Apparatus for determining an image position on imaging media

An apparatus for determining an image position obtains an image signal representing the whole image, which has been recorded approximately over the whole area of a recording medium, by carrying out an image read-out operation from approximately the whole area of the recording medium, at part of which an object image has been recorded. The position of the object image on the recording medium is determined on the basis of the image signal. A certainty operation device is provided to calculate the degrees of certainty, which indicate step-wise the levels of probability that the object image will be present in partial regions on said recording medium. The degree of certainty is calculated for each of the partial regions on the recording medium, in which partial regions the object image is expected as being recorded. A position determining device is provided to determine the position of the object image on the recording medium on the basis of a plurality of the degrees of certainty, which have been calculated for the respective partial regions on the recording medium.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an apparatus for determining an image position, 
wherein the position of a desired object image on a recording medium is 
determined on the basis of an image signal, which has been detected from 
approximately the whole surface of the recording medium and which 
represents the whole image recorded on approximately the whole surface of 
the recording medium. The desired object image having been recorded at on 
a portion the recording medium. This invention also relates to a method 
for adjusting read-out conditions and/or image processing conditions for a 
radiation image, wherein read-out conditions for a final readout and/or 
image processing conditions are adjusted on the basis of an image signal 
representing a radiation image in which a desired object image is 
embedded. 
2. Description of the Prior Art 
Techniques for reading out a recorded radiation image in order to obtain an 
image signal, carrying out appropriate image processing on the image 
signal, and then reproducing a visible image by use of the processed image 
signal have heretofore been known in various fields. For example, as 
disclosed in Japanese Patent Publication No. 61(1986)-5193, an X-ray image 
is recorded on an X-ray film having a small gamma value chosen according 
to the type of image processing to be carried out. The X-ray image is read 
out from the X-ray film and converted into an electric signal (image 
signal), and the image signal is processed and then used for reproducing 
the X-ray image as a visible image on a photocopy, or the like. In this 
manner, a visible image having good image quality with high contrast, high 
sharpness, high graininess, or the like can be reproduced. 
Also, when certain kinds of phosphors are exposed to radiation such as 
X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or 
ultraviolet rays, they store part of the energy of the radiation. Then, 
when the phosphor which has been exposed to the radiation is exposed to 
stimulating rays such as visible light, light is emitted by the phosphor 
in proportion to the amount of energy stored thereon during its exposure 
to the radiation. A phosphor exhibiting such properties is referred to as 
a stimulable phosphor. 
As disclosed in Japanese Unexamined Patent Publication Nos. 55(1980)-12429, 
56(1981)-11395, 55(1980)-163472, 56(1981)-104645, and 55(1980)-116340, it 
has been proposed to use stimulable phosphors in radiation image recording 
and reproducing systems. Specifically, a sheet provided with a layer of 
the stimulable phosphor (hereinafter referred to as a stimulable phosphor 
sheet) is first exposed to radiation which has passed through an object, 
such as the human body. A radiation image of the object is thereby stored 
on the stimulable phosphor sheet. The stimulable phosphor sheet is then 
scanned with stimulating rays, such as a laser beam, which cause it to 
emit light in proportion to the amount of energy stored thereon during its 
exposure to the radiation. The light emitted by the stimulable phosphor 
sheet, upon stimulation thereof, is photoelectrically detected and 
converted into an electric image signal. The image signal is then used 
during the reproduction of the radiation image of the object as a visible 
image on a recording material such as photographic film, or on a display 
device such as a cathode ray tube (CRT) display device, or the like. 
Radiation image recording and reproducing systems which use stimulable 
phosphor sheets are advantageous over conventional radiography using 
silver halide photographic materials, in that images can be recorded even 
when the energy intensity of the radiation to which the stimulable 
phosphor sheet is exposed varies over a wide range. More specifically, 
since the amount of light which the stimulable phosphor sheet emits when 
being stimulated varies over a wide range and is proportional to the 
amount of energy stored thereon during its exposure to the radiation, it 
is possible to obtain an image having a desirable density regardless of 
the energy intensity of the radiation to which the stimulable phosphor 
sheet was exposed. In order to obtain the desired image density, an 
appropriate read-out gain is set when the emitted light is being detected 
and converted into an electric signal to be used in the reproduction of a 
visible image on a recording material, such as photographic film, or on a 
display device, such as a CRT display device. 
In order for an image signal to be detected accurately, certain factors 
which affect the image signal must be set in accordance with the dose of 
radiation delivered to the stimulable phosphor sheet and the like. Novel 
radiation image recording and reproducing systems which accurately detect 
an image signal have been proposed in, for example, Japanese Unexamined 
Patent Publication Nos. 58(1983)-67240, 58(1983)-67241, and 
58(1983)-67242. The proposed radiation image recording and reproducing 
systems are constituted such that a preliminary read-out operation 
(hereinafter simply referred to as the "preliminary readout") is carried 
out in order to approximately ascertain the radiation image stored on the 
stimulable phosphor sheet. In the preliminary readout, the stimulable 
phosphor sheet is scanned with a light beam having a comparatively low 
energy level, and a preliminary read-out image signal obtained during the 
preliminary readout is analyzed. Thereafter, a final read-out operation 
(hereinafter simply referred to as the "final readout") is carried out to 
obtain the image signal, which is to be used during the reproduction of a 
visible image. In the final readout, the stimulable phosphor sheet is 
scanned with a light beam having an energy level higher than the energy 
level of the light beam used in the preliminary readout, and the radiation 
image is read out with the factors affecting the image signal adjusted to 
appropriate values on the basis of the results of an analysis of the 
preliminary read-out image signal. 
The term "read-out conditions" as used hereinafter means a group of various 
factors, which are adjustable and which affect the relationship between 
the amount of light emitted by the stimulable phosphor sheet during image 
readout and the output of a read-out means. For example, the term 
"read-out conditions" may refer to a read-out gain and a scale factor 
which define the relationship between the input to the read-out means and 
the output therefrom, or to the power of the stimulating rays used when 
the radiation image is read out. 
The term "energy level of a light beam" as used herein means the level of 
energy of the light beam to which the stimulable phosphor sheet is exposed 
per unit area. In cases where the energy of the light emitted by the 
stimulable phosphor sheet depends on the wavelength of the irradiated 
light beam, i.e. the sensitivity of the stimulable phosphor sheet to the 
irradiated light beam depends upon the wavelength of the irradiated light 
beam, the term "energy level of a light beam" means the weighted energy 
level which is calculated by weighting the energy level of the light beam, 
to which the stimulable phosphor sheet is exposed per unit area, with the 
sensitivity of the stimulable phosphor sheet to the wavelength. In order 
to change the energy level of a light beam, light beams of different 
wavelengths may be used, the intensity of the light beam produced by a 
laser beam source or the like may be changed, or the intensity of the 
light beam may be changed by moving an ND filter or the like into and out 
of the optical path of the light beam. Alternatively, the diameter of the 
light beam may be changed in order to alter the scanning density, or the 
speed at which the stimulable phosphor sheet is scanned with the light 
beam may be changed. 
Regardless of whether the preliminary readout is or is not carried out, it 
has also been proposed to analyze the image signal (including the 
preliminary readout image signal) obtained and to adjust the image 
processing conditions, which are to be used when the image signal is 
processed, on the basis of the results of an analysis of the image signal. 
The term "image processing conditions" as used herein means a group of 
various factors, which are adjustable and set when an image signal is 
subjected to processing, which affect the gradation, sensitivity, or the 
like, of a visible image reproduced from the image signal. The proposed 
method is applicable to cases where an image signal is obtained from a 
radiation image recorded on a recording medium such as conventional X-ray 
film, as well as to systems using stimulable phosphor sheets. 
In the course of recording a radiation image of an object on a recording 
medium, it is often desirable for portions of the object not related to a 
diagnosis, or the like, to be prevented from being exposed to radiation. 
Also, when the object portions not related to a diagnosis, or the like, 
are exposed to radiation, the radiation is scattered by such portions to 
the portion that is related to a diagnosis, or the like, and the image 
quality is adversely affected by the scattered radiation. Therefore, when 
a radiation image of an object is recorded on the recording medium, an 
irradiation field stop is often used to limit the irradiation field to an 
area smaller than the overall recording region of the recording medium so 
that radiation is irradiated only to that portion of the object, which is 
to be viewed, and part of the recording medium (i.e. the region inside of 
the irradiation field). The region inside of the irradiation field is 
often composed of an object image region, in which the image of the object 
is recorded, and a background region, upon which the radiation impinged 
directly without passing through the object. Of these regions on the 
recording medium, the region which it is necessary to reproduce is only 
the object image region. Therefore, when a visible image is to be 
reproduced from an image signal representing a radiation image, the shape 
and location of the object image region in the radiation image, which has 
been recorded over the whole area of the recording medium, should be 
determined, and image signal components corresponding to the object image 
region should be determined from the image signal. Appropriate read-out 
conditions for the final readout and/or appropriate image processing 
conditions should then be adjusted on the basis of the image signal 
components, which have thus been determined. In this manner, a visible 
reproduced image can be obtained which has good image quality and can 
serve as an effective tool in, particularly, the efficient and accurate 
diagnosis of an illness. When the shape and location of the object image 
region are determined, characteristics of the radiation image depending on 
the structure of an image recording apparatus used to record the radiation 
image of the object, or the like, and the shape of the object are often 
taken into consideration. By way of example, a method for determining the 
position of an object image region in an X-ray image of the mamma of a 
human body is disclosed in Japanese Unexamined Patent Publication No. 
61(1986)-170178. With the disclosed method, a change in the value of an 
image signal at the boundary between an object image region (i.e. a mamma 
pattern) and a background region is detected by utilizing such 
characteristics that the mamma pattern is recorded in an approximately 
semicircular shape on a recording medium and the background region is 
located outward from the circular arc, which defines the boundary of the 
approximately semicircular mamma pattern. 
However, the methods described above are based on the assumption that the 
relationship between the position of the contour of an irradiation field 
and the position of an object image region in the region inside of the 
irradiation field, or the like, coincides with a predetermined condition. 
Specifically, based on such assumption, operations are carried out on an 
image signal in order to find whether each of a plurality of partial 
regions on the recording medium, which are expected as falling within the 
region inside of the irradiation field, falls or does not fall within the 
region inside of the irradiation field. Therefore, it often occurs that 
the shape and location of the object image region cannot be determined by 
taking the shape of the object, or the like, into consideration. Such 
problems occur when the relationship between the position of the 
irradiation stop and the position of the object differs slightly from the 
predetermined relationship or when patterns of characters formed of lead 
having a low radiation transmittance are recorded together with the object 
image on a recording medium. If the shape and location of the object image 
region cannot be determined, the read-out conditions for the final readout 
and/or the image processing conditions, which are appropriate for the 
object image region, cannot be determined. In such cases, for example, the 
read-out conditions for the final readout and/or the image processing 
conditions are determined on the basis of the image signal detected from 
the entire area of the recording medium, including the region outside of 
the irradiation field, which region was exposed to little radiation. 
Specifically, the read-out conditions for the final readout and/or the 
image processing conditions are determined such that the whole radiation 
image may have comparatively good image quality in a reproduced visible 
image. As a result, a reproduced visible image is obtained wherein the 
image density of the object image region is markedly high (or the 
luminance of the object image region is markedly low when the reproduced 
image is displayed on a CRT display device, or the like). Such a 
reproduced image is not suitable for the viewing purposes. 
SUMMARY OF THE INVENTION 
The primary object of the present invention is to provide an apparatus for 
determining an image position, wherein the position of a specific image on 
a recording medium is determined accurately on the basis of an image 
signal detected from the recording medium. 
Another object of the present invention is to provide a method for 
adjusting read-out conditions and/or image processing conditions for a 
radiation image, wherein a probability density function of an image signal 
is obtained, the pattern of which probability density function is not very 
different from a standard pattern, and wherein appropriate read-out 
conditions for a final readout and/or appropriate image processing 
conditions are determined accurately on the basis of the results of an 
analysis of the probability density function. 
The specific object of the present invention is to provide a method for 
adjusting read-out conditions and/or image processing conditions for a 
mamma radiation image including a chest wall pattern, wherein a mamma 
pattern and a retro-mamma space (i.e. the boundary region between the 
mamma pattern and a chest wall pattern in a mamma radiation image 
including a chest wall pattern) are detected as a region of interest from 
the mamma radiation image including a chest wall pattern, and wherein the 
read-out conditions for a final readout and/or the image processing 
conditions are determined on the basis of image signal components of the 
image signal, which correspond to the region of interest. 
The present invention provides an apparatus for determining an image 
position, wherein an image signal representing the whole image, which has 
been recorded approximately over the whole area of a recording medium, is 
obtained by carrying out an image read-out operation from approximately 
the whole area of the recording medium, at part of which an object image 
has been recorded, and wherein the position of the object image on the 
recording medium is determined on the basis of the image signal. 
