CN105411588A - Safety monitoring device and method for MRI equipment - Google Patents
Safety monitoring device and method for MRI equipment Download PDFInfo
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Abstract
The invention relates to a safety monitoring device and method for MRI equipment. The device comprises an RF signal input module, an SAR value monitoring module, a gradient signal input module, a PNS stimulation monitoring module and a system management module. The RF signal input module collects and inputs RF signals. The SAR value monitoring module receives the RF signals and calculates an SAR value. The gradient signal input module collects and inputs gradient signals. The PNS stimulation monitoring module receives the gradient signals, and calculates a PNS stimulation value. The system management module sends an alarming signal to an upper computer when the calculation result of the SAR value monitoring module and the PNS stimulation monitoring module exceeds a threshold value. The SAR value monitoring module comprises a first SAR sliding average value calculating sub-unit used for calculating a first SAR sliding average value, and a second SAR sliding average value calculating sub-unit used for calculating a second SAR sliding average value, and sampling time corresponding to the first SAR sliding average value is longer than that corresponding to the second SAR sliding average value.
Description
Technical field
The present invention relates to field of medical device, particularly the safety monitoring device of patient and method thereof in MR imaging apparatus.
Background technology
Nuclear magnetic resonance (hereinafter referred to as: MRI) in technology, along with the increase of magnetic resonance main field field intensity, the power of radio frequency excitation pulse (hereinafter referred to as RF pulse) is also along with increase, the energetic portions of RF pulse institute load discharges with form of heat, absorbed by human body, cause the rising of its body temperature.If do not controlled the heat of RF pulses generation, its heat produced can cause patient's topical burn, tachycardias, stupor even dead.Therefore, in the magnetic resonance equipment of high field intensity, in order to avoid causing the problems such as patient localized thermal damage, MRI scanning introduces a kind of protection concept completely newly, i.e. radio-frequency (RF) energy absorbance, radio-frequency (RF) energy absorbance (SpecificAbsorptionRate, hereinafter referred to as: SAR) be the radio-frequency (RF) energy that human body per weight absorbs within the unit interval, measurement unit is W/kg.The index of the tissue energy distribution that SAR value causes as assessment RF pulse, effectively can weigh RF pulse and rise the impact caused on body surface temperature, simultaneously the probability of pyrolytic damage that is subject to of reflection tissue.
Except the heat injury that the tissue caused except described RF pulse is subject to, in MRI equipment, the gradient fields of gradient coil switches fast human nerve tip also can be caused to inspire electric current, thus stimulate the peripheral nervous (PeripheralNervousSystem of human body, hereinafter referred to as: PNS) and muscle, special cardiac stimulus, can produce human body sensation of pricking.
At present for MRI product, the FDA (FoodandDrugAdministration: U.S. food Drug Administration) etc. of the U.S., defines safety index laws and regulations aspect.The difficult point of prior art is the accurate Calculation of how to carry out SAR value and PNS stimulus value.Because the mode calculated is varied, do not have unified method to follow, particularly 1.5T develops to 3T, causes magnetic field intensity more and more higher; And single channel launches development to multichannel, cause calculating to become increasingly complex, FDA etc. require more and more stricter to these aspects simultaneously, exacerbate the difficulty of theoretical research to clinical practice.
Summary of the invention
The present invention, in order to solve difficult point of the prior art, proposes and a kind ofly calculates the SAR value of different sampling stages and the real time and on line monitoring system of PNS stimulus value.
For solving the problem, the invention provides a kind of safety monitoring device of MRI equipment, comprising:
RF signal input module, gathers and input rf signal;
SAR value monitoring module, receives described RF signal, calculates SAR value;
Gradient signal input module, gathers and input gradient signal;
PNS stimulates monitoring module, receives described gradient signal, calculates PNS stimulus value;
System management module, gives the alarm signal to host computer when described SAR value monitoring module and PNS stimulate the result of calculation of monitoring module to exceed threshold value;
Wherein, described SAR value monitoring module, comprising:
One SAR sliding average computation subunit, for calculating a SAR sliding average;
2nd SAR sliding average computation subunit, for calculating the 2nd SAR sliding average,
The sampling time that a described SAR sliding average is corresponding is longer than sampling time corresponding to described 2nd SAR sliding average
Optionally, a described SAR sliding average computation subunit and the 2nd SAR sliding average computation subunit comprise respectively:
Whole body SAR value computer, for calculating whole body SAR sliding average, and
Local SAR value computer, for calculating local SAR sliding average.
