JPH0451230A - Device for deciding radiograph reading condition and/or image processing condition - Google Patents

Abstract

PURPOSE:To perform normal-reading, or image processing with satisfactory accuracy by obtaining the retrieval extent of an image signal at the time of obtaining a reading condition, etc., based on a smooth histogram and obtaining the reading condition, etc., by retrieving within the aforesaid retrieval extent of a smooth histogram whose smoothness is smaller than the aforesaid smooth histogram. CONSTITUTION:The smooth histograms 72 and 73 shown by (b) and (a) are obtained by smoothing the histogram (c) of a pre-reading image signal Sp. Smoothing is performed by obtaining the average value of the longitudinal axis of a frequency (c) which is included in the extents of (SPO-d)-(SPO+d) with reference to the pre-reading image signal SPO(where (d) is a prescribed value fixed in advance), and an operation for plotting the average value as the frequency of the pre-reading image signal SPO is performed for each value of the pre-reading image signal Sp. At this time, by setting the prescribed value (d) to be a comparatively small value, the smooth histogram 72 having the low smoothness as shown by (b) can be obtained, meanwhile, by setting the prescribed value (d) to be a comparatively large value, the smooth histogram 73 having the high smoothness as shown by (a) can be obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is based on an image signal representing a radiographic image, reading conditions for obtaining an image signal, image processing conditions for performing image processing on an image signal, etc. The present invention relates to a device for determining desired radiation image reading conditions and/or image processing conditions.

(Prior Art) It is practiced in various fields to read a recorded radiation image to obtain an image signal, perform appropriate image processing on the image signal, and then reproduce and record the image. For example, an X-ray image is recorded using an X-ray film with a low gamma value designed to be compatible with later image processing, and the X-ray image is read from the film on which it is recorded and converted into an electrical signal. By performing image processing on this electrical signal (image signal) and then reproducing it as a visible image in a copy photograph, etc., it is possible to obtain a reproduced image with good image quality performance such as contrast, sharpness, and graininess. (Refer to Japanese Patent Publication No. 61-5193).

The applicant has also proposed radiation (X-rays, α-rays).

When irradiated with β rays, γ rays, electron beams, ultraviolet rays, etc., a part of this radiation energy is accumulated, and then when irradiated with excitation light such as visible light, stimulable fluorescence exhibits stimulated luminescence depending on the accumulated energy. Radiographic image information of a subject such as a human body is partially recorded on a sheet of stimulable phosphor using a stimulable phosphor, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam. The resulting stimulated luminescent light is read photoelectrically to obtain an image signal, and based on this image data, a radiation image of the subject can be recorded on a recording material such as a photographic light-sensitive material, a CRT, etc. A radiation image recording and reproducing system that outputs visual images has already been proposed (Japanese Unexamined Patent Publication No. 5
No. 5-12429, No. 5B-11395.

No. 55-163472, No. 5B-104845, No. 55-116340, etc.).

This system has the practical advantage of recording images over a much wider range of radiation exposure compared to conventional radiographic systems using silver halide photography. In other words, in a stimulable phosphor, it is recognized that the amount of emitted light that is stimulated to emit light due to excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range.
Therefore, even if the amount of radiation exposure varies considerably due to various imaging conditions, the amount of stimulated luminescence emitted from the stimulable phosphor sheet can be read by the photoelectric conversion means by setting the reading gain to an appropriate value. By converting the radiation image into an electric signal and using this electric signal to output the radiation image as a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT, a radiation image that is not affected by fluctuations in radiation exposure amount can be obtained. be able to.

In the above system, the stimulable phosphor sheet is scanned in advance with a low-level light beam before obtaining an image signal by reading it under optimal reading conditions depending on the dose of radiation applied to the stimulable phosphor sheet. Pre-reading is performed to read the outline of the radiation image recorded on this sheet, the pre-read image signal obtained by this pre-reading is analyzed, and then the sheet is irradiated with a high-level light beam and scanned, and this radiation image is There is also a system configured to perform actual reading in which image signals are obtained by reading under optimal reading conditions.

Here, reading conditions are a general term for various conditions that affect the relationship between the amount of stimulated luminescence light and the output of the reading device during reading, such as reading gain, scale factor, or , the power of excitation light during reading, etc.

Also, the high level and low level of the light beam are, respectively.
If the energy of the light beam irradiated per unit area of the sheet or the energy of stimulated luminescence light emitted from the sheet depends on the wavelength of the light beam (has a wavelength sensitivity distribution), It refers to the weighting energy after weighting the energy of the light beam irradiated per unit area of the sheet with the wavelength sensitivity.As a method of changing the level of the light beam, light beams of different wavelengths are used. methods to use, methods to change the intensity of the light beam itself emitted from a laser light source, methods to change the intensity of the light beam by inserting or removing an ND filter, etc. on the optical path of the light beam, methods to change the beam diameter of the light beam. Various known methods can be used, such as a method of changing the scanning density and a method of changing the scanning speed.

