KR101646620B1 - 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

Disclosed is a method for removing noise from a PET signal in a PET-MRI fusion device without MRI RF shielding that degrades the image quality of the PET-MRI fusion device. The method comprises the steps of receiving PET (Positron Emission Tomography) output signals from a PET-MRI fusing device and measuring the correlation between the PET output signal and the MR RF frequency (Lamor frequency) Removing the noise components to perform analog filtering, and converting the filtered signal into a digital signal through sampling. Molecular images can be obtained without degradation of PET detector in MRI environment.

Description

The present invention relates to a PET-MRI fusion device and a PET-MRI fusion device, and more particularly, to a PET-MRI fusion device and a PET- MRI fusion device using the same}

The present invention relates to a PET signal processing method in a PET-MRI fusion apparatus and a PET system in a PET-MRI fusion apparatus using the same, and more particularly to a noise removal method of a PET signal in a PET- To a PET system in a PET-MRI fusion device.

Medical images used for cell, preclinical, clinical experiment and patient diagnosis are generally classified into largely structured and functional images. The structural image means the structure of the human body and the anatomical image, and the functional image is to directly or indirectly image the functional information on the human body's cognition and sensory functions. Structural and anatomical imaging techniques include Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), and techniques for imaging functional information by observing physiological and biochemical actions of the human body A Positron Emission Tomography (PET) is widely used.

PET is a powerful biological imaging tool that quantifies human function noninvasively. It injects biosensor-labeled biosensor-labeled molecules with radioactive activity into the body, reconstructs the distribution of radiation by tomography Imaging can quantify the physiological and biochemical responses in each organ of the body. Functional / molecular information on the human body structure, such as the brain and organs, provided by PET can be usefully used for disease pathogenesis, diagnosis, and follow-up after chemotherapy.

In addition, PET provides functional information of human tissues with sensitivity at the level of molecules. In order to overcome the limitations inherently in terms of low resolution, PET is used as a convergence device such as a PET-CT fusion device, PET-MRI fusion device, Type PET medical imaging equipment.

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

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

A PET detector 120 is installed between the RF transmit coil 130 and the magnet bore 110. The structure of the PET-MRI fusion device 100 causes interaction between the PET and the MRI, resulting in a number of noises that degrade the quality of the image. Such noise includes high magnetic field, high frequency and low frequency to high power interference due to MRI, magnetism distortion caused by PET, reduction of signal-to-noise ratio, and eddy current. In particular, since the high magnetic field and the high frequency energy of the MRI have the greatest influence on the PET, the RF shield 150 is installed between the RF transmitting coil 130 and the PET detector 120 in order to minimize it. The RF shield 150 may include copper (Cu). The conductive cylinder for the RF shield 150 deteriorates the performance of the RF transmitting and receiving coils 120 and 140 of the MRI and the eddy current is generated in the gradient coil 113 to degrade the resolution of the MRI image. Since the PET detector 120 is provided outside the RF transmission coil 130 from the centrifugal point of the magnet bore 110, the gamma rays emitted from the subject 170 are attenuated by the RF transmission coil 130 Thereby reducing the magnitude of the detection signal. There is a possibility that the temperature of the PET detector 120 is raised, thereby causing a performance degradation. The RF shield 150 installed to minimize the high magnetic field and the high frequency energy of the MRI has a problem that the image quality of the PET-MRI fusion apparatus 100 is degraded.

The present invention is directed to a method for removing noise of a PET signal in a PET-MRI fusion device and a PET signal in a PET-MRI fusion device without MRI RF shielding which degrades image quality of a PET-MRI fusion device To provide a PET system.

According to one aspect of the present invention, a PET (Positron Emission Tomography) output signal is received in a PET-MRI fusion apparatus, and a correlation between a frequency of the PET output signal and a MR RF frequency (Lamor frequency) The present invention also provides a method of removing noise from a PET signal in a PET-MRI fusion apparatus, comprising the steps of removing noise components by a pulse frequency to perform analog filtering, and converting the filtered signal into a digital signal through sampling .

The filtering may remove noise components in the MR RF band (Lamor frequency band) and pass only signals in 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, there is provided a PET-MRI fusion apparatus, comprising: amplifying a PET (Positron Emission Tomography) output signal; converting the amplified PET output signal into a digital signal; And a step of digitally filtering the RF noise using the correlation between the frequency of the RF signal and the MR RF frequency (Lamor frequency).

The digital filtering removes the noise component of the MR RF frequency (Lamor frequency) band and allows only the signal of the frequency band of the PET output signal to pass.

According to another aspect of the present invention, there is provided a PET (Positron Emission Tomography) detector for detecting a gamma ray emitted from an object and converting the converted flash to an electrical signal, an electric signal (PET output signal) And a noise filter unit for filtering the RF noise using a correlation between the frequency of the PET output signal and the MR RF frequency (Lamor frequency). The present invention also provides a PET system in a PET-MRI fusion apparatus.

