KR20190038967A - Method for correction pile up signal in medical imaging device using multi-threshold voltage and medical imaging device thereof - Google Patents

Abstract

The present invention relates to a signal processing using multiple threshold voltages comprising: a signal detector including a plurality of optical sensors to convert a flashing light signal outputted by a scintillator unit for converting radiation into a flashing light signal into an electric signal or a plurality of semiconductor sensors to convert radiation into an electric signal; an analog signal processing unit to receive an electric signal for each channel outputted by the signal detector and a plurality of preset different threshold voltages to compare the electrical signal and signals in accordance with the plurality of different threshold voltages to generate a plurality of comparison signals; and a digital signal processing unit to receive the comparison signals outputted by the analog signal processing unit, and respond to the received comparison signals to acquire reaction energy level information, reaction time information, and reaction position information of radiation. The digital signal processing unit determines whether signals are signal-redundant with redundant signals depending on whether at least one comparison signal has two or more pulses, and reconstructs reaction energy level information and reaction time information corresponding to a plurality of signals constituting signal redundancy based on a pulse width for each threshold voltage of the signal redundancy.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of compensating for signal duplication in a medical imaging apparatus using multiple threshold voltages,

The present invention relates to a method for correcting signal duplication in a medical imaging apparatus using a multi-threshold voltage and a medical imaging apparatus using the same, A method for detecting and correcting a signal, and a signal processing system for the medical imaging apparatus.

In the case of various types of medical imaging devices, which are widely used in recent years, the radiation emitted from the radiopharmaceutical drug injected into the object or the radiation transmitted through the object is detected, Signal. At this time, a multi-channel radiation detector is used to provide accurate anatomical / physiological image information. For example, radiographic imaging devices such as Positron Emission Tomography (PET) and Gamma camera use optical sensors having a large number of channels per unit area in order to improve sensitivity . Due to this increase in the number of channels, the signal processing burden is increasing in acquiring and processing data.

In order to solve this problem, radiation imaging devices use a channel reduction circuit such as an anger circuit to reduce the number of channels, but as the radiation count increases, Pile up is occurring. Signal duplication causes degradation of the performance of the radiation detector and reduction of the radiation count rate and SNR (Signal to Noise Ratio) of the whole system. Therefore, it is necessary to detect and correct the signal duplication phenomenon efficiently while reducing the number of channels.

Korean Patent No. 10-1686306 (Title of the Invention: Method and Structure for Preventing Loss of Information Due to Signal Overlap of Radiation Coefficient Sensor Signal Processor and Eliminating Energy Distortion)

The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a method and apparatus for applying a plurality of threshold voltages having different values to a comparator without using an ADC or a TDC in a medical imaging apparatus, It is an object of the present invention to provide a signal processing system of a medical imaging apparatus capable of detecting and restoring information on radiation through a radio signal and detecting and restoring signal overlapping in real time. It is to be understood, however, that the technical scope of the present invention is not limited to the above-described technical problems, and other technical problems may exist.

As a technical means for achieving the above technical object, a first aspect of the present invention provides a method for converting a scintillation signal output from a scintillator unit into a scintillation signal, comprising the steps of: A signal detector including a semiconductor sensor; An analog signal processor for receiving an electrical signal for each channel output from the signal detector and a plurality of predetermined threshold voltages and generating a plurality of comparison signals by comparing electrical signals and signals corresponding to a plurality of different threshold voltages, ; And a digital signal processor for receiving the comparison signal output from the analog signal processor and acquiring reaction energy magnitude information, reaction time information, and reaction position information of the radiation in response to the input comparison signal. At this time, the digital signal processor determines whether the signals are pile-up depending on whether at least one comparison signal has two or more pulses, and determines whether the signals are overlapped or not based on the pulse widths of the signal overlaps And restores reaction energy magnitude information and reaction time information corresponding to each of the plurality of constituent signals.

According to a second aspect of the present invention, there is provided a method of detecting a radiation signal, comprising: generating a plurality of comparison signals according to a result of detecting a radiation signal and comparing the detected signal with a plurality of different threshold voltages; Determining whether the radiation signals are signal redundant depending on whether at least one of the plurality of comparison signals has two or more pulses; Dividing the signal redundancy into a plurality of signals according to the number of pulses contained in at least one comparison signal; And restoring reaction energy information and reaction time information of the radiation corresponding to each of the plurality of signals based on the pulse width of each of the plurality of signals by the threshold voltage.

A third aspect of the present invention provides a computer-readable recording medium having recorded thereon a program for executing the method of the second aspect by a computer.

According to the present invention, by separating the output signal of the signal detector through a plurality of different threshold voltages applied to the comparator, information such as energy, time, position, etc. for the radiation detected using the ADC or TDC It is possible to prevent the size and cost of the signal processing system from increasing,

Further, the present invention separates the output signal of the signal detector through different threshold voltages applied to the comparator, thereby recognizing the signal overlap in real time and restoring the signal redundancy by using a digital signal processor (DSP) The performance of the system can be improved.

1 is a conceptual diagram of a signal processing system of a medical imaging apparatus using a multi-mandatory voltage according to an embodiment of the present invention.
2 is an example of an input / output signal of a comparator according to an embodiment of the present invention.
FIG. 3 illustrates an example in which signal redundancy is input to the FPGA according to an embodiment of the present invention.
4 is a flowchart illustrating a restoration process performed by the digital signal processing unit according to an exemplary embodiment of the present invention.
5 is a diagram for explaining pulse widths according to signal duplication and threshold voltage according to an embodiment of the present invention.
FIG. 6A shows an example in which the pulse width for each threshold voltage is restored for the first signal of FIG.
And FIG. 6B shows an example of restoring the pulse width for each threshold voltage with respect to the second signal of FIG.
FIG. 7 is an example showing the superposition energy in the signal overlap in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is " on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as "including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. The terms "about "," substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure. The word " step (or step) "or" step "used to the extent that it is used throughout the specification does not mean" step for.

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

1 is a conceptual diagram of a signal processing system of a medical imaging apparatus using a multi-mandatory voltage according to an embodiment of the present invention. Here, the medical imaging device may be a computerized tomography (CT), a single photon emission computerized tomography (SPECT), a positron emission tomography (PET) Gamma Camera), and the signal processing system 100 may be a component of such a radiation image processing apparatus.

1, the signal processing system 100 of the present invention includes a signal detector 110, an analog signal processing unit 120, and a digital signal processing unit 130. As shown in FIG.

The signal detector 110 detects radiation emitted from the radiopharmaceutical injected into the object or irradiated to the object and transmits the radiation to generate a radiation detection signal indicative of a distribution in the body or a distribution in the organ. To this end, the signal detector 110 includes a plurality of optical sensors for converting a scintillation signal output from a scintillator (not shown) that converts radiation into a scintillation signal into an electrical signal, and a plurality of semiconductors Sensor. At this time, a photodiode may be used as the optical sensor, but the present invention is not limited thereto. CZT may be used as a semiconductor sensor, but it is not limited thereto.

The analog signal processing unit 120 receives an electric signal for each channel output from the signal detector 110 and a plurality of threshold voltages preset from the outside and compares the input electric signal with a different threshold voltage And generates a plurality of comparison signals. The analog signal processing unit 120 includes an amplifier 121, a signal combining unit (not shown), and a plurality of comparators 122, 123, 124, and 125.

The amplifier 121 receives the electric signals for each channel outputted from the signal detector 110 and amplifies the electric signals so that the gains of the electric signals are uniform.

The plurality of comparators 122, 123, 124 and 125 receive a different threshold voltage from the electrical signal output from the signal detector 110, and compare the threshold voltages with each other to generate a plurality of comparison signals.

2 is an example of an input / output signal of a comparator according to an embodiment of the present invention. As shown in FIG. 2, the electrical signal amplified through the amplifier 121 passes through a plurality of comparators 122, 123, 124 and 125 having different threshold voltages, and is converted into a comparison signal. Thereafter, the comparison signal is input to the digital signal processing unit 130. [

Although the four comparators 122, 123, 124, and 125 are used to generate four different comparison signals in FIGS. 1 and 2, the present invention is not limited thereto. The number of comparators can be set to various numbers, so that a different number of different threshold voltages can be set.

1, the digital signal processing unit 130 receives a comparison signal from each of the plurality of comparators 122, 123, 124, and 125, analyzes the comparison signal, calculates reaction energy level information, reaction time information, And calculates reaction location information. In particular, the digital signal processor 130 reconstructs a pile-up signal in which two or more signals are superimposed, and obtains reaction energy level information and reaction time information of each signal. The digital signal processor 130 may include a digital signal processor (DSP) 134 for restoring signal redundancy with an FPGA (Field Programmable Gate Array) 131. Although not shown in FIG. 1, the digital signal processor 130 may further include a memory (not shown) in which a program (or at least one instruction) executable by the DSP 134 is stored.

Specifically, in response to the input of a plurality of comparison signals corresponding to multiple threshold voltages, the FPGA 131 stores the counter value of the counter 133 in operation in the FPGA 131, and then, based on the width of the counter value, And a configurable logic block (CLB) 132 for calculating the reaction energy and reaction time information of the radiation by measuring the width and measuring the pulse arrival time using the time information on which the counter value is output. At this time, the CLB 132 may obtain the reaction position information of the radiation using the position of the input / output (I / O) pin of the FPGA 131 to which the comparison signal is inputted.

At this time, the CLB 132 determines whether the input signal is duplicated based on the plurality of comparison signals input to the FPGA 131. [ The signal overlap is detected by overlapping a plurality of radiation signals, which are measured in a superimposed state at a lower threshold voltage, but are not superimposed at an upper threshold voltage. Thus, the CLB 132 can determine the overlap of the signal when the comparison signal input corresponding to the lowest threshold voltage has one pulse while the comparison signal input corresponding to the other threshold voltage has two or more pulses. have. FIG. 3 shows an example in which the signal redundancy 310 is input to the FPGA 131. FIG. The CLB 132 receives two or more pulses from a third input pin (I / O) of the FPGA 131 and receives one pulse from the first input pin (I / O) Signal duplication can be distinguished.

On the other hand, as signal redundancy is input to the FPGA 131, the FPGA 131 can provide an event signal to the DSP 134 to restore the signal redundancy. For example, the FPGA 131 may provide the pulse width and pulse arrival time information measured by the FPGA 131 to the DPS 134 as the input signal is determined as a signal overlap.

In the above description, the digital signal processor 130 includes the FPGA 131 and the DSP 134, but the present invention is not limited thereto. For example, the digital signal processor 130 may include an application specific integrated circuit (ASIC), a micro-core, or the like.

4 is a flowchart illustrating a restoration process performed by the digital signal processor 130 according to an embodiment of the present invention.

First, the digital signal processor 130 determines whether the signal is duplicated as described above (S400). For example, if the FPGA 131 determines that the signal is redundant, the DSP 134 may perform the following restoration process according to an event signal from the FPGA 131. [

Specifically, the digital signal processor 130 divides the signal redundancy into a plurality of signals according to the number of pulses included in the comparison signal (S410). For example, the digital signal processor 130 may divide the signal redundancy into a plurality of signals based on the number of pulses included in the comparison signal corresponding to the greatest threshold voltage having the largest number of pulses.

Then, the digital signal processor 130 calculates the pulse width of each signal according to the threshold voltage (S420). The digital signal processor 130 may calculate the pulse width for each of the plurality of signals based on the pulse width and the slope of the radiation signal at the highest threshold voltage of each signal measured. On the other hand, it is assumed that the slope of the above-mentioned radiation signal is constant regardless of the magnitude of the reaction energy of the radiation. Accordingly, the rise time and fall time of the radiation signal can be calculated through an exponential function derived experimentally according to the above assumption. Accordingly, the digital signal processor 130 can calculate the pulse width for each threshold voltage of each signal through the following equation (1).

는 i 번째 문턱전압에 대한 펄스폭(sec)을 나타내며,

는 각 신호가 측정된 가장 높은 문턱전압에서의 펄스폭(sec)을 나타내며,

는 i번째 문턱전압을 나타낸다. EXP함수는 실험적으로 도출된 방사선 신호의 기울기 함수를 나타낸다. In the above equation,

(Sec) with respect to the i < th > threshold voltage,

Represents the pulse width (sec) at the highest threshold voltage at which each signal is measured,

Represents the ith threshold voltage. The EXP function represents the slope function of the experimentally derived radiation signal.

5, when the signal redundancy 500 is constituted by the first signal 501 and the second signal 502, the digital signal processing unit 130 outputs the first signal 501 and the second signal 502, The pulse width for each threshold voltage of the second signal 502 can be calculated. At this time, the digital signal processor 130 uses the slope function of the radiation signal and the pulse width 510 at the third threshold voltage 513, which is the highest threshold voltage at which the first signal 501 is measured, The pulse width at the second threshold voltage 512 and the pulse width at the first threshold voltage 511 of the first transistor 501 can be sequentially calculated. FIG. 6A shows an example in which the pulse width for each threshold voltage is restored for the first signal 501 of FIG.

