INTERNAL MRI COURSE Mgr. Ing. Marek Dostal, Ph.D. - DRNM UHB + Biophys. FacMed. Masaryk Uni. Translation from Czech was done by automatic PowerPoint translator without human control, so the language quality can be poor. Sorry for that. HISTORY OF MRI • 1921 - Discovery of electron spin (A. Compton). • 1924 - Discovery of nuclear spin (W. Pauli). • 1938 - Confirmation of the Magnetic Quantum Phenomenon (NMR) (LI. Rabi). • 1945 - Improvement of the Rabi instrument (birth of NMR spectroscopy) (F. Bloch and E. Purcell). • 1949 - Discovery of chemical shift. • 1971 - Different tissues have different relaxation periods (R. Damadian). • 1973 - the beginnings of tomographic MRI (P. Lauterbur). • 1977 - First full-body MRI (R. Damadian). • 1987 - birth of MR angiography (blood flow imaging). • 1992 - Birth of functional MRI (fMRI). MAGNETIC FIELD MAGNETIC FIELD Magnetic moment (|i) It characterizes the source of the magnetic field. Vector quantity. What does this have to do with MR?_ MAGNETIC FIELD • Electrons "orbit" around the nucleus (analogy with a coil). • Orbital mag. torque (|iL) • Electrons have an internal angular momentum ("rotation around an axis ). • Spin mag. torque (|iS) • Nucleons have an internal angular momentum ("rotation around an axis ). • Nuclear mag. moment MAGNETIZATION MAGNETIZATION As a result of the non-zero temperature (T > 0 K), the particles move completely randomly, and also the orientation of the magnetic moments is completely random. Therefore, the mean value of the magnetization vector is zero (M )=0. Orientation mag. moments in a strong external static mag. Field. Compass needle ^H^^^^^^H MAGNETIZATION E = hf Atom Isotop fL [MHz] v B= IT Vodík 42,7 Uhlík 10,7 Dusík 14|M 6,1 Fosfor 31 p 17,2 MAGNETIZATION N, AE =yhB0 Velikost mag. pole Přebytek spinu na n\Z$\ energetické hladině RELAXATION RELAXATION Typ látk T\ [ms] T2 [ms] tuk 250 sval 900 50 krev 1400 100-200 Mozek šedá hmota (GM) 950 100 bílá hmota ( ;wm) 600 80 cerebrospii tekutina (C aální :sf) 2000 SIGNAL • Signal detection is based on electromagnetic induction: • If the magnetic induction flux changes through the coil, the induced electromotive voltage is induced in it. • When the magnetization changes, the magnetic induction flux changes, and an alternating current of Larmor frequency is induced in the detection coils. • The amplitude of the voltage is proportional to the magnetization and therefore the density of the nuclei. • Free Induction Decay FID is a periodic damped function. __t_ FID = M0 cosO>0£) e T2 4 SIGNAL constant constant MR Signal with Sampled Raw Data Each data point is a I I , I I I ■ ■ ' ■■■■■■■ ■ ■ ■ I ■ I , ■ I i \ns = # of complex samples \\\\\ ..... ■ ■ ■ ■ ■ i ■ i ii i '■■■,<■■■■ —$\ K—Dwell Time (td) = ts/ns K-a Sampling Time (tj FOURIER TRANSFORM A Fourier transform is applied to the signal. What does the Fourier transform do? Converts a signal from the time domain to the frequency domain. uu S(cd) = J s(t) ,-ioit dt — 00 FOURIER TRANSFORM POSITIONAL CODING • But how do we know exactly where we are detecting the signal from? • Because we detect the signal from the entire investigated area at the same time, the spatial information in the FID signal is lost. • We need to include information about the location of the signal source artificially in the signal. • For this we use three gradient coils. • We place these gradient coils so that they produce a variable but time-constant magnetic field in space. • The magnetic induction of this field is significantly smaller than the outer field BO. • The variability (gradient) of these