KR20120060927A - Positron Emission tomograph and shooting method - Google Patents

Abstract

PURPOSE: A positron emission tomography and a photographing method thereof are provided to improve spatial resolution by employing a Compton camera, parallel to a sectional surface, for patient's summit. CONSTITUTION: A PET(Positron Emission Tomography,1) is in the shape of a horizontally located pipe. A Compton camera(2) is installed on an end of the PET and equipped with an ultralow temperature particle detector. The Compton camera comprises a front scattering part(21) and an absorbing part(22) installed behind the scattering part. The absorbing part comprises an absorber, a SQUID(Superconducting Quantum Interface Device) sensor connecting part which is provided on one side of the absorber and attached with an electric wire connected to a SQUID sensor, and a heat radiating part which is connected through a heat radiating part connector installed under the absorber.

Description

Positron emission tomography apparatus and its shooting method {Positron Emission tomograph and shooting method}

The present invention is a comb equipped with a super conducting Quantum Interface Devices (SQUID) sensor used in a metal magnet calorimeter, which is one of the cryogenic particle detection methods in parallel with a tomography plane in the direction of the patient's parietal tomography in a brain positron emission tomography device. The present invention relates to a positron emission tomography apparatus and a method of photographing the same, in which a turn camera is additionally installed in a positron emission tomography apparatus.

Positron emission tomography (PET), also called positron emission tomography, is a method of nuclear medicine that uses positron emission to inject positron emission after injecting drugs with radioactive isotopes that emit positrons. It is a method of tracking the distribution in the body by using a tomography camera. Receptor images or metabolic images can also be obtained for cancer screening, heart disease, brain disease, and brain function evaluation.

A positron is similar to a electron with a negative charge but with a positive charge, but with a positive charge. These positrons are a type of radiation that is emitted from radioactive isotopes such as C-11, N-13, O-15, and F-18. These elements are the main constituents of living organisms, which can be used to make medicines. . The most commonly used radiopharmaceutical, F-18-FDG, is a glucose-like substance that, when injected, collects much of the body in areas with elevated glucose metabolism, such as cancer.

Recently, positron / computed tomography (PET / CT) scanners combining a positron tomography scanner and a computed tomography (CT) scanner into one have been widely used. Positron / computed tomography is more accurate than conventional positron tomography because it provides anatomical information with the addition of a computed tomography scanner.

Compton Camera is a device that can image the location and shape of gamma source based on the principle of electric collimation that acquires information about the location of gamma source by geometrically interpreting the physical phenomenon called Compton scattering in 1973. It is based on focus and does not require a mechanical focus, and has a multi-racer function that can distinguish the photons' energy and obtain the image of the tracker for each unique energy. In other words, there is no confrontational relationship between image resolution and dose, and thus a good resolution can be obtained with a low dose of radiation.As a result of applying the Compton scattering dynamics, the background coefficient can be removed to a perfect level. Excellent level can be obtained. Therefore, the expectation for the application to real life is increasing.

If the Compton camera is put to practical use in the field of nuclear medical imaging, it is not only easy to find tissues such as cancer but also highly accurate to locate cancer tissues.

Metallic Magnetic Calorimeters (hereinafter referred to as 'MMC') are a type of Cryogenic Particle Detection, which is used to change the magnetization of paramagnetic materials due to temperature changes due to energy absorption. ) Detected by sensor. The very high sensitivity of this sensor ensures very high energy resolution.

Looking at the energy resolution of the MMC, the data published so far have hundreds of eV resolution (about 0.1%) for hundreds of keV photons.

