KR102541734B1 - Positron emission tomography apparatus and method using multi-layer flat scintillator - Google Patents

Abstract

Embodiments of the present invention relate to a positron emission tomography apparatus and method, which includes a plurality of planar scintillators having a stacked structure and a plurality of optical sensors disposed on the sides of the scintillator, and the number of optical sensors for detecting gamma rays. To provide a positron emission tomography apparatus and method capable of generating tomography images without a complex structure of a scintillator and a signal processing circuit.

Description

Positron emission tomography apparatus and method using a multi-layer planar scintillator

Embodiments of the present invention relate to a positron emission tomography apparatus and method using a multi-layer planar scintillator, and more particularly, positron emission for measuring a gamma-ray detection depth using a multi-layer planar scintillator stacked in an incident direction of gamma rays. It relates to a tomography apparatus and method.

In general, radiation imaging devices in the medical field that can image biochemical changes in the human body to find abnormalities and early diagnose various diseases include magnetic resonance imaging (MRI) and computer tomography (CT). Tomography (CT) and Positron Emission Tomography (PET).

In the case of such a radiation medical imaging device, radiation is detected and converted into an optical signal, and an image signal for an object is acquired using the converted optical signal. In particular, PET is a device that injects a radiopharmaceutical that emits positrons into a living body by a method such as intravenous injection or inhalation, and detects it to image the body distribution of the radiopharmaceutical. PET is used in the diagnosis and research of various diseases such as metabolic studies of the human body, cancer diagnosis, heart and nervous system abnormalities.

Hereinafter, a general PET operation method will be described with reference to FIG. 1 .

1 is a diagram for explaining a process of generating an image in a general general PET device.

Referring to FIG. 1, PET is two gamma rays emitted when a positron (e ⁺ ) emitted when an unstable radiation sample undergoes beta+ decay (β+-decay) and pair annihilation with an electron (radiation) is detected and an image is created from it. Therefore, it is possible to know whether a disease has occurred and the exact location of the disease by taking a picture of the inside of the human body without a surgical operation.

Conventional PET can be largely classified into a method using an array scintillator and a method using a flat scintillator. In the case of using an array type scintillator, resolution is excellent, but there is a problem in that performance such as sensitivity and energy resolution is lower than that of a detector using a flat scintillator.

Also, referring to FIG. 1 , a detector 100 based on a thin and long arrayed scintillator is disposed in a circular shape inside the PET(1) scanner. Therefore, parallax error occurs in the outer field of view, and the resolution of the image is lowered. In order to solve this problem, a method of changing the number and coupling method of optical sensors coupled to the scintillator has been developed, but an optical sensor that is twice as large as the previous one is required, a complex signal analysis algorithm, or a preliminary measurement of light distribution by gamma ray detection depth. There is a problem that requires

An apparatus and method for detecting gamma rays using a multi-layer planar scintillator according to embodiments of the present invention are intended to provide a positron emission tomography apparatus and method capable of measuring a detection depth of gamma rays using a small number of optical sensors.

In addition, an apparatus and method for detecting gamma rays using a multilayer planar scintillator according to an embodiment of the present invention are intended to provide a positron emission tomography apparatus and method capable of deriving the depth of gamma rays using a simple algorithm.

In addition, the gamma ray detection apparatus and method using the multi-layer planar scintillator according to the embodiment of the present invention provide a positron emission tomography apparatus and method capable of detecting the depth of gamma rays without prior measurement of light distribution for each gamma ray detection depth. it is for

However, the technical problem to be achieved by the present embodiment is not limited to the technical problem as described above, and other technical problems may exist.

As a technical means for achieving the above-described technical problem, the positron emission tomography apparatus according to the embodiment generates a scintillation signal when gamma rays are incident, and a plurality of planar scintillators stacked in the direction of incidence of the gamma rays, The flat scintillator converts the scintillation signal into an electrical signal, uses a plurality of optical sensors stacked on four sides of the flat scintillator in the same direction as the stacking direction of the flat scintillator, and the electrical signal, and a signal processing unit for deriving a 3D value of the gamma-ray detection location having a midpoint as an origin and generating an image using the gamma-ray detection location.

In addition, the optical sensor according to the embodiment is stacked with two or more and less than or equal to the number of stacked flat scintillators.

In addition, the positron emission tomography apparatus according to the embodiment further includes a light guide disposed between the multi-layer planar scintillator and the multi-layer optical sensor, wherein the light guide diffuses the scintillation signal to generate light sent to the sensor.

In addition, the signal processing unit according to the embodiment detects the x-axis of the gamma ray using a difference between an electrical signal measured by an optical sensor disposed on a first side of the scintillator and an optical sensor disposed on a third side among the four sides of the scintillator. The position is derived, and the y-axis position of the gamma ray is derived using the difference between the electrical signal measured by the optical sensor disposed on the second side and the optical sensor disposed on the fourth side of the scintillator, and the stacked optical sensor The z-axis position of the gamma ray is derived using the ratio of electrical signals measured for each layer of the gamma ray, the z-axis is a direction in which the gamma ray is incident and indicates depth, the x-axis is the horizontal side of the red side of the scintillator, and the y-axis is the red It means a vertical direction of the side, the first side and the third side are perpendicular to the x-axis, and the second side and the fourth side are sides perpendicular to the y-axis.