Optionally, described safety monitoring device, also comprises:
RF signal receiving is send to SAR value monitoring module after base band small-signal by demodulation module.
Optionally, described safety monitoring device, also comprises:
Light mouth module, receives RF signal, eliminates the interference in described RF signal, and send to SAR value monitoring module, and/or, receive gradient signal, eliminate the interference in described gradient signal, and send to PNS to stimulate monitoring module.
Optionally, described SAR value monitoring module also comprises:
Sample point energy calculation unit, according to the voltage on transmission line and the voltage on transmitting coil, calculates the energy of each sample point;
Accumulated energy computing unit, comprises a described SAR sliding average computation subunit and the 2nd SAR sliding average computation subunit, and calculates the endergonic cumulant of patient.
Optionally, described sample point energy calculation unit comprises:
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, described accumulated energy computing unit comprises:
Transmitting coil energy accumulation subelement, the transmitting coil emitted energy of unit of account time;
Transmitting coil energy loss adds up the off-energy of subelement, unit of account time transmitting coil;
Absorb energy accumulation subelement, calculate patient's unit interval according to the emitted energy of transmitting coil and off-energy and absorb SAR value;
A described SAR sliding average computation subunit and the 2nd SAR sliding average computation subunit absorb SAR value according to described patient's unit interval to calculate a SAR sliding average and the 2nd SAR sliding average.
Optionally, described accumulated energy computing unit also comprises:
Patient absorbs energy accumulation subelement, for calculating the endergonic accumulation of described patient, and sends to system management module.
Optionally, described accumulated energy computing unit also comprises:
Maximum SAR value computing unit, obtains a maximum SAR sliding average and maximum 2nd SAR sliding average according to a described SAR sliding average and the 2nd SAR sliding average result of calculation, and sends to system management module.
Optionally, described accumulated energy computing unit also comprises:
Verify calculation subelement, verifies a SAR sliding average and the 2nd SAR sliding average respectively, judges whether SAR value transfinites, if transfinite, then the defeated signal that transfinites is to system management module.
Optionally, described PNS stimulates monitoring module to comprise:
Gradient stimulates PNS computing unit, calculates the PNS stimulus value in X, Y, Z axis according to gradient signal;
PNS computing unit, calculates the total stimulus value of three axles of three axles;
Maximum value calculation unit, calculates the maximum of described total stimulus value; And
PNS verification unit, verifies according to the PNS stimulus value in X, Y, Z axis and maximum.
Optionally, described gradient stimulates PNS computing unit to comprise:
Gradient change rate computation subunit, calculates the gradient climb rate according to gradient data;
PNS computation subunit, calculates X, Y, Z tri-PNS stimulus value of axle according to the described gradient climb rate; And
PNS maximum value calculation subelement, calculates X, Y, Z tri-maximum PNS stimulus value of single shaft of axle.
The present invention also provides a kind of method for safety monitoring of MRI equipment, comprising:
Gather RF signal and gradient signal;
SAR value is calculated according to described RF signal;
PNS stimulus value is calculated according to carrying signal;
Give the alarm when described SAR value and PNS stimulus value exceed threshold value signal;
Described SAR value comprises a SAR sliding average and the 2nd SAR sliding average,
The sampling time that a described SAR sliding average is corresponding is longer than sampling time corresponding to described 2nd SAR sliding average.
Optional:
A described SAR sliding average is local the one SAR sliding average and whole body the one SAR sliding average;
Described 2nd SAR sliding average is local the 2nd SAR sliding average and whole body the 2nd SAR sliding average.
Optionally, described method for safety monitoring, also comprises:
Be calculate SAR value again after base band small-signal by RF signal receiving.
Optionally, described method for safety monitoring, also comprises:
Carry out calculating SAR value after interference in erasure signal to collection RF signal, and/or, carry out calculating SAR value after interference in erasure signal to collection gradient signal.
Optionally, calculate SAR value according to described RF signal to comprise:
According to the voltage on transmission line and the voltage on transmitting coil, calculate the energy of each sample point;
According to described sample point energy balane the one SAR sliding average and the 2nd SAR sliding average, and calculate the endergonic cumulative amount of patient.
Optionally, each sample point energy of described calculating comprises:
Calculate transmitting coil voltage;
The emitted energy of transmitting coil is calculated according to described transmitting coil voltage;
The parameter provided according to system and transmitting coil voltage 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 described each channel emission coil voltage;
The parameter provided according to system and described each transmitting coil voltage calculate the off-energy on each transmitting coil;
Described emitted energy is the emitted energy sum of each passage; And
Described off-energy is the off-energy sum of each passage.
Optionally, described method for safety monitoring, also comprises
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 that patient's unit interval absorbs is calculated according to the emitted energy of described transmitting coil and off-energy
A described SAR sliding average and the 2nd SAR slip sliding average absorb SAR value according to described patient's unit interval and calculate
Described method for safety monitoring, be also included in calculate described patient's unit interval absorbs SAR value while:
Calculate patient add up absorb energy, when described patient add up absorb energy exceed threshold value time give the alarm.
Optionally, described method for safety monitoring, also comprises:
One SAR sliding average and the 2nd SAR sliding average and threshold value are compared, if give the alarm when exceeding threshold value.
Optionally, describedly calculate PNS stimulus value according to gradient signal and comprise:
The PNS stimulus value in X, Y, Z axis is calculated according to gradient signal;
Calculate the total stimulus value of three axles of described three axles;
Calculate the maximum value calculation maximum of described total stimulus value; And
PNS stimulus value in described X, Y, Z axis and maximum are verified.
Optionally, the calculating of the described PNS carried out in X, Y, Z axis according to gradient signal comprises:
The gradient climb rate is calculated according to gradient data;
X, Y, Z tri-PNS stimulus value of axle is calculated according to the described gradient climb rate; And
Calculate X, Y, Z tri-maximum PNS stimulus value of single shaft of axle.
Compared with prior art, the present invention propose a kind of long to whole body time (FullBodyLongtime) SAR value (being 360 seconds time long); Whole body is (FullBodyShorttime) SAR value (being 10 seconds in short-term) in short-term; (PartBodyLongtime) SAR value when local is long; Local is the method simultaneously monitored of (PartBodyShowtime) SAR value four kinds of modes in short-term, more fully ensures the accuracy monitored.This safety monitoring system can not only be real-time calculate actual SAR and PNS stimulus value, simultaneously can do consistency desired result with theoretical SAR and the PNS stimulus value of expection, prevent the value difference of SAR and the PNS stimulus value of patient's actual absorption in MRI equipment and expection not excessive cause to monitor slip up and the patient that causes is subject to Shanghai.And propose when SAR or PNS stimulus value reaches certain threshold value in the present invention, MRI stops scanning automatically, stops certain hour, and when the fault offset locally absorbed is in safety range, MRI restarts.Ensure the safety of patient in scanning process.
Accompanying drawing explanation
Fig. 1 is the security monitoring portion structural representation according to MRI equipment of the present invention;
Fig. 2 is the structural representation according to SAR value monitoring module of the present invention;
Fig. 3 is the structural representation according to sample point energy calculation unit of the present invention;
Fig. 4 is the structural representation according to accumulated energy computing unit of the present invention;
Fig. 5 is the structural representation stimulating monitoring module according to PNS of the present invention;
Fig. 6 is the structural representation according to PNS computing unit of the present invention.
Detailed description of the invention
For enabling above-mentioned purpose of the present invention, feature and advantage more become apparent, and are described in detail the specific embodiment of the present invention below in conjunction with accompanying drawing.Set forth detail in the following description so that fully understand the present invention.But the present invention can be different from alternate manner described here to implement with multiple, those skilled in the art can when without prejudice to doing similar popularization when intension of the present invention.Therefore the present invention is not by the restriction of following public detailed description of the invention.
Fig. 1 is a kind of structural representation of the security monitoring portion about MRI equipment.The security monitoring portion of MRI equipment comprises: RF control inputs module 1, to energy datum, pulse switch and sequence switch data etc. that light mouth module 4 input system issues; RF signal input module 2, gathers RF signal, and described RF signal is sent to light mouth module 4; Gradient signal input module 3, gathers gradient signal, and described gradient signal is sent to light mouth module 4; Clock module 13, input clock signal, makes modules calculate data syn-chronization; Light mouth module 4, receives the interface of data, and capacity of resisting disturbance is strong, optionally eliminates the interference in Received signal strength; Demodulation module 5, sends SAR value monitoring module 6 to by after the RF signal decoding of light mouth module 4; SAR value monitoring module 6, calculates SAR value according to the RF signal after the demodulation of input; Gradient optical module (not shown), is integrated in light mouth module 4, and sending PNS to after being decoded by gradient signal stimulates monitoring module 7; PNS stimulates monitoring module 7, carries out the calculating of PNS stimulus value according to the decoded gradient signal of gradient optical module transmission; SAR value monitoring module 6 and PNS stimulate monitoring module 7 that result is reported system management module 10; System management module 10, stimulates the result of calculation of monitoring module 7 to manage to SAR value monitoring module 6 and PNS; Register mappings module 8, for the calculating parameter that register system provides, and when calculating for each module, because each parameter has a register address, can read and write corresponding parameter according to address; Host computer interface module 12 is PCIe module: host computer can read monitor data by slot; Program online updating module 9: for upgrading the logical order in security monitoring portion, provide online updating function, avoids equipment of taking apart to go to upgrade the program in hardware circuit board; Acquisition control module 11, collection primary RF signals real-time during for scanning, SAR value monitoring module 6 and PNS stimulate the result of calculation of monitoring module 7, and send to host computer, verify its result of calculation for host computer.Described host computer is the overall system control of MRI equipment, comprises the man machine interface display system for showing various parameter.
Below the monitor procedure in above-mentioned security monitoring portion is described.RF signal, gradient signal, control signal and the clock signal in MR system imaging process is obtained by RF control inputs module 1, clock module 13, RF signal input module 2 and gradient signal input module 3; Denoising is carried out to the described various signal obtained; Demodulation is carried out to RF signal, the modulating wave that collection is come in is demodulated to baseband signal, and (what collection came in is modulating wave, need to carry out signal receiving to this modulating wave, demodulation baseband signal is out only the real primary signal needed), and calculated the SAR value of human body according to the parameter that RF signal and system provide by SAR value monitoring module 6; Meanwhile, carried out the monitoring of human body PNS stimulus value according to the parameter that gradient signal and system provide by PNS stimulation monitoring module 7; Finally managed by the PNS stimulus value of system management module 10 to the SAR value of described human body and human body and reported in host computer.System management module 10 mainly management is mutual with host computer, performs and reports overload alarm (SAR value, PNS stimulus value) and remove overload alarm.System management module 10 is interrupt management functional modules, if multiple monitored results all transfinites, needs system management module 10 to determine processing sequence.The management personnel of upper computer end judge whether to proceed scanning according to the SAR value fed back in described process and PNS stimulus value.Describedly report in host computer process, host computer can be sent in by alert methods when SAR value and PNS stimulus value exceed certain threshold value, be convenient to the attention causing management personnel.
SAR value monitoring module 6 and PNS stimulation monitoring module 7 are the core calculations modules in security monitoring portion.Below with reference to the accompanying drawings 2 to 6, stimulate monitoring module 7 to be described in detail to SAR value monitoring module 6 and PNS.
Fig. 2 is the structural representation according to SAR value monitoring module 6 of the present invention.SAR value monitoring module 6 is primarily of data synchronisation unit 61, and come synchronously to calculate for the RF signal of cross clock domain is synchronized to PCIe clock zone, described RF signal is provided by demodulation module 5; Parameter pretreatment unit 62, anticipate the systematic parameter participating in SAR value calculating, described systematic parameter is provided by register mappings module 8; Sample point energy calculation unit 63, according to the voltage on transmission line and the voltage on transmitting coil, calculates the energy of each sample point; Consistency desired result unit 64, during for calculating RF sequence transmission energy whether with expection emitted energy consistent (expecting that emitted energy is that system issues), in order to the error of check system energy; Accumulated energy computing unit 65, for calculating the SAR value that human body adds up to absorb, hardware on-line monitoring unit 66: the voltage on the transmission line that sample point energy calculation unit 63 calculated and transmitting coil is monitored, and judges whether maximum voltage transfinites.
Below the SAR value computational process of SAR value monitoring module 6 is described.First, the RF signal after the demodulation send demodulation module 5 is synchronized to PCIe clock zone and synchronously calculates, and cross clock domain process is accelerated to calculate under from 10Mhz data rate synchronous to 125Mhz clock, simultaneously, pretreatment is carried out to parameter required in calculating, described parameter comprises, power and frequency calibration parameter, rate of energy loss parameter, also has the threshold parameter such as voltage threshold of some monitoring, SAR thresholding, tolerance etc., described pretreatment comprises, as floating number and fixed-point number are changed, parameter merges simplification in advance and calculates, differentiating of some parameters, also comprise the transmission coefficient calculating transmission line, the transmission coefficient of sample time and transmitting coil, these parameters are that system calibration measurement gets, during start, system can be calibrated, during scanning, system can issue these parameters, obtained by register mappings module 8, according to described synchronous after RF signal and pretreatment system parameter, calculate the energy of each sample point, the accumulated energy at different time and position is calculated again according to the energy of described sample point, whether verified with the consistent error to system capacity of expection emitted energy by energy during RF sequence transmission simultaneously, and the voltage on transmission line and transmitting coil is monitored, if voltage transfinites, turn off radio-frequency power amplifier, stop scanning, host computer showing voltage transfinites and reports to the police.
Fig. 3 is according to sample point energy calculation unit structural representation of the present invention.Sample point (RF signal values collected) energy calculation unit 63 major function calculates the voltage on the energy of each sample point, transmission line and the voltage on transmitting coil.As shown in the figure, it comprises: S parameter computation subunit 630: calculate S11, S12, S21, S22 tetra-parameters (described coefficient and parameter are that system calibration gets) respectively according to forward direction (FWR) and reverse (REF) rf data and transmission line coefficient (Tcable) and coil factor (Tcoil), result is sent to transmitting coil voltage computation subunit 631 and transmission-line voltage computation subunit 632 simultaneously; 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 the energy that the transmitting coil voltage calculating sampling time calculated is corresponding; Transmitting coil energy loss calculation subelement 634, calculates the energy of transmitting coil loss according to the transmitting coil voltage calculated and loss rate; Result of calculation synchronism output subelement 635, snaps to same rising edge clock and exports by all result of calculation.
Below the computational process of sample point energy calculation unit 63 is described: obtain forward direction (FWR) in RF signal and reverse (REF) rf data and transmission line coefficient (Tcable) and coil factor (Tcoil); (S parameter is the theory in microwave transmission equation to calculate S11, S12, S21, S22 tetra-parameters according to described data, it is 2 × 2 matrix, be made up of S11, S12, S21, S22 tetra-elements, this parameter in magnetic resonance system is calculated as prior art, does not repeat them here); Calculate coil voltage and transmission-line voltage according to described parameter, when the dual pathways is launched, need to calculate respectively voltage and transmitting coil voltage on the transmission line on first passage and second channel; Then, according to sampling time of transmitting coil and the transmitting coil voltage that calculated, just transmitting power can be calculated; Afterwards, then calculate emitted energy and the off-energy of transmitting coil according to the transmitting power of coil and sampling time, when being corrected by system, calculate rate of energy loss parameter; When multichannel is launched, need the loss rate calculating each channel energy respectively, then the energy of each pass loss is added and just obtains the total energy loss of transmitting coil; Finally simultaneously operating is carried out to result of calculation, synchronously to solve cross clock domain problem, input data from transmitting coil energy balane subelement 633 and transmitting coil energy loss calculation subelement 634 are asynchronous, export so need to be synchronized to 125Mhz by result of calculation synchronism output subelement 635 simultaneously.
Fig. 4 is the structural representation according to accumulated energy computing unit of the present invention.As shown in the figure, accumulated energy computing unit 65 comprises: time counting subelement 651, timing from during patient's new registration; Time signal is exported to transmitting coil energy accumulation subelement 652 and transmitting coil energy loss to add up subelement 653 simultaneously; Transmitting coil energy accumulation subelement 652 and transmitting coil energy loss add up subelement 653 according to the emitted energy of time cumulative unit interval (as 1 second) and off-energy, finally export to and absorb energy balane subelement 654; Absorb energy balane subelement 654, the energy that calculating patient's unit interval (as 1 second) absorbs; Patient absorbs energy accumulation subelement 655, the energy of the absorption that adds up according to unit interval absorption energy balane patient; SAR sliding average computation subunit 656 and SAR sliding average computation subunit 657 in short-term time long, absorb the SAR sliding average of (as 360S) when energy first calculates long respectively and (as 10S) in short-term according to patient's unit interval, with SAR sliding average computation subunit 656 during duration and in short-term SAR sliding average computation subunit 657 SAR value calculated exported to maximum SAR value send subelement 658; Maximum SAR value sends subelement 658, according to above-mentioned result of calculation obtain greatly enhance most time SAR sliding average and greatly enhance most time SAR sliding average send to system management module 10, verify calculation subelement 659, SAR value to be verified, judge whether SAR value transfinites, if transfinited, then export high level useful signal (overlimit) and send to system management module 10.
Below the computational process of the accumulated energy computing unit 65 in SAR value monitoring module 6 is described.When new patient registers, system will produce system reset (Warm_reset) signal, time counting subelement 651 starts the timing of a second a second, the transmitting coil energy calculated by above-mentioned sample point energy calculation unit and transmitting coil off-energy carry out temporal cumulative, and cumulative transmitting coil energy and off-energy are sent to absorption energy balane subelement 654, calculate the energy of human body unit interval absorption, the unit interval absorbs energy equivalence and deducts unit interval received energy and unit interval off-energy in unit interval emitted energy; SAR sliding average and SAR sliding average is in short-term absorbed when energy calculates long respectively again according to described unit interval, described two meansigma methodss can be divided into whole body SAR meansigma methods and local SAR meansigma methods again respectively, the i.e. average power of every 10 seconds or 360 seconds, is multiplied these energy and body part factor local factors (partbodyfactor) with the whole body factor (fullbodyfactor) simultaneously and obtains the SAR value of corresponding site; Finally described SAR value is verified, send when finding that there is and transfiniting the signal that transfinites.
Fig. 5 is the structural representation stimulating monitoring module according to PNS of the present invention.As shown in the figure, PNS stimulates monitoring module 7 to comprise: data syn-chronization input block 71, receives gradient signal, the gradient data of the X, Y, Z axis in gradient signal and systematic parameter is carried out to the synchronous process of cross clock domain; Gradient stimulates PNS computing unit 72, carries out the calculating of PNS, send result of calculation to maximum value calculation unit 74 simultaneously according to above-mentioned synchrodata; Maximum value calculation unit 74, the PNS result of calculation according to three axles draws total stimulus value, and obtains the maximum of the total stimulus value of three axles, and sends to PNS verification unit 75; PNS verification unit 75, to the total stimulus value of three axles, and the total irritation level maximum (PNS_totalmax) of three axles carries out implementing monitoring and consistency desired result.
The monitor procedure of monitoring module 7 is stimulated to be described to PNS below.First synchronously process according to the gradient signal inputted and systematic parameter, calculate the PNS of X-axis (PNS_core_X), Y-axis (PNS_core_Y), Z axis (PNS_core_Z) respectively, the PNS stimulus value computational methods of three axles are consistent; PNS computing unit 73, PNS_X, PNS_Y, PNS_Z of calculating are carried out suing for peace and obtains the total stimulus value of three axle (PNS_total) of three axles, then maximum value calculation and consistency desired result are carried out to described total stimulus value, consistency desired result allows the PNS stimulus value of Practical Calculation compare with desired value, determine whether in range of tolerable variance, stablize with decision-making system and whether normally calculate, if through verification, if transfinited, then report the value that transfinites (overlimit).
Fig. 6 is the structural representation stimulating PNS computing unit according to gradient of the present invention.As shown in the figure, PNS computing unit 72 comprises: gradient change rate computation subunit 721, calculates the gradient climb rate according to gradient signal; Gradient stimulates effective time count sub-element 722, stimulates effective time to carry out timing to gradient; Gradient stimulates limit value computation subunit 723, calculates the limit value of PNS in real time, send result to PNS computation subunit 724 simultaneously according to described timing result and the gradient climb rate; PNS computation subunit 724, calculates X, Y, Z tri-PNS of axle according to described PNS limit value; PNS maximum value calculation subelement 725, for calculating and exporting X, Y, Z tri-PNS maximum of axle.
Stimulating during PNS computing unit 72 below in conjunction with gradient stimulates the monitor procedure of monitoring module to be described.First the gradient climb rate is calculated according to gradient data, then the gradient climb rate and the threshold value that set are compared, if when judging that the climb rate is greater than threshold value, start the stimulation monitoring of PNS, described threshold value is issued by system, is used for doing the Rule of judgment that PNS monitors opening switch; Effective time and the gradient climb rate is stimulated to calculate the limit value of PNS according to gradient again, PNS computation subunit 724, for calculating X, Y, Z tri-PNS of axle, PNS=deltaG/Limit, wherein Limit is the PNS limit value that previous step calculates, and deltaG is gradient change rate; Finally calculate and export X, Y, Z tri-single shaft PNS maximum of axle.
Although the present invention with preferred embodiment openly as above; but it is not for limiting the present invention; any those skilled in the art without departing from the spirit and scope of the present invention; the Method and Technology content of above-mentioned announcement can be utilized to make possible variation and amendment to technical solution of the present invention; therefore; every content not departing from technical solution of the present invention; the any simple modification done above embodiment according to technical spirit of the present invention, equivalent variations and modification, all belong to the protection domain of technical solution of the present invention.
Claims (24)
1. a safety monitoring device for MRI equipment, comprising:
RF signal input module, gathers and input rf signal;
SAR value monitoring module, receives described RF signal, calculates SAR value;
Gradient signal input module, gathers and input gradient signal;
PNS stimulates monitoring module, receives described gradient signal, calculates PNS stimulus value;
System management module, gives the alarm signal to host computer when described SAR value monitoring module and PNS stimulate the result of calculation of monitoring module to exceed threshold value;
Wherein, described SAR value monitoring module, comprising:
One SAR sliding average computation subunit, for calculating a SAR sliding average;
2nd SAR sliding average computation subunit, for calculating the 2nd SAR sliding average,
The sampling time that a described SAR sliding average is corresponding is longer than sampling time corresponding to described 2nd SAR sliding average.
2. safety monitoring device according to claim 1, a described SAR sliding average computation subunit and the 2nd SAR sliding average computation subunit comprise respectively:
Whole body SAR value computer, for calculating whole body SAR sliding average, and
Local SAR value computer, for calculating local SAR sliding average.
3. safety monitoring device according to claim 1, also comprises:
RF signal receiving is send to SAR value monitoring module after base band small-signal by demodulation module.
4. safety monitoring device according to claim 1, also comprises:
Light mouth module, receives RF signal, eliminates the interference in described RF signal, and send to SAR value monitoring module, and/or, receive gradient signal, eliminate the interference in described gradient signal, and send to PNS to stimulate monitoring module.
5. safety monitoring device according to claim 2, described SAR value monitoring module also comprises:
Sample point energy calculation unit, according to the voltage on transmission line and the voltage on transmitting coil, calculates the energy of each sample point;
Accumulated energy computing unit, comprises a described SAR sliding average computation subunit and the 2nd SAR sliding average computation subunit, and calculates the endergonic cumulant of patient.
6. safety monitoring device according to claim 5, described sample point energy calculation unit comprises:
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.
7. safety monitoring device according to claim 6, described accumulated energy computing unit comprises:
Transmitting coil energy accumulation subelement, for the emitted energy of unit of account time transmitting coil;
Transmitting coil energy loss adds up subelement, for the off-energy of unit of account time transmitting coil;
Absorb energy accumulation subelement, calculate patient's unit interval according to the emitted energy of transmitting coil and off-energy and absorb SAR value;
A described SAR sliding average computation subunit and the 2nd SAR sliding average computation subunit absorb SAR value according to described patient's unit interval to calculate a SAR sliding average and the 2nd SAR sliding average.
8. safety monitoring device according to claim 7, described accumulated energy computing unit also comprises:
Patient absorbs energy accumulation subelement, for calculating the endergonic cumulant of described patient, and sends to system management module.
9. safety monitoring device according to claim 7, described energy calculation unit also comprises:
Maximum SAR value computing unit, obtains a maximum SAR sliding average and maximum 2nd SAR sliding average according to a described SAR sliding average and the 2nd SAR sliding average result of calculation, and sends to system management module.
10. safety monitoring device according to claim 7, described accumulated energy computing unit also comprises:
Verify calculation subelement, verifies a SAR sliding average and the 2nd SAR sliding average respectively, judges whether SAR value transfinites, if transfinite, then exports and transfinites signal to system management module.
11. safety monitoring devices according to any one of claim 1 to 10, described PNS stimulates monitoring module to comprise:
Gradient stimulates PNS computing unit, calculates the PNS stimulus value in X, Y, Z axis according to gradient signal;
PNS computing unit, calculates the total stimulus value of three axles of described three axles;
Maximum value calculation unit, calculates the maximum of described total stimulus value; And
PNS verification unit, verifies the PNS stimulus value in described X, Y, Z axis and maximum.
12. safety monitoring devices according to claim 11, described gradient stimulates PNS computing unit to comprise:
Gradient change rate computation subunit, calculates the gradient climb rate according to gradient data;
PNS computation subunit, calculates X, Y, Z tri-PNS stimulus value of axle according to the described gradient climb rate; And
PNS maximum value calculation subelement, calculates X, Y, Z tri-maximum PNS stimulus value of single shaft of axle.
The method for safety monitoring of 13. 1 kinds of MRI equipment, comprising:
Gather RF signal and gradient signal;
SAR value is calculated according to described RF signal;
PNS stimulus value is calculated according to gradient signal;
Give the alarm when described SAR value and PNS stimulus value exceed threshold value signal;
Described SAR value comprises a SAR sliding average and the 2nd SAR sliding average,
The sampling time that a described SAR sliding average is corresponding is longer than sampling time corresponding to described 2nd SAR sliding average.
14. method for safety monitoring according to claim 13, also comprise:
A described SAR sliding average is local the one SAR sliding average and whole body the one SAR sliding average;
Described 2nd SAR sliding average is local the 2nd SAR sliding average and whole body the 2nd SAR sliding average.
15. method for safety monitoring according to claim 13, also comprise:
Be calculate SAR value again after base band small-signal by described RF signal receiving.
16. method for safety monitoring according to claim 13, also comprise:
Carry out calculating SAR value after interference in erasure signal to collection RF signal, and/or, carry out calculating SAR value after interference in erasure signal to collection gradient signal.
17. method for safety monitoring according to claim 13, calculate SAR value according to described RF signal and comprise:
According to the voltage on transmission line and the voltage on transmitting coil, calculate the energy of each sample point;
According to energy balane the one SAR sliding average and the 2nd SAR sliding average of described sample point, and calculate the endergonic cumulative amount of patient.
18. method for safety monitoring according to claim 17, the energy calculating each sample point comprises:
Calculate transmitting coil voltage;
The emitted energy of transmitting coil is calculated according to described transmitting coil voltage;
The parameter provided according to system and transmitting coil voltage calculate the off-energy on transmitting coil.
In 19. method for safety monitoring according to claim 18, when multichannel is launched:
Calculate each channel emission coil voltage;
The emitted energy of each transmitting coil is calculated according to described each channel emission coil voltage;
The parameter provided according to system and described each transmitting coil voltage calculate the off-energy on each transmitting coil;
Described emitted energy is the emitted energy sum of each passage; And
Described off-energy is the off-energy sum of each passage.
20. method for safety monitoring according to claim 18, also comprise:
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 that patient's unit interval absorbs is calculated according to the emitted energy of described transmitting coil and off-energy;
A described SAR sliding average and the 2nd SAR sliding average absorb SAR value according to described patient's unit interval and calculate.
21. method for safety monitoring according to claim 20, described calculating patient's unit interval absorbs SAR value while:
Calculate patient add up absorb energy, when described patient add up absorb energy exceed threshold value time give the alarm.
22. method for safety monitoring according to claim 20, also comprise:
By the maximum of a SAR sliding average and the 2nd SAR sliding average, compare with threshold value, if give the alarm when exceeding threshold value.
23. according to claim 13 to the method for safety monitoring described in 23 any one, describedly calculates PNS stimulus value according to gradient signal and comprises:
The PNS stimulus value in X, Y, Z axis is calculated according to gradient signal;
Calculate the total stimulus value of three axles of described three axles;
Calculate the maximum of described total stimulus value; And
The sharp value of PNS in described X, Y, Z axis and maximum are verified.
24. method for safety monitoring according to claim 24, the calculating of the described PNS carried out in X, Y, Z axis according to gradient signal comprises:
The gradient climb rate is calculated according to gradient data;
X, Y, Z tri-PNS stimulus value of axle is calculated according to the described gradient climb rate; And
Calculate X, Y, Z tri-maximum PNS stimulus value of single shaft of axle.
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