In addition, regardless of whether the system performs this pre-reading or the system that does not, the obtained image signal (including the pre-read image signal) is analyzed and the optimal image processing conditions are determined when applying image processing to the image signal. Some systems let you decide. The term "image processing conditions" as used herein is a general term for various conditions when performing processing on an image signal that affects the gradation, sensitivity, etc. of a reproduced image based on the image signal. The method of determining the optimal image processing conditions based on this image signal is not limited to systems using stimulable phosphor sheets, and for example, image signals are obtained from radiation images recorded on recording sheets such as conventional X-ray films. It is also applied to the system.

Reading conditions and/or image processing conditions (hereinafter referred to as reading conditions etc.) are based on the image signal (including the pre-read image signal).

) is known as a method of obtaining a histogram of an image signal and determining reading conditions etc. based on this histogram.

FIG. 6 is a diagram showing a histogram of the pre-read image signal Sp obtained by pre-reading in the above-described pre-reading system. The horizontal axis of the figure represents the value of the pre-read image signal Sp, and the vertical axis (upper) represents the appearance frequency of the pre-read image signal Sp having 6 values (each pre-read image signal Sp corresponding to each pixel of the radiation image is 1 (counted as one). Also, the vertical axis of the figure (
(lower part) shows the value of the image signal SQ obtained by the main reading.

This histogram 70 includes a peak A of the pre-read image signal Sp which carries the subject image, and a peak corresponding to the direct radiation part where the radiation directly irradiates the stimulable phosphor sheet without passing through the subject. There is a mountain B located at a position where the value of the pre-read image signal Sp is larger than that of A. Here, the position where the frequency on the histogram 70 is T is the pre-read image signal Sp.
Search from the smaller value to the larger value, and the frequency is T
Pre-read image signals Spx and Spz corresponding to the first position a and the next position A are obtained. It is determined that the range sandwiched between the two pre-read image signals Spy and Spz obtained in this manner corresponds to the subject image on the radiation image. Therefore, when performing actual reading, the pre-read image signals Spx, Sp
The stimulated luminescent light emitted from the location on the radiation image corresponding to z is the minimum value SQ1. ]I so that it is converted into the large value SQ2, that is, the straight line G shown in FIG.
Reading conditions are determined so that the reading condition is 1, and the main reading is performed according to these reading conditions. Here, the reading condition is straight line G1
is determined by the horizontal position (sensitivity Sk) in FIG. 6 and the slope (latitude Gp) of the straight line G1.

Algorithms for such histogram analysis are determined in advance for each group classified by subject part (e.g., human head, chest, abdomen, etc.) and imaging method (normal imaging, tomography, enlarged imaging, etc.). Correct reading conditions can be found for most radiographic images by performing histogram analysis according to a predetermined algorithm, and the desired subject can be determined based on the image signal SQ obtained by performing main reading according to these correct reading conditions. Visible images with excellent viewing suitability can be reproduced.

(Problem to be Solved by the Invention) However, even if the range is limited to one unit of the histogram analysis algorithm, for example, a radiographic image of a human head facing right, the histogram of the image signal obtained by the subject is Due to various differences, there may be cases where correct reading conditions cannot be determined based on the above-mentioned histogram analysis. One of the main reasons for this is that the histogram is not a smooth curve but has many irregularities. For example, in the histogram shown in FIG. 6, if there are irregularities that cross the threshold value T as in histogram 71, the straight line corresponding to the reading condition will be incorrectly determined as the straight line Gl', and based on this reading condition When the main reading is performed, the image signal S0 is obtained which carries only the area (corresponding to the area A' on the histogram) between the pre-read image signals Spl and Spz' of the subject image 3 (see Fig. 1). In this case, for example, it may be necessary to take another photograph.

In view of the above circumstances, the present invention provides a radiographic image reading condition and/or image processing condition determination device that can at least reduce the probability that extremely deviant reading conditions, etc. are required, and determine more accurate reading conditions, etc. as a whole. The purpose is to

(Means for Solving the Problems) The first to third radiation image reading condition and/or image processing condition determining devices of the present invention are used in a system that performs pre-reading using the above-mentioned stimulable phosphor sheet. It is.

The first radiation image reading condition and image processing condition determining device of the present invention irradiates a stimulable phosphor sheet on which a radiation image is recorded with excitation light and stimulates the stimulated luminescence light emitted from the stimulable phosphor sheet. Based on the first image signal representing the radiation image obtained by reading, the stimulable phosphor sheet is irradiated with excitation light again and the stimulated luminescence light emitted from the stimulable phosphor sheet is read. Determination of radiation image reading conditions and/or image processing conditions for obtaining reading conditions for obtaining a second image signal representing a radiation image and/or image processing conditions for performing image processing on the obtained second image signal. The apparatus includes: a histogram calculation means for calculating a histogram of the first image signal; a histogram smoothing means for calculating a smoothed histogram by smoothing the histogram;
Alternatively, the image processing apparatus is characterized by comprising a condition determining means for determining the image processing conditions.

