KR20100103249A - Compton camera - Google Patents

Abstract

PURPOSE: The compton camera firstly grasps the case of getting the excellent image by comparing the result images according to the detected energy and the secondly detected energy. CONSTITUTION: Detection units(11, 12, 13, 14) detecting the radiation which is income are arranged in the x-axis direction and y-direction. The detection unit comprises the first detection unit and the second detection unit. The first detection unit diffuses the radiation which is income. The second detection unit absorbs the scattered radiation as described above. Detection units are altogether formed into structure and the same size.

Description

Compton Camera

The present invention relates to a device for detecting radiation, and more particularly to a Compton camera.

In response to the recent increase in the demand for new modern diseases and the accompanying high-tech diagnostic equipment, interest in nuclear medicine is drawing attention. Nuclear medicine is a medical specialty that injects radioisotope drugs into the human body to acquire morphological and biological information of diseased tissues with state-of-the-art medical cameras to explore the physiology and pathology of the human body and apply them to the diagnosis and treatment of diseases. to be.

The principle of the medical gamma camera is to detect the gamma rays emitted from the radiopharmaceuticals selectively ingested into the tumor, enter a scintillation crystal, convert them into photons of low energy, and then image the detection positions of the gamma rays. To diagnose the size, shape, and shape.

However, a conventional gamma camera using a mechanical collimator is effective to detect radiation of low energy, but has a problem in that efficiency is reduced and image noise is increased when detecting radiation of medium or high energy. On the other hand, electronic calibrators such as Compton cameras have high efficiency in obtaining images of medium to high energy radiation and have low image noise, which is suitable for detecting medium and high energy radiation.

Common Compton cameras are classified into primary scattering detector and secondary absorption detector. In other words, when the radiation is scattered by the primary detector and absorbed by the secondary detector, the radiation detection position information and energy information of each of the primary and secondary detectors may be combined to reversely project the direction of the radiation. By the way, when the order is divided into a primary detector and a secondary detector by using a shield or the like, the detectable radiation region is limited by the positions and shields of the two detectors. Therefore, there is a limit that the radiation incident region that can be detected is reduced by that amount.

On the contrary, when the order of the detectors is not distinguished without using a radiation shield or the like, there is a problem in that the detection area of the radiation is greatly widened, but it is difficult to find out which detector reacted from which.

The present invention provides a Compton camera capable of efficiently finding the position and type of radiation incident from various directions.

According to an aspect of the present invention, a pair of first detection units disposed in parallel with the x-axis and spaced apart from each other face each other; And a pair of second detectors disposed in a direction parallel to the y-axis so as to be adjacent to the first detector and spaced apart from each other.

A pair of third detectors may be further disposed in parallel with the z-axis to be adjacent to the first detector and the second detector, and spaced apart from each other to face each other, wherein the distance between the pair of first detectors is 160 mm. It may be In addition, the first detector, the second detector, and the third detector may be disposed to form a cube-shaped space inside.

On the other hand, the pair of first detection unit may be made of a scintillator and an optical sensor coupled to one surface of the scintillator, respectively, as main components. The scintillator may be made of a material including LaCl ₃ (Ce), wherein the scintillator may have a thickness of 20 mm to 30 mm.

As a light sensor, a position sensitive photomultiplier tube can be used.

The signal processor may further include a signal processor configured to receive information acquired by the pair of first detectors, and the signal processor may determine the detection order therebetween by comparing energy information acquired by each pair of first detectors. have. When the energy of the incident radiation is 1700 keV or less, the signal processor may determine the detection unit in which less energy information is acquired as a priority.

According to a preferred embodiment of the present invention, it is possible to efficiently find the position and type of radiation incident from various directions.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention.

Hereinafter, preferred embodiments of the Compton camera according to the present invention will be described in detail with reference to the accompanying drawings, and in the following description with reference to the accompanying drawings, the same or corresponding components are given the same reference numerals and duplicated thereto. The description will be omitted.

1 is a perspective view of a Compton camera according to an embodiment of the present invention. Referring to FIG. 1, the Compton camera 10, the detectors 11, 12, 13, and 14, the scintillators 21, 22, 23, and 24, and the photosensors 31, 32, 33, and 34 are shown. .