The apparatus for determining an image position has the following: 
i) a certainty operation means for calculating the degrees of certainty, 
which indicate step-wise the levels of probability that said object image 
will be present in partial regions on said recording medium, the degree of 
certainty being calculated for each of the partial regions on said 
recording medium, in which partial regions said object image is expected 
as being recorded, and 
ii) a position determining means for determining the position of said 
object image on said recording medium on the basis of a plurality of the 
degrees of certainty, which have been calculated for the respective 
partial regions on the recording medium. 
Heretofore, the presence or absence of an object image in each of partial 
regions, in which an object image is expected as being recorded, has been 
determined on the basis of only the results of an analysis of each partial 
region. Therefore, if the analysis of each partial region, in which an 
object image has been recorded, is carried out inaccurately, the presence 
or absence of the object image in each partial region cannot be 
determined. 
The apparatus for determining an image position in accordance with the 
present invention is provided with the certainty operation means for 
calculating the degrees of certainty, which indicate step-wise the levels 
of probability that the object image will be present in partial regions on 
the recording medium. The degree of certainty is calculated for each of 
the partial regions on the recording medium, in which partial regions the 
object image is expected as being recorded. The apparatus for determining 
an image position in accordance with the present invention is also 
provided with the position determining means for determining the position 
of the object image on the recording medium on the basis of a plurality of 
the degrees of certainty, which have been calculated for the respective 
partial regions on the recording medium. Therefore, with the apparatus for 
determining an image position in accordance with the present invention, 
even if, for example, the shape and the position of the object image are 
slightly different from a predetermined shape and a predetermined 
position, the degrees of certainty, which have been calculated for the 
respective partial regions on the recording medium, can be compared with 
each other. Thereafter, it is found that the object image is present in 
the partial region, which is associated with the highest degree of 
certainty. Accordingly, the position, at which the object image has been 
recorded, can be determined more accurately than with the conventional 
techniques. 
The present invention also provides a first apparatus for determining a 
mamma image position, which has the following: 
i) a prospective object image region finding means for: 
obtaining an image signal made up of a series of image signal components 
representing a radiation image of an object, which radiation image has 
been recorded on a recording medium and is composed of: 
a) a single object image region or a plurality of object image regions, in 
each of which a mamma pattern has been recorded such that it may project 
in an approximately semicircular shape from an edge of said recording 
medium toward the middle of the recording medium, the mamma pattern having 
been recorded by irradiating radiation, which has passed through a mamma, 
to the recording medium, 
b) a background region, which surrounds the approximately semicircular edge 
of each the object image region, and upon which the radiation impinged 
directly without passing through the object, and 
c) a scattered radiation image region, which is adjacent to the background 
region, and upon which scattered radiation impinged, 
detecting a change in the image signal at the approximately semicircular 
edge of each the object image region on the basis of said image signal, 
and 
thereby finding a single prospective object image region or a plurality of 
prospective object image regions, and 
ii) a position determining means for judging the correctness or 
incorrectness of each the prospective object image region on the basis of 
a mean-level value of the values of the image signal components 
corresponding to each said prospective object image region, and thereby 
determining the position of each the object image region in the radiation 
image. 
The term "mean-level value" as used herein means one of various types of 
values which represent the mean level of the values of the image signal 
components of the image signal. For example, the mean-level value may be 
the arithmetical mean, the geometric mean, or the median value of the 
values of the image signal components of the image signal. Alternatively, 
the mean-level value may be calculated with the formula expressed as 
(maximum value-minimum value)/2. 
The present invention further provides a second apparatus for determining a 
mamma image position, which has the following: 
i) a prospective object image region finding means for: 
obtaining an image signal made up of a series of image signal components 
representing a radiation image of an object, which radiation image has 
been recorded on a recording medium and is composed of: 
a) a single object image region or a plurality of object image regions, in 
each of which a mamma pattern has been recorded such that it may project 
in an approximately semicircular shape from an edge of the recording 
medium toward the middle of the recording medium, the mamma pattern having 
been recorded by irradiating radiation, which has passed through a mamma, 
to the recording medium, 
b) a background region, which surrounds the approximately semicircular edge 
of each the object image region, and upon which the radiation impinged 
directly without passing through the object, and 
c) a scattered radiation image region, which is adjacent to the background 
region, and upon which scattered radiation impinged, 
detecting a change in the image signal at the approximately semicircular 
edge of each the object image region on the basis of said image signal, 
and 
thereby finding a single prospective object image region or a plurality of 
prospective object image regions, and 
ii) a position determining means for judging the correctness or 
incorrectness of each the prospective object image region on the basis of 
the geometric form of each the prospective object image region, and 
thereby determining the position of each the object image region in said 
radiation image. 
The first and second apparatuses for determining a mamma image position in 
accordance with the present invention process a radiation image of an 
object, which radiation image has been recorded on a recording medium and 
is composed of: 
a) a single object image region or a plurality of object image regions, in 
each of which a mamma pattern has been recorded such that it may project 
in an approximately semicircular shape from an edge of the recording 
medium toward the middle of the recording medium, the mamma pattern having 
been recorded by irradiating radiation, which has passed through a mamma, 
to the recording medium, 
b) a background region, which surrounds the approximately semicircular edge 
of each object image region, and upon which the radiation impinged 
directly without passing through the object, and 
c) a scattered radiation image region, which is adjacent to the background 
region, and upon which scattered radiation impinged. 
With the first apparatus for determining a mamma image position in 
accordance with the present invention, the position of the object image 
region is determined accurately on the basis of the findings that the 
amount of radiation to which the recording medium is exposed varies for 
the object image region and the scattered radiation image region. 
Specifically, with the first apparatus for determining a mamma image 
position in accordance with the present invention, a change in the image 
signal at the approximately semicircular edge of each object image region 
is detected on the basis of the image signal representing the radiation 
image, and a single prospective object image region or a plurality of 
prospective object image regions are thereby found. For this purpose, the 
method disclosed in Japanese Unexamined Patent Publication No. 
61(1986)-170178 or the method described in an embodiment of the first 
apparatus for determining a mamma image position in accordance with the 
present invention, which will be described later, may be employed. 
Thereafter, a judgment is made as to the correctness or incorrectness of 
each prospective object image region on the basis of the mean-level value 
of the values of the image signal components corresponding to each 
prospective object image region. Therefore, the position of the object 
image region in the radiation image can be determined accurately. 
The position of the object image region can also be determined accurately 
on the basis of the findings that the object image region has an 
approximately semicircular shape. With the second apparatus for 
determining a mamma image position in accordance with the present 
invention, a single prospective object image region or a plurality of 
prospective object image regions are found in the same manner as that in 
the first apparatus for determining a mamma image position in accordance 
with the present invention. Thereafter, a judgment is made as to the 
correctness or incorrectness of each prospective object image region on 
the basis of the geometric form of each prospective object image region. 
Therefore, as in the first apparatus for determining a mamma image 
position in accordance with the present invention, the position of the 
object image region in the radiation image can be determined accurately. 
A method for adjusting read-out conditions and/or image processing 
conditions for a radiation image in accordance with the present invention 
is applied when a stimulable phosphor sheet is utilized and a preliminary 
readout is carried out. 
Specifically, the present invention still further provides a method for 
adjusting read-out conditions and/or image processing conditions for a 
radiation image, wherein a first image signal made up of a series of image 
signal components representing a radiation image, in which an object image 
is embedded at part, is obtained by exposing a stimulable phosphor sheet, 
on which the radiation image has been stored, to stimulating rays, which 
cause the stimulable phosphor sheet to emit light in proportion to the 
amount of energy stored thereon during its exposure to radiation, the 
emitted light being detected, 
a second image signal representing the radiation image is thereafter 
obtained by again exposing the stimulable phosphor sheet to stimulating 
rays, the light emitted by the stimulable phosphor sheet being detected, 
and 
read-out conditions, under which the second image signal is to be obtained, 
and/or image processing conditions, under which the second image signal 
having been obtained is to be image processed, are adjusted on the basis 
of the first image signal, 
the method for adjusting read-out conditions and/or image processing 
conditions for a radiation image includes the steps of: 
i) detecting a change in the first image signal at an edge of the object 
image, 
ii) thereby finding a plurality of points, which are spaced apart from each 
other and located at positions in the vicinity of the edge of the object 
image, said positions being slightly spaced apart from the object image, 
iii) creating a probability density function of the image signal components 
of the first image signal corresponding to a region, which is surrounded 
by lines connecting the plurality of the thus found points and which 
approximately corresponds to the object image, and 
iv) adjusting the read-out conditions and/or the image processing 
conditions on the basis of the results of an analysis of the probability 
density function. 
A method for adjusting image processing conditions for a radiation image in 
accordance with the present invention is applied when a recording medium, 
such as a stimulable phosphor sheet or X-ray film, is utilized. 
Specifically, the present invention also provides a method for adjusting 
image processing conditions for a radiation image, wherein image 
processing conditions, under which an image signal is to be image 
processed, are adjusted on the basis of the image signal made up of a 
series of image signal components representing a radiation image, in which 
an object image is embedded at part, 
the method for adjusting image processing conditions for a radiation image 
includes the steps of: 
i) detecting a change in the image signal at an edge of said object image, 
ii) thereby finding a plurality of points, which are spaced apart from each 
other and located at positions in the vicinity of the edge of the object 
image, the positions being slightly spaced apart from the object image, 
iii) creating a probability density function of the image signal components 
of the image signal corresponding to a region, which is surrounded by 
lines connecting the plurality of the thus found points and which 
approximately corresponds to the object image, and 
iv) adjusting the image processing conditions on the basis of the results 
of an analysis of the probability density function. 
The phase "lines connecting a plurality of points" as used herein for the 
method for adjusting read-out conditions and/or image processing 
conditions for a radiation image and the method for adjusting image 
processing conditions for a radiation image in accordance with the present 
invention means lines which surround the object image approximately along 
its edge. By way of example, the lines connecting a plurality of points 
may constitute straight lines, a zigzag line, a curve of secondary order, 
a curve of third order, or a spline-like curve. 
In general, radiation images include noise components due to, for example, 
the sway in the radiation employed during the recording of the radiation 
images. Therefore, it often occurs that the edge of an object image cannot 
be detected accurately. However, it is possible for a figure to be drawn 
which approximates the edge of the object image. The method for adjusting 
read-out conditions and/or image processing conditions for a radiation 
image and the method for adjusting image processing conditions for a 
radiation image in accordance with the present invention are based on such 
findings. 
However, in cases where the edge of an object image cannot be detected 
accurately and therefore a plurality of points, which are considered as 
being present on the edge of the object image, are detected on the basis 
of the image signal (or the first image signal), there is the risk that 
part of the object image is not included within the region surrounded by 
the lines connecting the thus detected points. In such cases, the problem 
often occurs in that the image signal components of the image signal 
corresponding to the object image are not detected accurately, and 
therefore appropriate read-out conditions for the final readout and/or 
appropriate image processing conditions cannot be determined. 
In order for the aforesaid problems to be eliminated, with the method for 
adjusting read-out conditions and/or image processing conditions for a 
radiation image and the method for adjusting image processing conditions 
for a radiation image in accordance with the present invention, after a 
plurality of points, which are considered as being present on the edge of 
the object image, are detected, the detected points are moved in 
directions slightly heading away from the object image. In this manner, a 
plurality of points are found, which are located at positions in the 
vicinity of the edge of the object image, the positions are slightly 
spaced apart from the object image. Thereafter, the thus found points are 
connected with each other. When the once detected points are thus moved in 
directions slightly heading away from the object image, the whole area of 
the object image is always included in the region surrounded by the 
plurality of the thus found points. The image signal components of the 
image signal, which correspond to the region surrounded by the plurality 
of the thus found points, include the image signal components 
corresponding to the region outside of the region corresponding to the 
object image. However, when the region is employed which is surrounded by 
the points located in the vicinity of the edge of the object image, the 
area of the region, which is outside of the region corresponding to the 
object image but is inside of the region surrounded by the points located 
in the vicinity of the edge of the object image, does not vary 
substantially for different radiation images. Therefore, the pattern of 
the probability density function of the image signal components of the 
image signal, which correspond to the region surrounded by the points 
located in the vicinity of the edge of the object image, is not very 
different from a standard pattern. Accordingly, appropriate read-out 
conditions for the final readout and/or appropriate image processing 
conditions can be determined accurately on the basis of the results of an 
analysis of the probability density function. 
