JPS6085383A - Radiation imaging apparatus - Google Patents

Abstract

PURPOSE:To increase the detection efficiency by an inexpensive and handy means by arranging a one-dimensional array of coded aparture in a multilayer with a partition. CONSTITUTION:As rays released from a sample 1 are absorbed when hitting metal plates of slits 23, components parallel with the metal plates only pass through the slits 23. Since the separation and extraction of image information were done in the way vertical to the metal plates of the slits 23 at this stage of process, the 2-D image will be obtained in the distribution of radioactive material if the separation and extraction of image information can be done in the way parallel to the metal plates at the subsequent stage. This can be accomplished by a space modulation with an aparture 24 and an image reproduction with a signal processor 3. Rays released at a point of the sample 1 forms a silhouette on the surface of a camera 22 as similar to the pattern of the aparture opening as passing through the aparture 24. As the opening pattern of the aparture 24 is previously known, the point at which the radiation is given can be calculated backward on the sample 1 from the silhouette on the camera 22.

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a radiation imaging device that one-dimensionally detects γ (ganoma) rays or X-rays emitted from radioactive substances and images the spatial distribution of the radioactive substances. [Prior Art] This type of device has traditionally been used as a type of ME equipment in scintillation cameras, which measure and record from outside the body the state of accumulation and distribution of radioisotopes administered to a subject in the body for diagnosis. It usually has the configuration shown in FIG. In other words, the gamma ray camera detection unit 2 one-dimensionally detects gamma rays a emitted by the subject l in which radioactive substances are accumulated. It consists of a signal processing device 3 and a display device, and the gamma ray camera detection section consists of a parallel multi-hole collimator 2 and an Anger type force meter. Radioactive substances distributed inside the subject emit γ-rays a' and
This γ-ray emission is isodirectional in all azimuth directions, and γ
Only gamma rays in a certain direction toward the camera are transmitted and detected by the collimator 2/ of the ray camera detection section. The transmittance of gamma rays is typically about 10-3 to 0-'' per hole. The transmitted gamma rays are then absorbed and detected by a camera, 2.2.