Further, the second radiation image reading condition and/or image processing condition determination device of the present invention irradiates a stimulable phosphor sheet on which a radiation image is recorded with excitation light, and detects the stimulable phosphor sheet emitted from the stimulable phosphor sheet. Based on the first image signal representing the radiation image obtained by reading the emitted light, the stimulable phosphor sheet is irradiated with excitation light again to stimulate the stimulated emitted light emitted from the stimulable phosphor sheet. Radiation image reading conditions and/or images for determining reading conditions for reading to obtain a second image signal representing the radiation image and/or image processing conditions for performing image processing on the obtained second image signal. In the processing condition determining device, a histogram calculation means for calculating a histogram of the first image signal; a histogram smoothing means for calculating a plurality of smoothed histograms having one or different degrees of smoothness by smoothing the histogram; The first image signal when determining the reading condition and/or the image processing condition based on a smoothing histogram having a higher degree of smoothness among the two smoothing histograms or the plurality of smoothing histograms having different degrees of smoothness from each other. and a search range determining means for determining a search range of the histogram before smoothing or a smoothed histogram having a smaller smoothness among the plurality of smoothed histograms having different smoothness degrees. The present invention is characterized by comprising a condition determining means for determining the reading conditions and/or the image processing conditions.

Furthermore, a third radiographic image reading condition and/or image processing condition determining device of the present invention is a radiographic image reading condition and/or image processing condition determining device in the second radiographic image reading condition and/or image processing condition determining device, wherein the one smoothing histogram or the mutual smoothness comprising a condition approximate value calculating means for calculating an approximate value of the reading condition and/or the image processing condition based on a smoothing histogram having a high degree of smoothness among a plurality of smoothing histograms having different degrees of smoothness, the condition determining means comprising: When a plurality of the reading conditions and/or the image processing conditions are determined by the condition determining means, the reading condition is approximated by the approximate value among the determined plurality of the reading conditions and/or the image processing conditions. and/or a function of extracting the image processing conditions.

Further, another device of the present invention is not limited to a stimulable phosphor sheet, but relates to a radiation image processing condition determining device for determining image processing conditions.

That is, the fourth radiation image processing condition determining device of the present invention is a radiation image processing condition determining device for determining image processing conditions for performing image processing on an image signal based on an image signal representing a radiation image, A histogram calculation means for calculating a histogram of an image signal, a histogram smoothing means for calculating a smoothed histogram by smoothing the histogram, and a condition determining means for calculating the image processing conditions based on the smoothed histogram. This is a characteristic feature.

Further, a fifth radiation image processing condition determining device of the present invention is a radiation image processing condition determining device for determining image processing conditions for performing image processing on an image signal based on an image signal representing a radiation image. a histogram calculation means for obtaining a histogram of a signal; a histogram smoothing means for obtaining a plurality of smoothed histograms having mutually different degrees of smoothness by smoothing the histogram; search range determining means for determining a search range of the image signal when determining the image processing conditions based on a smoothed histogram having a high degree of smoothness among a plurality of smoothed histograms; The image processing apparatus is characterized by comprising a condition determining means for determining the image processing condition by searching within the search range of a smoothing histogram having a small smoothness among a plurality of smoothing histograms having different degrees of smoothness.

Furthermore, the sixth radiation image processing condition determining device of the present invention includes:
In the fifth radiographic image processing condition determining device, an outline of the image processing conditions is determined based on the smoothing histogram having a higher degree of smoothness among the one smoothing histogram or the plurality of smoothing histograms having different degrees of smoothness. The condition determining means includes a condition approximate value calculating means for calculating a value, and when the condition determining means determines a plurality of the image processing conditions, the condition determining means calculates a value based on the approximate value among the plurality of image processing conditions determined. The present invention is characterized by having a function of extracting approximate image processing conditions.

(Function) The first radiographic image reading condition and/or image processing condition determining device and the fourth radiographic image processing condition determining device of the present invention obtain a smoothed histogram by smoothing the histogram. Since the reading conditions, etc. are determined based on the smoothed histogram, there is a possibility that the reading conditions, etc., will be determined with some error compared to the case where the reading conditions, etc. are determined correctly based on the histogram before smoothing. However, it is possible to prevent reading conditions etc. from being required to be extremely deviant, and it is possible to perform book reading or image processing with almost sufficient accuracy using the obtained reading conditions etc.

Further, the second radiation image reading condition and/or image processing condition determining device and the fifth radiation image processing condition determining device of the present invention are capable of determining image signals (i.e., This is because reading conditions, etc. are determined by searching within the search range of the histogram before smoothing or a smoothed histogram with a smaller degree of smoothness than the smoothed histogram. First, by limiting the search range, it is possible to prevent extremely deviant reading conditions, etc. from being required, and also by searching for unsmoothed histograms or histograms with low smoothness to determine reading conditions, etc. This means that it is possible to obtain accurate reading conditions, etc.