As described above, with the method for adjusting read-out conditions 
and/or image processing conditions for a radiation image and the method 
for adjusting image processing conditions for a radiation image in 
accordance with the present invention, a change in the image signal (or 
the first image signal) at an edge of the object image is detected. A 
plurality of points are thereby found, which are spaced apart from each 
other and located at positions in the vicinity of the edge of the object 
image, the positions being slightly spaced apart from the object image. A 
probability density function of the image signal components of the image 
signal (or the first image signal) corresponding to a region, which is 
surrounded by lines connecting the plurality of the thus found points and 
which approximately corresponds to the object image, is then created. 
Thereafter, the read-out conditions and/or the image processing conditions 
are adjusted on the basis of the results of an analysis of the probability 
density function. Therefore, even if the object image, or the like, has 
been recorded in a pattern markedly different from a standard pattern, a 
probability density function of an image signal, which function has a 
pattern close to a standard pattern, can be obtained. Accordingly, 
appropriate read-out conditions for the final readout and/or appropriate 
image processing conditions can be determined accurately on the basis of 
the results of an analysis of the probability density function. 
A method for adjusting read-out conditions and/or image processing 
conditions for a mamma radiation image including a chest wall pattern in 
accordance with the present invention is applied when a stimulable 
phosphor sheet is utilized and a preliminary readout is carried out. 
Specifically, the present invention further provides a method for adjusting 
read-out conditions and/or image processing conditions for a mamma 
radiation image including a chest wall pattern, wherein a first image 
signal made up of a series of image signal components representing 
respective picture elements in a radiation image of an object is obtained 
by exposing a stimulable phosphor sheet, on which the radiation image has 
been stored, to stimulating rays, which cause the stimulable phosphor 
sheet to emit light in proportion to the amount of energy stored thereon 
during its exposure to radiation, the emitted light being detected, the 
radiation image being composed of: 
a) an object image region constituted of a chest wall pattern, which 
extends along an edge of the stimulable phosphor sheet, and a mamma 
pattern projecting in an approximately semicircular shape from the chest 
wall pattern toward an edge of the stimulable phosphor sheet facing the 
edge, along which the chest wall pattern extends, and 
b) a background region, which is adjacent to the object image region, and 
upon which the radiation impinged directly without passing through the 
object, 
a second image signal representing the radiation image is thereafter 
obtained by again exposing the stimulable phosphor sheet to stimulating 
rays, the light emitted by the stimulable phosphor sheet being detected, 
and 
read-out conditions, under which the second image signal is to be obtained, 
and/or image processing conditions, under which the second image signal 
having been obtained is to be image processed, are adjusted on the basis 
of the first image signal, 
the method for adjusting read-out conditions and/or image processing 
conditions for a mamma radiation image including a chest wall pattern 
having the steps of: 
i) detecting a change in the first image signal, 
ii) thereby finding a plurality of boundary points between said object 
image region and the background region, 
iii) finding the center of gravity on the stimulable phosphor sheet on the 
basis of the image signal components of the first image signal, which 
represent a plurality of picture elements located along a line connecting 
each said boundary point and the edge of the stimulable phosphor sheet, 
along which edge the chest wall pattern extends, 
iv) finding a picture element spaced apart from the position, at which the 
center of gravity is located, in a direction heading away from each the 
boundary point by a distance equal to a value obtained by multiplying the 
distance between the position, at which the center of gravity is located, 
and said boundary point by a predetermined factor, and 
v) adjusting the read-out conditions and/or the image processing conditions 
on the basis of the image signal components of the first image signal 
corresponding to the region surrounded by the plurality of the boundary 
points and a plurality of the picture elements, which have thus been 
found. 
A method for adjusting image processing conditions for a mamma radiation 
image including a chest wall pattern in accordance with the present 
invention is applied when a recording medium, such as a stimulable 
phosphor sheet or X-ray film, is utilized. 
Specifically, the present invention still further provides a method for 
adjusting image processing conditions for a mamma radiation image 
including a chest wall pattern, wherein an image signal made up of a 
series of image signal components representing respective picture elements 
in a radiation image of an object is obtained by photoelectrically reading 
out the radiation image from a recording medium, on which the radiation 
image has been recorded, the radiation image being composed of: 
a) an object image region constituted of a chest wall pattern, which 
extends along an edge of the recording medium, and a mamma pattern 
projecting in an approximately semicircular shape from the chest wall 
pattern toward an edge of the recording medium facing the edge, along 
which the chest wall pattern extends, and 
b) a background region, which is adjacent to the object image region, and 
upon which the radiation impinged directly without passing through the 
object, and 
image processing conditions, under which the image signal is to be image 
processed, are adjusted on the basis of the image signal, 
the method for adjusting image processing conditions for a mamma radiation 
image including a chest wall pattern having the steps of: 
i) detecting a change in the image signal, 
ii) thereby finding a plurality of boundary points between the object image 
region and the background region, 
iii) finding the center of gravity on the recording medium on the basis of 
the image signal components of the image signal, which represent a 
plurality of picture elements located along a line connecting each the 
boundary point and the edge of the recording medium, along which edge the 
chest wall pattern extends, 
iv) finding a picture element spaced apart from the position, at which the 
center of gravity is located, in a direction heading away from each the 
boundary point by a distance equal to a value obtained by multiplying the 
distance between the position, at which the center of gravity is located, 
and the boundary point by a predetermined factor, and 
v) adjusting the image processing conditions on the basis of the image 
signal components of the image signal corresponding to the region 
surrounded by the plurality of the boundary points and a plurality of the 
picture elements, which have thus been found. 
In general, by obtaining reproduced visible images in which the image 
density, or the like, of mamma patterns is appropriate for diagnoses, most 
of diagnoses from mamma radiation images can be made accurately. However, 
in cases where a tumor, such as a cancer, is present on the side inward 
from a mamma in a human body, the effects from the tumor appear in the 
boundary region between the mamma pattern and a chest wall pattern (i.e. 
in the retro-mamma space) in the mamma radiation image including the chest 
wall pattern. By way of example, the mean-level image density (i.e. the 
mean-level value of the values of the image signal) varies markedly for 
the mamma pattern and the chest wall pattern, and therefore the boundary 
between the mamma pattern and the chest wall pattern appears in the 
retro-mamma space. If a tumor, or the like, is present on the side inward 
from the mamma, the boundary between the mamma pattern and the chest wall 
pattern will become distorted. Therefore, from the distortion of the 
boundary, it can be judged that a tumor, or the like, is present. However, 
as described above, the mean-level image density varies markedly for the 
mamma pattern and the chest wall pattern. Therefore, as in conventional 
techniques, when the read-out conditions for the final readout and/or the 
image processing conditions are set such that a visible image may be 
reproduced in which the image density, or the like, of the mamma pattern 
is appropriate for diagnoses, the retro-mamma space does not have 
appropriate image quality in the reproduced visible image. In such cases, 
there is the risk that the presence of the tumor, or the like, on the side 
inward from the mamma cannot be determined. 
In order for the aforesaid risk to be eliminated, a visible image should be 
reproduced such that both the mamma pattern and the retro-mamma space have 
good image quality. For this purpose, it is considered to find the image 
signal components of the image signal corresponding to the mamma pattern 
and the retro-mamma space, and to adjust the read-out conditions for the 
final readout and/or the image processing conditions on the basis of the 
thus found image signal components. 
Ordinarily, in order for the image signal components corresponding to part 
of a radiation image, e.g. a mamma pattern in the radiation image, to be 
found from the image signal representing the radiation image, 
differentiation processing, or the like, is carried out on the image 
signal, and points in the radiation image, at which the image density 
changes, (i.e. points at which the value of the image signal changes) are 
thereby found. However, in the retro-mamma space, the image density (or 
the value of the image signal) changes little by little. Therefore, the 
image signal components corresponding to the retro-mamma space cannot be 
found by detecting a change in the image density. 
The method for adjusting read-out conditions and/or image processing 
conditions for a mamma radiation image including a chest wall pattern and 
the method for adjusting image processing conditions for a mamma radiation 
image including a chest wall pattern in accordance with the present 
invention solve the aforesaid problems. 
The part in the object image region, which part is primarily adjacent to 
the background region, is the mamma pattern. Therefore, with the method 
for adjusting read-out conditions and/or image processing conditions for a 
mamma radiation image including a chest wall pattern and the method for 
adjusting image processing conditions for a mamma radiation image 
including a chest wall pattern in accordance with the present invention, 
the boundary points between the object image region and the background 
region, i.e. the boundary points primarily between the mamma pattern and 
the background region, are found by detecting a change in the image signal 
(or the first image signal). As for the retro-mamma space, the center of 
gravity on the recording medium is found on the basis of the image signal 
components of the image signal (or the first image signal), which 
represent a plurality of picture elements located along a line connecting 
each boundary point and the edge of the recording medium, along which edge 
the chest wall pattern extends. Thereafter, an operation is carried out in 
order to find a picture element spaced apart from the position, at which 
the center of gravity is located, in a direction heading away from each 
boundary point by a distance equal to a value obtained by multiplying the 
distance between the position, at which the center of gravity is located, 
and the boundary point by a predetermined factor. In this manner, the 
boundary between the retro-mamma space and the region, which corresponds 
to part of the chest wall pattern other than the retro-mamma space and 
which is not related to a diagnosis, is found. 
With the method for adjusting read-out conditions and/or image processing 
conditions for a mamma radiation image including a chest wall pattern and 
the method for adjusting image processing conditions for a mamma radiation 
image including a chest wall pattern in accordance with the present 
invention, the region surrounded by the boundary points and the picture 
elements, which have thus been found, is taken as a region of interest. 
The read-out conditions for the final readout and/or the image processing 
conditions are adjusted such that a reproduced visible image may be 
obtained in which the region of interest has good image quality suitable 
for a diagnosis. Therefore, both the mamma pattern and the retro-mamma 
space have good image quality in the reproduced visible image. As a 
result, a pattern of a tumor, or the like, which is present on the side 
inward from the mamma in a human body, can be detected accurately.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will hereinbelow be described in further detail with 
reference to the accompanying drawings. 
FIG. 1 is a schematic view showing an example of an X-ray image recording 
apparatus for recording a mamma image. In the X-ray image recording 
apparatus, a stimulable phosphor sheet is utilized. 
With reference to FIG. 1, a cassette 2, which houses a stimulable phosphor 
sheet therein, is disposed on an image recording table 1. An object (a 
mamma) 4 is sandwiched and pressed between the cassette 2 and a holding 
plate 3, which may be constituted of an acrylic resin, or the like. X-rays 
are produced by an X-ray source 5, which is disposed above the holding 
plate 3. The object 4 is exposed to the X-rays, which have passed through 
a conical cylinder 6 having a semicircular cross-section. 
FIG. 2 is an explanatory view showing an X-ray image, which has been 
recorded in the X-ray image recording apparatus of FIG. 1. 
With reference to FIG. 2, a semicircular irradiation field 7 is present on 
a stimulable phosphor sheet 11. The region inside of the irradiation field 
7 is constituted of a background region 8 and an object image region 9, 
which is surrounded by the background region 8. A scattered X-ray image 
region 10 (indicated by dots), which was exposed to scattered X-rays, is 
present on the side outward from the semicircular irradiation field 7. 
The graph shown at the right part of FIG. 2 indicates the amounts of energy 
stored at positions located along a straight line, y, on the stimulable 
phosphor sheet 11 during its exposure to the X-rays. The amounts of energy 
stored on the stimulable phosphor sheet 11 correspond to the values of the 
image signal, which is detected from the X-ray image stored on the 
stimulable phosphor sheet, and to the levels of image density in a visible 
image reproduced from the image signal. As illustrated in FIG. 2, the 
background region 8 has the largest amounts of energy stored, the object 
image region 9 has the second largest amounts of energy stored, and the 
region outside of the irradiation field 7 has the smallest amounts of 
energy stored. 
FIG. 3 is a perspective view showing an example of an X-ray image read-out 
apparatus, in which an embodiment of the apparatus for determining an 
image position in accordance with the present invention is employed. In 
this embodiment, a stimulable phosphor sheet is used, and a preliminary 
readout is carried out. 
