JPH03279936A - Radiation image display method - Google Patents

Abstract

PURPOSE:To erase a specific point and to prevent an error in judgment by inputting a specific point position signal, determining an interpolation image signal from the image signal corresponding to the picture elements around the specific point, replacing the original image signal corresponding to the specific point with the interpolation image signal and displaying a visible image. CONSTITUTION:The region corresponding to the defect is determined in accordance with a bar code signal SB or monitor signal SM and interpolation computation is made in accordance with the image signal around this region. The interpolation image signal corresponding to the respective picture elements within this region is determined. The visible image based on the image signal replaced with the interpolation image signal by making interpolation computation is reproduced and displayed at the time of reproducing and displaying the image on a CRT display 44 as a visible image. The pattern occurring in the defect is erased and the visible image carrying only the useful image information is eventually displayed in this way and the error in the judgment in the observation of the visible image is prevented.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a method for generating visible images based on image signals obtained by reading stimulated luminescence light emitted from a stimulable phosphor sheet on which radiation images are stored and recorded. The present invention relates to a radiation image display method.

(Conventional technology) Radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.)
When irradiated with , some of this radiation energy is accumulated,
A stimulable phosphor (stimulable phosphor) is known that exhibits stimulated luminescence depending on the accumulated energy when it is then irradiated with excitation light such as visible light.

Using this stimulable phosphor, radiation image information of a subject such as a human body is recorded once on a sheet of stimulable phosphor, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam to stimulate the image. Generate luminescent light, read the obtained stimulated luminescent light in a charging manner 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, or a CRT.
The present applicant has proposed a radiation image recording and reproducing system that outputs a visible image to
No. 429, No. 56-11395, No. 55-18347
No. 2, No. 5B-104845, No. 55-118340
No. etc.).

This system has the practical advantage of being able to record images over a much wider range of radiation exposures than 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.

(Problems to be Solved by the Invention) In the system using the above-mentioned stimulable phosphor sheet, for example, non-luminous impurities may be mixed in the phosphor raw material, or dust may be mixed in during the production of the stimulable phosphor sheet. Due to this, there may be minute defects on the surface or inside of the stimulable phosphor sheet as a finished product that cannot be removed by cleaning, etc. Also, photographs may be taken with dust attached to the surface of the stimulable phosphor sheet. , reading may be performed. In these cases, not only the image information of that part is lost, but also the pattern on the radiographic image caused by the defect or dust (hereinafter collectively referred to as "defect") and the necessary information on the radiographic image are lost. It is difficult to distinguish it from information, which may lead to errors in judgment when observing images.

For example, an X-ray image of a human breast is stored and recorded on the stimulable phosphor sheet, an electrical signal representing the X-ray image is obtained, and based on the electrical signal, the X-ray image is displayed as a visible image on a CRT display device or the like. One of the criteria for reproducing and outputting images to diagnose whether or not it is breast cancer is the presence, number, density, etc. of calcification, which appears as white spots with an average diameter of about 300 μm on the X-ray image. However, if there is a defect such as dust on the surface or inside of the stimulable phosphor sheet, the image information of that part will be lost due to the influence of the defect, and as a result, the reproduced visible image will appear white. It often appears as spots and is difficult to distinguish from the above-mentioned calcification, so there is a possibility that it may be misdiagnosed as a possible breast cancer even though calcification does not actually exist. There is.

In view of the above circumstances, an object of the present invention is to provide a radiation image display method capable of erasing from a visible image a pattern that appears in a radiation image due to a defect on the surface or inside of a stimulable phosphor sheet. It is something to do.

(Means for Solving the Problems) The radiation image display method of the present invention is characterized by irradiating excitation light onto a stimulable phosphor sheet on which a radiation image has been accumulated and recorded, thereby detecting the stimulable phosphor sheet emitted from the stimulable phosphor sheet. When displaying a visible image based on an image signal obtained by reading emitted light, the position of a singular point that appears in the radiation image carried by the image signal due to a defect on the surface or inside of the stimulable phosphor sheet is determined. A singular point position signal representing the singular point is input, and an interpolated image signal corresponding to the singular point is obtained by performing an interpolation operation based on image signals corresponding to pixels around the singular point. The present invention is characterized in that the image signal is replaced with the interpolated image signal, and a visible image is displayed based on the replaced image signal.

