JPH02275428A - Recording and reproducing method for radiograph information - Google Patents

Abstract

PURPOSE:To classify and display the differences of radiation energy absorption characteristics of respective structures in an object by storing ionizing radiation which is transmitted through the same object on plural stimulable phosphor sheets in mutually different energy distribution states. CONSTITUTION:A 1st stimulable phosphor sheet A is arranged at the position closest to a radiation source 3, 2nd and 3rd stimulable phosphor sheets B and C are arranged on the opposite side from the radiation source 3 in order, and the radiation source 3 is driven. The radiograph of the object 1 is accumulated and stored on the stimulable phosphor sheets A - C with the ionizing radiation 2. Stimulating light 13 emitted from the respective stimulable phosphor sheets which are irradiated with stimulating light is detected photoelectrically to obtain (n) image signals S carrying image information, and those (n) image signals are used as specific monochrome signals to reproduce a color radiation image of the subject according to the signals. Consequently, the differences of the radiation energy absorption characteristics of respective structures in the object are classified and displayed with the reproduced image.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a radiation image information recording and reproducing method using a stimulable phosphor sheet. This relates to a method for recording and reproducing radiation image information that can be displayed in different colors.

(Prior art) When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, ultraviolet rays, electron beams, etc.), part of the energy of this radiation is absorbed into the phosphor. When the phosphor is then irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy. (exhaustive phosphor).

Using this stimulable phosphor, radiation image information of a subject such as a human body is recorded on a stimulable phosphor sheet (hereinafter referred to as a stimulable phosphor sheet), which is then scanned with excitation light and illuminated. A method has been proposed in which the stimulated emitted light is photoelectrically read to obtain an image signal, and the image signal is processed to obtain a radiographic image of a subject that is suitable for diagnosis (for example, Japanese Patent Application Laid-Open No. 1983-1981). No. 12429, No. 55-116340, No. 55-163472, No. 56-11395, No. 56-104645, etc.).

By the way, a subject such as a human body that is used for recording and reproducing radiation image information as described above includes several structures such as bones and soft tissues that have different radiation energy absorption characteristics. is common. If such differences in radiation energy absorption characteristics could be differentiated and shown in some way in reconstructed radiation images, it would be very convenient for medical diagnosis and the like. Energy subtraction processing of radiographic images has been known as a technology to meet such demands (for example, Japanese Patent Laid-Open No. 5
9-83486). This energy subtraction process irradiates the same subject with radiation having different energy distributions, or changes the state of energy distribution of the radiation that has passed through the subject and irradiates it to two radiation detection means. Images with different structures are placed between two radiographic images, and then subtracting is performed with appropriate weighting between the image signals of these two radiographic images to obtain a certain radiation energy absorption characteristic. This is to obtain an image signal (difference signal) that extracts only a part of the structure.

(Problems to be Solved by the Invention) This energy subtraction processing has greatly contributed to the advancement of medical diagnostic technology, but since it extracts only a specific structure in a reproduced image, It is impossible to differentiate and display each of a plurality of structures in accordance with the difference in radiation energy absorption characteristics in a set of reproduced images.

The above-mentioned differentiation would be very convenient if the colors could be displayed. Displaying recorded information in color based on image signals read from a stimulable phosphor sheet is described, for example, in Japanese Patent Application Laid-Open No. 63-258158, but the technology disclosed in this publication was originally Even if this technology is used, because it exposes a color image to a stimulable phosphor sheet and does not record a transmitted radiation image,
It is impossible to display the aforementioned difference in radiation energy absorption characteristics in terms of color in a reproduced image.

The present invention has been made in view of the above circumstances, and provides a radiation image information recording and reproducing method that can display the differences in the radiation energy absorption characteristics of each structure in an object by color in a reproduced image. The purpose is to provide

(Means and effects for solving the problem) The radiation image information recording and reproducing method of the present invention uses n stimulable phosphor sheets (2≦n) as described above, and uses these stimulable phosphor sheets. Then, the radiation transmitted through the same object is accumulated in different energy distribution states, and the radiation image information of the object is recorded respectively. Next, each stimulable phosphor sheet is irradiated with excitation light, so that each accumulation The stimulated luminescent light emitted from the phosphor sheet is photoelectrically detected to obtain n sets of image signals carrying the above image information, and each of these n sets of image signals is converted into a predetermined monochromatic signal. This system is characterized by reproducing a color radiation image of a subject based on the following.

