KR20120057601A - Method for removing noise of PET signal using filtering in PET-MRI fusion device and PET system in PET-MRI fusion device using the same - Google Patents

Abstract

PURPOSE: A method for eliminating noise of PED signal and a PED system using the same are provided to obtain a molecular image without performance degradation of a PET detector by omitting radio frequency shielded material. CONSTITUTION: A signal amplification unit(730) amplifies a PET(Positron Emission Tomography) output signal inputted from a PET detector. An analog filter unit eliminates a noise component by MR RF(Lamor frequency) frequency from the PET output signal. A data acquisition unit(770) changes the PET output signal of an analog state into a digital signal. A digital filter unit eliminates the noise component from the digital signal through a filter circuit. A signal processing unit(790) executes signal processing for visualization from the digital signal.

Description

Method for removing noise of PET signal from PET-MRI fusion device using filtering and PET system using PET-MRR fusion device using filtering in PET-MRI fusion device and PET system in PET- MRI fusion device using the same}

The present invention relates to a PET signal processing method in the PET-MRI fusion device and a PET system in the PET-MRI fusion device using the same, in particular, a method for removing the noise of the PET signal in the PET-MRI fusion device using filtering and The present invention relates to a PET system in a PET-MRI fusion device.

Medical images used for the diagnosis of cells, preclinical, clinical trials, and patients are generally classified into structural and functional images. The structural image refers to the structure and anatomical image of the human body, and the functional image is to image functional information about the human body's cognition, sensory function, etc. directly or indirectly. Structural and anatomical imaging techniques include Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), and technology to visualize functional information by observing the physiological and biochemical effects of the human body. Positron emission tomography (PET) is widely used.

PET is a powerful biological imaging tool that quantifies non-invasive human function, injects biological probe molecules labeled with positron emitting isotopes with radioactive activity into the body, and then reconstructs the distribution of radioactivity by tomography. Imaging can quantify the physiological and biochemical responses within each organ of the human body. Functional / molecular information on the structure of the human body, such as the brain and organs, provided by PET can be usefully used for studying the pathogenesis of diseases, determining the prognosis of the disease, and monitoring the progress after chemotherapy.

In addition, PET provides functional information of human tissues with molecular level sensitivity, while fusion such as PET-CT fusion device, PET-MRI fusion device, and PET-optical imaging device to overcome the limitations inherently low resolution. The concept is developing as a type PET medical imaging equipment.

1 is a cross-sectional view of a conventional PET-MRI fusion device.

Referring to FIG. 1, the PET-MRI fusion device includes a magnet bore 110, a PET detector 120, an RF transmitting coil 130, an RF receiving coil 140, and an RF shield 150. Bed 160.

The PET detector 120 is installed between the RF transmitting coil 130 and the magnet bore 110. The structure of the PET-MRI fusion device 100 causes an interaction between the PET and the MRI, thereby generating various noises that degrade the quality of the image. Such noises include high magnetic field, high frequency and low frequency interference caused by MRI, magnetic field distortion caused by PET, reduction of signal-to-noise ratio, and eddy current. In particular, since the high magnetic field and high frequency energy of the MRI has the greatest impact on the PET, an RF shield 150 is installed between the RF transmitting coil 130 and the PET detector 120 to minimize this. This RF shield 150 may comprise copper (Cu). The conductive cylinder for the RF shield 150 deteriorates the performance of the RF transmission / reception coils 120 and 140 of the MRI, and generates a eddy current in the gradient coil 113 to reduce the resolution of the MRI image. In addition, since the PET detector 120 is provided outside the RF transmitting coil 130 from the centrifugal of the magnet bore 110, the gamma rays emitted from the test object 170 are attenuated by the RF transmitting coil 130. Scattering reduces the magnitude of the detection signal. There is a possibility that the temperature of the PET detector 120 is raised, thereby degrading the performance. The RF shield 150 installed to minimize the high magnetic field and high frequency energy of the MRI has a problem of degrading the image quality of the PET-MRI fusion device 100.