Further, in the present invention, the method of obtaining the singular point position signal is not limited to a specific method, but it can be obtained, for example, as in the embodiment described later.

(Function) The radiation image display method of the present invention inputs a singular point position signal and performs an interpolation calculation based on image signals corresponding to pixels around the singular point, thereby producing an interpolated image signal corresponding to the singular point. Since the visible image is displayed based on the image signal replaced by this interpolated image signal, the pattern caused by the above defect is erased from the visible image, and the visible image carrying only useful image information is created. This prevents errors in judgment when observing visible images.

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

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. A transmitted X-ray image of the breast 13a is accumulated and recorded on the stimulable phosphor sheet 14.

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

The stimulable phosphor sheet 14 on which the X-ray image has been recorded is moved in the direction of arrow Z shown in the figure and set at a predetermined position in the reading section 20. The stimulable phosphor sheet 14 set at a predetermined position is conveyed (sub-scanned) in the direction of arrow Y by a sheet conveying means 22 such as an endless belt driven by a motor 21. On the other hand, a light beam 24 emitted from a laser light source 23 is reflected and deflected by a rotating polygon mirror 2B that is driven by a motor 25 and rotates at high speed in the direction of the arrow.
After passing through a focusing lens 27 such as an fθ lens, the mirror 2
8, the optical path is changed and the light enters the 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).

A portion of the stimulable phosphor sheet 14 irradiated with the excitation light 24 emits stimulated luminescence light 29 in an amount corresponding to the accumulated and recorded X-ray image information, and this stimulated luminescence light 29 is transmitted to the light guide. 30 toward the injection end surface 30b. The light guide 30 is made by molding a light guide material such as an acrylic plate, and its entrance end surface 30a is formed in a straight line so as to extend along the main scanning line on the stimulable phosphor sheet 14. The injection end surface 30b is formed in an annular shape. An optical filter 3 is provided on the exit end surface 30b for transmitting the stimulated luminescence light 29 and blocking the excitation light 24.
The light-receiving surfaces of a photomultiplier 32 are coupled to each other with the photomultiplier 32 in between.

The stimulated luminescence light 29 that enters the light guide 30 from the input end face 30a travels through the light guide 30 through repeated total reflection, exits from the exit end face 30b, passes through the optical filter 31, and enters the photomultiplier 32. The received stimulated luminescence light 29 representing an X-ray image is converted into an electrical signal by a photomultiplier 32 .

The analog output signal SA output from the photomultiplier 32 is logarithmically amplified by the logarithmic amplifier 33, and the A/D
The signal is digitized by a converter 34, and an image signal S□ is obtained as an electrical signal.

The obtained image signal SD is input to the signal processing section 40. This signal processing section 40 includes a main body section 41. A drive section 42 into which a floppy disk as auxiliary memory is inserted and driven. A keyboard 43 for the operator to input necessary instructions to the signal processing section 4o. and a CRT display 44 for displaying visible images and necessary information based on the image signal SD.

The image signal SD input to the signal processing unit 40 is subjected to, for example, data compression processing as necessary, and sent to an image filing device (not shown) that stores radiographic images in the form of image signals. Alternatively, the image signal So is subjected to image processing such as frequency emphasis processing, smoothing processing, contrast conversion processing, etc., and is reproduced and displayed on the CRT display 44 as a visible image.

Note that the reading section 20 includes a light guide 35. A 20th photoelectric conversion means consisting of a photomultiplier 37, etc., and a barcode 51a or barcode 51b attached to the stimulable phosphor sheet 14 before the stimulable phosphor sheet 14 is set in the reading section 2o. Barcode reader 5 to read
2, which will be described later.

Note that this barcode 51a51b is attached to the back surface of the stimulable phosphor sheet 14.

FIG. 3 is a diagram showing an example of an X-ray image of a breast reproduced and displayed on a CRT display.

Spots 15a and 15b, which are whitish compared to the surrounding area and have an average diameter of about 300 μm, appear in the shadow 13a' of the breast. Here, the distinction between spots 15a and spots 15b will be described later. These whitish spots 15a.

15b is mainly caused by calcification in the breast, and its number, density, etc. are the basis for diagnosis of breast cancer. However, it is possible that these spots are patterns that appear on the X-ray image due to defects on the surface or inside of the stimulable phosphor sheet 14, and thus it is unclear whether these spots are due to true calcification or not. If the distinction cannot be made, it may be impossible to make a confident diagnosis.

