JPH08149372A - Recording medium and radiation image correction method - Google Patents

Abstract

(57) [Summary] [Object] To provide a radiation image correction method for correcting movement unevenness when the movement unevenness occurs, and a recording medium suitable for use in carrying out the method. A radiation image is accumulated which has a plurality of markers in which the emitted light amount of stimulated emission light repeatedly changes in a sub-scanning direction at a predetermined pitch and which are parallel to each other in the main scanning direction and out of phase with each other in the change of the emitted light amount. A recording medium having a recorded photostimulable phosphor layer is two-dimensionally scanned by an excitation light beam to obtain a light reception signal, and the movement unevenness in the sub-scanning direction is obtained based on the light reception signals corresponding to the plurality of markers. To correct.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium having a photostimulable phosphor layer on which a radiation image is accumulated and recorded, and a received signal obtained by photoelectrically reading the radiation image accumulated and recorded on the recording medium. The present invention relates to a radiation image correction method for correction.

[0002]

2. Description of the Related Art Conventionally, radiographic images such as X-ray images have been widely used for disease diagnosis. Taking an X-ray image as an example, the phosphor layer (fluorescent screen) is irradiated with X-rays that have passed through the subject, whereby the X-rays are converted into visible light, and this visible light is irradiated onto the silver salt film. An X-ray image is obtained by forming a latent image and developing the latent image, and the X-ray image thus obtained is used for disease diagnosis and the like. Further, in recent years, an X-ray image obtained on a silver salt film as described above is photoelectrically read by a so-called film digitizer to obtain an image signal, and the image signal is subjected to image processing to obtain sharpness, dynamic range, A system for obtaining a reproduced image of high image quality has also been used after various image performances such as graininess that determine the image quality have been improved.

Further, instead of the system using the silver salt film, a system using a stimulable phosphor (stimulated phosphor) has begun to be used. The system using this stimulable phosphor is to irradiate a recording medium called a stimulable phosphor panel or a stimulable phosphor sheet in which the stimulable phosphor is formed into a sheet or panel shape with X-rays transmitted through an object. A system for accumulating and recording an X-ray image on the recording medium, then photoelectrically reading the X-ray image to obtain an image signal, and subjecting the image signal to image processing to obtain a reproduced image. As a basic method, US Pat.
No. 9,527. Here, the stimulable phosphor means that, when irradiated with radiation such as X-rays, α-rays, β-rays, and γ-rays, a part of the energy of the radiation is accumulated inside for a while or for a long time, and during that time, Infrared light, visible light, refers to a phosphor that emits the accumulated energy as stimulated emission light when irradiated with excitation light such as ultraviolet light, the type of radiation that easily accumulates energy depending on the type of the phosphor, The wavelength of the excitation light that easily emits stimulated emission light and the wavelength of the emitted stimulated emission light are different from each other.

In the system using the photostimulable phosphor, the energy of the radiation applied to the photostimulable phosphor is proportional to the amount of the photostimulated luminescent light emitted by the irradiation of the excitation light over a wide energy range. It is recognized that this ratio can be changed depending on the light amount of the excitation light, and therefore, a radiation image that is not affected by fluctuations in radiation exposure amount can be obtained. Further, in a system for obtaining an X-ray image of a human body, it is possible to reduce the exposure dose of the human body in X-ray photography.

FIG. 6 is a schematic configuration diagram of a radiation image reading apparatus in a system using a photostimulable phosphor. First,
In a camera (not shown), a subject is placed upright in front of the photographing table, the subject is irradiated with X-rays generated by an X-ray generation unit, and the X-rays transmitted through the subject are irradiated onto a recording medium provided in the photographing table. Thus, the X-ray image of the subject is accumulated and recorded on this recording medium.

