Foundations of MRI - McGill University · Outline • Role of MRI in neuroscience! • Crash course...

Foundations of MRI© 1973 Nature Publishing Group

phase of the periodic response at the rota-tion or dilation-contraction frequency, mea-sured with the (complex-valued) Fouriertransform of the response profile over timeat each voxel, is closely related to the polarangle or eccentricity represented at that cor-tical location (13). This technique results inhigh signal-to-noise ratios (because at anyone point in time, approximately one-half ofeach visual field map will be activated) yetprovides fine spatial resolution. Common(for example, retinal) and between-areaphase delays can be removed and examinedby considering clockwise-counterclockwiserotation and expansion-contraction pairs(14, 15).

Figure lA shows a color plot of theresponse to a dilating ring on a medial viewof the cortical surface of the brain of thisparticipant (A.M.D.) (16). The hue of thecolor at each cortical surface point indicatesthe response phase, which is here propor-tional to the eccentricity of the local visualfield representation. In Fig. 1B the corticalsurface was unfolded. This process is similarto inflating a crumpled balloon except thatthe surface has not been stretched. In Fig.iC, the occipital lobe region containing theactivated area has been cut off and theresulting approximately conical surface cutagain along the fundus of the calcarinesulcus to allow it to be flattened completely(17).

There is a systematic increase in eccen-tricity (red to blue to green to yellow to red)moving anteriorly along the medial wall ofthe occipital cortex. Lines of isoeccentricityrun approximately in the coronal plane,cutting across several areas, as shown below.Ventrally, the region showing substantialretinotopy extends almost to the anterior-posterior midpoint of the unfolded ventraltemporal lobe.A parallel treatment of data from the

rotating hemifield stimulus collected a fewminutes later is shown in Fig. 1, D and E.The color again indicates the phase of theperiodic response, which is now proportion-al to the polar angle of the local visual fieldrepresentation. The picture of polar angle ismore complex, alternating between verticaland horizontal meridians both dorsally andventrally. The upper field vertical meridianis red, the horizontal meridian is blue, andthe lower field vertical meridian is green.Several alternations between red and bluestripes are visible ventrally, whereas severalalternations between green and blue stripesare visible dorsally. Mapping experiments inmonkeys suggest that several additional re-representations of the lower visual field ad-join V1 dorsally, including V2 (second vi-sual area) and V3 (third visual area), where-as several rerepresentations of the uppervisual field adjoin V1 ventrally, includingV2, VP (ventroposterior area), and V4v

890

(V4 ventral) (18). In particular, we wouldexpect vertical meridian representations atthe dorsal and ventral V1-V2 border, theventral VP-V4v border, and the dorsal V3-V4 border, and horizontal meridian repre-

sentations near the fundus of the calcarinesulcus in VI, at the dorsal V2-V3 border, atthe ventral V2-VP border, and at the ante-rior border of ventral V4v (4, 6, 7). Can-didates for all of the borders are visible in

Fig. 1. Isoeccentricity and isopolar angle maps of human visual areas. The top row shows isoeccentricitycoded by color [red (fovea) -* blue -> green (parafoveal) -* yellow -> red (periphery)] displayed on theoriginal cortical surface (A), the unfolded cortical surface (B), and the cut and flattened cortical surface (C).The bottom row shows polar angle [red (lower vertical meridian) -> blue (horizontal meridian) -* green(upper vertical meridian)] plotted on the same three surfaces (D), (E), and (F), respectively. Local eccen-tricity and polar angle were determined by considering the phase of the response to a slowly dilating ringor a slowly rotating hemifield at the dilation or rotation frequency. The unfolded representations in (B) and(E) were made by relaxing the curvature while approximately preserving local area and local angles (thesulcal cortex is dark gray and the gyral cortex light gray). The flattened representations in (C) and (F) weremade with the same algorithm after the occipital lobe was cut off and an additional cut in the fundus of thecalcarine sulcus was made.

Fig. 2. Analysis of the data in Fig. 1 byvisual field sign (mirror image versusnon-mirror image visual field represen-tation). Mirror image areas (yellow; forexample, V1), and non-mirror image ar-eas (blue; for example, V2) are shown ina medial view on the folded (A) and un-folded surface (B) and in a ventral view,folded (C) and unfolded (D). The incisionin the fundus of the calcarine is visible in(B). Ventral V1, V2, VP, and V4v (18),comprising four rerepresentations of theupper visual field, are visible below theincision, whereas lower visual field V1and V2 are visible above the incision.The complex folding pattern of the oc-cipital lobe coupled with the weak corre-lation between sulci and areal bound-aries underscores the need for an un-folded representation.