Therefore, in this embodiment, the stimulable phosphor sheet 14, which cannot be removed even by cleaning the stimulable phosphor sheet 14, is removed by performing the preparations described below before performing the X-ray imaging and reading of the breast as described above. The presence or absence of defects on the surface or inside of 14 and their positions are examined. Further, a monitor signal sM is obtained by a second photoelectric conversion means comprising a light guide 35° photomultiplier 37, etc. provided in the reading section 20 of the X-ray image reading device shown in FIG. The presence or absence of defects (for example, dust attached to the surface of the stimulable phosphor sheet 14) inherent in photographing and reading, which can be removed by cleaning, and their positions are checked.

FIG. 4 is a diagram showing an example of an X-ray imaging apparatus similar to that in FIG. 1.

By keeping the distance between the X-ray source 11 and the stimulable phosphor sheet 14 as far as possible, and irradiating the stimulable phosphor sheet 141 with X-rays 12 without placing a subject etc. in the middle, the stimulable phosphor sheet 14 is The entire surface of the body sheet 14 is irradiated with X-rays 12 having approximately -like energy. The state accumulated and recorded on the stimulable phosphor sheet 14 by uniformly irradiating the entire surface of the stimulable phosphor sheet 14 in this way is likened to an image, and the stimulable phosphor sheet 14 is uniformly exposed. It is assumed that the image is stored and recorded.

After the uniform exposure image is stored and recorded on the stimulable phosphor sheet 14, the stimulable phosphor sheet 14 is set at a predetermined position in the reading section 20 of the X-ray image reading device shown in FIG. In this way, the image signal SD is obtained and input to the signal processing section 40. Here, the image signal So is a signal carrying a uniform exposure image, and the signal processing unit 40 detects the presence or absence of defects on the surface or inside of the stimulable phosphor sheet 14 and their positions in the following manner. Ru.

FIG. 5 is a diagram showing a uniform exposure image signal SOO along a certain main scanning direction (X direction shown in FIG. 2).

Since the uniform exposure image signal SDO carries the uniform exposure image accumulated and recorded on the stimulable phosphor sheet 14, the --like exposure image signal sDo usually corresponds to each part of the stimulable phosphor sheet 4. It is a substantially constant value (A we) regardless of the

If a defect exists on the surface or inside of the stimulable phosphor sheet 14, the amount of stimulated luminescence light emitted from the defective portion decreases, and as a result, uniform exposure is performed as shown by symbol A in FIG. The value of the image signal SDO decreases. Therefore, an area where the predetermined threshold value Ave- is lower than 1 is determined for each main scan.

FIG. 6 is a diagram schematically showing each pixel of a part of the --like exposure image.

As described above, the uniform exposure image signal SDO is generated for each main scan.
It is determined whether is above or below the threshold value Ave-Kt, and SM
It is determined that the region (shaded region in the figure) consisting of each pixel of <Ave-Kt corresponds to a defect in the stimulable phosphor sheet 14.

FIG. 7 is a diagram schematically showing a stimulable phosphor sheet. In FIG. 7, it is assumed that the 0 mark indicates the position of the defect.

When the presence or absence of a defect in the stimulable phosphor sheet 14 and its position on the stimulable phosphor sheet 14 are detected in the above manner, the barcodes 51a and 51b attached to the back surface of the stimulable phosphor sheet 14 and The correspondence with the defect position information is stored in the signal processing unit 4o.

Here, the stimulable phosphor sheet 14 is used when the stimulable phosphor sheet 14 is set in the X-ray image reading device shown in FIG.
Depending on the direction of the paper 4, the paper may be transported (sub-scanning) in the direction of the arrow Y1 shown in FIG. 7 or may be transported in the direction of the arrow Y2. Since the position of the defect differs depending on which direction of the arrows Y1+Y2 the barcodes are transported (sub-scanning), different information is attached to the two barcodes 51a and 51b. When the barcode 51b is scanned (sub-scanning), the barcode 51b is scanned by the barcode reader 53 (second scanning).
When the barcode 51a is read by the barcode reader 52 and is transported in the arrow Y2 direction, the barcode signal S3 obtained thereby specifies the transport direction of the stimulable phosphor sheet. The position of the defect in the stimulable phosphor sheet 14 corresponding to the transport direction is determined.

