JPS61109550A - Processing of radiation image - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a method for recording radiation image information on a stimulable phosphor material and then scanning it with excitation light to read the radiation image information and generate a reproduced image. The present invention relates to an image processing method in a radiographic system.

(Prior Art) Radiographic images such as X#a images are often used for medical purposes. Conventionally, in order to obtain this radiographic image, a so-called radiographic method has been used in which a radiographic film made of a silver salt photosensitive material and an intensifying screen are combined. However, in recent years, with the advancement of radiographic image diagnostic technology, methods of obtaining radiographic images without using radiographic films made of silver salt photosensitive materials have been devised.

In such a method, the radiation transmitted through the object is absorbed by a certain kind of phosphor, and then this phosphor is excited by, for example, light or energy, so that the phosphor absorbs the radiation and accumulates. There is a method of emitting radiation energy as fluorescence, detecting this fluorescence and converting it into an image. Specifically, for example, British Patent No. 1,462,
No. 769 and Japanese Unexamined Patent Publication No. 51-29!389 disclose a method of using a photostimulable phosphor as the phosphor. This method uses a radiation image conversion panel in which a heat-stimulable phosphor layer is formed on a support, and the radiation transmitted through the subject is absorbed by the heat-stimulable phosphor layer of this radiation image conversion panel. A latent image is formed by multiplying radiation energy corresponding to the radiation transmittance of each part of the subject, and then the heat-stimulable phosphor layer is heated to excite it, and 'TI' is deposited on each part of the panel. The radiation energy is extracted as a light signal, and a radiation image is obtained depending on the intensity of this light.

Further, for example, US Pat. No. 3,859,527 and Japanese Patent Application Laid-Open No. 55-12144 disclose a method of using a photostimulable phosphor as the phosphor. This method uses a radiation image conversion panel in which a photostimulable phosphor layer is formed on a support. After forming a latent image as described above, this photostimulable phosphor layer is exposed to photostimulable excitation light. By scanning, the radiation energy accumulated in each part of the panel is extracted as a light signal, and a radiation image is obtained. This final image may be reproduced as a hard copy or on a CRT.
You can play it on top.

In a radiation image conversion system using a stimulable phosphor as described above, after converting radiation image information into an electrical signal, calculations are performed on the electrical signal, and spatial frequency processing, gradation processing, etc. A radiation image information processing method can be used to improve the sharpness, contrast, etc. of the reproduced image.

As one of the radiation image information processing methods, an unsharp mask signal Dus for each pixel is obtained 1, an original image signal Dorg, an unsharp mask signal Dus, and an emphasis coefficient β.
Using D = Dorg + β (Dorg - Dus), spatial frequency emphasis, so-called Etsuno emphasis, is performed,
A line image processing method for increasing the sharpness of an image is known (Japanese Patent Laid-Open No. 163472/1983).

The term "unsharp mask signal" as used herein refers to a signal of an unsharp image obtained by masking the original image so as to include only spatial frequency components lower than a specific spatial frequency.

In conventional radiation image information processing methods, a method has been adopted in which a non-sharp mask corresponding to extremely low frequencies is selected to emphasize the plantar frequency components. For example, JP-A-55-16347
In No. 2, the modulation transfer function is 0 as a non-sharp mask.
．． 0.5 or more and 0 when the spatial frequency is O1e/I
．． An image processing method using a spatial frequency of 0.5 or less at a spatial frequency of 5 c/mm is disclosed.

Furthermore, in JP-A-56-75137, a non-sharp mask has a modulation transfer function of 0.5 or more at a spatial frequency of 0.02clIIIl and 0.5 or less at a spatial frequency of 0.15c/+m. It is said that it is more preferable that

However, this image processing method that emphasizes extremely low frequency components has the following drawbacks.

For example, in an X-ray image of a bone, it is necessary for diagnosis to clearly show the minimum -t3 position of the bone, that is, the culvert.

However, since the image of the culvert has very high spatial frequency components of IC/11111 or higher, the effect of enhancement is small depending on conventional image processing methods, and no improvement in diagnostic performance can be expected.