After the image is taken in this manner, the recording medium 12 is taken out from the image taking table and set on the precision fine movement table 14 of the radiation image reading apparatus as shown in FIG. The recording medium 12 set on the precision fine movement table 14 is
While being placed on the precision fine movement table 14, it is transported (sub-scanning) in the arrow Y direction by a transporting means (not shown). Further, during this conveyance (sub scanning), the laser beam emitted from the semiconductor laser 16 is
For example, a laser beam 1 as excitation light having a wavelength of 780 nm
8 is repeatedly reflected and deflected by a scanner 20 such as a galvanometer mirror or a rotary polygonal mirror (polygon mirror), and is irradiated onto a recording medium 12 after passing through a beam shape correction optical system 22 such as an fθ lens. The laser beam 18 repeatedly scans 12 in the direction of arrow X (main scanning). From each point of this scanning, stimulated emission light carrying the X-ray image accumulated and recorded in the recording medium 12 is emitted. This stimulated emission light is condensed by the condenser 24, is guided to the photomultiplier tube 26 via an optical filter (not shown) that cuts the excitation light and passes the stimulated emission light, and Converted to a signal. The electric signal obtained by the photomultiplier tube 26 is A /
After being amplified to an optimum signal level for the D converter 30, A /
It is converted into a digital image signal by the D converter 30.
The digitized image signal is stored in the image memory 32. Then, this image signal is converted into a display luminance signal and displayed on a CRT (not shown) or output as a hard copy on a film.

Incidentally, in the radiation image reading apparatus shown in FIG.
The fine movement table 14 (recording medium 12) is moved, but the recording medium 12 is fixed and the semiconductor laser 1
The scanning optical system such as 6 and the reading system such as the photomultiplier tube 26 may be moved.

[0008]

If there is unevenness in the movement of the recording medium 12 or the scanning / reading system in the radiation image reading apparatus as shown in FIG. 6, the intervals between the scanning lines are not constant,
There is a problem that the scanning lines may be spaced apart from each other or the scanning lines may partially overlap with each other. In the past, it has been common to devise a moving mechanism so that the recording medium or the scanning / reading system moves with sufficient precision. However, since there is also a demand for high-speed reading, there is a limit in devising the moving mechanism, and even if it can be realized, there is a problem that it becomes an expensive moving mechanism.

In view of the above-mentioned circumstances, it is an object of the present invention to provide a radiation image correction method for correcting the movement unevenness when the movement unevenness occurs, and a recording medium suitable for use in carrying out the method. To do.

[0010]

The radiation image correction method of the present invention which achieves the above object, is such that the emitted light amount of stimulated emission light is repeatedly changed at a predetermined pitch in the sub-scanning direction and in parallel in the main scanning direction. Having a plurality of markers out of phase of the change in the amount of emitted light, on a recording medium provided with a stimulable phosphor layer in which a radiation image is stored and recorded, by an excitation light beam, while performing main scanning repeatedly in the main scanning direction. While scanning the recording medium two-dimensionally by relatively moving the recording medium or the excitation light beam in the sub-scanning direction, the stimulated emission light emitted from the recording medium is received to generate a light reception signal representing the radiation image. Then, based on the received light signal obtained by receiving the stimulated emission light emitted from the plurality of markers among the received light signals, the movement unevenness of the relative movement in the sub-scanning direction is corrected. And wherein the door.

Here, in the radiation image correction method of the present invention, a recording medium described below may be used, but the recording medium itself is the same as the conventional one and before the radiation image is accumulated and recorded. The marker may be recorded on the recording medium together with the radiation image by irradiating the recording medium with radiation in a state where a predetermined radiation transmitting member whose radiation transmittance repeatedly changes at a predetermined pitch is superposed on the recording medium.

The recording medium of the present invention, which can be preferably used for carrying out the radiation image correction method, has a stimulable phosphor layer on which a radiation image is accumulated and recorded, and
A plurality of markers in which the emitted light amount of stimulated emission light repeatedly changes at a predetermined pitch in a predetermined sub-scanning direction are arranged in parallel in a predetermined main scanning direction intersecting with the sub-scanning direction and the phases of changes in the emitted light amount are mutually shifted It is characterized by being formed.

Here, in the recording medium of the present invention,
It is preferable that the marker is such that the emitted light amount repeatedly changes in the sub-scanning direction at a pitch of two pixels. To form the marker on the recording medium, for example, dispersed carbon black (black ink) or the like is screen-printed.
It can be formed by coating, drying, and curing to form a light and shade pattern, or by forming a light and shade pattern on a recording medium by an etching method.