In addition, in the plurality of flat scintillators according to the embodiment, reflectors are coupled between the plurality of scintillators and on the front and rear surfaces, the front surface means a surface on which the gamma rays are near, and the rear surface means a surface on which the gamma rays are incident. Means a bottom surface facing parallel to, and the reflector reflects the scintillation signal.

In addition, the positron emission tomography method according to the embodiment includes generating a scintillation signal when a plurality of planar scintillators stacked in the direction of incidence of gamma rays are incident with the gamma rays, on four sides of the planar scintillator. converting the scintillation signal into an electrical signal by a plurality of optical sensors disposed and stacked in the same direction as the stacking direction of the flat scintillator, and a signal processor using the electrical signal to determine the center point of the flat scintillator and deriving a 3D value of the gamma-ray detection position as an origin and constructing an image using the gamma-ray detection position.

In addition, the step of converting the scintillation signal into an electrical signal according to the embodiment further includes converting the scintillation signal into an electrical signal using optical sensors stacked at least two and less than or equal to the number of stacked flat scintillators. do.

In addition, in the step of converting the scintillation signal into an electrical signal according to the embodiment, the scintillation signal is diffused using an optical guide disposed between the plurality of flat scintillators and the plurality of optical sensors and transmitted to the optical sensor. Include more steps.

In addition, in the step of configuring the image according to the embodiment, the signal processing unit measures the difference between the electrical signal measured by the optical sensor disposed on the first side and the optical sensor disposed on the third side of the four sides of the scintillator. Deriving the x-axis detection position of the gamma ray using the difference between the electrical signals measured by the optical sensor disposed on the second side and the optical sensor disposed on the fourth side of the scintillator, the y-axis position of the gamma ray and deriving a z-axis position of the gamma ray using a ratio of electrical signals measured for each layer of the stacked photosensors, wherein the z-axis is a direction in which the gamma ray is incident and represents a depth. The x-axis is the horizontal direction of the red-side surface of the scintillator, the y-axis means the vertical direction of the red-side surface, the first side and the third side are perpendicular to the x-axis, and the second side and the fourth side are The side perpendicular to the y-axis.

In addition, the step of generating the scintillation signal according to the embodiment further includes reflecting the scintillation signal by a reflector coupled between the plurality of flat scintillators and to the front and rear surfaces, the front surface of which the gamma rays are incident. surface, and the rear surface means a bottom surface parallel to the surface on which the gamma rays are incident.

Positron emission tomography apparatus and method using multi-layer planar scintillators according to embodiments of the present invention may provide a gamma ray detection apparatus and method capable of measuring a detection depth of gamma rays using an optical sensor.

In addition, the positron emission tomography apparatus and method using the multi-layer planar scintillator according to an embodiment of the present invention can provide a gamma ray detection apparatus and method capable of deriving the depth of gamma rays using a simple algorithm.

In addition, the positron emission tomography apparatus and method using the multilayer planar scintillator according to an embodiment of the present invention provide a gamma ray detection apparatus and method capable of detecting the depth of gamma rays without prior measurement of light distribution for each gamma ray detection depth. can

1 is a diagram for explaining a process of generating an image in a general PET device.
2 is a configuration diagram of a positron emission tomography device according to an embodiment.
3 is a configuration diagram of a scintillator according to an embodiment.
4 is a configuration diagram of an optical sensor according to an embodiment.
5 is a configuration diagram of an optical sensor according to an embodiment.
6 is a side view of a detector according to an embodiment.
7 is a side view of a detector coupled with a light guide according to an embodiment.
8 is an exemplary diagram for explaining a gamma ray detection position measurement method according to an embodiment.
9 is a flowchart of a quantum beam emission tomography method according to an embodiment.
10 is an exemplary diagram to which Monte Carlo simulation is applied to describe performance of a positron emission tomography apparatus according to an embodiment.
11 is an exemplary diagram to which Monte Carlo simulation is applied to describe performance of a positron emission tomography apparatus according to an embodiment.
12 is an example of a gamma ray detection depth distribution graph according to an embodiment.
13 is an exemplary view of a 2D plane image for each gamma ray detection depth according to an embodiment.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part is said to be "connected" to another part, this includes not only the case where it is "directly connected" but also the case where it is "electrically connected" with another element interposed therebetween. . In addition, when a certain component is said to "include", this means that it may further include other components without excluding other components unless otherwise stated.

In this specification, a "unit" includes a unit realized by hardware, a unit realized by software, and a unit realized using both. Further, one unit may be realized using two or more hardware, and two or more units may be realized by one hardware. Meanwhile, '~unit' is not limited to software or hardware, and '~unit' may be configured to be in an addressable storage medium or configured to reproduce one or more processors. Therefore, as an example, '~unit' refers to components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, and procedures. , subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays and variables. Functions provided within components and '~units' may be combined into smaller numbers of components and '~units' or further separated into additional components and '~units'. In addition, the components and '~units' may be implemented to regenerate one or more CPUs in the device.