Similarly, regarding the depiction of calcified areas in mammography, it is necessary to emphasize high spatial frequency components of 1c/lll11 or higher in order to diagnose the shape and arrangement of calcified areas. Image processing methods have little effect.

Furthermore, in plain chest images, by emphasizing ultra-low frequency components, the NFT pattern near the periphery is emphasized more than the core of the core.
This results in an unnatural image that is difficult to interpret.

In particular, when the degree of emphasis is high, the frequency processing described above actually hinders diagnosis.

Furthermore, in conventional image processing methods, a fairly wide range of frequencies above ultra-low frequencies is simultaneously emphasized, which may widen the image quality and cause white or black U missing parts to appear in the reproduced image.

(Object of the Invention) The present invention has been made in view of the shortcomings and problems described in conventional radiation image information processing methods. An object of the present invention is to provide a radiation image information processing method for obtaining images.

(Structure of the Invention) The present invention detects the radiation image information as fluorescence by scanning the stimulable phosphor material on which the radiation #i image has been recorded with excitation light, and obtains a reproduced image after photoelectrically converting the radiation image information. Original image signal ゛Dorgs Unsharp mask signal Dus obtained for each pixel Radiation image information processing method for performing spatial frequency enhancement by executing the calculation D = Dorg + β (Dorg - Dus) using the % emphasis coefficient β A radiation image information processing method is characterized in that a non-sharp mask having a modulation transfer function exceeding 0.5 for a spatial frequency of 0.5 c/s+- is used as the non-sharp mask.

In other words, the non-sharp mask according to the present invention has a spatial frequency r of 0.5e when the modulation transfer function is 0.5.
/nua is a non-sharp mask. It is obvious that the upper limit of ``in the non-sharp mask signal is smaller than that in the original image signal, but the spatial frequency m characteristic of the original image signal depends on the degree of scattering of excitation light in the stimulable phosphor material and Since it differs depending on the sampling pitch, etc., the upper limit value of ``of the non-sharp mask signal cannot be uniquely determined.

However, in order to obtain a sufficient enhancement effect, it is preferable that "r" of the unsharp mask signal is 95% or less of r of the original image signal.

In the present invention, the degree of strength or decrease of the spatial frequency is determined by the value of the emphasis coefficient β and the spatial frequency characteristics of the unsharp mask signal Dus. As a guideline to express the degree of spatial frequency emphasis, the maximum value of the modulation transfer function in the reproduced image after frequency processing and the spatial frequency 0. The ratio R to the value of the modulation transfer function at or below O1e/Rubo is used.

When the value of R is set to be greater than 1.0 and less than or equal to 3.0, an improvement in diagnostic performance is observed. In order to obtain an image that is easier to see, it is preferable that the R value be less than 5. If the R value is greater than 3.0, the image will become unnatural due to too much Ia;g, and in some cases, low-density areas may False images such as black lines appearing at the boundaries between the high-density areas and the high-density areas occur, and diagnostic performance deteriorates.

The procedure for determining the degree of spatial frequency emphasis is as follows:
First, after determining the size of the non-sharp mask, the emphasis coefficient β is set so that R takes a certain value within the above range. '
The processing effect will be different depending on whether the iin tonal coefficient β is a constant or a function of the image signal. Practically speaking, the following three settings can be considered.

1) β is constant 2) β monotonically increases as the value of the original image signal or unsharp mask signal increases 3) β increases as the value of the original image signal or unsharp mask signal increases If the degree of frequency emphasis is not very large, the method 1), in which the emphasis is applied uniformly over the entire density range, shortens the calculation time and reduces the time from 5-'y. Also, method 2) has the effect of canceling noise that appears in low density g6 when the degree of frequency emphasis is large, and is extremely useful.Noise caused by 0 frequency processing is noticeable mainly in images. Since this is a low-density part, by reducing the emphasis on this part, it is possible to obtain an image that is easy to see without "roughness."

For example, when performing spatial frequency enhancement on a plain chest image, fine granular noise may occur in low-density areas of the spine, diaphragm, and heart.