Korean Laid-Open Patent Publication No. 10-2007-0085387 discloses PET by improving the selection of actual (T) extinction events for events involving actual scattering (TS) and random (R) extinction events in PET tomography. New methods of improving the photosensitivity and / or resolution of scanners include the reconstruction of compton scattering interactions at the gamma ray detector to determine the angles of incidence of the gamma rays received at the detector, and the gamma ray polarization and associated with positron disappearance and compton scattering. Electronic recoil data can be used. With the use of the gamma-ray polarization effect, in PET devices, a system of selection of actual co-occurrence events in positron emission tomography is disclosed that enhances the ability to suppress TS and R events while simultaneously selecting data corresponding to T events. ,

Korean Patent Publication No. 10-2009-0109868 includes a plurality of first gamma ray detectors sequentially arranged in a direction of a gamma ray to be measured, and scatters the gamma rays by scattering and scattering the gamma rays. And a scattering unit for measuring energy lost by the gamma ray, and a second gamma ray detector disposed at a position at which the gamma ray scattered from the scattering unit reaches, and an absorbing unit for measuring the arrival position and energy of the scattered gamma ray. Compton camera made and a tomography apparatus using the same is described,

Publication No. 1020090128735 discloses that an ultra-small sample (e.g., biomolecule) is measured by measuring the change in the alternating magnetic permeability by the sample to be measured, using an optical pumping atomic magnetometer having excellent magnetic field sensitivity. The present invention relates to a measuring device capable of detecting the same and a method of using the same, wherein the cell includes an alkali metal atom affected by a magnetic field by a sample; A light source unit 120 for magnetically polarizing an alkali metal atom of the cell 110; An atomic magnetic force means (100) including a bias magnetic field applying unit (130) for applying a bias magnetic field (Bo) for adjusting a measurement resonance frequency of an alkali metal atom; Excitation magnetic field applying means (200) for applying an excitation magnetic field (Bs) composed of a plurality of alternating magnetic fields (Bs1, Bs2) having a predetermined frequency to magnetically excite the sample to the sample; And detection means (300) for detecting a change in magnetic permeability of the sample by measuring a change in magnetic polarization of an alkali metal atom affected by the magnetic field (B) due to the sample magnetically excited by the excitation magnetic field (Bs). Ultra-sensitivity permeability detection device using an atomic magnetometer and a method of using the same are described,

Korean Patent Publication No. 10-0656313 discloses a superpolarized solid material for NMR analysis in which a material is polarized in a ferromagnetic field in a cryostat 2 and then in solution while in the cryostat 2. It can be seen that methods and apparatus for dissolution are disclosed.

Conventional techniques such as the positron emission tomography device and the Compton camera are more than 20 years old, Compton positron emission tomography (Positron Emission Tomography, hereinafter referred to as 'PET'), camera technology. Although it has been developed as a medical technology treatment device using one or two metal magnetic calorimeters (hereinafter, referred to as 'MMC'), the problem of experiencing difficulties during surgery due to the error range cannot be reduced. It is a task to be solved.

In the present invention, to solve the above problems, the prior art is to use a Compton camera as a component of the PET, while obtaining a single image, the present invention is a Compton camera Brain PET Combined with, Principal to correct and correct the image of Brain PET by obtaining its own image with Compton camera,

It can be applied to PET for brain tomography, and it is a method of adding Scatter (scattering part) and absorber (absorbing part) Scatter and absorber in addition to the existing PET. Using a detector consisting of a scatterer and an absorber, the position where the Compton scattering occurred between the radiation and the scatterer, the position where the radiation was absorbed in the absorber and the energy absorbed in the absorber were detected. Compute cameras equipped with super conducting quantum interface devices (SQUID) sensors used in metal magnet calorimeters, one of the methods of accurately calculating the location and cryogenic particle detection, are installed at the end of the ring-shaped PET to reduce the temperature By detecting the change in the magnetization of paramagnetic material with the SQUID (super conducting Quantum Interface Devices) sensor, the sensor's very high sensitivity Positron emission by adding a Compton camera equipped with a super conducting Quantum Interface Devices (SQUID) sensor used in a metal magnet calorimeter, one of the cryogenic particle detection methods with high energy resolution. The present invention provides a tomography apparatus and a method for photographing the same.

In the present invention, a Compton camera is added to the parietal direction of a patient in a tomography using a positron emission tomography apparatus of the brain, and the SQUID (super conducting Quantum Interface Devices) used in a metal magnet calorimeter which is one of cryogenic particle detection methods. ) Compton cameras equipped with sensors can obtain images viewed in the vertical direction of a tomographic plane without additional radiation exposure (in some cases with smaller exposures). This image improves the error correction and resolution of the conventional positron emission tomography device. The super-conducting quantum interface devices (SQUID) sensor is 10 times higher than the conventional direct type radiation detection using high purity germanium or cadmium zinc telide. There is an effect that can be expected to improve the spatial resolution more than twice.