Next, an example of a method for detecting the presence or absence of a defect made of dust or the like attached to the surface of the stimulable phosphor sheet 14, which can be removed by cleaning or the like, and the position thereof will be described.

During reading, a part of the excitation light 24 that has irradiated the stimulable phosphor sheet 14 is reflected from the sheet 14, enters the light guide 35 from the entrance end surface 35a, travels inside the light guide 35, and reaches the exit end surface 35b. an optical filter 3 that transmits the excitation light 24 and blocks the stimulated luminescence light 29;
The excitation light 24 is incident on the photomultiplier 37 via the photomultiplier 6, and the excitation light 24 is photoelectrically detected by the photomultiplier 37. The analog signal sA output from this photomultiplier 37 is logarithmically amplified by a logarithmic amplifier 38, digitized by an A/D converter 39,
The signal is input to the image processing section 4o as a monitor signal SN.

The stimulable phosphor sheet 14 is irradiated with a constant amount of excitation light 24 that does not change over time, and therefore the amount of excitation light 24 that is reflected from the stimulable phosphor sheet 14 and enters the light guide 35 is also generally approximately constant. Become. If dust or the like adheres to the surface of the stimulable phosphor sheet 14, the excitation light 24 that irradiates the stimulable phosphor sheet 14 will be scattered by the dust or the like, and the amount of excitation light 24 that will enter the light guide 35. decreases,
The value of monitor signal sM decreases. Therefore, by using the monitor signal sM instead of the -like exposure image signal SDO and performing calculations similar to the method explained using FIGS. The presence or absence of dust, etc. and its location can be known.

In this embodiment, as described above, the barcode signal S8
As a result, it is possible to know the presence or absence of defects on the surface or inside of the stimulable phosphor sheet 14 that cannot be removed by cleaning or the like, as well as their positions.By performing calculations based on the monitor signal sM, the stimulable phosphor sheet 14 It is possible to know the presence or absence and location of defects inherent in photographing and reading, which can be removed by cleaning or the like, such as dust attached to the image. Therefore, in this embodiment, the barcode signal sB and the monitor signal sM correspond to the singular point position signal according to the present invention.

FIG. 8 is a diagram schematically showing each pixel of a part of the X-ray image of the breast carried by the image signal SD.

The shaded area in the figure is the area corresponding to the defect in the stimulable phosphor sheet determined as described above, and therefore the image signal So within this area does not accurately represent image information. Also, as shown in this figure, the image signals SD corresponding to each pixel around this area are a, (
i=1.2°..., 9;j-1,2).

The image signal SD carrying the X-ray image of the breast is transmitted to the signal processing unit 4
0, the area corresponding to the defect is determined based on the barcode signal sB or the monitor signal sM (area A' shown in FIG. 8), and the image signal a1 around this area is determined.
．． An interpolated image signal a corresponding to each pixel in this area is obtained by performing an interpolation calculation based on . This interpolation calculation method is not limited to a specific compensation calculation method, but for example, the average value of image signals corresponding to each surrounding pixel is determined, and this average value a, pixel interpolated image signal a. used as.

Further, as another example of the interpolation calculation method, -dimensional interpolation may be performed in the main scanning direction (X direction shown in FIGS. 2 and 8). For example, the interpolated image signal a8 of pixel C is obtained as 3, a, , +2 a32 a ll 婂・BEGG.

Further, as a further example of the interpolation calculation method, -dimensional interpolation may be performed in each of the main scanning direction (X direction) and the sub-scanning direction (Y direction), and the average value thereof may be used. In this case, the interpolated image signal a9 of pixel C is the interpolated image signal a in the X direction obtained by the above equation (2).
! The average value of the Y-direction interpolated image signal a obtained by the following equation (3) is adopted.

Here, the interpolation calculation method is not limited to each of the above-mentioned interpolation calculation methods, and a higher-order interpolation calculation method or the like may be adopted.

When the interpolated image signal is obtained as described above, the original image signal S is obtained for the area corresponding to the defect.

is replaced with the obtained interpolated image signal.