In that case, set β so that it is as small as an elbow in the concentration region corresponding to the spine, large β in the concentration region corresponding to the lung field, and β increases monotonically as the concentration increases in the middle. By performing this processing, noise is removed and an image that is easy to see and does not impair the effects of frequency processing can be obtained.

On the other hand, method 3) increases noise. Although it has some drawbacks, it is useful when the diagnostically important image area is concentrated in low-density areas.

In addition to the above-mentioned spatial frequency processing, gradation processing can be used to obtain images with higher diagnostic performance. Zero-gradation processing uses the optical density of the reproduced image on one axis of the rectangular coordinates and the xi exposure on the other axis. The gradation 'f' applied to the coordinates of the image level corresponding to the number of lights in the volume is expressed as a conversion curve, but this gradation conversion curve is defined as 4° can be considered to correspond to the characteristic curve of X-ray film. Here, the gradient of the gradation 7I4 conversion curve, that is, the slope of the straight part of the gradation conversion curve is 0.6 to 3.7 (preferably 0.6 to 3.7).
7 to 3, 5). The gradation processing may be performed before the spatial frequency processing is performed, or may be performed after the spatial frequency processing.

In the present invention, a stimulable phosphor refers to a stimulable phosphor that is stimulated optically, thermally, mechanically, chemically, or electrically (stimulated excitation) after being irradiated with high-energy radiation for the first time. ,
It refers to a phosphor that exhibits stimulated luminescence corresponding to the amount of initial light or high-energy radiation irradiation, but from a practical standpoint, it is preferably a phosphor that exhibits stimulated luminescence with an E of 5oo- or more and an Mh. A certain 0 photostimulable phosphor according to the present invention is, for example, Ba5O, :^X (where ^ is at least one of Dy+Tb and 'h, and X is 0.001≦x<1 mol%
It is. ) Phosphor expressed by JP-A-48-80488
No. Description (7) Phosphor represented by MgSO4:Ax ((El is either Ho or Dy, 0.001≦×≦1 mol, %), JP-A-48-8
5rSO described in No. 0489: ^X (However, ^
At least one of Tb, Tb, and Tm, and X
is 0. OO1≦x<1 mol%. ), Mn,
A phosphor added with at least one of Dy and VTb,
BeO,L described in JP-A No. 52-30487
Phosphors such as iF, Mg5O+ and Caf:, etc., JP-A-53
Li:B, Ot:Cu described in No.-39277
, Heg et al., LizO・(BJ2)x'', cu (where X is 2
<xs3), and Li:0 ・(820:)x:Cu,
3g (however, X is 2<xs3) ¥? phosphor, US Patent 3
, 859, 527, SrS:Ce,
Sm, SrS:Eu, S++.

La, O, S: Eu, S+ and 1/ (Zn, Cd) S:
Examples include phosphors represented by Mn and X (where X is /% Oden). In addition, the ZnS:Cu, Pb phosphor described in JP-A No. 55-12142, whose general formula is Ba
(lx^l:Os:Eu (however, 0.8≦×≦10), and the general formula is H″
O・xs:oz:^(However, Ml is Mg+Ca+5ryZ
n+Cd or Ba, and eight are Ce, Tb, Eu, Tm,
At least one of Pb, TI, Bi, and rjMn, and X satisfies 0.5≦x<2.5. ) Alkaline earth metal silicate-based phosphors represented by: Also, the general formula is (Ba, -X-yMgXCa,)FX:eEu2÷(
However, it is at least one of Xl, tBr and VCI, and X+V and e are respectively Oku\teny≦0.6, Xy≠
This is a number that satisfies the condition: 0 and 10 bows≦e≦s x to-'. ) is an alkaline earth fluorohalide phosphor represented by the general formula % formula %: f! RLLni is at least one of a, Y, Gd and Lu, X is C1 and/or Br, ^ is Ce and V/or Tb, and X is a number satisfying ()〈\<0.1. &b
) Phosphor expressed by t', JP-A-55-12145
The general formula described in the issue is ([ja, −<M”<)FX: y
^<(P is at least one of Mg, Ca, Sr, Zn and Cd, X is C1, BrhL
At least one of Vl to Eu, Tb, C
At least one of e, Tm, Dy+Pr, lIo+Nd, Yb and ZoEr, and X and y are ()≦X≦0.6
The general formula for the phosphor represented by (), which represents a number that satisfies the conditions VO≦y≦0.2, is BeFX:xCe+y^ (where X is CI, 8r At least one of the following I, 8 is In
.