With reference to FIG. 3, a stimulable phosphor sheet 11, on which an X-ray 
image having a mamma pattern embedded therein has been stored in the X-ray 
image recording apparatus shown in FIG. 1, is placed at a predetermined 
position in a preliminary read-out means 100, which carries out a 
preliminary readout by scanning the stimulable phosphor sheet 11 with a 
light beam having a low energy level, thereby releasing only part of the 
energy from the stimulable phosphor sheet 11, which energy was stored 
during its exposure to the X-rays. The stimulable phosphor sheet 11 is 
conveyed in a subscanning direction indicated by the arrow Y by a sheet 
conveyance means 13. The sheet conveyance means 13 may be constituted of 
an endless belt, or the like, and is operated by a motor 12. A laser beam 
15 having a low energy level is produced by a laser beam source 14. The 
laser beam 15 is reflected and deflected by a rotating polygon mirror 16, 
which is quickly rotated by a motor 23 in the direction indicated by the 
arrow. The laser beam 15 then passes through a converging lens 17, which 
may be constituted of an f.theta. lens, or the like. The direction of the 
optical path of the laser beam 15 is then changed by a mirror 18, and the 
laser beam 15 impinges upon the stimulable phosphor sheet 11 and scans it 
in a main scanning direction indicated by the arrow X. The main scanning 
direction is approximately normal to the subscanning direction indicated 
by the arrow Y. When the stimulable phosphor sheet 11 is exposed to the 
laser beam 15, the exposed portion of the stimulable phosphor sheet 11 
emits light 19 in an amount proportional to the amount of energy stored 
thereon during its exposure to the X-rays. The emitted light 19 is guided 
by a light guide member 20 and photoelectrically detected by a 
photomultiplier 21. The light guide member 20 is made from a light guiding 
material, such as an acrylic plate. The light guide member 20 has a linear 
light input face 20a, positioned so that it extends along the main 
scanning line on the stimulable phosphor sheet 11, and a ring-shaped light 
output face 20b, positioned so that it is in close contact with a light 
receiving face of the photomultiplier 21. The emitted light 19, which has 
entered the light guide member 20 at its light input face 20a, is guided 
through repeated total reflection inside of the light guide member 20, 
emanates from the light output face 20b, and is received by the 
photomultiplier 21. In this manner, the amount of the emitted light 19, 
which amount represents the X-ray image, is converted into an electric 
signal by the photomultiplier 21. 
An analog output signal S generated by the photomultiplier 21 is amplified 
by a logarithmic amplifier 26, and digitized by an A/D converter 27 into a 
preliminary read-out image signal SP. The preliminary read-out image 
signal SP takes a value proportional to the logarithmic value of the 
amount of the emitted light 19. 
In the preliminary readout, read-out conditions, such as the voltage 
applied to the photomultiplier 21 or the amplification factor of the 
logarithmic amplifier 26, are adjusted so that image information can be 
detected accurately even if the amount of energy stored on the stimulable 
phosphor sheet 11 during its exposure to the X-rays varies over a wide 
range. 
The preliminary read-out image signal SP obtained in the manner described 
above is fed into a storage means 28 and stored therein. Thereafter, the 
preliminary read-out image signal SP is read from the storage means 28 and 
fed into an operation means 29. On the basis of the preliminary read-out 
image signal SP, the operation means 29 determines the position of an 
object image region in the X-ray image, which has been stored on the 
stimulable phosphor sheet 11. After determining the position of the object 
image region, the operation means 29 calculates the read-out conditions G1 
for the final readout, such as the voltage to be applied to a 
photomultiplier 21' or the amplification factor to be set in a logarithmic 
amplifier 26', on the basis of the image signal components of the 
preliminary read-out image signal SP, which correspond to the object image 
region. 
A stimulable phosphor sheet 11', on which the preliminary readout has been 
finished, is placed at a predetermined position in the final read-out 
means 100' and scanned with a laser beam 15' having an energy level higher 
than that of the laser beam 15 used during the preliminary readout. In 
this manner, an image signal SQ is detected under the read-out conditions 
G1, which have been set in the manner described above. The configuration 
of the final read-out means 100' is nearly the same as that of the 
preliminary read-out means 100, and therefore elements corresponding to 
those constituting the preliminary read-out means 100 are numbered with 
corresponding primed reference numerals in FIG. 3. 
After the image signal SQ is digitized in an A/D converter 27', the image 
signal SQ is fed into an image processing means 50, which carries out 
appropriate image processing on the image signal SQ. After being image 
processed, the image signal is fed into a reproducing apparatus 60, which 
reproduces a visible image by use of the image signal. 
How the operation means 29 determines the position of the object image 
region on the basis of the preliminary read-out image signal SP will be 
described hereinbelow. 
FIGS. 4, 5A, 5B, and 5C are explanatory views showing examples of X-ray 
images, in which mamma patterns are embedded. In FIGS. 4, 5A, 5B, and 5C, 
similar elements are numbered with the same reference numerals with 
respect to FIG. 2. 
FIG. 4 shows an X-ray image, in which an object image region is positioned 
correctly. FIGS. 5A, 5B, and 5C are explanatory views showing examples of 
X-ray images, in which object image regions are positioned incorrectly. 
When the X-ray image of FIG. 5A was recorded, the object 4 was located 
incorrectly with respect to the position of the irradiation field stop 
(i.e. the conical cylinder 6). Therefore, a mammilla pattern is not 
included in the region inside of the irradiation field. In the X-ray image 
of FIG. 5B, the object image region is shifted horizontally from its 
correct position with respect to the irradiation field. When the X-ray 
image of FIG. 5C was recorded, a pattern 3a' of the lead plate 3' shown in 
FIG. 1 was recorded together. Therefore, in the X-ray image of FIG. 5C, 
part of the pattern 3a' extends to the object image region 9. Heretofore, 
the position of the object image region 9 can be determined only when the 
object image region 9 is positioned correctly in the X-ray image such 
that, as shown in FIG. 4, the background region 8 extends over the whole 
semicircular contour of the irradiation field. However, with the 
embodiment of the apparatus for determining an image position in 
accordance with the present invention, the position of the object image 
region 9 can be determined also when the object image region 9 is 
positioned incorrectly as shown in FIGS. 5A, 5B, and 5C. 
In this embodiment, as illustrated in FIG. 4, operations for finding a 
change in the value of the preliminary read-out image signal SP are 
carried out on the image signal components of the preliminary read-out 
image signal SP starting with the component corresponding to the center 
point of each edge of the stimulable phosphor sheet and continuing with 
components corresponding to positions lying in each of the directions of 
45.degree., 90.degree., and 135.degree.. In this manner, a change point in 
the preliminary read-out image signal SP at the boundary between the 
object image region 9 and the background region 8 is found. The change 
point correspond to the point a shown in FIG. 2. 
By way of example, with the method disclosed in Japanese Unexamined Patent 
Publication No. 61(1986)-170178, it is determined that an object image 
region is present only when the change point in the preliminary read-out 
image signal SP has been detected for all of the three directions of 
45.degree., 90.degree., and 135.degree.. When such a method is employed, 
the presence of the object image region cannot be determined for the X-ray 
images shown in FIGS. 5A, 5B, and 5C, in which object image regions are 
positioned incorrectly. 
Therefore, with this embodiment, a specific marking process is carried out 
in order to rate the presence or absence of the object image region. 
Specifically, when the change point in the preliminary read-out image 
signal SP is found for one of the directions of 45.degree., 90.degree., 
and 135.degree., two marks are given. Therefore, as for the lower edge of 
the stimulable phosphor sheet 11 shown in FIG. 4, six (=2+2+2) marks are 
given. As for the directions indicated by the arrows b, c, and d in FIGS. 
5A, 5B, and 5C, the object image region 9 directly adjoins the region 
outside of the irradiation field without the background region 8 
intervening therebetween. As illustrated in FIG. 2, the amount of energy 
stored on the stimulable phosphor sheet 11 (i.e. the value of the 
preliminary read-out image signal SP detected therefrom) is smaller in the 
region outside of the irradiation field than in the object image region 9. 
Therefore, operations for finding a change point, at which the value of 
the preliminary read-out image signal SP decreases sharply, are also 
carried out on the image signal components of the preliminary read-out 
image signal SP corresponding to positions lying in each of the aforesaid 
directions. When the change point, at which the value of the preliminary 
read-out image signal SP decreases sharply, is detected, a one mark is 
given for the change point. When any change point corresponding to the 
boundary between the object image region 9 and the background region 8 (to 
which change point, two marks are given) is not detected, nor a change 
point corresponding to the object image region 9 and the region outside of 
the irradiation field (to which change point, a one mark is given) is 
detected, a zero point is given as for the corresponding direction on the 
stimulable phosphor sheet 11. 
In the manner described above, a total of the marks is calculated for each 
of the four edges of the stimulable phosphor sheet 11. The total marks for 
the four edges of the stimulable phosphor sheet 11 are compared with each 
other. Thereafter, it is determined that the object image region is 
present at the position corresponding to the edge of the stimulable 
phosphor sheet 11, which edge is associated with the largest total marks. 
In this manner, the levels of the probability that the object image region 
will be present are found for the respective edges of the stimulable 
phosphor sheet 11. The levels of the probability, which have been found 
for the respective edges of the stimulable phosphor sheet 11, are then 
compared with each other, and the position at which the object image 
region is present is thereby determined. Therefore, the position of the 
object image region can be determined more accurately than with the 
conventional techniques. 
The directions, for which the change point in the preliminary read-out 
image signal SP is found, are not limited to the three directions of 
45.degree., 90.degree., and 135.degree.. For example, the change point in 
the preliminary read-out image signal SP may be found for more than three 
directions. Alternatively, the change point in the preliminary read-out 
image signal SP may be found with the method described below. 
FIG. 6 is an explanatory view showing an example of an X-ray image, which 
is the same as that shown in FIG. 4, the view serving as an aid in 
explaining a different example of how a change point in the preliminary 
read-out image signal SP is found. In FIG. 6, only the operations for 
finding a change point in the preliminary read-out image signal SP are 
shown, which are carried out starting with image signal components of the 
preliminary read-out image signal SP corresponding to the lower edge of 
the stimulable phosphor sheet 11. In this example, the operations for 
finding a change in the value of the preliminary read-out image signal SP 
are carried out on the image signal components of the preliminary read-out 
image signal SP starting with the components corresponding to the center 
point A of each edge of the stimulable phosphor sheet 11 and points B1, 
B2, which are located on both sides of the center point A, and continuing 
with components corresponding to positions lying in each of the 
directions, which are normal to each edge of the stimulable phosphor sheet 
11. In this manner, the boundary point between the object image region 9 
and the background region 8 or the boundary point between the object image 
region 9 and the region outside of the irradiation field is found. When 
the boundary point has been found, an intermediate point is then found 
which is spaced apart a predetermined distance d from the boundary point 
in the direction heading to the corresponding edge of the stimulable 
phosphor sheet 11. Thereafter, the operations for finding a boundary point 
are carried out on the image signal components of the preliminary read-out 
image signal SP starting with the component corresponding to the thus 
found intermediate point, and continuing with components corresponding to 
positions lying in each of the two directions, which are parallel to the 
corresponding edge of the stimulable phosphor sheet 11, i.e. the 
horizontal directions in FIG. 6. When the operations are carried out 
starting with each of the image signal components corresponding to the 
points A, B1, and B2, and the boundary points between the object image 
region 9 and the background region 8 are detected for the three 
directions, three marks are given. When the boundary points between the 
object image region 9 and the background region 8 are detected for the two 
directions parallel to each edge of the stimulable phosphor sheet 11, and 
at the same time a boundary point between the object image region 9 and 
the region outside of the irradiation field is detected for a direction 
which is normal to each edge of the stimulable phosphor sheet 11, two 
marks are given. When boundary points are detected which are located in a 
pattern different from the patterns described above, a one mark is given. 
When any boundary point is not detected, a zero mark is given. As for the 
operations carried out starting with the image signal components 
corresponding to the points B1 and B2 located on both sides of the center 
point A, the marks given to the point B1 or the point B2, whichever are 
larger, are employed. The marks are given in the manner described above to 
each of the points located on each edge of the stimulable phosphor sheet 
11, and marks for each edge are determined in the manner listed in Table 
1. 
TABLE 1 
______________________________________ 
A 
B.sub.1 or B.sub.2 
0 1 2 3 
______________________________________ 
0 0 2 5 8 
1 1 3 9 12 
2 4 6 11 14 
3 7 10 13 15 
______________________________________ 
For example, in cases where three marks are given to the center point A, 
and the marks given to the point B1 or the marks given to the point B2, 
whichever are larger, are two, 14 marks are given to the corresponding 
edge of the stimulable phosphor sheet 11 in accordance with Table 1. 
In the manner described above, marks are determined for each edge of the 
stimulable phosphor sheet 11. It is determined that the object image 
region is present at the edge, which is associated with the largest marks. 
The position of the object image region is determined accurately in the 
manner described above. Thereafter, the read-out conditions G1 for the 
final readout are adjusted on the basis of the image signal components of 
the preliminary read-out image signal SP, which correspond to the object 
image region. 
In the aforesaid embodiment, the read-out conditions for the final readout 
are adjusted by the operation means 29. Alternatively, predetermined 
read-out conditions may be used when the final readout is carried out 
regardless of the characteristics of the preliminary read-out image signal 
SP. On the basis of the preliminary read-out image signal SP, the 
operation means 29 may adjust image processing conditions G2 to be used in 
the image processing means 50 which carries out image processing of the 
image signal SQ. The information representing the image processing 
conditions G2 calculated by the operation means 29 may then be fed into 
the image processing means 50 as indicated by the broken line in FIG. 3. 
