JPH02272533A - Method for recognizing divided pattern of radiograph - Google Patents

Abstract

PURPOSE:To find accurate read conditions and image processing conditions by recognizing divided patterns when a recording sheet is divided into plural parts and photographed, part by part, from the combination of longitudinal and lateral distribution shapes of image density on the recording sheet. CONSTITUTION:Many image data which represent the radiograph are obtained from the recording sheet (accumulating fluorescent sheet, X-ray film, etc.) 11, the longitudinal and lateral distribution shape of image density on the recording sheet are detected from the image data, and the divided patterns of the radiation image are recognized from the combination of the distribution shapes in both directions. For example, when the profile of image data has one peak on a longitudinal crossing segment in the center and has a waveform having peaks on lateral crossing segment at both ends and in the center, it is decided that the image has a pattern which is divided into two right and left parts by a border extending longitudinally at the center 11c. Consequently, more appropriate read conditions and image processing conditions can be found by extracting image data corresponding to an object part in divided pattern units.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for recognizing a division pattern of a radiation image recorded on a recording sheet such as a stimulable phosphor sheet or an X-ray film.

(Prior Art) It is practiced in various fields to read a recorded radiation image to obtain image data, perform appropriate image processing on this image data, 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. A system that can obtain reproduced images with good image quality performance such as contrast sharpness and graininess by converting the electrical signals (image data) and performing image processing on them and then reproducing them as visible images in photocopies, etc. has been developed (see Japanese Patent Publication No. 61-5193).

In addition, the applicant has proposed radiation (X-rays, α-rays).

When irradiated with β-rays, γ-rays, two-electron beams, ultraviolet rays, etc., a part of this radiation energy is accumulated, and then when excitation light such as visible light is irradiated, stimulable fluorescence exhibits stimulated luminescence depending on the accumulated energy. A radiation image of a subject such as a human body is photographed and 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 image data, 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 a visual image has already been proposed. For example, Japanese Patent Application Laid-open No. 55-12429 (U.S. Pat. No. 4,258,264)
No. 5B-11395, No. 55-IG3472 (U.S. Patent No. 4315318), No. 5B-10464
No. 5.

See No. 55-116340 (US Pat. No. 4,276,473), etc.

This system has the practical advantage of being able to record 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 image data by reading it under optimal reading conditions depending on the dose of radiation irradiated on the stimulable phosphor sheet. Pre-reading is performed to read the outline of the radiation image recorded on this sheet, the pre-read image data obtained by this pre-reading is analyzed, and then the above sheet is irradiated with a light beam of a higher level than the light beam used during the above-mentioned pre-reading. There is also a system configured to perform actual reading in which image data is obtained by scanning the radiation image and reading it under reading conditions that are optimal for this radiation image. For example, JP-A-58-87
No. 240, No. 5g-67241 (U.S. Pat. No. 4527)
No. 060), No. 5g-67241, etc.

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 intensity of the light beam irradiated per unit area of the sheet or the intensity 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 weighted intensity after weighting the intensity of the light beam irradiated per unit area of the sheet by the wavelength sensitivity, and the method of changing the level of the light beam is to use light beams of different wavelengths. 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. How to change the scanning density,
Various known methods can be used, such as a method of changing the scanning speed.

In addition, regardless of whether the system performs this prefetching or the system that does not, the obtained image data (including prefetched image data) is analyzed to determine the optimal image processing conditions when performing image processing on the image data. Some systems let you decide. The method for determining the optimal image processing conditions based on this image data is not limited to systems using stimulable phosphor sheets, but for example, image data is obtained from a radiation image recorded on a recording sheet such as a conventional X-ray film. It is also applied to the system.

In addition, when recording radiation images on a recording sheet, it is important to avoid irradiating radiation to parts of the subject that are not necessary for observation, or to prevent radiation from being irradiated to parts that are unnecessary for observation. Scattered rays may enter some areas, reducing image quality. Therefore, use an irradiation field diaphragm to limit the radiation irradiation area so that only the necessary parts of the subject and part of the recording sheet are irradiated with radiation. Often. When analyzing image data to determine reading condition 1 image processing conditions as described above, if the image data used for analysis is image data obtained from a recording sheet photographed using an irradiation field aperture, this Even if the image data is analyzed while ignoring the existence of the irradiation field, the radiographic image taken and recorded will not be understood correctly, and incorrect reading conditions and image processing conditions will be required, resulting in the inability to reproduce and record a radiographic image that is suitable for observation. occurs. In order to solve this problem, before determining the reading condition 1 image processing conditions, it is necessary to recognize the irradiation field and determine the reading condition 5 image processing conditions based on the image data within the irradiation field.

