JPH04113348A - Radiograph output device - Google Patents

Abstract

PURPOSE:To enable efficient observation by extracting a candidate for a feature point or feature area on an image and clearly indicating the extant of the probability that the candidate is the desired feature point or feature area. CONSTITUTION:A stimulable phosphor sheet 14 is set at a specific position of an X-ray image reader 20. This sheet 14 is conveyed by a sheet conveying means 22 in a Y direction. A light beam 24 emitted by a laser light source 23, on the other hand, is reflected and deflected by a rotary polygon mirror 26, a mirror 28 changes its optical path, and the light is made incident on the sheet 14 to make a main scan in an X direction. Stimulated luminous light is emitted from a place irradiated with exciting light 24, guided by a light guide 30, and detected by a photoelectron multiplier tube 31. An analog output signal SO outputted by the photoelectron multiplier tube 31 is amplified by a logarithmic amplifier 32 and digitized by an A/D converter 33 to obtain image data S1 as an electric signal, and the data is recorded on an optical disk 34 and stored.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image output device that outputs a reproduced image based on image data.

(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 output a reproduced image.

For example, recording an X-ray image using a low gamma X-ray film designed to be compatible with subsequent image processing;
The X-ray image is read from the film on which the X-ray image is recorded, converted into an electrical signal (image data), and after image processing is performed on this image data, the contrast is Efforts have been made to obtain reproduced images with good image quality performance such as sharpness and graininess (see Japanese Patent Publication No. 5193/1983).

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. Using a stimulable phosphor, radiation image information of a subject such as a human body is recorded on a sheet of 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 is recorded on a recording material such as a photographic light-sensitive material, a CRT display device, etc. A radiation image recording and reproducing system that outputs a visible image has already been proposed (Japanese Patent Laid-Open Nos. 55-12429 and 58-11).
No. 395, No. 55 (No. 63472, No. 56-10464)
No. 5, No. 55-11834 (], 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 CRT display device, it is possible to obtain a radiation image that is not affected by fluctuations in radiation exposure. can.

In recent years, systems using the above-mentioned X-ray films, stimulable phosphor sheets, etc., especially systems configured for medical diagnosis of the human body, have been used to obtain reproduced images with good image quality suitable for simple observation (diagnosis). In addition, image pattern recognition has been carried out (for example, in Japanese Patent Application Laid-open No.
(Refer to Publication No.-125481).

Image pattern recognition here refers to the operation of extracting a target pattern from a complex image by performing various processes on image data. This refers to the operation of extracting, for example, calcification shadows, tumor shadows, etc. from a very complex image containing a mixture of circular patterns.

In this way, a desired pattern (for example, a calcification shadow or a tumor shadow) is extracted from a complex radiation image (for example, a mammary X-ray image or a chest X-ray image of a human body, etc.), and a reproduced image that clearly shows the extracted pattern is created. By outputting
can be made to do so.

(Problem to be Solved by the Invention) Conventionally, the pattern extracted as described above is indicated on the reproduced image using, for example, an arrow or a circle surrounding the pattern, or the density or color of the pattern is changed. It is considered that the pattern can be made explicit by, for example, the following.

However, for example, radiation images of the human body for medical diagnosis are generally very complex images, and therefore the patterns extracted by image pattern recognition do not match the desired patterns originally intended to be extracted (for example, calcification shadows, etc.). Patterns other than tumor shadows (such as tumor shadows, etc.) often occur (for example, areas with dense blood vessels or areas where bones intersect on the image), and therefore, if the extracted patterns are uniformly output on the reproduced image, the The viewer of the reproduced image does not know which pattern to focus more on observing, and for example, it is necessary to observe all the extracted patterns in order from the end, and the extracted patterns are clearly displayed on the reproduced image. There is a problem in that this may actually reduce the efficiency of observation.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a radiation image output device that employs the Meiji method of extracting patterns, which allows an observer to perform more efficient observation.

(Means for Solving the Problems) A radiographic image output device of the present invention includes: an extracting unit for extracting candidates for feature points or feature regions on the image based on image data representing a radiographic image; and based on the image data. The apparatus is characterized by comprising an output means for clearly outputting the candidate on the reproduced image so as to include information indicating the degree of probability that the candidate is a desired feature point or feature region. .

Here, as an aspect of the present invention, the reproduction is performed by changing at least one of the size, pointing direction, shape, density, or color of the marker indicating the position of the candidate according to the degree of probability. An output means for outputting the image together with the image may be provided.