[Of the gamma rays emitted from the subject l. Only the component parallel to the hole of the collimator 2/ (therefore perpendicular to the camera plane) is selectively transmitted to form a γ-ray image. camera,! , 2 (γ detected from C
The lines indicate position signals (x,
y coordinate) and a gamma ray energy signal to the signal processing device 3, where it undergoes appropriate processing and is stored in a memory (not shown). These incoming gamma ray events are sequentially processed and displayed on the display device after counting for a certain period of time. By the way, the collimator used in the conventional device shown in Fig. 1 is mainly a parallel porous collimator made of heavy metal such as lead, and the holes are adjusted depending on the nuclide of the radioisotope to be measured or the purpose of diagnosis. Various collimators with different densities are used. In general, a collimator increases the resolution (thus reducing the hole diameter and increasing the number of holes).
There is a trade-off relationship between resolution and detection efficiency, such that if the detection efficiency is increased (therefore, the hole diameter Y is increased and the number of holes is decreased), the resolution is decreased. In recent years, it has become common practice to administer a large amount of a low-energy radioactive isotope with a short half-life, such as Tc-99m, to a subject and then take a scintigram. When using low-energy nuclides, it is necessary to use a high-resolution, low-detection-efficiency collimator and a low-resolution, high-detection-efficiency collimator depending on the purpose of use, which poses the problem of having to replace and remove heavy collimators. In addition, the determining factor of the image quality of the device is the geometric efficiency due to the collimator's hole diameter, and in the case of a typical parallel hole collimator, it is as low as 10-j-10-'' and has the disadvantage of poor resolution due to the limit due to quantum characteristics. [Summary of the Invention] This invention was made to solve the problems of the conventional device as described above. [Embodiments of the Invention] The present invention will be described in detail below with reference to Examples. Fig. 1 shows a radiation imaging apparatus according to the present invention. 2A is the gamma ray camera detection section.The gamma ray camera detection section consists of two people holding the camera, two units, and a metal plate at regular intervals. The slit 23 is made of a metal plate in which narrow openings extending in a direction perpendicular to the metal plate 23 are arranged in a fixed arrangement. 3 is a camera, This is a signal processing device that processes signals, and is similar to 3 in Figure 1.D is also similar to that shown in Figure 1, and the distribution of radioactive substances is calculated by image data processed in signal processing device B. This is a display device for displaying an image. In the above-mentioned radiation imaging device, the gamma rays emitted from the subject L are absorbed when they hit the metal plate of the slit 23, so only the components parallel to the metal plate are absorbed by the slit. 23
pass through. At this stage, the image information in the direction perpendicular to the slit and the metal plate 23 has been separated and extracted, so if the image information in the direction parallel to the metal plate can be separated and extracted in the following steps, it is possible to separate and extract the image information in the direction parallel to the metal plate. A dimensional image is obtained. This is accomplished by spatial modulation by the aperture 2 and image reproduction by the signal processing device 3. Now, the separation and extraction in the direction perpendicular to the metal plate of the slit copter 3 is being performed, so the gamma rays (having a traveling direction extending in the /gg direction within this plane) that have passed between the adjacent metal plates are k How this is separated and extracted within this plane will be explained below. The problem is a one-dimensional ring element, so to explain Figure 3, in Figure 1,
The gamma rays emitted from one point on the subject L are transmitted through the aperture 2'
1 When the heat passes, a silhouette of Aiiri appears on the aperture opening pattern! It is created on the surface of the camera 22. Since the opening pattern of the aperture 2 is set in advance, the camera! From the silhouette on a, it is possible to back-calculate which point on the subject is responsible. This is the same even when a large number of γ-ray sources are distributed in the subject, and the distribution of the γ-ray sources in the subject is set to 0 (branch), aperture, ! Pattern q is A (support), camera Ω
If the silhouette formed on λ is P (support), then P(xi) =Σ0・(xJ)・A(X1→Xj)j However, +Xn=η1muX, so from the above equation, 0(2 )ヲ〃? I ended up going. ■) It is known that there is an A (branch) that can be easily converted from an O (branch), and according to this, Abacha butter/
All you have to do is decide on A (branch). A well-known example is a pseudorandom binary sequence (“l” and “0”).
(permutations), and 5M-sequences, 1.2-order remainder sequences, etc. are widely used. In this case, there is an inverse sequence G that is ΣA(xi)・I G(xi+xj)−δIJ, so using this G from the shadow picture formed on the camera 2.2, O can be easily obtained as follows. Round knee Σ0(xj) δjk 1 = O(xk) Therefore, if this reproduction operation is performed in the signal processing device @3, images in one-dimensional direction can be separated and extracted, and a one-dimensional image can be obtained as a whole. Note that binary In the case of a series, the aperture pattern may be set as an opening and a shield corresponding to l'' and 0''. In the above, it has been shown how a distribution image of radioactive substances can be obtained using the apparatus of the embodiment shown in FIG. [Effects of the Invention] Such a device has a high degree of freedom in selecting an aperture pattern, and can obtain a much higher force line transmittance than a conventional parallel porous collimator. In the above-mentioned M-series and quadratic remainder series, since ゛pa and ゛O'' appear at the same time, the transmittance becomes SO%.Because of such a high transmittance, the statistical accuracy due to quantum characteristics improves, Even with regeneration processing calculations, the signal-to-noise ratio (SNR) is improved compared to the conventional parallel-hole collimator method.The degree of improvement is expressed as follows: where L is the camera dimension and 1 is the spread of the radioactive material distribution. L/21, so now L =
If 'I 00 mm , 1-=30 mm, it will be improved by a factor of two. Since the SNR based on quantum statistics is determined by the square root of the detection efficiency, this is equivalent to an improvement of twice as much as a detection seedling. 1 Therefore, the resolution (discrimination), which was limited by quantum characteristics in conventional devices, will be improved.7 In addition, in the above embodiment, a slit was provided between the aperture and the camera; It may be provided between the test object and the subject, or it may be provided on both. Furthermore, the opening of the aperture is elongated and spans the entire length of the aperture in one direction, and the same pattern is used for all of the thin layered spaces created by the metal loading forming the slit. Also, in the above embodiment, the slit metal plate? Since they are all arranged in parallel, the image will not be enlarged or reduced, but if the metal plates of the slits are arranged so that their extension planes intersect in one straight line, it is of course possible to enlarge or reduce the image. . As described in detail above, according to the present invention, image information in one direction is separated and extracted using the aperture Y with high gamma ray transmittance, and furthermore, image information is separated and extracted in one direction using the aperture Y having a high gamma ray transmittance, and furthermore, between the aperture and the camera, or between the aperture and the subject Since slits in which thin shielding plates are arranged at regular intervals are provided on both sides to separate and extract image information in the other direction, a radiation imaging device with high detection efficiency and resolution can be obtained with a simple device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a radiographic image knob device according to the prior art, FIG. 1 is a block diagram showing a radiographic image knob device A' according to the present invention, and FIG. 3 is a diagram showing spatial modulation by the aperture of the present invention. be. In addition, in the figure... Subject, Yu and two people... γ-ray camera detection unit 5U/...
・Parallel porous collimator 5.2 pieces...Unger type camera,
-23...slit, 2q...aperture, 3...signal processing device, da...display device. In each figure, the same reference numerals indicate the same or corresponding parts. Agent Masu Oiwa Yudokoro 2 Figure 3 Note 3 Figure 2 P(x)

Claims (1)

[Claims] (1) γ-rays or X-rays emitted from a radioactive substance are detected one-dimensionally using a radiation detector, and the spatial distribution of the radioactive substance is detected by the output signal of the radiation detector. In a radiation imaging device for imaging, an opening is provided between the radioactive substance and the radiation detector, allowing γ-rays or X-rays traveling from the radioactive substance to the radiation detector to pass or be blocked according to a certain spatial pattern. an aperture is arranged between the aperture and the radioactive substance, or between the aperture and the radiation detector,
Or a thin shielding plate with a constant interval t on both of them so as to transmit only the component parallel to the plane of gamma rays or X-rays traveling from the radioactive substance to the radiation detector!
This radiation imaging device is characterized by an array of slits. (λ) The aperture has narrow openings extending in one direction arranged in parallel5. 2. The radiation imaging apparatus according to claim 1, wherein said opening is provided perpendicularly to a shielding plate forming a slit 'ir. (3) The radiation imaging apparatus according to claim 1 or λ, wherein the arrangement of the openings of the aperture in the direction perpendicular to the shielding plate of the slit is an M-sequence or a quadratic remainder sequence. (i) The radiation imaging apparatus according to claim 1, wherein the shielding plates forming the slits are arranged so that their extended planes intersect with seven straight lines. (!r) In the aperture, narrow openings extending in one direction are arranged in parallel, and the openings are orthogonal to a straight line formed by intersecting the extended plane of the shielding plate forming the slit. The radiation imaging device according to item 1. (A) The arrangement of the aperture openings in the direction perpendicular to the straight line formed by intersecting the extension plane of the slit shielding plate is M-
The radiation imaging apparatus according to claim 1 or 2, which is a sequence or a quadratic remainder sequence.