JPS61262358A - Reproducing method for radiograph - Google Patents

Abstract

PURPOSE:To attain reading with proper accuracy even when a level of a picture signal fluctuated due to fluctuation of a radiant ray dose by a radiant ray source by providing a memory storing picture information for one pattern in a recording medium and recording a picture while a larger storage capacity than that of the dynamic range required for the reproduction of a picture to the said memory. CONSTITUTION:Laser light from a stimulated light generator 2 is scanned on the surface of a recording medium 1 coated with an accumulated phosphor. The fluorescence emitted through the stimulation is converted linearly into an electric signal by a photodetector 3, a voltage (signal intensity) via an amplifier section is subjected to A/D conversion at an equal interval, the result is led to a memory 4, where the read picture signal is stored with the recording width over the dynamic range required for the reproduction and the signal only with a required level is extracted and a reproduced picture is obtained on a CRT.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a radiation image reproducing method in which a radiation image is recorded on a stimulable fluorescent material and irradiated with stimulated excitation light to reproduce the radiation image. Regarding.

[Prior art]

By irradiating a subject with radiation, causing the radiation transmitted from the subject to be absorbed by a storage phosphor, and then exciting the phosphor with, for example, light or thermal energy, the radiation accumulated in the phosphor can be removed. A device that extracts energy and detects it with a photodetector to generate an image signal is disclosed in US Pat. No. 3,859.

It is known as described in Japanese Patent Application Laid-open No. 527, Japanese Patent Application Laid-Open No. 55-12144, and Japanese Patent Application Laid-Open No. 55-12429. Such image signals are processed and the image of the subject is reproduced as a hard copy. Many papers have been published recently on these methods because they require only a small amount of radiation to produce hard copies. However, in order to convert the optical signal based on the intensity of light due to the energy stored in the stimulable phosphor into an electrical signal, and output the electrical signal as a visible image to a hard copy of a photographic light-sensitive material or a display device such as a CRT, the It has the disadvantage that accurate image reproduction is difficult to obtain due to fluctuations in the irradiation amount due to fluctuations in the radiation light source in the process and fluctuations in the reading gain for detecting fluorescence due to the excitation light of the stimulable fluorescent recording medium. As a means to solve this problem, JP-A-58-67
A method described in Japanese Patent No. 242 has been proposed. This is a method in which the stimulable phosphor is irradiated with excitation light twice, and the conditions for subsequent main reading, image processing conditions, etc. are set based on the first readout information, and the adverse effects caused by the fluctuations are corrected. However, attenuation of the stored energy due to the first reading is unavoidable, and the image quality obtained during the second reading will deteriorate. , there is also the disadvantage that the throughput of the device is reduced due to reading twice.

[Problem that the invention seeks to solve]

The present invention aims to improve the above-mentioned drawbacks, and allows reading to be performed with appropriate accuracy even if there are fluctuations in the image signal level due to fluctuations in the amount of radiation irradiated by the radiation light source, etc., and under appropriate reproduction conditions. It is an object of the present invention to provide a radiographic image reproduction method that can perform reproduction according to the method of the present invention, and a further object of the present invention is to provide a radiation image reproduction method that can perform reproduction without slowing down the reading speed.

[Means for solving problems]

The object of the present invention is to irradiate a recording body having a stimulable phosphor with radiation imagewise exposure, scan the recording body with excitation light, and detect light emission from the recording body. It has a memory that stores image information for one screen, and by taking out a portion of the dynamo necessary for image reproduction into the memory and performing radiation image-like exposure to reproduce the image, it is possible to reproduce a more accurate radiation image. can.

The stimulable phosphor of the recording medium used in the present invention is irradiated with the first light or high-energy radiation and then stimulated by thermal, mechanical, chemical, or electrical energy to produce the first light or high-energy radiation. A phosphor that exhibits so-called photostimulability, which re-emits light corresponding to the amount of energy radiation irradiated. Here, light includes visible light, ultraviolet light, and infrared light among electromagnetic radiation, and high-energy radiation includes X-rays, gamma rays, beta rays, alpha rays, neutron rays, and the like. This phosphor can be one that emits light with a wavelength of 300 to 500 mm when excited by the excitation light. For example, JP-A-48-8
Ba80. described in No. 0487. : A phosphor represented by Ax (where A is at least one of Dy, 'rb and Tm, and X is 0.001≦x<1 mol%), as described in JP-A No. 48-40488. Mg
5O,: A phosphor represented by Ax (where A is either HO or Dy, and 0.001≦x<1 mol%), as described in JP-A-48-80489. 5rSO, : Ax (However, A is DY
, Tb and Tm, and X satisfies 0.001≦x<1 mol%. ), B described in JP-A No. 52-30487
eO.