T1. is at least one of Gd, 5Tll, and Zr, and each of X and y is O<x≦2 X 10-'
and o<y≦5×10−′. ), the general formula described in JP-A-55-160078 is MlFx-x^:yLn (where Ml is at least one of Mg*Ca+Sr+Zn and Cd, and χ is CI , at least one of Br and V+, ^ is BeO+ sgo, CaO+
SrO+ CaO+ ZnO, ^l, 0).

Y: Oz, La20=, Inz03vSIOztTi
OzfZrO=, CeO2゜SnO2, Nb20s-
At least one of Ta=O1 and The, Ln
are Eu, Tb, Ce, Tm, Dy, Pr, Ho+Nb+
is at least one of Yb, Er, S+Il and VCd, and each of X and TJy is 5XIO-'≦X≦0.
5 and (a number that satisfies the condition 10<y≦0.2.)
Rare earth 'fft element-activated divalent metal fluorohalide phosphor, whose general formula is ZnS:^, CdS:8, (Z
n, Cd) S: ^, SnS: ^, X and CdS: ^
,X (However, ^ is Cu, ^g, ^U or M mouth is 1),
X is Heroden. ), a phosphor represented by
7-148285t I: Record Vt 3 a Tel, %
71 general formula (1) or Ell general formula (1) xM3
(POn)z @ NX2:)'^ General formula (II)
Mz(PO<):・y^(wherein H and N are each at least one of Mg, CawSr, Ba+Zn, and ZCd, and X is F, CI, Dr.

and at least one of VI, ^ is ELI + Tb,
Cp.

7m, oil Pry)low Ndt Yb
+ Er, Sb + Tl + Mnn represents at least one of Sn, and X and y are 0 <X≦6, O
It is the number that forms the row f'L (≦y≦1). ), and the general formula [1ll) or [■] General formula (m ) nReX, ・m^X2': xEu
General formula (IV) nReX3・m^X2' :xE
u+ySm (where Re is La, (:d, Y, L
At least one of u, ^ is an alkaline earth metal, B
a, at least one of Srt Ca, X and VX
' represents at least one of F, C1, and Br;
l0-'11 Xl0- ''<y< I Xl0-'
It is a number that satisfies the condition that n/+n is 1×10−co<
n7m < 7 X 10-' ) and the following general formula % formula %: (However, Ml is Li, Na, K, Rb and C
At least one alkali metal selected from s,
Ml is 8e, Mg, Ca, Sr, Ba, 2n
, Cd, Cu, and Ni. Ml is Se.

Yv Lap Cet Prt Ndv Pm, SI
@y Eut (:de Tbv D)'+)foe
At least one trivalent metal selected from Er, T1Yb, Lu, ^l, Ga, and In.

X+X'#! I /

Ce, Tm, Dye l'r+ Hot Nd,
Yb, Er, Gd, Lu+ S1Y, TI,
It is at least one metal selected from Na, 8g, Cu, and Mg. Further, a is a numerical value in the range of O≦a<0.5, bl, tO≦b<0.5, and C is a numerical value in the range of Ode≦0.2. ) and Mugi Sushiro phosphor. However, the stimulable phosphor according to the present invention is not limited to the above-mentioned phosphors, but can be any phosphor that exhibits stimulated luminescence when irradiated with radiation and then irradiated with exhaustion excitation. It may be the body.

Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 schematically shows a radiation image conversion system that is an embodiment of the present invention.

When the radiation transmitted through the subject 2 is absorbed by the stimulable phosphor material 3, the stimulable phosphor material 3 accumulates radiation energy and forms a latent image. By scanning this stimulable phosphor material with the stimulable excitation light from the stimulable excitation light source 4,
Photoelectric conversion of accumulated radiation energy as fluorescence 55
and convert it into an electrical signal. The electric signal is amplified, A/D converted, converted into a digital signal, and stored in the arithmetic unit 6, which produces an unsharp mask signal D u
After determining *, the calculation D” Dorg+β(Dorg Dus) is executed.