Further, the third radiographic image reading condition and/or image processing condition determining device and the sixth radiographic image processing condition determining device of the present invention each have a second radiographic image reading condition and/or image processing condition determining device.
Alternatively, in the image processing condition determination device, the fifth radiation image processing condition determination device, approximate values of the search range and reading conditions etc. are determined based on the smoothed histogram, and the histogram before smoothing or the smoothed histogram with a low degree of smoothness is obtained. When a plurality of reading conditions, etc. are determined based on the above, the reading conditions, etc. approximated by the above-mentioned approximate values are extracted. In addition to the effects of the radiographic image processing condition determining device described in Section 5, a solution is provided when a plurality of reading conditions are found by searching within the search range, and more correct reading conditions, etc., are found in a probabilistic manner.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 is a perspective view showing an example of a computer system including an example of an X-ray image reading device and an example of the radiation image reading condition and/or image processing condition determining device of the present invention. This system uses the aforementioned stimulable phosphor sheet and performs pre-reading.

In an X-ray imaging device (not shown), an X-ray image of a subject is accumulated and recorded on a stimulable phosphor sheet.

A stimulable phosphor sheet 11c on which this X-ray image is recorded;
The sheet 11 is first set at a predetermined position in a pre-reading means 100 which performs pre-reading by scanning with a weak light beam and emitting only a portion of the radiation energy accumulated in the sheet 11. The stimulable phosphor sheet 11 set at a predetermined position is conveyed (sub-scanned) in the direction of arrow Y by a sheet conveying means 13 such as an endless belt driven by a motor 12. On the other hand, a weak light beam 15 emitted from a laser light source 14 is reflected and deflected by a rotating polygon mirror 16 that is driven by a motor 23 and rotates at high speed in the direction of the arrow, passes through a focusing lens 17 such as an fθ lens, and then passes through a mirror 18 to is incident on the sheet 11 in the sub-scanning direction (arrow Y
Main scanning is performed in the direction of arrow X, which is substantially perpendicular to the main direction. From the part of the sheet 11 irradiated with this light beam I5, stimulated luminescence light 1 of a light amount corresponding to the radiographic image information stored and recorded is emitted.
9 is emitted, and this stimulated luminescence light 19 is guided by a light guide 20 to a photomultiplier (photomultiplier tube).
21 photoelectrically detected. The light guide 20 is made by molding a light-guiding material such as an acrylic plate, and is arranged so that the linear entrance end surface 20a extends along the main scanning line on the stimulable phosphor sheet 11. The light receiving surface of the photomultiplier 21 is coupled to the annularly formed output end surface 20b. The above-mentioned entrance end surface 20a
The stimulated luminescence light 19 that enters the light guide 20 from above travels through the interior of the light guide 20 through repeated total reflection, exits from the output end face 20b, is received by the photomultiplier 21, and is stimulated to produce a radiation image. A photomultiplier 21 converts the amount of emitted light 19 into an electrical signal.

The analog output signal S output from the second photomultiplier is logarithmically amplified by a logarithmic amplifier 26, and digitized by an A/D converter 27 to obtain a pre-read image signal Sp. The signal level of this pre-read image signal Sp is the sea-th l
It is proportional to the logarithm of the amount of stimulated luminescence light emitted from each pixel.

In the above-mentioned pre-reading, reading conditions, such as the voltage value applied to the photomultiplier 21 and the amplification factor of the logarithmic amplifier 26, are determined so that the radiation energy accumulated in the stimulable phosphor sheet can be read over a wide range. ing.

The obtained pre-read image signal Sp is sent to the computer system 4
It is input to 0. This computer system 40 includes an example of the radiation image reading condition and/or image processing condition determination device of the present invention, and includes a main body 41 in which a CPU and internal memory are built-in, and a floppy disk inserted as an auxiliary memory. Drive unit 4 that is driven
2. A keyboard 43 for the operator to input necessary instructions to the computer system 40. and a CRT display 44 for displaying necessary information.

In this computer system 40, the irradiation field is recognized as described later based on the input pre-read image signal Sp, and then the reading conditions for the actual reading, that is, the sensitivity Sk and the latitude Gp for the actual reading are determined. According to the obtained sensitivity Sk and latitude Gp, for example, the voltage value applied to the photomultiplier 21', the amplification factor of the logarithmic amplifier 26', etc. are controlled.

Here, the latitude Gp corresponds to the light intensity ratio of the most intense stimulated luminescence light to the weakest stimulated luminescence light that is converted into an image signal during main reading, and the sensitivity Sk corresponds to the ratio of the light amount of the most intense stimulated luminescence light to the weakest stimulated luminescence light that is converted into an image signal during main reading. This refers to the photoelectric conversion rate that determines the level of image signal generated from stimulated luminescence light.

