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MRI safety and health issuesprof. Yves De DeeneRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYBasic components of an MRI scannerCRYOGENICMAGNETGRADIENTCOILSSCANNERBORERx / Tx COILPATIENT TABLECACHE OF FARADAYYves De DeeneMRI safety and health issues1
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSIn the human environment5 mT50 µT0.1 – 0.2 T0.3 T – 3 TMRI safety and health issues: Static magnetic fieldsYves De DeeneRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSNMR spectrometers600 MHz spectrometer15 TProtein synthesis900 MHz spectrometerNMR spectrumYves De Deene22.5 TMRI safety and health issues: Static magnetic fields2
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSCERN: Compact Muon Solenoid (CMS) detector @ LHCCryogenic magnetMass:12500 TDiameter:15 mLength:21.4 mField strength:4TCurrent:19500 AStored energy: 2.66 GJMRI safety and health issues: Static magnetic fieldsYves De DeeneRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSForce on a charged particlein a homogeneous field Lorentz force: F FeForce on a magnetizable objectin an inhomogeneous field Fm Fe q E Magnetic force: Fm q (v B)Electric force:FmBv FNo magnetic energy transfer to objectYves De Deene M BMotion required0 H H MV0 B BrMoleculesCellsTissuesMRI safety and health issues: Static magnetic fields3
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSPotential interactions with human tissueSusceptibility induced molecular orientationmoleculeMagnetic energy:U1 V M B02For water molecules, the asymmetryin susceptibility is about one percentof the value of -9.05 10-61V B022 01cos222sin2TorqueB0Torque:TUV B02(21) sin cos0Yves De DeeneVNo significant effects have beenobserved for small molecules. Forlarger molecules diamagneticanisotropy effects have beenobserved in vitro.MRI safety and health issues: Static magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSPotential interactions with human tissueSusceptibility induced molecular orientationRhodopsinRetinaYves De DeeneHuman rod cellMRI safety and health issues: Static magnetic fields4
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSPotential interactions with human tissueSusceptibility induced molecular orientationerythrocyte12TorqueNo magnetic fieldYves De DeeneB0In a magnetic field of 8 TMRI safety and health issues: Static magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSPotential interactions with human tissueSusceptibility induced molecular orientationIncreased coagulation Observed change in blood viscosity Depends on oxygenation level: minimum viscosity at 85 % oxygenation Related to increased surface area of adjacent cells Increase in fibrin polymerizationYves De DeeneMRI safety and health issues: Static magnetic fields5
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSPotential interactions with human tissueSusceptibility induced molecular translationin a magnetic field gradientFmFgplasmaB1B0 0gz0eryplasmaeryplasmaLowmagnetic fieldIn a 4T MRI scanner :eryB0B0zFmB0zFmFgHighmagnetic fieldFgzB08 .8 T 2 / m0.027Compensated by hemodynamic forcesYves De DeeneMRI safety and health issues: Static magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSPotential interactions with human tissueMagnetic effects on chemical reactionsNo magnetic fieldFeMagnetic fieldABA BElectron spin(magnetic moment)DissociationBoundoxygenoxygenheemStrong magnetic fieldABOxy-hemoglobine(diamagnetic)Negligible effectYves De DeeneA BDeoxy-hemoglobine O2(paramagnetic)No observable effects in biochemical reactionsMRI safety and health issues: Static magnetic fields6
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSMagnetohydrodynamic effect Fm vCharge displacement due to FmB0jq FmElectric potential at the aortic wallV q (v B)Displacement due to Fmcreates another forcewhich is opposed to theoriginal displacementHaemoglobine(Fe)Yves De Deenev BdTNegligible effect on bloodflow/pressure for fields B 10 TEnhancement of T-waveMRI safety and health issues: Static magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSMagnetohydrodynamic effectObservations in high magnetic fields ( 3T) In some patients Vertigo Reversible B F q.(v B) vExplanationMagnetohydrodynamic (MHD) effect investibular organ causes discordancewith visual sensation.Yves De DeeneMRI safety and health issues: Static magnetic fields7
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSIn vitro experimentsTeratogenic, reproductive and mutagenic effects No effect observed after exposure of human fetusesat 1.5 T in third trimester of pregnancy. No teratogenic effect was found in Xenopus Laevis(frogs) upon exposure to a magnetic field of 8 T for 20hours. No mutagenic effect observed in bacteria afterexposure to static magnetic field up to 5 T.Eukariotic cytoskeletanRed: Actin filamentsGreen: microtubulusBlue: nucleiYves De DeeneMRI safety and health issues: Static magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSSome other observationsMigration of leucocytes in an ultra strong magnetic fieldgradient (60 T/m)Small deformation of erythrocytes when exposed at 0.5 Tfor more than 4 hoursReversibleYves De DeeneMRI safety and health issues: Static magnetic fields8
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSMRI safety and health issues: Static magnetic fieldsYves De DeeneRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSOfficial regulationsFood and Drug Administration (FDA) (July 14, 2003)Adults and children older than 1 month:8TBaby’s younger than 1 month:4TInternational Electro-technical Commission (IEC 60601-2-33)No limitsInternational Commission onNonionizing Radiation Protection(ICNIRP)Physical Agents Directive (E.U.)All patients:2TPersonnel:0.2 TUnder discussion in European CommissionYves De DeeneMRI safety and health issues: Static magnetic fields9
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYYves De DeeneMRI safety and health issues: Static magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSProjectile effectYves De DeeneMRI safety and health issues: Static magnetic fields10
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSProjectile effect1 pound 4.4 NYves De DeeneMRI safety and health issues: Static magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSFIELDSTRENGTHYves De DeeneEQUIPMENT10 mTWatches, creditcards, .5 mTOperator console, magnetic recordingmedia, electrical motors, computers, .1 mTVideo cameras and monitors, .0.5 mTCardiac pacemakers, hearingapparatus, metal detectors, imagieamplifiers,.0.1 mTGamma cameras, electronmicroscopes, CT scanners, PETscanners, .MRI safety and health issues: Static magnetic fields11
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSPassive implantsYves De DeeneMRI safety and health issues: Static magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSActive implantsDrug release systemPacemakerYves De DeeneVagal nerve stimulator(anti-epileptic)MRI safety and health issues: Static magnetic fields12
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSSusceptibility artifactsSusceptibility artifactfrom screwSusceptibility artifact from dentalimplant (SAG en TRA)zYves De DeeneB0GzSusceptibility artifact from Titanium bar(experimental) (SE-image)MRI safety and health issues: Static magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSSusceptibility artifacts caused by cosmeticsPiercingsCosmeticsYves De DeeneMRI safety and health issues: Static magnetic fields13
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGY B0 H MSTATIC MAGNETIC FIELDSClassification of materials M HMR incompatible materials: Experience a mechanical force in a magnetic fieldM0102e.g. Ferrous, steel, nickel, cobaltMR compatible materials:First kind:Do not experience a mechanical force in a magnetic fieldCause severe imaging artifacts105water102e.g. Titanium, bismuth, non-magn. steel, CarbonSecond kind:Do not cause severe imaging artifactswater105e.g. Water, human tissue, copper, zincYves De DeeneMRI safety and health issues: Static magnetic fieldsPATIËNT VEILGHEIDSFORMULIERRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSYves De DeeneMRI safety and health issues: Static magnetic fields14
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYSTATIC MAGNETIC FIELDSQuenchSuperconducting magnetHelium, Nitrogen cooled 1200 ALeakage in cryogen tankLoss of superconductivityHeating of magnetPressure increase in cryogen tankYves De DeeneQUENCHDANGER !!SuffocationMRI safety and health issues: Static magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSGradient switchingMAGNETICGRADIËNT COILSBhead [mT]t [ms]PATIENT TABLEYves De DeeneMRI safety and health issues: Static magnetic fields15
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSPatient motion in magnetSUPERCONDUCTINGMAGNETBhead [T]t [s]PATIENT TABLEYves De DeeneMRI safety and health issues: Variable magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulation- - - -Yves De Deene-MRI safety and health issues: Variable magnetic fields16
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulationMaxwell’s equation E ds Bt E- - -d B dAdt A - --vMRI safety and health issues: Variable magnetic fieldsYves De DeeneRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulationLaw of Weiss (1901) – Lapicque (1909)- dBdt - - -TdBdt1rht chrontLimit of perception (ICNIRP)-dBdt20 TsT110.36t [ms]dB/dt d0Yves De Deene0.20.40.60.81.0tS (ms)MRI safety and health issues: Variable magnetic fields17
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulationThreshold levels (current density) (ICNIRP)- - - v -Unclear how the threshold values were determined“. A threshold current density of 10 mA.m -2 at frequencies up to 1 kHz has been estimated for minor effects on nervoussystem functions. Among volunteers, the most consistent effects of exposure are the appearance of phosphenes anda minor reduction in heart rate during or immediately after exposure to ELF fields, but there is no evidence that thesetransient effects are associated with any long-term health risk.”, ICNIRP Guidelines, Health Physics 1998.Yves De DeeneMRI safety and health issues: Variable magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSCardiac stimulationConductivity mapThreshold levelsCurrent density (mA/m2)Nerve stimulationCardiac stimulationPossiblebiologicaleffectCurrent density mapPhosphenesFrequency (Hz)Yves De DeeneMRI safety and health issues: Variable magnetic fields18
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulationTranslation of threshold values to exposure limitsExposure limits(Weiss, Lapicque)Current densityMaxwell’sequation E dsExposure limits?d B dAdt AMagnetic fluxB (µT)106105104103Patient geometry102101Tissue conductivity10010-1110 102 103 104 105 106 107 108 109 1010 1011 1012f (Hz)MRI safety and health issues: Variable magnetic fieldsYves De DeeneRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulationB (µT)Action values (ICNIRP)10610510410310210110010-11Yves De Deene10 102 103 104 105 106 107 108 109 1010 1011 1012Frequency(Hz)MRI safety and health issues: Variable magnetic fields19
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulationB (µT)Action values106 30 µT10533 mT/m10410310230 µT10110010-1f (Hz)110 102 103 104 105 106 107 108 109 101010111012820 Hz65 kHzMRI safety and health issues: Variable magnetic fieldsYves De DeeneRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulationOpen MRIB (µT)Action values10610510410310230 µT10110010-1f (Hz)110 102 103 104 105 106 107 108 109 101010111012820 HzYves De Deene65 kHzMRI safety and health issues: Variable magnetic fields20
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulationInterventional MRIB (µT)Action values106105104B 2000 µT10310230 µT10110010-1f (Hz)110 102 103 104 105 106 107 108 109 101010111012820 HzYves De Deene65 kHzMRI safety and health issues: Variable magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulation1.5 mNursing staffB (T)1mv0.5 mt (s)0.5 T/m00.5 m5 T/m1 T/m3 T/m3 T/m0.3 T/m1mFouriertransformpatient3 T NMR scannerB (T)Action value1mf (Hz)1.5 mYves De DeeneMRI safety and health issues: Variable magnetic fields21
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSNeoronal stimulationCalculation (finite element)J (A/m 2)1.5 mnurse1mv 1 m/s4 T scanner0.5 mJ (A/m2)0.5 T/m5 T/m1 T/m3 T/m03 T/m0.3 T/m1mpatientCrozier S and Liu F 2005, Numerical evaluation of the fields induced by body motion in or near highfield MRI scanners, Progress in Biophysics and Molecular Biology 87, 267-78.Yves De DeeneMRI safety and health issues: Variable magnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYVARIABLE MAGNETIC FIELDSRegulations under discussionCurrent density (mA/m2)Current density (mA/m2)Threshold levelsIEEEOther tissuesIEEE heartIEEE brainFrequency (Hz)Yves De DeeneFrequency (Hz)MRI safety and health issues: Variable magnetic fields22
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYRADIOFREQUENCY ELECTROMAGNETIC FIELDSThermal effects RF waves with f 10 Mhz will deposit heat, distributedby convective heat transfer through blood flow. Body temperature hard to estimate (Bio-heat equation) Body temperature regulation (hypothalamus)But: complications in disease and with medications.- Cardiovascular disease- Barbiturates or phenotiazines depress reflex T regulation.- Anticholinergic drugs suppress sweating and vasodilation. Sensitive organs: eyes, testes, CNSMRI safety and health issues: Radiofrequency electromagnetic fieldsYves De DeeneRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYRADIOFREQUENCY ELECTROMAGNETIC FIELDSSpecific Absorption Rate (SAR)R3 2fP4B1 R Lt P TRLPartial body SAR:SARiTotal body SAR:SARiYves De DeeneLeff ,iLPPiMiPpatM patP headP torso 2.P legM patMRI safety and health issues: Radiofrequency electromagnetic fields23
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYRADIOFREQUENCY ELECTROMAGNETIC FIELDSBioheat equationMetabolismNumerical simulationSARThermalconductionTConvection bybloodflowt k (r ) T (r , t ) 1n dS (r ) c(r )T (r , t ) dVVSB (r ) c B (r )T (r , t ) v B (r , t ) 1n dSSThermal conductionEnvironmentaltemperature Q M (r ) dVVConvection by bloodflow Q EM (r , t ) dVVMetabolismSARDefect of patients thermoregulative systemMRI safety and health issues: Radiofrequency electromagnetic fieldsYves De DeeneRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYRADIOFREQUENCY ELECTROMAGNETIC FIELDSRegulationsSpecific absorption rateFood and Drug Administration (FDA) (July 14, 2003)Physical Agents Directive (European Union)Body partdoseTimespan(min)SAR(W/kg)Body erage60.4Headaverage103Head / torsoper gramtissue610Head / torsoper gramtissue58Limbsper gramtissue620Limbsper gramtissue512Yves De DeeneMRI safety and health issues: Radiofrequency electromagnetic fields24
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYRADIOFREQUENCY ELECTROMAGNETIC FIELDSIndirect effectsRadiofrequencyEM wavec1.fResonant absorption:/2 size object E ds2.Yves De Deeneddt B dAMRI safety and health issues: Radiofrequency electromagnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYPSYCHOLOGICAL EFFECTSAcoustic noisepressureGradient switching,RF hearingClaustrophobia andanxiety relatedcomplicationsYves De Deene Prepare for medical scanning “Quiet” imaging sequences Active/Passive noise reduction Head phones Prepare for medical scanning Sedate children Use of mirrors Open NMR scanner(esp. for children)MRI safety and health issues: Radiofrequency electromagnetic fields25
RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYACOUSTIC NOISE LEVELRegulationsFood and Drug Administration (FDA) (July 14, 2003)rms noise pressure 99 dBA with hearing protection.peak noise level 140 dB67 dB(A) is hazardous threshold for dangerously illpatientsScala of problems with noise:annoyance, difficulties for verbal communication,anxiety, temporary hearing loss, potential permanenthearing problemYves De DeeneMRI safety and health issues: Radiofrequency electromagnetic fieldsRESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGYPSYCHOLOGICAL EFFECTSYves De DeeneMRI safety and health issues: Radiofrequency electromagnetic fields26
MRI safety and health issues prof. Yves De Deene SCANNER BORE PATIENT TABLE CRYOGENIC MAGNET GRADIENT COILS Rx / Tx COIL CACHE OF FARADAY Basic components of an MRI scanner Yves De Deene RESEARCH GROUP QUANTITATIVE MRI IN MEDICINE AND BIOLOGY MRI safety and health issues. 2 50 µT 5 mT 0.3 T -3 T