[0014]

In the radiation image correction method of the present invention, since the plurality of markers are read together with the radiation image,
Based on the light reception signals of these markers, the pitch between scanning lines, that is, the movement unevenness is known, and the light reception signal in which the movement unevenness is corrected can be obtained by, for example, interpolation calculation.

[0015]

EXAMPLES Examples of the present invention will be described below. FIG.
FIG. 3 is a schematic diagram of a recording medium. The radiation image 50 is accumulated and recorded on the recording medium 12, and two markers 51 are formed along one side of the recording medium. When the radiographic image is captured, the marker 51 is stored and recorded together with the radiographic image by disposing a predetermined radiation transmissive member together with the subject and capturing the image. Alternatively, at the time of imaging, even if the position of the marker 51 is irradiated with uniform radiation without disposing a radiation transmitting member, the accumulated energy changes into a predetermined pattern, or even if the energy is uniform. Even if energy is accumulated, the irradiation light quantity of the excitation light changes to a predetermined pattern, or even if uniform energy is accumulated and even a uniform amount of excitation light is irradiated, the brightness emitted by it The marker 51 may be built in the recording medium so that the amount of the exhausted light changes into a predetermined pattern.

In order to make such a marker 51 in a recording medium, for example, a metal plate whose thickness changes in a predetermined pattern is embedded in the recording medium, or carbon black or another dye is applied by a screen printing method. The pattern can be formed by drying, drying, and curing, or by forming a pattern of density by an etching method.

When the radiation image stored and recorded on the recording medium 12 is scanned by the laser beam 18 (see FIG. 6) to read the radiation image, the laser beam 18 is used.
Is scanned in the X direction (main scanning direction) shown in FIG. 1, and the recording medium 12 is arranged so that the recording medium or the scanning / reading system relatively moves in the Y direction (sub scanning direction).

FIG. 2 is an enlarged view of the marker in the recording medium shown in FIG. This marker 51 is two markers 51
Each of the markers 51A and 51B has an on / off repeating pattern of two pixels in the sub-scanning direction (Y direction), and each of the two markers 51A and 51B.
A and 51B are out of phase with each other by one pixel in the sub-scanning direction. Here, for simplification, the size of one pixel is 10
The width of each marker 51A, 51B is 100 μm, and the diameter of the spot 18a of the laser beam 18 is also 100 μm.

Here, the laser spot 18 at the time of reading
Consider one main scan in which a moves along one main scan line 18X. Of the received light signals for each pixel obtained by reading, the value of the received light signal when the laser spot 18a completely enters the shaded portions of the markers 51A, 51B is 100, and the markers 51A, 5 are
It is assumed that the value of the received light signal is 0 when the laser spot 18a completely enters the portion other than the hatched portion of 1B.

At this time, if the shift in the sub-scanning direction between each pixel S = 1, 2, 3, ... Of the markers 51A, 51B and the main scanning line 18X is expressed in 10% steps, it can be expressed as shown in FIG. it can. That is, when the values of the received light signals when the laser spot 18a is inside the markers 51A and 51B are D _A and D _B , respectively, when D _A = 100, D _B = 1
When 00 is obtained, the pixel shift δ between the markers 51A and 51B and the main scanning line 18X in the sub scanning direction is 0 μm, and D _B = 9.
When 0, 80, ..., 10, the pixel shift δ between the markers 51A, 51B and the main scanning line 18X in the sub-scanning direction is 10 μm, 20 μm, ..., 90 μm, respectively.

FIG. 4 is obtained from the markers 51A and 51B,
FIG. 9 is an explanatory diagram of a method for obtaining a pixel value in which the displacement amount is corrected from the displacement amounts on two continuous main scanning lines. Marker 51
The initial displacement between the pixel position in the sub-scanning direction determined by A and 51B and the position in the sub-scanning direction of the main scanning line is δ ₀ . Further, the deviation amounts of the main scanning lines corresponding to the pixels S-1 and S of the markers 51A and 51B from the pixels S-1 and S are δ _S-1 and δ _{S, respectively.}
And This shift amount can be obtained from the pixel values of the markers 51A and 51B by referring to the table shown in FIG.