In order to accumulate radiation in different energy distribution states in each stimulable phosphor sheet as described above, (1) use n stimulable phosphor sheets having different types of phosphor layers; (2) A method of recording images by placing a sheet having a stimulable phosphor layer with higher absorption characteristics for low energy components of radiation closer to the subject (radiation source side) among the stimulable phosphor sheets of A method of obtaining radiation with different energy distributions by interposing a filter made of metal or the like that absorbs a specific energy component of radiation between each of the stimulable phosphor sheets;
Furthermore, (3) the n stimulable phosphor sheets are subjected to radiation image information recording (photography) one by one, and at that time, the energy of the radiation irradiated to each sheet is changed by changing the tube voltage of the radiation source, etc. Any method of changing the distribution state can be used. Alternatively, a combination of methods (1) and (2) may be used.

In addition, when using method (1), phosphors containing Sr%Ba and Gd, especially SrFX
: Z, BaFX' : Z', Gd0X' :
Preferably, Ce is used. Here, x and x' are both at least one halogen of Cl5Br and I, X'' is at least one halogen of CI and Br, and %Z%Z' are both Eu and Ce. At least one kind of rare earth element.2
When using 2 sheets, please use 2 sheets in this order depending on the purpose.
All you have to do is select one sheet.

For example, three stimulable phosphor sheets are used, and among the three sets of image signals obtained by reading processing for each sheet,
A read image signal from a stimulable phosphor sheet that mainly accumulates medium radiation energy components is defined as a G (green) signal,
The other two sets of image signals are R (red) signal and B signal respectively.
(Blue) Signal. In other words, in the reproduced radiation image, the longer the reproduced color of a certain structure is, for example, the longer the wavelength, the lower (or higher) the radiation level of that structure is.
It can be determined that the absorption rate of energy components is low.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a state in which radiation 2 that has passed through the same object 1 is irradiated onto three stimulable phosphor sheets ASB and C.

That is, the first stimulable phosphor sheet A is arranged at the position closest to the radiation source 3, and then the second and third stimulable phosphor sheets B and C are arranged in sequence on the side opposite to the radiation source 3. The radiation source 3 is driven. As a result, a radiation image of the subject 1 is accumulated and recorded on these stimulable phosphor sheets A, B, and C by the radiation 2. At this time, it is assumed that the positional relationship of the subject 1 in the stimulable phosphor sheets A, B, and C is the same.

Furthermore, the three stimulable phosphor sheets ASB and C have different radiation energy absorption characteristics. In this example, as the first stimulable phosphor sheet A, 5rFB which best accumulates the low energy components of the radiation 2 is used.
As the second stimulable phosphor sheet B, BaFBro, s I, which best stores the medium energy component of the radiation 2, is used.
o,2: A sheet having a layer of Eu phosphor is used, and as the third stimulable phosphor sheet C, Gd0C1:C which best stores the high energy components of radiation 2 is used.
A device having a layer of e-phosphor is used.

Next, these three stimulable phosphor sheets A and B.

A radiation image is read from C by an image reading means as shown in FIG. 2, and a digital image signal representing the image is obtained. First, while moving the stimulable phosphor sheet A in the direction of the arrow Y using a sub-scanning means 9 such as an endless belt, the laser beam (excitation light) 11 from the laser light source IO is deflected by the scanning mirror 12, and the sheet A is scanned. Perform main scanning in the X direction. In this embodiment, the laser light source 10 is a combination of a YAG laser that emits a laser beam with a wavelength of 11064n and an optical wavelength conversion element that converts the laser beam into a second harmonic.

By scanning this wavelength-converted laser beam 11 with a wavelength of 532 nm as described above, the stimulable luminescent light 13 is emitted from the stimulable phosphor A with an amount of light corresponding to the radiographic image information stored and recorded. emanates. Photostimulated luminescence light 13
is a light guide 14 made by molding a transparent acrylic plate.
The light enters the inside of the light guide 14 from one end surface of the light guide 14, travels therein while undergoing repeated total reflection, and is received by a photomultiplier (photomultiplier tube) 15. The photomultiplier 15 outputs an image signal S corresponding to the amount of the stimulated luminescence light 13, that is, indicative of the above-mentioned image information.