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

According to another aspect of the present invention, there is provided a PET (Positron Emission Tomography) detector for detecting a gamma ray emitted from an object and converting the converted flash to an electrical signal, an electric signal (PET output signal) A data acquiring unit for converting the PET output signal into a digital signal through sampling and a correlation between the frequency of the PET output signal converted into the digital signal and the MR RF frequency (Lamor frequency) There is provided a PET system in a PET-MRI fusion apparatus including a signal processing unit for filtering noise and performing signal processing for imaging from the filtered signal.

The signal processing unit may remove noise components in the MR RF band (Lamor frequency band) and pass only the signal of the frequency band of the PET output signal.

Noise removal method of PET signal in PET-MRI fusion apparatus using filtering according to this embodiment and PET system in PET-MRI fusion apparatus using this method can acquire molecular image without degradation of PET detector in MRI environment . The performance resistance such as PET refusal time, sensitivity, or image distortion is minimized. The noise removal method of the PET signal in the PET-MRI fusion apparatus using the filtering according to the present embodiment and the PET system in the PET-MRI fusion apparatus using the method are superior to the conventional methods and systems using the RF shield, The factor is removed. The system according to the present embodiment has a simple merit.

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

The present invention is capable of various modifications and various embodiments, and specific embodiments are 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.

The terms including ordinal, such as second, first, etc., may be used to describe various elements, but the elements are not limited to these 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 a first component, and similarly, the first component may also be referred to as a second component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be 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, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations 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 to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings, wherein like or corresponding elements are denoted by the same reference numerals, and redundant description thereof will be omitted.

2 is a view showing a PET-MRI fusion apparatus for explaining the present embodiment.

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

3 is a graph showing a normal PET pulse signal obtained by enlarging the signal of the PET detector.

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

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

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

Referring to FIG. 5, a PET (Positron Emission Tomography) output signal is received from a PET-MRI fusion apparatus, and a correlation between a frequency of the PET output signal and a MR RF frequency (Lamor frequency) The noise component due to the frequency is removed and analog filtering is performed (S410). That is, the MR RF frequency (Lamor frequency) band is removed and filtering is performed to pass the frequency band of the PET output signal. Through this, the RF noise absorbed in the PET signal transmission cable or the signal amplification part is filtered out. For example, if the RF noise in the 300 MHz band affects the PET output signal (the major frequency component in the 100 MHz band) with a frequency of less than 100 MHz, a low pass filter of 100 MHz or less, MHz band-pass filter and a band rejection filter in the 300 MHz band can be designed together to filter RF noise in the 300 MHz band. Here, the analog filter circuit is composed of an RLC filter circuit formed of a passive element or an active filter circuit including an active element. Here, the analog filter circuit can be installed inside the MR bore, inside the MR photographing room, on the wall of the MR photographing room, and the like.

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

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

Referring to FIG. 6, the PET output signal is received and the signal is amplified (S510). Then, the amplified PET output signal is converted into a digital signal (S520). Next, the RF noise is digital filtered using the correlation between the frequency of the PET output signal converted into the digital signal and the MR RF frequency (Lamor frequency) (S530). And performs signal processing for imaging the filtered signal (S540). That is, the digital filtering removes the noise component of the MR RF frequency (Lamor frequency) band and can pass only the signal of the frequency band of the PET output signal. Here, the digital filtering is performed through a logic circuit such as an FPGA or a CPLD. Here, the digital filter is installed inside the MR photographing room or outside the MR photographing room and is driven.

7 is a block diagram showing a PET system in a PET-MRI fusion apparatus according to an example of this embodiment.

7, the PET system 700 in the PET-MRI fusion apparatus includes a PET detector 710, a signal amplification unit 730, a noise filter unit 750, a data acquisition unit 770, and a signal processing unit 790 ).

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

The signal amplifying unit 730 amplifies weak electrical signals input from the PET detector 710 and amplifies the number of signal channels to enable subsequent data acquisition and signal processing. The noise filter unit 750 filters the RF noise using the correlation between the MR RF frequency (Lamor frequency) and the frequency of the PET output signal. That is, the MR RF frequency (Lamor frequency) band is removed and filtering is performed to pass the frequency band of the PET output signal. It will be apparent to those skilled in the art that the noise filter unit 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 elimination filter.

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

FIG. 8 is a circuit diagram showing an example of a noise filter unit according to an embodiment of the present invention, and FIG. 9 is a circuit diagram showing another example of the noise filter unit according to an example of this embodiment. Those skilled in the art will appreciate that such a noise filter portion may be configured in various ways according to the correlation between the MR RF frequency (Lamor frequency) and the frequency of the PET output signal.

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

10, a PET system 800 in a PET-MRI fusion apparatus includes a PET detector 810, a signal amplification unit 830, a data acquisition unit 850, and a signal processing unit 870.

The PET detector 810 includes a scintillation crystal 811 and a photosensor 813 and detects gamma rays emitted from the subject to convert the converted scintillation light into an electrical signal. The signal amplifying unit 830 amplifies weak electrical signals input from the PET detector 810 and amplifies the number of signal channels to enable subsequent data acquisition and signal processing.

