JPS63259500A - Radiation picture conversion panel and radiation picture reading method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radiation image conversion panel and a method for reading out radiation images stored in the panel, and in particular to a radiation image conversion panel and a method for reading radiation images stored in the panel. The present invention relates to a radiation image conversion panel and a radiation image reading method that are suitably applied to a method of reading a radiation image by storing the phosphor and detecting the movement of charges generated by irradiating the phosphor with excitation energy.

[Prior art and its problems] Certain types of phosphors emit X-rays, α-rays, β-rays, γ-rays, electron beams,
When exposed to radiation such as ultraviolet rays, some of that energy is temporarily absorbed inside M! ? When the phosphor is excited by irradiating it with electromagnetic waves such as visible light or infrared rays or by heating it, it emits fluorescence (photostimulant light) according to the energy stored by the radiation irradiation. emanate. Such a phosphor is called a stimulable phosphor. This stimulable phosphor is formed into a sheet to form a radiation image conversion panel,
The panel absorbs the radiation transmitted through an appropriate object such as a human body to accumulate and store a radiation image of the object, and then the panel is scanned by spot irradiation with excitation light such as a laser beam and is stored in the panel. The image information is separated into pixels with a size approximately equal to the spot diameter of the excitation light, and the emitted light at each pixel position on the panel is read with an appropriate photodetector such as a photomultiplier tube, etc., and time-sequentially. Convert to electrical signal.

Based on the electrical signals, images can be reproduced on recording and display media such as photographic film and CRT. This type of radiation image reading method has the great advantage of being able to perform the desired image processing at the electrical signal stage compared to the method of directly forming and recording radiation images on photographic film. It is used extremely effectively.

However, in such conventional radiation image reading methods, when the radiation image conversion panel is irradiated with excitation light to emit light and converts the emitted light into an electrical signal, each pixel emitted from the panel surface to the outside is (Japanese Patent Application Laid-Open No. 56-64651, Japanese Patent Application Laid-open No. 61-15)
(See Publication No. 6250, Special Publication No. 61-29490)
In this case, light detection is performed by guiding the light to a photodetector using a suitable light focusing optical system. The above-mentioned Japanese Patent Application Publication No. 1983
In the method described in Japanese Patent Publication No. 64651 and Japanese Patent Publication No. 61-29490, a light focusing optical system consisting of a half mirror, a focusing lens, etc. is adopted.
The method described in Japanese Patent No. 6250 employs a light focusing optical system comprising a light guide sheet.

Such a light focusing optical system and a photodetector need to be placed in a predetermined position relative to the light emitting position, and highly accurate 7 alignments are required. In addition, it is difficult to set the light focusing optical system and the photodetector at a position where the emitted light is extracted upward relative to the scanning of the excitation light irradiation spot, and the necessity of focusing the light leads to an increase in the size of the device. There is a problem that the device configuration becomes complicated and the cost increases.

Furthermore, in the conventional radiation image reading method as described above, a part of the irradiated excitation light is reflected and guided to the photodetector together with the emitted light, so there is a drawback that it is difficult to detect the amount of emitted light with sufficient accuracy. Therefore, it has been proposed to use a filter to separate the excitation light and the emission light, but due to the filter's ability, sufficient separation is not possible, and this insufficient separation is perceived as noise, making it difficult to improve performance. I was exposed.

Therefore, the present invention solves the above-mentioned problems in the conventional technology, and provides a radiation image conversion panel capable of reading accurate and high-resolution radiation images with a simple configuration, and a radiation image conversion panel that reads radiation images stored in the panel. The purpose is to provide a method.

[Means for Solving the Problems] According to the present invention, the above object is achieved by a radiation image conversion method comprising a pair of electrodes, at least one of which is transparent, and a layer of stimulable phosphor. This is achieved by the panel.

Further, according to the present invention, the above objects are achieved.