The digital signal may be temporarily recorded on a recording material such as a magnetic tape or an optical disk, and then read out to a calculation device to perform calculations.

Here, the method for obtaining the unsharp mask signal is as follows: 1) Read out a certain number of image signals in the peripheral areas along with the original image signal, and calculate their average value or weighted average value to obtain the unsharp mask signal.

2) After reading out the original image signal, the remaining radiation image information is read and converted into a non-sharp mask signal by scanning it with excitation light having a large beam diameter.

3) When reading the original image signal, simultaneously observe the light emission on the transmission source side of the excitation light, and use this as a non-sharp mask signal.

The following methods are used.

In the present invention, method 1) in which a non-sharp mask signal can be obtained using only dinotal calculations is the most advantageous from the viewpoint of simplifying the apparatus and shortening the calculation time.

The unsharp mask signal Dus obtained as described above, the original image signal D org, and the ? Using a harmonic coefficient β, D:Dorg+β(
The following calculation is performed: DorFl-Dus).

Here, as the non-sharp mask, a non-sharp mask whose modulation transfer function exceeds 0.5 for a spatial frequency of 0.5 c/m is used.

Figure m2 shows an example of spatial frequency processing in the present invention.

In Figure 52, the solid line a indicates the spatial frequency a characteristic of the original image signal Dorg read from the stimulable phosphor material at a sampling pitch of 100-.

Also, in Figure 2 (1), the dotted line represents 10 pixels x 10 pixels.
The frequency characteristics of the unsharp mask signal Dus obtained as the average value of the image signal in a rectangular area of 111i elements are shown.

This is 1.0 mm x 1. This is equivalent to that obtained by scanning with a beam of magnitude Os-.

FIG. 2(2) shows the 1g transfer function of (D org -Dus).

In FIG. 2(3), the actual jQa is β;2. o again. α
Rb represents the signal after spatial frequency processing when the calculation is performed with β=0.6.

As mentioned above, the value of the emphasis coefficient β may be constant, or in some cases, it may be effective to set it to vary depending on the original image signal or the unsharp mask signal.

The final processed image may be reproduced on a recording material such as an X-ray photographic film or on a CR'.

Fruit/male side 1 A simple chest image was recorded on a stimulable phosphor material by the method of the present invention, and this was recorded at a sampling pitch of 100JjlC.
h was read and used as an original image. The original image was subjected to nine types of spatial frequency processing as described below, in which the spatial frequency components to be emphasized and the degree of V emphasis were varied.

(la) r-0,52c/am (lb) r-0,52
c/ms (lc)rao, 52c/+mR-5. OR
-2,5R-1,4 (2a) r-0,71c/mm (2b) r=o, 7
1c/mm (2c) f=o, 71e/+*mR wealth 5
．． OR-2,58-1,4 (3a) f=o,! 36c/m+* (3b) f-0,
S6c/Iam (3c) f-0, S6c/amR-5
, OR=2,5 R=1.4 Here, f is the spatial frequency at which the modulation transfer function of the unsharp mask signal is 0.5, and R is the maximum value of the modulation transfer function after spatial frequency processing and the spatial frequency. 0. Modulation transfer rt in O1c/mm1c
Represents the ratio of J number values.

The image subjected to the spatial frequency processing was subjected to appropriate gradation processing and then reproduced on an X-ray film. Evaluations of the diagnostic performance of these reconstructed images were conducted by three radiologists and one radiologist.
! We asked a total of 14 people named riiG.

The evaluator considers the reproduced image to be an image processed by a conventional image processing method, that is, (1) and (2) in Comparative Example 1, which will be described later.
) and its fA were compared and evaluated according to the following criteria.