In the Compton camera 10 according to the present embodiment, the pair of detection portions for detecting incident radiation S ₁ and S ₂ is not disposed only in the x-axis direction, that is, in the direction parallel to the x-axis, but in the y-axis direction. It also has a structure that is arranged. At this time, a separate shield (not shown) may be disposed in the z-axis direction in which the detector is not disposed.

Each detector 11, 12, 13, 14 is paired with a primary detector in which incident radiation S ₁ , S ₂ is scattered and a secondary detector in which scattered radiation is absorbed. Accordingly, in the present embodiment, as shown in FIG. 1, four detection units 11, 12, 13, and 14 are paired with each other to form a wall facing each other. However, in the case of the Compton camera 10 according to the present embodiment, since the radiation incident from the side front direction (x-axis direction and y-axis direction) is detected, the same order as the first and second described above is absolute. Rather, it has a relative meaning which can be determined according to the direction of the incident radiation.

Meanwhile, the four detection units 11, 12, 13, and 14 may all have the same structure and size. As such, when all four detection units 11, 12, 13, and 14 have the same structure and size, it is possible to expect the effect of evenly measuring the lateral omnidirectional direction. However, the structure and size of some detectors may be designed differently from the others, depending on the design needs.

Each of the detectors 11, 12, 13, and 14 may include scintillators 21, 22, 23, and 24, and optical sensors 31, 32, 33, and 34 coupled to one surface thereof. At this time, each of the detectors 11, 12, 13, and 14 may be disposed such that the scintillators 21, 22, 23, and 24 face each other, as shown in FIG. 1. LaCl ₃ (Ce) may be used as the scintillator 21, and other materials such as NaI (Tl), ZnS (Ag), CsI (Tl), LiI (Tl), etc. may be used as necessary.

2 is a perspective view of a Compton camera according to another embodiment of the present invention. Referring to FIG. 2, the Compton camera 10 ′, the detectors 11, 12, 13, 14, 15, and 16, the scintillators 21, 22, 23, 24, 25, and 26, and the photosensors 31 and 32. 33, 34, 35, 36, a signal processor 40, and an image processor 50 are shown.

2 differs from the embodiment shown in FIG. 1 in that a pair of detectors 15 and 16 are also disposed in the z-axis direction. Through this structure, the Compton camera 10 ′ according to the present embodiment can detect all radiation incident from all directions. Hereinafter, the Compton camera 10 'according to the present embodiment will be described based on differences from the above-described embodiment.

In the present embodiment, as shown in Fig. 2, the six detection units 11, 12, 13, 14, 15, and 16 are paired to face each other so as to partition a cube-shaped space inside.

Meanwhile, all six detection units 11, 12, 13, 14, 15, and 16 may have the same structure and size. That is, as shown in Figure 2, all six detection units (11, 12, 13, 14, 15, 16) is formed in a rectangular shape having a rectangular cross section, the size is also the same, the cube shape inside It may have a structure in which a space is formed. As such, when all six detection units 11, 12, 13, 14, 15, and 16 have the same structure and size, it is possible to expect the effect of evenly measuring the omnidirectional. However, the structure and size of some detectors may be designed differently from the others, depending on the design needs.

Hereinafter, the structure and function of each detector 11, 12, 13, 14, 15, and 16 will be described with reference to FIGS. 1 and 2.

When the radiation S ₁ is incident on the scintillator 21, 22, the incident radiation S ₁ causes photoelectric effect and compton scattering in the scintillator 21, 22. The electrons generated by this interaction The photon mechanism generates photons having a wavelength in the visible light region by the scintillation mechanism. Photons generated in this way are collected by the optical sensors 31 and 32, and the positional information and the energy information of the incident radiation therefrom can be grasped.

At this time, there is a fear that the spatial resolution is lowered by scattering of the generated flashes. Thus, to prevent scattering of glare, the scintillator 21 may be pixel structured, as shown in FIG. 3. Flashes generated in the pixel-structured scintillator generate total reflection at the pixel wall due to the difference in the refractive index between the scintillator and the air, thereby preventing the scattering of the scintillation. The size and the like of each pixel 21a may be variously changed according to design needs. As a method for implementing the pixel structure of the scintillator 21, a MEMS process may be used, and various other methods may be used.

