stimulated luminescence outside the irradiation field is set to 3 m1n, that value is generally lower than the minimum value of the amount of stimulated luminescence in the bone within the IJ1 irradiation field, so in the main reading, scattered radiation unnecessary for diagnosis is excluded. Therefore, the density of the image in the portion necessary for diagnosis becomes too high, and as a result, the contrast deteriorates, 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 on the sheet, and the image information obtained by pre-reading will include information based on these scattered rays. Therefore, even if reading conditions are determined based on such sharp image information, it is difficult to determine the optimal reading condition. Obtaining a visible image becomes an office job.

(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 inconvenience caused by the above-mentioned illumination q4 field aperture and determine the optimal reading conditions even in the case of

(Structure of the Invention) In order to achieve the objective of the reading strip 1'1 determination method according to the present invention, C is applied to each circle on the stimulable phosphor sheet from the image information obtained by pre-reading. Obtain digital image data, and place the stimulable phosphor sheet in a predetermined direction in -rows on the stimulable phosphor sheet.
differential processing of the digital image data, and the absolute value of the differential value is below a predetermined value. If the candidate point of the irradiation field contour on that line is set at a position exceeding
- Special features of the digital image data from the evening. Detection of the irradiation field contour points is carried out for each line in a predetermined range of 1-1 phosphor sea 1. Recognize and recognize the inside of the line connecting the irradiation field as the irradiation field, and use the image information obtained by the above-mentioned pre-reading within this irradiation field.
The method is characterized in that reading conditions are determined.

(Actual 1+l1li aspect) Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings.

Embodiment IJ to be explained below, Embodiment I shown in FIG.
J, one stimulable phosphor sheet 10 is divided into two sections (J
Minute ^ 11 and a rectangular light 04 in each section! I'f
Aperture row 7:z,.

This is fiθ, which is determined by reading article 1'1 in the case where the award is given.

In this method, first, from the image information obtained by pre-reading th (-2 by 1q) as described above, the previous n[: W;
d-3&j digital image data is obtained at each position on the phosphor sheet.

Image information obtained by the above-mentioned pre-reading and 1.12, stimulated luminescence obtained by pre-reading excitation light scanning) 1f, 5. −
This refers to information consisting of an electric signal H corresponding to the amount of stimulated luminescence light for each scanning point (that is, each pixel) on the phosphor sheet, which is read by a photoelectric conversion means and accumulated at a ratio of 4:1. This information, of course, corresponds to the service line image information stored and recorded in the record sheet h.

FIG. 2(a) is an enlarged view of the storage/i/1 phosphor sheet 100G section shown in FIG. f (1,1), f (1,2), ... L in each pixel
t each pixel (1, 1>, (1, 2>, ...)
ni [Puru = 11 - Indicates the digitized version of the above image information. In addition, in this embodiment, as shown in Lt FIGS. 1 and 2, the X-axis and the Y-axis are set to be orthogonal to each other, and the X-axis direction is the main scanning direction, and the X-axis direction 1 is the sub-scanning direction. matches. FIGS. 2(b) and 2(C) will be explained later.

- In order to obtain the digital image data for each position on the tote from the image information mentioned above, it is first necessary to set the positions from sea 1 to above. This 117th setting ((J
This may be carried out in the middle of five pixels, or a plurality of pixels in a certain relationship, for example, three to five pixels arranged in a certain direction, may be grouped together at one position. In the former case, the digital image data at each position (d54) means the digitized image information of the pixels corresponding to the positions, and in the latter case, the digital image data at each position. IJ means something determined based on the image information of a plurality of pixels included in that position, for example, digital image data obtained by averaging the image information of a plurality of pixels.

In this embodiment, (jl) is set in the middle of a pixel.

In this way, the position is set, and the digital image data for each month 6 is obtained. Then, at CC Trat 10-1, one image of the names is lined up in a line in the predetermined direction. This line may be set in only one direction or in two directions.Of course, it may be set in more directions depending on the platform.

In this embodiment, lines JJ are defined in the X-axis direction and the y-axis direction, which are perpendicular to the line. That is, each position lined up in the X-axis direction (1, 1>, (2, 1), (3゜1
>, (4,1>, (5,1),...
First line X1 in direction X1, each position (1, 2>
, (2,?>, (3,2>, (A, 2
), (5, 2>, . 4 U・rnnl X4.
... or set it up again in the y ill + direction ＼) ρ7
5', each position (1, 1), (L 2>, (1
,3>, (1゜4), ...... is the first line l- in the y-axis direction, ,V 1, each a)'' month ri (2,1>,
(2,2>, (2,3>, (2,/I),
. . . is set as the second line 1-y2 in the y-axis direction, and the third line l in the y-axis direction is set in the same manner.V3.
4th line l'/4. ...... is set.