Diagnostic performance is superior to the comparative example: ◎ Slightly superior: ○ Equivalent: Δ Inferior: × What are the evaluation results? The numbers in Table 1 shown in tSl& are the evaluation numbers ◎, ○, Δ, and ×, respectively.
The reason for giving a rating of b or Q is that the fine lung core is clearly expressed. It is excellent for depicting the aortic shadow (the aortic shadow) and the aortic shadow. Points such as the fact that the hunt trust is appropriate and that "white areas" do not appear are cited.

As is clear from Table 1, the image processing method of the present invention was able to obtain plain chest images with higher diagnostic performance than conventional methods. Also, the degree of emphasis is higher when R=2.5 than when R=5.0, and when R=2.5.
Compared to the case where R=1.4, the image was evaluated to be more natural and closer to the image obtained by ordinary radiography, and the sharpness was sufficiently high.

Comparative Example 1 For the same image as the original image used in Example 1,
Spatial frequency processing for two scales was performed as follows.

(1) f=o, 03c/m+* (2) f
= o, lc/mm1 (-5, OR = 5.0 After performing gradation processing on the image subjected to the spatial frequency processing using the same gradation conversion curve as used in Example 1,
Reproduced on XR film.

(Example 2) An image of the femur (including muscles) was
The image was recorded on an iE-based phosphor material, and read at a sampling pitch of 100 to obtain an original image.

The following nine types of spatial frequency processing were performed on the original image by varying the spatial frequency components to be emphasized and the degree of 1 emphasis.

(4a) f-0,5Sc/mn (4b) f-0,58
c/mm (4c)f-0,5Sc,'lemR=5
．． OR=2.5 R=1.4(5a)r-
0,76c/1(5b)r-0,76c/m+n (5
c) r-0,76c/amR=5. OR=2,5
R= 1.4(6a)r-1,lc/+m
(6b) r-], 1c/+nl11 (6c) f-1,1
c7+nmR=5. OR= 2.5 R=
1.4 After performing appropriate gradation processing on the image subjected to spatial frequency processing, it was reproduced on X-ray film. A total of 14 people, 8 radiologists and 6 radiographers, were asked to evaluate the diagnostic performance of these reproduced images. The evaluator compares the reproduced image with the processed F1 image obtained by the conventional image processing method, that is, the two images (3) and V (4) in Comparative Example 2, which will be described later, and uses the same evaluation criteria as in Example 1. The evaluation was carried out by The results of the evaluation are shown in Table 2.

Table 2 Note that the reason for giving a rating of ◎ or ○ is that, as is clear from Table 2, the image processing method of the present invention produces femur images with higher diagnostic performance than conventional methods. I was able to get it. Also, the degree of emphasis is usually higher when R = 2.5 than when R = 5.0, and when R = 1.4 than when R = 2.5. The images were rated as natural, close to those obtained using traditional radiography, and with sufficiently high sharpness.

Comparative Example 2 For the same image as the original image used in Example 2,
28 like below! Seki's spatial frequency processing was performed.

(3) f=0.05c/mo+ (4N=0,2
c/■R=5. OR=5.0 The image subjected to the spatial frequency processing was subjected to gradation processing using the same gradation conversion curve used in (Example 2), and then reproduced on an X-ray film.

(Example 3) A mammography having a calcified area was recorded on a photostimulated °1 phosphor material using the method of the present invention, and this was sampled and read at a border of 100 m T to obtain an original image. The following nine types of spatial frequency processing were performed on the original image by varying the spatial frequency components to be emphasized and the degree of emphasis.

(7a) f', o, 58c/mm (7b) f・o, 5
8c/ms (7e)r□o, 58c/mmR=5.
OR = 2.5 R = 1.4 (8a) f30
．． 86c/am (8b) f-0, 86c/+mm
(8c) f>0, 86c/mwR=5. OR=2
．． S R = 1.4 (9a) f'l, 3c/m
m (91)H:1,3c/am (9c)f:1
．． 3e/knowledge mR=5. OR= 2.5 R=
1.4 The image subjected to the spatial frequency processing was subjected to appropriate gradation processing, and then reproduced on X#a film. We asked a total of 14 people, 8 radiologists and 6 radiographers, to evaluate the diagnostic performance of these reconstructed images. The evaluator compared the reproduced image with images processed by the conventional image processing method, that is, two images (5) and (6) in Comparative Example 3, which will be described later, and made an evaluation using the same evaluation criteria as in Example. went. Evaluation Results Table 3 The reasons for giving a rating of ◎ or O include that the calcified image is clearly depicted, and that the shape and arrangement of the calcified part is easy to diagnose. ing.