Position-sensitive photomultiplier tubes (PSPMT) may be used as the optical sensors 31 and 32 in which photons generated from the scintillators 21 and 22 are collected. The photomultiplier tube includes a photocathode (not shown), a dynode (not shown), an anode (not shown), and the like. Photomultiplier tube is a very fast amplifier, generally by amplifying the visible light pulse is incident during 1ns 10 ⁶ times the.

The inside of the photomultiplier tube is in a vacuum state, and the number of dynodes is usually 15 or more. Applying a progressively increased high voltage to each die node allows the photoelectrons to proceed to the next die node by the electric field generated at this time.

The photocathode of the photomultiplier tube converts photons generated in the scintillator into photoelectrons. The metal mainly used as the photocathode is a multi-alkali metal material based on Na ₂ KSb compound. The photoelectrons that pass through the potential barrier of the vacuum multiply through several dynodes and finally reach the anode. Electrons acquired at the anode of the photomultiplier are made of measurable electrical output pulses.

Meanwhile, in the present embodiment, the photomultiplier tube is presented as the optical sensor 31, but other types of optical sensors such as photodiodes may be used.

The output pulse is provided to the signal processor 40 and processed, and the processed signal is provided to the image processor 50 and converted into an image. The signal processor 40 may be formed of various functional modules (not shown) for processing an electrical position signal, and the image processor 50 may implement an image by converting an analog signal transmitted from the signal processor 40 into digital. have.

Meanwhile, an aiming device (not shown) may be attached to the detection units 11, 12, 13, 14, 15, and 16. Aimator (not shown) is a means for geometrically restricting the detection of only a source having a desired directionality, there are various types according to the detection site and purpose. Representative sights include parallel hole collimators and diverging collimators.

Hereinafter, the operation of the Compton camera 10 according to the embodiment shown in FIG. 1 will be described. Of course, the operation principle described below also applies to the Compton camera 10 'according to the embodiment shown in FIG.

For convenience of understanding, the detector 11 shown on the left side of FIG. 1 will be referred to as the primary detector and the detector 12 shown on the right side as the secondary detector.

Referring to FIG. 1, when radiation S ₁ is incident from the left side (negative direction of the x-axis), the primary detection unit 11 acquires primary position information and primary energy information of the incident radiation S ₁ . Done. The primary information thus obtained is transferred to the signal processor (40 in FIG. 2).

Meanwhile, the radiation S ₁ incident on the primary detection unit 11 is scattered while passing through the scintillator 21 of the primary detection unit 11, and the scattered radiation is disposed on the opposite side of the secondary detection unit 12. ) Is incident. When the scattered radiation is incident on the secondary detector 12, the secondary detector 12 acquires secondary position information and secondary energy information of the incident radiation. The secondary information thus obtained is also transmitted to the signal processor (40 of FIG. 2).

The signal processor 40 of FIG. 2 obtains information on the position and type of the radiation source S ₁ from the primary information and the secondary information transmitted from the primary detector 11 and the secondary detector 12, respectively. This is again transmitted to the image processor (50 of FIG. 2) is implemented as an image.

In addition, the radiation S ₂ incident in the negative y-axis direction is also detected by the detectors 13 and 14 in the y-axis direction, so that the signal processor (40 in FIG. 2) and the image processor (50 in FIG. 2) are detected. After that, it can be implemented as an image.

As such, the Compton camera 10 according to the present exemplary embodiment may exhibit an effect of detecting not only the radiation S ₁ incident in the x-axis direction but also the radiation S ₂ incident in the y-axis direction. In the case of the Compton camera 10 'of FIG. 2 in which a pair of detectors 15 and 16 are arranged in the z-axis direction, radiation can be detected not only in the x- and y-axis directions but also in the z-axis direction. This makes it possible to detect omnidirectionally.

On the other hand, when the scintillator 21 becomes thicker, the detection efficiency is improved, but the radiation scattered by the primary detector 11 is absorbed without exiting the primary detector 11 itself, and the information from the secondary detector 12 is absorbed. There is a fear that the image cannot be reconstructed because it is not available. In consideration of this, when the scintillators 21, 22, 23, 24, 25, and 26 are made of LaCl ₃ (Ce) as a main material, the thickness thereof may be 20 to 30 mm, more preferably 25 mm. have.