(Problems to be Solved by the Invention) By the way, in each of the above-mentioned systems, different radiation images are photographed and recorded in a plurality of divided areas on - recording sheets (stimulable phosphor sheets, X-ray films, etc.). There are things to do. According to this divisional shooting, for example, when shooting a subject that is small compared to the area of the recording sheet, it is possible to record the shooting of multiple subjects on one recording sheet, which is economical. When reading a recording sheet to obtain image data, multiple images can be read at once, and the reading processing speed is also improved.

However, in a radiation image, there are the subject area where the subject was recorded, the direct radiation area where radiation is irradiated directly onto the recording sheet without going through the subject, and the scattering area outside the irradiation area when using an irradiation field aperture. Since there are scattered radiation areas where only radiation is recorded, when determining the reading conditions and image processing conditions mentioned above, it is necessary to consider the area corresponding to the object area that ultimately needs to be reproduced as a visible image with excellent observation characteristics. Even though it is necessary to extract only image data, these conditions are determined based on the premise that the only radiation image is recorded on the recording sheet without recognizing the division pattern of the recording sheet. Subject part.

There may be cases where the direct radiation part, the scattered radiation part, etc. cannot be separated well, and the image data corresponding to the subject part cannot be successfully extracted.

In order to avoid this, it is possible to record the division pattern at the time of shooting and manually input the division pattern into the device before obtaining the image data from the recording sheet, but this method is time-consuming. This is very cumbersome and can lead to input errors.

In view of the above circumstances, the present invention provides more appropriate reading conditions and/or
Another object of the present invention is to provide a method of automatically recognizing a division pattern of a recording sheet so that image processing conditions can be determined.

(Means for Solving the Problems and Their Effects) The radiation image division pattern recognition method of the present invention represents a radiation image from a recording sheet (stimulable phosphor sheet, X-ray film, etc.) on which the radiation image is recorded. Obtaining a large number of image data, detecting the image density distribution shape in the vertical direction and the horizontal direction on the recording sheet from the image data, and recognizing the division pattern of the radiation image by a combination of the distribution shapes in both directions. This is a characteristic feature.

Various mathematical methods can be used to determine this distribution shape. For example, a profile of the image data on a line segment passing through the center of a central area of a recording sheet and crossing the area vertically and horizontally is determined, and this profile is expressed as a single mountain in the center on a line segment that crosses the area vertically. If it has a waveform that is high at both ends and the center on a horizontal line segment and is low in between, it is determined that it has a two-part pattern divided left and right by a boundary extending vertically at the center. If the vertical and horizontal directions are reversed, it is determined that the pattern is divided into two parts vertically by a boundary extending horizontally in the center, and if there is no significant difference between the two lines, there are four patterns horizontally and vertically. It is determined that it is divided.

Alternatively, the shape of the image density distribution can also be determined based on the shape of the vertical and horizontal density projections of the area.

The present invention focuses on the fact that when there is a divided pattern, there is a direct radiation part in the boundary area, and furthermore, the shape of this direct radiation part extends along the divided boundary. As described above, the image density distribution shape in the vertical and horizontal directions on the recording sheet is detected, and the division pattern of the recording sheet is recognized by the combination of the distribution shapes in both directions. be.

In this way, the present invention can easily and accurately recognize division patterns, extract image data corresponding to the subject part for each division pattern, and determine more appropriate reading conditions and image processing conditions. be able to.

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

FIG. 1 is an example of a radiation image divided into left and right halves, which is the target of the division pattern recognition method of the present invention.
1 shows an example in which two human necks are recorded side by side on the left and right. Center and left and right areas 1 of recording sheet 11
1A has a direct radiation section.