The operation means 29 may also adjust both the read-out conditions for 
the final readout and the image processing conditions. 
In the X-ray image read-out apparatus of FIG. 3, the preliminary read-out 
means 100 and the final read-out means 100' are separate from each other. 
Alternatively, because the configurations of the preliminary read-out 
means 100 and the final read-out means 100' are approximately identical to 
each other, a single read-out means may be utilized for performing both 
the preliminary readout and the final readout. In this case, after being 
subjected to the preliminary readout, the stimulable phosphor sheet 11 may 
be moved back to the position at which image readout is started. 
Thereafter, the final readout may be carried out. 
In cases where a single read-out means is utilized to perform both the 
preliminary readout and the final readout, it is necessary to change the 
intensity of the light beam used in the preliminary readout and the final 
readout. For this purpose, various methods may be employed as described 
above, for example, a laser beam source or the like may change the 
intensity of the light beam. 
The aforesaid embodiment is applied to the X-ray image read-out apparatus 
wherein the preliminary readout is carried out. However, the apparatus for 
determining an image position in accordance with the present invention is 
also applicable to X-ray image read-out apparatuses wherein no preliminary 
read-out operations are carried out, and only the aforesaid final read-out 
operations are carried out. In these cases, an image signal is obtained by 
use of predetermined read-out conditions. Based on the image signal, image 
processing conditions are calculated by an operation means. The calculated 
image processing conditions are taken into consideration when the image 
signal is processed. 
Also, in the aforesaid embodiment, an X-ray image of a mamma, which has 
been stored on a stimulable phosphor sheet, is processed. However, the 
apparatus for determining an image position in accordance with the present 
invention is not limited to embodiments wherein a mamma image is processed 
nor to embodiments wherein a stimulable phosphor sheet is used. The 
apparatus for determining an image position in accordance with the present 
invention is applicable widely when the position of an object image on a 
recording medium, on which the object image has been recorded at part, is 
determined. 
An embodiment of the apparatus for determining a mamma image position in 
accordance with the present invention will be described hereinbelow. 
FIG. 7 is an explanatory view showing an example of an X-ray image, which 
has been recorded in the X-ray image recording apparatus of FIG. 1. In 
FIG. 7, similar elements are numbered with the same reference numerals 
with respect to FIG. 2. 
In this embodiment, the operation means 29 of the X-ray image read-out 
apparatus shown in FIG. 3 determines the position of an object image 
region on the basis of a preliminary read-out image signal SP in the 
manner described below. 
FIGS. 8A, 8B, and 8C are explanatory views showing examples of X-ray 
images, in which mamma patterns are embedded. In FIGS. 8A, 8B, and 8C, 
similar elements are numbered with the same reference numerals with 
respect to FIG. 7. 
FIG. 8A shows an X-ray image, which has been stored on the stimulable 
phosphor sheet 11 and in which the pattern of only one of the right and 
left mammae is embedded. Each of FIGS. 8B and 8C shows an X-ray image, 
which has been stored on the stimulable phosphor sheet 11 and in which the 
patterns of the right and left mammae are embedded. In the X-ray image of 
FIG. 8B, parts of the two background regions 8, 8, which surround the two 
approximately semicircular object image regions 9, 9 are connected to each 
other. In the X-ray image of FIG. 8C; the upper one of the two background 
regions 8, 8 is slightly shifted rightwardly. 
As illustrated in FIG. 8A, it often occurs that the pattern of only one of 
the right and left mammae is stored on the stimulable phosphor sheet 11. 
Also, as illustrated in FIGS. 8B and 8C, it often occurs that the patterns 
of the right and left mammae are stored on the stimulable phosphor sheet 
11 such that they may project in approximately semicircular shapes from 
two edges (in these examples, the upper and lower edges) of the stimulable 
phosphor sheet 11, which face each other, toward the middle of the 
stimulable phosphor sheet 11. Moreover, as shown in FIG. 8C, it often 
occurs that the background region 8 is recorded at a position slightly 
shifted from the standard position. It also occurs that the object image 
region 9 is formed at a position slightly shifted from the standard 
position. 
As illustrated in FIG. 7, the image signal components of the preliminary 
read-out image signal SP corresponding to the background region 8 have 
larger values than the image signal components corresponding to the other 
regions. Therefore, in this embodiment, the preliminary read-out image 
signal SP is converted into a binary signal by using a predetermined 
threshold value Th, which is shown in FIG. 7. In the binary signal, a 
value of 1 is assigned to the image signal components corresponding to the 
background region 8, and a value of 0 is assigned to the image signal 
components corresponding to the other regions. 
Both the original X-ray image and the corresponding binary X-ray image will 
hereinbelow be referred to as the X-ray image. Operations for finding a 
change point, at which the value of the binary signal changes from 0 to 1, 
are then carried out on the signal components of the binary signal 
starting with the component corresponding to each of the center points Ca, 
Cb, Cc, and Cd of the edges 11a, 11b, 11c, and 11d (shown in each of FIGS. 
8A, 8B, and 8C) of the binary image and continuing with components 
corresponding to positions lying in the direction heading to the edge of 
the binary image, which edge faces said edge from which the operations 
were started. For example, when the operations are started from the center 
point Ca of the lower edge 11a shown in FIG. 8A, the point A is found as 
the change point, at which the value of the binary signal changes from 0 
to 1. When the change point, at which the value of the binary signal 
changes from 0 to 1, is found before the edge of the binary image is 
reached, which edge faces the edge from which the operations were started, 
an intermediate point is then found which is spaced apart a predetermined 
distance d from the change point in the direction heading to the center 
point (Ca, Cb, Cc, or Cd) from which the operations were started. 
Thereafter, the operations for finding a change point, at which the value 
of the binary signal changes from 0 to 1, are carried out on the signal 
components of the binary signal starting with the component corresponding 
to the thus found intermediate point, and continuing with components 
corresponding to positions lying in each of the two directions, which are 
parallel to the corresponding edge (11a, 11b, 11c, or 11d), on which the 
center point (Ca, Cb, Cc, or Cd) from which the operations were started is 
present. In this manner, two points are then found as the point, at which 
the value of the binary signal changes from 0 to 1. For example, when the 
operations are started from the center point Ca shown in FIG. 8A, the 
points B and C are thus found as the change point, at which the value of 
the binary signal changes from 0 to 1. When three points (A, B, and C) 
have been detected as the change point, at which the value of the binary 
signal changes from 0 to 1, it is then found that the object image region 
9 is present at the corresponding edge of the binary image. Thereafter, a 
judgment is made as to whether the object image region 9, which has thus 
been found, is or is not a true object image region 9. Therefore, the 
object image region 9, which has thus been found, is referred to as a 
prospective object image region 9. 
In the X-ray image of FIG. 8A, only a single prospective object image 
region 9 is found at the edge 11a. In the X-ray image of FIG. 8B, 
prospective object image regions 9, 9, 9, 9 are found at the four edges 
11a, 11b, 11c, and 11d. In the X-ray image of FIG. 8C, prospective object 
image regions 9, 9, 9 are found at the three edges 11a, 11b, and 11c. In 
this embodiment, the function of the operation means 29 shown in FIG. 3 
for finding the prospective object image region 9 constitutes an example 
of the prospective object image region finding means of the apparatus for 
determining a mamma image position in accordance with the present 
invention. 
FIGS. 9A through 9E are diagrams showing where the prospective object image 
regions 9, 9, . . . , which have been found in the manner described above, 
are located on stimulable phosphor sheets 11, 11, . . . . In each of FIGS. 
9A through 9E, the square represents the stimulable phosphor sheet 11 (or 
the whole X-ray image stored thereon). The circle represents the 
prospective object image region 9. 
In cases where, as shown in FIG. 9A, only a single prospective object image 
region 9 has been found on the stimulable phosphor sheet 11, it is 
directly judged that the prospective object image region 9 is a true 
object image region 9. 
In cases where, as shown in FIG. 9B, two prospective object image regions 
9, 9 have been found at two adjacent edges of the stimulable phosphor 
sheet 11, a calculation is made to find the mean value of the values of 
the image signal components of the preliminary read-out image signal SP 
corresponding to each of the prospective object image regions 9, 9. It is 
then judged that the prospective object image region 9, which is 
associated with a larger mean value, is a true object image region 9. 
In cases where, as shown in FIG. 9C, two prospective object image regions 
9, 9 have been found at two edges of the stimulable phosphor sheet 11, 
which edges face each other, a calculation is made to find the mean value 
of the values of the image signal components of the preliminary read-out 
image signal SP corresponding to each of the prospective object image 
regions 9, 9. When the mean values, which have been calculated for the 
prospective object image regions 9, 9, are approximately equal to each 
other, it is judged that the patterns of the right and left mammae are 
embedded in the X-ray image, i.e. that the two prospective object image 
regions 9, 9 are true object image regions 9, 9. When the mean values, 
which have been calculated for the prospective object image regions 9, 9, 
are markedly different from each other, it is judged that the prospective 
object image region 9, which is associated with a larger mean value, is a 
true object image region 9. 
In cases where, as shown in FIG. 9D, three prospective object image regions 
9, 9, 9 have been found, a calculation is made to find the first mean 
value of the values of the image signal components of the preliminary 
read-out image signal SP corresponding to the two prospective object image 
regions 9, 9, which have been found at the two edges of the stimulable 
phosphor sheet 11 facing each other. Also, a calculation is made to find 
the second mean value of the values of the image signal components of the 
preliminary read-out image signal SP corresponding to the remaining 
prospective object image region 9. A prospective object image region 9, 
which is associated with a larger mean value, is then employed. 
Specifically, when the first mean value is larger than the second mean 
value, it is judged that the two prospective object image regions 9, 9, 
which have been found at the two edges of the stimulable phosphor sheet 11 
facing each other, are true object image regions 9, 9. When the second 
mean value is larger than the first mean value, it is judged that only the 
remaining prospective object image region 9 is a true object image region 
9. As described above, in cases where the first mean value is larger than 
the second mean value, it may be judged directly that the two prospective 
object image regions 9, 9, which have been found at the two edges of the 
stimulable phosphor sheet 11 facing each other, are true object image 
regions 9, 9. Alternatively, as in the X-ray images shown in FIG. 9C, a 
calculation may be made to find the mean value of the values of the image 
signal components of the preliminary read-out image signal SP 
corresponding to each of the prospective object image regions 9, 9. When 
the mean values, which have been calculated for the prospective object 
image regions 9, 9, are approximately equal to each other, it may be 
judged that the two prospective object image regions 9, 9 are true object 
image regions 9, 9. When the mean values, which have been calculated for 
the prospective object image regions 9, 9, are markedly different from 
each other, it may be judged that the prospective object image region 9, 
which is associated with a larger mean value, is a true object image 
region 9. 
In cases where, as shown in FIG. 9E, four prospective object image regions 
9, 9, 9, 9 have been found, a calculation is made to find the mean value 
of the values of the image signal components of the preliminary read-out 
image signal SP corresponding to a set of the two prospective object image 
regions 9, 9, which have been found at the two edges of the stimulable 
phosphor sheet 11 facing each other. Also, a calculation is made to find 
the mean value of the values of the image signal components of the 
preliminary read-out image signal SP corresponding to the other set of the 
two prospective object image regions 9, 9, which have been found at the 
two edges of the stimulable phosphor sheet 11 facing each other. It is 
then judged that the two prospective object image regions 9, 9, which are 
associated with a larger mean value, are true object image regions 9, 9. 
As described above, in the X-ray image of FIG. 9E, it may be judged 
directly that the two prospective object image regions 9, 9, which are 
associated with a larger mean value, are true object image regions 9, 9. 
Alternatively, a calculation may be made to find the mean value of the 
values of the image signal components of the preliminary read-out image 
signal SP corresponding to each of the prospective object image regions 9, 
9, which are associated with a larger mean value. When the mean values, 
which have been calculated for the prospective object image regions 9, 9, 
are approximately equal to each other, it may be judged that the two 
prospective object image regions 9, 9 are true object image regions 9, 9. 
When the mean values, which have been calculated for the prospective 
object image regions 9, 9, are markedly different from each other, it may 
be judged that the prospective object image region 9, which is associated 
with a larger mean value, is a true object image region 9. 
In this embodiment, the operation means 29 shown in FIG. 3 has the 
functions for calculating the mean value of the values of the image signal 
components of the preliminary read-out image signal SP corresponding to 
each prospective object image region 9, and for making a judgment from the 
mean value as to whether each prospective object image region 9 is or is 
not a true object image region 9. Such functions of the operation means 29 
constitute an example of the position determining means of the first 
apparatus for determining a mamma image position in accordance with the 
present invention. 
In the manner described above, the position of the object image region 9 is 
determined by finding a change in the preliminary read-out image signal SP 
at the approximately semicircular edge of the object image region 9. 