In addition, considering that the resolution of the image increases as the distance between the scintillators 21, 22, 23, 24, 25, and 26 increases, the detection efficiency decreases, the distance between the detection units facing each other may be preferably 160 mm or less. .

In the present embodiment, since each detector can simultaneously play the role of the primary detector (scattering detector) and the secondary detector (absorption detector) according to the direction of incidence of the radiation, all the radiations coming from all directions are irrespective of the direction. Can be detected. However, such a structure may cause a problem that it becomes difficult to grasp the order from which detection unit a reaction occurs when the first-second / second-order radiation is made. This is because the primary and secondary detection of radiation occur almost simultaneously, so there is a limit in classifying the detection order by time information.

In consideration of this point, a method of determining the detection order by comparing the magnitudes of energy obtained by the two detection units may be used. That is, the case where the first detected energy is smaller than the second detected energy is divided into the opposite case and the resultant image is compared to determine the case in which the excellent image can be obtained.

Referring to FIG. 3, in the case of the image resolution (FWHM), the case where it is determined that the energy of the first detection is smaller than the energy of the second detection in all regions regardless of the energy of incident radiation (E1 <E2), and vice versa (E1>). It can be confirmed that it is superior to E2). Referring to FIG. 4, even when the standard deviation (inversely proportional to the detection efficiency) of the maximum point of the dotted circle image is obtained, it can be seen that the case where the energy of the first detection is smaller than the energy of the second detection is excellent in incident radiation lower than 1700 keV. . However, in the case of radiation exceeding 1700 keV, the standard deviation was lower when the energy of the second detection was smaller than the energy of the first detection.

Therefore, the detection unit with low detection energy is designated as the primary detection unit when the detection energy is lower than 1700 keV, and the detection unit with low detection energy is the primary detection unit when the image resolution is prioritized when the resolution is higher than 1700 keV. May be used as the primary detection unit.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

Many embodiments other than the above-described embodiments are within the scope of the claims of the present invention.

1 is a plan view showing a Compton camera according to an embodiment of the present invention.

2 is a perspective view of a Compton camera according to another embodiment of the present invention.

3 is a perspective view of a flashing body of the Compton camera according to an embodiment of the present invention.

4 is a graph showing a relationship between spatial resolution (FWHM) and energy of incident radiation (Energy).

5 is a graph showing the relationship between the standard deviation and the energy of incident radiation.

<Description of the symbols for the main parts of the drawings>

10, 10 ': Compton camera

11, 12, 13, 14, 15, 16: detector

21, 22, 23, 24, 25, 26: scintillation body

21a: pixels

31, 32, 33, 34, 35, 36: light sensor

40: signal processing unit

50: image processing unit

Claims (10)

a pair of first detectors disposed in parallel with the x-axis and spaced apart from each other; And Compton camera disposed in a direction parallel to the y-axis so as to be adjacent to the first detector, a pair of second detectors spaced apart from each other. The method of claim 1, And a pair of third detectors arranged in parallel with a z-axis so as to be adjacent to the first detector and the second detector, and spaced apart from each other to face each other. The method of claim 2, And the first detection unit, the second detection unit, and the third detection unit are arranged to form a cube-shaped space inside. The method of claim 1, The distance between the pair of first detection unit is less than 160mm Compton camera. The method of claim 1, The pair of first detection units, Compton camera each comprising a scintillator, and an optical sensor coupled to one surface of the scintillator. The method of claim 5, The scintillator is Compton camera made of a material containing LaCl ₃ (Ce). The method of claim 6, The thickness of the scintillator is 20 to 30mm Compton camera. The method of claim 5, The optical sensor is a position-sensitive photomultiplier tube Compton camera. The method of claim 1, And a signal processor configured to receive information acquired by the pair of first detectors. And the signal processing unit compares energy information acquired by each of the pair of first detection units to determine a detection order. 10. The method of claim 9, The energy of incident radiation is 1700 keV or less, And the signal processing unit determines a detection unit having less energy information as a priority.

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