The stimulable phosphor sheet 11' for which pre-reading has been completed is set at a predetermined position in the main reading means 100', and the sheet 11' is scanned by a light beam 15' which is stronger than the light beam used for the above-mentioned pre-reading, and the pre-read image signal is detected. An image signal is obtained according to the reading conditions determined based on Sp.
Since the configuration of 00' is the configuration and time of the above-mentioned pre-reading means 100, the components corresponding to each component of the pre-reading means 100 are indicated by adding a dash to the number used in the pre-reading means 100, Explanation will be omitted.

The image signal SO obtained by being digitized by the A/D converter 27' is sent to the computer system 40 again.
is input. Appropriate image processing is performed on the image signal S0 within the computer system 40, and the image signal subjected to this image processing is sent to a playback device (not shown), where an X-ray image based on this image signal is played back and displayed. Ru.

Next, a method will be described in which the computer system 40 first identifies the irradiation field based on the pre-read image signal Sp, and then determines the reading conditions for actual reading.

(In this embodiment, each means is considered to be a combination of hardware and software for realizing the functions of the computer system 40 corresponding to each means referred to in the present invention.

FIG. 3 is a graph showing an X-ray image recorded on the stimulable phosphor sheet 11, a pre-read image signal Sp obtained from this X-ray image, and its differential value ΔSp.

Here, the center C of the stimulable phosphor sheet 11 is selected,
Along each of the plurality of line segments 5 extending radially from the center C, a differential operation is performed on the pre-read image signal Sp corresponding to each pixel on each line segment, and the value of the pre-read image signal Sp suddenly decreases. These points are determined as contour points located on the contour of the irradiation field.

Hereinafter, a case will be described in which contour points on a line segment along the ξ axis among the plurality of line segments 5 are found.

Graph A is a graph representing the value of the pre-read image signal Sp obtained from each pixel along the ξ axis.

The value of the pre-read image signal Sp of the direct X-ray unit 6 where X-rays are directly irradiated onto the stimulable phosphor sheet 11 other than the subject image 3 in the irradiation field 2 is the highest, and the value of the pre-read image signal Sp is the highest at the contour of the irradiation field 2. The value of the pre-read image signal Sp is decreasing.

Graph B is a graph obtained by differentiating the pre-read image signal Sp shown in graph A from the center C in the negative direction of ξ (leftward in the figure) and in the positive direction of ξ (rightward in the figure).

In the graph B, on the line segment extending from the center C in the negative direction of the ξ axis, there is a main peak projecting downward, and therefore the position of this peak a1 is determined as a contour point.

In graph B, there is a peak a2 projecting downward on a line segment extending from the center C in the positive direction of the ξ axis, and the position of this peak a2 is determined as a contour point.

As described above, the contour points 7 are determined for each of the plurality of line segments 5 connecting the center C and the end of the stimulable phosphor sheet 11. After these contour points 7 are determined, if a line along these contour points 7 is determined, that line becomes the contour of the irradiation field. The line along this contour point 7 can be created by, for example, connecting the remaining points after smoothing the points, or by locally applying the least squares method to find a plurality of straight lines and connecting them. Although it can be determined by a method such as fitting a spline curve, in this embodiment, a plurality of straight lines along the contour point 7 are determined using Rough transformation. The process of finding this straight line will be explained below.

The X-axis as shown in the figure, with one end of the stimulable phosphor sheet 11 shown in FIG. 3 (lower left end in the figure) as the origin.

When the y-axis is determined, the coordinates of each contour point are (xl.

yi )+ (x2+ yz)T ”””+ (
xm+yIl), but here these coordinates are represented by the coordinates (Xo, yo). Here, when the coordinates of the contour points are (xo + 3'o), a curve expressed by p=XOQO8θ+Vosfnθ−(1) with these XO+YO as a constant is defined as the coordinates of all the contour points (XO.

yo). This curve is as shown in FIG. 4, and there are as many contour point coordinates (x(+, yo)).

Next, intersection points (ρ., θ.) where a predetermined number of zero or more of the above-mentioned plurality of curves intersect with each other are determined. Note that due to errors in contour point coordinates ("o + yo"), it is rare for many curves to intersect exactly at one point, so in reality, for example, the intersection points of two curves may exist at intervals of less than a predetermined minute value. , the center of the group of intersections is set to the above intersection (
ρ0. θ0). Next, from the intersection point (ρ0.θ0), a straight line defined by the following formula (%) is found in the x-y orthogonal coordinate system. This straight line is a straight line extending along a plurality of contour point coordinates (xor yo). When the contour points 7 are lined up as shown in FIG. 3, these straight lines are straight lines L1 to L that are extensions of the line segments forming the contour of the irradiation field 2 as shown in FIG.