In the direct radiation section 11A, the value of the image data is particularly large among all the data, and has a value larger than the threshold value Th, which is somewhat higher than the average density of the image.

Therefore, by determining whether the value of the image data is larger than this threshold Thl, it is possible to determine whether the image data is directly from the radiation section.

Therefore, image data having a value larger than the threshold value Th1, that is, the distribution shape of the linear radiation portion 11A is examined.

As shown in FIG. 1, for example, a line segment 11a passing through the center 11C of the recording sheet 11 and crossing the image vertically and horizontally.
, llb of the image data profile tta
',IH,' and this profile Lla'
, llb' is a line segment 11 that crosses vertically as in the example in FIG.
If image data having a value equal to or greater than the predetermined value Th1 is concentrated in the center on a and distributed at both ends and the center on a horizontal line segment 11b, the distribution of image data having a value equal to or greater than the predetermined value It is determined that three are lined up horizontally, and the screen is recognized as being divided into two on the left and right. If the vertical and horizontal directions are reversed, it will be determined that there are three vertically arranged columns, and the screen will be divided into two vertically arranged columns.
perceived as being divided. In addition, as shown in Figure 2, if there is no significant difference in the profiles on both lines 9, it is determined that the direct radiation area extends both vertically and horizontally, and it is recognized that it is divided into four parts horizontally, vertically, and vertically. Ru.

Alternatively, the distribution of the radiation area can be determined directly from the horizontal and vertical density projection of the image in a manner similar to the above profile, so it can be divided using this method! , can recognize many turns.

FIG. 4 is a perspective view showing an embodiment of a radiation image reading device using an example of the divided pattern recognition method of the present invention. This device is a device for reading radiation images, such as those shown in FIG. 1, photographed and recorded on the stimulable phosphor sheet 11, and is also a device for performing the above-mentioned pre-reading.

The stimulable phosphor sheet 11 on which the radiation image has been recorded is first placed at a predetermined position by a pre-reading means 100 which performs pre-reading by scanning with a weak light beam and emitting only a part of the radiation energy stored in the sheet 11. Set. 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 1 emitted from a laser light source 14
5 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, and after passing through a focusing lens 17 such as an fθ lens, the optical path is changed by a mirror 18 and enters the sheet 11 for sub-scanning. Main scanning is performed in the direction of arrow X, which is substantially perpendicular to the direction (direction of arrow Y). From the part of the sheet 11 irradiated with this light beam 15, stimulated luminescence light 19 of a light amount corresponding to the radiographic image information stored and recorded is emitted.
is emitted, and this stimulated luminescence light 19 is guided by a light guide 20 and passed through a photomultiplier (photomultiplier tube) 21.
is detected photoelectrically by The light guide 20 is made by molding a light guide material such as an acrylic plate,
The linear incident end surface 20a is the stimulable phosphor sheet 11.
The photomultiplier 2 is disposed so as to extend along the upper main scanning line, and is disposed on an annular output end surface 20b.
1 light-receiving surfaces are combined. The stimulated luminescent light 19 that has entered the light guide 20 from the input end surface 20a travels through the interior of the light guide 20 by repeating total reflection, and then reaches the output end surface 20a.
The light is emitted from b and is received by the photo multiplier 21,
A photomultiplier 21 converts the amount of stimulated luminescent light 19 representing a radiation image into an electrical signal.

The analog output signal S output from the photomultiplier 21 is logarithmically amplified by a logarithmic amplifier 26 and digitized by an A/D converter 27 to obtain pre-read image data Sp. This pre-read image data Sp is data having a value proportional to the logarithm of the amount of stimulated luminescence light.

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 11 can be read over a wide range. It is being

The obtained pre-read image data sp is inputted into the storage means 28 and is stored therein. Thereafter, the pre-read image data Sp stored in the storage means 28 is read out and inputted to the calculation means 29, and the calculation means 29 uses the above-mentioned division pattern recognition method based on the manually input pre-read image data Sp. First, a division pattern is recognized when the stimulable phosphor sheet 11 is divided into a plurality of regions and imaging is performed for each region, and then optimal reading conditions for each divided region are determined. By determining the average reading condition of the reading conditions of
The amplification factor, etc. of ′ can be found.