The whitish spots 15b shown in FIG. 3 indicate the singular points found as described above. When reproducing and displaying the breast X-ray image as a visible image on the CRT display 44, by performing the interpolation calculation as described above and reproducing and displaying the visible image based on the image signal replaced with the interpolated image signal, calcification is performed. Only the spots 15a are displayed, thus preventing misdiagnosis.

It should be noted that an image in which the spots 15b caused by defects are always removed may be displayed, and the operator can use the keyboard 4 to
It may also be erased when instructed using 3.

Furthermore, instead of displaying an image on the CRT display 44, when a visible image is reproduced and output on a film, an image with spots caused by defects removed may be output.

FIG. 9 shows the differential value 5DOs of the uniformly exposed image signal SDO along the main scanning direction (X direction) in order to show another method of determining the presence or absence and position of defects on the surface or inside of the stimulable phosphor sheet. Or the differential value SM' of the monitor signal sM
FIG.

When differentiated along the X direction in the figure, a downward peak a1 occurs at the front end of portion A corresponding to the defect, and an upward peak a2 occurs at the rear end. Therefore, these peaks aina2 are compared with the threshold value ±2, and the front and rear ends of the region corresponding to the defect are determined.

Similar to FIG. 6, FIG. 10 is a diagram schematically representing each pixel of a part of the X-ray image accumulated and recorded on the stimulable phosphor sheet.

The front end for each main scan using the detection direction described above.

When the rear end is determined, the pixels corresponding to the front end and the rear end are, for example, the hatched pixels in FIG. 10. Therefore, the area surrounded by each pixel corresponding to the front end and the rear end is determined to be a portion corresponding to a defect.

Although the above embodiment describes an X-ray image of a human breast, the object to be photographed is not limited to a human breast, and is not limited to an X-ray image. The present invention can also be applied to an electron microscope system, etc. that accumulates and records images.

(Effects of the Invention) As explained in detail above, the radiation image display method of the present invention inputs a singular point position signal and performs interpolation calculation based on image signals corresponding to pixels around the singular point. find an interpolated image signal corresponding to the singular point, replace the original image signal corresponding to the singular point with the interpolated image signal,
Since the visible image is displayed based on this replaced image signal, even if a singular point exists, it will be erased from the reproduced visible image, preventing errors in judgment due to the presence of the singular point. Ru.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of an X-ray imaging device, and FIG.
FIG. 3 is a perspective view showing an example of a radiation image reading device; FIG. 3 is a diagram showing an example of a breast X-ray image reproduced and displayed on a CRT display; FIG. A schematic diagram of an example of an imaging device, FIG. 5 is a diagram showing a uniform exposure image signal SDO along the main scanning direction (X direction shown in FIG. 2), and FIG. 6 is a diagram showing a uniform exposure image signal SDO along the main scanning direction (X direction shown in FIG. FIG. 7 is a diagram schematically showing each pixel of a part of the uniform exposure image stored and recorded. FIG. 7 is a diagram schematically showing a stimulable phosphor sheet. FIG. FIG. 9 is a diagram schematically representing each pixel of a part of an X-ray image of a breast. Main scanning direction (X direction)
The first diagram shows the differential value SDo of the uniform exposure image signal SDO along the line or the differential value SM' of the monitor signal sM.
Similar to FIG. 6, FIG. 0 is a diagram schematically representing each pixel of a part of an X-ray image accumulated and recorded on a stimulable phosphor sheet. lO...X-ray imaging device 14...Stormable phosphor sheet 20...Reading section 24...
...excitation light 26...rotating polygon mirror 30,
35...Light guides 31, 36...Optical filters 32, 37...Photomultiplier 40...Signal processing unit Fig. 4 Fig. Fig. 500 (SM) Fig. 9 Fig. 0

Claims (1)

[Claims] When displaying a visible image based on an image signal obtained by reading the stimulated luminescence light emitted from the stimulable phosphor sheet by irradiating the stimulable phosphor sheet on which a radiation image has been accumulated and recorded with excitation light, A singular point position signal representing the position of a singular point that appears in the radiation image carried by the image signal, which is caused by a defect on the surface or inside of the stimulable phosphor sheet, is input, and pixels around the singular point are An interpolated image signal corresponding to the singular point is obtained by performing an interpolation operation based on the corresponding image signal, the image signal corresponding to the singular point is replaced with the interpolated image signal, and based on the replaced image signal, 1. A radiation image display method characterized by displaying a visible image.