The technical problem to be achieved by the present invention is to remove the noise of the PET signal in the PET-MRI fusion device and to remove the noise of the PET signal in the PET-MRI fusion device without the MRI RF shield that reduces the image quality of the PET-MRI fusion device To provide a PET system.

According to an aspect of the present invention, a PET-MRI fusion device receives a PET (Positron Emission Tomography) output signal and uses the correlation between the frequency of the PET output signal and the MR RF frequency (Lamor frequency) from the PET output signal to RF. It provides a method of removing noise of a PET signal in a PET-MRI fusion device, which comprises the steps of analog filtering by removing noise components by pulse frequency, and converting the filtered signal into a digital signal through sampling. .

The filtering may remove noise components of the MR RF frequency band and pass only signals of the frequency band of the PET output signal.

The method may further include receiving the digital signal and performing signal processing for imaging.

According to another aspect of the present invention, amplifying a PET (Positron Emission Tomography) output signal in a PET-MRI fusion device, converting the amplified PET output signal into a digital signal, and the PET output signal converted into the digital signal The present invention provides a noise reduction method of a PET signal in a PET-MRI fusion device, including digitally filtering RF noise by using a correlation between a frequency and an MR RF frequency.

The digital filtering may remove noise components of the MR RF frequency band and pass only signals of the frequency band of the PET output signal.

According to another aspect of the present invention, a PET (Positron Emission Tomography) detector which detects gamma rays emitted from an object and converts the converted flashes into an electrical signal, and an electrical signal (PET output signal) input from the PET detector. The present invention provides a PET system in a PET-MRI fusion device including a signal amplifier for amplifying and a noise filter for filtering RF noise by using a correlation between the frequency of the PET output signal and a MR RF frequency.

The filtering may remove noise components of the MR RF frequency band and pass only signals of the frequency band of the PET output signal.

According to another aspect of the present invention, a PET (Positron Emission Tomography) detector which detects gamma rays emitted from an object and converts the converted flashes into an electrical signal, and an electrical signal (PET output signal) input from the PET detector. RF by using a correlation between a signal amplifier for amplifying, a data acquisition unit for converting the PET output signal into a digital signal through sampling, and a frequency of the PET output signal converted into the digital signal and a MR RF frequency The present invention provides a PET system in a PET-MRI fusion device including a signal processor that filters noise and performs signal processing for imaging from the filtered signal.

The signal processor may remove noise components of the MR RF frequency band and pass only a signal of a frequency band of the PET output signal.

The noise reduction method of the PET signal in the PET-MRI fusion device using filtering according to the present embodiment and the PET system in the PET-MRI fusion device using the same can obtain molecular images without degrading the performance of the PET detector in the MRI environment. . Performance resistance such as PET dead time, sensitivity or image distortion is minimized. The noise reduction method of the PET signal in the PET-MRI fusion device using the filtering according to the present embodiment and the PET system in the PET-MRI fusion device using the same are more susceptible to mutual interference than the conventional method and system using the RF shield. The factor is removed. The system according to the present embodiment has the advantage that the equipment is simple.

1 is a cross-sectional view of a conventional PET-MRI fusion device.
Figure 2 is a view showing a PET-MRI fusion device to explain this embodiment.
3 is a graph showing a normal PET pulse signal in which the signal of the PET detector is enlarged.
4 is a graph showing a PET pulse signal affected by noise by the high magnetic field and high frequency energy of the MRI in the PET-MRI fusion device.
5 is a flowchart illustrating a method of removing noise of a PET signal in a PET-MRI fusion device using filtering according to an embodiment of the present embodiment.
6 is a flowchart illustrating a method of removing noise of a PET signal in a PET-MRI fusion device using filtering according to another embodiment of the present embodiment.
7 is a block diagram illustrating a PET system in a PET-MRI fusion device according to an embodiment of the present embodiment.
8 is a circuit diagram illustrating an example of a noise filter unit according to an example of this embodiment, and FIG. 9 is a circuit diagram illustrating another example of a noise filter unit according to an example of this embodiment.
10 is a block diagram showing a PET system in a PET-MRI fusion device according to another example of this embodiment.
11 is a graph showing an energy spectrum after removing noise of a PET signal in a PET-MRI fusion device according to an embodiment of the present embodiment.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated and described in the drawings. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Terms including ordinal numbers, such as second and first, may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the second component may be referred to as the first component, and similarly, the first component may also be referred to as the second component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings, and the same or corresponding components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted.