In addition, the accompanying drawings are only for easy understanding of the embodiments disclosed in this specification, the technical idea disclosed in this specification is not limited by the accompanying drawings, and all changes included in the spirit and technical scope of the present invention , it should be understood to include equivalents or substitutes.

Terms including ordinal numbers, such as first and second, may be used to describe various components, but the components are not limited by the terms. These terms are only used for the purpose of distinguishing one component from another.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this application, terms such as "comprise" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Hereinafter, the configuration of the positron emission tomography apparatus 1 according to the embodiment will be described with reference to FIG. 2 .

2 is a configuration diagram of a positron emission tomography device according to an embodiment.

Referring to FIG. 2 , the positron emission tomography apparatus 1 according to the embodiment includes a detector 100 that generates an electrical signal S3 corresponding to a detection position of gamma rays (radiation S1) when gamma rays (radiation S1) are incident on it. It includes a signal processing unit 200 that constructs an image by deriving a detection location of gamma rays using the electrical signal S3.

Specifically, the detector 100 includes a plurality of scintillators 110 and a plurality of photosensors 130 . The plurality of scintillators 110 generate a scintillation signal S2 in response to the incident gamma rays S1.

The scintillator 110 may include any material that emits light when radiation strikes it. In addition, it is used as a meaning including all terms referring to a scintillator material such as a scintillator crystal. In addition, the scintillation signal S2 includes all light signals such as light and visible light generated by the scintillator 110 in response to the incidence of radiation.

The plurality of optical sensors 130 generate an electrical signal S3 corresponding to the scintillation signal S2 generated by the plurality of scintillators 100 . Accordingly, the optical sensor 130 may use the scintillation signal S2 or all information included in the scintillation signal S2, such as the wavelength, amplitude, and frequency, to convert the electrical signal S3 into the electrical signal S3.

The signal processing unit 200 derives the gamma-ray detection position using an algorithm for deriving the gamma-ray detection position and the electrical signal S3 measured by the detector 100, and constructs an image based on the gamma-ray detection position. Accordingly, the performance of the positron emission tomography apparatus 1 may be determined by the structure of the gamma ray detector 100 and an algorithm for deriving the gamma ray detection position.

The gamma ray detector 100 generally uses either an array type scintillator in which a plurality of thin and long rectangular parallelepiped scintillators are combined or a flat planar scintillator that is a single rectangular parallelepiped block. In the case of using an array type scintillator, there is an advantage in that the resolution is excellent. However, the array type scintillator has a disadvantage in that performance such as sensitivity and energy resolution is lower than that of the flat scintillator.

In addition, when array-type scintillators are arranged circularly, parallax errors occur in the outer field of view, resulting in a problem in that the resolution of the image is lowered. At this time, resolution degradation due to parallax error increases as the diameter of the circular PET 1 decreases.

Therefore, in order to solve the resolution degradation problem, the resolution degradation problem has been conventionally solved by changing the structure of an arrayed scintillator or measuring the detection depth of gamma rays by changing the number and coupling method of optical sensors.

However, this complicates the structure of the scintillator or signal processing circuit, and increases the number of optical sensors by more than two times, thereby increasing the manufacturing cost of PET. In addition, data analysis time for deriving the gamma-ray detection location is excessively increased, and a complex signal analysis algorithm such as an expected value maximization location calculation algorithm is required.

Therefore, the positron emission tomography device according to the embodiment improves sensitivity and energy resolution by stacking thin flat scintillators in the incident direction of gamma rays and disposing the optical sensors 130 on four side surfaces. In addition, since an increase in the number of optical sensors and a complicated signal analysis algorithm are not required, manufacturing cost and time required to generate an image can be reduced. A specific configuration of the scintillator 130 will be described with reference to FIG. 3 to be described later.

Hereinafter, the configuration of the scintillator according to the embodiment will be described with reference to FIG. 3 .

3 is a configuration diagram of a scintillator according to an embodiment.

Referring to FIG. 3 , the scintillator 130 included in the detector 100 according to the embodiment has a structure in which a plurality of flat scintillators are stacked. A plurality of flat scintillators have a stacked structure such that the height increases in the incident direction D1 of gamma rays. In addition, a reflector 120 may be disposed between the plurality of flat scintillators 110 and at least one of the front and rear surfaces.

At this time, the front means a surface on which gamma rays are incident, and the rear means a bottom surface parallel to and facing the front. The thickness of the scintillator 110 may be set to 5 mm. However, the embodiment is not limited thereto, and the thickness may be changed according to the purpose of use and conditions of use.

In addition, the reflector 120 disposed on the bonding surface of the plurality of scintillators 110 reflects the scintillation signal S2. Therefore, when gamma rays (S1) are detected in any one layer of the scintillator 110 stacked with a plurality of layers and a scintillation signal (S2) is generated, the scintillation signal (S2) propagates only within the generated scintillator 110, It does not propagate to other scintillators 110 .

Hereinafter, the configuration of the optical sensor 130 according to the embodiment will be described with reference to FIGS. 4 and 5 .

4 is a configuration diagram of an optical sensor according to an embodiment.

Referring to FIG. 4 , optical sensors 130 according to the embodiment are disposed on four sides of the scintillator 110 . That is, among the six surfaces of the scintillator, the scintillator is arranged to surround the remaining four surfaces except for the two surfaces (front and rear) perpendicular to the incident direction (D1) of gamma rays.