fields is determined exactly for the needs of the experiment (knowledge of the gradient in the x, y, z axes is essential). RF amplitude transmitted RF banówidW Aco frequency ntenor /-axis RF carrier frequency 7-AWS Larmor equation applies here the image slice 1 í t 21.1 MHz Nižší ?1 3 MH? 21.4 MHz Vyssí Všechna jádra uvnitř zvolené tomoroviny precesují se stejnou frekvencí i fází. Gradient Z Gradient Bo + Gradient »MAJOS2011 Aco = y- Gz • Az Gr*dteot v Gradien B0 + Gradient + Gradient Bo + Gradient Gradient x MR Signal with Sampled Raw Data O-"W^V^—■- JL r i Rc-1.028 Im +0.913 PULSE SEQUENCE i Spatial frequency ^/y=kY ,-fr frequency Vx = kx k-space filled line by line 'Cartesian1 daia acquisition SPATIAL RESOLUTION FOV (x*y) Number of frequencies in k-space Number of phases in k-space _ FOVx _ FOVy R0Zx ~ #Mk ] Rozy ~ #/üf 240 240 Rozx = —— = 0,93 mm ; Rozy = —— = 1,25 mm 480 280 RozY = —— = 1,48 ; Rozv = —— = 1,75 mm x 324 y 160 SNR • Voxel size SNR-V SNR (0,93 ; 1,25; 4)~0,93 * 1,25 * 4 = 4,65 SJVi? (0,93 ; 1,25; 3)~0,93 * 1,25 * 3 = 3,48 SNR (0,8 ; 1; 4)~0,8 * 1 * 4 = 3,20 SIGNAL AVERAGING NEX4 SNR~y/NEX ; t~NEX TV _1 _1 SPIN ECHO (SE) TjDiKay d- TE e T2 TE PD TR JEM. e T2 SPIN ECHO Fpin-ipncd inter^k^c (7?;. Spn-mfff hovi fntEra^e fT1) l-1-1-1-1-r 200 j£.u jiju Cas |n\=;] S~PD (l - e ™) TE e nje-72 SPIN CSF GM Tuk TE 8 8 8 TR 600 600 600 Tl 2000 520 180 T2 300 100 90 EXP(-TR/T1) 0,7408 0,315 0,0357 EXP(-TE/T2) 0,9737 0,923 0,9149 1-EXP(-TR/T1) 0,2592 0,685 0,9643 Součin 0,2524 0,632 0,8823 i VI - e TiJ e T2 CSF GM Tuk 120 120 120 6000 6000 6000 2000 520 180 300 100 90 EXP(-TR/T1) EXP(-TE/T2) 0,0498 1E-05 3E-15 0,6703 0,301 0,2636 1-EXP(-TR/T1) 0,9502 Součin 0,6369 0,301 0,2636 S~PD VI - e TiJe n CSF GM Tuk 8 8 8 6000 6000 6000 2000 520 180 300 100 90 EXP(-TR/T1) 0,0498 1E-05 3E-15 EXP(-TE/T2) 0,9737 0,923 0,9149 1-EXP(-TR/T1) 0,9502 0,9252 0,923 0,9149 SPIN ECHO PD CSF GM Tuk TE 120 120 120 TR 600 600 600 TI 2000 520 180 12 300 100 90 EXP(-TR/T1) 0,7408 0,315 0,0357 EXP(-TE/T2) 0,6703 0,301 0,2636 1-EXP(-TR/T1) 0,2592 0,685 0,9643 Součin 0,1737 0,206 0,2542 SPIN ECHO ACQUISITION SPEED Number of averagings Number of rows of k-space t = TR * #phase * NEX t(600ms, 256,1) = 0,6 * 256 * 1 = 153,6s t(4000,256,1) = 4 * 256 * 1 = 1024 s t(500, 512,4) = 0,5 * 512 * 4 = 1024 s TURBO SPIN ECHO ACQUISITION SPEED XR, TF t = TR * #phase * NEX / TF XT ' u * t(600ms,256,l,4) = 0,6 * 256 * 1/4 = 38s Number or averagings v„ \ ' 6 5 t(4000,256,1,18) = 4* 256 * 1 = 56,8s Number of rows of k-space t(5Q(j 512,4,4) = 0, 5 * 512 * 4 = 256 s High SAR uu^^^^h»» water fat n — 1 ^ ^- 0.0 1.1 2.2 3.3 4.4 milliseconds after RF pulse CH SHIFT, J-COUPLING TSE (ETL=15) SE VS TSE - SUSCEPTIBILITY TSE (ETL=5) SE Driven Equilibrium 90° 180° 180° 180° 180° 180° Pulse 90° 180 —iJ, i II # II f II § il FSE Sequence -90e Additional -90° pulse Acceleration of return M shorter TR TR = 4000 1:21 min | TSE DRIVE/FRFSE TSE MULTIVANE/PROPELER Radial scoop of k-space Center resampled Margins undersampled Less sensitive movement Increased blur Creation of artifacts Longer acquisitions >.v; :>. . WW*; TSE MULTIVANE/PROPELER SINGLESHOT TSE High ETL, partial k-space scoop High SAR Decrease in SNR Very fast pick-up (-Is) m These two data points, mirror images across the origin of k-space. have identical amplitudes but opposite phases AT Phase Encode Gradient Steps 90" SPIN-ECHO 90" 180° FAST SPIN-ECHO 180" 3 0" HASTE 90" 180° " li)" n 180° 180" VV ldo* " 180' 90" 90" SINGLESHOT TSE • Reducing SAR > replacing 180° pulses 3D sequence Variable refoc. angle Lower SAR High ETL High