Thereafter, a judgment is made as to whether the object image region 9 is 
or is not a true object image region 9. Therefore, the position of the 
true object image region 9 can be determined accurately. 
A judgment as to whether the object image region 9, which has been found, 
is or is not a true object image region 9 may be made on the basis of the 
mean value of the values of the image signal components of the preliminary 
read-out image signal SP in the manner described above. Alternatively, a 
judgment may be made on the basis of the geometric form, i.e. the 
approximately semicircular shape, of the object image region 9. 
FIG. 10 is an explanatory view showing an X-ray image, which is the same as 
that shown in FIG. 8B, the view serving as an aid in explaining an example 
of how a judgment is made from the geometric form of an prospective object 
image region as to whether the prospective object image region, which has 
been found, is or is not a true object image region. From the X-ray image, 
as shown in FIG. 9E, four prospective object image regions 9, 9, 9, 9 are 
found. Operations carried out for the prospective object image region 9, 
which has been found at the edge 11a, and the prospective object image 
region 9, which has been found at the edge 11d, will be primarily 
described hereinbelow. 
After the four prospective object image regions 9, 9, 9, 9 have been found 
in the manner described above, a point is found, which falls within each 
prospective object image region 9 and which is closest to the middle of 
the stimulable phosphor sheet 11. Specifically, for example, the point D 
is thus found for the prospective object image region 9, which has been 
found at the edge 11a. The point E is found for the prospective object 
image region 9, which has been found at the edge 11d. Also, one of the two 
points is found which are located on the edge of each prospective object 
image region 9 such that they are in contact with the corresponding edge 
of the stimulable phosphor sheet 11. Specifically, for example, the point 
F is thus found for the prospective object image region 9, which has been 
found at the edge 11a. The point G is found for the prospective object 
image region 9, which has been found at the edge 11d. 
The two points are thus found for each prospective object image region 9. 
Thereafter, operations are carried out to find whether the values of the 
signal components of the binary signal corresponding to the respective 
picture elements located along the line, which connect the two points, are 
primarily 0 or 1. When the values of the signal components of the binary 
signal corresponding to the respective picture elements located along said 
line are primarily 0, it is judged that the prospective object image 
region 9 is a true object image region 9. Specifically, as for the 
prospective object image region 9, which has been found at the edge 11a, 
the values of the signal components of the binary signal corresponding to 
the respective picture elements located along the line, which connect the 
points D and F, are 0. Therefore, it is judged that the prospective object 
image region 9, which has been found at the edge 11a, is a true object 
image region 9. As for the prospective object image region 9, which has 
been found at the edge 11d, the values of the signal components of the 
binary signal corresponding to the respective picture elements located 
along the line, which connect the points E and G, are 1. Therefore, it is 
judged that the prospective object image region 9, which has been found at 
the edge 11d, is not a true object image region 9. In this manner, a 
judgment as to whether the object image region 9, which has been found, is 
or is not a true object image region 9 can be made on the basis of the 
geometric form, i.e. the approximately semicircular shape, of the object 
image region 9. With this method, the position of the object image region 
9 can be determined accurately. 
No limitation is imposed on how a judgment as to whether the object image 
region 9, which has been found, is or is not a true object image region 9 
is made on the basis of the geometric form, i.e. the approximately 
semicircular shape, of the object image region 9. For example, after the 
point is found, which falls within each prospective object image region 9 
and which is closest to the middle of the stimulable phosphor sheet 11, a 
semicircle may be drawn, which has its center at the center point Ca, Cb, 
Cc, or Cd of the edge 11a, 11b, 11c, or 11d corresponding to each 
prospective object image region 9 and which passes through the thus found 
point closest to the middle of the stimulable phosphor sheet 11. For 
example, a semicircular arc J is drawn for the prospective object image 
region 9 corresponding to the edge 11a shown in FIG. 11A. Also, a 
semicircular arc K is drawn for the prospective object image region 9 
corresponding to the edge 11d. Thereafter, operations may be carried out 
to calculate the frequency of occurrence of a value of 0 and the frequency 
of occurrence of a value of 1 in the signal components of the binary 
signal, which correspond to the region inside of the semicircle. On the 
basis of the ratio of the frequency of occurrence of a value of 0 to the 
frequency of occurrence of a value of 1, a judgment may be made as to 
whether the prospective object image region 9 is or is not a true object 
image region 9. Any of other methods may be employed with which a judgment 
is made on the basis of the geometric form. 
In this embodiment, the function of the operation means 29 shown in FIG. 3 
for determining the position of the true object image region 9 on the 
basis of the geometric form constitutes an example of the position 
determining means of the second apparatus for determining a mamma image 
position in accordance with the present invention. 
The operations for finding a prospective object image region 9 are not 
limited to those described above. 
FIGS. 11A and 11B are explanatory views showing X-ray images, which are the 
same as that shown in FIG. 8A, the view serving as an aid in explaining 
different examples of how an prospective object image region 9 is found. 
In FIG. 11A, operations for finding a point lying on the contour of a 
prospective object image region 9 are carried out on the signal components 
of the binary signal starting with the component corresponding to the 
center point Ca of the edge 11a of the stimulable phosphor sheet 11 and 
continuing with components corresponding to positions lying in each of the 
directions of 45.degree., 90.degree., and 135.degree.. The prospective 
object image region 9 may also be found by carrying such operations for 
each of the edges 11a, 11b, 11c, and 11d. 
In FIG. 11B, in the same manner as that in the aforesaid embodiment, 
operations for finding points lying on the contour of a prospective object 
image region 9 are carried out on the signal components of the binary 
signal starting with the component corresponding to the center point Ca of 
the edge 11a of the stimulable phosphor sheet 11. Also, in the same 
manner, operations for finding points lying on the contour of a 
prospective object image region 9 are carried out on the signal components 
of the binary signal starting with each of the components corresponding to 
the points Ca' and Ca", which are located on both sides of the center 
point Ca. In this case, at most nine contour points are found. In cases 
where only eight points or fewer points can be found, a judgment as to the 
presence or absence of an object image region 9 is made by utilizing 
predetermined algorithms. 
Alternatively, any of operations other than those described above may be 
employed. The prospective object image region finding means of the first 
and second apparatuses for determining a mamma image position in 
accordance with the present invention may employ any of operation methods, 
with which a change in the image signal at the edge of the object image 
region can be found. In the aforesaid embodiments of the first and second 
apparatuses for determining a mamma image position in accordance with the 
present invention, the preliminary read-out image signal SP is converted 
into a binary signal. Alternatively, instead of the binary signal being 
generated, a prospective object image region may be found on the basis of 
the preliminary read-out image signal SP. 
After the position of the object image region is determined accurately, the 
read-out conditions G1 for the final readout are adjusted on the basis of 
the image signal components of the preliminary read-out image signal SP 
corresponding to the object image region. 
In the aforesaid embodiments of the first and second apparatuses for 
determining a mamma image position in accordance with the present 
invention, the X-ray image of a mamma, which has been stored on a 
stimulable phosphor sheet, is processed. However, the first and second 
apparatuses for determining a mamma image position in accordance with the 
present invention are not limited to apparatuses in which stimulable 
phosphor sheets are utilized, but are also applicable when other recording 
media, such as sheets of X-ray sensitive silver halide film, are used. 
An embodiment of the method for adjusting read-out conditions and/or image 
processing conditions for a radiation image in accordance with the present 
invention will be described hereinbelow. 
FIGS. 12A, 12B, and 12C are explanatory views showing examples of X-ray 
images, which have been recorded in the X-ray image recording apparatus of 
FIG. 1. In FIGS. 12A, 12B, and 12C, similar elements are numbered with the 
same reference numerals with respect to FIG. 2. As illustrate at the right 
part of FIG. 12A, the preliminary read-out image signal SP include much 
noise components due to, for example, the sway in the X-rays used during 
the recording of the X-ray image. 
FIG. 12A shows the X-ray image having a standard pattern. As illustrated in 
FIG. 12B, it often occurs that an X-ray image is recorded such that the 
area of the background region 8 is markedly small and the area of the 
object image 9 is comparatively large. Also, as illustrated in FIG. 12C, 
it often occurs that an X-ray image is recorded such that the area of the 
background region 8 is markedly large and the area of the object image 9 
is small. With the method for adjusting read-out conditions and/or image 
processing conditions for a radiation image in accordance with the present 
invention, even if the ratio of the area of the object image 9 to the area 
of the background region 8 varies markedly for different X-ray images, the 
probability density functions of the preliminary read-out image signals SP 
can be obtained, which functions have patterns close to a standard 
pattern. 
In this embodiment, the operation means 29 of the X-ray image read-out 
apparatus shown in FIG. 3 determines the position of an object image on 
the basis of the preliminary read-out image signal SP in the manner 
described below. 
FIGS. 13A and 13B are explanatory views showing examples of X-ray images, 
in which mamma patterns are embedded, the views serving as an aid in 
explaining how a region, which approximately corresponds to an object 
image, is found. In FIGS. 13A and 13B, similar elements are numbered with 
the same reference numerals with respect to FIGS. 12A, 12B, and 12C. 
As illustrated in FIG. 12A, the image signal components of the preliminary 
read-out image signal SP corresponding to the background region 8 have 
larger values than the image signal components corresponding to the other 
regions. Therefore, in this embodiment, the preliminary read-out image 
signal SP is converted into a binary signal by using a predetermined 
threshold value Th, which is shown in FIG. 12A. In the binary signal, a 
value of 1 is assigned to the image signal components corresponding to the 
background region 8, and a value of 0 is assigned to the image signal 
components corresponding to the other regions. 
Both the original X-ray image and the corresponding binary X-ray image will 
hereinbelow be referred to as the X-ray image. Operations for finding a 
change point, at which the value of the binary signal changes from 0 to 1, 
are then carried out on the signal components of the binary signal 
starting with the component corresponding to each of the center points Ca, 
Cb, Cc, and Cd of the edges 11a, 11b, 11c, and 11d (shown in FIG. 13A) of 
the binary image and continuing with components corresponding to positions 
lying in the direction heading to the edge of the binary image, which edge 
faces said edge from which the operations were started. For example, when 
the operations are started from the center point Ca of the lower edge 11a 
shown in FIG. 13A, the point A is found as the change point, at which the 
value of the binary signal changes from 0 to 1. When the change point, at 
which the value of the binary signal changes from 0 to 1, is found before 
the edge of the binary image is reached, which edge faces said edge from 
which the operations were started, an intermediate point is then found 
which is spaced apart a predetermined distance d from the change point in 
the direction heading to the center point (Ca, Cb, Cc, or Cd) from which 
the operations were started. Thereafter, the operations for finding a 
change point, at which the value of the binary signal changes from 0 to 1, 
are carried out on the signal components of the binary signal starting 
with the component corresponding to the thus found intermediate point, and 
continuing with components corresponding to positions lying in each of the 
two directions, which are parallel to the corresponding edge (11a, 11b, 
11c, or 11d), on which the center point (Ca, Cb, Cc, or Cd) from which the 
operations were started is present. In this manner, two points are then 
found as the point, at which the value of the binary signal changes from 0 
to 1. For example, when the operations are started from the center point 
Ca shown in FIG. 13A, the points B and C are thus found as the change 
point, at which the value of the binary signal changes from 0 to 1. When 
three points (A, B, and C) have been detected as the change point, at 
which the value of the binary signal changes from 0 to 1, it is then found 
that the object image 9 is present at the corresponding edge of the binary 
image. After it is found that the object image 9 is present at the edge 
11a, the operations for finding a change point, at which the value of the 
binary signal changes from 0 to 1, are carried out on the signal 
components of the binary signal corresponding to the edge 11a. From the 
operations, the points D and E are found. In this manner, a plurality of 
the points A through E are found. Thereafter, points Ao through Eo are 
found which are spaced a distance l from the points A through E to the 
side outward from the object image 9. 
FIG. 14 is an enlarged view showing part of the X-ray image shown in FIG. 
13A. 
As described above with reference to FIG. 12A, the preliminary read-out 
image signal SP includes much noise components. Therefore, as shown in 
FIG. 14, it often occurs that the point A, which has been found in the 
manner described above, is located on the side inward from the edge 9d of 
the object image 9. Also, as indicated by points A' and A" in FIG. 14, it 
often occurs that the point, which has been found in the manner described 
above, is located on the side outward from the edge 9d of the object image 
9. Therefore, such that a point may be found which is located in the 
vicinity of and on the side outward from the edge 9d of the object image 
9, the point A, which has been found in the manner described above, is 
shifted a distance l to the side outward from the object image 9, and the 
point Ao is thereby found. As for the points B through E, the points Bo 
through Eo are found in the same manner. 
