MR Pulse Sequences

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MR PulseMR PulseSequencesSequences


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ObjectiveObjective

Physic overviewPhysic overview Basic sequencesBasic sequences Clinical ApplicationClinical Application


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MRIMRI

MRI: Magnetic resonance imagingMRI: Magnetic resonance imaging

Excellent anatomic and pathologicExcellent anatomic and pathologicdetaildetail

Recent technologic advancesRecent technologic advances


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Commom symbols of pulseCommom symbols of pulsesequence diagramssequence diagrams


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MRIMRIThe basis conceptThe basis concept

T1 recoveryT1 recoveryT2 and T2* decayT2 and T2* decay

Repetition time: TRRepetition time: TR Echo time: TEEcho time: TE Contrast weightingContrast weighting


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Physics overview

(Net magnetization vector)


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Magnetization relaxationMagnetization relaxationand decayand decay


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Fat: Shorter T1 (recovers faster)Fat: Shorter T1 (recovers faster)

Shorter T2 (decays faster)Shorter T2 (decays faster) Water (long T1 and T2)Water (long T1 and T2) T2*T2*

- depends on the magnetic enviroment- depends on the magnetic enviroment

(external field)(external field)- Decay of both fat and water occurs very- Decay of both fat and water occurs veryquiklyquikly


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Definitions: TR and TEDefinitions: TR and TE

Two key parametersTwo key parameters

TR(ms) and TE(ms) are key to theTR(ms) and TE(ms) are key to the

creation of image contrastcreation of image contrast

TR: The time between the applicationTR: The time between the applicationof an RF excitation pulse and theof an RF excitation pulse and thestart of the next RF pulsestart of the next RF pulse

TE: the time between the applicationTE: the time between the applicationof RF pulse and the peak of echoof RF pulse and the peak of echodetecteddetected


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MR Signal Localization-MR Signal Localization-GradientsGradients

Gradients are linear variations of theGradients are linear variations of themagnetic field strength in a selectedmagnetic field strength in a selectedregion.region.

Three types of Gradients are appliedThree types of Gradients are applied

- The section-selective gradient:The section-selective gradient:

-

The phase-encoding gradient:The phase-encoding gradient:- The frequency-encoding gradientThe frequency-encoding gradient


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ImagingPlane

Sliceselection

Encoding

Phase Frequency

Coronal Gy Gx GzAxial (bodyimaging)

Gz Gy Gx

Axial (headimaging)

Gz Gx Gy

Sagital Gx Gy Gz


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It can compute the exact location andIt can compute the exact location andamplitude of the signalamplitude of the signal

K- Space and the Image Matrix- >K- Space and the Image Matrix- >

Fourrier: ImageFourrier: Image


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Tissue ContrastTissue Contrast


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DPTR : 2000ms.

TE : 20ms

T2TR : 2000ms. TE : 120ms.

-AT : 4 min. 25 sec.

T1TR : 500ms.

TE :15ms.

AT: 4 min.

Tissue contrastTissue contrast


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Effect of TR and TE on MREffect of TR and TE on MRimaging contrastimaging contrast

Imagingtechnique

TR TE

T1 weighting Short Short

T2 weighting Long Long

Proton-densityweighting

Long Short


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Typical TR and TE valuesTypical TR and TE valuesfor SE and GREfor SE and GRETR (ms) TE (ms)

Sequence Short Long Short Long

SE 250-700>2000 10-20 >60

GRE 100 1-5 >10


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Basis SequencesBasis Sequences

Spin-echoSpin-echo Gradient-echoGradient-echo Inversion-recoveryInversion-recovery Echo-planar imagingEcho-planar imaging

MR angiographicMR angiographic


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SE SequencesSE Sequences


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Tissue contrastTissue contrast

T1: AnatomyT1: AnatomyT1 +Gd: PathologyT1 +Gd: Pathology

T2 : PathologyT2 : Pathology Density proton WI: Both Anatomy andDensity proton WI: Both Anatomy and

PathologyPathology


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Hypersignal on T1Hypersignal on T1

Sub-acute Hematome: (MetHb).Sub-acute Hematome: (MetHb). Fat.Fat.

Artifacts.Artifacts.

Post-hypophyse.Post-hypophyse.

ProteinProtein Melanine (metastase of melanoma).Melanine (metastase of melanoma).