A radiation image recorded on the stimulable phosphor layer of a radiation image conversion panel having a pair of electrodes, at least one of which is transparent, and a stimulable phosphor layer is transferred to the stimulable phosphor layer by converting the excitation energy of the stimulable phosphor into The body layer is intermittently irradiated in a spot shape, the irradiation energy spot is scanned on the phosphor layer, and at this time, a time-series pixel signal sequence is generated as electrical information between at least the pair of electrodes. A radiation image reading method characterized by reading by detecting.

This is achieved by

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic cross-sectional view showing a first embodiment of a radiation image conversion panel according to the present invention.

In FIG. 1, 2 is a layer made of a stimulable phosphor.

The Jffl type phosphor is preferably a phosphor that emits light in a wavelength range of 300 to 500 nm, and examples of such a stimulable phosphor include those shown below.

La0Br: Ce, Tb 5rS: Ce, Sm 5rS: Ce, B1 BaO. However, materials other than those that emit light in the wavelength range of 300 to 500 nm can also be used. JM like this
Examples of the phosphor include those shown below.

ZnS: Pb ZnS: Mn, Cu (0,3Zn, 0.7Cd)S:Ag ZnS, KCI:Mn Ca5:Ce, Bi The phosphor is formed into a sheet using a suitable binder by a conventional method. and the thickness is e.g. 50 gm to 500 uLm
It is said that

In FIG. 1, 4.6 is f of the phosphor layer 2, respectively.
A pair of electrode layers are attached to the surface and the top surface. The lower electrode layer 4 is made of a suitable metal such as AI.

The upper electrode layer 6 is a transparent electrode made of a transparent conductor such as ITO. The thickness of the electrode layer 6 is, for example, about several hundred to tens of thousands, and is particularly preferably 6000 Å or more.

FIG. 2 is an explanatory diagram showing an embodiment of the radiation image reading method according to the present invention.

In FIG. 2, lO is the radiation image conversion panel shown in FIG. 1 above, which panel consists of a stimulable phosphor layer 2 and a pair of electrode layers 4.6. The panel 10 has a rectangular shape with long sides in the X direction and short sides in the Y direction, and can be moved in the X direction by being driven by a driving means (not shown). Lead wires 12 and 14 are connected to the electrodes 4 and 6 of the panel 10, respectively, and the lead wires are connected to a bias power source 16. The voltage of the power supply varies depending on the thickness and dielectric constant of the stimulable phosphor layer 2, but is, for example, about 0.1 V to 5 V. Also.

A weak 'It flow detector 18 is located in the middle of the lead wire 14.
It is continued. A pixel signal extraction circuit 20 is connected to the detector, and a control circuit 22 is connected to the extraction circuit.
is connected. 24 is a memory using a magnetic recording medium or the like, and is attached to the control circuit 22.

In FIG. 2, 26 is a laser light source that emits laser light as excitation energy, and this light source emits the laser light in the y direction. Reference numeral 28 denotes a reflecting mirror, which is driven by a driving means (not shown) and can rotate around an axis in the X direction.

The laser beam emitted from the L light source 26 is reflected and deflected by the reflecting mirror 28, and the radiation image conversion panel 1
0, passes through the transparent electrode 6 of the panel, and forms a minute spot on the phosphor layer 2. The above reflecting mirror 28
When the rotation angle 0 changes from 01 to 02, the spot is scanned in the y direction from the position P1 of the phosphor layer 2 to the position faP2.

The laser light source 26 has an emission wavelength range of 500-1
Examples of such a laser light source, which preferably has a wavelength of 100 nm, include a Kr laser, a He-Ne laser, and a YAG laser. Of course, one emission wavelength range other than the above may also be used. Any excitation light source can be used as long as it causes stimulated luminescence in the phosphor of the radiation image conversion panel.

FIG. 3 is a diagram showing the operation timing and signals of each part in this embodiment.

In FIG. 3, (a) shows the X-direction position x of the panel 10, (b) shows the rotation angle θ of the reflecting mirror 28,
(c) shows the intensity of light emitted from the light source 26,
(d) shows the intensity of stimulated luminescence of the panel phosphor layer 2.