It is required as. Next, the multiple straight lines L obtained in this way
1. L2. L3. ...A region surrounded by Ll is determined, and this region is recognized as the irradiation field 2. In detail, this area is recognized as follows, for example. Inside the computer system 40 is a stimulable phosphor sheet 11.
Line segments connecting the corners of and center C Ml , Mz , M3
,...M, (4 lines if the stimulable phosphor sheet 11 is rectangular) are stored, and each of these line segments M1 to M and each of the above-mentioned straight lines L! The presence or absence of an intersection with ~L is checked. If this intersection exists, of the plane divided into two by the straight line, the plane on the side including the corner of the stimulable phosphor sheet 11 is cut off. This operation covers all straight lines Ll-L,,
By performing this on the line segments M1 to M, the straight line L
A region surrounded by 1 to L is left.

This remaining area is the irradiation field 2 (see FIG. 3).

When irradiation field 2 is obtained in this way, this irradiation field 2
The reading conditions for actual reading are determined based on the pre-read image signal Sp corresponding to .

FIG. 1 shows a pre-read image signal Sp corresponding to the entire area of the irradiation field 2.
FIG. 3 is a diagram showing a histogram ((C)), a smoothed histogram ((a), (b)) obtained by smoothing this histogram, and a method for determining reading conditions for main reading ((d)). Here, the histogram 71 before smoothing shown in (C) represents the same histogram as the histogram 71 shown in FIG.

As described above with reference to FIG. 6, if reading conditions are determined using the histogram before smoothing, reading conditions that are completely different from each other may be determined as shown in FIG. 6 Gl'.

Therefore, first, the histogram 71 shown in FIG. 1(C) is smoothed to obtain smoothed histograms 72 and 73 shown in FIGS. 1(b) and (a).

In the present invention, smoothing does not require any specific method as long as it is an operation for smoothing out small irregularities in a histogram, but the following method is adopted in this embodiment. That is, regarding the pre-read image signal SPO having a certain value, S
The average value of the frequency (vertical axis in FIG. 1(c)) included in the range of po d - Spo + d (where d is a predetermined value) is calculated, and this average value is used as the pre-read image signal SPO.
6 of the pre-read image signal Sp to plot the operation as the frequency of
Do this for values. At this time, by setting the predetermined value d to a relatively small value, a smoothed histogram 72 with a low degree of smoothness as shown in FIG. 1(b) is obtained, and the predetermined value d is set to a relatively large value. By this, Figure 1(a)
A smoothed histogram 73 with a high degree of smoothness as shown in FIG.

One aspect of the present invention is to determine reading conditions based on the smoothed histograms 72 and 73 determined as described above. If reading conditions are determined based on the histogram 71 before smoothing, extremely deviant reading conditions as shown in FIG. 6 Gl' may be obtained. 7
2), as described above, the position where the frequency on the smoothed histogram 72 is T is determined by the pre-read image signal sp.
Search from the smaller value to the larger value, and the frequency is T
Find the pre-read image signals Sp + r SP2' corresponding to the first position a' and the next position b', and use these pre-read image signals SPI + SP2' to find the reading conditions. Although there is a possibility that the reading conditions will contain some errors due to the above smoothing compared to the case where the reading conditions are correctly determined based on the histogram 70,
At least, it is possible to prevent reading conditions from being required to be extremely different.

Another aspect of the present invention is to define a search range for determining reading conditions based on a smoothed histogram, and to search for a smoothed histogram having a lower smoothness than the smoothed histogram or a histogram before smoothing. The reading conditions are determined by searching the range.

To give an example of this aspect, for example, two points a/, b are calculated based on the histogram 72 shown in FIG. 1(b) as described above.
Pre-read image signal SPI + SP2' corresponding to /
These pre-read image signals SPI r SP2
A predetermined range centered on ', Sp+ d1~
SPI' +61・SP2 di~S, 2' +d
1 (where dl is a predetermined value), and only this determined range is searched in the histogram before smoothing shown in Figure 1 (C), and two points a and b are
The pre-read image signals SPl+SP2 corresponding to 8 are obtained, and these pre-read image signals S pl and 8 P2 are the respective minimum values S of the image signal S0 obtained in the main reading.
The reading conditions along the straight line G1 are determined so that QL and the maximum value SQ2 are obtained. Here, for example, in a case like the histogram 71' shown in FIG. 1(C), SPI dl~S
As a result of searching within the range of PI+dl, two candidate points a.

C may be required. In order to cope with such a case, the pre-read image signal SPI + SP2' obtained based on the histogram 72 is stored and the obtained 2
Pre-read image signals SPl+ corresponding to the two candidate points a and c
Among SP2, the pre-read image signal SPI having a value close to the pre-read image signal S PI' is adopted. One aspect of the present invention is to perform such selection when a plurality of candidate points are obtained in this way.

Furthermore, it is also possible to adopt the method described below by integrating the above-mentioned aspects of the present invention.

That is, first, based on the smoothed histogram 73 having a high degree of smoothness, the pre-read image signal Sp+ + SP2' corresponding to the two points a'b' is obtained in the same way as in the case described above.
A predetermined range centered on each of these pre-read image signals SPI + SP2', SPI d2 to Sp+
+d2, Sp2 dz~SP2'+d2 is obtained. Here, dl is a predetermined value, which is set to a value larger than the aforementioned predetermined value d1.