Manganse.Manganse.

calcifications.calcifications.


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The signal intensity ofThe signal intensity ofvarious tissue T1 SEvarious tissue T1 SE

Air, mineral rich tissue (cortical bone, stones), fast

flowing blood

Collagenous tisue (ligament, tendons, scars)

High free water tissue: Kidneys, liver, muscle...

Proteinaceous tissue (abcess, complex

cysts, sylnovial)

Fat, blood products (metHb), slow-flowing blood,

radiation change, contrast agent


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The signal intensity ofThe signal intensity ofvarious tissue on T2 SEvarious tissue on T2 SE

Air, mineral rich tissue, fast-flowing blood

Collagenous tissue, bone islands

Hight bound water tissues (liver, pancreas,adrenals)

Fat, fatty bone marrow

High free water tissue, proteinceous tissue, blood

products


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Advances in MR imaging technology haveAdvances in MR imaging technology have

enabled a reduction in acquisition time withenabled a reduction in acquisition time withthe use of Fast SE sequencesthe use of Fast SE sequences


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Fast SEFast SE

Echo train

N: Echo train length


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SE and Fast SESE and Fast SE

Fast SE: 36s7min 17s


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Sequentially increasing the TE of aSequentially increasing the TE of asequence weights it more heavily towardsequence weights it more heavily toward

T2:T2:

- MR cholangiopancreatography: Bile ductsMR cholangiopancreatography: Bile ductsand Pancreatic ductsand Pancreatic ducts

- MRI: Hemangiomas and CystsMRI: Hemangiomas and Cysts

Fast SEFast SE


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Fast SE: T2W (TE= 650)

Fast SE: T2W (TE= 83)Fast SE: T2W (TE= 180)

Hemangiomas or

Cysts


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SE and Fast SESE and Fast SESequencesSequences


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GRE SequencesGRE Sequences

RF pulse is applied thatRF pulse is applied thatpartly flips the NMVpartly flips the NMVinto the tranverseinto the tranverseplane (variable flipplane (variable flip

angle).angle). Gradients, as opposedGradients, as opposedto RF pulses, are usedto RF pulses, are usedto dephase (negativeto dephase (negativegradient) and rephasegradient) and rephase

(positive gradient)(positive gradient)tranversetranversemagnetizationmagnetization


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GRE SequenceGRE Sequence

Sensitive to magnetic susceptibility differences between tissues.

T2*W: (TR : 800ms; TE : 15 ms), 3 min.


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HemorrhagicHemorrhagic Pigmented villonodular synovitisPigmented villonodular synovitis CalcificationCalcification T2* + Gd: Perfusion studyT2* + Gd: Perfusion study Mapping of human brain function:Mapping of human brain function:

Blood oxygenation level-dependent imaging:Blood oxygenation level-dependent imaging:BOLDBOLD

Deoxyhemoglobin in the vasculatureDeoxyhemoglobin in the vasculature-> Reflection of neuronal activity-> Reflection of neuronal activity



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GRE SequenceGRE SequencePigmented villonodularPigmented villonodular

synovitissynovitis

Coronal PD FSE, fat

suppression

Coronal T2*-weighted GRE:

Blooming artifact Hemosiderin


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GRE SequenceGRE SequencePerfusionPerfusion


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Partially Refocused GRE:Partially Refocused GRE:+ MR angiography+ MR angiography+ Pathology of Internal auditory canal+ Pathology of Internal auditory canal

Fully Refocused GREFully Refocused GRE

- All the gradients are refocused- All the gradients are refocused--> Signal improvement--> Signal improvementSSFP: Steady-state free precession:SSFP: Steady-state free precession:

+ Typical fast+ Typical fast

+ Hight Signal-to-noise ratio+ Hight Signal-to-noise ratio+ Useful for Cardiac imaging, High resolution of IAC :+ Useful for Cardiac imaging, High resolution of IAC :

Spoiled GRE: T1 + GdSpoiled GRE: T1 + Gd


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Oblique sagital T2WSSFP

T1W Spoiled GRE


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CISS: State steady interference constructionCISS: State steady interference construction

- Hight resolution, 3D- Hight resolution, 3D- Acquisition Time: 5min- Acquisition Time: 5min

- Pathology:- Pathology:

+ Cranial nerve: Tumor, neuro-vascular+ Cranial nerve: Tumor, neuro-vascularconflictconflict

+ Meningo-os fistula+ Meningo-os fistula

GRE SequenceGRE SequenceFully Refocused GREFully Refocused GRE

CISS/ FIESTACISS/ FIESTA


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T2 SE

CISS


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CISS TOF 3D

Common names for GRECommon names for GRE


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Common names for GRECommon names for GRESequences Used by MajorSequences Used by Major

VendorsVendors

C ti l I iC ti l I i


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Conventional InversionConventional InversionRecoveryRecovery

TI: The interval between the

180 pulse and the 90 pulse

Fluid is dark

C ti l I iC ti l I i


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Conventional InversionConventional InversionRecoveryRecovery

STIR: Short TI inversion-recoverySTIR: Short TI inversion-recovery FLAIR: Fluid attenuated inversion-FLAIR: Fluid attenuated inversion-

recoveryrecovery TIR (Turbo Inversion Recuperation)

Conventional InversionConventional Inversion


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Conventional InversionConventional InversionRecovery STIRRecovery STIR

Coronal STIRFracture of the distal tibial

Fast SE with spectral fat

suppression

STIR

To null signal from the

Fat : TI 140 msec

TE 140-150 msec

Bone marrow edema


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FLAIRFLAIR

To null signal fromthe Fluid

Technics

TR : 8000 ms.TE : 105 ms.

Acquisition time : 3 min

Lung cancer


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FLAIR SequenceFLAIR Sequence

-Interest: very sensibility-Interest: very sensibility

+ White matter pathology (SEP,+ White matter pathology (SEP,Inflammation, infection, tumor,Inflammation, infection, tumor,vascular).vascular).

+ Epidermoid Kysts.+ Epidermoid Kysts.

- Disadvantage: No specific, artifarctDisadvantage: No specific, artifarctof flow at the posterior fossaof flow at the posterior fossa

TIRTIR (T b(Turbo


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TIRTIR (Turbo(TurboInversionInversionRecuperation)Recuperation)-Advantage: Good-Advantage: Good

contrast white/graycontrast white/graymattermatter

- Application:- Application:

+ Study hippocampe:+ Study hippocampe:(seizure)(seizure)

+ Malformative+ MalformativePathologyPathology (anormal of(anormal ofneuronal migration,neuronal migration,

Gyration, Heterotopies)Gyration, Heterotopies)


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Echo-Planar ImagingEcho-Planar Imaging

A single echo train is used to collectA single echo train is used to collectdata from all lines of k-space duringdata from all lines of k-space duringone TR -> shortents the acquisitionone TR -> shortents the acquisition

timetime 2 types of EPI: SE and GRE2 types of EPI: SE and GRE

sequencessequences

Technique of choice forTechnique of choice for

+ Diffusion-weighted imaging: EPI SE+ Diffusion-weighted imaging: EPI SEsequencesequence

+ Cerebral Perfusion Ma netic


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EPIEPI

EPI GRE


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DWIDWI

To distinguish betweenTo distinguish between+ Rapid diffusion of protons: unrestriction+ Rapid diffusion of protons: unrestriction

Diff.Diff.

+ Slow diffusion of protons: restriction Diff.+ Slow diffusion of protons: restriction Diff.Principle: Either GRE or Fast SE+ Supplement Gradient to dephase:B0, B1000(millitesla/mm2)

+ Gradient to rephase

(equal gradient pulses applied on each side ofthe 180 RF pulse in EPS)

DWDW


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DWDWStrokeStroke

RestrictionHight

signal

intensity


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EPI -DWEPI -DWNo net movement:Rephase (-) Hight signal intensityNet movement: Rephase (+) Signal intensity decrease

Cytotoxique edema, abcess Hyposignal: Fluid, LCR


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DW and ADCDW and ADC

Cart ADC: Apparent diffusionCart ADC: Apparent diffusioncoefficientcoefficient

For the calculation of ADC mapsFor the calculation of ADC maps

2 sets of images2 sets of images

+ One obtained without application of+ One obtained without application ofa Diffusion gradient: T2WI or B0a Diffusion gradient: T2WI or B0

+ One obtained with a diffusion+ One obtained with a diffusiongradientgradient


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Cart ADCCart ADC

Dark and white image : Dark and white image :- ADC decrease dark, viscosite- ADC decrease dark, viscosite

increase:increase:+ Recent infarction+ Recent infarction

+ Abcess+ Abcess+ Recent hematome+ Recent hematome- ADC increase, white, mobile fluid:- ADC increase, white, mobile fluid:

+ LCR+ LCR+ Tumor kysts+ Tumor kysts

Color image:Color image:- ADC decrease = blue- ADC decrease = blue- ADC increase = red- ADC increase = red


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Whats the purpose?Whats the purpose?