When gamma rays S1 are incident on the scintillator 110, the scintillator 110 generates a scintillation signal S2. The plurality of optical sensors 130 may detect a scintillation signal generated by the scintillator 110 to derive a detection position of gamma rays. In order to derive the detection location of the gamma ray, PET according to the embodiment is parallel to each other, and the coordinates of the detection location of the gamma ray may be derived by comparing result values measured by optical sensors located on opposite surfaces.

5 is a configuration diagram of an optical sensor according to an embodiment.

Referring to FIG. 5 , the optical sensor 130 has a stacked structure in which the first optical sensor 130-1 is disposed on the upper side and the second optical sensor 130-2 is disposed on the lower side. That is, a plurality of optical sensors may be arranged such that the height increases in the incident direction of the gamma rays.

5 shows that the first optical sensor 130-1 and the second optical sensor 130-2 have a stacked structure, but this is an example and the embodiment is not limited thereto, and a plurality of optical sensors are stacked. structure can be placed.

Since the plurality of optical sensors 130 are arranged to have a stacked structure, the detection depth of gamma rays S1 can be measured even when the multi-layer flat scintillator 110 is used. Specifically, the detection depth of the gamma ray S1 may be measured using the ratio of the scintillation signal S2 detected in each layer of the optical sensor 130 having the stacked structure.

Therefore, in order to measure the detection depth of the gamma rays S1, the number of layers of the optical sensor 130 must be at least two. In addition, the number of stacked optical sensors 130 may be less than or equal to the number of scintillators 110 . However, the embodiment is not limited thereto, and as the number of layers of the optical sensor 130 increases, measurement accuracy of the detection depth of the gamma ray S1 may be increased.

A method of measuring the detection depth of gamma rays S1 will be described with reference to FIGS. 6 and 7 to be described later.

Hereinafter, a method of measuring the detection depth of gamma rays will be described with reference to FIGS. 6 and 7 .

6 is a side view of a detector according to an embodiment.

FIG. 6 shows an example of a detector 100 having three scintillators 110 and two optical sensors 130 . In addition, although not shown in FIG. 6 , a reflector 120 may be included between each scintillator 110 as shown in FIG. 3 .

When gamma rays S1 reach the first scintillator 110-1, the first scintillator 110-1 generates a scintillation signal S2. The scintillation signal S2 generated by the first scintillator 110-1 does not propagate to the second scintillator 110-2 by the reflector 120, but propagates to the first optical sensor 130-1 located on the side. do. Therefore, when gamma rays are detected by the first scintillator 110-1, the scintillation signal S2 is measured by the first optical sensor 130-1.

In addition, when gamma rays S2 reach the second scintillator 110-2, the second scintillator 110-2 generates a scintillation signal S2. The scintillation signal S2 generated by the second scintillator 110-2 is not propagated to the first scintillator 110-1 and the third scintillator 110-3 by the reflector 120, and the first scintillator located on the side It propagates to the optical sensor 130-1 and the second optical sensor 130-2. Accordingly, when gamma rays S1 are detected by the second scintillator 110-2, the scintillation signal S2 is measured by both the first optical sensor 130-1 and the second optical sensor 130-2.

When gamma rays S1 reach the third scintillator 110-3, the third scintillator 110-3 generates a scintillation signal S2. The scintillation signal S2 generated by the third scintillator 110-3 does not propagate to the second scintillator 110-2 by the reflector 120, but propagates to the second optical sensor 130-2 located on the side. do. Accordingly, when gamma rays (S1) are detected by the third scintillator 110-3, a scintillation signal is measured by the second optical sensor 130-2.

Accordingly, the detector 100 may derive the detection depth of the gamma rays using the intensity of the flash signal S2 measured by the first optical sensor 130-1 and the second optical sensor 130-2.

7 is a side view of a detector coupled with a light guide according to an embodiment.

7 shows an example of a detector 100 in which the number of scintillators 110 is four and the number of optical sensors 130 is two, and an optical guide 140 is provided between the scintillator 110 and the optical sensor 130. can be placed. In addition, although not shown in FIG. 7 , a reflector 120 may be included between each scintillator 110 as shown in FIG. 3 .

The light guide 140 is an optical fiber used to diffuse and transmit light. The light guide 140 helps transfer the scintillation signal S2 generated from the scintillator 110, thereby increasing the accuracy of measuring the detection depth of the gamma ray S1.

When there is no light guide 140, even if gamma rays (S1) are incident on the first scintillator 110-1 and the second scintillator 110-2, only the first optical sensor 130-1 generates a scintillation signal (S2). is measured, and the flash signal S2 is not measured in the first optical sensor 130-2. Therefore, when the light guide 140 is not inserted, it is difficult to distinguish the case where gamma rays (S1) are incident on the first scintillator 110-1 and the second scintillator 110-2, and the detection depth of gamma rays is accurately measured. Can not.

However, when the detector 100 includes the light guide 140, the scintillation signal S2 generated by the first scintillator 110-1 is transmitted to the first optical sensor 130-1, and some signals are It may be transmitted to the second optical sensor 130-2.