resolution Less metal. Artifacts Long acquisition, time (>5min) 40 60 RF pulse Q.6- AS 0.4- 3 H—' n Ü.2 0„ C Iii Iii |- Tl=1000msT2=150m6 - \ /T1=10O0msT2=10ams ■ \ / / T1 =700ms T2=60ms - 20 40 60 echo 80 100 • a < 90° = shorter TR • T2 -> T2* • Sensitive to inhomogeneities • Lower SAR • Quick acquisition • 2 basic families • No/coherent GRE COHERENT GRE (FFE/GRE/FISP) Preserves the transverse component IV Signal T2/T1 weighted Low tissue contrast kg Flowing blood high signal 1 TOF MRA *S A . KOH GRE (12 FFE/FSPGR/PSIF) SE sequence generated by GRE Sequence of a-pulses and grad. TE > TR j Low SNR Quick measurement Extremely sensitive to the movement of spins in the 3r 7" < 1 . /- V KOh "Sum" of FISP (GRE) and PSIF (SE) Unique contrast Use in MSK Cartilage/fluid/bone Dual Echo Steady State (DESS) RF a -A- a Slice -H_r Read J Phase Signal SS-FID SS-Echo * KOH GRE (MENSA/DESS) KOH GRE (FIESTA-C/CISS) Combination of FISP (GRE) and PSIF (SE) SCISS = (S1 + (-l)nS2)/2 Neuro-vascular contact flj*-^" MR cisternography W~ » <^^"/^-f- VVV f F ' -i . V KOH GRE (FIESTA-C/CISS) o KOH GRE (FIESTA/BFFE) • Balanced sequence of all GRETs • Very fast • Less sensitive to turbulence • Extremely sensitive to inhomogeneities BO (-1/TR) • Stronger field = bigger problem • Cardio • Quick display of the abdomen KOH GRE (FIESTA/BFFE) NEKOH GRE (FSPGR/T1FFE) Does not preserve the transverse component M-L Signal Tl or T2* weighted Quick Sequence vazenf , Detection of haemosiderin/calcification ■ Contrast MRA f^^^ T2* significantly shorter than T2 Very sensitive to mag. inhomogeneities Suscept. art. increase in size with a larger TE NEKOH GRE (FSPGR/Tl FFE) NEKOH GRE (FSPGR/T1FFE) a = 10 a = 30 a = 50° [H] and T2* Weighting More T1 Weighting NEKOH GRE (FSPGR/T1FFE) / 1 TR = 20 TR = 50 TR = 100 TR = 400 More T1 Weighting More [H] Weighting NEKOH GRE (FSPGR/Tl FFE) GRE no .1, 60 1 -1-1-1- * ln-P"«se - ■ 1 A"" A NEKOH GRE (IN/OUT PHASE) 1^ 1.1 2.2 3.3 4.4 milliseconds after RF pulse Dependence on BO NEKOH GRE (M-FFE/MERGE) NEKOH GRE (THRIVE/LAVA) TR a \ Spoiler ■-->wyy\/\jy\/vvw... TE Very short TR (-5 ms) and TE (-1 ms) ■ Fast data collection (-15 s) h 061 Generic Gradient Echo GRE GRE FFE GE FE RF-Spoiled GRE FLASH SPGR Tl-FFE RSSG Tl-FFE Coherent GRE with "FID" Refoeusing FISP GRASS FFE SARGE (SG) FE Coherent GRE with "Echo" Refoeusing PSIF SSFP T2-FFE TRSG SSFP Coherent GRE with Balanced "FID/Echo" Refoeusing True FISP FIESTA Balanced FFE BASG True SSFP Coherent Balanced GRE using Dual-excitation CISS FIESTA-C — PBSG — Coherent Double GRE using Combined "FIDs" & "Echoes" DESS MENSA — — — Spoiled GRE using Combined Multiple FIDs MEDIC MERGE M-FFE — — Ultrafast GRE TurboFLASH (2D) MP-RAGE (3D) Fast GRE BRAVO {3D) TFE 3D Tl-TFE RGE (2D) 3D-GEIR Fast FE Spoiled 3D GRE Variants VIBE FAME/LAVA THRIVE TIGRE 3D QUICK GRE Plus SE with Combined Signal TGSE — GRASE — Hybrid EPI MR SAFETY • Strong static and dynamic mag. Field • According to FDA up to 8T for adults without risk • Rapid changes dB/dt = > stimulation of the periphery. Nerves not heart muscle • High-frequency RF pulses • Most E converted to heat (cumulative) • Specific Apsorption Rate (SAR, [W/kg]) • SAR < 4 W/kg = > no temperature increase • SAR < 6 W/kg = > well tolerated • Greater increase in T on the surface • Noise • Small space MR SAFETY • Noise • Grows with BO and gradient velocity • Various noise reduction methods • There may be a problem in psychiatric patients or pregnancy • Small space • Can be suppressed by open magnet design • Closed magnets with larger gantry (70 cm) • Calming down with medication