1 is an error phenomenon state diagram of a conventional positron emission tomography apparatus
Figure 2 is a detailed view of the positron emission tomography apparatus of the present invention
Figure 3 is a detailed view of the mechanical details of a typical radiographic image
Figure 4 is a detailed view of the electrical reference in a typical radiographic image
5 is an image acquisition flowchart of the present invention.
6 and 7 is a detailed view of the absorber or scattering portion mounted to the Compton camera of the present invention

In order to achieve the above object, it is not possible to precisely measure the parietal part of the brain due to the structure of the conventional ring-shaped or tubular PET during brain imaging, the cryogenic particles at one end of the parietal part of the brain, namely conventional PET A positron emission tomography device that photographs a Compton camera using MMC equipped with a super conducting Quantum Interface Devices (SQUID) sensor, which is used in one of the detection methods, as a metal magnet calorimeter. It relates to a photographing method.

In the present invention, the Compton camera is added to the head of the patient while the existing equipment is left in the brain PET, and the existing Compton camera can not be installed at all, and the scattering and absorbing parts (or absorption) of the Compton camera By using a super conducting Quantum Interface Devices (SQUID) sensor using a metal magnet calorimeter, which is one of the cryogenic particle detection methods, by detecting the magnetization change of paramagnetic material due to temperature change due to energy absorption, Due to the sensitivity, a Compton camera equipped with a super conducting Quantum Interface Devices (SQUID) sensor, which is used in metal magnet calorimeters, which is one of the cryogenic particle detection methods for accurate positioning with very high energy resolution, A positron emission tomography apparatus for photographing and a photographing method thereof.

The present invention is taken by adding a Compton camera parallel to the tomographic plane in the parietal direction of the patient in PET tomography of the brain, the Compton camera using a cryogenic particle detector, without additional radiation exposure (in some cases with a smaller exposure) ) You can get the image from the vertical direction of the fault plane. Using this image, the error correction and resolution of the conventional PET are improved, and the Compton camera using the cryogenic particle detector has 10 times more energy resolution than the conventional direct radiation detection using high purity germanium or cadmium zinc telide. Therefore, more precise nuclear medical devices have been developed.

Korean Patent Laid-Open Publication No. 10-2007-0085387 and 10-2009-0109868, which are conventional technologies using a PET and a Compton camera, are equipped with a Compton camera instead of a PET radiation detector.

Although the Compton camera is directly used as a radiation detector (ring shape) for producing a response line (LOR) of PET tomography image, in the present invention, a Compton camera parallel to the tomography surface is additionally installed in the conventional PET device, It is a technical configuration to improve the quality of tomography images without radiation exposure.

Efforts to use Compton cameras in nuclear medicine imaging have been underway for about 20 years, but have not yet achieved good results in nuclear medicine.

The conventional PET as described above is a unique method among radiographic apparatuses. When two 511keV gamma rays are generated in opposite directions by approximately 180 degrees and detected by two detectors at the same time, a line connecting the detectors is connected to one reaction line. (LOR) to form an image, no need for mechanical sight like a pinhole camera, etc., in terms of sensitivity, there is no advantage of Compton camera compared to scintillation detectors currently used in commercial PET systems, in particular, a domestic patent The spatial resolution of Compton cameras derived from the inherent energy resolution of the CZT detector, which is disclosed in Korean Patent Publication No. 10-2009-0109868, is similar to or less than that of commercial PET. It is not used.

The cryogenic ion detector includes a metal magnet calorimeter (MMC), and the cryogenic ion detector includes 1. a metal magnet calorimeter 2. a transition edge sensor, 3. an electron probe microanalysis, etc. 5 There are ~ 6 known technologies.

Cryogenic Particle Detector Metal magnet calorimeter
(Metal magnetic microcalorimeters) (Cryogenic Particle Detection)
Transition Edge Sensor
(Transition edge sensor)
Electronic Detection Micro Analysis
Electron probe microanalysis

...