In addition, the scintillation signal S2 generated by the second scintillator 110-2 is distributed and transmitted to the first optical sensor 130-1 and the second optical sensor 130-2. However, when the scintillation signal S2 is generated from the second scintillator 110-2, a stronger signal than the case where the scintillation signal S2 is generated from the first scintillator 110-1 is generated by the second optical sensor 130. -2) is measured.

That is, when the light guide 140 is inserted, the first scintillator 110-1 and the second scintillator 110-2 are compared with the intensities of the scintillation signal S2 measured by the second optical sensor 130-2. ), the case where the gamma ray (S1) arrives can be distinguished.

Like the third scintillator 110-3 and the fourth scintillator 110-4, as well as the first scintillator 110-1 and the second scintillator 110-2, when the light guide 140 is not included, The scintillation signal S2 is detected only in the two scintillators 130-2.

However, when the light guide 140 is inserted, most of the scintillation signal S2 generated by the fourth scintillator 110-4 is transmitted to the second optical sensor 130-2, and some of the signals are transmitted to the first optical sensor. It can be sent to (130-1).

In addition, when the scintillation signal S2 is generated by the third scintillator 110-3, the scintillation signal S2 is distributed and transmitted to the first optical sensor 130-1 and the second optical sensor 130-2. do. However, a stronger scintillation signal is measured by the first optical sensor 130-1 compared to the case where gamma rays (S1) reach the fourth scintillator 110-4.

Therefore, when the light guide 140 is inserted, the detection depth of gamma rays S1 can be accurately measured even when the number of optical sensors 130 is n and the number of scintillators 110 is 2n. In addition, by using the light guide 140, the detection depth of gamma rays S1 can be accurately measured without increasing the number of optical sensors 130.

Hereinafter, an algorithm for measuring the detection depth of gamma rays will be described with reference to FIG. 8 .

8 is an exemplary diagram for explaining a gamma ray detection position measurement method according to an embodiment.

Referring to FIG. 8 , the incident direction D1 of gamma rays is set to the z-axis, the horizontal direction of the red-side surface of the scintillator is set to the x-axis, and the vertical direction of the red-side surface is set to the y-axis.

In addition, in FIG. 8, the first side (A) and the third side (C) mean sides orthogonal to the x-axis, and the second side (B) and the fourth side (D) are sides orthogonal to the Y-axis. it means. In addition, FIG. 8 is an example of a detector 100 having three scintillators 110 and two optical sensors 130 . Therefore, the optical sensor 130 has a structure in which the first optical sensor 130-1 and the second optical sensor 130-2 are stacked.

The first optical sensor 130-1 includes optical sensors 130-A1, 130-B1, 130-C1, and 130-D1 located in the first row of the first to fourth side surfaces. The second optical sensor 130-2 includes optical sensors 130-A2, 130-B2, 130-C2, and 130-D2 located in the second row of the first to fourth side surfaces.

In order to measure the x-axis coordinate of the gamma ray S1, values measured by the optical sensors 130-A and 130-C disposed on the first and third side surfaces A and C orthogonal to the x-axis are used. . The signal processing unit 200 uses the difference value between the flash signal S2 measured by the optical sensor 130-A disposed on the first side and the optical sensor 130-C disposed on the third side, and uses the x-axis of gamma rays. Derive the detection position.

Specifically, the signal processing unit 200 may derive the x-axis detection position of the gamma ray using Equation 1 below.

[Equation 1]

X-position = (SUM_A1 + SUM_A2 - SUM_C1 - SUM_C2) / (SUM_A1 + SUM_A2 + SUM_C1 + SUM_C2)

Here, X-position means the x-axis detection position of the gamma ray S1, SUM_A1 means the sum of the scintillation signals S2 measured by the optical sensor 130-A1 located in the first row of the first side, , SUM_A2 denotes the sum of the flash signals S2 measured by the photosensors 130-A2 located in the second row of the first side. In addition, SUM_C1 means the sum of the flash signals S2 measured by the optical sensors 130-C1 located in the first row of the third side, and SUM_C2 is the optical sensor 130-C2 located in the second row of the third side. It means the sum of the scintillation signal (S2) measured in C2).

That is, the sum (SUM_A1 + SUM_A2) of the scintillation signal S2 measured by the optical sensor 130-A located on the first side and the scintillation signal S2 measured by the optical sensor 130-C located on the third side The x-axis detection position value of the gamma ray S1 may be measured using a difference value of the sum of (SUM_C1 + SUM_C2).

In addition, in order to measure the y-axis coordinate of the gamma ray S1, the value measured by the optical sensors 130-B and 130-D disposed on the second and fourth sides B and D orthogonal to the y-axis Use The signal processing unit 200 uses the difference value between the flash signal S2 measured by the optical sensor 130-B disposed on the second side and the optical sensor 130-D disposed on the fourth side to determine the y-axis of the gamma ray. Derive the detection position.

Specifically, the signal processing unit 200 may derive the y-axis detection position of the gamma ray using Equation 2 below.