This output image signal S is logarithmically amplified by a logarithmic amplifier 16, then passed through an A/D converter 17, and converted into a digital image signal 1ogs1.

This digital image signal 10g5l is stored in a storage medium 18 such as a magnetic disk. Next, in exactly the same manner, the recorded image information of the other two stimulable phosphor sheets BSC is read out, and the digital image signal 1 representing the image information is read out.
ogS2 and fogs3 are similarly stored on storage medium 18.

Next, the digital image signal 10 obtained as described above is
Regarding the process of reproducing the radiation image of subject 1 based on IogS z s fogs s,
This will be explained with reference to the figures. First, using the reading device 19, image files 18A, 18B, and 1 in the storage medium 18 are read.
From 8C, the digital image signal 1ogs1, fogs
2 and l0g53 are read out, and their signals are sent to the signal processing circuit 20. At this time, the image signal is 1ogS
1 s IogS 2 Sl0g53 are each R(
The signals are input to the signal processing circuit 20 as a red) signal, a G (green) signal, and a B (blue) signal. These signals 1ogs1
~log S3 undergoes processing such as gradation processing and addition of a synchronization signal in the signal processing circuit 20, and then is sent to the image reproducing device 21, where it is used for reproducing a radiation image. This image reproducing device 21 may be a display means such as a color CRT, or a recording device that performs optical scanning recording on a color photosensitive film.

Image signals 10g5l, +ogsz and f as above
When a color image is reproduced using ogs3 as an image signal for each color, in the reproduced image, among the structures of subject 1, those through which the low energy component of radiation 2 is well transmitted are red;
Similarly, structures through which the medium energy component of the radiation 2 is well transmitted are displayed in green, and structures through which the high energy component of the radiation 2 is well transmitted are displayed in blue. For example, a structure that transmits both the low energy component and the medium energy component well is yellow or orange, and a structure that has other intermediate radiation energy absorption characteristics is red. , displayed in an intermediate hue between green and blue.

In this example, image signals 10g5l, +ogsz, +ogsz, obtained from stimulable phosphor sheets A, B, and C, respectively.
Although fogs3 is used as an R signal, a G signal, and a B signal as is, it is preferable to perform appropriate processing on these signals to remove the influence of energy components other than the energy components to be carried.

That is, as shown in FIG. 4, the image signals 1ogs1 and +
ogsz is input to the subtraction circuit 30, and these image signals logs1 and IogSz are subtracted for each corresponding pixel to obtain log S2 −log Sz −alog Sl(α
is an appropriate coefficient). Obtain a difference signal 10g5g', and convert this signal 1ogSz to G
It can also be used as a signal. Similarly, image signal logS2 and f
ogs3 is input to the subtraction circuit 31, and these image signals +ogs2 and fogs3 are subtracted for each corresponding pixel to obtain a difference signal 1ogS3' of log s3 -1ogs, -β+ogs2 (β is an appropriate coefficient). , this signal 10g53 may be used as the B signal. Regarding this B signal, in order to further remove the influence of the low energy component of radiation 2, log S3 - log S3 - βlog
It may also be Sz-alog Sl.

The stimulable phosphor sheet used in the present invention and the wavelength of the excitation light related thereto are not limited to those in the above-mentioned embodiments, and various combinations are possible. For example, stimulable phosphor sheets A arranged in order from the radiation source 3 side
, B, and C as 5rFI:Eu, BaFBr, respectively.
:Eu5GdOC1:Ce with a layer of phosphor, and those stimulable phosphor sheets) A, B, C at wavelength 63
Radiation image information can also be read by scanning with a 3 nm He-Ne laser beam.

In addition, in the case of two-color display, for example, as a stimulable phosphor sheet ASC that satisfactorily accumulates the low-energy component and high-energy component of the radiation 2, S rFB r :
Eu, , Gd0C1: Using a layer of Ce phosphor, these stimulable phosphor sheets) A and C have a wavelength of 51
Radiation image information can also be read by scanning with a 4.5 nm Ar laser beam.

Furthermore, in the case of two-color display, for example, BaFB is used as a stimulable phosphor sheet BSC that satisfactorily accumulates medium energy components and high energy components of radiation 2.
ro, a Io, 2: Eu, Gd0 CI: Ce having a phosphor layer was used, and the stimulable phosphor sheets B and C were scanned with a He-Ne laser beam with a wavelength of 633 nm to read radiation image information. You can also do it.

In the case of this two-color display, for example, the read image signal from one stimulable phosphor sheet may be used as the R signal, and the read image signal from the other stimulable phosphor sheet may be used as the G signal. However, the color correspondence is not limited to this example; the image signal from one stimulable phosphor sheet can be used as the G signal, and the image signal from the other stimulable phosphor sheet can be used as the B signal. You can choose. However, when using the B signal, it is preferable to use it for images with energy-saving components that include many noise components. In addition, three stimulable phosphor sheets ASBS
Even when C is used, contrary to the above embodiment,
The read image signal 1ogs1 from the stimulable phosphor sheet A is the B signal, and the read image signal to from the stimulable phosphor sheet C is
It is also possible to use gs3 as the R signal. However, in this case as well, the noise components of the image generally tend to increase in the order of AlB and C, so l0g53 (or log33'
) is preferably a B signal whose noise is difficult to visually identify.

Further, instead of scanning the plurality of stimulable phosphor sheets with a common excitation light, they may be scanned with excitation light of different wavelengths in accordance with the excitation characteristics of the phosphor of each sheet. In order to do so, each stimulable phosphor sheet may be read by a separate reading device, or one reading device may be configured so that the excitation light source can be switched.

The above describes an example in which stimulable phosphor sheets having different energy component absorption characteristics are used in order to accumulate radiation in different energy distribution states in a plurality of stimulable phosphor sheets. By disposing such a filter between each stimulable phosphor sheet, radiation may be accumulated in each of the stimulable phosphor sheets in a different energy distribution state, or these two methods may be combined. Furthermore, in the present invention, a plurality of stimulable phosphor sheets are subjected to radiation image information recording (photography) one by one, and at that time, the energy distribution of the radiation irradiated to each sheet is adjusted by changing the tube voltage of the radiation source, etc. It doesn't matter if you change the state.

(Effects of the Invention) As explained in detail above, the radiation image information recording and reproducing method of the present invention accumulates radiation transmitted through the same subject in different energy distribution states in a plurality of stimulable phosphor sheets, and Since each image signal obtained by reading the stimulable phosphor sheet is used as a monochromatic signal to reproduce a color image, the reproduced image obtained by this method is able to detect differences in the radiation energy absorption characteristics of each structure of the subject. will be shown in different colors. Therefore, according to the method of the present invention, structures such as bones, soft tissues, and blood vessels can be clearly differentiated and shown in reconstructed radiographic images by different hues, which further improves diagnostic technology. Effects can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the radiation image storage and recording step in the method of the present invention, and FIG. 2 is a schematic diagram illustrating the reading of radiation image information from the stimulable phosphor sheet on which the storage and recording has been performed. FIG. 3 is a block diagram showing an example of an apparatus for reproducing images according to the method of the present invention, and FIG. 4 is a block diagram showing another example of an apparatus for reproducing images according to the method of the present invention. 1... Subject 2... Radiation 3... Radiation source 10... Laser light source 11... Laser light 12... Scanning mirror 13... Stimulated luminescence light 14... Light guide 15. ...Photomultiplier 1G...Logarithmic amplifier 17...A/D converter 19...Reading device 20...Signal processing circuit 21...Image reproduction device 30.31...Subtraction circuit A , B, C... stimulable phosphor sheet

Claims (1)

[Scope of Claims] Radiation that has passed through the same object is accumulated in n (2≦n) stimulable phosphor sheets in mutually different energy distribution states, and radiographic image information of the object is recorded respectively, Next, each stimulable phosphor sheet is irradiated with excitation light, and thereby the stimulated luminescence light emitted from each stimulable phosphor sheet is photoelectrically detected to obtain n sets of image signals carrying the image information. A radiation image information recording and reproducing method characterized in that each of the n sets of image signals is used as a predetermined monochromatic signal, and a color radiation image of the subject is reproduced based on the signal.