Superconducting Quantum Interference Device (SQUID), which is one of the cryogenic particle detection methods, is a component of the metal magnet calorimeter.The SQUID sensor is a high purity germanium or cadmium It is used for more precise nuclear medicine devices because it has 10 times more energy resolution than the conventional direct method radiation detection using light.

Super conducting Quantum Interface Devices (SQUID) sensors

Absorption of particles (radiation)-> Temperature change-> Magnetization change-> Magnetization Measurement Signals are measured and the energy of the absorbed particles (radiation) is calculated by measuring the very small change in magnetization, and magnetization of the metal Is a very sensitive sensor that measures change,

A very sensitive magnetometer used to measure extremely small magnetic fields and is based on superconducting loops containing Josephson junctions. In addition, noise in the measurement is very low, at a level of 3fT? Hz ^-½ .

For example, a magnet in a typical refrigerator is 0.01 Tesla (10 ^-2 T) and the weak magnetic field in the animal's body ranges from 10 ^-9 T to 10 ^-6 T.

Recently invented SERF atomic magnetometers are more sensitive, but they are larger and more power intensive than SQUID. For decades, SQUID sensors have been the only way to measure very small magnetic fields.

DC SQUID was invented in 1964 by Ford's research experiments with Robert Jacquevik, John Lambie, Arnold Silver and Janes Mercero.

It was after BD Josephson claimed the Josephson effect in 1962 and the Josephson junction was created by John Lowell and Philip Anderson at Bell Labs in 1963. ACQUIRE SQUID was invented by Ford's James Edward Zimmerman and Arnold Silver in 1965.

Because the Manetosensor is very precise, the calculated energy value is also used to have a precise (high resolution) value.

In general, radiation detection is the process of converting radiation into electrical signals. It has the characteristics of energy resolution, spatial resolution, sensitivity, etc. There are direct method and indirect method, and direct method is that the semiconductor detector absorbs radiation (electrical signal), high energy resolution, low sensitivity, and indirect method (using scintillator). Silver scintillator is a method of detecting the radiation by the signal amplification by using the light multiplier (flash generation) photomultiplier, low energy resolution, high sensitivity.

Radiation imaging has a mechanical collimator and an electrical collimator. As shown in FIG. 3, the pinhole camera is a representative example of the angle of incidence of the radiation to the detector to determine the position of the radiation source. Limit. Spatial resolution and sensitivity are in conflict with each other, the electrical reference is Compton camera, as shown in FIG. Using two or more detectors to determine the location of the radiation source by calculating the angle of bending by Compton scattering. It does not limit the angle of incidence of the radiation to the detector, making it more sensitive than mechanical sighting. It can be seen that the spatial resolution is proportional to the energy resolution.

Looking at the error that may occur in PET, as shown in Figure 1, radiation scattering (Scatter): the phenomenon that the direction of change in the reaction (physical) with the human body or air before reaching the detector,

Random coincidence: The phenomenon that radiations from different radiation sources accidentally reach the detector and the error due to the observation position (Parallax error): The radiation generated from the radiation source far from the center of the detector ring is geometrically determined by the detector. Are more likely to be detected by neighboring detectors. As a result, the image is blurred as the image moves away from the center.

The spatial resolution of PET is currently known to be about 2 to 5 mm, and the factors affecting the inherent spatial resolution are the size of the detector crystal (the same principle as the pixel of a digital camera) and the angle logic (Anger logic). Logic for converting into virtual planar coordinates), nonlinearity of photons (gamma emission angle of about 180 to 0.25 degrees), positron response range (average free travel of positrons (F-18: 0.5mm, Rb-82 (4.5mm)) and image restoration algorithms (the size of the detector crystals dominates).

The Compton camera uses a detector consisting of a scatter and an absorber to detect where the Compton scattering occurs between radiation and scatter, where the radiation is absorbed, and where it is absorbed. It is a radiation detector that detects energy and calculates the position of the radiation source.