In addition, on a certain pixel row arranged in the sub-scanning direction on the radiation image (excluding the portions of the markers 51A and 51B),
The pixel values before correction corresponding to the pixels S-1 and S of the markers 51A and 51B are g (s-1) and g (s). At this time, the initial deviation δ ₀ corresponding to the pixel S is larger than that of the pixel S.
The pixel value G (s) corresponding to the main scanning line deviated by

[0023]

[Equation 1]

However, δ _M represents the size of one pixel in the sub-scanning direction = 100 μm. Can be obtained by According to the equation (1), the markers 51A and 51A are provided for each main scanning line.
Shift amount from the pixels of the _{B ..., δ S-1,} δ S, even if ... are different, i.e., the recording medium when reading or even moving unevenness has occurred in the scan-reading system always markers 51A , 51B pixels and a pixel value at a position deviated by a constant initial deviation δ ₀ can be obtained. In this way,
By performing the calculation of the equation (1) on the entire surface of the radiation image, it is possible to obtain the data in which the movement unevenness is corrected.

The above equation (1) is an equation for obtaining the correction data by a linear equation, but a higher order interpolation equation may be used depending on the required accuracy. FIG. 5 is a diagram showing another mode of the markers 51A and 51B formed on the recording medium 12. The two markers 51A and 51B are arranged relatively displaced by a displacement amount δ _{L as} compared with the markers shown in FIG. Even in this case, if | δ _L | ≦ δ _M / 2 (2), the displacement can be corrected in the same manner as described above.

[0026]

As described above, according to the present invention,
It is possible to obtain a light reception signal which correctly carries the radiation image accumulated and recorded on the recording medium, in which the unevenness in feeding in the sub-scanning direction is corrected.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a recording medium.

FIG. 2 is an enlarged view of a marker in the recording medium shown in FIG.

FIG. 3 is a diagram showing a shift between a pixel of a marker and a main scanning line in a sub scanning direction.

FIG. 4 is a sequence of two obtained from markers 51A and 51B.
It is explanatory drawing of the method of calculating | requiring the pixel value by which the shift was corrected from the shift amount on the main scanning line of a book.

FIG. 5: Markers 51A and 51 formed on the recording medium 12
It is a figure which shows the other aspect of B.

FIG. 6 is a schematic configuration diagram of a radiation image reading device in a system using a stimulated phosphor.

[Explanation of Codes] 12 Recording Medium 18 Laser Beam 18a Laser Spot 18x Main Scanning Line 26 Photomultiplier 50 Radiation Image 51, 51A, 51B Marker

Claims (4)

[Claims] 1. A plurality of markers having a photostimulable phosphor layer on which a radiation image is accumulated and recorded, and a plurality of markers whose emitted light amount of photostimulated luminescence light repeatedly changes in a predetermined sub-scanning direction at a predetermined pitch in the sub-scanning direction. A recording medium, which is formed in parallel in a predetermined main scanning direction intersecting with each other and with the phases of the changes of the emitted light amounts shifted from each other. 2. The recording medium according to claim 1, wherein the marker is such that the emitted light amount repeatedly changes in the sub-scanning direction at a 2-pixel pitch. 3. A radiographic image having a plurality of markers in which the amount of stimulated emission light repeatedly changes in the sub-scanning direction at a predetermined pitch and in parallel in the main scanning direction and the phases of changes in the amount of the emitted light are shifted from each other. On the recording medium having the stimulated phosphor layer in which is accumulated and recorded, by the excitation light beam, the main scanning is repeatedly performed in the main scanning direction, and the recording medium or the excitation light beam is relatively moved in the sub scanning direction. While scanning the recording medium two-dimensionally by
The photostimulated luminescence light emitted from the recording medium is received to obtain a photodetection signal representing the radiographic image, and among the photodetection signals, photostimulation luminescence light emitted from the plurality of markers is received. A radiation image correction method characterized by correcting the movement unevenness of the relative movement in the sub-scanning direction based on a light reception signal. 4. The radiation marker is placed on the recording medium before the radiation image is accumulated and recorded on the recording medium in a state where a predetermined radiation transmitting member whose radiation transmittance repeatedly changes at the predetermined pitch is superposed on the recording medium. The radiation image correction method according to claim 3, wherein the radiation image is recorded on the recording medium together with the radiation image by irradiation.