Incidentally, the panel IO has been irradiated with radiation in advance, and a radiation image of an appropriate pattern is stored in the phosphor layer 2.

At time O, the position x of the panel 10 is 0, and the rotation angle θ of the reflecting mirror 28 is O. The reflecting mirror 28 is then rotated at a constant angular velocity such that the rotation angle increases until time t3.

Time 1. to time t2, the light source 26
It flashes in a pulsed manner at regular intervals T. and,
At time t1, the rotation angle θ of the reflecting mirror 28 becomes 01, and at this time the laser beam spot exists at the level faPx of the panel phosphor layer 2. Then, at time t2, the rotation angle θ of the E-type reflecting mirror 28 becomes 02, and at this time the laser beam spot exists at the position P2 of the panel phosphor layer 2. Thus, from time t1 to time t2, a line-shaped portion of the panel phosphor layer 2 along the y direction from position MP1 to position iP2 is intermittently spot irradiated. Therefore, the time T corresponds to the pitch of the read pixels in the y direction.

As the irradiation spot of the panel phosphor layer 2 is scanned by the excitation laser beam as described above, each pixel portion is changed as shown in FIG. 3(d).
The luminescence intensity corresponds to the radiation field to which each pixel portion was previously irradiated.

As each pixel portion emit light in a time-series manner, an amount of charge corresponding to the amount of emitted light is transferred in the panel phosphor layer 2. The charges are moved in one direction by the bias voltage applied between the electrodes 4.6, thus causing a weak current to flow. The current is detected by a detector 18. Therefore, the current detector 18 obtains a time-series detection signal corresponding to the above-mentioned FIG.

The signal detected by the detector 18 is input to an extraction circuit 20. In the extraction circuit, for example, a peak value is extracted from the current signal corresponding to each pixel portion to form a pixel signal for the pixel portion. The extraction circuit is a control circuit 22
The control circuit records the pixel signals obtained in the above manner in the memory 24 together with each pixel address specifying signal obtained from the panel movement driving means and the reflecting mirror rotation driving means (not shown). FIG. 3(e) is a diagram showing pixel signals of a line-shaped portion from position 2tPx to position P2 recorded in this way. Corresponds to a stored image pattern.

At time t3, the panel 10 increases the distance l in steps.
It is forced to move by ax. The distance corresponds to the arrangement pitch of the reading pixels in the X direction. At the same time, at time t3, the reflection #n28 is reversed so that the angular velocity is the same as before, but the rotation angle is decreased.

FIG. 4 is a diagram showing the scanning path of the excitation laser beam irradiation spot on the panel IO. At time t4, the spot is located on the panel 10 at a distance of X in the X direction from the position P2.
It exists at the position 21P3, which is the position moved by the amount, and is then scanned and moved in the y direction to reach the position g\P4. During this time, the same operation as during the scanning movement from the above-mentioned position 2tPt to position P2 is performed.

Thereafter, spot scanning is performed in the same manner, thereby making it possible to read an image of a desired area.

FIG. 5 is a schematic sectional view showing a second embodiment of the radiation image conversion panel according to the present invention, in which the same members as in FIG. 1 are given the same reference numerals.

This embodiment differs from the first embodiment only in that a photoconductor layer 8 is interposed between the stimulable phosphor layer 2 and the electrode layer 4.

The photoconductor preferably has a relationship of A>B between its sensitivity to light with a wavelength of 300 to 500 nm (A) and the sensitivity to light with a wavelength of 600 to 800 nm (B). Examples include selenium-based materials. As the photoconductor, other materials such as selenium-tellurium, organic, amorphous silicon, etc. can also be used. When selecting a photoconductor, depending on the material of the stimulable phosphor and the excitation light source, the sensitivity to the excitation light should be as low as possible, and the sensitivity to the stimulated emission light of the phosphor layer 2 should be as low as possible. From this point of view, the one with the above-mentioned A>B condition uses a phosphor that emits light in the wavelength range of 300 to 500 nm, and the phosphor has a high Excitation wavelength range is 500-1100
This is extremely effective when using an am excitation light source.