[Equation 2]

Y-position = (SUM_B1 + SUM_B2 - SUM_D1 - SUM_D2) / (SUM_B1 + SUM_B2 + SUM_D1 + SUM_D2)

Here, Y-position means the y-axis detection position of gamma rays S1, and SUM_B1 means the sum of the scintillation signals S2 measured by the optical sensor 130-B1 located in the first row of the second side, , SUM_B2 denotes the sum of the flash signals S2 measured by the photosensors 130-B2 located in the second row of the second side. In addition, SUM_D1 means the sum of the flash signals S2 measured by the optical sensors 130-D1 located in the first row of the fourth side, and SUM_D2 is the optical sensor 130-D2 located in the second row of the fourth side. It means the sum of the scintillation signals (S2) measured in D2).

That is, the sum (SUM_B1 + SUM_B2) of the scintillation signal S2 measured by the optical sensor 130-B located on the second side and the scintillation signal S2 measured by the optical sensor 130-D located on the fourth side The y-axis detection position value of the gamma ray S1 may be measured using the difference value of the sum of (SUM_D1 + SUM_D2).

In addition, the signal processing unit 200 may measure the value of the detection depth (z) of the gamma rays by using the ratio of the detection signal value of the optical sensor 130 to the detection depth of the gamma rays as shown in FIGS. 6 and 7 described above. And, specifically, the z value can be derived using Equation 3 below.

[Equation 3]

Z-position = Log ₁₀ (SUM_A1 + SUM_B1 + SUM_C1 + SUM_D1) / (SUM_A2 + SUM_B2 + SUM_C2 + SUM_D2)

Here, Z-position means the Z-axis detection position (depth) of the gamma ray S1, and SUM_A1 + SUM_B1 + SUM_C1 + SUM_D1 means the sum of the scintillation signals measured by the first optical sensor 130-1, , SUM_A2 + SUM_B2 + SUM_C2 + SUM_D2 denote the sum of the flash signals measured by the second optical sensor 130-2.

However, the reason why the log (Log ₁₀ ) value is taken in Equation 3 is to prevent the position value of the z-axis from becoming excessively large, and therefore, the log value is not necessarily taken in Equation 3.

Therefore, the optical sensors 130-1 and 130-2 arranged in two layers on the four sides produce an electrical signal S3 in response to the light signal S2 measured on the four sides of the scintillator 110. do. The signal processor 200 may derive the detection position and depth coordinates of the gamma ray S1 by substituting the value of the electrical signal S3 into Equations 1 to 3 described above.

Hereinafter, a positron emission tomography method according to an embodiment will be described with reference to FIG. 9 .

9 is a flowchart of a quantum beam emission tomography method according to an embodiment.

Referring to FIG. 9 , in step S100 , gamma rays S1 are incident on the detector 100 included in the positron emission tomography apparatus 1 . In addition, step S100 may include stacking a plurality of flat scintillators 110 in the direction D1 of incident of gamma rays before the gamma rays S1 is incident. In addition, a step of arranging a plurality of optical sensors stacked in the same direction as the stacking direction of the scintillator 130 may be further included on four side surfaces of the flat scintillator 110 .

In step S200, the plurality of scintillators 110 generate a scintillation signal S2 when gamma rays S1 are incident. At this time, the scintillation signal S2 generated by the plurality of scintillators 110 is transmitted to the optical sensor 130 disposed on the side of the scintillator 110 . In addition, since the reflector 120 is disposed between the plurality of scintillators 110, the scintillation signal S2 moves only within the generated scintillator 110.

In step S300, the plurality of photosensors 130 generate an electrical signal S3 in response to the measured flash signal S2. At this time, the optical sensor 130 is composed of a plurality of layers. Accordingly, the ratio of the scintillation signal S2 measured by each of the optical sensors 130-1 and 130-2 varies according to the detection depth of the gamma ray S1.

Therefore, in step S300, the ratio values of electrical signals measured by the first optical sensor 130-1 and the second optical sensor 130-2 vary according to the detection depth of the gamma rays S1. Therefore, the detection position and depth of gamma rays can be measured without increasing the number of optical sensors by using the difference and ratio of the scintillation signal S1 measured by the optical sensor 130 composed of a plurality of layers.

In step S400, the signal processing unit 200 derives the detection position and depth value of the gamma ray S1 using the electrical signal S3 generated by the optical sensor 130. At this time, values measured by the plurality of optical sensors 130 may be substituted into Equations 1 to 3 above to derive the values of the detection positions (x, y) and depth (z) of the gamma rays.

In step S500, a tomographic image of the object to be examined is configured using the derived gamma ray (S1) detection position and depth value.

Hereinafter, simulation results of the positron emission tomography apparatus according to the exemplary embodiment will be described with reference to FIGS. 10 to 13 .

10 and 11 are exemplary diagrams to which Monte Carlo simulation is applied to describe the performance of the positron emission tomography apparatus according to the embodiment.

The Monte Carlo simulation method is a simulation method using a stochastic system under uncertain circumstances. A simulation method that uses random statistical sampling techniques, such as estimation of unknown values. The Monte Carlo simulation method is a simulation method for estimating the error range in the real world by synthesizing the results of repeated simulations obtained by generating random numbers in all stochastic models included in the simulation.