As shown in FIG. 13B, after the points Ao through Eo are thus found, they 
are connected to each other by a zigzag line. The region surrounded by the 
zigzag line is taken as the region approximately corresponding to the 
object image 9 is found. The region thus found includes the object image 9 
and is surrounded by the lines extending approximately along the edge of 
the object image 9. As described above, the lines connecting the points Ao 
through Eo are not limited to the zigzag line. 
FIG. 15 is a graph showing an example of the probability density function 
of the image signal components of the preliminary read-out image signal SP 
corresponding to the thus found region, which approximately corresponds to 
the object image 9, and examples of the probability density functions of 
the image signal components of the preliminary read-out image signals SP 
corresponding to the regions inside of the irradiation fields 7, 7, 7 in 
the X-ray images shown in FIGS. 12A, 12B, and 12C. The probability density 
functions shown in FIG. 15 have been normalized with the areas of the 
region, which approximately corresponds to the object image 9, and the 
regions inside of the irradiation fields 7, 7, 7 in the X-ray images shown 
in FIGS. 12A, 12B, and 12C. 
Probability density functions 71, 72, and 73 correspond respectively to the 
X-ray images shown in FIGS. 12A, 12B, and 12C. The ratio of the area of 
the object image 9 to the area of the background region 8 varies markedly 
for the X-ray images of FIGS. 12B and 12C. Therefore, the patterns of the 
probability density functions 72 and 73 differ markedly from each other. 
Problems will be described hereinbelow which are encountered when, for 
example, the smallest value of the preliminary read-out image signal SP 
occurring with a frequency Vo is found. In the probability density 
function 71, which corresponds to the X-ray image having a standard 
pattern as shown in FIG. 12A, and the probability density function 70 of 
the image signal components of the preliminary read-out image signal SP 
corresponding to the region found in the manner described above, which 
region approximately corresponds to the object image 9, a point SPo on the 
horizontal axis, on which the values of the preliminary read-out image 
signal SP are plotted, is found as the point corresponding to the 
frequency Vo. However, in the probability density function 72, which 
corresponds to the X-ray image shown in FIG. 12B, a point SPo' on the 
horizontal axis is found as the point corresponding to the frequency Vo. 
As a result, errors occur in setting the read-out conditions for the final 
readout. Also, in the probability density function 73, which corresponds 
to the X-ray image shown in FIG. 12C, a point SPo" on the horizontal axis 
is found as the point corresponding to the frequency Vo. In this case, 
values of the read-out conditions for the final readout are determined 
which are markedly different from correct values. In the worst case, it 
becomes necessary for a new X-ray image to be recorded. 
On the other hand, the probability density function 70 is obtained from the 
image signal components of the preliminary read-out image signal SP 
corresponding to the region, which approximately corresponds to the object 
image 9. Therefore, even if, as shown in FIGS. 12B and 12C, the ratio of 
the area of the object image 9 to the area of the background region 8 
varies markedly for different X-ray images, the probability density 
functions of the preliminary read-out image signals SP can be obtained, 
which functions have patterns close to a standard pattern. For example, 
when points corresponding to the frequency Vo are found from the 
probability density functions of the preliminary read-out image signals SP 
representing different X-ray images, the point SPo is always found as such 
points. Therefore, read-out conditions for the final readout can be set to 
values appropriate for every X-ray image. 
After the probability density function of the image signal components of 
the preliminary read-out image signal SP corresponding to the region, 
which approximately corresponds to the object image 9, is created in the 
manner described above, the read-out conditions G1 for the final readout 
are adjusted accurately on the basis of the results of an analysis of the 
probability density function. 
No limitation is imposed on how the points A through E lying on the edge of 
the object image 9 are found. For example, the points A through E may be 
found with the technique described below. 
FIGS. 11A and 11B are explanatory views showing X-ray images, which are the 
same as that shown in FIG. 13A, the view serving as an aid in explaining 
different examples of how a plurality of points lying on the edge of the 
object image 9 are found. 
In FIG. 11A, operations for finding a point lying on the edge of an object 
image 9 are carried out on the signal components of the binary signal 
starting with the component corresponding to the center point Ca of the 
edge 11a of the stimulable phosphor sheet 11 and continuing with 
components corresponding to positions lying in each of the directions of 
45.degree., 90.degree., and 135.degree.. The region approximately 
corresponding to the object image 9 may also be found by carrying such 
operations for each of the edges 11a, 11b, 11c, and 11d. 
In FIG. 11B, in the same manner as that in the aforesaid embodiment, 
operations for finding points lying on the edge of an object image 9 are 
carried out on the signal components of the binary signal starting with 
the component corresponding to the center point Ca of the edge 11a of the 
stimulable phosphor sheet 11. Also, in the same manner, operations for 
finding points lying on the edge of an object image 9 are carried out on 
the signal components of the binary signal starting with each of the 
components corresponding to the points Ca' and Ca", which are located on 
both sides of the center point Ca. In this case, at most nine points lying 
on the edge of the object image 9 are found. In cases where only eight 
points or fewer points can be found, the region approximately 
corresponding to the object image 9 is found on the basis of the eight or 
fewer points. 
Alternatively, any of operations other than those described above may be 
employed in order to find the region approximately corresponding to the 
object image 9. In the aforesaid embodiment of the method for adjusting 
read-out conditions and/or image processing conditions for a radiation 
image in accordance with the present invention, the preliminary read-out 
image signal SP is converted into a binary signal. Alternatively, instead 
of the binary signal being generated, points lying on the edge of the 
object image 9 may be found on the basis of the preliminary read-out image 
signal SP. 
In the aforesaid embodiment of the method for adjusting read-out conditions 
and/or image processing conditions for a radiation image in accordance 
with the present invention, the read-out conditions for the final readout 
are adjusted by the operation means 29. Alternatively, predetermined 
read-out conditions may be used when the final readout is carried out 
regardless of the characteristics of the preliminary read-out image signal 
SP. On the basis of the preliminary read-out image signal SP, the 
operation means 29 may adjust image processing conditions G2 to be used in 
the image processing means 50 which carries out image processing of the 
image signal SQ. The information representing the image processing 
conditions G2 calculated by the operation means 29 may then be fed into 
the image processing means 50 as indicated by the broken line in FIG. 3. 
The operation means 29 may also adjust both the read-out conditions for 
the final readout and the image processing conditions. 
The aforesaid embodiment of the method for adjusting read-out conditions 
and/or image processing conditions for a radiation image in accordance 
with the present invention is applied to the X-ray image read-out 
apparatus wherein the preliminary readout is carried out. However, the 
method for adjusting read-out conditions and/or image processing 
conditions for a radiation image in accordance with the present invention 
is also applicable to X-ray image read-out apparatuses wherein no 
preliminary read-out operations are carried out, and only the aforesaid 
final read-out operations are carried out. In these cases, an image signal 
is obtained by use of predetermined read-out conditions. Based on the 
image signal, image processing conditions are calculated by an operation 
means. The calculated image processing conditions are taken into 
consideration when the image signal is processed. 
Also, in the aforesaid embodiment of the method for adjusting read-out 
conditions and/or image processing conditions for a radiation image in 
accordance with the present invention, an X-ray image of a mamma, which 
has been stored on a stimulable phosphor sheet, is processed. However, the 
method for adjusting read-out conditions and/or image processing 
conditions for a radiation image in accordance with the present invention 
is not limited to embodiments wherein a mamma image is processed nor to 
embodiments wherein a stimulable phosphor sheet is used. The method for 
adjusting read-out conditions and/or image processing conditions for a 
radiation image in accordance with the present invention is applicable 
widely when the read-out conditions for the final readout and/or the image 
processing conditions are adjusted on the basis of an image signal 
obtained by reading out an image from a recording medium, on which an 
object image has been recorded at part. 
An embodiment of the method for adjusting read-out conditions and/or image 
processing conditions for a mamma radiation image including a chest wall 
pattern in accordance with the present invention will be described 
hereinbelow. 
FIG. 16 is an explanatory view showing an example of an X-ray image, which 
has been recorded in the X-ray image recording apparatus of FIG. 1. 
With reference to FIG. 16, a semicircular irradiation field 7 is present on 
a stimulable phosphor sheet 11. The region inside of the irradiation field 
7 is constituted of a background region 8 and the region corresponding to 
an object image 9. The object image 9 is composed of a chest wall pattern 
9a, which extends along an edge 11a of the stimulable phosphor sheet 11, 
and a mamma pattern 9b, which projects in an approximately semicircular 
shape from the chest wall pattern 9a toward an edge 11c. The boundary 
region between the chest wall pattern 9a and the mamma pattern 9b, i.e. 
the region in the vicinity of the broken line 30, is referred to as a 
retro-mamma space 9c. 
A scattered X-ray image region 10 (indicated by dots), which was exposed to 
scattered X-rays, is present on the side outward from the semicircular 
irradiation field 7. 
The graph shown at the right part of FIG. 16 indicates the amounts of 
energy stored at positions located along a straight line, y, on the 
stimulable phosphor sheet 11 during its exposure to the X-rays. The 
amounts of energy stored on the stimulable phosphor sheet 11 correspond to 
the values of the preliminary read-out image signal SP, which is detected 
during a preliminary readout from the X-ray image stored on the stimulable 
phosphor sheet, and to the levels of image density in a visible image 
reproduced on the basis of the preliminary read-out image signal SP. As 
illustrated in FIG. 16, the background region 8 has the largest mean value 
of the amounts of energy stored, the region corresponding to the object 
image 9 has the second largest mean value of the amounts of energy stored, 
and the region outside of the irradiation field 7 has the smallest mean 
value of the amounts of energy stored. In the region corresponding to the 
object image 9, the amounts of energy stored are comparatively larger in 
the region corresponding to the mamma pattern 9b than in the region 
corresponding to the chest wall pattern 9a. Also, in the retro-mamma space 
9c, the amounts of energy stored change comparatively gradually. The 
preliminary read-out image signal SP includes much noise components due to 
the sway in the X-rays used during the recording of the X-ray image. 
In this embodiment, the operation means 29 of the X-ray image read-out 
apparatus shown in FIG. 3 finds a region of interest in the X-ray image, 
which has been stored on the stimulable phosphor sheet 11, on the basis of 
the preliminary read-out image signal SP. The region of interest is 
composed of the mamma pattern 9b and the retro-mamma space 9c. How the 
region of interest is found will be described later. After the region of 
interest is found, read-out conditions G1 for the final readout are 
adjusted on the basis of the image signal components of the preliminary 
read-out image signal SP corresponding to the region of interest. 
How the operation means 29 finds the region of interest on the basis of the 
preliminary read-out image signal SP will be described hereinbelow. 
FIGS. 17A and 17B are explanatory views showing examples of X-ray images, 
in which mamma patterns are embedded, the views serving as an aid in 
explaining an example of how a region of interest is found. In FIGS. 17A 
and 17B, similar elements are numbered with the same reference numerals 
with respect to FIG. 16. 
As illustrated in FIG. 16, the image signal components of the preliminary 
read-out image signal SP corresponding to the background region 8 have 
larger values than the image signal components corresponding to the other 
regions. Therefore, in this embodiment, the preliminary read-out image 
signal SP is converted into a binary signal by using a predetermined 
threshold value Th, which is shown in FIG. 16. In the binary signal, a 
value of 1 is assigned to the image signal components corresponding to the 
background region 8, and a value of 0 is assigned to the image signal 
components corresponding to the other regions. 
Both the original X-ray image and the corresponding binary X-ray image will 
hereinbelow be referred to as the X-ray image. Operations for finding a 
change point, at which the value of the binary signal changes from 0 to 1, 
are then carried out on the signal components of the binary signal 
starting with the component corresponding to each of the center points Ca, 
Cb, Cc, and Cd of the edges 11a, 11b, 11c, and 11d (shown in FIG. 17A) of 
the binary image and continuing with components corresponding to positions 
lying in the direction heading to the edge of the binary image, which edge 
faces said edge from which the operations were started. For example, when 
the operations are started from the center point Ca of the lower edge 11a 
shown in FIG. 17A, the point A is found as the change point, at which the 
value of the binary signal changes from 0 to 1. When the change point, at 
which the value of the binary signal changes from 0 to 1, is found before 
the edge of the binary image is reached, which edge faces said edge from 
which the operations were started, an intermediate point is then found 
which is spaced apart a predetermined distance d from the change point in 
the direction heading to the center point (Ca, Cb, Cc, or Cd) from which 
the operations were started. Thereafter, the operations for finding a 
change point, at which the value of the binary signal changes from 0 to 1, 
are carried out on the signal components of the binary signal starting 
with the component corresponding to the thus found intermediate point, and 
continuing with components corresponding to positions lying in each of the 
two directions, which are parallel to the corresponding edge (11a, 11b, 
11c, or 11d), on which the center point (Ca, Cb, Cc, or Cd) from which the 
operations were started is present. In this manner, two points are then 
found as the point, at which the value of the binary signal changes from 0 
to 1. For example, when the operations are started from the center point 
Ca shown in FIG. 17A, the points B and C are thus found as the change 
point, at which the value of the binary signal changes from 0 to 1. When 
three points (A, B, and C) have been detected as the change point, at 
which the value of the binary signal changes from 0 to 1, it is then found 
that the object image 9 is present at the corresponding edge of the binary 
image. After a plurality of the points A, B, and C are found, points Ao, 
Bo, and Co are found which are spaced a distance P from the points A, B, 
and C to the side outward from the object image 9. 