Further, as another aspect of the present invention, the output outputs a reproduced image in which at least one of the density and color of the candidate or the enlarged candidate area including the candidate and extending in the vicinity of the candidate is changed depending on the degree of probability. A means may also be provided.

In the present invention, the output means may include, for example, a laser printer that outputs the reproduced image on film, paper, etc., or may include, for example, a CRT display device that displays the reproduced image on its display screen. It may include.

Furthermore, in the present invention, the term "density" refers to a concept that also includes the "brightness" of a reproduced image when the reproduced image is displayed on, for example, a CRT display device.

In addition, the feature points or feature regions extracted by the above-mentioned extraction means are not limited to specific ones, but for example, the feature points or feature regions that appear in the X-sen image of the chest or breasts of a human body, etc. A point or area that appears characteristically on an image, such as a shadow of a calcified area (calcification shadow) or a tumor shadow (tumor shadow) of the chest or breast.

Furthermore, the method for extracting the feature point or feature region by the extraction means is not limited to a specific method, and various methods may be employed, including the method shown in the examples described later.

(Function) The present invention determines how much of a "candidate" the "candidate" extracted by the extraction means is, that is, how likely the "candidate" is to be a desired feature point, etc. (for example, the above-mentioned Since the reproduced image indicates whether it is considered to be a feature point (such as a calcified shadow or a tumor shadow in an example where the Observations can be made selectively depending on the degree of the problem, allowing for more efficient observation.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. Here, the above-mentioned stimulable phosphor sheet was used,
An example will be described in which a shadow of a calcified portion (calcification shadow) that typically occurs in a human breast as a substantially spherical shape with a diameter of approximately IMn is extracted. This calcified shadow appears on a visible image as a substantially circular pattern that is whitish (higher brightness or lower density) than the surrounding area.

FIG. 1 is a schematic diagram of an example of an X-ray imaging apparatus.

X-rays 12 are irradiated from the X-ray source 11 of the X-ray imaging device 10 toward the breast 13a of the human body 13, and the X-rays 12a that have passed through the human body 13 are irradiated to the stimulable phosphor sheet 14. The transmitted X-ray image of the breast 13a is the breast 13
The light is accumulated and recorded on the stimulable phosphor sheet 14 at approximately the same magnification as that of a.

FIG. 2 is a perspective view showing an example of an X-ray image reading device.

A stimulable phosphor film 14 on which an X-ray image has been recorded is set at a predetermined position in the X-ray image reading device 20.

The stimulable phosphor sheet 14 set at a predetermined position is transported in the direction of arrow Y (sub-scanning) by a sheet transport means 22 such as an endless belt driven by a motor 21.
be done. On the other hand, the light beam 24 emitted from the laser light source 23 is reflected and deflected by a rotating polygon mirror 26 that is driven by a motor 25 and rotates at high speed in the direction of the arrow, passes through an fθ lens 27, and then changes its optical path by a mirror 28 to form a sheet 14. , and main scanning is performed in the direction of arrow X, which is substantially perpendicular to the direction of sub-scanning (direction of arrow Y). Stimulated luminescence light 29 is emitted from the part of the sheet 14 that is irradiated with the excitation light 24, and the amount of stimulated luminescence light 29 corresponds to the stored and recorded X-ray image information, and this stimulated luminescence light 29 is guided by the light guide 30. , are photoelectrically detected by a photomultiplier (photomultiplier tube) 31. The light guide 30 is made by molding a light guiding material such as an acrylic plate, and has a linear entrance end surface 3.
0a extends along the main scanning line on the stimulable phosphor sheet 14, and the emission end surface 30b is formed in an annular shape.
The light receiving surface of the photomultiplier 31 is coupled to the photomultiplier 31 . The stimulated luminescent light 29 that enters the light guide 30 from the entrance end surface 30a travels through the interior of the light guide 30 through repeated total reflection, exits from the exit end surface 30b, and is received by the photomultiplier 31, forming an X-ray image. Stimulated luminescent light 29 representing
is converted into an electrical signal by the photomultiplier 31.

The analog output signal SO output from the photomultiplier 31 is logarithmically amplified by the logarithmic amplifier 82, and the A/D
The data is digitized by a converter 33, and image data S1 as an electrical signal is obtained. In this embodiment, image data S1 sampled at intervals of OAmm is generated in each of the main scanning direction and the sub-scanning direction. This image data S1 is recorded and saved on the optical disc 34.