Phosphors such as LiF, MgSO4 and CaF, Sr8 as described in U.S. Pat. No. 3,859,527:
Ce.

am, SrS: gu, am, La1O, S: I
Examples include phosphors represented by u, 8m and (Zn, Cd) 8: Mn, X (where X is a Q-gen). In addition, the general formula is M"O-xsiO,: A (where Ml is Mg, Ca, Sr, ZnCd or Ba,
A is Ce, Tb, Eu, Tm.

At least one of Pb, Tl, Bi, and Mn, and X satisfies 0.5≦X≦2.5. ) are alkaline earth metal silicate-based phosphors.

Also, the general formula is (Ba, -x -yMgxcay)'gx, e
Eu (where X is at least one of Br and CI!, and x, y and e are each O< x + y≦
0.6, xy〆0 and turtle ff-'≦e≦s x to
This is a number that satisfies the condition -2. ) Alkaline earth fluorohalide phosphor represented by JP-A-55-1214
The general formula described in No. 4 is LnOX: xA (Ln is at least one of La, Y, Gd and Lu, X is C/ and/or Br, and A is C
e and/or Tb, and X represents a number satisfying O<X<0.1. ), a phosphor expressed by JP-A-1988
The general formula described in No. 5-12145 is (Ba1-
xM'x) FX: yA (However, MI is Mg
, Ca, Sr, Zn, and Cd, X is at least one of CIe, Br, and l, A is E! u, Tb, Ce, T
m.

At least one of Dy, Pr, He, Nd, Yb and Ir, where X and y are 0≦X≦
It represents a number that satisfies the conditions 0, 6 and 0≦y≦0.2. ), the general formula described in JP-A-55-84389 is BaFX:xCe,
yA (However, X is at least one of Cj', Br and I, A is In, TI!, Gd, S
is at least one of m and Zr, and X and y are O< x≦2×to” and o<y≦5, respectively
A phosphor represented by
The general formula described in No. 5-160078 is ■ M FX -xA : yLn (However, 1.II is at least one of Mg, Ca, Ba, Zn and Cd, A is BeO, MgO,
CaO, SrO.

BaO, ZnO, A120B, Y2O3, La, O,
, In, 0. .

8i02. Ti01, ZrO2, Gem,,
Snug, Nb10g.

At least one of Ta, O, and The,
Ln is Eu, Tb, Ce, Tm, Dy
, Pr, Ho, Nd, YbEr,
is at least one of Sm and Gd, and X
and y are numbers satisfying the conditions of 5 X 10-5≦X≦0.5 and Q<y≦0.2, respectively. ) rare earth element-activated divalent metal fluoro tetrahalide phosphor, general formula [1) or (II) described in JP-A-57-148285, xM, (PO,), ・NX: yA
General formula (J Ma (Pot)t: yA (wherein, M and N are Mg, Ca, and Sr, respectively)
.

At least one of Ha, Zn and Cd, X is F, CIe, Br and! At least one of A is Eiu, Tb, CIe, Tm, Dy, Pr,
Ho, Nd.

Yb, FXat, Sb, Tl, Mn
and Sn. Also, X
and y is a number that satisfies the condition 0<x≦6.0≦y≦1. ) and the general formula (13
or [W), general formula 113 nReX3- mA
Xi: xEu general formula (Iv)nReX3-mA
Xl: xEu-78m (wherein, Re is La, Gd,
At least one of Y and Lu, A represents an alkaline earth metal, at least one of Ba, Sr, and Ca, and X and X' represent at least one of F* C1I Br. Also, X and y are 1 x to-4
< x < 3 x 10-1, I x 10-'<
It is a number that satisfies the condition y <I
m is 1x to-3 < n/m < 7 x 10
The phosphor used in the present invention is not limited thereto.

In addition, the excitation light used to make these stimulable phosphors emit light again is one that radiates the radiation energy accumulated in the stimulable phosphors and converts it into light, and visible light sources or infrared rays can be used. but especially 600-700 n
It is effective to use light in the wavelength range of )ie −N
Preferable lasers include e-laser, Ar laser, YAG laser, He-Cd laser, Kr laser, and E-47 semiconductor laser. Further, it can be used by converting it into light in the wavelength range of 600 to 700 nH using a filter.

As a support for the recording medium used in the present invention.

Any material may be used as long as it has the supporting performance of a generally known recording layer, such as paper, metal plate, synthetic resin plate, etc., such as a polyethylene sheet with a thickness of 50 to 300 pm, a plastic film, an aluminum plate, a thickness of 1 to 3 iw+ glass plates, etc. are commonly used.

〔Example〕

The present invention will now be described in detail based on examples.