The Compton effect was discovered by Arthur Compton in 1923 and confirmed by his student the following year. Compton won the Nobel Prize in Physics in 1927 for this discovery. Compton scattering or the Compton effect refers to a phenomenon in which photons of X-rays or gamma rays interact with matter to lose energy and increase wavelength. Inverse Compton scattering also exists, on the other hand, when photons react with matter to obtain energy, reducing the wavelength. Compton scattering is an example of inelastic scattering because the wavelength of the scattered light is different from the wavelength of the incident light. However, the origin of this effect is considered to be the elastic collision between photons and electrons. The amount of wavelength changed by this effect is called the Compton shift. Although there is nuclear Compton scattering, Compton scattering is usually used for reactions involving electrons of atoms.

This effect is important because it shows that light cannot be explained completely by wave phenomena alone. Thomson scattering, a classical theory of electromagnetic scattering of charged particles, cannot explain the change of wavelength toward lower energy. To account for Compton scattering, you must act as if it were composed of particles of light. Compton's experiments showed that light behaves like a flow of particle objects with energy proportional to the frequency.

Spatial Resolution of Compton Cameras

                      (Equation -1)

As in Equation-1, each resolution appears to be proportional to the energy resolution. Compton cameras using detectors, which typically exhibit energy resolution of several keV (about 1%), exhibit angular resolutions of 2 degrees. There is an uncertainty of about 3mm to locate the source 10cm away.

The 3 mm uncertainty can lead to immense errors in the operation of the brain resulting in the loss of the patient's life.

Metallic Magnetic Calorimeters is a Cryogenic Particle Detection instrument that detects the magnetization change of paramagnetic material due to temperature change due to energy absorption with a super conducting Quantum Interface Devices (SQUID) sensor. The very high sensitivity of this sensor ensures very high energy resolution.

Looking at the energy resolution of the MMC, the data published so far have hundreds of eV resolution (about 0.1%) for hundreds of keV photons.

The present invention is as shown in Figure 2, the cryogenic particles in the crown part of the brain that is not able to precisely measure the crown part of the brain in the structure of the conventional ring-shaped or tubular PET when taking the brain cryogenic particles at one end of the conventional PET The Compton camera using MMC that can measure precisely to the crown part by installing a Compton camera using MMC

Simply calculating using Equation-1, the Compton camera using the MMC has an angular resolution of about 0.2 degrees, which results in a 0.3 mm uncertainty of the position of the source 10 cm away.

If the SQUID sensor of the computer camera of the present invention to explain in detail the principle of correcting the PET (1) image,

Extinction radiation (511keV gamma rays) generated when the positron emitted from the radioisotope injected into the brain is combined with the neighboring electron and extinguishes is detected using a Compton camera installed in the crown. Using the Compton camera proposed in the present invention can find the position where the extinction radiation occurred in the error range of about 0.3mm. Using this, the distribution of radiation sources injected into the brain can be known very accurately. Sensitivity is significantly lower than the detector used in conventional PET, so it is difficult to make a diagnostic image by itself, but the exact location information can be used to correct errors in the existing PET image. There may be several algorithms for error correction.

1. Simple comparison: A simple comparison between Compton camera images and PET images to emphasize common points.

2. Distance inverse factor calculation: A method of multiplying the pixel value of the PET image coordinates by a factor inversely proportional to the distance from the position of the radiation source detected in the Compton camera image.

Based on these two algorithms, we can design an algorithm suitable for error correction according to the medical application.

Fig. 7 is a three-dimensional drawing of one cell of Fig. 6, and the entirety of Fig. 6 may be an absorbing part 22 or a scattering part 21.

Example

When the Compton camera 2 photographs the inside of the tubular PET (1) installed at one rear end, two images respectively captured by the PET (1) and the Compton camera (2) are obtained.

The captured image of the Compton camera 2 is a heat discharge port 55 is connected to the heat dissipation portion 54 by the heat dissipation portion 54 under the absorption portion 22 by the absorbed radiation signal Through the exhaust,

When a radiation signal is obtained from the absorber 53 of the absorber 22, a part of the absorber 53 sends a signal to the SQUID sensor through the SQUID sensor connector 52 to obtain an image.