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DW and ADCDW and ADCIschemia ?Ischemia ?

DW ADCDW ADC


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DW-ADCDW-ADCIschemiaIschemia

Cytotoxique EdemaCytotoxique EdemaDWI

DW-ADCDW-ADC


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Arachnoide and EpidermoideArachnoide and Epidermoide

Kyst ?Kyst ?

DW-ADC


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DW ADC

Primary Tumors:Glioblastoma ?

DW ADCDW-ADC


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DW-ADCDW-ADCMetastase ?Metastase ?

Metastase: Breast Cancer

DW ADCDW-ADC


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DW-ADCDW-ADCMetastase ?Metastase ?

55 years old, man. Metastase bronchal epidermoid carcinome

DW-ADCDW-ADC


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DW-ADCDW-ADCAbces ?Abces ?

Rana and al. AJNR 2002

Sensibility +++

Specific: +++

DW-ADCDW-ADC


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DW-ADCDW-ADCAbcesAbces

Different Diagnosis:

Metastase: Carcinome epidermoid

Radionecrosis

Hemorrhage in tumor


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MR AngiographyMR Angiography

- Exploration of vessel: No invasive- Exploration of vessel: No invasivetechniquetechnique

- Principle : Creation of contrast- Principle : Creation of contrast

Blood flow: hypersignalBlood flow: hypersignalSuppression of stational tissueSuppression of stational tissue

- 4 Principle sequences:- 4 Principle sequences:

+ TOF: Time Of Flight + TOF: Time Of Flight

+ MOTSA: Multiple onerlapping thin-slab+ MOTSA: Multiple onerlapping thin-slabacquisitionacquisition

+ Contrast-enhanced MRA (Fast GRE 3D+Gd;+ Contrast-enhanced MRA (Fast GRE 3D+Gd;FISP

MRAMRA


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MRAMRATOF and MOTSATOF and MOTSA

Multiple RF pulses applied with shortsMultiple RF pulses applied with shortsTRs saturate the spin in stationaryTRs saturate the spin in stationarytissues:tissues:

Suppression of the signal fromSuppression of the signal fromstationary tissues in the imaging slabstationary tissues in the imaging slab 2D: section-by-section2D: section-by-section

3D: larger volume3D: larger volume MOTSA: Hybrid result of 2D and 3DMOTSA: Hybrid result of 2D and 3D

the Thinner slab -> the Lessthe Thinner slab -> the Lessdeleteriously affected by distaldeleteriously affected by distal


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TOFTOF

GRE: Shorts TR: 40-50msec

Exploration of circulate Flow: Artery or Vein

TOFTOF


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TOFTOF- 2D- 2D ::

- Many Acquisitions by continuous coups (Section-by- Many Acquisitions by continuous coups (Section-bySection)Section)- Favorage:Favorage:+ Slow flow: Veins, before of severe stenosis.+ Slow flow: Veins, before of severe stenosis.+ Exam for large zone+ Exam for large zone

- 3D- 3D ::- Exam the Volume on only timesExam the Volume on only times

The volumes acquisition limited 5-10cm.The volumes acquisition limited 5-10cm.- Precise the anatomy better than 2D.- Precise the anatomy better than 2D.

- Saturate the slow flow.Saturate the slow flow. Exam the arteryExam the arteryReconstruction all of the plan: MIPReconstruction all of the plan: MIPAcquisition time: 7Acquisition time: 7


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Original Coup: TOF


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MIP Reconstructions

Exam the veins (Dural sinus). Interest:

Thrombophlebite

Bilan extension the veins of Meningioma


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Polygone TOFPolygone TOF

Exam the arteries intra-cranial: polygoneExam the arteries intra-cranial: polygoneof Willisof Willis

- Vascular Malformations:Ane., MAV- Vascular Malformations:Ane., MAV- Bilan extension vessel of tumor- Bilan extension vessel of tumor

- Nervo-vascular conflict (Original- Nervo-vascular conflict (Original

coups)coups)

Original Coups


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Original Coups


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MIP Reconstructions

MRAMRA


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Contrast-enhanced MRContrast-enhanced MR

angiographyangiographyT1+ Gd: Shorten the T1 of Blood ->T1+ Gd: Shorten the T1 of Blood ->

Hight signal intensity on T1WIHight signal intensity on T1WI

Fast GRE, 3D (Short AcquisitionFast GRE, 3D (Short Acquisitiontimes:44sec)times:44sec)

Interest: Exploration of cervical vesselsInterest: Exploration of cervical vesselsfrom their origins to cranial base.from their origins to cranial base.

Original Coups


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Original Coups

MIP Reconstructions


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MIP Reconstructions

MRAMRA


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MRAMRA

Contrast

MRAMIP on Contrast

MRA

ARM by Phase of ContrastARM by Phase of Contrast


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ARM by Phase of ContrastARM by Phase of Contrast

- To dephase of mobile protons, using- To dephase of mobile protons, usingtwo inverse pole gradients:two inverse pole gradients:

+ Immobile Protons, dephase and+ Immobile Protons, dephase andrephage: No signalrephage: No signal

+ Mobile Protons+ Mobile Protons: signal: signal

- The different levels of phase depend on- The different levels of phase depend onthe velocity of circulated protonthe velocity of circulated proton

Necessary to select the encode ofNecessary to select the encode of

potential speed to analyze the vesselpotential speed to analyze the vessel

MRA by Phase ofMRA by Phase ofCC t t


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yyContrastContrast

MRAMRA


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MRAMRAPhase-contrast ImagingPhase-contrast Imaging

Providing information about the phaseProviding information about the phase(direction) and the velocity (magnitude) of(direction) and the velocity (magnitude) offlowflow

2D and 3D2D and 3D Hight signal: Flow moves fromHight signal: Flow moves from

RT->LTRT->LT

Sup-> InfSup-> Inf

Ant-> PosAnt-> Pos No signal: Flow moves from:No signal: Flow moves from:


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Phase-contrast

Subclavian steal

Fat-related ImagingFat-related Imaging


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Fat related Imagingg gTechniquesTechniques

Fat Signal Suppression: 3 waysFat Signal Suppression: 3 ways

+ RF- uncoherent gradient: MRI +Gd+ RF- uncoherent gradient: MRI +Gd

+ Inversion-recovery pulse: STIR+ Inversion-recovery pulse: STIR

+ Water-excitation technique:+ Water-excitation technique:Spectral-spatial RF pulseSpectral-spatial RF pulse

Fat-related ImagingFat-related ImagingT h iT h i


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TechniquesTechniques

STIR

Water excitation

fat suppressionT1 fat suppression

Fat-saturated T1WIFat-saturated T1WI


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InterestInterest

- To confirm the fat in the lesion.- To confirm the fat in the lesion.- Bilan lesions extension to the- Bilan lesions extension to the

vessel and the space containingvessel and the space containing

fat:fat:- Arterial dissection- Arterial dissection

Fat saturated T1WIFat saturated T1WI


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Lipome


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Original 3DTOF.

Fat-saturated T1W images.

In-phase and Out-of-PhaseIn-phase and Out-of-Phase


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ppImagingImaging

Different chemical environments of 1H inDifferent chemical environments of 1H infat ( CH2) and water (H2O)fat ( CH2) and water (H2O)

Spoiled GRE: Fat and WaterSpoiled GRE: Fat and Water

In-phase: TE =4,2-4,5 msec (1.5 T)In-phase: TE =4,2-4,5 msec (1.5 T)

Out of phase: TE = 2,1-2,3 msecOut of phase: TE = 2,1-2,3 msec To depict microscopic fat:To depict microscopic fat:

Adrenal adenomas # Adrenal carcinomasAdrenal adenomas # Adrenal carcinomas

SteatosisSteatosisFat + -> null on out of phaseFat + -> null on out of phase

In-phase and Out-of-PhaseIn-phase and Out-of-Phase


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ppImagingImaging

T1 W Spoiled GRE: In-phase:

TE= 4.2

T1 W Spoiled GRE: Out of phase:

TE= 2.1

Adrenal adenoma


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T1

T2 T1 Fat sat


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T1

T2

T1 +Gd


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MR SpectroscopyMR Spectroscopy



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MRS provides a measure of Brain chemistry:MRS provides a measure of Brain chemistry:

1H, 23Na; 31P: (1H higher signal-to-noise)1H, 23Na; 31P: (1H higher signal-to-noise)

Each metabolite appears at a specific ppm, andEach metabolite appears at a specific ppm, andeach one reflects specific cellular and biochemicaleach one reflects specific cellular and biochemicalprocessesprocesses

Biochemical changes in Tumors, Stroke, Epilepsy,Biochemical changes in Tumors, Stroke, Epilepsy,Metabolic disorders, Infections andMetabolic disorders, Infections and

Neurodegenerative diseasesNeurodegenerative diseases Interpretation: MRI and MRSInterpretation: MRI and MRS

(ppm: Parts per millions)


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Observable Proton Metabolites

0.9-1.4 Lipids Products of brain destruction

1.3 Lactate Product of anaerobic glycolysis

2.0 NAA Neuronal marker

2.2-2.4 Glutamine/GABA Neurotransmitters

3.0 Creatine Energy metabolism

3.2 Choline Cell membrane marker

3.5 myo-inositol Glial cell marker, osmolyte

hormone receptor mechanisms

1.2 Ethanol Triplet

1.48 Alanine Present in meningiomas

3.4&3.8 Glucose Increased in diabetes

3.8 Mannitol Rx for increased ICP

ppm Metabolite Properties


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NAA: Decreases with any disease thatNAA: Decreases with any disease thatadversely affects neuronal integ-rityadversely affects neuronal integ-rity

Creatine provides a measure of energyCreatine provides a measure of energy

storesstores Choline: measure of increased cellularCholine: measure of increased cellular

turnoverturnover

Elevate in tumors,Elevate in tumors,

Inflammatory processesInflammatory processes Myoinositol: located primarily in astrocytesMyoinositol: located primarily in astrocytes

Increased in hypernatremia, in tubers andIncreased in hypernatremia, in tubers and

Alzeimer D.Alzeimer D.

Basis physical PrinciplesBasis physical Principles


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Basis physical PrinciplesBasis physical Principles

The resonant frequencies of Protons:The resonant frequencies of Protons:

10MHz at 0.3 T10MHz at 0.3 T

300MHz at 7 T300MHz at 7 T

63-64 MHZ at 1.5 T63-64 MHZ at 1.5 T

Higher field strength, Higher signal-to-Higher field strength, Higher signal-to-noise and better separation of thenoise and better separation of themetabolite peaksmetabolite peaks


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Study the biochemical structure of theStudy the biochemical structure of thedisovle molecule in the waterdisovle molecule in the water

Aanalyze the character of chemicalAanalyze the character of chemicalmovement of the molecules aftermovement of the molecules aftersuppression the signal of water bysuppression the signal of water by

supplemental magnetique fieldsupplemental magnetique field


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Water and Fat is suppressed by:Water and Fat is suppressed by:Technics:Technics:

CHESS (CHEmical-Shift Selective)CHESS (CHEmical-Shift Selective)IR (Inversion Recorvery)IR (Inversion Recorvery)

STEAM or PRESS pulse sequenceSTEAM or PRESS pulse sequence(Stimulated Echo Acquisition Mode): Refocuses(Stimulated Echo Acquisition Mode): Refocuses

9090(Point Resolved SpectroScopy): Refocuses 180(Point Resolved SpectroScopy): Refocuses 180

CSI (Chemical Shift Imaging) refers to multi-voxelCSI (Chemical Shift Imaging) refers to multi-voxelMRSMRS

SI (Spectroscopic Imaging) displays the dataSI (Spectroscopic Imaging) displays the datadepending on the concentration of a particulardepending on the concentration of a particular

metabolitemetabolite

PRESS (pointPRESS (point STEAMSTEAM

( i l d h( ti l t d h


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(p(presolvedresolvedspectroscopy)spectroscopy)

Double spin-echoDouble spin-echotechniquetechnique

Subject to T2 lossSubject to T2 loss

(stimulated echo(stimulated echoacquisitionacquisition

mode):mode): Can use shorterCan use shorter

TE, allow to seeTE, allow to seemore metabolitesmore metabolites

such assuch asmyoinositolmyoinositol

Less SNR thanLess SNR thanPRESSPRESS

SETTING UP MRSETTING UP MR


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SPECTROSCOPYSPECTROSCOPY Choose the right sequenceChoose the right sequence+ Homogeneous lesion: single voxel+ Homogeneous lesion: single voxel

+ Heterogeneous lesion (ring-enhancing,+ Heterogeneous lesion (ring-enhancing,

edema): multivoxeledema): multivoxel Choose the volume (4-8 cmChoose the volume (4-8 cm33)) Avoid skull, sinus, fat, blood products,Avoid skull, sinus, fat, blood products,

vasogenic edema, water, foreign bodies andvasogenic edema, water, foreign bodies andradioactive seedsradioactive seeds


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Short TE of 30msec: Metabolites withShort TE of 30msec: Metabolites withboth short and long T2 relaxationboth short and long T2 relaxationtimes are observed:times are observed:

Long TE of 270 msec, onlyLong TE of 270 msec, onlymetabolites with a long T2 are seen:metabolites with a long T2 are seen:NAA, Creatinin and CholineNAA, Creatinin and Choline

TE of 144 msec: Lactate at 1.3 ppmTE of 144 msec: Lactate at 1.3 ppm

Normal MR Spectrum2
http://www.ajnr.org/content/vol21/issue9/images/large/ajnr-21-09-04-f01.jpeg


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1

WM

1

2

GM

Huntersangle

Hunters Angle:

NAA/Cr, NAA/Cho, and Cho/Cr

Normal Abnormal

NAA/Cr 2.0 < 1.6

NAA/Cho 1.6 < 1.2

Cho/Cr 1.2 > 1.5

MRSMRSBrain Tumors: Degree ofBrain Tumors: Degree of


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Brain Tumors: Degree ofBrain Tumors: Degree ofMalignancyMalignancy

Malignancy increases:Malignancy increases: NAA and Creatine decreaseNAA and Creatine decrease

+ Displaces or destroys neurons+ Displaces or destroys neurons+ Very malignancy: Hight metabolic activity+ Very malignancy: Hight metabolic activity

and deplete the energy stores -> Reduceand deplete the energy stores -> ReduceCreatineCreatine

Choline, Lactate and Lipid increaseCholine, Lactate and Lipid increase+ Very hypercellular tumors with rapid growth+ Very hypercellular tumors with rapid growth

elevate the Cholin levelselevate the Cholin levels+ Lipid: in necrotic portions of tumors+ Lipid: in necrotic portions of tumors+ Lactats appears when tumors out grow their+ Lactats appears when tumors out grow theirblood supply and start ultilizing anaerobicblood supply and start ultilizing anaerobic

glycosisglycosis

MRSMRS


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GliomblastomaGliomblastoma

Elevation of Cho and Decrease NAA

Lactat doublet

Glial tumor or Non-glialGlial tumor or Non-glial


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tumorstumors

Gliomas: Elevation of Cholin beyond the margin ofGliomas: Elevation of Cholin beyond the margin ofenhancementenhancement

High grade astrocytoma # metastasis: the presence ofHigh grade astrocytoma # metastasis: the presence ofhigh choline in the peritumoral region.high choline in the peritumoral region.

Non glial tumors: Have little or no NAANon glial tumors: Have little or no NAA Meningoma: Elevation of Alanine at 1.48ppm:Meningoma: Elevation of Alanine at 1.48ppm: PNET or medulloblastomas have higher elevations ofPNET or medulloblastomas have higher elevations of

Choline than astrocytomaCholine than astrocytoma Lymphomas have higher elevated lipids compared toLymphomas have higher elevated lipids compared to

GBM.GBM. Craniopharyngiomas have a peak in the lactate-lipidCraniopharyngiomas have a peak in the lactate-lipid

range.range.

Tumor recurrence after RadiTumor recurrence after Radi


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or Sur.or Sur.

Elevated cholin is a marker forElevated cholin is a marker forrecurrent tumorrecurrent tumor

Radiation change generally exhibits lowRadiation change generally exhibits low

NAA, Creatine and Cholin onNAA, Creatine and Cholin onSpectroscopySpectroscopy

If radiation necrosis is present, theIf radiation necrosis is present, the

spectrum may reveal elevated lipidsspectrum may reveal elevated lipidsand lactateand lactate

TUMOR VS RADIATIONTUMOR VS RADIATION


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NECROSISNECROSIS Radiation necrosis have high lactateRadiation necrosis have high lactate

and lipids (which may be also foundand lipids (which may be also foundafter radiotherapy)after radiotherapy)

MRSMRSh i d f i


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Ischemia and InfectionIschemia and Infection

IschemiaIschemia

+ Anaerobic glycosis and lactate accumulates -> Hight+ Anaerobic glycosis and lactate accumulates -> HightLactateLactate

+ Infarction: Lipid increase+ Infarction: Lipid increase Brain abcesses destroy or displace brain tissueBrain abcesses destroy or displace brain tissue

+ NAA: not present+ NAA: not present

+ Bacterial abcesses: Lactate, cytosolic acid, alanine+ Bacterial abcesses: Lactate, cytosolic acid, alanine

and Acetateand Acetate+ Toxoplasmosis and Tuberculomas: Prominent peaks+ Toxoplasmosis and Tuberculomas: Prominent peaksfrom Lactate and Lipidsfrom Lactate and Lipids

Infections DiseasesInfections Diseases


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Infections DiseasesInfections Diseases

Brain abcesses destroy or displaceBrain abcesses destroy or displacebrain tissuebrain tissue

NAA: not presentNAA: not present

Bacterial abcesses: Lactate, cytosolicBacterial abcesses: Lactate, cytosolicacid, alanine and Acetateacid, alanine and Acetate

Toxoplasmosis and Tuberculomas:Toxoplasmosis and Tuberculomas:

Prominent peaks from Lactate andProminent peaks from Lactate andLipidsLipids


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How about protocols MRIHow about protocols MRI

for each disease ?for each disease ?


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Thank you for yourThank you for yourattentions!attentions!


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Protocol dIRM dansProtocol dIRM dansl ti h ll ti h l


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exploration encphaleexploration encphale

Standard: T1 sagitalStandard: T1 sagitalT2 axialT2 axial

Flaire axialFlaire axial

Comitialit : T1 sag-T1 Stir CoronalComitialit : T1 sag-T1 Stir Coronal

T2* axialT2* axial

Flaire coronalFlaire coronal+/- T1 axial ou coronal+/- T1 axial ou coronal

avec Gdavec Gd



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Dmence: T1 sag-T1 Stir coronalDmence: T1 sag-T1 Stir coronal(hippo)(hippo)

Flaire axialFlaire axial

T1 axial GdT1 axial Gd Hypophyse: T1 sag et coronalHypophyse: T1 sag et coronal

T1 sag et coronal avecT1 sag et coronal avec

GdGdT2 coronalT2 coronal

ARM post Embolisation: T2 axialARM post Embolisation: T2 axial

TOFTOF



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exploration encphaleexploration encphale Surdit rtrocochlaires, VertigesSurdit rtrocochlaires, Vertiges

T1 sagT1 sagT2 axial coupes fines encphalesT2 axial coupes fines encphalesCISS 3D axialCISS 3D axialT1 axial FS pre et post GdT1 axial FS pre et post Gd

+/-Coro+/-Coro Controle Neurinome de lacoustique non oprControle Neurinome de lacoustique non opr

T1 Gd axial et coro : VolumeT1 Gd axial et coro : VolumeT2 axialT2 axial

Controle Neurinome oprControle Neurinome oprT1 pre et post Gd FST1 pre et post Gd FST2 axialT2 axial



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Orbites: T1 PNOOrbites: T1 PNOT2 PNOT2 PNO

T2 coro StirT2 coro Stir

+/-T1 avec Gd FS+/-T1 avec Gd FS

Conflit Vasculo-nerveuxConflit Vasculo-nerveux

T1 sagT1 sag

T2 axial coupes fines encphalesT2 axial coupes fines encphales

CISS 3D axialCISS 3D axialTOF PolygoneTOF Polygone

ArtifactArtifact


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ArtifactArtifact

Documents

MR Pulse Sequences