SCIENCE * VOL. 268 * 12 MAY 1995Rick Hoge, Ph.D. McConnell Brain Imaging Centre Montreal Neurological Institute

McGill University

Outline

• Role of MRI in neuroscience

• Crash course on MRI basics

• what is a pulse sequence?

• review of basic pulse sequences and imaging protocols

Structural

T2

PD

T1

DTI

Angiography

Role of MRI in neuroscience

• structure

• cortical anatomy, volumetry

• white matter integrity, vascular burden

• vascular anatomy

• white matter connectivity

Functional

BOLD fMRI

ASL/Perfusion

Spectroscopy

Cardiac

Role of MRI in neuroscience

• function

• localization of processing

• physiological processes (perfusion, metabolism)

• biochemical & molecular information

x-ray

PET

ultrasound

MRI

MRI vs. other modalities

MRI ∼ water imaging

oxygen

hydrogen

hydrogen

Nuclear Magnetization

hydrogen nucleus = proton = “spin”

-

+nuclei aligned

with field

nuclei aligned against field M0

M0 =B0�2�2

4k̄TPD

54°

B0

Different “resonant” nuclei

Nucleus γ [MHz/T]

1H 42.58

13 10.71

19 40.05

31 11.26

Excitation and Relaxation

excite

long delay

BOLDimage

M

*2R

longitudinal magnetization

transverse magnetization

T2*

excite

long delay

BOLDimage

M

*2R

Recovery of longitudinal magnetization

labelprepulse

excite

short delay

perfusionimageM

controlpulse

subtract

What is a pulse sequence?

• a series of radiofrequency (RF) and electromagnetic gradient pulses applied to the body in order to:

• manipulate tissue magnetization to create contrast

• excite tissue magnetization to generate a detectible RF signal

• modulate tissue RF signal to allow generation of cross-sectional images

Exercise: Diffusion Weighting Hands On

B.4$4 IDEA ManualConfidential Draft January 2004

0.0

Figure B.4.1: Sample timing scheme for a diffusion weighted sequence.

GS

GP

GR

ADC

pMrProt->te()[0]

pMrProt->te()[0]/2

lInterDuration

sGSliSel

sGSliSelReph

sGPhasTab

sGPhasTabRew

sSRF01 sSRF02

sGReadDeph

sGBWeightsGBWeight

sGSliSel2

sGradReadout

asGSpoil[Read]sADC01

asGSpoil[Slice]

lInterDuration = Maximum( )'A','B''A' 'B'

lTimeAfterADC

lPERampTime

lAvailableTime = pMrProt->te()[0] - ( sSRF01.getDuration()/2 + sADC01.getDuration()/2 + sGradReadout.getRampUpTime() ) ;

fRTEBFinish()fRTEBInit()

FLASHDiffusion.cpp

Difference between a “sequence” and a “protocol”

• sequence:

• a computer program that generates the specific RF and gradient pulses required to create a particular type of contrast and image geometry

• protocol:

• the set of user parameters that are input to the sequence program

Difference between a “sequence” and a “protocol”

• example of two sequences:

• a T1-weighted anatomic scan (MPRAGE) vs. a T2*-weighted single-shot functional image (EPI)

• example of two protocols:

• a 32-direction DTI scan with 2 mm resolution vs. a 64-direction DTI scan with 3 mm resolution

User control over protocols

User%s Guide Protocol development tools

syngo MR 2004A C.3+37Confidential Draft January 2004

0.0

EXAMPLE:V:/n4/pkg/MrServers/MrImaging/seq/a_ep2d_diff>poetd test.pro /SpuSer /PmuSer

The following window will pop up, if test.pro contains a valid protocol:C.3.

SIEMENS MAGNETOM TrioTim syngo MR B13

\\USER\People\karla\DTI_nogating\mpr_ax111TA: 6:01 PAT: Off Voxel size: 1.0×1.0×1.0 mm Rel. SNR: 1.00 SIEMENS: tfl

PropertiesPrio Recon OffVoice output beforeVoice output afterLoad to viewer OnInline movie OffAuto store images OnLoad to stamp segments OffLoad to graphic segments OffAuto open inline display OffAutoAlign Spine OffStart measurement withoutfurther preparation

On

Wait for user to start OnStart measurements single

RoutineSlab group 1 Slabs 1 Dist. factor 50 % Position R5.5 A13.6 H16.3 Orientation Transversal Phase enc. dir. R >> L Rotation 90.00 degPhase oversampling 0 %Slice oversampling 0 %Slices per slab 192FoV read 192 mmFoV phase 91.7 %Slice thickness 1.00 mmTR 2040 msTE 4.7 msAverages 1Concatenations 1Filter NoneCoil elements HEA;HEP

ContrastMagn. preparation Slice-sel. IRTI 900 msFlip angle 8 degFat suppr. Water excit. normalWater suppr. None

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Averaging mode Long termReconstruction MagnitudeMeasurements 1Multiple series Each measurement

ResolutionBase resolution 192Phase resolution 100 %Slice resolution 75 %Phase partial Fourier OffSlice partial Fourier OffFilter 1 Raw filter OffFilter 2 Distortion Corr. OffFilter 3 Prescan Normalize OffFilter 4 Normalize OffFilter 5 Elliptical filter OffTrajectory Cartesian

Interpolation Off- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

PAT mode NoneMatrix Coil Mode Triple

GeometryMulti-slice mode Single shotSeries Ascending

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

SystemBody OffHEP OnHEA On

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Positioning mode REFTable position HTable position 0 mmMSMA S - C - TSagittal R >> LCoronal A >> PTransversal F >> HSave uncombined OffCoil Combine Mode Adaptive Combine

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Shim mode StandardAdjust with body coil OffConfirm freq. adjustment OffAssume Silicone Off Ref. amplitude 1H 111.000 VAdjustment Tolerance AutoAdjust volume Position R5.5 A13.6 H16.3 Orientation Transversal Rotation 90.00 deg A >> P 192 mm R >> L 176 mm F >> H 192 mm

Physio1st Signal/Mode None

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Dark blood Off- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Resp. control OffInline

Subtract OffStd-Dev-Sag OffStd-Dev-Cor OffStd-Dev-Tra OffStd-Dev-Time OffMIP-Sag OffMIP-Cor OffMIP-Tra OffMIP-Time OffSave original images On

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

SequenceIntroduction OnDimension 3DElliptical scanning OffAsymmetric echo AllowedBandwidth 130 Hz/PxFlow comp. NoEcho spacing 11.2 ms

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

RF pulse type Fast

6/+

Examples of common pulse sequences

• T1, T2, PD-weighted structural scans

• Diffusion-tensor images

• Blood Oxygenation Level-Dependent (BOLD) imaging

• Fluid-Attenuated Inversion Recovery (FLAIR)

Basic MRI contrasts

T1W T2W T2* W EPIPDW

Diffusion-tensor imaging

ADC FAPrincipal

Eigenvector

Diffusion-tensor imaging

BOLD Functional MRI

Fluid-attenuated inversion recovery (FLAIR)

MS lesions, vascular burden

Other pulse sequences

• Magnetization Transfer (MT) imaging

• Arterial spin-labelling (ASL)

• Magnetic resonance angiography (MRA)

• Susceptibility-weighted imaging (SWI)

Magnetization Transfer

Degeneration of corticospinal tract in ALS

Arterial Spin Labelling: MRI of cerebral blood flow

Image slices

Label plane

Functional

BOLD fMRI

ASL/Perfusion

Spectroscopy

Cardiac

CBF in ml/100g/min

ASL Pulse Sequence

labelprepulse

excite

short delay

perfusionimageM

controlpulse

subtract

Functional

BOLD fMRI

ASL/Perfusion

Spectroscopy

Cardiac

X

Magnetic resonance angiography

Susceptibility-weighted imaging

Other advanced MR methods• Parallel imaging

• allows enhancement of SNR or reduction of scan times

• Magnetic Resonance Spectroscopy (MRS)

• proton (1H)

• phosphorus (31P)

• New contrast agents

• super-paramagnetic iron oxide compounds

The “alphabet soup” of Vendor-specific terminology

2

Vendor MRI Acronyms Siemens GE Philips Hitachi Toshiba

Sequence Type

Spin Echo SE SE SE SE SE

Gradient Echo GRE GRE Fast Field Echo (FFE) GE Field Echo

Spoiled Gradient Echo FLASH SPGR T1-FFE RF Spoiled SARGE, RSSG FastFE

Coherent Gradient Echo FISP GRASS FFE Rephased SARGE SSFP

Steady-State Free Precession PSIF SSFP T2-FFE Time-Reversed SARGE

True FISP TrueFISP FIESTA Balanced FFE Balanced SARGE, BASG True SSFP

True FISP/Dual Excitation CISS FIESTA-C – Phase Balanced SARGE, PBSG –

Double Echo Steady State DESS – – – –

Multi-Echo Data Image Combination MEDIC MERGE M-FFE – –

Ultrafast Gradient Echo TurboFLASH Fast GRE, Fast SPGR TFE RGE Fast FE

Ultrafast Gradient Echo 3D MPRAGE 3D FGRE, 3D Fast SPGR 3D TFE MPRAGE 3D Fast FE

Volume Interpolated GRE VIBE LAVA-XV THRIVE TIGRE

Body Diffusion REVEAL DWIBS Body Vision

Susceptibility-Weighted Imaging SWI (SWAN) (Venous BOLD) –

Dynamic MRA with k-space Manipulation TWIST TRICKS-XV Keyhole (4D-TRAK) –

High-Resolution Bilateral Breast Imaging VIEWS VIBRANT-XV BLISS RADIANCE

Non-contrast MR Angio, TSE-based NATIVE-SPACE – TRANCE VASC FSE FBI, CIA

Non-contrast MR Angio, TrueFISP-based NATIVE-TrueFISP Inhance Inflow IR B-TRANCE VASC ASL Time-SLIP

Parametric Mapping MapIT CartiGram – –

Inversion Recovery IR,Turbo IR (TIR) IR, MPIR, FastIR IR-TSE IR IR

Short Tau IR STIR STIR STIR STIR FastSTIR

Long Tau IR Turbo Dark Fluid FLAIR FLAIR FLAIR FastFLAIR

True IR True IR – Real IR – FastIR

Turbo Spin Echo/Fast Spin Echo TSE (Turbo Spin Echo) FSE (Fast Spin Echo) TSE (Turbo Spin Echo) FSE (Fast Spin Echo) FSE (Fast Spin Echo)

Single-Shot TSE/FSE HASTE Single-Shot FSE Single-Shot TSE Single-Shot FSE FASE

FSE/TSE with 90° Flip-Back Pulse RESTORE Fast Recovery FSE (FRFSE) DRIVE Driven Equillibrium FSE T2 Puls FSE

Hyper Echoes Hyperecho – – – –

3D TSE with Variable Flip Angle SPACE CUBE VISTA – –

Number of Echoes Turbo Factor Echo Train Length (ETL) Turbo Factor Shot Factor Echo Train Length (ETL)

Time Between Echoes Echo Spacing Echo Spacing Echo Spacing Interecho Time (ITE) Echo Spacing

Echo Planar Imaging (EPI) EPI EPI EPI EPI EPI

Number of Echoes EPI Factor ETL EPI Factor Shot Factor Echo Train Length (ETL)

Diffusion-Weighted Imaging DWI DWI DWI DWI DWI

Apparent Diffusion Coefficient Map ADC ADC ADC ADC Map ADC

Diffusion Tensor Imaging DTI Diffusion Tensor Imaging Diffusion Tensor Imaging – DTI

DTI Tractography (Fiber Tracking) DTI Tractography FiberTrak FiberTrak – –

Turbo Gradient Spin Echo (GRASE) TurboGSE, TGSE – GRASE – Hybrid EPI

Motion Correction

1D Navigators for Cardiac Imaging 1D PACE Navigators

2D Navigators for Abdominal Imaging 2D PACE – Navigators – –

3D Prospective Motion Correction for fMRI 3D PACE – – – –

3D Retrospective Motion Correction for fMRI 3D ART – –

Motion Correction with Radial Blades BLADE PROPELLER MultiVane RADAR JET

Soft Tissue Motion Correction BRACE

2


Sequence Type






































Motion Correction








Sequence Type






































Motion Correction







3

4

Vendor MRI AcronymsSiemens GE Philips Hitachi Toshiba

Parallel Acquisition Techniques iPAT

PAT: Image-based Algorithm mSENSE ASSET SENSE RAPID SPEEDER

PAT: k-space-based Algorithm GRAPPA ARC – – –

Integrated Calibration Auto-Calibration Self-Calibration (with ARC) – – –

Separate Calibration Turbo-Calibration (Calibration for ASSET) (Calibration for SENSE) / CLEAR (Calibration for RAPID) (Calibration for SPEEDER)

Multiple datasets calibrate each other Self-Calibration, T-PAT – – – –

Spectroscopy

Prostate Spectroscopy 3D CSI PROSE – –

Breast Spectroscopy GRACE BREASE – – –

Comprehensive Cardiac Tool BEAT (2D/3D) – – – –

Patient Orientation Sequence Localizer, Scout Localizer Plan Scan Scanogram Locator

Contrast Bolus Timing/Visualization CARE Bolus Smart Prep; FluoroTriggered MRA BolusTrak FLUTE Visual Prep

Sequence Parameters

Repetition Time, Echo Time (in msec) TR, TE TR, TE TR, TE TR, TE

Inversion Time (in msec) TI TI TI TI TI

Averages Average NEX NSA NSA NSA

Simultaneous Excitation Simultaneous Excitation POMP (Phase Offset Multiplanar) Multi-Slice Dual Slice QuadScan

RF Pulse in Gradient Echo Flip Angle Flip Angle Flip Angle Flip Angle Flip Angle

Scan Measurement Time Acquisition Time, TA Acquisition Time Acquisition Time Scan Time Acquisition Time

Distance Between Slices Distance Factor (% of slice thickness) Gap Gap Slice Interval Gap

Shifting Slices Off Center Off-center Shift Off-center FoV Off-center FoV Off-center FoV Phase & Frequency Shift

Field of View (FoV) FoV [mm] FoV [cm] FoV [mm] FoV FoV

Rectangular FoV FoV Phase/Rectangular FoV Partial FoV (PFoV) Rectangular FoV Rectangular FoV Rectangular FoV

Bandwidth Bandwidth [Hz/Px] Receive Bandwidth [kHz] Fat/Water Shift [pixel] Bandwidth Bandwidth

Variable Bandwidth Optimized bandwidth Variable Bandwidth Optimized Bandwidth Variable Bandwidth Matched Bandwidth

Frequency Oversampling Oversampling Anti-Aliasing Frequency Oversampling Frequency Oversampling Frequency Wrap Suppression

Phase Oversampling Phase Oversampling No Phase Wrap Fold-over Suppression Anti-Wrap Phase Wrap Suppression

Segmented k-Space Lines/Segments Views per segment Views/Segment Segments

Time Delay/Block k-space Time Delay Intersegment Delay TD TD

Half Fourier Imaging Half Fourier 1/2 NEX; fractional NEX Half Scan Half Scan AFI

Partial Echo Asymmetric Echo Partial Echo Partial Echo Half Echo Matched Bandwidth

Gradient Moment Nulling GMR/Flow Comp Flow Comp Flow Comp; Flag GR FC

Ramped RF Pulse TONE Ramped Pulse TONE SSP ISCE

Magnetization Transfer Contrast MTC; MTS MTC MTC MTC SORS-STC

Prep Pulse – Chemically Fat Sat Fat Sat/Chem Sat SPIR Fat Sat MSOFT

Water Excitation Water Excitation – Proset Water Excitation PASTA

Fat-Water separation DIXON IDEAL – FatSep

Prep Pulse - Spatially Presat SAT REST Pre Sat Pre Sat

Moving Sat Pulse Travel Sat; Tracking Sat Walking Sat Travel REST Sequential Pre Sat BFAST

Scan Synchronization with ECG ECG Triggered Cardiac Gated/Triggering ECG Triggered/VCG ECG Triggered Cardiac Gated

Delay after R-Wave Trigger Delay; TD Trigger Delay; TD Trigger Delay; TD Delay Time Trigger Delay; TD

Respiratory Gating Respiratory Gated Respiratory Comp Trigger; PEAR MAR Respiratory Gated

Multi-Channel RF Coil Sensitivity Normalization Prescan Normalize PURE CLEAR NATURAL –

Central k-space Filling Arterial Visualization Elliptical Scanning Elliptic Centric CENTRA PEAKS DRKS

Competition product descriptions, comparison, and specifications contained in this document are based on interpretation of available data at the time this material was being prepared and may require independent verification. Specifications have been obtained from competition brochures, websites, and other independent published sources.