Once the lines are set in this manner, a differential process or the like is performed on each line to detect the contour points of the irradiation field on the line. The method for detecting this irradiation field contour point is not shown in Figure 1.
This will be explained by taking as an example the table for the n-th line l, . . . xn in the axial direction.

FIG. 3 is a diagram showing the size of the digital image data at each position on the line Hxn, and FIG. 1 shows the digital image data on the line 1-xn subjected to differential processing to
FIG. 3 is a diagram showing differential values at each position.

First, the digital image data on the line Lxn is subjected to differential processing to obtain the differential value δ at each position on the line.

The method of differentiation may be first-order differentiation or higher-order differentiation. Furthermore, in the case of discretely sampled images, differentiation is equivalent to finding the difference between adjacent image data. Existing in the vicinity does not necessarily mean existing adjacent to each other;
For example, if it exists every other time, it means that it includes b.

In this embodiment, −th order differentiation is performed to find the differential value δ for each position. As described above, 61 corresponds to the difference between the image data of M adjacent positions in the X-axis direction, and is expressed as in the following equation.

δ(1,n>=f (1,n) −f (2,n)δ(
2, n) = j (2, n), -f (3, n) After finding the differential value δ at each position of the [)th line l xnl- in this way, next find the absolute value of the differential value The position Δ, C, l) where is equal to or greater than a predetermined value 0 is set as the complementary point of the irradiation field contour on the line 1-xn.

Since the image data corresponds to the T-shaped magnitude of the radiation incident on the sheet, image data in the field is generally at a low level, and image data within the irradiation field is generally at a high level. becomes. Therefore, the difference (differential value) between the image data in the part where the contour of the irradiation field exists is more general than the difference (differential value) between the image data in the part A19.
The terminal level is human-friendly. Therefore, the differential value is the predetermined value 11n
It can be determined that a position where the radius is 0 or more is a point where the contour of the irradiation field exists, and as a result, that point is selected as a candidate point for the contour of the irradiation field.

However, even if it is possible to determine that a position where the differential value is greater than or equal to the predetermined value To is a point where an irradiation field contour exists, the differential value of the point where the contour exists does not necessarily exceed the predetermined value To. That is, for example, the left radiation field 1 in this embodiment
Despite the existence of a contour line such as the right side contour line 12b of 2, the image data changes slowly (see FIG. 3), and as a result, as shown in FIG.
There may be a case where the differential value of the position B does not exceed the predetermined value To even though b exists at the position.

Therefore, it is not always possible to find the contour points of the irradiation field only by performing differential processing on the image data and thresholding the differential value. Therefore, in the present invention, even in such a case, in order to avoid generating all contour points, the following processing is further performed.

First, threshold cut JQj using -F specified 1-o
contour candidate points A, ・C, I) found by lt-
The digital image data TA0c, Tv of the line LxnJ= is determined (see FIG. 3). Next, based on these image data A, TC, and TD, characteristic values Th of the digital image data A2, C, and TD are determined.

The characteristic value Th can be any long value as long as it is based on the image data TA, c, To, but for example, TA, Tc'
, To, the minimum value, average value, median value, maximum value, etc. can be used as the characteristic value. In this embodiment, TA', TC,
TA, which is the minimum value within the range, is adopted as the characteristic value Th. In this way, if the minimum value is set as the characteristic value descending, the finally detected irradiation field can be made relatively wide, and the irradiation field detected as a result of (a) becomes -b larger than the actual irradiation field.
This can reduce the risk of narrowing.

- After determining the characteristic value Th, as shown in FIG. Detected as an irradiation field contour point on the line I-Xn; a3L-j, the digital image data is detected as a point on the line I-Xn; −
, C-~1)-) is determined to be the range of the 14th field on the line I xn.

Then, the work of detecting the contour points of the field ``d'' on one line is performed for each line lx in the X-axis direction. ! Lines <7 across the area in 11 directions, connect the irradiation field outline points of each line Lx-t to form the left and right irradiation fields 1.
2.14 y-axis direction contour line 12a, 121).

Find 1'la and 14b.

Next, for any line 1-yn in the y-axis direction, the irradiation field contour point on that line route is detected in the same manner as above.
At the same time, this contour point detection is performed for each line 1 in the yhl+ direction over the entire area in the X-axis direction, and the contour members on each line lV are connected to form contour lines 12c, 12d, l/Ic, 14d in the X1111 direction.
Find these contour lines 12c, '12d, 14
c, 14d and the above contour lines 12a, '12b',
i4a, 14b (7) Recognize the inner area, that is, the range surrounded by the contour line of -tnra, as the irradiation field.

The above contour point detection can be performed for each line within a predetermined range of seas 1 to 10, -1=. That is, 1-i14
In implementation G, are you doing this for each line covering the entire range of Sea 1 to Sea 10-1-?
1, if you know to some extent (, The point detection is 1-1 and the contour line in the y-axis direction is '/WtA -, l
i-, G-,,.

After finding D-, the next y-axis 1] direction 7, in+, y
t; 2 and 1 exists within the range of 8-~B-, C-~l)-, then the line C is IJ. By reading ahead
Based only on the image information of this reference IIJJ motive factor among the image information obtained, the reading line 1'1 which is d';IJ in the main reading is determined. This reading strip a'1 contains the image information of Teruq.1 field (
For example, as mentioned above, create a stogram of the state of stimulated luminescence yf in the irradiation field, and use this histogram to determine the maximum stimulated luminescence amount SmaX. The minimum stimulated luminescence light MSmin is determined, and reading conditions can be determined based on SmaX and Sm1n.

In addition, the decision 1j5 for the reading strip II is limited to the case where the decision is reversed based only on the pre-read image information within the irradiation field. The determination can also be made by taking into consideration the copying method such as simple, contrast, tomographic, enlarged @ shadow, etc.

After determining the irradiation field as described above and determining the reading strip 1'1 for main reading based on the image information within this irradiation field, the determined reading strip 1'1 is determined. The main reading is carried out according to 1. However, this main reading (Yo, the present applicant filed the application earlier,
As disclosed in June 12034, it is preferable to limit the reading area to the determined irradiation field.

In this way, by limiting the reading area of the main reading to the irradiation source, it is possible to record in the field of irradiation of the accumulation 1 1 phosphor sheet 1,
Noise components caused by the recorded scattered radiation are not read, making it possible to obtain an excellent final image.

Furthermore, by narrowing down the reading area, it is possible to shorten the reading time or increase the reading density.

The above-mentioned embodiment is implemented only by differential processing of the image data and threshold cutting of the differential value (41 contour lines 12
This is an example of a case where the position of 1) cannot be determined, or it can be used even when all contour lines can be determined only by the present invention 1 and 11 dimensions and threshold cut J. It's Shino. In the case of the method of finding the contour line position by differentiation and threshold cut, θ, it is necessary to judge whether or not the contour line 'r: of Jpe can be detected as the neck by that method. When there is a contour line that does not exist 1
31 Perform some kind of processing to detect the rough line 91 1. 'K [-j, the algorithm required for final irradiation field detection is 4T complicated, but if the method according to the present invention J, then the initial differentiation and threshold cut will be enough. This method has the advantage that it can always automatically detect and override all contour positions, regardless of whether the contour line position has been detected or not, and the algorithm is in-process. In addition, the above fruit 711! i aspect 1.1. Even if a rectangular irradiation field is used, or an irradiation field other than a circle or a rectangle, the present invention allows recognition of the q4 field.

In addition, in the actual 1ffA mode described above, the illumination 0=+
Although we have dealt with the case where there are two fields, the present invention can also be applied to cases where there is only one field. In this case, for example, since there are only two contour lines in the y-axis direction, there may be a case where there is only one contour candidate point obtained by the threshold cut. In this case, there is only one piece of digital image data at the contour candidate point, and in that case, for example, it is possible to perform one-value processing that specifies the image data itself.

Further, in the embodiment described above, contour point detection is performed for each of the lines in the X-axis direction and the y-axis direction, but it is not necessarily necessary to perform contour point detection for lines in two directions. for example,
As shown in Figure 5 (a,), (b), if the irradiation field shape is circular or diagonal rectangular, the entire irradiation field contour is detected only by detecting contour points for each line lx in the X-axis direction. It is something that can be done.

Furthermore, in the actual embodiment described above, I set the position of the sea 1-104- pixel by pixel to obtain digital image data. For example, when it is known in advance that the irradiation field is a rectangle, Select the X-axis and y-axis along the two sides, and first set one position for every three pixels lined up in the y-axis direction, that is, position (1, 2) as shown in Figure 2 (i)). --3 pixels (・1.1) + (1,
,,2>+(1,3) Position('7.?)-=3 pixels(2,1),+(2,
2) + (2, 3 > position (1,, 5) -1 - 3 pixels (1, 4 > + (1
,5> +(j,・6) Position (2,5)−=3 pixels (2,4)+(2,5)
+(2,,6), and calculate the digital image data F at each position using the following formula, F(1,2)-1(f(1,1)+f(1) ,2) ten f(
1,3))/3 F(2,2)-1(f(2,1)+f(2,2)tenf(2,3>')/3 F(1,5)-=(f( 1,4>+f(1,5>+f
(1,6) ), /3 F (2,5) '-(f (2,4>+f (2,5)
+f(2,6))/3 This image data F is differentiated for each line in the X-axis direction to obtain the differential value δ at each position as shown in FIG. 2(C),
Using this differential value δ, the irradiation field contour line in the y-axis direction is detected using the same method as described above, and one position is then set for each of the three pixels lined up in the X-axis direction, i.e. Set each position as follows, position (2, 1) -- 3 pixels (1
, 1) + (2, 1) ten (3, 1) position (2, 21 - 3 pixels (1, 2) + (2, 2) +
(3, 2> position (5, 1)' = 3 pixels (4, 1) - 1 - (5,
D + (6,1) position (5,2)' = 3 pixels (4,2) - 1 - (5,
2> + (6, 2> Digital image data at each position [is converted to the position (1, 2
)', (2,2)'...... This image data is calculated by averaging in the same way as in the case of The irradiation field contour line in the X-axis direction may be detected using the value δ in the same manner as described above.

Setting the position in this way means preprocessing the look-ahead image information for each pixel before performing subsequent differential processing, etc. By performing this preprocessing, noise contained in the image information can be reduced. Since the influence can be eliminated and the number of image data to be processed thereafter can be reduced, the contour of the irradiation field can be detected more accurately and at high speed.

(Effects of the Invention) As described above, the method according to the present invention performs differential processing on digital image data for each line in a predetermined direction, and places the differential value at a position exceeding a predetermined value lower than 0 (J and both of the above). Obtain the image data, obtain the special value from the image data, set the position that is the same as the image data or the current '[)1 value on each line as the contour point of the irradiation field, and connect these contour points to form the contour. Find the line,
It recognizes that the area inside the contour line is the irradiation field, and determines the actual reading line (J) based on the pre-read image information within this irradiation field.

Therefore, according to the method according to the present invention, even when the irradiation field is narrowed down, the negative influence of the scattered radiation in the field in front of Sea 1 is divided by 11, and The reading conditions are determined based only on the effective image information within the irradiation field, and the reading conditions are always optimal. 1 can be determined.

In addition, the method according to the present invention (Jll, as described above, it is possible to detect the irradiation field contour that cannot be detected only by differentiation and threshold cutting, and the irradiation field The contour point extraction algorithm has the advantage of being relatively simple.

[Brief explanation of the drawing]

Figure 1 shows the stimulable phosphor sheet and the front side! Illustrated diagram of l,
Figure 2 (a) is an enlarged view of section G in Figure 1, Figure 2 (h) is a diagram showing digital image data at each position, Figure 2 (
C) is a diagram showing the differential fraction of A"3 (J) at each position. Figure 3 is a diagram showing digital image data on line 1-xn. Figure 4 is a diagram showing digital image data on line I-xn ten. Figure 5 (1-1) is a diagram showing differential values. The sheet is shown in Figure J. 10...Stormable phosphor sheet 1~12.1/l...
Front field 12a, 12t+, 12c
, 12rl, 14a, 'January),
1/+(: . 14d...Irradiation field contour point -2ε3 - r+
tJ Ritoto

Claims (2)

[Claims] (1) By irradiating the excitation light onto the stimulable phosphor sheet on which the radiation image information is stored and recorded with an irradiation field aperture, the radiation image information stored on the stimulable phosphor sheet is radiated. Prior to main reading, which is emitted as luminescent light and photoelectrically reads this stimulated luminescent light to obtain an electrical image signal for outputting a visible image, excitation with energy lower than the energy of the excitation light used in the main reading is performed. Reading the radiation image information by performing pre-reading of the radiation image information stored and recorded on the stimulable phosphor sheet using light, and determining reading conditions for the main reading based on the image information obtained by this pre-reading. In the condition determining method, digital image data at each position on the stimulable phosphor sheet is obtained from the image information obtained by the pre-reading, and one image data is set at each position on the stimulable phosphor sheet in a line in a predetermined direction. The digital image data on this line is differentiated, and the position where the absolute value of the differential value exceeds a predetermined value T_0 is set as a candidate point for the irradiation field contour on that line, and the position on the line at that candidate point is Obtain digital image data, obtain a characteristic value Th of the digital image data from the digital image data, and detect a position on the line where the digital image data has the characteristic value Th as an irradiation field contour point on the line. , detecting the irradiation field contour points for each line in a predetermined range on the stimulable phosphor sheet, and recognizing the inside of the line connecting the irradiation field contour points in each line as the irradiation field;
A method for determining reading conditions for radiation image information, characterized in that reading conditions for the main reading are determined based on image information obtained by the pre-reading within the irradiation field. (2) An x-axis and a y-axis that are orthogonal to each other are set on the stimulable phosphor sheet, and the detection of the irradiation field contour points on the lines is performed on both the x-axis direction line and the y-axis direction line. A method for determining reading conditions for radiographic image information according to claim 1, characterized in that the method is carried out for: