CN105411588B - The safety monitoring device and method of MRI machine - Google Patents
The safety monitoring device and method of MRI machine Download PDFInfo
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- CN105411588B CN105411588B CN201510718247.1A CN201510718247A CN105411588B CN 105411588 B CN105411588 B CN 105411588B CN 201510718247 A CN201510718247 A CN 201510718247A CN 105411588 B CN105411588 B CN 105411588B
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7271—Specific aspects of physiological measurement analysis
- A61B5/7285—Specific aspects of physiological measurement analysis for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal
- A61B5/7289—Retrospective gating, i.e. associating measured signals or images with a physiological event after the actual measurement or image acquisition, e.g. by simultaneously recording an additional physiological signal during the measurement or image acquisition
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2560/00—Constructional details of operational features of apparatus; Accessories for medical measuring apparatus
- A61B2560/02—Operational features
- A61B2560/0266—Operational features for monitoring or limiting apparatus function
Abstract
The present invention relates to a kind of safety monitoring device of MRI machine, including：RF signal input modules, gather simultaneously input rf signal；SAR value monitoring module, receives the RF signals, calculates SAR value；Gradient signal input module, gathers simultaneously input gradient signal；PNS stimulates monitoring module, receives the gradient signal, calculates PNS values；System management module, when the SAR value monitoring module and PNS stimulate the result of calculation of monitoring module to exceed threshold value, signal an alert is to host computer；Wherein, the SAR value monitoring module, including：First SAR sliding average computation subunits, for calculating the first SAR sliding averages；2nd SAR sliding average computation subunits, for calculating the 2nd SAR sliding averages, the first SAR sliding averages corresponding sampling time is longer than the 2nd SAR sliding averages corresponding sampling time.
Description
Technical field
The present invention relates to field of medical device, more particularly in MR imaging apparatus the safety monitoring device of patient and its
Method.
Background technology
In magnetic resonance imaging (hereinafter referred to as：MRI) in technology, with the increase of magnetic resonance main field field strength, radio frequency swashs
Send out pulse (hereinafter referred to as：RF pulses) power also increase as, the energy part that RF pulses are loaded is released with form of heat
Release, absorbed by human body, cause the rise of its body temperature.If be not controlled by the heat of RF pulses generations, it is produced
Raw heat can cause patient's topical burn, tachycardias, stupor even dead.Therefore, in the magnetic resonance equipment of high field intensity, it is
The problems such as avoiding causing patient's localized thermal damage, MRI scan introduces a kind of brand-new protection concept, i.e. RF energy absorbs
Rate, and RF energy absorptivity (Specific Absorption Rate, hereinafter referred to as：SAR it is) human body per weight in list
The RF energy absorbed in the time of position, measurement unit W/kg.SAR value is as tissue interior energy caused by assessment RF pulses
The index of distribution is measured, can effectively weigh influence caused by RF pulses rise body surface temperature, while reflect tissue
The possibility for the pyrolytic damage being subject to.
In addition to the heat injury that tissue caused by the RF pulses is subject to, in MRI machine, the ladder of gradient coil
Degree field, which is switched fast, also can cause human nerve tip to inspire electric current, so as to stimulate the peripheral nerve (Peripheral of human body
Nervous System, hereinafter referred to as：PNS) and muscle, special cardiac stimulus, can produce human body tingling sensation.
Currently for MRI products, FDA (the Food and Drug Administration in the U.S.：U.S.'s food and medicine prison
Superintend and direct management board) etc., all to being defined in terms of safety index laws and regulations.The difficult point of the prior art is how to carry out SAR value
Accurate with PNS values calculates.Since the mode of calculating is varied, ununified method can be followed, particularly 1.5T to
3T develops, and causes magnetic field intensity higher and higher；And single channel launches development to multichannel, calculating is caused to become increasingly complex, at the same time
FDA etc. is more and more stringenter to these aspect requirements, exacerbates theoretical research to the difficulty of clinical practice.
The content of the invention
The present invention is in order to solve difficult point of the prior art, it is proposed that a kind of SAR value and PNS for calculating different sampling stages
The real time and on line monitoring system of values.
To solve the above problems, the present invention provides a kind of safety monitoring device of MRI machine, including：
RF signal input modules, gather simultaneously input rf signal；
SAR value monitoring module, receives the RF signals, calculates SAR value；
Gradient signal input module, gathers simultaneously input gradient signal；
PNS stimulates monitoring module, receives the gradient signal, calculates PNS values；
System management module, when the result of calculation of the SAR value monitoring module and PNS stimulation monitoring modules exceeds threshold value
Signal an alert is to host computer；
Wherein, the SAR value monitoring module, including：
First SAR sliding average computation subunits, for calculating the first SAR sliding averages；
2nd SAR sliding average computation subunits, for calculating the 2nd SAR sliding averages,
It is longer than that the 2nd SAR sliding averages are corresponding to be adopted the first SAR sliding averages corresponding sampling time
The sample time
Optionally, the first SAR sliding averages computation subunit and the 2nd SAR sliding averages computation subunit point
Do not include：
Whole body SAR value calculator, for calculating whole body SAR sliding averages, and
Local SAR value calculator, for calculating local SAR sliding average.
Optionally, the safety monitoring device, further includes：
Demodulation module, RF signals are demodulated into after base band small-signal and are sent to SAR value monitoring module.
Optionally, the safety monitoring device, further includes：
Optical port module, receives RF signals, eliminates the interference in the RF signals, and is sent to SAR value monitoring module, and/
Or, gradient signal is received, the interference in the gradient signal is eliminated, and be sent to PNS to stimulate monitoring module.
Optionally, the SAR value monitoring module further includes：
Sample point energy calculation unit, according to the voltage on the voltage and transmitting coil on transmission line, calculates each sample
The energy of this point；
Accumulated energy computing unit, including the first SAR sliding averages computation subunit and the 2nd SAR sliding averages
It is worth computation subunit, and calculates the cumulant that patient absorbs energy.
Optionally, the sample point energy calculation unit includes：
Transmitting coil voltage computation subunit, for calculating the voltage on transmitting coil；
Transmitting coil energy balane subelement, for calculating the emitted energy on transmitting coil；And
Transmitting coil energy loss calculation subelement, for calculating the off-energy on transmitting coil.
Optionally, the accumulated energy computing unit includes：
Transmitting coil energy accumulation subelement, the transmitting coil emitted energy of unit of account time；
Transmitting coil energy loss adds up subelement, the off-energy of unit of account time transmitting coil；
Energy accumulation subelement is absorbed, is inhaled according to the emitted energy of transmitting coil and off-energy calculating patient's unit interval
Receive SAR value；
The first SAR sliding averages computation subunit and the 2nd SAR sliding average computation subunits are according to institute
Stating patient's unit interval absorbs SAR value and calculates the first SAR sliding averages and the 2nd SAR sliding averages.
Optionally, the accumulated energy computing unit further includes：
Patient absorbs energy accumulation subelement, absorbs the accumulation of energy for calculating the patient, and be sent to system
Management module.
Optionally, the accumulated energy computing unit further includes：
Maximum SAR value computing unit, knot is calculated according to the first SAR sliding averages and the 2nd SAR sliding averages
Fruit obtains maximum first SAR sliding averages and maximum 2nd SAR sliding averages, and is sent to system management module.
Optionally, the accumulated energy computing unit further includes：
Computation subunit is verified, the first SAR sliding averages and the 2nd SAR sliding averages are verified respectively, sentenced
Determine whether SAR value transfinites, if transfiniting, the defeated signal that transfinites is to system management module.
Optionally, the PNS stimulates monitoring module to include：
Gradient stimulates PNS computing units, and the PNS values in X, Y, Z axis is calculated according to gradient signal；
PNS computing units, calculate the total values of three axis of three axis；
Maximum value calculation unit, calculates the maximum of total values；And
PNS verification units, are verified according to the PNS values in X, Y, Z axis and maximum.
Optionally, the gradient stimulates PNS computing units to include：
Gradient change rate computation subunit, the gradient climb rate is calculated according to gradient data；
PNS computation subunits, the PNS values of tri- axis of X, Y, Z is calculated according to the gradient climb rate；And
PNS maximum value calculation subelements, calculate the single shaft maximum PNS values of tri- axis of X, Y, Z.
The present invention also provides a kind of method for safety monitoring of MRI machine, including：
Gather RF signals and gradient signal；
SAR value is calculated according to the RF signals；
PNS values is calculated according to signal is carried；
The signal an alert when the SAR value and PNS values exceed threshold value；
The SAR value includes the first SAR sliding averages and the 2nd SAR sliding averages,
It is longer than that the 2nd SAR sliding averages are corresponding to be adopted the first SAR sliding averages corresponding sampling time
The sample time.
Optionally：
The first SAR sliding averages are the first SAR sliding averages of local first SAR sliding averages and whole body；
The 2nd SAR sliding averages are the 2nd SAR sliding averages of local 2nd SAR sliding averages and whole body.
Optionally, the method for safety monitoring, further includes：
SAR value is calculated again after RF signals are demodulated into base band small-signal.
Optionally, the method for safety monitoring, further includes：
Collection RF signals are carried out to calculate SAR value after disturbing in elimination signal, and/or, disappear to collection gradient signal
Except in signal disturb after calculate SAR value.
Optionally, calculating SAR value according to the RF signals includes：
According to the voltage on the voltage and transmitting coil on transmission line, the energy of each sample point is calculated；
According to the first SAR sliding averages of sample point energy balane and the 2nd SAR sliding averages, and calculate patient
Absorb the cumulative amount of energy.
Optionally, each sample point energy of calculating includes：
Calculate transmitting coil voltage；
The emitted energy of transmitting coil is calculated according to the transmitting coil voltage；
The parameter and transmitting coil voltage that are there is provided according to system calculate the off-energy on transmitting coil.
Optionally, when multichannel is launched：
Calculate each channel emission coil voltage；
The emitted energy of each transmitting coil is calculated according to each channel emission coil voltage；
The parameter and each transmitting coil voltage that are there is provided according to system calculate the off-energy on each transmitting coil；
The emitted energy is the sum of emitted energy of each passage；And
The off-energy is the sum of off-energy of each passage.
Optionally, the method for safety monitoring, further includes
The emitted energy of the transmitting coil of unit of account time；
The off-energy of the transmitting coil of unit of account time；
The SAR value absorbed according to the emitted energy of the transmitting coil and off-energy calculating patient's unit interval
The first SAR sliding averages and the 2nd SAR slide sliding average and are absorbed according to patient's unit interval
SAR value calculates
The method for safety monitoring, is additionally included in and calculates SAR value that patient's unit interval absorbs at the same time：
Patient is calculated to add up the energy of absorption, when the patient adds up the energy of absorption exceedes threshold value when send alarm.
Optionally, the method for safety monitoring, further includes：
By the first SAR sliding averages and the 2nd SAR sliding averages compared with threshold value, if being sent when exceeding threshold value
Alarm.
Optionally, it is described to be included according to gradient signal calculating PNS values：
PNS values in X, Y, Z axis is calculated according to gradient signal；
Calculate the total values of three axis of three axis；
Calculate the maximum value calculation maximum of total values；And
PNS values in the X, Y, Z axis and maximum are verified.
Optionally, the calculating of the PNS carried out according to gradient signal in X, Y, Z axis includes：
The gradient climb rate is calculated according to gradient data；
The PNS values of tri- axis of X, Y, Z is calculated according to the gradient climb rate；And
Calculate the single shaft maximum PNS values of tri- axis of X, Y, Z.
Compared with prior art, (Full Body Longtime) SAR value is (when long when the present invention proposes a kind of long to whole body
For 360 seconds)；Whole body (Full Body Shorttime) SAR value (being in short-term 10 seconds) in short-term；(Part Body when local long
Longtime) SAR value；The method that local four kinds of modes of (Part Body Showtime) SAR value in short-term monitor at the same time, more comprehensively
Guarantee monitoring accuracy.This safety monitoring system can not only calculate actual SAR and PNS values in real time,
Consistency desired result can be done with expected theory SAR and PNS values at the same time, prevent the SAR of patient's actual absorption in MRI machine
With PNS values and expected value difference not it is excessive cause monitoring slip up caused by patient by Shanghai.And proposed in the present invention
When SAR or PNS values reaches certain threshold value, MRI is automatically stopped scanning, stops certain time, treats that part is absorbed
When energy is discharged into safe range, MRI restarts.Ensure the safety of patient in scanning process.
Brief description of the drawings
Fig. 1 is the security monitoring portion structure diagram of MRI machine according to the present invention；
Fig. 2 is the structure diagram of SAR value monitoring module according to the present invention；
Fig. 3 is the structure diagram of sample point energy calculation unit according to the present invention；
Fig. 4 is the structure diagram of accumulated energy computing unit according to the present invention；
Fig. 5 is the structure diagram that PNS according to the present invention stimulates monitoring module；
Fig. 6 is the structure diagram of PNS computing units according to the present invention.
Embodiment
It is understandable to enable the above objects, features and advantages of the present invention to become apparent, below in conjunction with the accompanying drawings to the present invention
Embodiment be described in detail.Detail is elaborated in the following description in order to fully understand the present invention.But
It is that the present invention can be implemented with a variety of different from other manner described here, those skilled in the art can be without prejudice to originally
Similar popularization is done in the case of invention intension.Therefore the limitation of the invention from following public embodiment.
Fig. 1 is a kind of structure diagram in the security monitoring portion on MRI machine.The security monitoring portion of MRI machine includes：
RF control inputs module 1, the energy datum issued to 4 input system of optical port module, pulse switch and sequence switch data etc.；RF
Signal input module 2, gathers RF signals, and the RF signals are sent to optical port module 4；Gradient signal input module 3, collection
Gradient signal, and the gradient signal is sent to optical port module 4；Clock module 13, input clock signal, makes modules meter
Count according to synchronization；Optical port module 4, receives the interface of data, strong antijamming capability, optionally eliminates and receive doing in signal
Disturb；Demodulation module 5, will send SAR value monitoring module 6 to after the RF signals decoding Jing Guo optical port module 4；SAR value monitors mould
Block 6, SAR value is calculated according to the RF signals after the demodulation of input；Gradient optical module (not shown), is integrated in optical port module 4,
Monitoring module 7 is stimulated by PNS is sent to after gradient signal decoding；PNS stimulates monitoring module 7, is transmitted according to gradient optical module
Decoded gradient signal carry out PNS values calculating；SAR value monitoring module 6 and PNS stimulate monitoring module 7 by result
It is reported to system management module 10；System management module 10, stimulates SAR value monitoring module 6 and PNS the calculating of monitoring module 7
As a result it is managed；Register mappings module 8, the calculating parameter provided for register system, and while being calculated for each module, use,
Because each parameter has a register address, corresponding parameter can be read and write according to address；Host computer interface module 12 is
PCIe modules：Host computer can read monitoring data by slot；Program online updating module 9：For updating security monitoring portion
Logical program, there is provided online updating function, avoids dismantling equipment and goes program in renewal hardware circuit board；Acquisition control module
11, for scanning when gathers primary RF signals, SAR value monitoring module 6 and PNS in real time stimulates the result of calculation of monitoring module 7,
And host computer is sent to, its result of calculation is verified for host computer.The host computer controls system for the overall of MRI machine
System, including for showing the man-machine interface display system of various parameters.
The monitoring process in above-mentioned security monitoring portion is illustrated below.Pass through RF control inputs module 1, clock module
13rd, RF signal input modules 2 and gradient signal input module 3 obtain RF signals during MR system imagings, gradient signal, control
Signal processed and clock signal；Denoising is carried out to the various signals of acquisition；RF signals are demodulated, the tune for making collection come in
Ripple processed is demodulated to baseband signal, and (what collection came in is modulating wave, it is necessary to carry out signal demodulation to the modulating wave, demodulates the base come
Band signal is only the original signal really needed), and the parameter meter provided by SAR value monitoring module 6 according to RF signals and system
Calculate the SAR value of human body；At the same time, stimulate monitoring module 7 according to the parameter that gradient signal and system provide into pedestrian by PNS
The monitoring of body PNS values；Finally the SAR value of the human body and the PNS values of human body are carried out by system management module 10
Manage and report in host computer.System management module 10 mainly management interacted with host computer, perform report overload alarm (SAR value,
PNS values) and removing overload alarm.System management module 10 is an interrupt management function module, if a variety of monitoring knots
Fruit is all transfinited, it is necessary to which system management module 10 determines processing sequence.The administrative staff of upper computer end are according to anti-during described
The SAR value and PNS values of feedback judge whether to continue to scan.It is described report host computer during, SAR value and PNS are stimulated
Value can be sent in host computer when exceeding certain threshold value with alert methods, easy to cause the attention of administrative staff.
SAR value monitoring module 6 and PNS stimulate the core calculation module that monitoring module 7 is security monitoring portion.Below according to attached
Fig. 2 to 6, stimulates monitoring module 7 to be described in detail SAR value monitoring module 6 and PNS.
Fig. 2 is the structure diagram of SAR value monitoring module 6 according to the present invention.SAR value monitoring module 6 mainly by：Data
Synchronization unit 61, calculates for the RF signals of cross clock domain to be synchronized to PCIe clock domain to synchronize, and the RF signals are
There is provided by demodulation module 5；Parameter pretreatment unit 62, the systematic parameter calculated participating in SAR value are anticipated, the system
Parameter of uniting is provided by register mappings module 8；Sample point energy calculation unit 63, according to the voltage and emission lines on transmission line
Voltage on circle, calculates the energy of each sample point；Consistency desired result unit 64, energy is during for calculating RF sequence transmissions
It is no consistent (being issued it is expected that emitted energy is system) with expected emitted energy, to the error of check system energy；Accumulated energy
Computing unit 65, the SAR value absorbed for calculating human body to add up, hardware on-line monitoring unit 66：For by sample point energy meter
The voltage calculated on transmission line and transmitting coil that unit 63 calculates is monitored, and judges whether maximum voltage transfinites.
The SAR value calculating process of SAR value monitoring module 6 is illustrated below.First, demodulation module 5 is sent
RF signals after demodulation are synchronized to PCIe clock domain and synchronize calculating, cross clock domain processing such as from 10Mhz data rate synchronous to
Accelerate to calculate under 125Mhz clocks；Meanwhile parameter needed for calculating is pre-processed, the parameter includes, power and frequency
Rate calibration parameter, rate of energy loss parameter, also have threshold parameter such as voltage threshold, SAR thresholdings, tolerance etc. of some monitoring,
The pretreatment includes, and simplifies calculating as the conversion of floating number and fixed-point number, parameter in advance merge, some parameters are differentiated, also
The transmission coefficient of transmission coefficient, sample time and transmitting coil including calculating transmission line, these parameters are that system calibration is surveyed
Measure what is come, system can calibrate during start, and system can issue these parameters during scanning, be obtained by register mappings module 8；Root
According to the RF signals and pretreatment system parameter after the synchronization, the energy of each sample point is calculated；According to the energy of the sample point
Amount calculates different time and the accumulated energy at position again；At the same time by energy during RF sequence transmissions whether with being expected emitted energy one
Cause to be verified to the error of system capacity, and the voltage on transmission line and transmitting coil is monitored, if voltage transfinites,
Radio-frequency power amplifier is turned off, stops scanning, shows that voltage transfinites and alarms on host computer.
Fig. 3 is sample point energy calculation unit structure diagram according to the present invention.Sample point (the radiofrequency signal collected
Value) energy calculation unit 63 major function be to calculate the energy of each sample point, on the voltage and transmitting coil on transmission line
Voltage.As shown in the figure, it includes：S parameter computation subunit 630：According to it is preceding to (FWR) and reverse (REF) rf data and
Transmission line coefficient (Tcable) and coil factor (Tcoil) calculate tetra- parameter (coefficients of S11, S12, S21, S22 respectively
It is that system calibration is got with parameter), while result is transmitted to transmitting coil voltage computation subunit 631 and transmission-line voltage
Computation subunit 632；Transmitting coil voltage computation subunit 631, calculates the voltage (Ucoil) of transmitting coil；Transmission-line voltage
Computation subunit 632, calculates the voltage (Ucable) of transmission line；Transmitting coil energy balane subelement 633, according to having calculated that
Transmitting coil voltage calculate sampling time corresponding energy；Transmitting coil energy loss calculation subelement 634, according to having calculated
The transmitting coil voltage and loss late gone out calculates the energy of transmitting coil loss；Result of calculation synchronism output subelement 635, by institute
There is result of calculation to snap to same rising edge clock output.
The calculating process of sample point energy calculation unit 63 is illustrated below：Obtain the forward direction (FWR) in RF signals
With reverse (REF) rf data and transmission line coefficient (Tcable) and coil factor (Tcoil)；According to the data calculate S11,
Tetra- parameters of S12, S21, S22 (S parameter is the theory in microwave transmission equation, is 2 × 2 matrixes, by S11, S12, S21,
Tetra- elements of S22 are formed, and the parameter in magnetic resonance system is calculated as the prior art, and details are not described herein)；According to the parameter
Coil voltage and transmission-line voltage are calculated, it is necessary to calculate the biography on first passage and second channel respectively when binary channels is launched
Voltage and transmitting coil voltage on defeated line；Then, according to the sampling time of transmitting coil and the transmitting coil calculated electricity
Pressure, it is possible to calculate transmission power；And then the hair of transmitting coil is calculated according to the transmission power of coil and sampling time
Energy and off-energy are penetrated, rate of energy loss parameter is calculated when being corrected by system；, it is necessary to calculate respectively when multichannel is launched
The energy of each pass loss, is then added and just obtains the total energy loss of transmitting coil by the loss late of each channel energy；Finally
Operation is synchronized to result of calculation, is synchronously in order to solve the problems, such as cross clock domain, from transmitting coil energy balane subelement
633 is asynchronous with the input data of transmitting coil energy loss calculation subelement 634, so needing synchronously defeated by result of calculation
Go out subelement 635 and be synchronized to 125Mhz and export at the same time.
Fig. 4 is the structure diagram of accumulated energy computing unit according to the present invention.As shown in the figure, accumulated energy calculates list
Member 65 includes：Time counting subelement 651, when patient's new registration timing；Time signal is exported to emission lines at the same time
Circle energy accumulation subelement 652 and transmitting coil energy loss add up subelement 653；Transmitting coil energy accumulation subelement 652
With transmitting coil energy loss add up subelement 653 according to the time come add up the unit interval (such as 1 second) emitted energy and loss
Energy, finally exports and gives absorption energy balane subelement 654；Energy balane subelement 654 is absorbed, calculates patient's unit interval
The energy that (such as 1 second) absorbs；Patient absorbs energy accumulation subelement 655, and absorbing energy balane patient according to the unit interval adds up
The energy of absorption；SAR sliding averages computation subunit 656 and SAR sliding averages computation subunit 657 in short-term, root when long
(such as 360S) and in short-term the SAR sliding averages of (such as 10S) are absorbed when energy first calculates long respectively according to patient's unit interval, at the same time
SAR sliding averages computation subunit 656 and the SAR value that SAR sliding averages computation subunit 657 will calculate in short-term when long
Export to maximum SAR value transmission sub-unit 658；Maximum SAR value transmission sub-unit 658, maximum is obtained according to above-mentioned result of calculation
SAR sliding averages and SAR sliding averages are sent to system management module 10 when most greatly enhancing when long, verify computation subunit
659th, SAR value is verified, judges whether SAR value transfinites, if transfinited, export high level useful signal (over
Limit) and it is sent to system management module 10.
The calculating process of the accumulated energy computing unit 65 in SAR value monitoring module 6 is illustrated below.In new patient
During registration, generation system is resetted (Warm_reset) signal by system, and time counting subelement 651 starts the meter of one second one second
When, transmitting coil energy and transmitting coil the off-energy progress calculated by above-mentioned sample point energy calculation unit is temporal tired
Add, and cumulative transmitting coil energy and off-energy are sent to and absorb energy balane subelement 654, when calculating human body unit
Between the energy that absorbs, the unit interval, which absorbs energy and subtracts the unit interval equivalent to unit interval emitted energy, receives energy and unit
Loss of time energy；SAR sliding averages when energy calculates long respectively are absorbed further according to the unit interval and SAR is slided in short-term
Average value, described two average values can be respectively divided into whole body SAR average values and local SAR average value again, i.e., every 10 seconds or
The average power of 360 seconds, while by these energy and body part factor local factors (part body factor) and whole body
The factor (full body factor), which is multiplied, has obtained the SAR value of corresponding site；Finally the SAR value is verified, works as hair
It is existing to send the signal that transfinites when transfiniting.
Fig. 5 is the structure diagram that PNS according to the present invention stimulates monitoring module.As shown in the figure, PNS stimulates monitoring module
7 include：Data synchronization input unit 71, receives gradient signal, gradient data and system ginseng to the X, Y, Z axis in gradient signal
Number carries out the synchronization process of cross clock domain；Gradient stimulates PNS computing units 72, and the calculating of PNS is carried out according to above-mentioned synchrodata,
Send result of calculation to maximum value calculation unit 74 at the same time；Maximum value calculation unit 74, obtains according to the PNS result of calculations of three axis
Go out total values, and obtain the maximum of the total values of three axis, and be sent to PNS verification units 75；PNS verification units 75 are right
The total values of three axis, and the total irritation level maximum (PNS_totalmax) of three axis carry out implementing monitoring and consistency desired result.
The monitoring process for stimulating monitoring module 7 to PNS below illustrates.First according to the gradient signal and system of input
Parameter synchronizes processing, calculates X-axis (PNS_core_X), Y-axis (PNS_core_Y), Z axis (PNS_core_Z) respectively
PNS, it is consistent that the PNS of three axis, which stimulates value calculating method,；PNS computing units 73, by the PNS_X, PNS_Y calculated,
PNS_Z is summed to obtain the total values of three axis (PNS_total) of three axis, then carries out maximum to total values
Calculate and consistency desired result, consistency desired result are to allow the PNS values actually calculated to determine whether compared with desired value in tolerance
In the range of, it is whether normal with decision-making system stabilization and calculating, if by verification, if transfinited, report the value that transfinites
(overlimit)。
Fig. 6 is the structure diagram that gradient according to the present invention stimulates PNS computing units.As shown in the figure, PNS computing units
72 include：Gradient change rate computation subunit 721, the gradient climb rate is calculated according to gradient signal；Gradient stimulates effective time
Count sub-element 722, stimulates effective time to carry out timing gradient；Gradient stimulates limit value computation subunit 723, according to the meter
When result and the gradient climb rate calculate the limit value of PNS in real time, while send result to PNS computation subunits 724；PNS is counted
Operator unit 724, the PNS of tri- axis of X, Y, Z is calculated according to the PNS limit values；PNS maximum value calculations subelement 725, for calculating
And export the PNS maximums of tri- axis of X, Y, Z.
Stimulated below in conjunction with gradient stimulates the monitoring process of monitoring module to illustrate during PNS computing units 72.Root first
The gradient climb rate is calculated according to gradient data, then the gradient climb rate and the threshold value set are compared, if it is determined that climbing
When rate is more than threshold value, start the stimulation monitoring of PNS, the threshold value is issued by system, for doing the judgement that switch is opened in PNS monitoring
Condition；Effective time and the gradient climb rate is stimulated to calculate the limit value of PNS further according to gradient, PNS computation subunits 724, be used for
PNS, the PNS=deltaG/Limit of tri- axis of X, Y, Z are calculated, wherein Limit is the PNS limit values that previous step calculates,
DeltaG is gradient change rate；Finally calculate the single shaft PNS maximums of output tri- axis of X, Y, Z.
Although the present invention is disclosed as above with preferred embodiment, it is not for limiting the present invention, any this area
Technical staff without departing from the spirit and scope of the present invention, may be by the methods and technical content of the disclosure above to this hair
Bright technical solution makes possible variation and modification, therefore, every content without departing from technical solution of the present invention, according to the present invention
Any simple modifications, equivalents, and modifications made to above example of technical spirit, belong to technical solution of the present invention
Protection domain.
Claims (22)
1. a kind of safety monitoring device of MRI machine, including：
RF signal input modules, gather simultaneously input rf signal；
SAR value monitoring module, receives the RF signals, calculates SAR value；
Gradient signal input module, gathers simultaneously input gradient signal；
PNS stimulates monitoring module, receives the gradient signal, calculates PNS values, including data synchronization input unit, gradient
Stimulate PNS computing units, maximum value calculation unit and PNS verification units；
System management module, sends when the result of calculation of the SAR value monitoring module and PNS stimulation monitoring modules exceeds threshold value
Alarm signal is to host computer；
Wherein, the SAR value monitoring module, including：
First SAR sliding average computation subunits, for calculating the first SAR sliding averages；
2nd SAR sliding average computation subunits, for calculating the 2nd SAR sliding averages,
When the first SAR sliding averages corresponding sampling time is longer than the 2nd SAR sliding averages corresponding sampling
Between；The first SAR sliding averages computation subunit and the 2nd SAR sliding average computation subunits are according to patient's unit
Time absorbs SAR value and calculates the first SAR sliding averages and the 2nd SAR sliding averages；
The SAR value monitoring module further includes：
Sample point energy calculation unit, according to the voltage on the voltage and transmitting coil on transmission line, calculates each sample point
Energy；
Accumulated energy computing unit, including the first SAR sliding averages computation subunit and the 2nd SAR sliding average meters
Operator unit, and calculate the cumulant that patient absorbs energy.
2. safety monitoring device according to claim 1, the first SAR sliding averages computation subunit and second
SAR sliding average computation subunits include respectively：
Whole body SAR value calculator, for calculating whole body SAR sliding averages, and
Local SAR value calculator, for calculating local SAR sliding average.
3. safety monitoring device according to claim 1, further includes：
Demodulation module, RF signals are demodulated into after base band small-signal and are sent to SAR value monitoring module.
4. safety monitoring device according to claim 1, further includes：
Optical port module, receives RF signals, eliminates the interference in the RF signals, and is sent to SAR value monitoring module, and/or, connect
Gradient signal is received, eliminates the interference in the gradient signal, and is sent to PNS to stimulate monitoring module.
5. safety monitoring device according to claim 2, the sample point energy calculation unit includes：
Transmitting coil voltage computation subunit, for calculating the voltage on transmitting coil；
Transmitting coil energy balane subelement, for calculating the emitted energy on transmitting coil；And
Transmitting coil energy loss calculation subelement, for calculating the off-energy on transmitting coil.
6. safety monitoring device according to claim 5, the accumulated energy computing unit includes：
Transmitting coil energy accumulation subelement, the emitted energy for unit of account time transmitting coil；
Transmitting coil energy loss adds up subelement, the off-energy for unit of account time transmitting coil；
Energy accumulation subelement is absorbed, is absorbed according to the emitted energy of transmitting coil and off-energy calculating patient's unit interval
SAR value.
7. safety monitoring device according to claim 6, the accumulated energy computing unit further includes：
Patient absorbs energy accumulation subelement, absorbs the cumulant of energy for calculating the patient, and be sent to system administration
Module.
8. safety monitoring device according to claim 6, the energy calculation unit further includes：
Maximum SAR value computing unit, is asked according to the first SAR sliding averages and the 2nd SAR sliding average result of calculations
Go out maximum first SAR sliding averages and maximum 2nd SAR sliding averages, and be sent to system management module.
9. safety monitoring device according to claim 6, the accumulated energy computing unit further includes：
Computation subunit is verified, the first SAR sliding averages and the 2nd SAR sliding averages are verified respectively, judges SAR
Whether value transfinites, if transfiniting, output transfinites signal to system management module.
10. according to claim 1 to 9 any one of them safety monitoring device, the PNS stimulates monitoring module to include：
Gradient stimulates PNS computing units, and the PNS values in X, Y, Z axis is calculated according to gradient signal；
PNS computing units, calculate the total values of three axis of three axis；
Maximum value calculation unit, calculates the maximum of total values；And
PNS verification units, verify the PNS values in the X, Y, Z axis and maximum.
11. safety monitoring device according to claim 10, the gradient stimulates PNS computing units to include：
Gradient change rate computation subunit, the gradient climb rate is calculated according to gradient data；
PNS computation subunits, the PNS values of tri- axis of X, Y, Z is calculated according to the gradient climb rate；And
PNS maximum value calculation subelements, calculate the single shaft maximum PNS values of tri- axis of X, Y, Z.
12. a kind of method for safety monitoring of MRI machine, including：
Gather RF signals and gradient signal；
SAR value is calculated according to the RF signals；
According to gradient signal calculate PNS values, including data synchronously input, gradient stimulate PNS calculate, maximum value calculation and
PNS is verified；
The signal an alert when the SAR value and PNS values exceed threshold value；
The SAR value includes the first SAR sliding averages and the 2nd SAR sliding averages,
When the first SAR sliding averages corresponding sampling time is longer than the 2nd SAR sliding averages corresponding sampling
Between；The first SAR sliding averages computation subunit and the 2nd SAR sliding average computation subunits are according to patient's unit
Time absorbs SAR value and calculates the first SAR sliding averages and the 2nd SAR sliding averages；
Calculating SAR value according to the RF signals includes：
According to the voltage on the voltage and transmitting coil on transmission line, the energy of each sample point is calculated；
According to the first SAR sliding averages of energy balane of the sample point and the 2nd SAR sliding averages, and calculate patient's suction
Receive the cumulative amount of energy.
13. method for safety monitoring according to claim 12, further includes：
The first SAR sliding averages are the first SAR sliding averages of local first SAR sliding averages and whole body；
The 2nd SAR sliding averages are the 2nd SAR sliding averages of local 2nd SAR sliding averages and whole body.
14. method for safety monitoring according to claim 12, further includes：
SAR value is calculated again after the RF signals are demodulated into base band small-signal.
15. method for safety monitoring according to claim 12, further includes：
Collection RF signals are carried out to calculate SAR value after disturbing in elimination signal, and/or, elimination letter is carried out to collection gradient signal
SAR value is calculated after being disturbed in number.
16. method for safety monitoring according to claim 12, calculating the energy of each sample point includes：
Calculate transmitting coil voltage；
The emitted energy of transmitting coil is calculated according to the transmitting coil voltage；
The parameter and transmitting coil voltage that are there is provided according to system calculate the off-energy on transmitting coil.
17. in method for safety monitoring according to claim 16, when multichannel is launched：
Calculate each channel emission coil voltage；
The emitted energy of each transmitting coil is calculated according to each channel emission coil voltage；
The parameter and each transmitting coil voltage that are there is provided according to system calculate the off-energy on each transmitting coil；
The emitted energy is the sum of emitted energy of each passage；And
The off-energy is the sum of off-energy of each passage.
18. method for safety monitoring according to claim 16, further includes：
The emitted energy of the transmitting coil of unit of account time；
The off-energy of the transmitting coil of unit of account time；
The SAR value absorbed according to the emitted energy of the transmitting coil and off-energy calculating patient's unit interval；
The first SAR sliding averages and the 2nd SAR sliding averages absorb SAR value meter according to patient's unit interval
Calculate.
19. method for safety monitoring according to claim 18, same in the SAR value that calculating patient's unit interval absorbs
When：
Patient is calculated to add up the energy of absorption, when the patient adds up the energy of absorption exceedes threshold value when send alarm.
20. method for safety monitoring according to claim 18, further includes：
By the maximum of the first SAR sliding averages and the 2nd SAR sliding averages, compared with threshold value, if exceeding threshold value
When send alarm.
It is 21. described that PNS stimulations are calculated according to gradient signal according to claim 12 to 20 any one of them method for safety monitoring
Value includes：
PNS values in X, Y, Z axis is calculated according to gradient signal；
Calculate the total values of three axis of three axis；
Calculate the maximum of total values；And
Value is swashed to the PNS in the X, Y, Z axis and maximum is verified.
22. method for safety monitoring according to claim 21, the PNS's carried out according to gradient signal in X, Y, Z axis
Calculating includes：
The gradient climb rate is calculated according to gradient data；
The PNS values of tri- axis of X, Y, Z is calculated according to the gradient climb rate；And
Calculate the single shaft maximum PNS values of tri- axis of X, Y, Z.
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