Figure 2 is a view showing a PET-MRI fusion device to explain this embodiment.

Referring to FIG. 2, this embodiment removes noise of a PET signal in a PET system including a PET detector 120 and a PET image processor 210 in a PET-MRI fusion device. The MRI operates independently of this embodiment.

3 is a graph showing a normal PET pulse signal in which the signal of the PET detector is enlarged.

4 is a graph showing a PET pulse signal affected by noise by the high magnetic field and high frequency energy of the MRI in the PET-MRI fusion device. Referring to FIG. 4, it may be confirmed that the signal is not clear due to noise.

The noise reduction method of the PET signal in the PET-MRI fusion device according to the present embodiment removes the noise of the PET signal by filtering the MR RF noise using a correlation between the MR RF frequency and the frequency of the PET output signal.

5 is a flowchart illustrating a method of removing noise of a PET signal in a PET-MRI fusion device using filtering according to an embodiment of the present embodiment.

Referring to FIG. 5, an RF pulse is received from the PET output signal using a correlation between a frequency of the PET output signal and a MR RF frequency by receiving a Positron Emission Tomography (PET) output signal from a PET-MRI fusion device. Analog filtering is performed by removing the noise component due to the frequency (S410). That is, filtering is performed to remove the MR RF frequency band and pass the frequency band of the PET output signal. This removes the RF noise absorbed by the PET signal transmission cable or signal amplifier through filtering. For example, if RF noise in the 300 MHz band affects a PET output signal with a frequency below 100 MHz (the 100 MHz band is the main frequency component), a low pass filter below 100 MHz, 100 A 300 MHz band pass filter and a 300 MHz band rejection filter can be designed together to filter out RF noise in the 300 MHz band. Here, the analog filter circuit is composed of an RLC filter circuit composed of passive elements or an active filter circuit including active elements. Here, the analog filter circuit may be installed and driven inside the MR bore, inside the MR imaging chamber, on the MR imaging chamber wall, and the like.

Then, the filtered signal is received and converted into a digital signal through sampling (S420). Signal processing for imaging (S430).

6 is a flowchart illustrating a method of removing noise of a PET signal in a PET-MRI fusion device using filtering according to another embodiment of the present embodiment.

Referring to FIG. 6, the PET output signal is input and amplified (S510). Then, the amplified PET output signal is converted into a digital signal (S520). Next, the RF noise is digitally filtered using the correlation between the frequency of the PET output signal converted into the digital signal and the MR RF frequency (Smor frequency) (S530). Signal processing for imaging the filtered signal (S540). That is, the digital filtering may remove noise components in the MR RF frequency band and pass only signals in the frequency band of the PET output signal. Here, digital filtering is performed through logic circuits such as FPGA and CPLD. Here, the digital filter is installed and driven inside the MR imaging room or outside the MR imaging room.

7 is a block diagram illustrating a PET system in a PET-MRI fusion device according to an embodiment of the present embodiment.

Referring to FIG. 7, the PET system 700 in the PET-MRI fusion device includes a PET detector 710, a signal amplifier 730, a noise filter 750, a data acquisition unit 770, and a signal processor 790. ).

The PET detector 710 includes a scintillation crystal 711 and an optical sensor 713, and the scintillation crystal 711 detects gamma rays emitted from the subject to convert the scintillation. For example, the scintillation crystal 711 detects 511 keV gamma rays which are generated in opposite directions by a bi-decay phenomenon. The scintillation crystals 711 may include Bismuth Germanate (BGO), Lutetium Oxyorthosilicate (LSO), Lutetium Yttrium Oxyorthosilicate (LYSO), Lutetium Aluminum Perovskite (LUAP), Lutetium Yttrium Aluminum Perovskite (LUYAP), LaBr3 (Lanthanum Bromide) Lutetium Iodide), GSO (Gadolinium oxyorthosilicate), LGSO (lutetium gadolinium oxyorthosilicate), LuAG (Lutetium aluminum garnet) can be made of one. The photosensor 713 converts the converted flash into an electrical signal. Here, the optical sensor 713 may include a Photo-Multiplier Tube (PMT), a Positive-Intrinsic-Negative Diode (PID), a Cadmium Telluride (CdTe), a Cadmium Zinc Telluride (CZT), an Avalanche Photo Diode (APD), or a Geger mode (GAPD). Avalanche Photo Diode) and the like can be used.

The signal amplifier 730 amplifies the weak electric signal input from the PET detector 710 and amplifies the number of signal channels to enable subsequent data acquisition and signal processing. The noise filter 750 filters the RF noise by using a correlation between the MR RF frequency and the frequency of the PET output signal. That is, filtering is performed to remove the MR RF frequency band and pass the frequency band of the PET output signal. It will be apparent to those skilled in the art that the noise filter 750 may be configured by combining various filters such as a high pass filter, a low pass filter, a band pass filter, and a band cancellation filter.

The data acquisition unit 770 converts an electrical signal filtered with RF noise into a digital signal (hereinafter referred to as a PET signal) through sampling to enable signal processing and image reconstruction. The signal processor 790 performs signal processing for imaging from the obtained PET signal.

8 is a circuit diagram illustrating an example of a noise filter unit according to an example of this embodiment, and FIG. 9 is a circuit diagram illustrating another example of a noise filter unit according to an example of this embodiment. It will be apparent to those skilled in the art that the noise filter unit may be configured in various ways depending on the correlation between the MR RF frequency and the frequency of the PET output signal.

10 is a block diagram showing a PET system in a PET-MRI fusion device according to another example of this embodiment.

Referring to FIG. 10, the PET system 800 in the PET-MRI fusion device includes a PET detector 810, a signal amplifier 830, a data acquisition unit 850, and a signal processor 870.

The PET detector 810 includes a scintillation crystal 811 and an optical sensor 813, and detects gamma rays emitted from the subject to convert the converted scintillation into an electrical signal. The signal amplifier 830 amplifies the weak electric signal input from the PET detector 810 and amplifies the number of signal channels to enable data acquisition and signal processing later.

The data acquisition unit 850 converts an analog signal, which is an electrical signal, into a digital signal through sampling. The signal processor 870 filters the RF noise by using a correlation between the MR RF frequency and the frequency of the PET output signal. That is, filtering is performed to remove the MR RF frequency band and pass the frequency band of the PET output signal. For example, finite impulse response (FIR) filters, infinite impulse response (IIR) filters, and the like may be used. In addition, the signal processor 870 performs signal processing for imaging from the filtered signal.

In the present embodiment, various methods of removing noise through filtering from a PET signal in a PET-MRI fusion device may be used.

The noise reduction method of the PET signal in the PET-MRI fusion device using the filtering according to the embodiment of the present embodiment and the noise reduction method of the PET signal in the PET-MRI fusion device according to another embodiment of the present embodiment can be used at the same time In addition, the characteristics of the PET system in the PET-MRI fusion device according to an example of this embodiment and the characteristics of the PET system in the PET-MRI fusion device according to another example of this embodiment may coexist in the PET-MRI fusion device at the same time. have.

11 is a graph showing an energy spectrum after removing noise of a PET signal in a PET-MRI fusion device according to an embodiment of the present embodiment. Referring to Figure 11, it can be seen that the noise is removed.