Accordingly, FIGS. 10 and 11 simulate a situation in which gamma ray detection occurs at an arbitrary position inside the scintillator 110 . That is, the (x, y) coordinates are (1,1), (1,15), (1, 30), (15, 1), (15,15), (15,30), (30,1) , (30,15), and (30,30) when gamma ray detection occurs. In addition, it is assumed that gamma ray detection occurs at depths with z coordinate values of 1.0, 2.5, 4.0, 6.0, 7.5, 9.0, 11.0, 12.5, and 14.0.

12 is an example of a gamma ray detection depth distribution graph according to an embodiment.

Referring to FIG. 12, the x-axis represents the gamma-ray measurement position (z-coordinate, mm). Therefore, since the thickness of the scintillator 110 used in the simulation is 5 mm, 0 to 5 (mm) is the lowest layer, the third scintillator 110-3, and 5 to 10 (mm) is the middle layer, the second scintillator 110-2 , 10 to 15 mm may mean the first scintillator 110-1, which is the uppermost layer.

In addition, the y-axis represents the depth measurement value (Z-position) of the gamma ray derived according to Equation 3 described above. Therefore, referring to FIG. 12 , it is possible to check the gamma ray detection depth measurement value according to the location where the gamma ray detection occurred.

Specifically, when gamma ray detection occurs as shown in FIGS. 10 and 11 , the detection depth of gamma rays measured at the third scintillator 110-3 is a value close to -5. More specifically, when the depth of detection of gamma rays is 1.0, 2.5, or 4.0, which is the inside of the third scintillator 110-3, the detection depth of gamma rays measured by the positron emission tomography apparatus 1 according to the embodiment is It has a value of about -5.

In addition, the detection depth of gamma rays measured by the second scintillator 110-2 is a value close to 0. More specifically, when the depth of detection of gamma rays is 6.0, 7.5, or 9.0, which is the inside of the second scintillator 110-2, the detection depth of gamma rays measured by the positron emission tomography apparatus 1 according to the embodiment is has a value of about 0.

In addition, the detection depth of gamma rays measured by the first scintillator 110-1 is a value close to 5. More specifically, when the depth of detection of gamma rays is 11.0, 12.5, or 14.0, which is the inside of the first scintillator 110-1, the detection depth of gamma rays measured by the positron emission tomography apparatus 1 according to the embodiment is It has a value of about 5.

13 is an exemplary view of a 2D plane image for each gamma ray detection depth according to an embodiment.

Referring to FIG. 13 , the detection positions (x, y) of gamma rays measured in each layer of the plurality of scintillators 110 are shown. It is a value obtained by deriving the detection position (x, y) of the gamma ray using Equation 1 and Equation 2 described above and displaying it.

As shown in FIG. 13, the same value is measured for all gamma ray detection positions regardless of the layer of the scintillator 110. in other words. (1,1), (1,15), (1, 30), which are the occurrence positions of gamma ray detection in all of the first scintillator 110-1, the second scintillator 110-2, and the third scintillator 110-3 ), (15, 1), (15, 15), (15, 30), (30, 1), (30, 15), and (30, 30) are measured.

Therefore, the positron emission tomography device 1 according to the embodiment uses the multi-layer comfortable scintillator 110 forming a stacked structure and a plurality of optical sensors 130 disposed on the side of the scintillator 110, thereby providing an optical sensor. It is possible to configure a tomography image by measuring the detection location and depth of gamma rays while reducing the number of lines 130 .

An embodiment of the present invention may be implemented in the form of a recording medium including instructions executable by a computer, such as program modules executed by a computer. Computer readable media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. Also, computer readable media may include computer storage media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data.

Although the methods and systems of the present invention have been described with reference to specific embodiments, some or all of their components or operations may be implemented using a computer system having a general-purpose hardware architecture.

The above description of the present invention is for illustrative purposes, and those skilled in the art can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be construed as being included in the scope of the present invention. do.

1: image tomography device 100: detector
200: signal processing unit 110: scintillator
120: reflector 130: optical sensor
140: light guide

Claims (10)