Next, based on the smoothing histogram 72 with low smoothness, the predetermined range SPI d2 to SPl'+d2, S, 2
-d2~S,2'+62 is searched, and thus 2
Pre-read image signal S PI corresponding to points a', b'
S P2' is calculated, and a predetermined range SP, -d1 to S
py' +dt s SP2'-dl~SP2'10dl
is required. This predetermined range S,,'-d,~S PI
'10 d 115 P2' d 1~SP2'10 dl
is the above predetermined range Sp+ dz ~ SP1' + d2,
It is narrower than SP2 d2 to Sp2'+d2.

Furthermore, based on the histogram 71 before smoothing, the predetermined range SPI'd1 to SPl'+dl, SP2'
The area from dl to SP2'+dl is searched, thereby obtaining the pre-read image signals SPI+SP2 corresponding to the two points a and b, and these pre-read image signals S.

Reading condition G1 is determined based on SP2. Note that if a plurality of candidate points are found when searching the smoothed histogram 72 with a low degree of smoothness, the pre-read image signal SPI obtained by searching the smoothed histogram 73 with a high degree of smoothness
+ A candidate closer to SP2' is adopted, and if a plurality of candidate points are found when searching the histogram 71 before smoothing, the pre-read image signal 5PIS found by searching the smoothed histogram 72 is closer to PIS P2'. The candidate is hired.

In this way, by obtaining a large number of histograms from a smoothed histogram with a high degree of smoothness to a smoothed histogram with a low degree of smoothness or a histogram before smoothing, and gradually finding more correct reading conditions, it is possible to Even in the case of a histogram, it is possible to find correct reading conditions.

According to the reading conditions (sensitivity Sk and latitude Gp) determined in this way, the voltage applied to the photomultiplier 21' of the main reading means 100', the amplification factor of the amplifier 26', etc. are controlled, and according to the controlled conditions, A reading will be held.

In the above embodiment, the pre-reading means 100 and the main reading means 100
' are constructed separately, but as mentioned above, the structure of the pre-reading means 100 and the main reading means 100' is between the two, so the pre-reading means 100 and the main reading means 100' can be integrated. May be used for both purposes. In this case, after pre-reading, the stimulable phosphor sheet 11 may be moved back once and then scanned again to perform main reading.

When the pre-reading means and the main reading means are used, it is necessary to switch the intensity of the light beam between the pre-reading and the main reading. Various methods can be used, such as a method of switching the intensity itself.

Further, in the above embodiment, a device for determining reading conditions for reading a book using the computer system 40 was explained.
During the actual reading, reading is performed under predetermined reading conditions regardless of the pre-read image signal Sp, and the computer system 40 sets the image processing conditions when performing image processing on the image signal So based on the pre-read image signal Sp. Alternatively, the computer system 40 may obtain both the reading conditions and the image processing conditions.

Furthermore, although the above embodiment has been described with respect to a radiation image reading device that performs pre-reading, the present invention can also be applied to a radiation image reading device that immediately performs reading equivalent to the above-mentioned main reading without performing pre-reading. In this case, when reading, an image signal is obtained by reading under predetermined reading conditions, and based on this image signal, the computer system 4
Image processing conditions are determined within 0, and image processing is performed on the image signal according to the determined image processing conditions.

Further, the present invention can be used not only for systems using stimulable phosphor sheets, but also for devices using conventional X-ray films.

(Effects of the Invention) As explained in detail above, the first radiation image reading condition and/or image processing condition determining device or the fourth radiation image processing condition determining device of the present invention performs reading based on a smoothed histogram. Since the conditions etc. are determined, it is possible to prevent reading conditions etc. from being determined extremely far, and it is possible to determine reading conditions with sufficient accuracy.

Further, the second radiation image reading condition and/or image processing condition determining device or the fifth radiation image processing condition determining device of the present invention determines a search range for determining reading conditions etc. based on the smoothing histogram, and smooths the image processing condition. Since the reading conditions, etc. are determined based on the unprocessed histogram or the smoothed histogram with a low degree of smoothness, it is possible to prevent extremely deviant reading conditions from being required, and furthermore, the above-mentioned first radiographic image reading conditions and/or Alternatively, it is possible to obtain more accurate reading conditions, etc. compared to the image processing condition determining device or the fourth radiographic image processing condition determining device.