The term '~ part' used in the present embodiment refers to software or a hardware component such as a field-programmable gate array (FPGA) or an ASIC, and '~ part' performs certain roles. However, '~' is not meant to be limited to software or hardware. &Quot; to " may be configured to reside on an addressable storage medium and may be configured to play one or more processors. Thus, as an example, '~' means components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, procedures, and the like. Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functionality provided within the components and the 'parts' may be combined into a smaller number of components and the 'parts' or further separated into additional components and the 'parts'. In addition, the components and '~' may be implemented to play one or more CPUs in the device or secure multimedia card.

All of the above functions may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), or the like according to software or program code coded to perform the function. The design, development and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

51 In addition, the program can be recorded in advance on a hard disk or ROM (Read Only Memory) as a recording medium, or a flexible disk, compact disc read only memory (CD-ROM), magneto optical (MO) disk, or DVD (Digital Versatile). It can be stored temporarily or permanently in a removable recording medium, such as a disc), a magnetic disk, and a semiconductor memory. Such a removable recording medium can be provided as package software.

Although the present invention has been described above with reference to the embodiments, a person skilled in the art may variously modify and change the present invention without departing from the spirit and scope of the present invention. I can understand that. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

700: PET system 710: PET detector
711: scintillation crystal 713: light sensor
730: signal amplifier 750: noise filter
770: data acquisition unit 790: signal processing unit

Claims (7)

A PET-MRI fusion device receives a PET (Positron Emission Tomography) output signal and checks a period of a noise component by MR RF frequency from the PET output signal to detect a noise frequency, and then corresponds to the detected noise frequency. An analog filtering step of removing a noise component due to an MR RF frequency from the PET output signal in an analog state through a filter circuit;
A digital conversion step of sampling the PET output signal and converting the PET output signal into a digital signal;
A digital filtering step of removing the noise component from the digital signal; And
A signal processing step of performing signal processing for imaging from the digital signal;
Noise reduction method of the PET signal in the PET-MRI fusion device comprising a.
The method of claim 1,
The digital filtering step
After detecting the noise frequency by checking the period of the noise component by the MR RF frequency from the digital signal, the noise component is removed from the digital signal through a filter circuit implemented to correspond to the detected noise frequency Noise Reduction Method of PET Signal in PET-MRI Fusion Device.
The method of claim 1,
The digital filtering step
The noise reduction method of the PET signal in the PET-MRI fusion device, characterized in that for removing the noise component from the digital signal by using the noise frequency detected in the analog filtering step.
A positron emission tomography (PET) detector which detects gamma rays emitted from the subject and converts the converted flashes into electrical signals;
A signal amplifier for amplifying the PET output signal inputted from the PET detector;
After detecting the noise frequency by checking the period of the noise component by the MR RF frequency from the PET output signal, the noise component by the MR RF frequency is removed from the PET output signal through a filter circuit configured to correspond to the detected noise frequency. An analog filter unit;
A data acquisition unit for sampling the PET output signal in an analog state and converting the PET output signal into a digital signal;
A digital filter unit to remove the noise component from the digital signal; And
A signal processor which performs signal processing for imaging from the digital signal;
PET system in PET-MRI fusion device comprising a.
The method of claim 4, wherein
The digital filter unit
After detecting the noise frequency by checking the period of the noise component by the MR RF frequency from the digital signal, and removing the noise component from the digital signal through a filter circuit implemented to correspond to the detected noise frequency PET system in PET-MRI fusion device.
The method of claim 4, wherein
The digital filter unit
The PET system of the PET-MRI fusion device, characterized in that for removing the noise component from the digital signal using the noise frequency detected by the analog filter.
The method of claim 4, wherein
The analog filter unit
The PET system in the PET-MRI fusion device, characterized in that it comprises a filter circuit which is spaced apart from the MR bore a predetermined distance, inside the MR imaging room or on the MR imaging room wall.

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