4

Vendor MRI AcronymsSiemens GE Philips Hitachi Toshiba

Parallel Acquisition Techniques iPAT

PAT: Image-based Algorithm mSENSE ASSET SENSE RAPID SPEEDER

PAT: k-space-based Algorithm GRAPPA ARC – – –

Integrated Calibration Auto-Calibration Self-Calibration (with ARC) – – –

Separate Calibration Turbo-Calibration (Calibration for ASSET) (Calibration for SENSE) / CLEAR (Calibration for RAPID) (Calibration for SPEEDER)

Multiple datasets calibrate each other Self-Calibration, T-PAT – – – –

Spectroscopy

Prostate Spectroscopy 3D CSI PROSE – –

Breast Spectroscopy GRACE BREASE – – –

Comprehensive Cardiac Tool BEAT (2D/3D) – – – –

Patient Orientation Sequence Localizer, Scout Localizer Plan Scan Scanogram Locator

Contrast Bolus Timing/Visualization CARE Bolus Smart Prep; FluoroTriggered MRA BolusTrak FLUTE Visual Prep

Sequence Parameters

Repetition Time, Echo Time (in msec) TR, TE TR, TE TR, TE TR, TE

Inversion Time (in msec) TI TI TI TI TI

Averages Average NEX NSA NSA NSA

Simultaneous Excitation Simultaneous Excitation POMP (Phase Offset Multiplanar) Multi-Slice Dual Slice QuadScan

RF Pulse in Gradient Echo Flip Angle Flip Angle Flip Angle Flip Angle Flip Angle

Scan Measurement Time Acquisition Time, TA Acquisition Time Acquisition Time Scan Time Acquisition Time

Distance Between Slices Distance Factor (% of slice thickness) Gap Gap Slice Interval Gap

Shifting Slices Off Center Off-center Shift Off-center FoV Off-center FoV Off-center FoV Phase & Frequency Shift

Field of View (FoV) FoV [mm] FoV [cm] FoV [mm] FoV FoV

Rectangular FoV FoV Phase/Rectangular FoV Partial FoV (PFoV) Rectangular FoV Rectangular FoV Rectangular FoV

Bandwidth Bandwidth [Hz/Px] Receive Bandwidth [kHz] Fat/Water Shift [pixel] Bandwidth Bandwidth

Variable Bandwidth Optimized bandwidth Variable Bandwidth Optimized Bandwidth Variable Bandwidth Matched Bandwidth

Frequency Oversampling Oversampling Anti-Aliasing Frequency Oversampling Frequency Oversampling Frequency Wrap Suppression

Phase Oversampling Phase Oversampling No Phase Wrap Fold-over Suppression Anti-Wrap Phase Wrap Suppression

Segmented k-Space Lines/Segments Views per segment Views/Segment Segments

Time Delay/Block k-space Time Delay Intersegment Delay TD TD

Half Fourier Imaging Half Fourier 1/2 NEX; fractional NEX Half Scan Half Scan AFI

Partial Echo Asymmetric Echo Partial Echo Partial Echo Half Echo Matched Bandwidth

Gradient Moment Nulling GMR/Flow Comp Flow Comp Flow Comp; Flag GR FC

Ramped RF Pulse TONE Ramped Pulse TONE SSP ISCE

Magnetization Transfer Contrast MTC; MTS MTC MTC MTC SORS-STC

Prep Pulse – Chemically Fat Sat Fat Sat/Chem Sat SPIR Fat Sat MSOFT

Water Excitation Water Excitation – Proset Water Excitation PASTA

Fat-Water separation DIXON IDEAL – FatSep

Prep Pulse - Spatially Presat SAT REST Pre Sat Pre Sat

Moving Sat Pulse Travel Sat; Tracking Sat Walking Sat Travel REST Sequential Pre Sat BFAST

Scan Synchronization with ECG ECG Triggered Cardiac Gated/Triggering ECG Triggered/VCG ECG Triggered Cardiac Gated

Delay after R-Wave Trigger Delay; TD Trigger Delay; TD Trigger Delay; TD Delay Time Trigger Delay; TD

Respiratory Gating Respiratory Gated Respiratory Comp Trigger; PEAR MAR Respiratory Gated

Multi-Channel RF Coil Sensitivity Normalization Prescan Normalize PURE CLEAR NATURAL –

Central k-space Filling Arterial Visualization Elliptical Scanning Elliptic Centric CENTRA PEAKS DRKS

Competition product descriptions, comparison, and specifications contained in this document are based on interpretation of available data at the time this material was being prepared and may require independent verification. Specifications have been obtained from competition brochures, websites, and other independent published sources.

Conclusion

• MRI offers a vast array of anatomic and functional contrast mechanisms

• these are made available via an ever expanding array of pulse sequence programs that can be adapted to specific purposes by user edits to the protocol

• these techniques generate image contrast by manipulating nuclear magnetization arising mainly from water

Foundations of MRI - McGill University · Outline • Role of MRI in neuroscience! • Crash course...

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Transcript of Foundations of MRI - McGill University · Outline • Role of MRI in neuroscience! • Crash course...