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 using the correlation between the MR RF frequency (Lamor frequency) and the frequency of the PET output signal. That is, the MR RF frequency (Lamor frequency) band is removed and filtering is performed to pass the frequency band of the PET output signal. For example, a finite impulse response (FIR) filter and an infinite impulse response (IIR) filter can be used. Further, the signal processing unit 870 performs signal processing for imaging from the filtered signal.

In the present embodiment, various methods for filtering noise from the PET signal in the PET-MRI fusion apparatus may be used.

The noise removal method of the PET signal in the PET-MRI fusion apparatus using filtering according to an example of this embodiment and the noise removal method of the PET signal in the PET-MRI fusion apparatus according to another example of this embodiment can be used together The characteristics of the PET system in the PET-MRI fusion device according to one embodiment of the present invention and the characteristics of the PET system in the PET-MRI fusion device according to another example of this embodiment can simultaneously coexist within the PET-MRI fusion device have.

11 is a graph showing an energy spectrum after removing the noise of the PET signal in the PET-MRI fusion apparatus according to an example of this embodiment. Referring to FIG. 11, it is confirmed that the noise is removed.

As used in this embodiment, the term " portion " refers to a hardware component such as software or an FPGA (field-programmable gate array) or ASIC, and 'part' performs certain roles. However, 'part' 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, by way of example, 'parts' may refer to components such as software components, object-oriented software components, class components and task components, and processes, functions, , Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and components may be further combined with a smaller number of components and components or further components and components. In addition, the components and components may be implemented to play back one or more CPUs in a device or a secure multimedia card.

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

In addition, the program may be recorded in advance in a hard disk or a ROM (Read Only Memory) as a recording medium or may be recorded in a recording medium such as a flexible disk, a CD-ROM (Compact Disc Read Only Memory), an MO Disc, a magnetic disk, a semiconductor memory, or the like, on a temporary basis or permanently. Such a removable recording medium can be provided as package software.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It can be understood that. Therefore, it is intended that the present invention covers all embodiments falling within the scope of the following claims, rather than being limited to the above-described embodiments.

700: PET system 710: PET detector
711: scintillation crystal 713: light sensor
730: Signal amplification unit 750: Noise filter unit
770: Data acquisition unit 790: Signal processing unit

Claims (14)

The PET-MRI fusion apparatus receives a PET (Positron Emission Tomography) output signal without RF shielding, detects a noise frequency by the MR RF frequency from the PET output signal to detect a noise frequency, An analog filtering step of removing a noise component due to the MR RF frequency from the PET output signal in the analog state through a filter circuit configured to cope with;
A digital conversion step of sampling the PET output signal and converting it into a digital signal;
A digital filtering step of removing the noise component from the digital signal; And
And a signal processing step of performing signal processing for imaging from the digital signal. The method for removing noise of a PET signal in a PET-MRI fusion apparatus.
The method according to claim 1,
The digital filtering step
And the noise component is removed from the digital signal through a filter circuit implemented to correspond to the detected noise frequency after the noise frequency is detected from the digital signal by checking the period of the noise component based on the MR RF frequency, Noise removal method of PET signal in PET-MRI fusion device.
The method according to claim 1,
The digital filtering step
Wherein the noise component is removed from the digital signal using the noise frequency detected in the analog filtering step.
A positron emission tomography (PET) detector for detecting a gamma ray emitted from the subject and converting the converted flash to an electrical signal without RF shielding;
A signal amplifier for amplifying a PET output signal input from the PET detector;
A noise frequency is detected by checking the period of the noise component based on the MR RF frequency from the PET output signal, and noise components due to the MR RF frequency are removed from the PET output signal through a filter circuit configured to correspond to the detected noise frequency An analog filter unit;
A data obtaining unit for sampling the PET output signal in the analog state and converting the sampled PET output signal into a digital signal;
A digital filter for removing the noise component from the digital signal; And
And a signal processing unit for performing signal processing for imaging from the digital signal.
5. The method of claim 4,
The digital filter unit
And the noise component is removed from the digital signal through a filter circuit implemented to correspond to the detected noise frequency after the noise frequency is detected from the digital signal by checking the period of the noise component based on the MR RF frequency, PET system in PET-MRI fusion device.
5. The method of claim 4,
The digital filter unit
And the noise component is removed from the digital signal by using the noise frequency detected by the analog filter unit.
5. The method of claim 4,
The analog filter unit
And a filter circuit that is spaced apart from the MR bore by a predetermined distance and installed in the MR imaging room or the MR imaging room wall.


The method according to claim 1,
Wherein the analog filtering step and the digital filtering step comprise:
Wherein the analog and digital filtering are performed using the correlation between the frequency of the PET output signal and the MR RF frequency, respectively.
delete delete 5. The method of claim 4,
Wherein the analog filter unit and the digital filter unit comprise:
Wherein the analog and digital filtering are performed using the correlation between the frequency of the PET output signal and the MR RF frequency, respectively.
delete delete delete

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