A plurality of flat scintillators that generate scintillation signals when gamma rays are incident and are stacked in the direction of incidence of the gamma rays;
A plurality of optical sensors that convert the scintillation signal into an electrical signal and are stacked on four sides of the flat scintillator in the same direction as the stacking direction of the flat scintillator, and
A signal processing unit for deriving a 3D value of the gamma-ray detection position having the center point of the flat scintillator as an origin by using the electrical signal, and generating an image using the gamma-ray detection position.
Including,
The plurality of optical sensors are provided with two,
The signal processing unit,
The x-axis detection position of the gamma ray is derived through Equation 1 using the difference between the electrical signal measured by the optical sensor disposed on the first side and the optical sensor disposed on the third side among the four sides of the scintillator,
Deriving the y-axis position of the gamma ray through Equation 2 using the difference between the electrical signals measured by the optical sensor disposed on the second side and the optical sensor disposed on the fourth side of the scintillator,
The z-axis position of the gamma ray is derived through Equation 3 using the ratio of electrical signals measured for each layer of the stacked optical sensors,
The z-axis represents the depth as the direction in which the gamma rays are incident, the x-axis represents the horizontal direction of the red-side surface of the scintillator, and the y-axis represents the vertical direction of the red-side surface of the scintillator,
The first side and the third side are perpendicular to the x-axis, and the second side and the fourth side are sides perpendicular to the y-axis,
[Equation 1]
X-position = (SUM_A1 + SUM_A2 - SUM_C1 - SUM_C2) / (SUM_A1 + SUM_A2 + SUM_C1 + SUM_C2)
The X-position is the x-axis detection position of the gamma ray, SUM_A1 and SUM_A2 are the strengths of electrical signals measured by the optical sensors located on the first and second rows of the first side, and SUM_C1 and SUM_C2 are the third side. Indicates the strength of the electrical signal measured by the optical sensors located in the first row and the second row,
[Equation 2]
Y-position = (SUM_B1 + SUM_B2 - SUM_D1 - SUM_D2) / (SUM_B1 + SUM_B2 + SUM_D1 + SUM_D2)
The Y-position is the y-axis detection position of the gamma ray, SUM_B1 and SUM_B2 are the strengths of electrical signals measured by the optical sensors located in the first and second rows of the second side, SUM_D1 and SUM_D2 are the fourth side Indicates the strength of the electrical signal measured by the optical sensors located in the first row and the second row,
[Equation 3]
Z-position = Log10(SUM_A1 + SUM_B1 + SUM_C1 + SUM_D1) / (SUM_A2 + SUM_B2 + SUM_C2 + SUM_D2)
The Z-position represents a z-axis detection position of gamma rays, positron emission tomography apparatus. delete According to claim 1,
An optical guide disposed between the plurality of flat scintillators and the plurality of optical sensors
Including more,
The light guide diffuses the scintillation signal and transmits it to the photosensor. delete According to claim 1,
The plurality of flat scintillators,
Reflectors are coupled between the plurality of scintillators and between the front and rear surfaces,
The front surface means a surface on which the gamma rays are incident, and the rear surface means a bottom surface facing parallel to the surface on which the gamma rays are incident,
The reflector reflects the scintillation signal, the positron emission tomography apparatus. Generating a scintillation signal when a plurality of planar scintillators stacked in the direction of incidence of gamma rays are incident upon the gamma rays;
Converting the scintillation signal into an electrical signal by a plurality of optical sensors disposed on four sides of the flat scintillator and stacked in the same direction as the stacking direction of the flat scintillator, and
Deriving, by a signal processing unit, a 3D value of the gamma-ray detection position having the center point of the flat scintillator as an origin using the electrical signal, and constructing an image using the gamma-ray detection position
including,
The plurality of optical sensors are provided with two,
The signal processing unit,
The x-axis detection position of the gamma ray is derived through Equation 1 using the difference between the electrical signal measured by the optical sensor disposed on the first side and the optical sensor disposed on the third side among the four sides of the scintillator,
Deriving the y-axis position of the gamma ray through Equation 2 using the difference between the electrical signals measured by the optical sensor disposed on the second side and the optical sensor disposed on the fourth side of the scintillator,
The z-axis position of the gamma ray is derived through Equation 3 using the ratio of electrical signals measured for each layer of the stacked optical sensors,
The z-axis represents the depth as the direction in which the gamma rays are incident, the x-axis represents the horizontal direction of the red-side surface of the scintillator, and the y-axis represents the vertical direction of the red-side surface of the scintillator,
The first side and the third side are perpendicular to the x-axis, and the second side and the fourth side are sides perpendicular to the y-axis,
[Equation 1]
X-position = (SUM_A1 + SUM_A2 - SUM_C1 - SUM_C2) / (SUM_A1 + SUM_A2 + SUM_C1 + SUM_C2)
The X-position is the x-axis detection position of the gamma ray, SUM_A1 and SUM_A2 are the strengths of electrical signals measured by the optical sensors located on the first and second rows of the first side, and SUM_C1 and SUM_C2 are the third side. Indicates the strength of the electrical signal measured by the optical sensors located in the first row and the second row,
[Equation 2]
Y-position = (SUM_B1 + SUM_B2 - SUM_D1 - SUM_D2) / (SUM_B1 + SUM_B2 + SUM_D1 + SUM_D2)
The Y-position is the y-axis detection position of the gamma ray, SUM_B1 and SUM_B2 are the strengths of electrical signals measured by the optical sensors located in the first and second rows of the second side, SUM_D1 and SUM_D2 are the fourth side Indicates the strength of the electrical signal measured by the optical sensors located in the first row and the second row,
[Equation 3]
Z-position = Log10(SUM_A1 + SUM_B1 + SUM_C1 + SUM_D1) / (SUM_A2 + SUM_B2 + SUM_C2 + SUM_D2)
The Z-position represents the z-axis detection position of gamma rays, the positron emission tomography method. delete According to claim 6,
Converting the flash signal into an electrical signal,
Spreading the scintillation signal using a light guide disposed between the plurality of flat scintillators and the plurality of light sensors and transmitting the light to the light sensor.
Further comprising, positron emission tomography method. delete According to claim 6,
Generating the flash signal,
Reflecting the scintillation signal by reflectors coupled between the plurality of flat scintillators and on the front and rear surfaces,
The front surface means a surface on which the gamma rays are incident, and the rear surface means a bottom surface parallel to the surface on which the gamma rays are incident.

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