In this embodiment, when the phosphor layer 2 undergoes stimulated emission during irradiation with excitation light, charges corresponding to the t-th stimulated emission light are also generated in the photoconductor layer 8 into which the emitted light is incident. Therefore, when reading an image with the configuration shown in FIG. 2, thus causing a more amplified current to flow than in the embodiment of FIG. The current is detected by the detector 18
Detected by

FIG. 6 is a schematic cross-sectional view showing a third embodiment of the radiation image conversion panel according to the present invention. In this figure, the same members as in FIG. 5 are given the same reference numerals.

This embodiment differs from the second embodiment only in that a transparent electrode layer 6a is further interposed between the stimulable phosphor layer 2 and the photoconductor layer 8.

In this embodiment, as in the case of the second embodiment,
When the phosphor layer 2 undergoes stimulated emission during irradiation with excitation light, charges corresponding to the stimulated emission light are also generated in the photoconductor layer 8 into which the emitted light is incident. Therefore, when reading an image with the configuration shown in the second vIJ, by partially changing the circuit configuration to the one shown in FIG. , 6a, the current thus flowing is detected by the detector 18a, and the charge generated in the photoconductor layer 8 is moved by the bias voltage applied between the electrodes 4.6a. The current flowing in this way is detected by the detector 18b, and the output information of the detectors 18a and 18b is added to the extraction circuit 2.
According to this embodiment, a larger amount of information can be obtained than when the panel shown in FIG. 5 is used.

In this embodiment, it is preferable to use a material having a low transmittance for excitation light and a high transmittance for stimulated luminescence light as the a-bright electrode layer 6a.

FIG. 8 is a schematic cross-sectional view showing a fourth embodiment of the radiation image conversion panel according to the present invention. In this figure, the same members as in FIG. 6 are given the same reference numerals.

In this embodiment, when the phosphor layer 2 undergoes stimulated emission during irradiation with excitation light, charges corresponding to the stimulated emission light are also generated in the photoconductor layer 8 into which the emitted light is incident. Therefore, when reading an image with the configuration shown in FIG. 4.6al
The bias voltage applied to l causes it to move, thus causing a more amplified current to flow than in the embodiment of FIG. The current is detected by a detector 18.

FIG. 9 is a schematic cross-sectional view showing the fifth embodiment of the radiation image conversion panel according to the present invention.
Similar members as in lrA are given the same reference numerals.

This embodiment differs from the first embodiment only in that a transparent protective layer 9 is provided on the transparent electrode layer 6. Transparency S
As the material for the layer, various organic polymers such as polyethylene terephthalate, polyester, cellulose acetate, ethyl cellulose, nitrocellulose, etc. may be used.

FIG. 10 is a schematic perspective view showing a sixth embodiment of the radiation image conversion panel according to the present invention. still.

In this figure, a part of the circuit for image reading is also shown. In this figure, the same members as in FIG. 1 are given the same reference numerals.

In this embodiment, the transparent electrode layer 6 is divided into two by a dividing line in the X direction to form divided portions 6c and 6d. Then, a bias voltage is applied to each divided portion by the power supply 16, and a current detector 18c is used to read pixel information in the area corresponding to the one divided portion 6c, and pixel information in the area corresponding to the divided portion 6d is used. A current detector 18d is used for reading. The extraction circuit shown in FIG. 2 and the following are connected to each detector. By dividing the electrode as described above, it is possible to reduce the influence of noise due to the movement of charges generated in areas other than the readout portion, and it is also possible to increase the number of scans as described below.

The excitation laser beam irradiation spot can be scanned by moving it back and forth in the X direction as shown by a in Figure 1θ, or by moving it back and forth in the X direction as shown by c in Figure 1θ. . Incidentally, by performing the reciprocating movements (a) and (c) at the same time, it is possible to read two areas at the same time, and in this case, the reading speed is doubled.