or anesthesia MR SAFETY • Metal implants • Dislocation of ferromagnetic due to BO • Heating of el. conductive thanks to RF and grad. pulses • Ferromagnetic material always absolute contraindications • Non-ferromagnetic = artifacts in the image • Some implants can only be used under certain conditions (BO, grad., SAR...) MR SAFETY - CARDIO STIM • The patient must have a certificate with the stamp and signature of the attending physician that his pacemaker (including electrodes) is MR compatible. • This confirmation must not be older than 3 days. A card about the type of pacemaker is not enough. In case of doubt, it is always necessary to contact the attending physician, it is possible to take an X-ray of the chest, which, however, must be indicated by the attending physician. • The confirmation must include information that the pacemaker is set in MR compatible mode. The advantage is a direct printout from the calibration of the instrument. This confirmation shall not be older than 24 hours. • The confirmation must include a statement from the attending physician that the patient does not have any other implants that would be a contraindication to the MR examination. Especially, for example, left electrodes, etc. • The MR workplace must contain information on the conditions for MR examination in these patients for individual types of stimulators (e.g. the need for centration outside the chest, etc.). • Either the patient brings them with him or they must already be available at the workplace. • When measuring, the patient must be monitored using an ECG. Absolutní kontraindikace LrjQplarľtQyaaŕ Kard.iQMniulátíjr n e b q Ponechané elektrody po deplantaci kardiostimulátoru nebo defibrilátoru Aneuryzmatické cévní svorky (klipy), pokud není písemně doložena jejich M R kompatibilita pumpa atd). pcjkud„nejú pJsjm&djpjGžjnä.MR kcinjfMbJJM Kovová cizí tělesa z jiného než prokazatelně nemagnetického kovu :-intrakraniálně - intraorbitálně Relativní kontraindikace (potenciálně nebezpečné) Stenty (cévní výztuže), žilní filtry, kovový embolizační materiál a okludery méně než 6 týdnů po implantaci, pokud není písemně doložena jejich M R kompatibilita Kloubní náhrady, osteosyntetický materiál a dentální implantáty méně než 6 týdnů po implantaci, pokud není písemně doložena jejich M R kompatibilita Kloubní náhrady a osteosyntetický materiál se známkami uvolňování Bezpečné Stenty {cévní výztuže), žilní filtry, kovový embolizační materiál a okludery 6 a více týdnů po implantaci Kloubní náhrady, osteosyntetický materiál a dentální implantáty 6 a více týdnů po implantaci, bez známek uvolňování (bez ohledu na použitý materiál) Náhrady srdečních chlopní s výjimkou cíleně udané MR nekompatibility Neaneuryzmatické chirurgické cévní svorky (hemostatické klipy) 6 a více týdnů po implantaci Svorky na žlučových cestách 6 a více týdnů po operaci Není kontraindikace Písemné potvrzení výrobce implantátu o jeho plné MR kompatibilitě (kdekoli v těle pacienta) s písemným potvrzením operatéra, který jej implantoval Nitroděložní tělíska (IUD) Stenty (cévní výztuže), žilní filtry, kovový embolizační materiál a okludery, pokud lze písemně doložit plnou M R kompatibilitu (bez ohledu na dobu implantace) SIGNAL SUPPRESSION/AMPLIFICATION • Fat suppression • FatSat • STIR • SPAIR • Water suppression • FLAIR/DIR • Magnetizing transfer • Fat-Water Separation - Dixon • Water excitation SPIR/FATSAT Fat suppression (shift in fat frequency to water, selective RF, gradient pulse reset) ^^^^^^_| Significantly does not extend TR ^^^^^^^Hl^^Hl Does not change the TE ^^^^^^^Ui^^ll Does