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' that is stronger than the light beam used for the above-mentioned pre-reading. Image data is obtained according to the reading condition G1 determined by the main reading means 100.
Since the configuration of ' is different from the configuration of the above-mentioned pre-reading means 100, components corresponding to the respective components 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 data S0 obtained by being digitized by the A/D converter 27' is sent to the image processing means 50. The image processing means 50 performs appropriate image processing on the image data S0. The image data subjected to this image processing is sent to the reproduction device 60, and a radiation image based on this image data is reproduced and displayed.

It goes without saying that various mathematical methods can be used as the above-mentioned distribution shape discrimination method for recognizing the division pattern, and the above-mentioned two examples are merely examples thereof.

The above mathematical method will be explained in further detail. In the example of FIG. 1, image data having a value larger than the threshold value Th1 (the mountainous part) is the profile 1 that crosses the image horizontally.
In 1b', there are three locations, IIB, , 11B2, 11B3, and in vertically traversing profile 11a', there are 11 A s.
There is only one location. Also, in the example shown in FIG. 3, image data having a value larger than the threshold value Th1 is present at three locations in the horizontal projection llb' and at one location in the vertical projection 11a'. In this way, if there are three locations in the horizontal profile or horizontal projection and one location in the vertical profile or vertical projection, it is recognized that the pattern is divided into two left and right parts. If this relationship is reversed vertically and horizontally, that is, at one point in the horizontal profile or horizontal projection,
If there are three locations in the vertical profile or vertical projection, it is recognized that the pattern is divided into two vertically.

In addition, in Figure 2, there are 3 locations on the horizontal profile and 2 locations on the vertical profile, and in this case, there are 4 locations on the left, right, top, and bottom.
Recognize that you are divided. In the case of 4-division, the vertical and horizontal directions may be reversed, so even in that case, it is recognized as 4-division.

The above relationships are summarized in the table below. In this table, Na represents the number of peaks exceeding the threshold value in the vertical profile or vertical projection, and Nb represents the number of peaks exceeding the threshold value in the horizontal profile or horizontal projection.

When the division pattern is obtained in this way, next, the pre-read image data Sp corresponding to the radiation image in each division area is
, pre-read image data Sp corresponding to the subject part of the image
is extracted, and based on this, optimal reading conditions are determined for each divided area.

Note that in the apparatus shown in FIG. 4, the reading conditions for main reading cannot be changed for each image on one sheet 11 even if a plurality of images are recorded on one sheet 11.
In this device, after determining the reading conditions for each divided area as described above, the average reading condition of these reading conditions is determined, and this average reading condition is used as the reading condition G for main reading.
1.

Further, in the above embodiment, a case has been described in which the calculation means 29 calculates the reading condition G1 for main reading, but during main reading, reading is performed under a predetermined reading condition regardless of the pre-read image data Sp, and the calculation means 29, based on the pre-read image data Sp, the image processing condition G2 for performing image processing on the image data S0 in the image processing means 50 is determined, and the image obtained by the calculation means 29 is calculated as shown by the broken line in FIG. The processing conditions may be input to the image processing means 50,
Further, the calculation means 29 may calculate both the reading conditions and the image processing conditions.

Furthermore, in the above embodiment shown in FIG.
Although the pre-reading means 100 and the main reading means 100' are configured separately, as described above, the pre-reading means 100 and the main reading means 100' are configured in a parallel manner.
′ may be combined and used for the same purpose.

In this case, after pre-reading,
1 back once and scan again to read the book.

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 between the two.

Further, although the above embodiment is an example of a radiation image reading device that performs pre-reading, the present invention can also be applied to a radiation image reading device that performs reading equivalent to the above-mentioned main reading from the beginning without performing pre-reading. In this case, upon reading, image data is obtained by reading under predetermined reading conditions, and based on this image data, a division pattern of the radiographic image is determined by the calculating means, and further, image processing conditions are determined. The obtained image processing conditions are taken into consideration when image processing is performed on the image data.

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

FIG. 5 is a perspective view of an embodiment of an X-ray image reading device that reads an X-ray image recorded on an X-ray film.

An X-ray film 30 on which an X-ray image has been recorded, which has been set at a predetermined position, is conveyed by a film conveyance means 31 in the direction of arrow Y' shown in the figure.

Further, the reading light 33 emitted from the light Fi, 32, which is elongated in the − dimension, is converged by the cylindrical lens 34, and irradiates the X-ray film in a straight line in the X″ direction, which is substantially perpendicular to the arrow Y′ direction. Below the X-ray film 30 irradiated with the reading light 33, there is a position at which the reading light 33 that passes through the X-ray film 30 and is intensity-modulated by the X-ray image recorded on the X-ray film 30 is received. X' in the upper 36 X-ray images
A MOS sensor 35 is provided in which a large number of solid-state photoelectric conversion elements are linearly arranged in correspondence with each pixel interval in the force direction. While the X-ray film 30 is transported in the direction of arrow Y' while being irradiated with the reading light 33, the MOS sensor 35 converts the reading light transmitted through the X-ray film 30 into an X-ray image Y'
Light is received at predetermined time intervals corresponding to each pixel interval in the direction.

FIG. 6 is a circuit diagram showing an equivalent circuit of the MOS sensor 35.

Signals from photocarriers generated when the reading light 33 hits a large number of solid-state photoelectric conversion elements 36 are transferred to capacitors CI (i-1, 2°...) within the solid-state photoelectric conversion elements 36.
・ Accumulated in n). The accumulated photocarrier signals are sequentially read out by sequentially opening and closing the switch section 38 controlled by the shift register 37, thereby obtaining a time-series image signal. This image signal (image data) is then amplified by the amplifier 39 and output from its output terminal 40.

The output analog image data is sampled and converted into digital image data, and then, based on the image data, a division pattern is recognized in the same manner as in the embodiment described above. In this embodiment, instead of the MOS sensor 35, a CCD CP D (Charge
Needless to say, it is possible to use the following. Furthermore, in reading the X-ray film, it is of course possible to scan the film two-dimensionally with a light beam in the same way as reading the stimulable phosphor sheet described above. Further, in the above embodiment, the light transmitted through the X-ray film 30 is received, but it is of course possible to be configured so that the light reflected from the X-ray film 30 is received.

As described above, the division pattern recognition method of the present invention can be widely used in systems in which a recording sheet is divided into a plurality of parts and a photograph is taken for each divided part.

(Effects of the Invention) As explained in detail above, the radiation image division pattern recognition method of the present invention is effective when a recording sheet is divided into a plurality of parts and imaging is performed for each divided part. Since the division pattern is recognized by a combination of the vertical and horizontal image density distribution shapes on the recording sheet, the division pattern can be recognized very easily.

By recognizing this division pattern, more accurate reading condition 1 image processing conditions can be determined.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of a division pattern in which two radiation images are formed on the left and right sides of one sheet, and Figure 2 is a diagram showing an example of a division pattern in which four radiation images are formed in the left, right, top and bottom of one sheet. A diagram showing an example, FIG. 3 is a diagram showing the other side of a division pattern in which two radiation images are formed on the left and right sides of one sheet, and FIG. 4 is a diagram using an example of the division pattern recognition method of the present invention. FIG. 5 is a perspective view of an embodiment of an X-ray image reading device that reads an X-ray image recorded on an X-ray film, and FIG. 6 is a MOS
FIG. 2 is a circuit diagram showing an equivalent circuit of a sensor. 11.11'...Stormative phosphor sheet 11 people...
Direct radiation part ttC...center point of image 19.19'...stimulated luminescence light 21.21'...photomultiplier 2
8.28'...Logarithmic amplifier 27.27'...A/D converter 28...Storage means 29...Arithmetic means 30
...X-ray film 35...MOS sensor 50
. . . Image processing means 100 . . . Pre-reading means Th 1 . . . Threshold value 60 .

Claims (1)

[Claims] Obtain a large number of image data representing the radiographic image from a recording sheet on which the radiographic image is recorded, detect the image density distribution shape in the vertical direction and the horizontal direction on the recording sheet from the image data, and detect the distribution shape in both directions. A method for recognizing a division pattern of a radiation image, characterized in that the division pattern of the radiation image is recognized by a combination of the following.