FIG. 3 is a perspective view showing the external appearance of one embodiment of the image output device of the present invention, and FIG. 4 is a perspective view showing the image output device shown in FIG. FIG.

The image output device 40 shown in FIG. 3 includes an optical disk 34 (see FIG. 2) that stores a large number of image signals S1 corresponding to a large number of X-ray images obtained by the ) is loaded and driven by an optical disk drive unit 4LCP.
A main body part 42 that has a built-in U, internal memory, etc. A floppy disk drive unit 431 in which a floppy disk as an auxiliary memory is loaded and driven
CRT display 44 for displaying line images. It consists of a keyboard 45 through which an operator inputs various commands and information, and the image output device 40, except for the optical disk drive section 41, is placed on a table 46.

As shown in FIG. 4, image data S1 is read out from the optical disk 34 by the optical disk drive section 41 and input to the gradation/frequency processing section 42a and the high frequency emphasis processing section 42b.

In the gradation/frequency processing section 42a, the CRT display 4
The input image data S1 is subjected to gradation conversion processing and various frequency processing calculations so that the visible image displayed in 4 becomes an image with excellent viewing suitability. Note that these calculations are executed using the CPU etc. built into the main body section 42 shown in FIG.
1. The combination of hardware and software that performs the above-mentioned gradation conversion processing calculations and various frequency processing calculations is the gradation and
It can be considered as a frequency processing section 42a. Gradation conversion processing.

The image data S2 subjected to frequency processing is input to the CRT display 44, and a visible image based on the image data S2 is displayed on the CRT display 44.

The high frequency enhancement processing section 42b performs high frequency enhancement processing on the input image data S1 in the following manner.

In this example, the target is the extraction of calcified shadows that appear in mammary ]-mm or less is extracted.

The coordinates of each pixel on the X-ray image are (x, y), and each pixel (X
, y), the evaluation function g(x, y) is defined as g(x, y) − 3×3, and this evaluation function g(x , y) to scan the X-ray image. Equation (1) expresses the pixel of interest (x,
The pixel (x, y) is calculated from the average value of image data of 3 pixels (total 9 pixels) arranged in each direction of x and y with pixel (x, y) as the center.
9 pixels lined up in each direction of x and y centering on (81 pixels in total)
This indicates that the average value of the image data of pixels) is subtracted.

Figure 5 shows the spatial frequency (cycles/mm) of equation (1) above.
) is a diagram showing the response characteristics for

As mentioned above, the image data S1 targeted here is 0.1. Equation (1) has a response characteristic suitable for extracting a calcified shadow having a diameter of approximately 1rrR or less and greater than noise.

After scanning the X-ray image using the evaluation function g(x, y), the evaluation function g(x, y) is determined by the threshold processing unit 42c.
is input to , and the magnitude is compared with the threshold value Thl, g(x, y)≧Thl...(2)
Pixels that satisfy the following are extracted. Each pixel extracted in this manner is an example of a feature point or a feature region according to the present invention. Although the threshold value Thl is input in advance from the threshold setting section 45 and stored in the threshold processing section 42c, it can be changed arbitrarily by operating the threshold setting section 45.

In this embodiment, threshold processing is also one of the arithmetic processing performed within the main unit 42 shown in FIG. 3, and the combination of hardware and software that performs this threshold processing is the threshold processing unit. It is considered to be 42c. Further, the threshold value setting section 45 refers to the keyboard 45 shown in FIG. Furthermore, in this embodiment, the high frequency emphasis processing section 42b, the L threshold processing section 42c, and the threshold setting section 45 are collectively considered as the extraction means according to the present invention.

Extraction is performed as described above, and the position information of each pixel satisfying the above ('2J formula) is input to the image brightness switching section 42d, and the image brightness switching section 42d selects the above-mentioned g (
The brightness of the point or area corresponding to the extracted pixel of the visible image displayed on the CRT display 44 is increased so that the larger the value of x, y) is, the higher the brightness is. In this embodiment, the image brightness switching section 42d is also realized by a combination of hardware and software within the main body section 42.

Here, the brightness of a corresponding point or area on the visible image displayed on the CRT display 44 may be increased only while a specific key on the keyboard 45 is pressed, or when a key on the keyboard 45 is pressed once. Even if you release your hand immediately after pressing the key, the brightness may be increased for a certain period of time from the time the key is pressed, and then returned to the brightness of light. Here, the higher the brightness, the larger g(x, y), and therefore the higher the probability that it is a calcified shadow, so the observer only needs to concentrate on observing points or areas with high brightness. Observation becomes possible.