The digital signal processing unit 130 then uses the slope function of the radiation signal and the pulse width 520 at the fourth threshold voltage 514, which is the highest threshold voltage at which the second signal 502 is measured, The pulse widths at the third to first threshold voltages 513 to 511 of the second transistor 502 can be sequentially calculated. FIG. 6B shows an example of restoring the pulse width for each threshold voltage with respect to the second signal 502 of FIG.

After that, the digital signal processor 130 reconstructs reaction energy and reaction time information of the radiation corresponding to each signal overlapping signal (S430).

First, the digital signal processor 130 calculates the energy magnitude of each signal by summing the pulse widths of the respective signals with respect to the threshold voltage. At this time, among the signal duplicated signals, the size of the energy can be distorted due to the influence of the preceding signal in the overlapping of the preceding signal and the preceding signal. Accordingly, the digital signal processing unit 130 can calculate the overlapping energy between the preceding signal and the succeeding signal, and then correct the reactive energy of the succeeding signal by subtracting the superimposed energy from the reactive energy of the succeeding signal. At this time, the overlap energy can be calculated as the sum of the results obtained by subtracting the arrival time of the following signal (i.e., the rising time of the pulse) at the end time of the preceding signal (i.e., the falling time of the pulse).

FIG. 7 is an example showing superposition energy 710 in the signal overlap of FIG. The digital signal processing unit 130 subtracts the overlapping energy 710 from the reactive energy of the second signal 502 (i.e., the sum of the pulse widths of the second signals 502) Can be restored.

On the other hand, the reaction time information is calculated based on the arrival time of each signal (that is, the rise time of the pulse) and the end time (that is, the fall time of the pulse). At this time, the time information may be determined by the output time of the counter 133 provided in the FPGA 131, for example. However, since the signal-overlapped signals do not have separated time information, the digital signal processor 130 performs a restoration operation for distinguishing them.

6A, the digital signal processor 130 receives the pulse arrival time of the preceding signal (i.e., the first signal 501) at the lowest threshold voltage (i.e., the first threshold voltage 511) The response time information of the preceding signal can be restored based on the width. That is, the arrival time 610 of the first signal 501 is equal to the pulse arrival time 610 at the first threshold voltage 511, and the end time 620 of the first signal 501 is the same as the arrival time 610 of the signal overlap And the pulse width of the first signal 501 acquired and corrected by using Equation 1 at the first threshold voltage 511 at the arrival time 610 of the first signal 501. [

6B, the response time information of the trailing signal includes the pulse arrival time of the trailing signal at the highest threshold voltage at which the trailing time is measured (i.e., the fourth threshold voltage 514) Can be restored based on the slope. That is, the arrival time 640 of the second signal 502 may be inferred according to the pulse arrival time 630 of the fourth threshold voltage 514 and the radiation signal slope function.

As described above, the signal processing system 100 according to the disclosed embodiment can improve the economical efficiency by analyzing the radiation signal without using the ADC and the TDC, and can also use the digital signal processing unit including the DSP to generate the signal By restoring redundancy in real time, signal loss and distortion due to signal overlap can be minimized.

On the other hand, an embodiment of the present invention may also be realized in the form of a recording medium including instructions executable by a computer such as a program module 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. The computer-readable medium may also 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.

While the methods and systems of the present invention have been described in connection with specific embodiments, some or all of those elements or operations may be implemented using a computer system having a general purpose hardware architecture.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

100: signal processing system
110: Signal detector
120: Analog signal processor
130: Digital signal processor
131: Field programmable gate array (FPGA)
132: a digital signal processor (DSP)

Claims (13)