Further, the third radiation image reading condition and/or image processing condition determining device or the sixth radiation image processing condition determining device of the present invention is the second radiation image reading condition and/or image processing condition determining device or the fifth radiation image processing condition determining device. In addition to the configuration of the radiographic image processing condition determination device, the approximate value of the reading condition is determined, and when multiple candidates are determined, the candidate closest to the approximate value is adopted. Reading conditions etc. will be determined more accurately.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a histogram of a pre-read image signal, a smoothed histogram obtained by smoothing this histogram, and reading conditions for actual reading. FIG. 2 is an example of an X-ray image reading device. and a perspective view showing an example of a computer system including an example of the radiation image reading condition and/or image processing condition determination device of the present invention; Figure 4 is a graph showing the pre-read image signal obtained from this X-ray image and its differential value, and Figure 5 is a graph for explaining the method of finding a straight line along the contour points. FIG. 6, an explanatory diagram for explaining a method of extracting an area surrounded by straight lines along a point, is a diagram showing a histogram of a pre-read image signal. 2...Irradiation field 3...Subject image 6...
Direct X-ray section 11, 11'...Stormable phosphor sheet 19, 19'.
... Stimulated luminescent light 21, 21' ... Photo multiplier 26, 28
'... Logarithmic amplifiers 27, 27'... A/D converter 40... Computer systems 70, 71... Histograms 72, 73... Smoothing histogram 100... Pre-reading means 100'.・・Book Reading Means Diagram Diagram

Claims (6)

[Claims] (1) A first image signal representing the radiation image obtained by irradiating the stimulable phosphor sheet on which the radiation image is recorded with excitation light and reading the stimulated luminescence light emitted from the stimulable phosphor sheet. based on the reading conditions for obtaining a second image signal representing the radiation image by irradiating the stimulable phosphor sheet with excitation light again and reading the stimulated luminescence light emitted from the stimulable phosphor sheet. and/or in a radiation image reading condition and/or image processing condition determination device for determining image processing conditions when performing image processing on the obtained second image signal, histogram calculation for determining a histogram of the first image signal; means, histogram smoothing means for obtaining a smoothed histogram by smoothing the histogram, and adjusting the reading conditions and/or the reading conditions based on the smoothed histogram.
Or, a radiographic image reading condition and/or image processing condition determining device characterized by comprising a condition determining means for determining the image processing condition. (2) A first image signal representing the radiation image obtained by irradiating the stimulable phosphor sheet on which the radiation image is recorded with excitation light and reading the stimulated luminescence light emitted from the stimulable phosphor sheet. based on the reading conditions for obtaining a second image signal representing the radiation image by irradiating the stimulable phosphor sheet with excitation light again and reading the stimulated luminescence light emitted from the stimulable phosphor sheet. and/or in a radiation image reading condition and/or image processing condition determination device for determining image processing conditions when performing image processing on the obtained second image signal, histogram calculation for determining a histogram of the first image signal; means, histogram smoothing means for obtaining one or a plurality of smoothed histograms having different degrees of smoothness by smoothing the histogram; search range determining means for determining a search range of the first image signal when determining the reading conditions and/or the image processing conditions based on the smoothed histogram having a high degree of smoothness; and the histogram before smoothing. Alternatively, the apparatus further comprises condition determining means for determining the reading condition and/or the image processing condition by searching within the search range of a smoothing histogram having a small smoothness among the plurality of smoothing histograms having different smoothness degrees. A radiation image reading condition and/or image processing condition determining device characterized in that: (3) Determine approximate values of the reading conditions and/or the image processing conditions based on the one smoothing histogram or the smoothing histogram with a higher degree of smoothness among the plurality of smoothing histograms having different degrees of smoothness. The condition determining means includes a condition approximate value calculating means, when the condition determining means determines a plurality of the reading conditions and/or the image processing conditions, the condition determining means calculates the plurality of the found reading conditions and/or the image processing conditions 3. The reading condition and/or image processing condition determining apparatus according to claim 2, further comprising a function of extracting the reading condition and/or the image processing condition approximated by the approximate value from among the image processing conditions. (4) A radiation image processing condition determining device for determining image processing conditions for performing image processing on an image signal based on an image signal representing a radiation image, comprising: a histogram calculation means for calculating a histogram of the image signal; A radiographic image processing condition determining apparatus comprising: a histogram smoothing means for obtaining a smoothed histogram by smoothing; and a condition determining means for obtaining the image processing conditions based on the smoothed histogram. (5) A radiation image processing condition determination device for determining image processing conditions for performing image processing on an image signal based on an image signal representing a radiation image, comprising: a histogram calculation means for calculating a histogram of the image signal; a histogram smoothing means for obtaining one or a plurality of smoothed histograms having different degrees of smoothness by smoothing; a search range determining means for determining a search range of the image signal when determining the image processing conditions based on a large smoothed histogram, and one of the histogram before smoothing or the plurality of smoothed histograms having different smoothness degrees; A radiographic image processing condition determining device comprising: a condition determining means for determining the image processing condition by searching within the search range of a smoothed histogram having a low degree of smoothness. (6) Condition approximate value calculation means for calculating an approximate value of the image processing condition based on the one smoothing histogram or a smoothing histogram having a higher degree of smoothness among the plurality of smoothing histograms having different degrees of smoothness. Preparation: When the plurality of image processing conditions are determined by the condition determining means, the condition determining means extracts the image processing condition approximated by the approximate value from among the plurality of determined image processing conditions. 6. The image processing condition determining device according to claim 5, further comprising the following functions.