FIG. 14 is an enlarged view showing part of the X-ray image shown in FIG. 
17A. 
As described above with reference to FIG. 16, the preliminary read-out 
image signal SP includes much noise components. Therefore, as shown in 
FIG. 14, it often occurs that the point A, which has been found in the 
manner described above, is located on the side inward from the edge 9d of 
the object image 9. Also, as indicated by points A' and A" in FIG. 14, it 
often occurs that the point, which has been found in the manner described 
above, is located on the side outward from the edge 9d of the object image 
9. Therefore, such that a point may be found which is located in the 
vicinity of and on the side outward from the edge 9d of the object image 
9, the point A, which has been found in the manner described above, is 
shifted a distance l to the side outward from the object image 9, and the 
point Ao is thereby found. As for the points B and C, the points Bo and Co 
are found in the same manner. After the points Ao, Bo, and Co are thus 
found, the mamma pattern 9b can be surrounded by straight lines or a curve 
connecting these points. The term "boundary points" as used herein for the 
method for adjusting read-out conditions and/or image processing 
conditions for a mamma radiation image including a chest wall pattern in 
accordance with the present invention is not limited to the points A, B, 
and C found in this embodiment, but embraces various other points, e.g. 
the points Ao, Bo, and Co. 
An example of how a picture element, which is located at the boundary 
between the retro-mamma space 9c and the part of the chest wall pattern 9a 
other than the retro-mamma space 9c, is found will be described 
hereinbelow. 
The center of gravity D on the stimulable phosphor sheet 11 is found on the 
basis of the image signal components of the preliminary read-out image 
signal SP, which represent a plurality of picture elements located along a 
straight line connecting the thus found boundary point A or Ao and the 
center point Ca of the edge 11a of the stimulable phosphor sheet 11. As 
indicated by the profile of the preliminary read-out image signal SP shown 
in FIG. 16, the values of the image signal components of the preliminary 
read-out image signal SP corresponding to the chest wall pattern 9a are 
markedly smaller than the values of the image signal components 
corresponding to the mamma pattern 9b. Therefore, of the image signal 
components of the preliminary read-out image signal SP, which represent a 
plurality of picture elements located along the line connecting the thus 
found boundary point A or Ao and the center point Ca of the edge 11a of 
the stimulable phosphor sheet 11, the image signal components of the 
preliminary read-out image signal SP, which represent a plurality of 
picture elements located in the region corresponding to the chest wall 
pattern 9a, make little contribution to the results of the operations for 
finding the center of gravity D. Accordingly, the thus found center of 
gravity D is located in the vicinity of the middle of the mamma pattern 
9b. In this embodiment, the center of gravity is found on the basis of the 
preliminary read-out image signal SP, the value of which is proportional 
to the logarithmic value of the amount of light emitted by the stimulable 
phosphor sheet 11. Alternatively, the center of gravity may be found on 
the basis of the signal, the value of which is proportional to the amount 
of light emitted by the stimulable phosphor sheet 11. 
After the center of gravity D is found in the manner described above, 
operations are carried out in order to find a picture element E spaced 
apart from the position, at which center of gravity D is located, in a 
direction heading to the center point Ca by a distance equal to a value, b 
(b=a.multidot..eta.), obtained by multiplying the distance, a, between the 
boundary point A or Ao and the position, at which the center of gravity D 
is located, by a predetermined factor h. The value of the factor h is 
predetermined such that the thus found picture element E may lie at the 
boundary between the retro-mamma space 9c and the part of the chest wall 
pattern 9a other than the retro-mamma space 9c. The picture element E is 
found in the manner described above, and points F and G, which are located 
at the boundary of the irradiation field 7 and, at the same time, at the 
boundary between the object image 9 and the background region 8, are 
found. Thereafter, a line 32 is found, which is parallel to the line 
passing through the point E and connecting the two points F and G. 
As shown in FIG. 17B, after the points Ao, Bo, Co, the point E, and the 
line 32 are found in the manner described above, a region 33 is found 
which is surrounded by the points Ao, Bo, Co, the point E, and the line 
32. The read-out conditions for the final readout are set on the basis of 
the image signal components of the preliminary read-out image signal SP 
corresponding to the thus found region 33 such that during the final 
readout the amount of light emitted by the region corresponding to the 
mamma pattern 9b and the retro-mamma space 9c may be detected accurately. 
In this embodiment, the points Bo and Co are connected with the line 32 by 
using lines, which are normal to the edge 11a of the stimulable phosphor 
sheet 11. Alternatively, the points Bo and Co may be connected with the 
line 32 by using lines, which are normal to the line 32. Also, in this 
embodiment, the region 33 is surrounded by straight lines (which 
constitute a zigzag line). Alternatively, the region 33 may be surrounded 
by any of other lines, such as a curve of secondary order, a curve of 
third order, or a spline-like curve. 
An example of how the read-out conditions for the final readout are 
determined on the basis of the image signal components of the preliminary 
read-out image signal SP corresponding to the region 33 will be described 
hereinbelow. 
FIG. 18 is a graph showing an example of the probability density function 
of the image signal components of the preliminary read-out image signal SP 
corresponding to the region 33. The values of the image signal components 
of the preliminary read-out image signal SP are plotted on the horizontal 
axis. The relative frequency of occurrence of the values of the image 
signal components of the preliminary read-out image signal SP is plotted 
on the vertical axis at the upper part of the graph, and the values of the 
image signal SQ obtained during the final readout are plotted on the 
vertical axis at the lower part of the graph. 
The probability density function of the image signal components of the 
preliminary read-out image signal SP corresponding to the region 33 is 
composed primarily of two projecting parts A and B. The projecting part A, 
which represents the frequency of occurrence of the image signal 
components of the preliminary read-out image signal SP having 
comparatively small values, corresponds to the mamma pattern 9b and the 
retro-mamma space 9c. The projecting part B, which represents the 
frequency of occurrence of the image signal components of the preliminary 
read-out image signal SP having comparatively large values, corresponds to 
part of the background region 8 included in the region 33. As described 
above, the projecting part A includes the image signal components 
corresponding to the retro-mamma space 9c. Therefore, the projecting part 
A extends to the smaller value side of the preliminary read-out image 
signal SP than a projecting part A', which corresponds to the mamma 
pattern 9b. 
The values of the probability density function are compared to a 
predetermined threshold value T, starting with the value of the function 
at the minimum value of the preliminary read-out image signal SP and 
working along the direction of increase of the image signal values. In 
this manner, a point e, at which the probability density function first 
crosses the threshold value T, and a point f, at which the probability 
density function next crosses the threshold value T, are found. Values SP1 
and SP2 are then found which correspond to the points e and f. The 
read-out conditions for the final readout are set such that the values SP1 
and SP2 of the preliminary read-out image signal SP may be detected 
respectively as the minimum value SQ1 and the maximum value SQ2 of the 
image signal SQ during the final readout. Specifically, the read-out 
conditions for the final readout are set such that during the final 
readout the image information represented by values of the emitted light 
signal falling within the range of SP1 to SP2 may be detected as the image 
signal SQ with values lying on the straight line G1 shown in FIG. 18. By 
carrying out a final readout under the thus set read-out conditions, the 
image signal SQ is obtained which represents the mamma pattern 9b and the 
retro-mamma space 9c. 
No limitation is imposed on how the boundary points A, B, and C between the 
mamma pattern 9b and the background region 8 are found, and how the 
boundary line between the retro-mamma space 9c and part of the chest wall 
pattern 9a other than the retro-mamma space 9c is found. For example, the 
technique described below may be employed. 
FIGS. 19A and 19B are explanatory views showing examples of X-ray images, 
which are the same as that shown in FIG. 17A, the views serving as an aid 
in explaining different examples of how a region, which approximately 
corresponds to an object image, is found. 
In FIG. 19A, operations for finding a point lying on the edge of an object 
image are carried out on the signal components of the binary signal 
starting with the component corresponding to the center point Ca of the 
edge 11a of the stimulable phosphor sheet 11 and continuing with 
components corresponding to positions lying in each of the directions of 
45.degree., 90.degree., and 135.degree.. The boundary points between the 
mamma pattern 9b and the background region 8 may also be found by carrying 
such operations for each of the edges 11a, 11b, 11c, and 11d. 
In FIG. 19B, in the same manner as that in the aforesaid embodiment, 
operations for finding the boundary points between the mamma pattern 9b 
and the background region 8 are carried out on the signal components of 
the binary signal starting with the component corresponding to the center 
point Ca of the edge 11a of the stimulable phosphor sheet 11. Also, in the 
same manner, operations for finding boundary points are carried out on the 
signal components of the binary signal starting with each of the 
components corresponding to the points Ca' and Ca", which are located on 
both sides of the center point Ca. In this case, at most nine boundary 
points are found. In cases where only eight points or fewer points can be 
found, the eight or fewer points are taken as the boundary points. 
In such cases, three centers of gravity D, D', and D" are found in the same 
manner as that in the embodiment described above with reference to FIGS. 
17A and 17B. Therefore, three picture elements E, E', and E" are found 
which lie at the boundary between the retro-mamma space 9c and part of the 
chest wall pattern 9a other than the retro-mamma space 9c. In such cases, 
two points F and G shown in FIG. 17A need not be found, but a line 32' 
connecting the three points E, E', and E" can be found. 
Alternatively, any of operations other than those described above may be 
employed in order to find the boundary points. Also, more picture elements 
than those described above may be found. In the aforesaid embodiment of 
the method for adjusting read-out conditions and/or image processing 
conditions for a mamma radiation image including a chest wall pattern in 
accordance with the present invention, when the boundary points are to be 
found, the preliminary read-out image signal SP is converted into a binary 
signal. Alternatively, instead of the binary signal being generated, the 
boundary points may be found on the basis of the preliminary read-out 
image signal SP. 
In the aforesaid embodiment of the method for adjusting read-out conditions 
and/or image processing conditions for a mamma radiation image including a 
chest wall pattern in accordance with the present invention, the read-out 
conditions for the final readout are adjusted by the operation means 29. 
Alternatively, predetermined read-out conditions may be used when the 
final readout is carried out regardless of the characteristics of the 
preliminary read-out image signal SP. On the basis of the preliminary 
read-out image signal SP, the operation means 29 may adjust image 
processing conditions G2 to be used in the image processing means 50 which 
carries out image processing of the image signal SQ. The information 
representing the image processing conditions G2 calculated by the 
operation means 29 may then be fed into the image processing means 50 as 
indicated by the broken line in FIG. 3. The operation means 29 may also 
adjust both the read-out conditions for the final readout and the image 
processing conditions. 
As described above, one of various techniques may be employed. For example, 
the intensity of the laser beam produced by the laser beam source may be 
changed. 
The aforesaid embodiment of the method for adjusting read-out conditions 
and/or image processing conditions for a mamma radiation image including a 
chest wall pattern in accordance with the present invention is applied to 
the X-ray image read-out apparatus wherein the preliminary readout is 
carried out. However, the method for adjusting read-out conditions and/or 
image processing conditions for a mamma radiation image including a chest 
wall pattern in accordance with the present invention is also applicable 
to X-ray image read-out apparatuses wherein no preliminary read-out 
operations are carried out, and only the aforesaid final read-out 
operations are carried out. In these cases, an image signal is obtained by 
use of predetermined read-out conditions. Based on the image signal, image 
processing conditions are calculated by an operation means. The calculated 
image processing conditions are taken into consideration when the image 
signal is processed. 
Also, in the aforesaid embodiment of the method for adjusting read-out 
conditions and/or image processing conditions for a mamma radiation image 
including a chest wall pattern in accordance with the present invention, 
an X-ray image of a mamma, which has been stored on a stimulable phosphor 
sheet, is processed. However, the method for adjusting read-out conditions 
and/or image processing conditions for a mamma radiation image including a 
chest wall pattern in accordance with the present invention is not limited 
to embodiments wherein a stimulable phosphor sheet is used. The method for 
adjusting read-out conditions and/or image processing conditions for a 
mamma radiation image including a chest wall pattern in accordance with 
the present invention is applicable widely when the read-out conditions 
for the final readout and/or the image processing conditions are adjusted 
on the basis of an image signal obtained by reading out an image from a 
recording medium, on which a mamma radiation image including a chest wall 
pattern has been recorded.