In a signal processing system using multiple threshold voltages,
A signal detector including a plurality of optical sensors for converting a scintillation signal output from a scintillator unit for converting radiation into a scintillation signal into an electric signal or a plurality of semiconductor sensors for directly converting radiation;
An electric signal for each channel outputted from the signal detector and a predetermined plurality of different threshold voltages and for comparing the electric signal and the signals according to the plurality of different threshold voltages to generate a plurality of comparison signals An analog signal processor; And
And a digital signal processor for receiving the comparison signal output from the analog signal processor and acquiring reaction energy magnitude information, reaction time information, and reaction position information of the radiation in response to the input comparison signal,
The digital signal processing unit
Determining whether the signals are overlapped or not based on whether the at least one comparison signal has two or more pulses, and if the at least one comparison signal is overlapped, determining whether each of the plurality of signals constituting the signal overlap And corresponding reaction energy magnitude information and reaction time information. The method according to claim 1,
Wherein the digital signal processor comprises:
Wherein a comparison signal input corresponding to the lowest threshold voltage is comprised of one pulse and a comparison signal having two or more pulses corresponding to the other threshold voltage is input, . The method according to claim 1,
The digital signal processing unit
Dividing the signal redundancy into a plurality of signals according to the number of pulses included in the comparison signal, calculating a reactive energy value of each of the signals by adding the pulse widths of the respective threshold voltages of the respective signals, And corrects the reactive energy value of the signal. The method of claim 3,
The digital signal processing unit
Wherein the signal processing system calculates the overlapping energy value between the preceding signal and the following signal and corrects the reactive energy of the following signal by subtracting the overlapping energy value from the reactive energy of the succeeding signal. The method of claim 3,
The digital signal processing unit
Measuring response time information of the preceding signal based on a pulse arrival time of the preceding signal at the lowest threshold voltage,
And the response time information of the trailing signal is restored based on the pulse arrival time of the trailing signal at the highest threshold voltage at which the trailing signal is measured and the slope of the measurement signal. The method according to claim 1,
The digital signal processing unit
Calculating a pulse width for each of the plurality of signals based on the pulse width and the slope of the radiation signal at the highest threshold voltage of each of the plurality of signals,
The slope of the radiation signal
Wherein the signal processing system is represented by an empirically derived equation. The method according to claim 1,
The digital signal processor includes a field programmable gate array (FPGA) and a digital signal processor (DSP)
The FPGA
Storing a counter value being driven in response to input of a plurality of comparison signals corresponding to the multiple threshold voltage, measuring a pulse width for each threshold voltage based on the width of the counter value, (I / O) pin for receiving the comparison signal, and calculating position information based on the position of the input /
And provides the DSP with the pulse width and pulse arrival time information for each threshold voltage when the plurality of comparison signals are judged as a signal overlap,
The DSP
Based on the threshold pulse width and pulse arrival time information, restores reaction energy magnitude information and reaction time information corresponding to each of the plurality of signals constituting the signal overlap. The method according to claim 1,
The analog signal processing unit
An amplifier for receiving the radiation detection signal for each channel and amplifying the radiation detection signal so that the gain of the radiation detection signal is uniform; And
A plurality of comparators for receiving the amplified plurality of radiation detection signals and the plurality of different threshold voltages and for comparing the radiation detection signal and signals corresponding to the plurality of different threshold voltages to generate the plurality of comparison signals, The signal processing apparatus comprising: A method for restoring a signal-duplicated signal in a signal processing system for analyzing a radiation signal using a multi-threshold voltage,
Generating a plurality of comparison signals according to a result of comparing the detected signal with a plurality of different threshold voltages after detecting a radiation signal;
Determining whether the signals are signal redundant signal duplication according to whether at least one of the plurality of comparison signals has two or more pulses;
Dividing the signal redundancy into a plurality of signals according to the number of pulses included in the at least one comparison signal; And
And restoring reaction energy information and reaction time information of the radiation corresponding to each of the plurality of signals based on the pulse width of each of the plurality of signals by the threshold voltage. 10. The method of claim 9,
The step of determining whether the signal is duplicated
Wherein if the comparison signal corresponding to the lowest threshold voltage is composed of one pulse and the comparison signal corresponding to the other threshold voltage comprises two or more pulses, it is determined that the signal is redundant. 10. The method of claim 9,
The step of restoring the reaction energy information
Calculating a reaction energy value of each signal by adding the pulse widths of the plurality of signals to each threshold voltage;
Calculating an overlapping energy value between the preceding signal and the succeeding signal of the signal overlap; And
And correcting the reactive energy value of the trailing signal by subtracting the overlapping energy value from the reactive energy of the trailing signal. 12. The method of claim 11,
The step of restoring the reaction time information
Measuring response time information of the preceding signal based on a pulse arrival time of the preceding signal at the lowest threshold voltage; And
And restoring the measurement time information of the trailing signal based on the pulse arrival time of the trailing signal at the highest threshold voltage at which the trailing signal is measured and the slope of the measurement signal. A computer-readable recording medium on which a program for executing the method according to any one of claims 9 to 12 is recorded.

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