[Effects of the Invention] According to the present invention as described above, since the accumulated signal information that does not contain any noise with respect to the excitation energy of the stimulable phosphor can be detected using the electrode, it is possible to detect the accumulated signal information using the electrode. This method eliminates the need for rods, photomultiplier tubes, etc.), has extremely low detection errors, and enables accurate reading of pixel information.

Furthermore, according to the present invention, a signal that accurately corresponds to the spot diameter of excitation energy irradiation is obtained, so by improving the accuracy of the excitation energy irradiation system, image reading with sufficiently high resolution becomes usable.

Furthermore, according to the present invention, there is no need for a large-scale and precise light detection means and its movement mechanism.
It is easy to construct, and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1, FIG. 5, FIG. 6, FIG. 8, and FIG. 9 are all schematic cross-sectional views showing a radiation image conversion panel according to the present invention. FIG. 2 is an explanatory diagram showing the radiation image reading method according to the present invention, and FIG. 3 is a diagram showing the operation timing and signals of each part at that time. FIG. 4 is a diagram showing the scanning path of the excitation laser beam irradiation spot on the panel. FIG. 7 is a diagram showing a part of the circuit when reading an image. FIG. 1θ is a schematic perspective view showing a radiation image conversion panel according to the present invention. 2: stimulable phosphor layer, 4: electrode layer, 6, 6a: transparent electrode layer, 8: photoconductor layer, 9: transparent protective layer, IO: radiation image conversion panel, 26: excitation light source, 28 two reflecting mirrors . Figure 1 Figure 2 Figure 2 Day 3 Figure p, p2 Figure 8 Figure 9 Figure 10

Claims (13)

[Claims] (1) A radiation image conversion panel comprising a pair of electrodes, at least one of which is transparent, and a layer of stimulable phosphor. (2) The radiation image conversion panel according to claim 1, wherein the stimulable phosphor layer is present between the pair of electrodes. (3) The radiation image conversion panel according to claim 2, wherein only the stimulable phosphor layer is sandwiched between the pair of electrodes. (4) The radiation image conversion panel according to claim 2, wherein the stimulable phosphor layer and the photoconductor layer are arranged in this order from the transparent electrode side between the pair of electrodes. (5) Both of the pair of electrodes are transparent electrodes, and the stimulable phosphor layer is disposed between the electrodes, and the side of one of the pair of electrodes is opposite to the phosphor layer side. The radiation image conversion panel according to claim 2, wherein a photoconductive layer and an electrode are arranged in this order from the electrode side. (6) A photoconductive layer is disposed between the pair of electrodes, and the stimulable phosphor layer is disposed on a side of the transparent electrode opposite to the photoconductive layer. 1. Radiographic image conversion panel. (7) The radiation image conversion panel according to claim 2, wherein a transparent protective layer is attached to the surface of the transparent electrode. (8) having a photoconductor layer, the photoconductor layer having a wavelength of 300
Sensitivity (A) to ~500nm light and wavelength 600~8
The radiation image conversion panel according to claim 1, wherein the relationship A>B holds between sensitivity (B) to 00 nm light. (9) The radiation image conversion panel according to claim 1, which has a photoconductor layer, and the photoconductor is made of a selenium-based compound. (10) The radiation image conversion panel according to claim 1, wherein at least one of the pair of electrodes is electrically insulated in a plurality of directions in the in-plane direction. (11) A radiation image recorded on the stimulable phosphor layer of a radiation image conversion panel having a pair of electrodes, at least one of which is transparent, and a stimulable phosphor layer is is intermittently irradiated onto the phosphor layer in the form of spots, and the irradiation energy spot is scanned over the phosphor layer, and at this time, time-series pixels are generated as electrical information between at least the pair of electrodes. A radiation image reading method characterized by reading by detecting a signal train. (12) The radiation image reading method according to claim 11, wherein a DC bias voltage is applied between the pair of electrodes. (13) The radiation image reading method according to claim 11, wherein the excitation energy is an electromagnetic wave in a wavelength range of 500 to 1100 nm.