not affect the application of KL ^^^^^^^■B^^l Very sensitive to field inhomogeneity ^^^^^^^■^B^^ll Better separation in higher mags. Fields ^^^^^^V^B^HI STIR Fat suppression based on Tl time by inverse pulse Not sensitive to field inhomogeneities Can be applied even at lower mags. Fk RF iU DO NOT use with KL " JL Choose longer TR 0° 180° 1180° ISO0 |1S0° 181V TI canceling the fat signal SPAIR/SPECIAL Fat suppression based on spectral selection. IR (inverts only fat) Less sensitive to field inhomogeneities than FatSat, but more sensitive than STIR ^^^^^^^^^^^^^^^^^ More than STIR ^D^^^^^^^^^^^^^^^^^^^^^l DO NOT use with KL H^^^^^B^^^^^^^^S SPAIR/SPECIAL SPAIR WATER SUPPRESSION (FLAIR) IR-based fat suppression Long TI = long TR TI and TR are tied Truncation TR = > TI truncation T2-w image (long TE) Often together with FatSat WATER SUPPRESSION (MAG TR) Bound water = very short T2 = > does not contribute to the signal By saturation of bound water, even free water is saturated Exploitation: Background signal suppression (KL, TOF MRA) Quantification of the free/bound water ratio free water MT RF pulse I fat sat fat bound water 3D TOF + MT TOF MRA MT 3D TOF + MT + FatSat 9 V5 SEPARATION OF WATER AND FAT • IP = V + T . OP = V - T •IP + OP = V + T + V- T = 2V •IP-OP = V + T- V + T = 2T RF 'Pantico G Read out "S f _i fr TE1 TE2 n it \_7 DIXON KVANTIFIKACE Multi-echo Multi-fat peak correction BO correction T2* mapping Fat fraction bvrr Fat-fraction: 2% Liver Fat fraction: 22% WATER EXCITATION • Using multiple RFs excites only H of water • Less sensitive to mag inhomogeneities. fields than FatSat • Models: • (1 1) = 45°45° •(121) = 22.5° 45° 22.5° •(1331) = 10° 30° 30° 10° • Higher model of larger exit •Can change both TE and TR GE Signa 1.5T superconducting scanner Hitachi Aperto 0 4T permanent magnet scanner Hitachi Oasis 1.2T HFO superconducting scanner CONSTRUCTION solenoid C-shaped permanent magnet V7777777777777777T? Dipolar electromagnet design PERMANENT Metal alloys (Fe77Ndl5B8...) BO = 0,1-0,3 T Advantages: Low purchase price Low operating costs Open Disadvantages: Weight (15-70 tons) Field stability very sensitive to temperature Elmag induction BO = 0,1-0,4 T Wk Advantages: Low purchase price Low weight Open and off Disadvantages: High power consumption (~ 50 kW) Field stability very sensitive to temperature • Elmag induction + liquid he cooling • BO = 0,5 - 7 T • Advantages: • Image quality • Stability mag. field • Disadvantages: • Acquisition costs • Can't be turned off 1.5T At a larger BO ^ Growing S/W Growing Tl time Growing SAR (ERF ~ B02!!!) The effect of susceptibility grows Growing noise Rising price Image homogeneity decreases Decreasing T2* time FIELD STRENGTH GRADIENTS • Spatial information ■ • Parameters: • Max. amplitude (20 - 80 mT/m) • Slew rate (80 - 200 mT/m/ms) • Linearity • Amplitude ~ Prost, distinguish • Slew rate ~ TEmin, TRmin... • Minimizing geometric distortion • Maximizing the signal thanks to the ideal Larmor. frequency • Better FatSat, MRS, EPI, fMRI... Unwanted harmonic in field ^.Improved homogeneity Opposite harmonic from shim coil RF COILS Broadcast vs Receiving Full body T/R, worse S/W Surface Closer to the body = > better S/W Dedicated according to ant. areas Multi-segment Multiple coils in one block Coverage of larger areas Enable advanced techniques Greater signal inhomogeneity /VIULII I l\/-\INO/Vll I Conventional Multi Phase Transmit • Larger BO = > shorter waves. Length = > greater signal inhomogeneity Standing wave Non-uniform a. Uniform image RF source 2D EXCITATION • 2D spatially selective RF • Display of small/"rectangular" organs Conventional DWI b 50, 1000,1500, ADC 2.1x2.1x3 mm3 TR/TE 4600 / 79 COS TA3:23 min ZOOMitPRo1 b 50, 1000,1500, ADC 0.95x0.95x3 mm3 TR/TE 4600 / 79 ms TA 3:29 min T2-weighted TSE full-FOV DW-EPI reduced-FOV DW-EP PARALLEL TECHNIQUES SENSE/ASSET Requires calibration 1. Reconstruction, then correction ACQUIRE Coil se 8BI1IB1 UNFOLD/COMBINE Merging of Vi FOV images usi weightings from coil sensitivi maps RECO FOV images from ARC/GRAPPA No need for calibration 1. Correction, then reconstruction acquire Center without deleting columns Partial *-$pace data G with central oversampling Missing lines of k-space and regional coil sensitivities larmonics Individual coil Into final magnitt images image using sum squares so encode ^ Inhomogeneity BO Misaligned machine Metal object Difference of susceptibilit ARTEFACTS ARTEFACTS • Inhomogeneity B1 • Local inaccuracy of the RF pulse angle • Inhomogeneity of the received signal (coil surface) 1 kanalova Multi-kanalova ARTEFACTS Inhomogeneity B1 Dielectric effect Wavelength in body ~ 25cm (3T) Conventional Multi Phase Transmit Non-uniform - Uniform image Standing \ RF source FLAIR 7T ARTEFACTS ARTEFACTS Imperfection of gradients Geometric distortion Movement, flow Poor localization of signal phases ARTEFACTS ARTEFACTS • Motion suppression options • Breath-hold scoop • Pickup synchronized with the breathing curve • Pickup synchronized with diaphragm movement • Pickup synchronized with ECG • Change the data pickup type (Propeller/MultiVane) ARTEFACTS • Flow suppression options • Suitable direction of phase coding NPW = off NPW = off NPW = on ARTEFACTS Flow suppression options Add a gradient pulse 3 RF-pulse and echo Standard readout gradient Readout gradient with extra GMN lobes Net phase gain for moving spins • Flow suppression options • Spatial saturation ARTEFACTS ARTEFACTS Signal line failure Řádek 0 Řádek 10 Řádek 40 ARTEFACTS Failure of multiple signal points (sparking) 15 jisker 5 jisker 35 jisker ARTEFACTS • Chemical shift - increase in BW = decrease in displacement ARTEFACTS Flip Larger FOV Change of FK NPW Phase Encoding- |Mismapped as +270° Mismapped as +90° image with phase wrap-around artifact CONTRAST AGENTS Positive KL Mineral oils Sucrose polyesters Short Tl times protons => positive signal on Tl CONTRAST AGENTS Negative KL Gases (C02, air) Kaolin porridge Dehydrating agents Rectally applied Perflubron CONTRAST AGENTS T2 Silne T2 CONTRAST AGENTS • Paramagnetic KL • The substance itself is not displayed • Significantly changes Tl time in its surroundings (Relaxivity) • Nitrogen dioxide • Stable free radicals • Metal cations (Ni2+, Fe2+, Gd3+) • Relaxivity - concentration, mag.moment, distance, nepar.e- CONTRAST AGENTS • Chelates - coordination links • E.g. Dotarem • CONTRAST AGENTS Contraindication • Termoch Pregnancy —5 & J s*^* Dotareir Breastfeeding ^^£rohanc Kidney disease • Primovi Hypersensitivity to the KL component " Muitihai Contraindication " Magnev • Gadovis Significantly less than iodine ^^tx. Headache, rashes, difficulty breathing Vs^Optimai Allergic reactions Systemic nephrogosis fibrosis It is not recommended to use linear non-ionic KL Termodynamická stabilita - pKŤ] Dotarem 25.6 pohance 23.8 Primovi st 23.5 Multihance 22.6 Magnevist 22.1 Gadovist 21.8 -fJTŕvmscan 16.9 Optimark 16.6 (cyklický, iontový) (cyklický, neiontový^ (lineární, iontový) (lineární, iontový) (lineární, iontový) (cyklický, neiontový) (lineární, neiontovy)"-(lineární, neiontový) nízké riziko vysoké riziko DIFFUSE DISPLAY DWI Diffuse weighing with additional gradients Quality grad. machine equipment ^^^H Max. amplitude (G) 40-80 mT/m Rise speed 80-200 T/m/s ill b=yA2 GA2 5A2 (A-5/3) b = 0 - 1500 s/mm2 clinical b = 0 - 4000 s/mm2 scientific Quick pickup (-100 ms) nam ln (t) =ADC DWI - ADC o0 => D = U S => b = 1000 S => b = 800 S0 => b = 0 S => b > 1500 Restricted diffusion Normal diffusion V) c OJ c c o> (Ž) o E ro O 150 b values (s/mm2) 500 Liver tumor 0 50 150 b values (s/mm2) 500 • Diffusion can be oriented in the same way as diffusion gradients • Min 6 directions grad. • Tensor calculation • Ellipsoid characterization • For a more accurate estimate of > 16 directions DTI FA DTI FA color DTI MD Scalar parameters r Unit of measure Formula Object measured FA MD AD RD Scalar value ranging Fibers directionality/axonal loss Amount of water diffusiori/myelirj loss DifFusivity parallel to the ribers/myelin and axonal content DifFusivity perpendicular to the fibers/myeliii content between 0-1 mm1/sec mm2/sec mm1/sec A, (A, + A,)/2 FA: fractional anisotropyL MD: mean dimisivily; AD: axial dirTusivity; RD: radial difFusivity; mm: millimeters; sec: second. Tractography wholebrairridiffusion tractography average length of streamlines in every voxel / Injury colour denotes reduction in streamline length small injury causes reduction in streamline length along entire tract MRA • Time of flight (TOF) • Principle: • 90° and 180° RF applications • Blood from another layer only 180° RF • Static tissue suppression • The size of the signal is growing: • With speed • With TR, Tl and a • The size of the signal decreases: • Layer thickness • With layer orientation MRA - TOF Influence of flow direction 2D TOF 2D TOF without tracking venous sat with tracking venous sat I 3D TOF single slab MRA - BFFE/FIESTA Selective inverse pulse Incoming blood is univerted Quick acquisition required Breath triscopy/ECG PERIPHERAL MRA Blood in the sys. And dias. Different signal Subtraction EcG tinging Pulsation is essential Phase MRA - PHASE CONTRAST • mpoiar graaient • Motion = phase shift • Phase shift velocity - • Encoding in 3 directions Quantification • Determination of vmax = > "overflow" • Pulsation/turbulence artifacts MRA - CONTRAST • Principle: • When TR << Tl = > low signal • Presence of KL = destruction Tl = higher signal • The more KL, the greater the shortening • Quantity optimization • Application speed optimization • Optimization TE, TR, a • Timely start of measurements • The right choice of data collection • Use of parallel techniques MRA-CE Quick Sequence (3D GRE) Min TE i TR (-1 resp. ~4 ms) Suitable spatial resolution of the given vessel I^^H Suitable measurement volume I^^S Both above will affect accruals fi^^S Optimal a (>Ernst angle) Tl blood 50-150 ms according to KL concentration BE MRA-CE TIMING Bolus Application ~2ml KL Measurement of inflow time Then the rest of the KL and measurements Advantages Precise determination of the beginning of the measi Disadvantages Part of KL not used Longer measurement Background contamination KL MRA-CE TIMING Fluoro trigering/BolusTrak Quick artery scan When KL arrives, the measurement starts Advantages Use of all KL Semi/Automatic Disadvantages A more complex method for RA MRA-CE TIMING Continuous shooting TRICKS/4D-TRAK Sensing on before KL administration Continuous image formation during K Compromise prost. and time, resolutio Advantages: No need to time Possibility to display the optimal phase Advanced data collection = possibility to improve time. Disadvantages: The necessity of compromise time and simplicity, resoli Max. gradients = > greater stimulus, perif. Nerves