FIG. 1 is a schematic diagram of an apparatus using the radiation image reproduction method of the present invention, in which 1 is a recording medium coated with a stimulable phosphor;
Laser light from the excitation light generator 2 is scanned over this surface. The fluorescent light that is excited and emitted by this is detected by a photodetector 3.
Converts the amount of light into an electrical signal near IJ,
In step 9, the voltage (signal strength) is converted to A/D at equal intervals via the amplification section, and led to memory 4, where the image signal read out is recorded with a dynamic range that exceeds the dynamic range required for reproduction. The signal width is stored, and only signals of the necessary level are extracted to obtain a reproduced image on a CRT.

Figure 2 shows the light source after radiation.
In FIG. 2, (a) shows an example of a histogram of an image signal corresponding to each signal intensity level. Sm1n and Smax indicate the intensity range (recording width) of the signal set and recorded during reading. On the other hand, S'min S'max is the minimum value and maximum value of image data actually obtained, and it changes depending on fluctuations in photographing conditions, fluctuations in gain of the reading system, etc.
Sm1n and Smax are set so that their fluctuations can be sufficiently covered.

.DELTA.S is the width of one step after A/D conversion, and must be set sufficiently small so that good gradation can be obtained under desired reproduction conditions. (b) is a diagram showing an example of reproduction conditions, where ■ is a reproduction condition with soft tone, ■ is a condition where high tone is used to make the low density area of 1 easier to see, and ■ is a condition where high tone is used to make the high density area of summer easier to see. It is a condition to express.

In normal X-ray photography of the human body, the effective width of the image signal is approximately 100 as S'max/S'min, and in addition to this, considering fluctuations in imaging conditions, reading conditions, etc., Smax and Sm1n can be calculated. Set the value. In addition, Sm
Unnecessarily widening the width of ax NSm1n is accompanied by a decrease in the accuracy of light emission detection, so it is appropriate to keep it within the necessary limit. It is also necessary to change it depending on the part to be imaged.

FIG. 3 is a histogram of an image signal when a log lamp is used as a light source.

log,. s=p shall be.

0.3≦a+b≦0.6 The dynamic range setting conditions are a + b -0,3 Then becomes.

Example 8 parts by weight of a phosphor consisting of BaFBr and Eu were dispersed in 1 part by weight of polyvinyl-j-tyral using a solvent mixed with equal amounts of acetone and ethyl acetate, and this was spread onto a polyethylene terephthalate substrate using a wire par. It was created by applying it. The dry thickness of the phosphor layer of this recording medium was approximately 300 μm.

After irradiating this recording body with X@ with a polarizing voltage of 80 KVP, a He-Ne laser beam was applied to this recording body as excitation light for 4 μs.
The fluorophore was excited by irradiation for EC, and luminescence was detected using an excitation light cut filter in front of the photomultiplier tube. This image information is amplified and A/D converted to approximately LObits.
to memory. This was then introduced into a CRT device with 8 bits to obtain a reproduced image. At this time, X-ray transmission images are continuously projected onto a recording medium, and when reproduced images are obtained from this recording plate on a CRT, good images that are not affected by changes in the X@irradiation amount are continuously obtained. Ta.

〔Effect of the invention〕

According to the radiographic image reproduction method of the present invention, reading can be performed with the necessary accuracy even if there is a variation in the amount of X-ray irradiation, and a reproduced image with good image quality can always be obtained under appropriate reproduction conditions without reducing reading throughput.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus implementing the radiation image reproduction method of the present invention, and FIGS. 2 and 3 are histograms of image signals. 1...Recording body 2...Excitation light generator 3...Photodetector Applicant Roku Konishi Photo Industry Co., Ltd. Figure 2 (IIX) (α) Procedural amendment 1. Display of incident 1985 Patent II No. 86875 2, Title of invention Radiographic image reproduction method 3.11I! Relationship with the person who corrects the case Patent applicant address Konishiroku Photo Industry Co., Ltd., 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 1-1 Sakuracho, Hino-shi, Tokyo 191 (Telephone: 0425-83-152)
1) Patent Section 5, "Detailed Description of the Invention" column 6 of the subject specification of M, as per the attached sheet

Claims (1)

[Claims] 1. A recording medium having a stimulable phosphor is irradiated with radiation imagewise exposure, the recording medium is irradiated and scanned with excitation light, and the light emitted from the recording medium is detected to generate an image signal. A radiographic image reproducing device that reproduces an image using this image signal has a memory that stores image information for at least one screen in a recording medium, and the memory has a recording area wider than the dynamic range required for image reproduction. A radiation image reproduction method that records an image by giving a width and reproduces the image by extracting a part of the recording width of the recorded image information. 2. The radiation image reproducing method according to claim 1, wherein the image reproducing condition is determined from at least one of the maximum value, minimum value, or average value of the detected value of light emission from the recording medium.