The captured image of PET (1) is the captured image of Compton camera (2) by simply comparing the image of Compton camera and the image of PET to emphasize the common part, or comp to the pixel value of PET image coordinates The final image was corrected by using a method of multiplying a factor inversely proportional to the distance from the position of the radiation source detected in the turn camera image, so that the final corrected image of the PET 1 was displayed.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram showing a state of error of a conventional positron emission tomography apparatus, FIG. 2 is a detailed view of a positron emission tomography apparatus of the present invention, FIG. 3 is a mechanical detail view of a general radiographic image, and FIG. Figure 5 is a detailed view of the image acquisition flow chart of the present invention, Figures 6 and 7 shows a detailed view of the absorber or scattering portion mounted to the Compton camera of the present invention, PET (1), Compton camera ( 2), scattering unit 21, absorbing unit 22, super conducting Quantum Interface Devices (SQUID) sensor 51, SQUID sensor connection unit 52, absorber 53, heat discharge connector 54, heat outlet ( 55).

Looking at the structure of the positron emission tomography apparatus of the present invention, as shown in Figures 2, 6 and 7, the tubular PET (1), and the Compton camera installed on one end of the PET ( 2) and a cryogenic particle detector mounted on the compton camera 2, and the cryogenic particle detector mounted on the compton camera 2 is a super conducting quantum interface device (SQUID) used in a metal magnet calorimeter. Sensor 51,

It can be seen that consists of.

As shown in FIG. 2, the compton camera 2 includes a scattering unit 21 disposed at a front side and an absorbing unit 22 disposed at a rear side of the scattering unit 21.

As shown in FIGS. 6 and 7, the absorber part 22 includes an absorber 53 and a SQUID sensor connection part 52 protruding from an upper side of the absorber 53 and connected to a SQUID sensor. And, it can be seen that the heat discharge port 55 is connected by the heat discharge connection portion 54 provided in the lower portion of the absorber (53).

PET (1), Compton camera (2), scattering unit (21), absorbing unit (22), super conducting Quantum Interface Devices (SQUID) sensor 51, SQUID sensor connection unit 52, absorber 53, heat Exhaust connector (54), heat outlet (55),

Claims (4)

In a positron emission tomography apparatus,
PET (1) having a horizontally positioned tube, Compton camera (2) installed on the front so that the P-ring or tube is blocked at one end of the PET (1) located horizontally, and the Compton camera A positron emission tomography apparatus, characterized in that it is composed of a cryogenic particle detector attached to (2).
The method according to claim 1, wherein the compton camera 2 is composed of a scattering portion 21 provided on the front, and the absorbing portion 22 provided on the back of the scattering portion 21,
The absorbent part 22 is installed at the lower part of the absorber 53, the SQUID sensor connecting portion 52 is attached to the upper part of the absorber 53 protruding to connect to the SQUID sensor, Positron emission tomography apparatus, characterized in that consisting of a heat discharge port 55 is connected by the heat discharge connection portion (54). The positron emission tomography apparatus according to claim 1, wherein the cryogenic particle detector mounted on the compton camera is a super conducting quantum interface devices (SQUID) sensor used in a metal magnet calorimeter.
In the positron emission tomography method,
When the Compton camera 2 photographs the inside of the tubular PET (1) installed at one rear end, two images respectively captured by the PET (1) and the Compton camera (2) are obtained.

The captured image of the Compton camera 2 is a heat discharge port 55 is connected to the heat dissipation portion 54 by the heat dissipation portion 54 under the absorption portion 22 by the absorbed radiation signal Through the exhaust,

When a radiation signal is obtained from the absorber 53 of the absorber 22, a part of the absorber 53 sends a signal to the SQUID sensor through the SQUID sensor connector 52 to obtain an image.

The captured image of PET (1) is taken by Compton Camera (2) The captured image of PET (1) is taken by Compton Camera (2) The final image is corrected by using a method of emphasizing the common part by simple comparison, or multiplying the pixel value of the PET image coordinates by a factor that is inversely proportional to the distance from the position of the radiation source detected in the Compton camera image. Positron emission tomography method, characterized in that photographed to show the image of the PET (1).

Images