In the above embodiment, by increasing the brightness of the point or area on the visible image corresponding to the extracted pixel, the point or area is made clear, and furthermore, depending on the degree of increasing the brightness, the point or area is calcified. Although the probability of being a shadow is shown here, instead of increasing the brightness, the color of the point or area may be changed depending on the probability of being a calcification shadow, and the point or area may be displayed in a circle. The size, color, etc. of the circle or frame may be used to indicate the probability that the point or area is a calcified shadow. It can be indicated by different arrows (, it can be clearly indicated by these various methods. Also, the extraction of calcified shadows and the probability that the extracted calcified shadows are truly calcified shadows are determined. The calculation for is not limited to the calculations of equations (1) and (2) above, but other calculations may be used.

Furthermore, the feature points or feature regions of the present invention are not limited to calcified shadows as described above.

Next, an example of a method for extracting a tumor shadow that appears as a substantially circular pattern on an X-ray image as a feature point or feature region will be described (see Japanese Patent Application No. 1-162909).

FIG. 6 is a diagram virtually drawn on an X-ray image centering on a predetermined pixel Po on the X-ray image in order to explain a spatial filter for extracting a tumor shadow.

As shown in FIG. 6, a plurality of (eight in this case) line segments L+ (i-1, 2,..., 8) extend from a predetermined pixel Po in the X-ray image to the periphery of the X-ray image. Assuming that, each radius '1+
Three circles R+ (j = 1.2.3
) is assumed. Predetermined pixel P. Qo is the central region containing
and each pixel P located at each intersection of each line segment L1 and congruence R4 (in Fig. 6, PII + p, □ + P13 + P5
Symbols are shown for 1+ P52+ P53. ) is defined as Q1+ (j=1.2...
, 8. j=12.3) (However, in Figure 6, Qo and Qllll Q121 Q131 Q5 are explicitly shown.
1. Q521 Only Q53 is shown. ).

Each region Qo and Q, (i = 1, 2.-.8; j
=1,2.3), the average value Qo of a large number of each image data corresponding to a large number of pixels in each region Qo, Q,
Q1+ (i = 1, 2.-.8; j = 1, 2
．． 3) is required. Here, for the sake of simplicity, each area Q. , Q'' (i = 1, 2..., 8, j =
1.2.3) The same symbol is used for the symbol indicating the average value of the image data in each region.

Next is the average value Q of the central area. and the average value Q'+ of each surrounding area
+ and each difference ΔII (j = 1, 2...
. , 8.j = L2,3) is obtained as Δ, I = 0.1-QO-(3), and for each line segment L1, the difference Δ1. The maximum value Δ1 of is determined.

Next, the first characteristic value U representing the maximum value Δ1 (i=1 to 8) and the second characteristic value ■ representing the maximum value Δ+(i=4 to 8) with 9 pieces are determined. . For this purpose, first, each characteristic value U1 to U4 +
v1 to ■4 are required.

U1=(Δ1+Δ2+Δ5+Δ6)/4...(4)
U2-(Δ2+Δ3+Δ6+Δ7)/4...(5)
U3-(Δ3+Δ4+Δ7+Δ8)/4...(6)
U4=(Δ4+Δ5+Δ8+Δ1)/4...(7)
V1 = U1/Ua
−(8) Vz = U2 / Ua
---(9) V3=U3/U,
...(10) v4=U, /U2
...(11) Here, for example, when calculating the characteristic value Ul according to equation (4),
Two adjacent areas (Δwork and Δ2, or Δ5 and Δ6)
Adding for the pixels means smoothing, and adding for regions on opposite sides of the pixel Po (Δ1+Δ2 and Δ5+Δ6) means that even if there is a tumor shadow in an area with a density gradient, the tumor shadow can be detected. This is to make it possible to do so.

Furthermore, for example, to explain the case where characteristic value v1 is determined according to equation (8), characteristic value U1 and characteristic value U3 are characteristic values determined in directions perpendicular to each other, so if the tumor shadow is circular, V1→1 , 0 and deviates from the circle, vl deviates from 1.0.