As is clear from the third barley, the image processing method of the present invention was able to obtain mammography with higher diagnostic performance than conventional methods. Also, the degree of emphasis is higher when R=2.5 than when R=5.0, and when R=2.5.
Compared to the case where R=1.4 was set, the image was evaluated to be more natural and closer to that obtained by ordinary radiography, and the sharpness was sufficiently high.

Comparative Example 3 For the same image as the original image used in Example 3,
Two types of spatial frequency processing were performed as follows.

(5) f = 00lc/ram (6) f =
0.3c/+mR=5. OR=5.0 After performing gradation processing on the image subjected to the intermediate frequency processing using the same gradation conversion curve as used in Example 3,
Reproduced on X-ray film.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a radiation image conversion system that is an embodiment of the present invention, and FIG. 2 (1), (2), and (3) are graphs showing the process of spatial frequency processing. 1... Radiation generator 2... Subject 3... Stimulable phosphor material 4... Stimulable excitation light source 5... Photoelectric converter 6... Arithmetic device 7... Radiation image Reproduction device agent Patent attorney No 1) Parent-in-law 1: 1 fold of school seven! 2: v5. ＄I book 3: Hunfuyusei 4mura rihan 4: Keyaki ~ growling brother 5: L electric chisel video answer 6: 5F ear split 7: Radiant rod Wataru image reproduction'' Figure 2 7 Mazono Noizu ( c/mm) Spatial MyL teaching (c/mm) Muroma Gokin & (c/mm) Procedural amendment Yoshi April 5, 1985 1, Indication of the case 1982 Patent M No. 233931 2, Invention Name: Radiographic image information processing method 3, relationship with the person making the amendment Patent applicant address: Konishiroku Photo Industry Co., Ltd., 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 1-1 Sakuracho, Hino-shi, Tokyo 191 Japan (Telephone number) 0425-83-15
21) Patent Department 5 amends the drawing to be amended, Figure 6, and the content of the amendment, Figure 2, as shown in the attached sheet. Figure 2 Spatial Darkness Number, (c/mm) Ashishu Nami (c/mm) Procedural Amendment February 3, 1986

Claims (7)

[Claims] (1) The radiation image information is detected as fluorescence by scanning the stimulable phosphor material on which the radiation image has been recorded with excitation light, and in order to obtain the reproduced image after photoelectric conversion, the original image signal Dorg and each pixel are In a radiation image information processing method in which spatial frequency enhancement is performed by executing the calculation D=Dorg+β(Dorg-Dus) using the unsharp mask signal Dus and the emphasis coefficient β obtained for the unsharp mask, the unsharp mask is 0.5c/ mm
A radiation image processing method characterized in that a non-sharp mask having a modulation transfer function exceeding 0.5 is used for a spatial frequency of . (2) Claim 1, characterized in that the maximum value of the modulation transfer function after frequency processing is 3.0 times or less the value of the modulation transfer function at a spatial frequency of 0.01 c/mm or less. radiographic image processing method. (3) The maximum value of the modulation transfer function after frequency processing is 1.
The radiation image processing method according to claim 1, wherein the radiation image processing method is less than 5 times. (4) The radiation image processing method according to any one of claims 1 to 3, wherein the emphasis coefficient β is a constant. (5) The enhancement coefficient β monotonically increases as the value of the original image signal Dorg or the unsharp mask signal Dus increases. Radiographic image processing method. (6) The enhancement coefficient β has a portion that decreases as the original image signal Dorg or the unsharp mask signal Dus increases. Radiographic image processing method. (7) In addition to spatial frequency enhancement processing, perform gradation processing such that the gamma of the gradation conversion curve representing the relationship between the optical density of the reproduced image and the logarithm of the X-ray exposure amount is 0.6 to 3.7. A radiation image processing method according to any one of claims 1 to 6, characterized in that: