JPH0697266B2 - Radiation image detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radiation image detecting apparatus capable of accurately measuring the two-dimensional spread and density of a radioactive substance contained in a biological sample.

(Prior Art) Many proposals have been made and implemented as a method for quantifying the presence of radioactive substances in a sample.

Quantify the radioactive substances in the sample slices created by cutting biological tissues, etc., apply liquid scintillator to the sample surface to measure its distribution, place a photosensitive film on it, and use the radiation from the sample. There is a method of recording the scintillation light on the photosensitive film by the generated scintillation light.

There is also a method of recording radiation by directly contacting a film with a film sensitive to the energy of radiation from the sample.

There is also a method (gas chamber method) of flowing a gas over a sample and recording the ionized state of the gas ionized by radiation energy.

Since any of the above-mentioned methods has low detection sensitivity, it takes a long time for measurement.

In particular, when a photosensitive emulsion sensitive to scintillation light or radiation is used, there is a problem that "monitoring cannot be performed during exposure".

For example, when it is necessary to expose a film for several weeks to several months in order to obtain pharmaceutical knowledge by autoradiography, there is a disadvantage that the exposure state cannot be known during the exposure. Then, it is necessary to carefully measure the development process and the transmittance of the developed film with a microphotometer in order to accurately determine the radiation dose from the degree of blackening of the exposed film.

In order to solve these problems, there has been proposed a radiation image detecting device (Japanese Patent Laid-Open No. 61-296290) capable of quantifying radioactive substances in a sample by a method which is completely different from the method described above.

The radiation image detecting apparatus according to the above-mentioned proposal is a scintillator arranged on the surface of a sample containing a radioactive substance, and photoelectrically converts the scintillation light to multiply it by a microchannel plate and make the scintillator enter the scintillator on a fluorescent surface. An image intensifying device for forming an image corresponding to a radiation quantum unit, an optical means for connecting the light emission of the scintillator to a photocathode of the image intensifying device, and a television imaging device for taking an image of a fluorescent surface of the image intensifying device. From the image processing device that processes the video signal indicating the generation position of the fluorescent image obtained for each imaging and stores it in the frame memory, and stores the generation frequency of each position, and the output device that outputs the processing result. It is configured.

(Problems to be Solved by the Invention) In the radiation image detecting apparatus described above, scintillation corresponding to a radiation image can be obtained by disposing a scintillator on the surface of a sample containing a radioactive substance. Since an optical means is used for connecting to the photocathode (photocathode) of the image intensifier, light other than scintillation may be mixed.

In particular, due to the weak integration of scintillation light, mixing of light from the outside becomes a problem when an emission image is to be obtained.

Also, the device for preventing this mixture becomes large,
Handling is also complicated.

An object of the present invention is to provide a radiation image detecting device capable of accurately measuring the two-dimensional spread and density of a radioactive substance contained in a biological sample or the like with a high resolution without being affected by external noise. To provide.

(Means for Solving the Problem) In order to achieve the above-mentioned object, the radiation image detecting device according to the present invention has a large number of scintillation materials for each recess formed by engraving a core glass portion on one surface to a substantially constant depth. A scintillation fiber plate filled with particles and fixed, and a photocathode is connected to the scintillation fiber plate via a fiber plate, and the scintillation fiber is photoelectrically converted to multiply the scintillation light by a microchannel plate and the scintillation fiber on the fluorescent surface. An image intensifier that forms an image corresponding to one radiation quantum unit incident on a plate, a television imager that captures an image of the fluorescent surface of the image intensifier, and the generation of a fluorescent image obtained for each image The video signal indicating the position is processed and stored in the frame memory, and the frequency of occurrence for each position is stored. It is composed of an image processing device and an output device for outputting a processing result.

The radiation source to be measured can be arranged close to the surface of the scintillation fiber plate on which the scintillation material particles are provided.

Suitable scintillation material particles for the scintillation fiber plate are particles of zinc sulfide or particles of cadmium sulfide with added silver.

A metal thin film that transmits radiation and reflects scintillation light may be provided on a surface of the scintillation fiber plate that is filled with scintillation material particles.

(Example) Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a radiation image detecting device according to the present invention.

FIG. 2 is a view showing the scintillation fiber plate, the image intensifying device, and the image pickup device taken out of the device, and the image intensifying device is shown broken along a plane including the tube axis.

FIG. 3 is an enlarged cross-sectional view of the scintillation fiber plate of the device.

As shown in FIG. 3, the core glass part 31 on one surface of the scintillation fiber plate 1 is the clad glass.
The core glass 31 is removed to a depth of about 30 mm with respect to 30 to form a recess.

Then, the concave portions are filled with scintillation material particles (zinc sulfide containing several% of silver) having a particle diameter of about 2 μm.

Cadmium sulfide containing a few percent of silver can likewise be used as scintillation material particles. An aluminum metal back layer 33 is further formed on the surface.

The scintillation light generated by the β rays incident from the metal back layer 33 side of the scintillation fiber plate 3 can be extracted to the other surface.

The scintillation fiber plate 3 is manufactured by the following steps.

A core glass portion on one surface of the fiber plate is etched to a substantially constant depth by etching with an acid to form a large number of recesses.

The classification step prepares scintillation material particles having a substantially uniform particle size from scintillation material particles having various particle sizes. This classification is performed by the sedimentation method.

In the filling step, the scintillation material particles having a substantially uniform particle size obtained in the classification step are filled in the concave portion of the fiber plate by centrifugal filling. A solution containing an organic adhesive and a dispersant can be used in the filling step.

A thin film of aluminum that transmits radiation and reflects scintillation light is formed by vapor deposition on the surface of the scintillation fiber plate that is filled with scintillation material particles.

The device according to the invention is used to record the distribution of radioactive material within a material by recording an image formed by the accumulation of very weak scintillation light due to one radiation particle from the surface of the material containing the radioactive material. It can be quantified.

The biological tissue of the experimental animal containing the radioactive isotope ¹⁴ C as Sample 2 (20 cm x 20 cm x several tens of μm rat tissue)
An example of using will be described.

The incident surface of the scintillation fiber plate 3 is arranged extremely close to the sample 2 placed on the sample table 1.

The entrance face plate 50a of the image intensifying device 5 is arranged in close contact with the exit face of the scintillation fiber plate 3.

A plurality of visible (or ultraviolet) light quanta are generated in the scintillation fiber plate 3 for each β-ray quantum generated by the radioisotope ¹⁴ C.

This scintillation light image is an entrance face plate 50 of the image intensifier 5.
It is incident on the photocathode 51 of the image intensifying device 5 via a.

As shown in FIG. 2, the entrance window 50a of the vacuum container 50
The exit window 50b and the exit window 50b form a part of the vacuum container, and the entrance window 5b
The photocathode 51 is on the inner surface of 0a, and the fluorescent surface 5 is on the inner surface of the exit window 50b.
5 are arranged.

A mesh 52 close to the photocathode 51 in the vacuum container 50,
Next, electron lens electrode 53, micro channel plate
54 are arranged in this order.

The microchannel plate 54 is a two-dimensional electron image intensifier having an infinite number of continuous dynodes. Particularly, in this embodiment, in order to increase the sensitivity of the secondary electron multiplication, two sets of microchannel plates having channels having different inclinations with respect to the tube axis are used.

Electron multiplication of about 10 ⁶ is possible with two microchannel plates.

An operating voltage is supplied to each electrode of the image intensifying device 5 from the power source 8 of the image intensifying device, and photoelectrons emitted from the photocathode 51 are accelerated by the accelerating electric field generated by the mesh electrode 52 to cause electron lens electrode 53. The microchannel plate 54 is focused by the microchannel plate 54 while maintaining the relationship corresponding to the generation position.
Is incident on the incident surface of.

The electron group multiplied by the microchannel plate 54 is the fluorescent surface to which the highest potential is given in this image intensifier 5.
When it is made incident on 55, fluorescence is generated at that position.

The light emitted from the fluorescent surface 55 is imaged by the image pickup tube 6 via the lens 60.

A low afterimage vidicon is used as the image pickup tube 6. Afterimages hinder quantification.

An operation voltage and a deflection current are supplied to the image pickup tube 6 from a scanning and operation power supply circuit 7. Scanning is done at the standard television rate.

The video signal output from the image pickup tube 6 is input to the image processing device 9.

The image processing device 9 includes an A / D converter for A / D converting the video signal, a CPU for performing image processing such as binarization on the digitized signal, and a pixel corresponding frame memory 91 for storing the processing result. It is provided.

FIG. 4 shows the image of the fluorescent surface (FIG. 4I) appearing on the output surface 50a of the image intensifying device 5 and the frame memory of the image processing device 9.
It is explanatory drawing which shows correspondence with 91 (FIG. 4 II).

The parallel horizontal lines in FIG. 4I correspond to the horizontal scanning lines of the television.

Further, FIG. 11 shows a region corresponding to pixels.

The concentric image appearing in FIG. 4I is an image resulting from the multiplication of photoelectrons due to one β-ray particle in the microchannel frame.

FIG. 4I shows an image when three β-ray particles are generated almost at the same time.

The contents of the frame memory 91 are constantly displayed on the television monitor 13, and the user can always observe the cumulative state of radiation emission.

Further, the contents of the frame memory 91 can be recorded in the image recording device 12 at the end of the measurement. A command for starting / stopping the entire system is input from the operator console 11 by the operator, and the control signal is transmitted from the control signal generating circuit 10 to the above-mentioned units.

As described in detail above, the embodiments according to the present invention can be variously modified within the scope of the present invention.

In the above embodiment, an example of image formation by accumulating output patterns of single radiation quantum has been described in detail.

It is possible to calculate the center of gravity of this output pattern and perform calculations for improving the image quality.

If you check the relationship between the RI amount and the number of photoelectrons in advance,
The RI amount can be quantified by determining the number of photoelectrons in the region of interest.

In addition, the device, by illuminating the sample with normal illumination light,
It is possible to memorize the structure in advance and then perform the above-mentioned measurement with the same camera and superimpose the radiation images for examination.

(Effects of the Invention) As described in detail above, in the radiation image detecting device according to the present invention, a large number of scintillation material particles are filled and fixed in each recess formed by engraving the core glass portion of one surface to a substantially constant depth. The scintillation fiber plate, and the photocathode is connected to the scintillation fiber plate via the fiber plate, the scintillation light is photoelectrically converted and multiplied by the microchannel plate, and then incident on the fluorescent surface to the scintillation fiber plate. An image intensifying device for forming an image corresponding to one radiation quantum unit, a television image taking device for taking an image of a fluorescent surface of the image intensifying device, and a video showing a generation position of a fluorescent image obtained for each of the image takings. Image processing apparatus that processes signals, stores them in a frame memory, and stores the occurrence frequency for each position And an output device for outputting the processing result.

Since there is no room for noise light to be mixed in the process of the scintillation light reaching the photocathode, each radiation quantum image can be extracted in the video signal with a good signal-to-noise ratio.

Then, the dynamic range of the image detection result can be made extremely large by adding this in pixel units, so that highly accurate quantification is possible.

Since the image intensifying device according to the present invention has extremely high sensitivity as described above, it is possible to detect a radiation image in a shorter time than any of the above-mentioned measuring methods.

In the device according to the present invention, since the image pickup portion and the output portion are constructed separately, the operation and the monitor can be performed in different rooms.

Further, as described above, since the detection state can be monitored in real time, failure in image detection can be prevented in advance.

In the past, in many cases, it was not possible to know how the detection was progressing until the film development was completed.

The resolution of the scintillation fiber plate used in the device according to the invention is very good. It has been confirmed that it has a spread of 10 μm (FWHM) when it is incident through a slit of 5 μm width of gold foil using ¹⁴ C as a β-ray source.

The scintillation material is firmly fixed with an adhesive or the like mixed in a solvent, and is further provided with a metal back.

Therefore, the sample labeled with the radioactive substance can be directly brought into contact with the scintillation fiber plate.

Also, since the scintillation material is packed in the recess,
The scintillation material is less likely to be contaminated by the sample.

As a result, a weak scintillation light image can be detected with high resolution.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the radiation detecting apparatus according to the present invention. FIG. 2 is a view showing the scintillation fiber plate, the image intensifying device, and the image pickup device taken out of the device, and the image intensifying device is shown broken along a plane including the tube axis. FIG. 3 is an enlarged cross-sectional view of the scintillation fiber plate of the device. FIG. 4 is a schematic diagram showing the output surface of the image intensifier tube and the contents of the image storage device in contrast. 1 ... Sample stage, 2 ... Sample 3 ... Scintillation fiber plate 30 ... Clad glass 31 ... Core glass 32 ... Scintillation material particles 33 ... Metal back (aluminum thin film) 5 ... Image intensifier, 6 ... Camera tube 7 ... Scan control device , 8 ... Power source of image intensifying device 9 ... Image processing device, 10 ... Control device 11 ... Operation console, 12 ... Image storage device 13 ... Monitor

Claims (4)

[Claims] 1. A scintillation fiber plate in which a large number of particles of scintillation material are filled and fixed in each of the recesses formed by engraving a core glass portion on one surface to a substantially constant depth, and the scintillation fiber plate via the fiber plate. A photocathode is connected, and an image intensifier for photoelectrically converting scintillation light and multiplying it by a microchannel plate to form an image corresponding to one radiation quantum unit incident on the scintillation fiber plate on the fluorescent surface, A television image pickup device for picking up an image of the fluorescent surface of the image intensifying device, and a video signal indicating the position of occurrence of the fluorescent image obtained for each image pickup, processed and stored in a frame memory, and the frequency of occurrence for each position. And an output device for outputting the processing result. The radiation image detecting device for detecting an image of the radiation incident on Aibapureto. 2. The radiation incident on the scintillation fiber plate is generated from a radiation source located proximate to the surface of the scintillation fiber plate on which the scintillation material particles are provided. The radiation image detecting device according to item 1. 3. The radiation image detecting device according to claim 1, wherein the scintillation material particles of the scintillation fiber plate are particles in which silver is added to zinc sulfide or cadmium sulfide. 4. The radiation image detecting device according to claim 1, wherein a metal thin film which transmits radiation and reflects scintillation light is provided on a surface of the scintillation fiber plate which is filled with the scintillation material particles. .