The first characteristic value U representing the maximum value Δ+ (i=1 to 8) of the above difference is the maximum value U=MAX of U1 to U4.
(Ul, Uz, U3, Ua)...
(12) is adopted, and the maximum value of the above difference Δ+(j=1~
The second characteristic value V representing the variation in 8) is 1
~V4 maximum value V-MAX (Vt, V2, V3. Va
) −(13) is adopted. When the first and second characteristic values U and V are obtained in this way, these first and second characteristic values C2 are used to determine whether a predetermined pixel Po is a pixel within a tumor shadow. The ratio of the two characteristic values...(14) (1) is adopted, and this characteristic value 02 is compared with a predetermined threshold Th2, and depending on whether C2≧Th2 or C2<Th2, the pixel Po is It is determined whether each pixel is within a tumor shadow. Moreover, even if C2≧Th2, C2
The larger the value, the higher the probability that it is a tumor shadow. By scanning the X-ray image using this spatial filter in the extraction means (see Figure 4),
Tumor shadow extraction is performed.

In each of the above filter examples, each peripheral area Q including pixels P on eight line segments L1 to L8 as shown in FIG.
Although the Q-th average value of the image data corresponding to +i is used, the number of line segments need not be 8, and of course may be 16, for example. Also here rl+
Although calculations were performed for three distances rZ + r3, this is not limited to three distances,
In order to extract tumor shadows of various sizes with higher precision, calculations may be performed while continuously changing the distance from rl to r3.

The tumor shadow extracted in this manner is clearly displayed on the visible image in the same manner as in the embodiment shown in FIG.

Of course, the extraction of tumor shadows is not limited to extraction using the above-mentioned filter. Method of scanning an X-ray image using a filter, patent application No. 1-162909
A method of scanning an X-ray image using a real space filter that extracts a circular pattern from the value of a component of the gradient of density of an image surrounding a predetermined point in the direction of the predetermined point, etc. described in the No. , various methods can be adopted.

Each of the above embodiments is an example of extracting a calcified shadow or a tumor shadow that typically appears as a circle in a mammary X-ray image of a human body obtained using a stimulable phosphor and clearly showing it on a visible image. However, the feature points or feature regions of the present invention are not limited to calcification shadows or tumor shadows, and are not limited to CRT shadows or tumor shadows.
It does not have to be something that displays images on a display;
For example, it may be a device that outputs a hard copy of an image on film, paper, etc., and is widely applied to various image output devices that output general radiographic images to clearly indicate various characteristic points or characteristic regions. It is.

(Effects of the Invention) As explained in detail above, the radiation image output device of the present invention extracts candidates for feature points or feature regions on an image, and determines the probability that the candidates are the desired feature points or feature regions. Since the extracted candidates are clearly displayed so as to include information on the images, and a reproduced image based on the image data is output, the viewer can pick up and observe only highly probable candidates as necessary. , efficient image observation becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of an X-ray image capturing device, FIG. 2 is a perspective view of an example of an X-ray image reading device, and FIG. 3 is a schematic diagram of an example of an image output device of the present invention. FIG. 4 is a block diagram showing the function of the image output device shown in FIG. 3 as an embodiment of the present invention; FIG. 5 is a perspective view showing the appearance of the image output device; FIG. y) spatial frequency (
Figure 6 shows the response characteristics for cycles/mm).
The figure is a diagram virtually drawn on an X-ray image centered on a predetermined pixel P, in order to explain a spatial filter for extracting a tumor shadow. DESCRIPTION OF SYMBOLS 10... X-ray imaging device 14... Storable phosphor sheet 20... X-ray image reading device 23... Laser light source 26... Rotating polygon mirror 29
... Stimulated luminescence light 30 ... Light guide 31 ...
Photo multiplier 40... Image output device 41... Optical disk drive section 42... Main body section 44... CRT display 45... Keyboard

Claims (3)

[Claims] (1) Extracting means for extracting candidates for feature points or feature regions on the image based on image data representing a radiation image; and feature points or features desired by the candidates on a reproduced image based on the image data. 1. A radiation image output device comprising: output means for clearly outputting the candidate so as to include information representing the degree of probability of the region. (2) The output means changes at least one of the size, pointing direction, shape, density, or color of the marker indicating the position of the candidate according to the degree of probability to reproduce the reproduced image. 2. The radiation image output device according to claim 1, wherein the radiation image output device outputs the radiation image at the same time as the radiation image output device. (3) The output means outputs a reproduced image in which at least one of the density and color of the candidate or an enlarged candidate area including the candidate and expanding in the vicinity of the candidate is changed depending on the degree of probability. The radiation image output device according to claim 1, characterized in that: